diff --git a/package.json b/package.json
index f0ba128a91..261cdfa64b 100644
--- a/package.json
+++ b/package.json
@@ -36,7 +36,7 @@
         "istanbul": "latest",
         "mocha-fivemat-progress-reporter": "latest",
         "tslint": "next",
-        "typescript": "1.8.0-dev.20160113",
+        "typescript": "next",
         "tsd": "latest"
     },
     "scripts": {
diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 3127561fea..5eee3c3172 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -137,6 +137,7 @@ namespace ts {
             options = opts;
             inStrictMode = !!file.externalModuleIndicator;
             classifiableNames = {};
+
             Symbol = objectAllocator.getSymbolConstructor();
 
             if (!file.locals) {
@@ -201,8 +202,8 @@ namespace ts {
         // unless it is a well known Symbol.
         function getDeclarationName(node: Declaration): string {
             if (node.name) {
-                if (node.kind === SyntaxKind.ModuleDeclaration && node.name.kind === SyntaxKind.StringLiteral) {
-                    return `"${(<LiteralExpression>node.name).text}"`;
+                if (isAmbientModule(node)) {
+                    return isGlobalScopeAugmentation(<ModuleDeclaration>node) ? "__global" : `"${(<LiteralExpression>node.name).text}"`;
                 }
                 if (node.name.kind === SyntaxKind.ComputedPropertyName) {
                     const nameExpression = (<ComputedPropertyName>node.name).expression;
@@ -358,7 +359,12 @@ namespace ts {
                 //   2. When we checkIdentifier in the checker, we set its resolved symbol to the local symbol,
                 //      but return the export symbol (by calling getExportSymbolOfValueSymbolIfExported). That way
                 //      when the emitter comes back to it, it knows not to qualify the name if it was found in a containing scope.
-                if (hasExportModifier || container.flags & NodeFlags.ExportContext) {
+
+                // NOTE: Nested ambient modules always should go to to 'locals' table to prevent their automatic merge
+                //       during global merging in the checker. Why? The only case when ambient module is permitted inside another module is module augmentation 
+                //       and this case is specially handled. Module augmentations should only be merged with original module definition 
+                //       and should never be merged directly with other augmentation, and the latter case would be possible if automatic merge is allowed.
+                if (!isAmbientModule(node) && (hasExportModifier || container.flags & NodeFlags.ExportContext)) {
                     const exportKind =
                         (symbolFlags & SymbolFlags.Value ? SymbolFlags.ExportValue : 0) |
                         (symbolFlags & SymbolFlags.Type ? SymbolFlags.ExportType : 0) |
@@ -871,7 +877,10 @@ namespace ts {
 
         function bindModuleDeclaration(node: ModuleDeclaration) {
             setExportContextFlag(node);
-            if (node.name.kind === SyntaxKind.StringLiteral) {
+            if (isAmbientModule(node)) {
+                if (node.flags & NodeFlags.Export) {
+                    errorOnFirstToken(node, Diagnostics.export_modifier_cannot_be_applied_to_ambient_modules_and_module_augmentations_since_they_are_always_visible);
+                }
                 declareSymbolAndAddToSymbolTable(node, SymbolFlags.ValueModule, SymbolFlags.ValueModuleExcludes);
             }
             else {
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index a2d1292c51..edc1868401 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -372,6 +372,32 @@ namespace ts {
             }
         }
 
+        function mergeModuleAugmentation(moduleName: LiteralExpression): void {
+            const moduleAugmentation = <ModuleDeclaration>moduleName.parent;
+            if (moduleAugmentation.symbol.valueDeclaration !== moduleAugmentation) {
+                // this is a combined symbol for multiple augmentations within the same file.
+                // its symbol already has accumulated information for all declarations 
+                // so we need to add it just once - do the work only for first declaration 
+                Debug.assert(moduleAugmentation.symbol.declarations.length > 1);
+                return;
+            }
+
+            if (isGlobalScopeAugmentation(moduleAugmentation)) {
+                mergeSymbolTable(globals, moduleAugmentation.symbol.exports);
+            }
+            else {
+                // find a module that about to be augmented 
+                let mainModule = resolveExternalModuleNameWorker(moduleName, moduleName, Diagnostics.Invalid_module_name_in_augmentation_module_0_cannot_be_found);
+                if (!mainModule) {
+                    return;
+                }
+                // if module symbol has already been merged - it is safe to use it.
+                // otherwise clone it
+                mainModule = mainModule.flags & SymbolFlags.Merged ? mainModule : cloneSymbol(mainModule);
+                mergeSymbol(mainModule, moduleAugmentation.symbol);
+            }
+        }
+
         function addToSymbolTable(target: SymbolTable, source: SymbolTable, message: DiagnosticMessage) {
             for (const id in source) {
                 if (hasProperty(source, id)) {
@@ -401,22 +427,10 @@ namespace ts {
             return nodeLinks[nodeId] || (nodeLinks[nodeId] = {});
         }
 
-        function getSourceFile(node: Node): SourceFile {
-            return <SourceFile>getAncestor(node, SyntaxKind.SourceFile);
-        }
-
         function isGlobalSourceFile(node: Node) {
             return node.kind === SyntaxKind.SourceFile && !isExternalOrCommonJsModule(<SourceFile>node);
         }
 
-        /** Is this type one of the apparent types created from the primitive types. */
-        function isPrimitiveApparentType(type: Type): boolean {
-            return type === globalStringType ||
-                type === globalNumberType ||
-                type === globalBooleanType ||
-                type === globalESSymbolType;
-        }
-
         function getSymbol(symbols: SymbolTable, name: string, meaning: SymbolFlags): Symbol {
             if (meaning && hasProperty(symbols, name)) {
                 const symbol = symbols[name];
@@ -579,8 +593,7 @@ namespace ts {
                         if (!isExternalOrCommonJsModule(<SourceFile>location)) break;
                     case SyntaxKind.ModuleDeclaration:
                         const moduleExports = getSymbolOfNode(location).exports;
-                        if (location.kind === SyntaxKind.SourceFile ||
-                            (location.kind === SyntaxKind.ModuleDeclaration && (<ModuleDeclaration>location).name.kind === SyntaxKind.StringLiteral)) {
+                        if (location.kind === SyntaxKind.SourceFile || isAmbientModule(location)) {
 
                             // It's an external module. First see if the module has an export default and if the local
                             // name of that export default matches.
@@ -736,7 +749,9 @@ namespace ts {
 
             if (!result) {
                 if (nameNotFoundMessage) {
-                    error(errorLocation, nameNotFoundMessage, typeof nameArg === "string" ? nameArg : declarationNameToString(nameArg));
+                    if (!checkAndReportErrorForMissingPrefix(errorLocation, name, nameArg)) {
+                        error(errorLocation, nameNotFoundMessage, typeof nameArg === "string" ? nameArg : declarationNameToString(nameArg));
+                    }
                 }
                 return undefined;
             }
@@ -773,6 +788,43 @@ namespace ts {
             return result;
         }
 
+        function checkAndReportErrorForMissingPrefix(errorLocation: Node, name: string, nameArg: string | Identifier): boolean {
+            if (!errorLocation || (errorLocation.kind === SyntaxKind.Identifier && (isTypeReferenceIdentifier(<Identifier>errorLocation)) || isInTypeQuery(errorLocation))) {
+                return false;
+            }
+
+            const container = getThisContainer(errorLocation, /* includeArrowFunctions */ true);
+            let location = container;
+            while (location) {
+                if (isClassLike(location.parent)) {
+                    const classSymbol = getSymbolOfNode(location.parent);
+                    if (!classSymbol) {
+                        break;
+                    }
+
+                    // Check to see if a static member exists.
+                    const constructorType = getTypeOfSymbol(classSymbol);
+                    if (getPropertyOfType(constructorType, name)) {
+                        error(errorLocation, Diagnostics.Cannot_find_name_0_Did_you_mean_the_static_member_1_0, typeof nameArg === "string" ? nameArg : declarationNameToString(nameArg), symbolToString(classSymbol));
+                        return true;
+                    }
+
+                    // No static member is present.
+                    // Check if we're in an instance method and look for a relevant instance member. 
+                    if (location === container && !(location.flags & NodeFlags.Static)) {
+                        const instanceType = (<InterfaceType>getDeclaredTypeOfSymbol(classSymbol)).thisType;
+                        if (getPropertyOfType(instanceType, name)) {
+                            error(errorLocation, Diagnostics.Cannot_find_name_0_Did_you_mean_the_instance_member_this_0, typeof nameArg === "string" ? nameArg : declarationNameToString(nameArg));
+                            return true;
+                        }
+                    }
+                }
+
+                location = location.parent;
+            }
+            return false;
+        }
+
         function checkResolvedBlockScopedVariable(result: Symbol, errorLocation: Node): void {
             Debug.assert((result.flags & SymbolFlags.BlockScopedVariable) !== 0);
             // Block-scoped variables cannot be used before their definition
@@ -1074,6 +1126,10 @@ namespace ts {
         }
 
         function resolveExternalModuleName(location: Node, moduleReferenceExpression: Expression): Symbol {
+            return resolveExternalModuleNameWorker(location, moduleReferenceExpression, Diagnostics.Cannot_find_module_0);
+        }
+
+        function resolveExternalModuleNameWorker(location: Node, moduleReferenceExpression: Expression, moduleNotFoundError: DiagnosticMessage): Symbol {
             if (moduleReferenceExpression.kind !== SyntaxKind.StringLiteral) {
                 return;
             }
@@ -1092,20 +1148,29 @@ namespace ts {
             if (!isRelative) {
                 const symbol = getSymbol(globals, "\"" + moduleName + "\"", SymbolFlags.ValueModule);
                 if (symbol) {
-                    return symbol;
+                    // merged symbol is module declaration symbol combined with all augmentations
+                    return getMergedSymbol(symbol);
                 }
             }
 
-            const resolvedModule = getResolvedModule(getSourceFile(location), moduleReferenceLiteral.text);
+            const resolvedModule = getResolvedModule(getSourceFileOfNode(location), moduleReferenceLiteral.text);
             const sourceFile = resolvedModule && host.getSourceFile(resolvedModule.resolvedFileName);
             if (sourceFile) {
                 if (sourceFile.symbol) {
-                    return sourceFile.symbol;
+                    // merged symbol is module declaration symbol combined with all augmentations
+                    return getMergedSymbol(sourceFile.symbol);
                 }
-                error(moduleReferenceLiteral, Diagnostics.File_0_is_not_a_module, sourceFile.fileName);
-                return;
+                if (moduleNotFoundError) {
+                    // report errors only if it was requested 
+                    error(moduleReferenceLiteral, Diagnostics.File_0_is_not_a_module, sourceFile.fileName);
+                }
+                return undefined;
             }
-            error(moduleReferenceLiteral, Diagnostics.Cannot_find_module_0, moduleName);
+            if (moduleNotFoundError) {
+                // report errors only if it was requested
+                error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+            }
+            return undefined;
         }
 
         // An external module with an 'export =' declaration resolves to the target of the 'export =' declaration,
@@ -1522,8 +1587,7 @@ namespace ts {
         }
 
         function hasExternalModuleSymbol(declaration: Node) {
-            return (declaration.kind === SyntaxKind.ModuleDeclaration && (<ModuleDeclaration>declaration).name.kind === SyntaxKind.StringLiteral) ||
-                (declaration.kind === SyntaxKind.SourceFile && isExternalOrCommonJsModule(<SourceFile>declaration));
+            return isAmbientModule(declaration) || (declaration.kind === SyntaxKind.SourceFile && isExternalOrCommonJsModule(<SourceFile>declaration));
         }
 
         function hasVisibleDeclarations(symbol: Symbol): SymbolVisibilityResult {
@@ -1647,6 +1711,12 @@ namespace ts {
             return undefined;
         }
 
+        function isTopLevelInExternalModuleAugmentation(node: Node): boolean {
+            return node && node.parent &&
+                node.parent.kind === SyntaxKind.ModuleBlock &&
+                isExternalModuleAugmentation(node.parent.parent);
+        }
+
         function getSymbolDisplayBuilder(): SymbolDisplayBuilder {
 
             function getNameOfSymbol(symbol: Symbol): string {
@@ -2229,6 +2299,10 @@ namespace ts {
                     case SyntaxKind.FunctionDeclaration:
                     case SyntaxKind.EnumDeclaration:
                     case SyntaxKind.ImportEqualsDeclaration:
+                        // external module augmentation is always visible
+                        if (isExternalModuleAugmentation(node)) {
+                            return true;
+                        }
                         const parent = getDeclarationContainer(node);
                         // If the node is not exported or it is not ambient module element (except import declaration)
                         if (!(getCombinedNodeFlags(node) & NodeFlags.Export) &&
@@ -2321,7 +2395,9 @@ namespace ts {
                         const firstIdentifier = getFirstIdentifier(internalModuleReference);
                         const importSymbol = resolveName(declaration, firstIdentifier.text, SymbolFlags.Value | SymbolFlags.Type | SymbolFlags.Namespace,
                             Diagnostics.Cannot_find_name_0, firstIdentifier);
-                        buildVisibleNodeList(importSymbol.declarations);
+                        if (importSymbol) {
+                            buildVisibleNodeList(importSymbol.declarations);
+                        }
                     }
                 });
             }
@@ -2406,7 +2482,7 @@ namespace ts {
             // Every class automatically contains a static property member named 'prototype',
             // the type of which is an instantiation of the class type with type Any supplied as a type argument for each type parameter.
             // It is an error to explicitly declare a static property member with the name 'prototype'.
-            const classType = <InterfaceType>getDeclaredTypeOfSymbol(prototype.parent);
+            const classType = <InterfaceType>getDeclaredTypeOfSymbol(getMergedSymbol(prototype.parent));
             return classType.typeParameters ? createTypeReference(<GenericType>classType, map(classType.typeParameters, _ => anyType)) : classType;
         }
 
@@ -4900,6 +4976,10 @@ namespace ts {
             return checkTypeRelatedTo(source, target, identityRelation, /*errorNode*/ undefined) ? Ternary.True : Ternary.False;
         }
 
+        function compareTypesAssignable(source: Type, target: Type): Ternary {
+            return checkTypeRelatedTo(source, target, assignableRelation, /*errorNode*/ undefined) ? Ternary.True : Ternary.False;
+        }
+
         function isTypeSubtypeOf(source: Type, target: Type): boolean {
             return checkTypeSubtypeOf(source, target, /*errorNode*/ undefined);
         }
@@ -4916,16 +4996,27 @@ namespace ts {
             return checkTypeRelatedTo(source, target, assignableRelation, errorNode, headMessage, containingMessageChain);
         }
 
+        function isSignatureAssignableTo(source: Signature,
+                                         target: Signature,
+                                         ignoreReturnTypes: boolean): boolean {
+            return compareSignaturesRelated(source, target, ignoreReturnTypes, /*reportErrors*/ false, /*errorReporter*/ undefined, compareTypesAssignable) !== Ternary.False;
+        }
+
         /**
          * See signatureRelatedTo, compareSignaturesIdentical
          */
-        function isSignatureAssignableTo(source: Signature, target: Signature, ignoreReturnTypes: boolean): boolean {
+        function compareSignaturesRelated(source: Signature,
+                                          target: Signature,
+                                          ignoreReturnTypes: boolean,
+                                          reportErrors: boolean,
+                                          errorReporter: (d: DiagnosticMessage, arg0?: string, arg1?: string) => void,
+                                          compareTypes: (s: Type, t: Type, reportErrors?: boolean) => Ternary): Ternary {
             // TODO (drosen): De-duplicate code between related functions.
             if (source === target) {
-                return true;
+                return Ternary.True;
             }
             if (!target.hasRestParameter && source.minArgumentCount > target.parameters.length) {
-                return false;
+                return Ternary.False;
             }
 
             // Spec 1.0 Section 3.8.3 & 3.8.4:
@@ -4933,36 +5024,49 @@ namespace ts {
             source = getErasedSignature(source);
             target = getErasedSignature(target);
 
+            let result = Ternary.True;
+
             const sourceMax = getNumNonRestParameters(source);
             const targetMax = getNumNonRestParameters(target);
             const checkCount = getNumParametersToCheckForSignatureRelatability(source, sourceMax, target, targetMax);
+            const sourceParams = source.parameters;
+            const targetParams = target.parameters;
             for (let i = 0; i < checkCount; i++) {
-                const s = i < sourceMax ? getTypeOfSymbol(source.parameters[i]) : getRestTypeOfSignature(source);
-                const t = i < targetMax ? getTypeOfSymbol(target.parameters[i]) : getRestTypeOfSignature(target);
-                const related = isTypeAssignableTo(t, s) || isTypeAssignableTo(s, t);
+                const s = i < sourceMax ? getTypeOfSymbol(sourceParams[i]) : getRestTypeOfSignature(source);
+                const t = i < targetMax ? getTypeOfSymbol(targetParams[i]) : getRestTypeOfSignature(target);
+                const related = compareTypes(t, s, /*reportErrors*/ false) || compareTypes(s, t, reportErrors);
                 if (!related) {
-                    return false;
+                    if (reportErrors) {
+                        errorReporter(Diagnostics.Types_of_parameters_0_and_1_are_incompatible,
+                            sourceParams[i < sourceMax ? i : sourceMax].name,
+                            targetParams[i < targetMax ? i : targetMax].name);
+                    }
+                    return Ternary.False;
                 }
+                result &= related;
             }
 
             if (!ignoreReturnTypes) {
                 const targetReturnType = getReturnTypeOfSignature(target);
                 if (targetReturnType === voidType) {
-                    return true;
+                    return result;
                 }
                 const sourceReturnType = getReturnTypeOfSignature(source);
 
                 // The following block preserves behavior forbidding boolean returning functions from being assignable to type guard returning functions
                 if (targetReturnType.flags & TypeFlags.PredicateType && (targetReturnType as PredicateType).predicate.kind === TypePredicateKind.Identifier) {
                     if (!(sourceReturnType.flags & TypeFlags.PredicateType)) {
-                        return false;
+                        if (reportErrors) {
+                            errorReporter(Diagnostics.Signature_0_must_have_a_type_predicate, signatureToString(source));
+                        }
+                        return Ternary.False;
                     }
                 }
 
-                return isTypeAssignableTo(sourceReturnType, targetReturnType);
+                result &= compareTypes(sourceReturnType, targetReturnType, reportErrors);
             }
 
-            return true;
+            return result;
         }
 
         function isImplementationCompatibleWithOverload(implementation: Signature, overload: Signature): boolean {
@@ -5033,24 +5137,14 @@ namespace ts {
             let expandingFlags: number;
             let depth = 0;
             let overflow = false;
-            let elaborateErrors = false;
 
             Debug.assert(relation !== identityRelation || !errorNode, "no error reporting in identity checking");
 
-            const result = isRelatedTo(source, target, errorNode !== undefined, headMessage);
+            const result = isRelatedTo(source, target, /*reportErrors*/ !!errorNode, headMessage);
             if (overflow) {
                 error(errorNode, Diagnostics.Excessive_stack_depth_comparing_types_0_and_1, typeToString(source), typeToString(target));
             }
             else if (errorInfo) {
-                // If we already computed this relation, but in a context where we didn't want to report errors (e.g. overload resolution),
-                // then we'll only have a top-level error (e.g. 'Class X does not implement interface Y') without any details. If this happened,
-                // request a recompuation to get a complete error message. This will be skipped if we've already done this computation in a context
-                // where errors were being reported.
-                if (errorInfo.next === undefined) {
-                    errorInfo = undefined;
-                    elaborateErrors = true;
-                    isRelatedTo(source, target, errorNode !== undefined, headMessage);
-                }
                 if (containingMessageChain) {
                     errorInfo = concatenateDiagnosticMessageChains(containingMessageChain, errorInfo);
                 }
@@ -5060,6 +5154,7 @@ namespace ts {
             return result !== Ternary.False;
 
             function reportError(message: DiagnosticMessage, arg0?: string, arg1?: string, arg2?: string): void {
+                Debug.assert(!!errorNode);
                 errorInfo = chainDiagnosticMessages(errorInfo, message, arg0, arg1, arg2);
             }
 
@@ -5197,14 +5292,14 @@ namespace ts {
                     }
                     // Even if relationship doesn't hold for unions, intersections, or generic type references,
                     // it may hold in a structural comparison.
-                    const apparentType = getApparentType(source);
+                    const apparentSource = getApparentType(source);
                     // In a check of the form X = A & B, we will have previously checked if A relates to X or B relates
                     // to X. Failing both of those we want to check if the aggregation of A and B's members structurally
                     // relates to X. Thus, we include intersection types on the source side here.
-                    if (apparentType.flags & (TypeFlags.ObjectType | TypeFlags.Intersection) && target.flags & TypeFlags.ObjectType) {
+                    if (apparentSource.flags & (TypeFlags.ObjectType | TypeFlags.Intersection) && target.flags & TypeFlags.ObjectType) {
                         // Report structural errors only if we haven't reported any errors yet
-                        const reportStructuralErrors = reportErrors && errorInfo === saveErrorInfo;
-                        if (result = objectTypeRelatedTo(apparentType, source, target, reportStructuralErrors)) {
+                        const reportStructuralErrors = reportErrors && errorInfo === saveErrorInfo && !(source.flags & TypeFlags.Primitive);
+                        if (result = objectTypeRelatedTo(apparentSource, source, target, reportStructuralErrors)) {
                             errorInfo = saveErrorInfo;
                             return result;
                         }
@@ -5269,6 +5364,7 @@ namespace ts {
                                 // We know *exactly* where things went wrong when comparing the types.
                                 // Use this property as the error node as this will be more helpful in
                                 // reasoning about what went wrong.
+                                Debug.assert(!!errorNode);
                                 errorNode = prop.valueDeclaration;
                                 reportError(Diagnostics.Object_literal_may_only_specify_known_properties_and_0_does_not_exist_in_type_1,
                                     symbolToString(prop), typeToString(target));
@@ -5371,7 +5467,7 @@ namespace ts {
                 const id = relation !== identityRelation || source.id < target.id ? source.id + "," + target.id : target.id + "," + source.id;
                 const related = relation[id];
                 if (related !== undefined) {
-                    if (elaborateErrors && related === RelationComparisonResult.Failed) {
+                    if (reportErrors && related === RelationComparisonResult.Failed) {
                         // We are elaborating errors and the cached result is an unreported failure. Record the result as a reported
                         // failure and continue computing the relation such that errors get reported.
                         relation[id] = RelationComparisonResult.FailedAndReported;
@@ -5591,7 +5687,7 @@ namespace ts {
                         }
                         // don't elaborate the primitive apparent types (like Number)
                         // because the actual primitives will have already been reported.
-                        if (shouldElaborateErrors && !isPrimitiveApparentType(source)) {
+                        if (shouldElaborateErrors) {
                             reportError(Diagnostics.Type_0_provides_no_match_for_the_signature_1,
                                 typeToString(source),
                                 signatureToString(t, /*enclosingDeclaration*/ undefined, /*flags*/ undefined, kind));
@@ -5603,77 +5699,10 @@ namespace ts {
             }
 
             /**
-             * See signatureAssignableTo, signatureAssignableTo
+             * See signatureAssignableTo, compareSignaturesIdentical
              */
             function signatureRelatedTo(source: Signature, target: Signature, reportErrors: boolean): Ternary {
-                // TODO (drosen): De-duplicate code between related functions.
-                if (source === target) {
-                    return Ternary.True;
-                }
-                if (!target.hasRestParameter && source.minArgumentCount > target.parameters.length) {
-                    return Ternary.False;
-                }
-                let sourceMax = source.parameters.length;
-                let targetMax = target.parameters.length;
-                let checkCount: number;
-                if (source.hasRestParameter && target.hasRestParameter) {
-                    checkCount = sourceMax > targetMax ? sourceMax : targetMax;
-                    sourceMax--;
-                    targetMax--;
-                }
-                else if (source.hasRestParameter) {
-                    sourceMax--;
-                    checkCount = targetMax;
-                }
-                else if (target.hasRestParameter) {
-                    targetMax--;
-                    checkCount = sourceMax;
-                }
-                else {
-                    checkCount = sourceMax < targetMax ? sourceMax : targetMax;
-                }
-                // Spec 1.0 Section 3.8.3 & 3.8.4:
-                // M and N (the signatures) are instantiated using type Any as the type argument for all type parameters declared by M and N
-                source = getErasedSignature(source);
-                target = getErasedSignature(target);
-                let result = Ternary.True;
-                for (let i = 0; i < checkCount; i++) {
-                    const s = i < sourceMax ? getTypeOfSymbol(source.parameters[i]) : getRestTypeOfSignature(source);
-                    const t = i < targetMax ? getTypeOfSymbol(target.parameters[i]) : getRestTypeOfSignature(target);
-                    const saveErrorInfo = errorInfo;
-                    let related = isRelatedTo(s, t, reportErrors);
-                    if (!related) {
-                        related = isRelatedTo(t, s, /*reportErrors*/ false);
-                        if (!related) {
-                            if (reportErrors) {
-                                reportError(Diagnostics.Types_of_parameters_0_and_1_are_incompatible,
-                                    source.parameters[i < sourceMax ? i : sourceMax].name,
-                                    target.parameters[i < targetMax ? i : targetMax].name);
-                            }
-                            return Ternary.False;
-                        }
-                        errorInfo = saveErrorInfo;
-                    }
-                    result &= related;
-                }
-
-                const targetReturnType = getReturnTypeOfSignature(target);
-                if (targetReturnType === voidType) {
-                    return result;
-                }
-                const sourceReturnType = getReturnTypeOfSignature(source);
-
-                // The following block preserves behavior forbidding boolean returning functions from being assignable to type guard returning functions
-                if (targetReturnType.flags & TypeFlags.PredicateType && (targetReturnType as PredicateType).predicate.kind === TypePredicateKind.Identifier) {
-                    if (!(sourceReturnType.flags & TypeFlags.PredicateType)) {
-                        if (reportErrors) {
-                            reportError(Diagnostics.Signature_0_must_have_a_type_predicate, signatureToString(source));
-                        }
-                        return Ternary.False;
-                    }
-                }
-
-                return result & isRelatedTo(sourceReturnType, targetReturnType, reportErrors);
+                return compareSignaturesRelated(source, target, /*ignoreReturnTypes*/ false, reportErrors, reportError, isRelatedTo);
             }
 
             function signaturesIdenticalTo(source: Type, target: Type, kind: SignatureKind): Ternary {
@@ -6681,10 +6710,6 @@ namespace ts {
                 if (typeInfo && typeInfo.type === undefinedType) {
                     return type;
                 }
-                // If the type to be narrowed is any and we're checking a primitive with assumeTrue=true, return the primitive
-                if (!!(type.flags & TypeFlags.Any) && typeInfo && assumeTrue) {
-                    return typeInfo.type;
-                }
                 let flags: TypeFlags;
                 if (typeInfo) {
                     flags = typeInfo.flags;
@@ -6695,6 +6720,10 @@ namespace ts {
                 }
                 // At this point we can bail if it's not a union
                 if (!(type.flags & TypeFlags.Union)) {
+                    // If we're on the true branch and the type is a subtype, we should return the primitive type
+                    if (assumeTrue && typeInfo && isTypeSubtypeOf(typeInfo.type, type)) {
+                        return typeInfo.type;
+                    }
                     // If the active non-union type would be removed from a union by this type guard, return an empty union
                     return filterUnion(type) ? type : emptyUnionType;
                 }
@@ -8619,7 +8648,7 @@ namespace ts {
         function checkIndexedAccess(node: ElementAccessExpression): Type {
             // Grammar checking
             if (!node.argumentExpression) {
-                const sourceFile = getSourceFile(node);
+                const sourceFile = getSourceFileOfNode(node);
                 if (node.parent.kind === SyntaxKind.NewExpression && (<NewExpression>node.parent).expression === node) {
                     const start = skipTrivia(sourceFile.text, node.expression.end);
                     const end = node.end;
@@ -11990,7 +12019,7 @@ namespace ts {
                     case SyntaxKind.InterfaceDeclaration:
                         return SymbolFlags.ExportType;
                     case SyntaxKind.ModuleDeclaration:
-                        return (<ModuleDeclaration>d).name.kind === SyntaxKind.StringLiteral || getModuleInstanceState(d) !== ModuleInstanceState.NonInstantiated
+                        return isAmbientModule(d) || getModuleInstanceState(d) !== ModuleInstanceState.NonInstantiated
                             ? SymbolFlags.ExportNamespace | SymbolFlags.ExportValue
                             : SymbolFlags.ExportNamespace;
                     case SyntaxKind.ClassDeclaration:
@@ -12438,7 +12467,7 @@ namespace ts {
                 // checkFunctionOrConstructorSymbol wouldn't be called if we didnt ignore javascript function.
                 const firstDeclaration = forEach(localSymbol.declarations,
                     // Get first non javascript function declaration
-                    declaration => declaration.kind === node.kind && !isSourceFileJavaScript(getSourceFile(declaration)) ?
+                    declaration => declaration.kind === node.kind && !isSourceFileJavaScript(getSourceFileOfNode(declaration)) ?
                         declaration : undefined);
 
                 // Only type check the symbol once
@@ -14123,7 +14152,13 @@ namespace ts {
         function checkModuleDeclaration(node: ModuleDeclaration) {
             if (produceDiagnostics) {
                 // Grammar checking
-                const isAmbientExternalModule = node.name.kind === SyntaxKind.StringLiteral;
+                const isGlobalAugmentation = isGlobalScopeAugmentation(node);
+                const inAmbientContext = isInAmbientContext(node);
+                if (isGlobalAugmentation && !inAmbientContext) {
+                    error(node.name, Diagnostics.Augmentations_for_the_global_scope_should_have_declare_modifier_unless_they_appear_in_already_ambient_context);
+                }
+
+                const isAmbientExternalModule = isAmbientModule(node);
                 const contextErrorMessage = isAmbientExternalModule
                     ? Diagnostics.An_ambient_module_declaration_is_only_allowed_at_the_top_level_in_a_file
                     : Diagnostics.A_namespace_declaration_is_only_allowed_in_a_namespace_or_module;
@@ -14133,7 +14168,7 @@ namespace ts {
                 }
 
                 if (!checkGrammarDecorators(node) && !checkGrammarModifiers(node)) {
-                    if (!isInAmbientContext(node) && node.name.kind === SyntaxKind.StringLiteral) {
+                    if (!inAmbientContext && node.name.kind === SyntaxKind.StringLiteral) {
                         grammarErrorOnNode(node.name, Diagnostics.Only_ambient_modules_can_use_quoted_names);
                     }
                 }
@@ -14146,7 +14181,7 @@ namespace ts {
                 // The following checks only apply on a non-ambient instantiated module declaration.
                 if (symbol.flags & SymbolFlags.ValueModule
                     && symbol.declarations.length > 1
-                    && !isInAmbientContext(node)
+                    && !inAmbientContext
                     && isInstantiatedModule(node, compilerOptions.preserveConstEnums || compilerOptions.isolatedModules)) {
                     const firstNonAmbientClassOrFunc = getFirstNonAmbientClassOrFunctionDeclaration(symbol);
                     if (firstNonAmbientClassOrFunc) {
@@ -14167,19 +14202,107 @@ namespace ts {
                     }
                 }
 
-                // Checks for ambient external modules.
                 if (isAmbientExternalModule) {
-                    if (!isGlobalSourceFile(node.parent)) {
-                        error(node.name, Diagnostics.Ambient_modules_cannot_be_nested_in_other_modules_or_namespaces);
+                    if (isExternalModuleAugmentation(node)) {
+                        // body of the augmentation should be checked for consistency only if augmentation was applied to its target (either global scope or module)
+                        // otherwise we'll be swamped in cascading errors. 
+                        // We can detect if augmentation was applied using following rules:
+                        // - augmentation for a global scope is always applied
+                        // - augmentation for some external module is applied if symbol for augmentation is merged (it was combined with target module). 
+                        const checkBody = isGlobalAugmentation || (getSymbolOfNode(node).flags & SymbolFlags.Merged);
+                        if (checkBody) {
+                            // body of ambient external module is always a module block
+                            for (const statement of (<ModuleBlock>node.body).statements) {
+                                checkModuleAugmentationElement(statement, isGlobalAugmentation);
+                            }
+                        }
                     }
-                    if (isExternalModuleNameRelative(node.name.text)) {
-                        error(node.name, Diagnostics.Ambient_module_declaration_cannot_specify_relative_module_name);
+                    else if (isGlobalSourceFile(node.parent)) {
+                        if (isGlobalAugmentation) {
+                            error(node.name, Diagnostics.Augmentations_for_the_global_scope_can_only_be_directly_nested_in_external_modules_or_ambient_module_declarations);
+                        }
+                        else if (isExternalModuleNameRelative(node.name.text)) {
+                            error(node.name, Diagnostics.Ambient_module_declaration_cannot_specify_relative_module_name);
+                        }
+                    }
+                    else {
+                        if (isGlobalAugmentation) {
+                            error(node.name, Diagnostics.Augmentations_for_the_global_scope_can_only_be_directly_nested_in_external_modules_or_ambient_module_declarations);
+                        }
+                        else {
+                            // Node is not an augmentation and is not located on the script level.
+                            // This means that this is declaration of ambient module that is located in other module or namespace which is prohibited.
+                            error(node.name, Diagnostics.Ambient_modules_cannot_be_nested_in_other_modules_or_namespaces);
+                        }
                     }
                 }
             }
             checkSourceElement(node.body);
         }
 
+        function checkModuleAugmentationElement(node: Node, isGlobalAugmentation: boolean): void {
+            switch (node.kind) {
+                case SyntaxKind.VariableStatement:
+                    // error each individual name in variable statement instead of marking the entire variable statement
+                    for (const decl of (<VariableStatement>node).declarationList.declarations) {
+                        checkModuleAugmentationElement(decl, isGlobalAugmentation);
+                    }
+                    break;
+                case SyntaxKind.ExportAssignment:
+                case SyntaxKind.ExportDeclaration:
+                    grammarErrorOnFirstToken(node, Diagnostics.Exports_and_export_assignments_are_not_permitted_in_module_augmentations);
+                    break;
+                case SyntaxKind.ImportEqualsDeclaration:
+                    if ((<ImportEqualsDeclaration>node).moduleReference.kind !== SyntaxKind.StringLiteral) {
+                        error((<ImportEqualsDeclaration>node).name, Diagnostics.Module_augmentation_cannot_introduce_new_names_in_the_top_level_scope);
+                        break;
+                    }
+                    // fallthrough
+                case SyntaxKind.ImportDeclaration:
+                    grammarErrorOnFirstToken(node, Diagnostics.Imports_are_not_permitted_in_module_augmentations_Consider_moving_them_to_the_enclosing_external_module);
+                    break;
+                case SyntaxKind.BindingElement:
+                case SyntaxKind.VariableDeclaration:
+                    const name = (<VariableDeclaration | BindingElement>node).name;
+                    if (isBindingPattern(name)) {
+                        for (const el of name.elements) {
+                            // mark individual names in binding pattern
+                            checkModuleAugmentationElement(el, isGlobalAugmentation);
+                        }
+                        break;
+                    }
+                    // fallthrough
+                case SyntaxKind.ClassDeclaration:
+                case SyntaxKind.EnumDeclaration:
+                case SyntaxKind.FunctionDeclaration:
+                case SyntaxKind.InterfaceDeclaration:
+                case SyntaxKind.ModuleDeclaration:
+                case SyntaxKind.TypeAliasDeclaration:
+                    const symbol = getSymbolOfNode(node);
+                    if (symbol) {
+                        // module augmentations cannot introduce new names on the top level scope of the module
+                        // this is done it two steps
+                        // 1. quick check - if symbol for node is not merged - this is local symbol to this augmentation - report error
+                        // 2. main check - report error if value declaration of the parent symbol is module augmentation)
+                        let reportError = !(symbol.flags & SymbolFlags.Merged);
+                        if (!reportError) {
+                            if (isGlobalAugmentation) {
+                                // global symbol should not have parent since it is not explicitly exported
+                                reportError = symbol.parent !== undefined;
+                            }
+                            else {
+                                // symbol should not originate in augmentation
+                                reportError = isExternalModuleAugmentation(symbol.parent.valueDeclaration);
+                            }
+                        }
+                        if (reportError) {
+                            error(node, Diagnostics.Module_augmentation_cannot_introduce_new_names_in_the_top_level_scope);
+                        }
+                    }
+                    break;
+            }
+        }
+
         function getFirstIdentifier(node: EntityName | Expression): Identifier {
             while (true) {
                 if (node.kind === SyntaxKind.QualifiedName) {
@@ -14202,7 +14325,7 @@ namespace ts {
                 error(moduleName, Diagnostics.String_literal_expected);
                 return false;
             }
-            const inAmbientExternalModule = node.parent.kind === SyntaxKind.ModuleBlock && (<ModuleDeclaration>node.parent.parent).name.kind === SyntaxKind.StringLiteral;
+            const inAmbientExternalModule = node.parent.kind === SyntaxKind.ModuleBlock && isAmbientModule(<ModuleDeclaration>node.parent.parent);
             if (node.parent.kind !== SyntaxKind.SourceFile && !inAmbientExternalModule) {
                 error(moduleName, node.kind === SyntaxKind.ExportDeclaration ?
                     Diagnostics.Export_declarations_are_not_permitted_in_a_namespace :
@@ -14210,12 +14333,16 @@ namespace ts {
                 return false;
             }
             if (inAmbientExternalModule && isExternalModuleNameRelative((<LiteralExpression>moduleName).text)) {
-                // TypeScript 1.0 spec (April 2013): 12.1.6
-                // An ExternalImportDeclaration in an AmbientExternalModuleDeclaration may reference
-                // other external modules only through top - level external module names.
-                // Relative external module names are not permitted.
-                error(node, Diagnostics.Import_or_export_declaration_in_an_ambient_module_declaration_cannot_reference_module_through_relative_module_name);
-                return false;
+                // we have already reported errors on top level imports\exports in external module augmentations in checkModuleDeclaration
+                // no need to do this again.
+                if (!isTopLevelInExternalModuleAugmentation(node)) {
+                    // TypeScript 1.0 spec (April 2013): 12.1.6
+                    // An ExternalImportDeclaration in an AmbientExternalModuleDeclaration may reference
+                    // other external modules only through top - level external module names.
+                    // Relative external module names are not permitted.
+                    error(node, Diagnostics.Import_or_export_declaration_in_an_ambient_module_declaration_cannot_reference_module_through_relative_module_name);
+                    return false;
+                }
             }
             return true;
         }
@@ -14321,7 +14448,7 @@ namespace ts {
                     // export { x, y } from "foo"
                     forEach(node.exportClause.elements, checkExportSpecifier);
 
-                    const inAmbientExternalModule = node.parent.kind === SyntaxKind.ModuleBlock && (<ModuleDeclaration>node.parent.parent).name.kind === SyntaxKind.StringLiteral;
+                    const inAmbientExternalModule = node.parent.kind === SyntaxKind.ModuleBlock && isAmbientModule(node.parent.parent);
                     if (node.parent.kind !== SyntaxKind.SourceFile && !inAmbientExternalModule) {
                         error(node, Diagnostics.Export_declarations_are_not_permitted_in_a_namespace);
                     }
@@ -14365,7 +14492,7 @@ namespace ts {
             }
 
             const container = node.parent.kind === SyntaxKind.SourceFile ? <SourceFile>node.parent : <ModuleDeclaration>node.parent.parent;
-            if (container.kind === SyntaxKind.ModuleDeclaration && (<ModuleDeclaration>container).name.kind === SyntaxKind.Identifier) {
+            if (container.kind === SyntaxKind.ModuleDeclaration && !isAmbientModule(container)) {
                 error(node, Diagnostics.An_export_assignment_cannot_be_used_in_a_namespace);
                 return;
             }
@@ -14395,7 +14522,7 @@ namespace ts {
         }
 
         function hasExportedMembers(moduleSymbol: Symbol) {
-            for (var id in moduleSymbol.exports) {
+            for (const id in moduleSymbol.exports) {
                 if (id !== "export=") {
                     return true;
                 }
@@ -14410,7 +14537,9 @@ namespace ts {
                 const exportEqualsSymbol = moduleSymbol.exports["export="];
                 if (exportEqualsSymbol && hasExportedMembers(moduleSymbol)) {
                     const declaration = getDeclarationOfAliasSymbol(exportEqualsSymbol) || exportEqualsSymbol.valueDeclaration;
-                    error(declaration, Diagnostics.An_export_assignment_cannot_be_used_in_a_module_with_other_exported_elements);
+                    if (!isTopLevelInExternalModuleAugmentation(declaration)) {
+                        error(declaration, Diagnostics.An_export_assignment_cannot_be_used_in_a_module_with_other_exported_elements);
+                    }
                 }
                 // Checks for export * conflicts
                 const exports = getExportsOfModule(moduleSymbol);
@@ -15470,13 +15599,13 @@ namespace ts {
             };
         }
 
-        function getExternalModuleFileFromDeclaration(declaration: ImportEqualsDeclaration | ImportDeclaration | ExportDeclaration): SourceFile {
-                const specifier = getExternalModuleName(declaration);
-                const moduleSymbol = getSymbolAtLocation(specifier);
-                if (!moduleSymbol) {
-                    return undefined;
-                }
-                return getDeclarationOfKind(moduleSymbol, SyntaxKind.SourceFile) as SourceFile;
+        function getExternalModuleFileFromDeclaration(declaration: ImportEqualsDeclaration | ImportDeclaration | ExportDeclaration | ModuleDeclaration): SourceFile {
+            const specifier = getExternalModuleName(declaration);
+            const moduleSymbol = resolveExternalModuleNameWorker(specifier, specifier, /*moduleNotFoundError*/ undefined);
+            if (!moduleSymbol) {
+                return undefined;
+            }
+            return getDeclarationOfKind(moduleSymbol, SyntaxKind.SourceFile) as SourceFile;
         }
 
         function initializeTypeChecker() {
@@ -15485,13 +15614,27 @@ namespace ts {
                 bindSourceFile(file, compilerOptions);
             });
 
+            let augmentations: LiteralExpression[][];
             // Initialize global symbol table
             forEach(host.getSourceFiles(), file => {
                 if (!isExternalOrCommonJsModule(file)) {
                     mergeSymbolTable(globals, file.locals);
                 }
+                if (file.moduleAugmentations) {
+                    (augmentations || (augmentations = [])).push(file.moduleAugmentations);
+                }
             });
 
+            if (augmentations) {
+                // merge module augmentations.
+                // this needs to be done after global symbol table is initialized to make sure that all ambient modules are indexed
+                for (const list of augmentations) {
+                    for (const augmentation of list) {
+                        mergeModuleAugmentation(augmentation);
+                    }
+                }
+            }
+
             // Setup global builtins
             addToSymbolTable(globals, builtinGlobals, Diagnostics.Declaration_name_conflicts_with_built_in_global_identifier_0);
 
@@ -16307,7 +16450,7 @@ namespace ts {
                     return true;
                 }
                 else if (node.body === undefined) {
-                    return grammarErrorAtPos(getSourceFile(node), node.end - 1, ";".length, Diagnostics._0_expected, "{");
+                    return grammarErrorAtPos(getSourceFileOfNode(node), node.end - 1, ";".length, Diagnostics._0_expected, "{");
                 }
             }
 
diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index 4056d9c3e9..cfdcb2b930 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -718,7 +718,8 @@ namespace ts {
         }
 
         // Find the component that differs
-        for (var joinStartIndex = 0; joinStartIndex < pathComponents.length && joinStartIndex < directoryComponents.length; joinStartIndex++) {
+        let joinStartIndex: number;
+        for (joinStartIndex = 0; joinStartIndex < pathComponents.length && joinStartIndex < directoryComponents.length; joinStartIndex++) {
             if (getCanonicalFileName(directoryComponents[joinStartIndex]) !== getCanonicalFileName(pathComponents[joinStartIndex])) {
                 break;
             }
diff --git a/src/compiler/declarationEmitter.ts b/src/compiler/declarationEmitter.ts
index 75319d0ab5..9a57b4b1a3 100644
--- a/src/compiler/declarationEmitter.ts
+++ b/src/compiler/declarationEmitter.ts
@@ -54,6 +54,7 @@ namespace ts {
         let writer = createAndSetNewTextWriterWithSymbolWriter();
 
         let enclosingDeclaration: Node;
+        let resultHasExternalModuleIndicator: boolean;
         let currentText: string;
         let currentLineMap: number[];
         let currentIdentifiers: Map<string>;
@@ -101,6 +102,7 @@ namespace ts {
                 });
             }
 
+            resultHasExternalModuleIndicator = false;
             if (!isBundledEmit || !isExternalModule(sourceFile)) {
                 noDeclare = false;
                 emitSourceFile(sourceFile);
@@ -139,6 +141,14 @@ namespace ts {
                 allSourcesModuleElementDeclarationEmitInfo = allSourcesModuleElementDeclarationEmitInfo.concat(moduleElementDeclarationEmitInfo);
                 moduleElementDeclarationEmitInfo = [];
             }
+
+            if (!isBundledEmit && isExternalModule(sourceFile) && sourceFile.moduleAugmentations.length && !resultHasExternalModuleIndicator) {
+                // if file was external module with augmentations - this fact should be preserved in .d.ts as well.
+                // in case if we didn't write any external module specifiers in .d.ts we need to emit something 
+                // that will force compiler to think that this file is an external module - 'export {}' is a reasonable choice here.
+                write("export {};");
+                writeLine();
+            }
         });
 
         return {
@@ -721,16 +731,25 @@ namespace ts {
             writer.writeLine();
         }
 
-        function emitExternalModuleSpecifier(parent: ImportEqualsDeclaration | ImportDeclaration | ExportDeclaration) {
+        function emitExternalModuleSpecifier(parent: ImportEqualsDeclaration | ImportDeclaration | ExportDeclaration | ModuleDeclaration) {
+            // emitExternalModuleSpecifier is usually called when we emit something in the.d.ts file that will make it an external module (i.e. import/export declarations).
+            // the only case when it is not true is when we call it to emit correct name for module augmentation - d.ts files with just module augmentations are not considered 
+            // external modules since they are indistingushable from script files with ambient modules. To fix this in such d.ts files we'll emit top level 'export {}'
+            // so compiler will treat them as external modules.
+            resultHasExternalModuleIndicator = resultHasExternalModuleIndicator || parent.kind !== SyntaxKind.ModuleDeclaration;
             let moduleSpecifier: Node;
             if (parent.kind === SyntaxKind.ImportEqualsDeclaration) {
                 const node = parent as ImportEqualsDeclaration;
                 moduleSpecifier = getExternalModuleImportEqualsDeclarationExpression(node);
             }
+            else if (parent.kind === SyntaxKind.ModuleDeclaration) {
+                moduleSpecifier = (<ModuleDeclaration>parent).name;
+            }
             else {
                 const node = parent as (ImportDeclaration | ExportDeclaration);
                 moduleSpecifier = node.moduleSpecifier;
             }
+
             if (moduleSpecifier.kind === SyntaxKind.StringLiteral && isBundledEmit && (compilerOptions.out || compilerOptions.outFile)) {
                 const moduleName = getExternalModuleNameFromDeclaration(host, resolver, parent);
                 if (moduleName) {
@@ -784,13 +803,23 @@ namespace ts {
         function writeModuleDeclaration(node: ModuleDeclaration) {
             emitJsDocComments(node);
             emitModuleElementDeclarationFlags(node);
-            if (node.flags & NodeFlags.Namespace) {
-                write("namespace ");
+            if (isGlobalScopeAugmentation(node)) {
+                write("global ");
             }
             else {
-                write("module ");
+                if (node.flags & NodeFlags.Namespace) {
+                    write("namespace ");
+                }
+                else {
+                    write("module ");
+                }
+                if (isExternalModuleAugmentation(node)) {
+                    emitExternalModuleSpecifier(node);
+                }
+                else {
+                    writeTextOfNode(currentText, node.name);
+                }
             }
-            writeTextOfNode(currentText, node.name);
             while (node.body.kind !== SyntaxKind.ModuleBlock) {
                 node = <ModuleDeclaration>node.body;
                 write(".");
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 760da6058c..8fd40f7b42 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1767,6 +1767,42 @@
         "category": "Error",
         "code": 2661
     },
+    "Cannot find name '{0}'. Did you mean the static member '{1}.{0}'?": {
+        "category": "Error",
+        "code": 2662
+    },
+    "Cannot find name '{0}'. Did you mean the instance member 'this.{0}'?": {
+        "category": "Error",
+        "code": 2663
+    },
+    "Invalid module name in augmentation, module '{0}' cannot be found.": {
+        "category": "Error",
+        "code": 2664
+    },
+    "Module augmentation cannot introduce new names in the top level scope.": {
+        "category": "Error",
+        "code": 2665
+    },
+    "Exports and export assignments are not permitted in module augmentations.": {
+        "category": "Error",
+        "code": 2666
+    },
+    "Imports are not permitted in module augmentations. Consider moving them to the enclosing external module.": {
+        "category": "Error",
+        "code": 2667
+    },
+    "'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.": {
+        "category": "Error",
+        "code": 2668
+    },
+    "Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.": {
+        "category": "Error",
+        "code": 2669
+    },
+    "Augmentations for the global scope should have 'declare' modifier unless they appear in already ambient context.": {
+        "category": "Error",
+        "code": 2670
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index 1ebbbe74ab..96c655ac90 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -1250,7 +1250,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
                         else {
                             // One object literal with all the attributes in them
                             write("{");
-                            for (var i = 0; i < attrs.length; i++) {
+                            for (let i = 0, n = attrs.length; i < n; i++) {
                                 if (i > 0) {
                                     write(", ");
                                 }
@@ -1262,7 +1262,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
 
                     // Children
                     if (children) {
-                        for (var i = 0; i < children.length; i++) {
+                        for (let i = 0; i < children.length; i++) {
                             // Don't emit empty expressions
                             if (children[i].kind === SyntaxKind.JsxExpression && !((<JsxExpression>children[i]).expression)) {
                                 continue;
@@ -1356,7 +1356,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
                 function emitJsxElement(node: JsxElement) {
                     emitJsxOpeningOrSelfClosingElement(node.openingElement);
 
-                    for (var i = 0, n = node.children.length; i < n; i++) {
+                    for (let i = 0, n = node.children.length; i < n; i++) {
                         emit(node.children[i]);
                     }
 
@@ -2886,7 +2886,8 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
                     case SyntaxKind.ForStatement:
                     case SyntaxKind.ForInStatement:
                     case SyntaxKind.ForOfStatement:
-                        if ((<ForStatement | ForInStatement | ForOfStatement>node).initializer.kind === SyntaxKind.VariableDeclarationList) {
+                        const initializer = (<ForStatement | ForInStatement | ForOfStatement>node).initializer;
+                        if (initializer && initializer.kind === SyntaxKind.VariableDeclarationList) {
                             loopInitializer = <VariableDeclarationList>(<ForStatement | ForInStatement | ForOfStatement>node).initializer;
                         }
                         break;
@@ -5171,7 +5172,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
                 //                                  a lexical declaration such as a LexicalDeclaration or a ClassDeclaration.
 
                 if (isClassExpressionWithStaticProperties) {
-                    for (var property of staticProperties) {
+                    for (const property of staticProperties) {
                         write(",");
                         writeLine();
                         emitPropertyDeclaration(node, property, /*receiver*/ tempVariable, /*isExpression*/ true);
@@ -5718,7 +5719,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
                         const parameters = valueDeclaration.parameters;
                         const parameterCount = parameters.length;
                         if (parameterCount > 0) {
-                            for (var i = 0; i < parameterCount; i++) {
+                            for (let i = 0; i < parameterCount; i++) {
                                 if (i > 0) {
                                     write(", ");
                                 }
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 420d201adc..e391408b41 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -4430,6 +4430,9 @@ namespace ts {
                         }
                         continue;
 
+                    case SyntaxKind.GlobalKeyword:
+                        return nextToken() === SyntaxKind.OpenBraceToken;
+
                     case SyntaxKind.ImportKeyword:
                         nextToken();
                         return token === SyntaxKind.StringLiteral || token === SyntaxKind.AsteriskToken ||
@@ -4494,6 +4497,7 @@ namespace ts {
                 case SyntaxKind.ModuleKeyword:
                 case SyntaxKind.NamespaceKeyword:
                 case SyntaxKind.TypeKeyword:
+                case SyntaxKind.GlobalKeyword:
                     // When these don't start a declaration, they're an identifier in an expression statement
                     return true;
 
@@ -4582,6 +4586,7 @@ namespace ts {
                 case SyntaxKind.PublicKeyword:
                 case SyntaxKind.AbstractKeyword:
                 case SyntaxKind.StaticKeyword:
+                case SyntaxKind.GlobalKeyword:
                     if (isStartOfDeclaration()) {
                         return parseDeclaration();
                     }
@@ -4609,6 +4614,7 @@ namespace ts {
                     return parseTypeAliasDeclaration(fullStart, decorators, modifiers);
                 case SyntaxKind.EnumKeyword:
                     return parseEnumDeclaration(fullStart, decorators, modifiers);
+                case SyntaxKind.GlobalKeyword:
                 case SyntaxKind.ModuleKeyword:
                 case SyntaxKind.NamespaceKeyword:
                     return parseModuleDeclaration(fullStart, decorators, modifiers);
@@ -5243,14 +5249,25 @@ namespace ts {
             const node = <ModuleDeclaration>createNode(SyntaxKind.ModuleDeclaration, fullStart);
             node.decorators = decorators;
             setModifiers(node, modifiers);
-            node.name = parseLiteralNode(/*internName*/ true);
+            if (token === SyntaxKind.GlobalKeyword) {
+                // parse 'global' as name of global scope augmentation 
+                node.name = parseIdentifier();
+                node.flags |= NodeFlags.GlobalAugmentation;
+            }
+            else {
+                node.name = parseLiteralNode(/*internName*/ true);
+            }
             node.body = parseModuleBlock();
             return finishNode(node);
         }
 
         function parseModuleDeclaration(fullStart: number, decorators: NodeArray<Decorator>, modifiers: ModifiersArray): ModuleDeclaration {
             let flags = modifiers ? modifiers.flags : 0;
-            if (parseOptional(SyntaxKind.NamespaceKeyword)) {
+            if (token === SyntaxKind.GlobalKeyword) {
+                // global augmentation
+                return parseAmbientExternalModuleDeclaration(fullStart, decorators, modifiers);
+            }
+            else if (parseOptional(SyntaxKind.NamespaceKeyword)) {
                 flags |= NodeFlags.Namespace;
             }
             else {
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 6905e01b1e..398ce27ef4 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -361,7 +361,24 @@ namespace ts {
         const currentDirectory = host.getCurrentDirectory();
         const resolveModuleNamesWorker = host.resolveModuleNames
             ? ((moduleNames: string[], containingFile: string) => host.resolveModuleNames(moduleNames, containingFile))
-            : ((moduleNames: string[], containingFile: string) => map(moduleNames, moduleName => resolveModuleName(moduleName, containingFile, options, host).resolvedModule));
+            : ((moduleNames: string[], containingFile: string) => {
+                const resolvedModuleNames: ResolvedModule[] = [];
+                // resolveModuleName does not store any results between calls.
+                // lookup is a local cache to avoid resolving the same module name several times
+                const lookup: Map<ResolvedModule> = {};
+                for (const moduleName of moduleNames) {
+                    let resolvedName: ResolvedModule;
+                    if (hasProperty(lookup, moduleName)) {
+                        resolvedName = lookup[moduleName];
+                    }
+                    else {
+                        resolvedName = resolveModuleName(moduleName, containingFile, options, host).resolvedModule;
+                        lookup[moduleName] = resolvedName;
+                    }
+                    resolvedModuleNames.push(resolvedName);
+                }
+                return resolvedModuleNames;
+            });
 
         const filesByName = createFileMap<SourceFile>();
         // stores 'filename -> file association' ignoring case
@@ -498,15 +515,19 @@ namespace ts {
                         return false;
                     }
 
-                    // check imports
+                    // check imports and module augmentations
                     collectExternalModuleReferences(newSourceFile);
                     if (!arrayIsEqualTo(oldSourceFile.imports, newSourceFile.imports, moduleNameIsEqualTo)) {
                         // imports has changed
                         return false;
                     }
+                    if (!arrayIsEqualTo(oldSourceFile.moduleAugmentations, newSourceFile.moduleAugmentations, moduleNameIsEqualTo)) {
+                        // moduleAugmentations has changed
+                        return false;
+                    }
 
                     if (resolveModuleNamesWorker) {
-                        const moduleNames = map(newSourceFile.imports, name => name.text);
+                        const moduleNames = map(concatenate(newSourceFile.imports, newSourceFile.moduleAugmentations), getTextOfLiteral);
                         const resolutions = resolveModuleNamesWorker(moduleNames, getNormalizedAbsolutePath(newSourceFile.fileName, currentDirectory));
                         // ensure that module resolution results are still correct
                         for (let i = 0; i < moduleNames.length; i++) {
@@ -895,65 +916,85 @@ namespace ts {
             return a.text === b.text;
         }
 
+        function getTextOfLiteral(literal: LiteralExpression): string {
+            return literal.text;
+        }
+
         function collectExternalModuleReferences(file: SourceFile): void {
             if (file.imports) {
                 return;
             }
 
             const isJavaScriptFile = isSourceFileJavaScript(file);
+            const isExternalModuleFile = isExternalModule(file);
 
             let imports: LiteralExpression[];
+            let moduleAugmentations: LiteralExpression[];
+
             for (const node of file.statements) {
-                collect(node, /*allowRelativeModuleNames*/ true, /*collectOnlyRequireCalls*/ false);
+                collectModuleReferences(node, /*inAmbientModule*/ false);
+                if (isJavaScriptFile) {
+                    collectRequireCalls(node);
+                }
             }
 
             file.imports = imports || emptyArray;
+            file.moduleAugmentations = moduleAugmentations || emptyArray;
 
             return;
 
-            function collect(node: Node, allowRelativeModuleNames: boolean, collectOnlyRequireCalls: boolean): void {
-                if (!collectOnlyRequireCalls) {
-                    switch (node.kind) {
-                        case SyntaxKind.ImportDeclaration:
-                        case SyntaxKind.ImportEqualsDeclaration:
-                        case SyntaxKind.ExportDeclaration:
-                            let moduleNameExpr = getExternalModuleName(node);
-                            if (!moduleNameExpr || moduleNameExpr.kind !== SyntaxKind.StringLiteral) {
-                                break;
-                            }
-                            if (!(<LiteralExpression>moduleNameExpr).text) {
-                                break;
-                            }
-
-                            if (allowRelativeModuleNames || !isExternalModuleNameRelative((<LiteralExpression>moduleNameExpr).text)) {
-                                (imports || (imports = [])).push(<LiteralExpression>moduleNameExpr);
-                            }
+            function collectModuleReferences(node: Node, inAmbientModule: boolean): void {
+                switch (node.kind) {
+                    case SyntaxKind.ImportDeclaration:
+                    case SyntaxKind.ImportEqualsDeclaration:
+                    case SyntaxKind.ExportDeclaration:
+                        let moduleNameExpr = getExternalModuleName(node);
+                        if (!moduleNameExpr || moduleNameExpr.kind !== SyntaxKind.StringLiteral) {
                             break;
-                        case SyntaxKind.ModuleDeclaration:
-                            if ((<ModuleDeclaration>node).name.kind === SyntaxKind.StringLiteral && (node.flags & NodeFlags.Ambient || isDeclarationFile(file))) {
-                                // TypeScript 1.0 spec (April 2014): 12.1.6
+                        }
+                        if (!(<LiteralExpression>moduleNameExpr).text) {
+                            break;
+                        }
+
+                        // TypeScript 1.0 spec (April 2014): 12.1.6
+                        // An ExternalImportDeclaration in an AmbientExternalModuleDeclaration may reference other external modules 
+                        // only through top - level external module names. Relative external module names are not permitted.
+                        if (!inAmbientModule || !isExternalModuleNameRelative((<LiteralExpression>moduleNameExpr).text)) {
+                            (imports || (imports = [])).push(<LiteralExpression>moduleNameExpr);
+                        }
+                        break;
+                    case SyntaxKind.ModuleDeclaration:
+                        if (isAmbientModule(<ModuleDeclaration>node) && (inAmbientModule || node.flags & NodeFlags.Ambient || isDeclarationFile(file))) {
+                            const moduleName = <LiteralExpression>(<ModuleDeclaration>node).name;
+                            // Ambient module declarations can be interpreted as augmentations for some existing external modules.
+                            // This will happen in two cases:
+                            // - if current file is external module then module augmentation is a ambient module declaration defined in the top level scope
+                            // - if current file is not external module then module augmentation is an ambient module declaration with non-relative module name
+                            //   immediately nested in top level ambient module declaration .
+                            if (isExternalModuleFile || (inAmbientModule && !isExternalModuleNameRelative(moduleName.text))) {
+                                (moduleAugmentations || (moduleAugmentations = [])).push(moduleName);
+                            }
+                            else if (!inAmbientModule) {
                                 // An AmbientExternalModuleDeclaration declares an external module. 
                                 // This type of declaration is permitted only in the global module.
                                 // The StringLiteral must specify a top - level external module name.
                                 // Relative external module names are not permitted
-                                forEachChild((<ModuleDeclaration>node).body, node => {
-                                    // TypeScript 1.0 spec (April 2014): 12.1.6
-                                    // An ExternalImportDeclaration in anAmbientExternalModuleDeclaration may reference other external modules 
-                                    // only through top - level external module names. Relative external module names are not permitted.
-                                    collect(node, /*allowRelativeModuleNames*/ false, collectOnlyRequireCalls);
-                                });
-                            }
-                            break;
-                    }
-                }
 
-                if (isJavaScriptFile) {
-                    if (isRequireCall(node)) {
-                        (imports || (imports = [])).push(<StringLiteral>(<CallExpression>node).arguments[0]);
-                    }
-                    else {
-                        forEachChild(node, node => collect(node, allowRelativeModuleNames, /*collectOnlyRequireCalls*/ true));
-                    }
+                                // NOTE: body of ambient module is always a module block
+                                for (const statement of (<ModuleBlock>(<ModuleDeclaration>node).body).statements) {
+                                    collectModuleReferences(statement, /*inAmbientModule*/ true);
+                                }
+                            }
+                        }
+                }
+            }
+
+            function collectRequireCalls(node: Node): void {
+                if (isRequireCall(node)) {
+                    (imports || (imports = [])).push(<StringLiteral>(<CallExpression>node).arguments[0]);
+                }
+                else {
+                    forEachChild(node, collectRequireCalls);
                 }
             }
         }
@@ -1083,14 +1124,22 @@ namespace ts {
 
         function processImportedModules(file: SourceFile, basePath: string) {
             collectExternalModuleReferences(file);
-            if (file.imports.length) {
+            if (file.imports.length || file.moduleAugmentations.length) {
                 file.resolvedModules = {};
-                const moduleNames = map(file.imports, name => name.text);
+                const moduleNames = map(concatenate(file.imports, file.moduleAugmentations), getTextOfLiteral);
                 const resolutions = resolveModuleNamesWorker(moduleNames, getNormalizedAbsolutePath(file.fileName, currentDirectory));
-                for (let i = 0; i < file.imports.length; i++) {
+                for (let i = 0; i < moduleNames.length; i++) {
                     const resolution = resolutions[i];
                     setResolvedModule(file, moduleNames[i], resolution);
-                    if (resolution && !options.noResolve) {
+                    // add file to program only if:
+                    // - resolution was successfull
+                    // - noResolve is falsy
+                    // - module name come from the list fo imports
+                    const shouldAddFile = resolution &&
+                        !options.noResolve &&
+                        i < file.imports.length;
+
+                    if (shouldAddFile) {
                         const importedFile = findSourceFile(resolution.resolvedFileName, toPath(resolution.resolvedFileName, currentDirectory, getCanonicalFileName), /*isDefaultLib*/ false, file, skipTrivia(file.text, file.imports[i].pos), file.imports[i].end);
 
                         if (importedFile && resolution.isExternalLibraryImport) {
@@ -1168,7 +1217,7 @@ namespace ts {
             if (sourceFiles) {
                 const absoluteRootDirectoryPath = host.getCanonicalFileName(getNormalizedAbsolutePath(rootDirectory, currentDirectory));
 
-                for (var sourceFile of sourceFiles) {
+                for (const sourceFile of sourceFiles) {
                     if (!isDeclarationFile(sourceFile)) {
                         const absoluteSourceFilePath = host.getCanonicalFileName(getNormalizedAbsolutePath(sourceFile.fileName, currentDirectory));
                         if (absoluteSourceFilePath.indexOf(absoluteRootDirectoryPath) !== 0) {
diff --git a/src/compiler/scanner.ts b/src/compiler/scanner.ts
index 8161ea998c..7192ba6b40 100644
--- a/src/compiler/scanner.ts
+++ b/src/compiler/scanner.ts
@@ -94,6 +94,7 @@ namespace ts {
         "protected": SyntaxKind.ProtectedKeyword,
         "public": SyntaxKind.PublicKeyword,
         "require": SyntaxKind.RequireKeyword,
+        "global": SyntaxKind.GlobalKeyword,
         "return": SyntaxKind.ReturnKeyword,
         "set": SyntaxKind.SetKeyword,
         "static": SyntaxKind.StaticKeyword,
diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index e6f908d250..bf25d39aa4 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -376,9 +376,11 @@ namespace ts {
                 /**
                  * @param watcherPath is the path from which the watcher is triggered.
                  */
-                function fileEventHandler(eventName: string, relativefileName: string, baseDirPath: Path) {
+                function fileEventHandler(eventName: string, relativeFileName: string, baseDirPath: Path) {
                     // When files are deleted from disk, the triggered "rename" event would have a relativefileName of "undefined"
-                    const filePath = relativefileName === undefined ? undefined : toPath(relativefileName, baseDirPath, getCanonicalPath);
+                    const filePath = typeof relativeFileName !== "string"
+                        ? undefined
+                        : toPath(relativeFileName, baseDirPath, createGetCanonicalFileName(sys.useCaseSensitiveFileNames));
                     if (eventName === "change" && fileWatcherCallbacks.contains(filePath)) {
                         for (const fileCallback of fileWatcherCallbacks.get(filePath)) {
                             fileCallback(filePath);
@@ -460,7 +462,7 @@ namespace ts {
             }
 
             function getCanonicalPath(path: string): string {
-                return useCaseSensitiveFileNames ? path.toLowerCase() : path;
+                return useCaseSensitiveFileNames ? path : path.toLowerCase();
             }
 
             function readDirectory(path: string, extension?: string, exclude?: string[]): string[] {
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index a4632bed3b..18dc6602ab 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -170,6 +170,7 @@ namespace ts {
         SymbolKeyword,
         TypeKeyword,
         FromKeyword,
+        GlobalKeyword,
         OfKeyword, // LastKeyword and LastToken
 
         // Parse tree nodes
@@ -389,10 +390,11 @@ namespace ts {
         ContainsThis =      1 << 18,  // Interface contains references to "this"
         HasImplicitReturn =     1 << 19,  // If function implicitly returns on one of codepaths (initialized by binding)
         HasExplicitReturn =     1 << 20,  // If function has explicit reachable return on one of codepaths (initialized by binding)
-        HasClassExtends =       1 << 21,  // If the file has a non-ambient class with an extends clause in ES5 or lower (initialized by binding)
-        HasDecorators =         1 << 22,  // If the file has decorators (initialized by binding)
-        HasParamDecorators =    1 << 23,  // If the file has parameter decorators (initialized by binding)
-        HasAsyncFunctions =     1 << 24,  // If the file has async functions (initialized by binding)
+        GlobalAugmentation =    1 << 21,  // Set if module declaration is an augmentation for the global scope
+        HasClassExtends =       1 << 22,  // If the file has a non-ambient class with an extends clause in ES5 or lower (initialized by binding)
+        HasDecorators =         1 << 23,  // If the file has decorators (initialized by binding)
+        HasParamDecorators =    1 << 24,  // If the file has parameter decorators (initialized by binding)
+        HasAsyncFunctions =     1 << 25,  // If the file has async functions (initialized by binding)
 
         Modifier = Export | Ambient | Public | Private | Protected | Static | Abstract | Default | Async,
         AccessibilityModifier = Public | Private | Protected,
@@ -1583,6 +1585,7 @@ namespace ts {
         // Content of this fiels should never be used directly - use getResolvedModuleFileName/setResolvedModuleFileName functions instead
         /* @internal */ resolvedModules: Map<ResolvedModule>;
         /* @internal */ imports: LiteralExpression[];
+        /* @internal */ moduleAugmentations: LiteralExpression[];
     }
 
     export interface ScriptReferenceHost {
@@ -1917,7 +1920,7 @@ namespace ts {
         isOptionalParameter(node: ParameterDeclaration): boolean;
         moduleExportsSomeValue(moduleReferenceExpression: Expression): boolean;
         isArgumentsLocalBinding(node: Identifier): boolean;
-        getExternalModuleFileFromDeclaration(declaration: ImportEqualsDeclaration | ImportDeclaration | ExportDeclaration): SourceFile;
+        getExternalModuleFileFromDeclaration(declaration: ImportEqualsDeclaration | ImportDeclaration | ExportDeclaration | ModuleDeclaration): SourceFile;
     }
 
     export const enum SymbolFlags {
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 3553430bcd..69941a6095 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -251,6 +251,31 @@ namespace ts {
             isCatchClauseVariableDeclaration(declaration);
     }
 
+    export function isAmbientModule(node: Node): boolean {
+        return node && node.kind === SyntaxKind.ModuleDeclaration &&
+            ((<ModuleDeclaration>node).name.kind === SyntaxKind.StringLiteral || isGlobalScopeAugmentation(<ModuleDeclaration>node));
+    }
+
+    export function isGlobalScopeAugmentation(module: ModuleDeclaration): boolean {
+        return !!(module.flags & NodeFlags.GlobalAugmentation);
+    }
+
+    export function isExternalModuleAugmentation(node: Node): boolean {
+        // external module augmentation is a ambient module declaration that is either:
+        // - defined in the top level scope and source file is an external module
+        // - defined inside ambient module declaration located in the top level scope and source file not an external module
+        if (!node || !isAmbientModule(node)) {
+            return false;
+        }
+        switch (node.parent.kind) {
+            case SyntaxKind.SourceFile:
+                return isExternalModule(<SourceFile>node.parent);
+            case SyntaxKind.ModuleBlock:
+                return isAmbientModule(node.parent.parent) && !isExternalModule(<SourceFile>node.parent.parent.parent);
+        }
+        return false;
+    }
+
     // Gets the nearest enclosing block scope container that has the provided node
     // as a descendant, that is not the provided node.
     export function getEnclosingBlockScopeContainer(node: Node): Node {
@@ -343,6 +368,7 @@ namespace ts {
             case SyntaxKind.FunctionDeclaration:
             case SyntaxKind.FunctionExpression:
             case SyntaxKind.MethodDeclaration:
+            case SyntaxKind.TypeAliasDeclaration:
                 errorNode = (<Declaration>node).name;
                 break;
         }
@@ -1115,6 +1141,9 @@ namespace ts {
         if (node.kind === SyntaxKind.ExportDeclaration) {
             return (<ExportDeclaration>node).moduleSpecifier;
         }
+        if (node.kind === SyntaxKind.ModuleDeclaration && (<ModuleDeclaration>node).name.kind === SyntaxKind.StringLiteral) {
+            return (<ModuleDeclaration>node).name;
+        }
     }
 
     export function hasQuestionToken(node: Node) {
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index fd9f1077dd..7cc3a6c96a 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -1002,7 +1002,9 @@ namespace ts.server {
                     info.setFormatOptions(this.getFormatCodeOptions());
                     this.filenameToScriptInfo[fileName] = info;
                     if (!info.isOpen) {
-                        info.fileWatcher = this.host.watchFile(<Path>fileName, _ => { this.watchedFileChanged(fileName); });
+                        info.fileWatcher = this.host.watchFile(
+                            toPath(fileName, fileName, createGetCanonicalFileName(sys.useCaseSensitiveFileNames)),
+                            _ => { this.watchedFileChanged(fileName); });
                     }
                 }
             }
@@ -1215,7 +1217,9 @@ namespace ts.server {
                     }
                 }
                 project.finishGraph();
-                project.projectFileWatcher = this.host.watchFile(<Path>configFilename, _ => this.watchedProjectConfigFileChanged(project));
+                project.projectFileWatcher = this.host.watchFile(
+                    toPath(configFilename, configFilename, createGetCanonicalFileName(sys.useCaseSensitiveFileNames)),
+                    _ => this.watchedProjectConfigFileChanged(project));
                 this.log("Add recursive watcher for: " + ts.getDirectoryPath(configFilename));
                 project.directoryWatcher = this.host.watchDirectory(
                     ts.getDirectoryPath(configFilename),
diff --git a/src/services/navigationBar.ts b/src/services/navigationBar.ts
index 46ec807a88..f62c6cb170 100644
--- a/src/services/navigationBar.ts
+++ b/src/services/navigationBar.ts
@@ -387,7 +387,7 @@ namespace ts.NavigationBar {
 
             function getModuleName(moduleDeclaration: ModuleDeclaration): string {
                 // We want to maintain quotation marks.
-                if (moduleDeclaration.name.kind === SyntaxKind.StringLiteral) {
+                if (isAmbientModule(moduleDeclaration)) {
                     return getTextOfNode(moduleDeclaration.name);
                 }
 
diff --git a/src/services/services.ts b/src/services/services.ts
index 8e998760b4..0fae1c0aa4 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -811,6 +811,7 @@ namespace ts {
         public nameTable: Map<string>;
         public resolvedModules: Map<ResolvedModule>;
         public imports: LiteralExpression[];
+        public moduleAugmentations: LiteralExpression[];
         private namedDeclarations: Map<Declaration[]>;
 
         constructor(kind: SyntaxKind, pos: number, end: number) {
@@ -6028,6 +6029,10 @@ namespace ts {
              */
             function getPropertySymbolsFromBaseTypes(symbol: Symbol, propertyName: string, result: Symbol[],
                 previousIterationSymbolsCache: SymbolTable): void {
+                if (!symbol) {
+                    return;
+                }
+
                 // If the current symbol is the same as the previous-iteration symbol, we can just return the symbol that has already been visited
                 // This is particularly important for the following cases, so that we do not infinitely visit the same symbol.
                 // For example:
@@ -6043,7 +6048,7 @@ namespace ts {
                     return;
                 }
 
-                if (symbol && symbol.flags & (SymbolFlags.Class | SymbolFlags.Interface)) {
+                if (symbol.flags & (SymbolFlags.Class | SymbolFlags.Interface)) {
                     forEach(symbol.getDeclarations(), declaration => {
                         if (declaration.kind === SyntaxKind.ClassDeclaration) {
                             getPropertySymbolFromTypeReference(getClassExtendsHeritageClauseElement(<ClassDeclaration>declaration));
@@ -6292,7 +6297,7 @@ namespace ts {
                     return SemanticMeaning.Value | SemanticMeaning.Type;
 
                 case SyntaxKind.ModuleDeclaration:
-                    if ((<ModuleDeclaration>node).name.kind === SyntaxKind.StringLiteral) {
+                    if (isAmbientModule(<ModuleDeclaration>node)) {
                         return SemanticMeaning.Namespace | SemanticMeaning.Value;
                     }
                     else if (getModuleInstanceState(node) === ModuleInstanceState.Instantiated) {
@@ -6823,7 +6828,8 @@ namespace ts {
             function classifyDisabledMergeCode(text: string, start: number, end: number) {
                 // Classify the line that the ======= marker is on as a comment.  Then just lex
                 // all further tokens and add them to the result.
-                for (var i = start; i < end; i++) {
+                let i: number;
+                for (i = start; i < end; i++) {
                     if (isLineBreak(text.charCodeAt(i))) {
                         break;
                     }
diff --git a/tests/baselines/reference/YieldExpression11_es6.errors.txt b/tests/baselines/reference/YieldExpression11_es6.errors.txt
index c19e8b6cfa..1b0c08bd79 100644
--- a/tests/baselines/reference/YieldExpression11_es6.errors.txt
+++ b/tests/baselines/reference/YieldExpression11_es6.errors.txt
@@ -1,5 +1,5 @@
 tests/cases/conformance/es6/yieldExpressions/YieldExpression11_es6.ts(2,3): error TS1220: Generators are only available when targeting ECMAScript 6 or higher.
-tests/cases/conformance/es6/yieldExpressions/YieldExpression11_es6.ts(3,11): error TS2304: Cannot find name 'foo'.
+tests/cases/conformance/es6/yieldExpressions/YieldExpression11_es6.ts(3,11): error TS2663: Cannot find name 'foo'. Did you mean the instance member 'this.foo'?
 
 
 ==== tests/cases/conformance/es6/yieldExpressions/YieldExpression11_es6.ts (2 errors) ====
@@ -9,6 +9,6 @@ tests/cases/conformance/es6/yieldExpressions/YieldExpression11_es6.ts(3,11): err
 !!! error TS1220: Generators are only available when targeting ECMAScript 6 or higher.
         yield(foo);
               ~~~
-!!! error TS2304: Cannot find name 'foo'.
+!!! error TS2663: Cannot find name 'foo'. Did you mean the instance member 'this.foo'?
       }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/accessInstanceMemberFromStaticMethod01.errors.txt b/tests/baselines/reference/accessInstanceMemberFromStaticMethod01.errors.txt
new file mode 100644
index 0000000000..0ce9c61461
--- /dev/null
+++ b/tests/baselines/reference/accessInstanceMemberFromStaticMethod01.errors.txt
@@ -0,0 +1,13 @@
+tests/cases/compiler/accessInstanceMemberFromStaticMethod01.ts(5,17): error TS2662: Cannot find name 'foo'. Did you mean the static member 'C.foo'?
+
+
+==== tests/cases/compiler/accessInstanceMemberFromStaticMethod01.ts (1 errors) ====
+    class C {
+        static foo: string;
+    
+        bar() {
+            let k = foo;
+                    ~~~
+!!! error TS2662: Cannot find name 'foo'. Did you mean the static member 'C.foo'?
+        }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/accessInstanceMemberFromStaticMethod01.js b/tests/baselines/reference/accessInstanceMemberFromStaticMethod01.js
new file mode 100644
index 0000000000..763be0568d
--- /dev/null
+++ b/tests/baselines/reference/accessInstanceMemberFromStaticMethod01.js
@@ -0,0 +1,18 @@
+//// [accessInstanceMemberFromStaticMethod01.ts]
+class C {
+    static foo: string;
+
+    bar() {
+        let k = foo;
+    }
+}
+
+//// [accessInstanceMemberFromStaticMethod01.js]
+var C = (function () {
+    function C() {
+    }
+    C.prototype.bar = function () {
+        var k = foo;
+    };
+    return C;
+}());
diff --git a/tests/baselines/reference/accessStaticMemberFromInstanceMethod01.errors.txt b/tests/baselines/reference/accessStaticMemberFromInstanceMethod01.errors.txt
new file mode 100644
index 0000000000..612a89a104
--- /dev/null
+++ b/tests/baselines/reference/accessStaticMemberFromInstanceMethod01.errors.txt
@@ -0,0 +1,13 @@
+tests/cases/compiler/accessStaticMemberFromInstanceMethod01.ts(5,17): error TS2304: Cannot find name 'foo'.
+
+
+==== tests/cases/compiler/accessStaticMemberFromInstanceMethod01.ts (1 errors) ====
+    class C {
+        foo: string;
+    
+        static bar() {
+            let k = foo;
+                    ~~~
+!!! error TS2304: Cannot find name 'foo'.
+        }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/accessStaticMemberFromInstanceMethod01.js b/tests/baselines/reference/accessStaticMemberFromInstanceMethod01.js
new file mode 100644
index 0000000000..fd8ee14b2e
--- /dev/null
+++ b/tests/baselines/reference/accessStaticMemberFromInstanceMethod01.js
@@ -0,0 +1,18 @@
+//// [accessStaticMemberFromInstanceMethod01.ts]
+class C {
+    foo: string;
+
+    static bar() {
+        let k = foo;
+    }
+}
+
+//// [accessStaticMemberFromInstanceMethod01.js]
+var C = (function () {
+    function C() {
+    }
+    C.bar = function () {
+        var k = foo;
+    };
+    return C;
+}());
diff --git a/tests/baselines/reference/aliasAssignments.errors.txt b/tests/baselines/reference/aliasAssignments.errors.txt
index fe13faba58..18ea36c5d0 100644
--- a/tests/baselines/reference/aliasAssignments.errors.txt
+++ b/tests/baselines/reference/aliasAssignments.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/compiler/aliasAssignments_1.ts(3,1): error TS2322: Type 'number' is not assignable to type 'typeof "tests/cases/compiler/aliasAssignments_moduleA"'.
-  Property 'someClass' is missing in type 'Number'.
 tests/cases/compiler/aliasAssignments_1.ts(5,1): error TS2322: Type 'typeof "tests/cases/compiler/aliasAssignments_moduleA"' is not assignable to type 'number'.
 
 
@@ -9,7 +8,6 @@ tests/cases/compiler/aliasAssignments_1.ts(5,1): error TS2322: Type 'typeof "tes
     x = 1; // Should be error
     ~
 !!! error TS2322: Type 'number' is not assignable to type 'typeof "tests/cases/compiler/aliasAssignments_moduleA"'.
-!!! error TS2322:   Property 'someClass' is missing in type 'Number'.
     var y = 1;
     y = moduleA; // should be error
     ~
diff --git a/tests/baselines/reference/ambientExternalModuleInAnotherExternalModule.errors.txt b/tests/baselines/reference/ambientExternalModuleInAnotherExternalModule.errors.txt
index 0e508470b1..4edf3bf796 100644
--- a/tests/baselines/reference/ambientExternalModuleInAnotherExternalModule.errors.txt
+++ b/tests/baselines/reference/ambientExternalModuleInAnotherExternalModule.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/ambientExternalModuleInAnotherExternalModule.ts(5,16): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+tests/cases/compiler/ambientExternalModuleInAnotherExternalModule.ts(5,16): error TS2664: Invalid module name in augmentation, module 'ext' cannot be found.
 tests/cases/compiler/ambientExternalModuleInAnotherExternalModule.ts(10,22): error TS2307: Cannot find module 'ext'.
 
 
@@ -9,7 +9,7 @@ tests/cases/compiler/ambientExternalModuleInAnotherExternalModule.ts(10,22): err
     
     declare module "ext" {
                    ~~~~~
-!!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+!!! error TS2664: Invalid module name in augmentation, module 'ext' cannot be found.
         export class C { }
     }
     
diff --git a/tests/baselines/reference/ambientExternalModuleInsideNonAmbient.errors.txt b/tests/baselines/reference/ambientExternalModuleInsideNonAmbient.errors.txt
index 7e4ac795d0..c892c91bfd 100644
--- a/tests/baselines/reference/ambientExternalModuleInsideNonAmbient.errors.txt
+++ b/tests/baselines/reference/ambientExternalModuleInsideNonAmbient.errors.txt
@@ -1,9 +1,12 @@
+tests/cases/conformance/ambient/ambientExternalModuleInsideNonAmbient.ts(2,5): error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
 tests/cases/conformance/ambient/ambientExternalModuleInsideNonAmbient.ts(2,27): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 
 
-==== tests/cases/conformance/ambient/ambientExternalModuleInsideNonAmbient.ts (1 errors) ====
+==== tests/cases/conformance/ambient/ambientExternalModuleInsideNonAmbient.ts (2 errors) ====
     module M {
         export declare module "M" { }
+        ~~~~~~
+!!! error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
                               ~~~
 !!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/ambientExternalModuleInsideNonAmbientExternalModule.errors.txt b/tests/baselines/reference/ambientExternalModuleInsideNonAmbientExternalModule.errors.txt
index e5905aaaf8..1599069e67 100644
--- a/tests/baselines/reference/ambientExternalModuleInsideNonAmbientExternalModule.errors.txt
+++ b/tests/baselines/reference/ambientExternalModuleInsideNonAmbientExternalModule.errors.txt
@@ -1,7 +1,10 @@
-tests/cases/conformance/ambient/ambientExternalModuleInsideNonAmbientExternalModule.ts(1,23): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+tests/cases/conformance/ambient/ambientExternalModuleInsideNonAmbientExternalModule.ts(1,1): error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
+tests/cases/conformance/ambient/ambientExternalModuleInsideNonAmbientExternalModule.ts(1,23): error TS2664: Invalid module name in augmentation, module 'M' cannot be found.
 
 
-==== tests/cases/conformance/ambient/ambientExternalModuleInsideNonAmbientExternalModule.ts (1 errors) ====
+==== tests/cases/conformance/ambient/ambientExternalModuleInsideNonAmbientExternalModule.ts (2 errors) ====
     export declare module "M" { }
+    ~~~~~~
+!!! error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
                           ~~~
-!!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
\ No newline at end of file
+!!! error TS2664: Invalid module name in augmentation, module 'M' cannot be found.
\ No newline at end of file
diff --git a/tests/baselines/reference/argumentsBindsToFunctionScopeArgumentList.errors.txt b/tests/baselines/reference/argumentsBindsToFunctionScopeArgumentList.errors.txt
index 812bbe15da..89ef8ded91 100644
--- a/tests/baselines/reference/argumentsBindsToFunctionScopeArgumentList.errors.txt
+++ b/tests/baselines/reference/argumentsBindsToFunctionScopeArgumentList.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/compiler/argumentsBindsToFunctionScopeArgumentList.ts(3,5): error TS2322: Type 'number' is not assignable to type 'IArguments'.
-  Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/argumentsBindsToFunctionScopeArgumentList.ts (1 errors) ====
@@ -8,5 +7,4 @@ tests/cases/compiler/argumentsBindsToFunctionScopeArgumentList.ts(3,5): error TS
         arguments = 10;  /// This shouldnt be of type number and result in error.
         ~~~~~~~~~
 !!! error TS2322: Type 'number' is not assignable to type 'IArguments'.
-!!! error TS2322:   Property 'length' is missing in type 'Number'.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/arrayAssignmentTest1.errors.txt b/tests/baselines/reference/arrayAssignmentTest1.errors.txt
index d3a7fafed0..3cce5658c1 100644
--- a/tests/baselines/reference/arrayAssignmentTest1.errors.txt
+++ b/tests/baselines/reference/arrayAssignmentTest1.errors.txt
@@ -26,10 +26,13 @@ tests/cases/compiler/arrayAssignmentTest1.ts(70,1): error TS2322: Type 'C3[]' is
     Property 'C2M1' is missing in type 'C3'.
 tests/cases/compiler/arrayAssignmentTest1.ts(75,1): error TS2322: Type 'C2[]' is not assignable to type 'C3[]'.
   Type 'C2' is not assignable to type 'C3'.
+    Property 'CM3M1' is missing in type 'C2'.
 tests/cases/compiler/arrayAssignmentTest1.ts(76,1): error TS2322: Type 'C1[]' is not assignable to type 'C3[]'.
   Type 'C1' is not assignable to type 'C3'.
+    Property 'CM3M1' is missing in type 'C1'.
 tests/cases/compiler/arrayAssignmentTest1.ts(77,1): error TS2322: Type 'I1[]' is not assignable to type 'C3[]'.
   Type 'I1' is not assignable to type 'C3'.
+    Property 'CM3M1' is missing in type 'I1'.
 tests/cases/compiler/arrayAssignmentTest1.ts(79,1): error TS2322: Type '() => C1' is not assignable to type 'any[]'.
   Property 'push' is missing in type '() => C1'.
 tests/cases/compiler/arrayAssignmentTest1.ts(80,1): error TS2322: Type '{ one: number; }' is not assignable to type 'any[]'.
@@ -159,14 +162,17 @@ tests/cases/compiler/arrayAssignmentTest1.ts(85,1): error TS2322: Type 'I1' is n
     ~~~~~~
 !!! error TS2322: Type 'C2[]' is not assignable to type 'C3[]'.
 !!! error TS2322:   Type 'C2' is not assignable to type 'C3'.
+!!! error TS2322:     Property 'CM3M1' is missing in type 'C2'.
     arr_c3 = arr_c1_2; // should be an error - is
     ~~~~~~
 !!! error TS2322: Type 'C1[]' is not assignable to type 'C3[]'.
 !!! error TS2322:   Type 'C1' is not assignable to type 'C3'.
+!!! error TS2322:     Property 'CM3M1' is missing in type 'C1'.
     arr_c3 = arr_i1_2; // should be an error - is
     ~~~~~~
 !!! error TS2322: Type 'I1[]' is not assignable to type 'C3[]'.
 !!! error TS2322:   Type 'I1' is not assignable to type 'C3'.
+!!! error TS2322:     Property 'CM3M1' is missing in type 'I1'.
     
     arr_any = f1; // should be an error - is
     ~~~~~~~
diff --git a/tests/baselines/reference/arrayLiterals3.errors.txt b/tests/baselines/reference/arrayLiterals3.errors.txt
index 637fb3e3bc..5409075a55 100644
--- a/tests/baselines/reference/arrayLiterals3.errors.txt
+++ b/tests/baselines/reference/arrayLiterals3.errors.txt
@@ -18,7 +18,6 @@ tests/cases/conformance/expressions/arrayLiterals/arrayLiterals3.ts(34,5): error
       Types of parameters 'items' and 'items' are incompatible.
         Type 'number | string' is not assignable to type 'Number'.
           Type 'string' is not assignable to type 'Number'.
-            Property 'toFixed' is missing in type 'String'.
 
 
 ==== tests/cases/conformance/expressions/arrayLiterals/arrayLiterals3.ts (6 errors) ====
@@ -82,5 +81,4 @@ tests/cases/conformance/expressions/arrayLiterals/arrayLiterals3.ts(34,5): error
 !!! error TS2322:       Types of parameters 'items' and 'items' are incompatible.
 !!! error TS2322:         Type 'number | string' is not assignable to type 'Number'.
 !!! error TS2322:           Type 'string' is not assignable to type 'Number'.
-!!! error TS2322:             Property 'toFixed' is missing in type 'String'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/arraySigChecking.errors.txt b/tests/baselines/reference/arraySigChecking.errors.txt
index b70b659773..1968957363 100644
--- a/tests/baselines/reference/arraySigChecking.errors.txt
+++ b/tests/baselines/reference/arraySigChecking.errors.txt
@@ -4,7 +4,6 @@ tests/cases/compiler/arraySigChecking.ts(18,5): error TS2322: Type 'void[]' is n
 tests/cases/compiler/arraySigChecking.ts(22,1): error TS2322: Type 'number[][]' is not assignable to type 'number[][][]'.
   Type 'number[]' is not assignable to type 'number[][]'.
     Type 'number' is not assignable to type 'number[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/arraySigChecking.ts (3 errors) ====
@@ -39,7 +38,6 @@ tests/cases/compiler/arraySigChecking.ts(22,1): error TS2322: Type 'number[][]'
 !!! error TS2322: Type 'number[][]' is not assignable to type 'number[][][]'.
 !!! error TS2322:   Type 'number[]' is not assignable to type 'number[][]'.
 !!! error TS2322:     Type 'number' is not assignable to type 'number[]'.
-!!! error TS2322:       Property 'length' is missing in type 'Number'.
     
     function isEmpty(l: { length: number }) {
         return l.length === 0;
diff --git a/tests/baselines/reference/arrayTypeOfTypeOf.errors.txt b/tests/baselines/reference/arrayTypeOfTypeOf.errors.txt
index 41446dfcea..1c37f04be7 100644
--- a/tests/baselines/reference/arrayTypeOfTypeOf.errors.txt
+++ b/tests/baselines/reference/arrayTypeOfTypeOf.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/conformance/types/specifyingTypes/typeLiterals/arrayTypeOfTypeOf.ts(6,5): error TS2322: Type 'number' is not assignable to type 'ArrayConstructor'.
-  Property 'isArray' is missing in type 'Number'.
 tests/cases/conformance/types/specifyingTypes/typeLiterals/arrayTypeOfTypeOf.ts(6,22): error TS1005: '=' expected.
 tests/cases/conformance/types/specifyingTypes/typeLiterals/arrayTypeOfTypeOf.ts(6,30): error TS1109: Expression expected.
 tests/cases/conformance/types/specifyingTypes/typeLiterals/arrayTypeOfTypeOf.ts(7,5): error TS2322: Type 'number' is not assignable to type 'ArrayConstructor'.
@@ -16,7 +15,6 @@ tests/cases/conformance/types/specifyingTypes/typeLiterals/arrayTypeOfTypeOf.ts(
     var xs3: typeof Array<number>;
         ~~~
 !!! error TS2322: Type 'number' is not assignable to type 'ArrayConstructor'.
-!!! error TS2322:   Property 'isArray' is missing in type 'Number'.
                          ~
 !!! error TS1005: '=' expected.
                                  ~
diff --git a/tests/baselines/reference/assignmentCompat1.errors.txt b/tests/baselines/reference/assignmentCompat1.errors.txt
index 7539af9288..0936c532ab 100644
--- a/tests/baselines/reference/assignmentCompat1.errors.txt
+++ b/tests/baselines/reference/assignmentCompat1.errors.txt
@@ -3,9 +3,7 @@ tests/cases/compiler/assignmentCompat1.ts(4,1): error TS2322: Type '{ [index: st
 tests/cases/compiler/assignmentCompat1.ts(6,1): error TS2322: Type '{ [index: number]: any; }' is not assignable to type '{ one: number; }'.
   Property 'one' is missing in type '{ [index: number]: any; }'.
 tests/cases/compiler/assignmentCompat1.ts(8,1): error TS2322: Type 'string' is not assignable to type '{ [index: string]: any; }'.
-  Index signature is missing in type 'String'.
 tests/cases/compiler/assignmentCompat1.ts(10,1): error TS2322: Type 'boolean' is not assignable to type '{ [index: number]: any; }'.
-  Index signature is missing in type 'Boolean'.
 
 
 ==== tests/cases/compiler/assignmentCompat1.ts (4 errors) ====
@@ -25,11 +23,9 @@ tests/cases/compiler/assignmentCompat1.ts(10,1): error TS2322: Type 'boolean' is
     y = "foo"; // Error
     ~
 !!! error TS2322: Type 'string' is not assignable to type '{ [index: string]: any; }'.
-!!! error TS2322:   Index signature is missing in type 'String'.
     z = "foo"; // OK, string has numeric indexer
     z = false; // Error
     ~
 !!! error TS2322: Type 'boolean' is not assignable to type '{ [index: number]: any; }'.
-!!! error TS2322:   Index signature is missing in type 'Boolean'.
     
     
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatWithCallSignatures4.errors.txt b/tests/baselines/reference/assignmentCompatWithCallSignatures4.errors.txt
index e00d1eea04..a75b5fafac 100644
--- a/tests/baselines/reference/assignmentCompatWithCallSignatures4.errors.txt
+++ b/tests/baselines/reference/assignmentCompatWithCallSignatures4.errors.txt
@@ -8,6 +8,10 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures4.ts(53,9): error TS2322: Type '(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type '<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U'.
   Types of parameters 'y' and 'y' are incompatible.
     Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
+      Types of parameters 'arg2' and 'arg2' are incompatible.
+        Type 'Base' is not assignable to type '{ foo: number; }'.
+          Types of property 'foo' are incompatible.
+            Type 'string' is not assignable to type 'number'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures4.ts (2 errors) ====
@@ -76,6 +80,10 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322: Type '(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type '<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U'.
 !!! error TS2322:   Types of parameters 'y' and 'y' are incompatible.
 !!! error TS2322:     Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
+!!! error TS2322:       Types of parameters 'arg2' and 'arg2' are incompatible.
+!!! error TS2322:         Type 'Base' is not assignable to type '{ foo: number; }'.
+!!! error TS2322:           Types of property 'foo' are incompatible.
+!!! error TS2322:             Type 'string' is not assignable to type 'number'.
     
             
             var b10: <T extends Derived>(...x: T[]) => T; 
diff --git a/tests/baselines/reference/assignmentCompatWithConstructSignatures4.errors.txt b/tests/baselines/reference/assignmentCompatWithConstructSignatures4.errors.txt
index 6cd40f6c8c..da9ffba1ee 100644
--- a/tests/baselines/reference/assignmentCompatWithConstructSignatures4.errors.txt
+++ b/tests/baselines/reference/assignmentCompatWithConstructSignatures4.errors.txt
@@ -8,6 +8,10 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(53,9): error TS2322: Type 'new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type 'new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U'.
   Types of parameters 'y' and 'y' are incompatible.
     Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
+      Types of parameters 'arg2' and 'arg2' are incompatible.
+        Type 'Base' is not assignable to type '{ foo: number; }'.
+          Types of property 'foo' are incompatible.
+            Type 'string' is not assignable to type 'number'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(77,9): error TS2322: Type 'new <T>(x: (a: T) => T) => T[]' is not assignable to type '{ new (x: { new (a: number): number; new (a?: number): number; }): number[]; new (x: { new (a: boolean): boolean; new (a?: boolean): boolean; }): boolean[]; }'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '(a: any) => any' is not assignable to type '{ new (a: number): number; new (a?: number): number; }'.
@@ -15,6 +19,7 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(78,9): error TS2322: Type '{ new (x: { new (a: number): number; new (a?: number): number; }): number[]; new (x: { new (a: boolean): boolean; new (a?: boolean): boolean; }): boolean[]; }' is not assignable to type 'new <T>(x: (a: T) => T) => T[]'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '{ new (a: number): number; new (a?: number): number; }' is not assignable to type '(a: any) => any'.
+      Type '{ new (a: number): number; new (a?: number): number; }' provides no match for the signature '(a: any): any'
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(81,9): error TS2322: Type 'new <T>(x: (a: T) => T) => any[]' is not assignable to type '{ new (x: { new <T extends Derived>(a: T): T; new <T extends Base>(a: T): T; }): any[]; new (x: { new <T extends Derived2>(a: T): T; new <T extends Base>(a: T): T; }): any[]; }'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '(a: any) => any' is not assignable to type '{ new <T extends Derived>(a: T): T; new <T extends Base>(a: T): T; }'.
@@ -22,6 +27,7 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(82,9): error TS2322: Type '{ new (x: { new <T extends Derived>(a: T): T; new <T extends Base>(a: T): T; }): any[]; new (x: { new <T extends Derived2>(a: T): T; new <T extends Base>(a: T): T; }): any[]; }' is not assignable to type 'new <T>(x: (a: T) => T) => any[]'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '{ new <T extends Derived>(a: T): T; new <T extends Base>(a: T): T; }' is not assignable to type '(a: any) => any'.
+      Type '{ new <T extends Derived>(a: T): T; new <T extends Base>(a: T): T; }' provides no match for the signature '(a: any): any'
 
 
 ==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts (6 errors) ====
@@ -90,6 +96,10 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322: Type 'new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type 'new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U'.
 !!! error TS2322:   Types of parameters 'y' and 'y' are incompatible.
 !!! error TS2322:     Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
+!!! error TS2322:       Types of parameters 'arg2' and 'arg2' are incompatible.
+!!! error TS2322:         Type 'Base' is not assignable to type '{ foo: number; }'.
+!!! error TS2322:           Types of property 'foo' are incompatible.
+!!! error TS2322:             Type 'string' is not assignable to type 'number'.
     
             
             var b10: new <T extends Derived>(...x: T[]) => T; 
@@ -124,6 +134,7 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322: Type '{ new (x: { new (a: number): number; new (a?: number): number; }): number[]; new (x: { new (a: boolean): boolean; new (a?: boolean): boolean; }): boolean[]; }' is not assignable to type 'new <T>(x: (a: T) => T) => T[]'.
 !!! error TS2322:   Types of parameters 'x' and 'x' are incompatible.
 !!! error TS2322:     Type '{ new (a: number): number; new (a?: number): number; }' is not assignable to type '(a: any) => any'.
+!!! error TS2322:       Type '{ new (a: number): number; new (a?: number): number; }' provides no match for the signature '(a: any): any'
     
             var b17: new <T>(x: (a: T) => T) => any[];
             a17 = b17; // error
@@ -137,6 +148,7 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322: Type '{ new (x: { new <T extends Derived>(a: T): T; new <T extends Base>(a: T): T; }): any[]; new (x: { new <T extends Derived2>(a: T): T; new <T extends Base>(a: T): T; }): any[]; }' is not assignable to type 'new <T>(x: (a: T) => T) => any[]'.
 !!! error TS2322:   Types of parameters 'x' and 'x' are incompatible.
 !!! error TS2322:     Type '{ new <T extends Derived>(a: T): T; new <T extends Base>(a: T): T; }' is not assignable to type '(a: any) => any'.
+!!! error TS2322:       Type '{ new <T extends Derived>(a: T): T; new <T extends Base>(a: T): T; }' provides no match for the signature '(a: any): any'
         }
     
         module WithGenericSignaturesInBaseType {
diff --git a/tests/baselines/reference/assignmentCompatability16.errors.txt b/tests/baselines/reference/assignmentCompatability16.errors.txt
index 266d72b323..71a93f11b3 100644
--- a/tests/baselines/reference/assignmentCompatability16.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability16.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability16.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: any[]; }'.
   Types of property 'one' are incompatible.
     Type 'number' is not assignable to type 'any[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/assignmentCompatability16.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability16.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: any[]; }'.
 !!! error TS2322:   Types of property 'one' are incompatible.
-!!! error TS2322:     Type 'number' is not assignable to type 'any[]'.
-!!! error TS2322:       Property 'length' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2322:     Type 'number' is not assignable to type 'any[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability17.errors.txt b/tests/baselines/reference/assignmentCompatability17.errors.txt
index b37f39d082..a87bcff2e9 100644
--- a/tests/baselines/reference/assignmentCompatability17.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability17.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability17.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ two: any[]; }'.
   Types of property 'two' are incompatible.
     Type 'string' is not assignable to type 'any[]'.
-      Property 'push' is missing in type 'String'.
 
 
 ==== tests/cases/compiler/assignmentCompatability17.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability17.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ two: any[]; }'.
 !!! error TS2322:   Types of property 'two' are incompatible.
-!!! error TS2322:     Type 'string' is not assignable to type 'any[]'.
-!!! error TS2322:       Property 'push' is missing in type 'String'.
\ No newline at end of file
+!!! error TS2322:     Type 'string' is not assignable to type 'any[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability18.errors.txt b/tests/baselines/reference/assignmentCompatability18.errors.txt
index 2be4a03757..8ab5e5dcd0 100644
--- a/tests/baselines/reference/assignmentCompatability18.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability18.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability18.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: number[]; }'.
   Types of property 'one' are incompatible.
     Type 'number' is not assignable to type 'number[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/assignmentCompatability18.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability18.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: number[]; }'.
 !!! error TS2322:   Types of property 'one' are incompatible.
-!!! error TS2322:     Type 'number' is not assignable to type 'number[]'.
-!!! error TS2322:       Property 'length' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2322:     Type 'number' is not assignable to type 'number[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability19.errors.txt b/tests/baselines/reference/assignmentCompatability19.errors.txt
index ae97af6aa7..e84e665cef 100644
--- a/tests/baselines/reference/assignmentCompatability19.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability19.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability19.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ two: number[]; }'.
   Types of property 'two' are incompatible.
     Type 'string' is not assignable to type 'number[]'.
-      Property 'push' is missing in type 'String'.
 
 
 ==== tests/cases/compiler/assignmentCompatability19.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability19.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ two: number[]; }'.
 !!! error TS2322:   Types of property 'two' are incompatible.
-!!! error TS2322:     Type 'string' is not assignable to type 'number[]'.
-!!! error TS2322:       Property 'push' is missing in type 'String'.
\ No newline at end of file
+!!! error TS2322:     Type 'string' is not assignable to type 'number[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability20.errors.txt b/tests/baselines/reference/assignmentCompatability20.errors.txt
index 750310ac5c..2e67a2a203 100644
--- a/tests/baselines/reference/assignmentCompatability20.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability20.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability20.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: string[]; }'.
   Types of property 'one' are incompatible.
     Type 'number' is not assignable to type 'string[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/assignmentCompatability20.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability20.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: string[]; }'.
 !!! error TS2322:   Types of property 'one' are incompatible.
-!!! error TS2322:     Type 'number' is not assignable to type 'string[]'.
-!!! error TS2322:       Property 'length' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2322:     Type 'number' is not assignable to type 'string[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability21.errors.txt b/tests/baselines/reference/assignmentCompatability21.errors.txt
index 8da52fe42c..44e24e7d0b 100644
--- a/tests/baselines/reference/assignmentCompatability21.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability21.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability21.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ two: string[]; }'.
   Types of property 'two' are incompatible.
     Type 'string' is not assignable to type 'string[]'.
-      Property 'push' is missing in type 'String'.
 
 
 ==== tests/cases/compiler/assignmentCompatability21.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability21.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ two: string[]; }'.
 !!! error TS2322:   Types of property 'two' are incompatible.
-!!! error TS2322:     Type 'string' is not assignable to type 'string[]'.
-!!! error TS2322:       Property 'push' is missing in type 'String'.
\ No newline at end of file
+!!! error TS2322:     Type 'string' is not assignable to type 'string[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability22.errors.txt b/tests/baselines/reference/assignmentCompatability22.errors.txt
index f0799a92f5..cb42a7abae 100644
--- a/tests/baselines/reference/assignmentCompatability22.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability22.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability22.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: boolean[]; }'.
   Types of property 'one' are incompatible.
     Type 'number' is not assignable to type 'boolean[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/assignmentCompatability22.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability22.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: boolean[]; }'.
 !!! error TS2322:   Types of property 'one' are incompatible.
-!!! error TS2322:     Type 'number' is not assignable to type 'boolean[]'.
-!!! error TS2322:       Property 'length' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2322:     Type 'number' is not assignable to type 'boolean[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability23.errors.txt b/tests/baselines/reference/assignmentCompatability23.errors.txt
index a005eaa02d..7b54e8559e 100644
--- a/tests/baselines/reference/assignmentCompatability23.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability23.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability23.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ two: boolean[]; }'.
   Types of property 'two' are incompatible.
     Type 'string' is not assignable to type 'boolean[]'.
-      Property 'push' is missing in type 'String'.
 
 
 ==== tests/cases/compiler/assignmentCompatability23.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability23.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ two: boolean[]; }'.
 !!! error TS2322:   Types of property 'two' are incompatible.
-!!! error TS2322:     Type 'string' is not assignable to type 'boolean[]'.
-!!! error TS2322:       Property 'push' is missing in type 'String'.
\ No newline at end of file
+!!! error TS2322:     Type 'string' is not assignable to type 'boolean[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability29.errors.txt b/tests/baselines/reference/assignmentCompatability29.errors.txt
index 194ae4ab67..9ba5c35d52 100644
--- a/tests/baselines/reference/assignmentCompatability29.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability29.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability29.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: any[]; }'.
   Types of property 'one' are incompatible.
     Type 'number' is not assignable to type 'any[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/assignmentCompatability29.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability29.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: any[]; }'.
 !!! error TS2322:   Types of property 'one' are incompatible.
-!!! error TS2322:     Type 'number' is not assignable to type 'any[]'.
-!!! error TS2322:       Property 'length' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2322:     Type 'number' is not assignable to type 'any[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability30.errors.txt b/tests/baselines/reference/assignmentCompatability30.errors.txt
index b025705517..43f7f3f9c0 100644
--- a/tests/baselines/reference/assignmentCompatability30.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability30.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability30.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: number[]; }'.
   Types of property 'one' are incompatible.
     Type 'number' is not assignable to type 'number[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/assignmentCompatability30.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability30.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: number[]; }'.
 !!! error TS2322:   Types of property 'one' are incompatible.
-!!! error TS2322:     Type 'number' is not assignable to type 'number[]'.
-!!! error TS2322:       Property 'length' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2322:     Type 'number' is not assignable to type 'number[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability31.errors.txt b/tests/baselines/reference/assignmentCompatability31.errors.txt
index 8e19905eba..8874ebf06a 100644
--- a/tests/baselines/reference/assignmentCompatability31.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability31.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability31.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: string[]; }'.
   Types of property 'one' are incompatible.
     Type 'number' is not assignable to type 'string[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/assignmentCompatability31.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability31.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: string[]; }'.
 !!! error TS2322:   Types of property 'one' are incompatible.
-!!! error TS2322:     Type 'number' is not assignable to type 'string[]'.
-!!! error TS2322:       Property 'length' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2322:     Type 'number' is not assignable to type 'string[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability32.errors.txt b/tests/baselines/reference/assignmentCompatability32.errors.txt
index 6d6321f5e5..00164a48fd 100644
--- a/tests/baselines/reference/assignmentCompatability32.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability32.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/assignmentCompatability32.ts(9,1): error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: boolean[]; }'.
   Types of property 'one' are incompatible.
     Type 'number' is not assignable to type 'boolean[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/assignmentCompatability32.ts (1 errors) ====
@@ -17,5 +16,4 @@ tests/cases/compiler/assignmentCompatability32.ts(9,1): error TS2322: Type 'inte
     ~~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type 'interfaceWithPublicAndOptional<number, string>' is not assignable to type '{ one: boolean[]; }'.
 !!! error TS2322:   Types of property 'one' are incompatible.
-!!! error TS2322:     Type 'number' is not assignable to type 'boolean[]'.
-!!! error TS2322:       Property 'length' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2322:     Type 'number' is not assignable to type 'boolean[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatability_checking-apply-member-off-of-function-interface.errors.txt b/tests/baselines/reference/assignmentCompatability_checking-apply-member-off-of-function-interface.errors.txt
index e5db4f9ab9..33a2269f74 100644
--- a/tests/baselines/reference/assignmentCompatability_checking-apply-member-off-of-function-interface.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability_checking-apply-member-off-of-function-interface.errors.txt
@@ -1,9 +1,7 @@
 tests/cases/compiler/assignmentCompatability_checking-apply-member-off-of-function-interface.ts(10,1): error TS2322: Type 'string' is not assignable to type 'Applicable'.
-  Property 'apply' is missing in type 'String'.
 tests/cases/compiler/assignmentCompatability_checking-apply-member-off-of-function-interface.ts(11,1): error TS2322: Type 'string[]' is not assignable to type 'Applicable'.
   Property 'apply' is missing in type 'string[]'.
 tests/cases/compiler/assignmentCompatability_checking-apply-member-off-of-function-interface.ts(12,1): error TS2322: Type 'number' is not assignable to type 'Applicable'.
-  Property 'apply' is missing in type 'Number'.
 tests/cases/compiler/assignmentCompatability_checking-apply-member-off-of-function-interface.ts(13,1): error TS2322: Type '{}' is not assignable to type 'Applicable'.
   Property 'apply' is missing in type '{}'.
 tests/cases/compiler/assignmentCompatability_checking-apply-member-off-of-function-interface.ts(22,4): error TS2345: Argument of type 'string' is not assignable to parameter of type 'Applicable'.
@@ -26,7 +24,6 @@ tests/cases/compiler/assignmentCompatability_checking-apply-member-off-of-functi
     x = '';
     ~
 !!! error TS2322: Type 'string' is not assignable to type 'Applicable'.
-!!! error TS2322:   Property 'apply' is missing in type 'String'.
     x = [''];
     ~
 !!! error TS2322: Type 'string[]' is not assignable to type 'Applicable'.
@@ -34,7 +31,6 @@ tests/cases/compiler/assignmentCompatability_checking-apply-member-off-of-functi
     x = 4;
     ~
 !!! error TS2322: Type 'number' is not assignable to type 'Applicable'.
-!!! error TS2322:   Property 'apply' is missing in type 'Number'.
     x = {};
     ~
 !!! error TS2322: Type '{}' is not assignable to type 'Applicable'.
diff --git a/tests/baselines/reference/assignmentCompatability_checking-call-member-off-of-function-interface.errors.txt b/tests/baselines/reference/assignmentCompatability_checking-call-member-off-of-function-interface.errors.txt
index f3ff6f1b79..1651e5082e 100644
--- a/tests/baselines/reference/assignmentCompatability_checking-call-member-off-of-function-interface.errors.txt
+++ b/tests/baselines/reference/assignmentCompatability_checking-call-member-off-of-function-interface.errors.txt
@@ -1,9 +1,7 @@
 tests/cases/compiler/assignmentCompatability_checking-call-member-off-of-function-interface.ts(10,1): error TS2322: Type 'string' is not assignable to type 'Callable'.
-  Property 'call' is missing in type 'String'.
 tests/cases/compiler/assignmentCompatability_checking-call-member-off-of-function-interface.ts(11,1): error TS2322: Type 'string[]' is not assignable to type 'Callable'.
   Property 'call' is missing in type 'string[]'.
 tests/cases/compiler/assignmentCompatability_checking-call-member-off-of-function-interface.ts(12,1): error TS2322: Type 'number' is not assignable to type 'Callable'.
-  Property 'call' is missing in type 'Number'.
 tests/cases/compiler/assignmentCompatability_checking-call-member-off-of-function-interface.ts(13,1): error TS2322: Type '{}' is not assignable to type 'Callable'.
   Property 'call' is missing in type '{}'.
 tests/cases/compiler/assignmentCompatability_checking-call-member-off-of-function-interface.ts(22,4): error TS2345: Argument of type 'string' is not assignable to parameter of type 'Callable'.
@@ -26,7 +24,6 @@ tests/cases/compiler/assignmentCompatability_checking-call-member-off-of-functio
     x = '';
     ~
 !!! error TS2322: Type 'string' is not assignable to type 'Callable'.
-!!! error TS2322:   Property 'call' is missing in type 'String'.
     x = [''];
     ~
 !!! error TS2322: Type 'string[]' is not assignable to type 'Callable'.
@@ -34,7 +31,6 @@ tests/cases/compiler/assignmentCompatability_checking-call-member-off-of-functio
     x = 4;
     ~
 !!! error TS2322: Type 'number' is not assignable to type 'Callable'.
-!!! error TS2322:   Property 'call' is missing in type 'Number'.
     x = {};
     ~
 !!! error TS2322: Type '{}' is not assignable to type 'Callable'.
diff --git a/tests/baselines/reference/booleanAssignment.errors.txt b/tests/baselines/reference/booleanAssignment.errors.txt
index 454bd7ef70..15b506d3df 100644
--- a/tests/baselines/reference/booleanAssignment.errors.txt
+++ b/tests/baselines/reference/booleanAssignment.errors.txt
@@ -1,11 +1,5 @@
 tests/cases/compiler/booleanAssignment.ts(2,1): error TS2322: Type 'number' is not assignable to type 'Boolean'.
-  Types of property 'valueOf' are incompatible.
-    Type '() => number' is not assignable to type '() => boolean'.
-      Type 'number' is not assignable to type 'boolean'.
 tests/cases/compiler/booleanAssignment.ts(3,1): error TS2322: Type 'string' is not assignable to type 'Boolean'.
-  Types of property 'valueOf' are incompatible.
-    Type '() => string' is not assignable to type '() => boolean'.
-      Type 'string' is not assignable to type 'boolean'.
 tests/cases/compiler/booleanAssignment.ts(4,1): error TS2322: Type '{}' is not assignable to type 'Boolean'.
   Types of property 'valueOf' are incompatible.
     Type '() => Object' is not assignable to type '() => boolean'.
@@ -17,15 +11,9 @@ tests/cases/compiler/booleanAssignment.ts(4,1): error TS2322: Type '{}' is not a
     b = 1; // Error
     ~
 !!! error TS2322: Type 'number' is not assignable to type 'Boolean'.
-!!! error TS2322:   Types of property 'valueOf' are incompatible.
-!!! error TS2322:     Type '() => number' is not assignable to type '() => boolean'.
-!!! error TS2322:       Type 'number' is not assignable to type 'boolean'.
     b = "a"; // Error
     ~
 !!! error TS2322: Type 'string' is not assignable to type 'Boolean'.
-!!! error TS2322:   Types of property 'valueOf' are incompatible.
-!!! error TS2322:     Type '() => string' is not assignable to type '() => boolean'.
-!!! error TS2322:       Type 'string' is not assignable to type 'boolean'.
     b = {}; // Error
     ~
 !!! error TS2322: Type '{}' is not assignable to type 'Boolean'.
diff --git a/tests/baselines/reference/capturedLetConstInLoop11.js b/tests/baselines/reference/capturedLetConstInLoop11.js
new file mode 100644
index 0000000000..fa295739d0
--- /dev/null
+++ b/tests/baselines/reference/capturedLetConstInLoop11.js
@@ -0,0 +1,35 @@
+//// [capturedLetConstInLoop11.ts]
+for (;;) {
+    let x = 1;
+    () => x;
+}
+
+function foo() {
+    for (;;) {
+        const a = 0;
+        switch(a) {
+            case 0: return () => a;
+        }
+    }
+}
+
+//// [capturedLetConstInLoop11.js]
+var _loop_1 = function() {
+    var x = 1;
+    (function () { return x; });
+};
+for (;;) {
+    _loop_1();
+}
+function foo() {
+    var _loop_2 = function() {
+        var a = 0;
+        switch (a) {
+            case 0: return { value: function () { return a; } };
+        }
+    };
+    for (;;) {
+        var state_2 = _loop_2();
+        if (typeof state_2 === "object") return state_2.value
+    }
+}
diff --git a/tests/baselines/reference/capturedLetConstInLoop11.symbols b/tests/baselines/reference/capturedLetConstInLoop11.symbols
new file mode 100644
index 0000000000..2e242906b7
--- /dev/null
+++ b/tests/baselines/reference/capturedLetConstInLoop11.symbols
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/capturedLetConstInLoop11.ts ===
+for (;;) {
+    let x = 1;
+>x : Symbol(x, Decl(capturedLetConstInLoop11.ts, 1, 7))
+
+    () => x;
+>x : Symbol(x, Decl(capturedLetConstInLoop11.ts, 1, 7))
+}
+
+function foo() {
+>foo : Symbol(foo, Decl(capturedLetConstInLoop11.ts, 3, 1))
+
+    for (;;) {
+        const a = 0;
+>a : Symbol(a, Decl(capturedLetConstInLoop11.ts, 7, 13))
+
+        switch(a) {
+>a : Symbol(a, Decl(capturedLetConstInLoop11.ts, 7, 13))
+
+            case 0: return () => a;
+>a : Symbol(a, Decl(capturedLetConstInLoop11.ts, 7, 13))
+        }
+    }
+}
diff --git a/tests/baselines/reference/capturedLetConstInLoop11.types b/tests/baselines/reference/capturedLetConstInLoop11.types
new file mode 100644
index 0000000000..93e18f2cb2
--- /dev/null
+++ b/tests/baselines/reference/capturedLetConstInLoop11.types
@@ -0,0 +1,29 @@
+=== tests/cases/compiler/capturedLetConstInLoop11.ts ===
+for (;;) {
+    let x = 1;
+>x : number
+>1 : number
+
+    () => x;
+>() => x : () => number
+>x : number
+}
+
+function foo() {
+>foo : () => () => number
+
+    for (;;) {
+        const a = 0;
+>a : number
+>0 : number
+
+        switch(a) {
+>a : number
+
+            case 0: return () => a;
+>0 : number
+>() => a : () => number
+>a : number
+        }
+    }
+}
diff --git a/tests/baselines/reference/capturedLetConstInLoop11_ES6.js b/tests/baselines/reference/capturedLetConstInLoop11_ES6.js
new file mode 100644
index 0000000000..49f6e9f521
--- /dev/null
+++ b/tests/baselines/reference/capturedLetConstInLoop11_ES6.js
@@ -0,0 +1,28 @@
+//// [capturedLetConstInLoop11_ES6.ts]
+for (;;) {
+    let x = 1;
+    () => x;
+}
+
+function foo() {
+    for (;;) {
+        const a = 0;
+        switch(a) {
+            case 0: return () => a;
+        }
+    }
+}
+
+//// [capturedLetConstInLoop11_ES6.js]
+for (;;) {
+    let x = 1;
+    (() => x);
+}
+function foo() {
+    for (;;) {
+        const a = 0;
+        switch (a) {
+            case 0: return () => a;
+        }
+    }
+}
diff --git a/tests/baselines/reference/capturedLetConstInLoop11_ES6.symbols b/tests/baselines/reference/capturedLetConstInLoop11_ES6.symbols
new file mode 100644
index 0000000000..6079bf490a
--- /dev/null
+++ b/tests/baselines/reference/capturedLetConstInLoop11_ES6.symbols
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/capturedLetConstInLoop11_ES6.ts ===
+for (;;) {
+    let x = 1;
+>x : Symbol(x, Decl(capturedLetConstInLoop11_ES6.ts, 1, 7))
+
+    () => x;
+>x : Symbol(x, Decl(capturedLetConstInLoop11_ES6.ts, 1, 7))
+}
+
+function foo() {
+>foo : Symbol(foo, Decl(capturedLetConstInLoop11_ES6.ts, 3, 1))
+
+    for (;;) {
+        const a = 0;
+>a : Symbol(a, Decl(capturedLetConstInLoop11_ES6.ts, 7, 13))
+
+        switch(a) {
+>a : Symbol(a, Decl(capturedLetConstInLoop11_ES6.ts, 7, 13))
+
+            case 0: return () => a;
+>a : Symbol(a, Decl(capturedLetConstInLoop11_ES6.ts, 7, 13))
+        }
+    }
+}
diff --git a/tests/baselines/reference/capturedLetConstInLoop11_ES6.types b/tests/baselines/reference/capturedLetConstInLoop11_ES6.types
new file mode 100644
index 0000000000..de75d5d151
--- /dev/null
+++ b/tests/baselines/reference/capturedLetConstInLoop11_ES6.types
@@ -0,0 +1,29 @@
+=== tests/cases/compiler/capturedLetConstInLoop11_ES6.ts ===
+for (;;) {
+    let x = 1;
+>x : number
+>1 : number
+
+    () => x;
+>() => x : () => number
+>x : number
+}
+
+function foo() {
+>foo : () => () => number
+
+    for (;;) {
+        const a = 0;
+>a : number
+>0 : number
+
+        switch(a) {
+>a : number
+
+            case 0: return () => a;
+>0 : number
+>() => a : () => number
+>a : number
+        }
+    }
+}
diff --git a/tests/baselines/reference/compoundAdditionAssignmentLHSCannotBeAssigned.errors.txt b/tests/baselines/reference/compoundAdditionAssignmentLHSCannotBeAssigned.errors.txt
index 535e4eb1a3..6bbebeb6ec 100644
--- a/tests/baselines/reference/compoundAdditionAssignmentLHSCannotBeAssigned.errors.txt
+++ b/tests/baselines/reference/compoundAdditionAssignmentLHSCannotBeAssigned.errors.txt
@@ -2,7 +2,6 @@ tests/cases/conformance/expressions/assignmentOperator/compoundAdditionAssignmen
 tests/cases/conformance/expressions/assignmentOperator/compoundAdditionAssignmentLHSCannotBeAssigned.ts(8,1): error TS2322: Type 'string' is not assignable to type 'number'.
 tests/cases/conformance/expressions/assignmentOperator/compoundAdditionAssignmentLHSCannotBeAssigned.ts(11,1): error TS2322: Type 'string' is not assignable to type 'E'.
 tests/cases/conformance/expressions/assignmentOperator/compoundAdditionAssignmentLHSCannotBeAssigned.ts(14,1): error TS2322: Type 'string' is not assignable to type '{ a: string; }'.
-  Property 'a' is missing in type 'String'.
 tests/cases/conformance/expressions/assignmentOperator/compoundAdditionAssignmentLHSCannotBeAssigned.ts(17,1): error TS2322: Type 'string' is not assignable to type 'void'.
 
 
@@ -29,7 +28,6 @@ tests/cases/conformance/expressions/assignmentOperator/compoundAdditionAssignmen
     x4 += '';
     ~~
 !!! error TS2322: Type 'string' is not assignable to type '{ a: string; }'.
-!!! error TS2322:   Property 'a' is missing in type 'String'.
     
     var x5: void;
     x5 += '';
diff --git a/tests/baselines/reference/constructorReturnsInvalidType.errors.txt b/tests/baselines/reference/constructorReturnsInvalidType.errors.txt
index a8fe1de470..3b9a84fea9 100644
--- a/tests/baselines/reference/constructorReturnsInvalidType.errors.txt
+++ b/tests/baselines/reference/constructorReturnsInvalidType.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/compiler/constructorReturnsInvalidType.ts(3,16): error TS2322: Type 'number' is not assignable to type 'X'.
-  Property 'foo' is missing in type 'Number'.
 tests/cases/compiler/constructorReturnsInvalidType.ts(3,16): error TS2409: Return type of constructor signature must be assignable to the instance type of the class
 
 
@@ -9,7 +8,6 @@ tests/cases/compiler/constructorReturnsInvalidType.ts(3,16): error TS2409: Retur
             return 1;
                    ~
 !!! error TS2322: Type 'number' is not assignable to type 'X'.
-!!! error TS2322:   Property 'foo' is missing in type 'Number'.
                    ~
 !!! error TS2409: Return type of constructor signature must be assignable to the instance type of the class
         }
diff --git a/tests/baselines/reference/constructorWithAssignableReturnExpression.errors.txt b/tests/baselines/reference/constructorWithAssignableReturnExpression.errors.txt
index 1f7d7133bd..421e629c11 100644
--- a/tests/baselines/reference/constructorWithAssignableReturnExpression.errors.txt
+++ b/tests/baselines/reference/constructorWithAssignableReturnExpression.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/conformance/classes/constructorDeclarations/constructorWithAssignableReturnExpression.ts(12,16): error TS2322: Type 'number' is not assignable to type 'D'.
-  Property 'x' is missing in type 'Number'.
 tests/cases/conformance/classes/constructorDeclarations/constructorWithAssignableReturnExpression.ts(12,16): error TS2409: Return type of constructor signature must be assignable to the instance type of the class
 tests/cases/conformance/classes/constructorDeclarations/constructorWithAssignableReturnExpression.ts(26,16): error TS2322: Type '{ x: number; }' is not assignable to type 'F<T>'.
   Types of property 'x' are incompatible.
@@ -22,7 +21,6 @@ tests/cases/conformance/classes/constructorDeclarations/constructorWithAssignabl
             return 1; // error
                    ~
 !!! error TS2322: Type 'number' is not assignable to type 'D'.
-!!! error TS2322:   Property 'x' is missing in type 'Number'.
                    ~
 !!! error TS2409: Return type of constructor signature must be assignable to the instance type of the class
         }
diff --git a/tests/baselines/reference/contextualTyping21.errors.txt b/tests/baselines/reference/contextualTyping21.errors.txt
index 362ead49ad..db6ecd32b9 100644
--- a/tests/baselines/reference/contextualTyping21.errors.txt
+++ b/tests/baselines/reference/contextualTyping21.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/contextualTyping21.ts(1,36): error TS2322: Type '({ id: number; } | number)[]' is not assignable to type '{ id: number; }[]'.
   Type '{ id: number; } | number' is not assignable to type '{ id: number; }'.
     Type 'number' is not assignable to type '{ id: number; }'.
-      Property 'id' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/contextualTyping21.ts (1 errors) ====
@@ -9,5 +8,4 @@ tests/cases/compiler/contextualTyping21.ts(1,36): error TS2322: Type '({ id: num
                                        ~~~
 !!! error TS2322: Type '({ id: number; } | number)[]' is not assignable to type '{ id: number; }[]'.
 !!! error TS2322:   Type '{ id: number; } | number' is not assignable to type '{ id: number; }'.
-!!! error TS2322:     Type 'number' is not assignable to type '{ id: number; }'.
-!!! error TS2322:       Property 'id' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2322:     Type 'number' is not assignable to type '{ id: number; }'.
\ No newline at end of file
diff --git a/tests/baselines/reference/contextualTyping33.errors.txt b/tests/baselines/reference/contextualTyping33.errors.txt
index 4ed0787bde..16c975391a 100644
--- a/tests/baselines/reference/contextualTyping33.errors.txt
+++ b/tests/baselines/reference/contextualTyping33.errors.txt
@@ -1,6 +1,7 @@
 tests/cases/compiler/contextualTyping33.ts(1,66): error TS2345: Argument of type '((() => number) | (() => string))[]' is not assignable to parameter of type '{ (): number; (i: number): number; }[]'.
   Type '(() => number) | (() => string)' is not assignable to type '{ (): number; (i: number): number; }'.
     Type '() => string' is not assignable to type '{ (): number; (i: number): number; }'.
+      Type 'string' is not assignable to type 'number'.
 
 
 ==== tests/cases/compiler/contextualTyping33.ts (1 errors) ====
@@ -8,4 +9,5 @@ tests/cases/compiler/contextualTyping33.ts(1,66): error TS2345: Argument of type
                                                                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2345: Argument of type '((() => number) | (() => string))[]' is not assignable to parameter of type '{ (): number; (i: number): number; }[]'.
 !!! error TS2345:   Type '(() => number) | (() => string)' is not assignable to type '{ (): number; (i: number): number; }'.
-!!! error TS2345:     Type '() => string' is not assignable to type '{ (): number; (i: number): number; }'.
\ No newline at end of file
+!!! error TS2345:     Type '() => string' is not assignable to type '{ (): number; (i: number): number; }'.
+!!! error TS2345:       Type 'string' is not assignable to type 'number'.
\ No newline at end of file
diff --git a/tests/baselines/reference/contextualTypingOfArrayLiterals1.errors.txt b/tests/baselines/reference/contextualTypingOfArrayLiterals1.errors.txt
index a1bfaf5633..698a8e789f 100644
--- a/tests/baselines/reference/contextualTypingOfArrayLiterals1.errors.txt
+++ b/tests/baselines/reference/contextualTypingOfArrayLiterals1.errors.txt
@@ -2,7 +2,6 @@ tests/cases/compiler/contextualTypingOfArrayLiterals1.ts(5,5): error TS2322: Typ
   Index signatures are incompatible.
     Type 'Date | number' is not assignable to type 'Date'.
       Type 'number' is not assignable to type 'Date'.
-        Property 'toDateString' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/contextualTypingOfArrayLiterals1.ts (1 errors) ====
@@ -16,7 +15,6 @@ tests/cases/compiler/contextualTypingOfArrayLiterals1.ts(5,5): error TS2322: Typ
 !!! error TS2322:   Index signatures are incompatible.
 !!! error TS2322:     Type 'Date | number' is not assignable to type 'Date'.
 !!! error TS2322:       Type 'number' is not assignable to type 'Date'.
-!!! error TS2322:         Property 'toDateString' is missing in type 'Number'.
     var r2 = x3[1]; 
     r2.getDate(); 
     
\ No newline at end of file
diff --git a/tests/baselines/reference/contextualTypingOfConditionalExpression2.errors.txt b/tests/baselines/reference/contextualTypingOfConditionalExpression2.errors.txt
index 08fe22c08e..be49b7b524 100644
--- a/tests/baselines/reference/contextualTypingOfConditionalExpression2.errors.txt
+++ b/tests/baselines/reference/contextualTypingOfConditionalExpression2.errors.txt
@@ -2,7 +2,6 @@ tests/cases/compiler/contextualTypingOfConditionalExpression2.ts(11,5): error TS
   Type '(b: number) => void' is not assignable to type '(a: A) => void'.
     Types of parameters 'b' and 'a' are incompatible.
       Type 'number' is not assignable to type 'A'.
-        Property 'foo' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/contextualTypingOfConditionalExpression2.ts (1 errors) ====
@@ -22,5 +21,4 @@ tests/cases/compiler/contextualTypingOfConditionalExpression2.ts(11,5): error TS
 !!! error TS2322:   Type '(b: number) => void' is not assignable to type '(a: A) => void'.
 !!! error TS2322:     Types of parameters 'b' and 'a' are incompatible.
 !!! error TS2322:       Type 'number' is not assignable to type 'A'.
-!!! error TS2322:         Property 'foo' is missing in type 'Number'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/contextualTypingOfGenericFunctionTypedArguments1.errors.txt b/tests/baselines/reference/contextualTypingOfGenericFunctionTypedArguments1.errors.txt
index a11f000901..c7b15e8efe 100644
--- a/tests/baselines/reference/contextualTypingOfGenericFunctionTypedArguments1.errors.txt
+++ b/tests/baselines/reference/contextualTypingOfGenericFunctionTypedArguments1.errors.txt
@@ -1,6 +1,5 @@
 tests/cases/compiler/contextualTypingOfGenericFunctionTypedArguments1.ts(16,32): error TS2345: Argument of type '(x: number) => string' is not assignable to parameter of type '(x: number) => Date'.
   Type 'string' is not assignable to type 'Date'.
-    Property 'toDateString' is missing in type 'String'.
 tests/cases/compiler/contextualTypingOfGenericFunctionTypedArguments1.ts(17,32): error TS2345: Argument of type '(x: number) => string' is not assignable to parameter of type '(x: number) => Date'.
   Type 'string' is not assignable to type 'Date'.
 
@@ -25,7 +24,6 @@ tests/cases/compiler/contextualTypingOfGenericFunctionTypedArguments1.ts(17,32):
                                    ~
 !!! error TS2345: Argument of type '(x: number) => string' is not assignable to parameter of type '(x: number) => Date'.
 !!! error TS2345:   Type 'string' is not assignable to type 'Date'.
-!!! error TS2345:     Property 'toDateString' is missing in type 'String'.
     var r6 = _.forEach<number>(c2, (x) => { return x.toFixed() }); 
                                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2345: Argument of type '(x: number) => string' is not assignable to parameter of type '(x: number) => Date'.
diff --git a/tests/baselines/reference/declarationEmit_UnknownImport.errors.txt b/tests/baselines/reference/declarationEmit_UnknownImport.errors.txt
new file mode 100644
index 0000000000..2ae0b6a160
--- /dev/null
+++ b/tests/baselines/reference/declarationEmit_UnknownImport.errors.txt
@@ -0,0 +1,15 @@
+tests/cases/compiler/declarationEmit_UnknownImport.ts(2,1): error TS2304: Cannot find name 'SomeNonExistingName'.
+tests/cases/compiler/declarationEmit_UnknownImport.ts(2,14): error TS2503: Cannot find namespace 'SomeNonExistingName'.
+tests/cases/compiler/declarationEmit_UnknownImport.ts(2,14): error TS4000: Import declaration 'Foo' is using private name 'SomeNonExistingName'.
+
+
+==== tests/cases/compiler/declarationEmit_UnknownImport.ts (3 errors) ====
+    
+    import Foo = SomeNonExistingName
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2304: Cannot find name 'SomeNonExistingName'.
+                 ~~~~~~~~~~~~~~~~~~~
+!!! error TS2503: Cannot find namespace 'SomeNonExistingName'.
+                 ~~~~~~~~~~~~~~~~~~~
+!!! error TS4000: Import declaration 'Foo' is using private name 'SomeNonExistingName'.
+    export {Foo}
\ No newline at end of file
diff --git a/tests/baselines/reference/declarationEmit_UnknownImport.js b/tests/baselines/reference/declarationEmit_UnknownImport.js
new file mode 100644
index 0000000000..601d2a92c8
--- /dev/null
+++ b/tests/baselines/reference/declarationEmit_UnknownImport.js
@@ -0,0 +1,7 @@
+//// [declarationEmit_UnknownImport.ts]
+
+import Foo = SomeNonExistingName
+export {Foo}
+
+//// [declarationEmit_UnknownImport.js]
+"use strict";
diff --git a/tests/baselines/reference/declarationEmit_UnknownImport2.errors.txt b/tests/baselines/reference/declarationEmit_UnknownImport2.errors.txt
new file mode 100644
index 0000000000..0e0bf6690e
--- /dev/null
+++ b/tests/baselines/reference/declarationEmit_UnknownImport2.errors.txt
@@ -0,0 +1,21 @@
+tests/cases/compiler/declarationEmit_UnknownImport2.ts(2,1): error TS2304: Cannot find name 'From'.
+tests/cases/compiler/declarationEmit_UnknownImport2.ts(2,12): error TS1005: '=' expected.
+tests/cases/compiler/declarationEmit_UnknownImport2.ts(2,12): error TS2503: Cannot find namespace 'From'.
+tests/cases/compiler/declarationEmit_UnknownImport2.ts(2,12): error TS4000: Import declaration 'Foo' is using private name 'From'.
+tests/cases/compiler/declarationEmit_UnknownImport2.ts(2,17): error TS1005: ';' expected.
+
+
+==== tests/cases/compiler/declarationEmit_UnknownImport2.ts (5 errors) ====
+    
+    import Foo From './Foo'; // Syntax error
+    ~~~~~~~~~~~~~~~
+!!! error TS2304: Cannot find name 'From'.
+               ~~~~
+!!! error TS1005: '=' expected.
+               ~~~~
+!!! error TS2503: Cannot find namespace 'From'.
+               ~~~~
+!!! error TS4000: Import declaration 'Foo' is using private name 'From'.
+                    ~~~~~~~
+!!! error TS1005: ';' expected.
+    export default Foo
\ No newline at end of file
diff --git a/tests/baselines/reference/declarationEmit_UnknownImport2.js b/tests/baselines/reference/declarationEmit_UnknownImport2.js
new file mode 100644
index 0000000000..213b4fc736
--- /dev/null
+++ b/tests/baselines/reference/declarationEmit_UnknownImport2.js
@@ -0,0 +1,8 @@
+//// [declarationEmit_UnknownImport2.ts]
+
+import Foo From './Foo'; // Syntax error
+export default Foo
+
+//// [declarationEmit_UnknownImport2.js]
+"use strict";
+'./Foo'; // Syntax error
diff --git a/tests/baselines/reference/destructuringArrayBindingPatternAndAssignment2.errors.txt b/tests/baselines/reference/destructuringArrayBindingPatternAndAssignment2.errors.txt
index 9140528597..3348effe82 100644
--- a/tests/baselines/reference/destructuringArrayBindingPatternAndAssignment2.errors.txt
+++ b/tests/baselines/reference/destructuringArrayBindingPatternAndAssignment2.errors.txt
@@ -5,7 +5,6 @@ tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAss
   Types of property '1' are incompatible.
     Type 'number' is not assignable to type 'boolean'.
 tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(17,6): error TS2322: Type 'string' is not assignable to type 'Number'.
-  Property 'toFixed' is missing in type 'String'.
 tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(22,5): error TS2322: Type 'number[]' is not assignable to type '[number, number]'.
   Property '0' is missing in type 'number[]'.
 tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(23,5): error TS2322: Type 'number[]' is not assignable to type '[string, string]'.
@@ -43,7 +42,6 @@ tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAss
     var [b3 = "string", b4, b5] = bar();  // Error
          ~~
 !!! error TS2322: Type 'string' is not assignable to type 'Number'.
-!!! error TS2322:   Property 'toFixed' is missing in type 'String'.
     
     // V is an array assignment pattern, S is the type Any or an array-like type (section 3.3.2), and, for each assignment element E in V,
     //      S is not a tuple- like type and the numeric index signature type of S is assignable to the target given in E.
diff --git a/tests/baselines/reference/destructuringParameterDeclaration2.errors.txt b/tests/baselines/reference/destructuringParameterDeclaration2.errors.txt
index c8037255a3..8c0781571e 100644
--- a/tests/baselines/reference/destructuringParameterDeclaration2.errors.txt
+++ b/tests/baselines/reference/destructuringParameterDeclaration2.errors.txt
@@ -8,7 +8,6 @@ tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration2.ts(
       Type 'number | string[][] | string' is not assignable to type 'number | string[][]'.
         Type 'string' is not assignable to type 'number | string[][]'.
           Type 'string' is not assignable to type 'string[][]'.
-            Property 'push' is missing in type 'String'.
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration2.ts(16,8): error TS2371: A parameter initializer is only allowed in a function or constructor implementation.
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration2.ts(16,16): error TS2371: A parameter initializer is only allowed in a function or constructor implementation.
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration2.ts(23,14): error TS2345: Argument of type '{ x: string; y: boolean; }' is not assignable to parameter of type '{ x: number; y: any; }'.
@@ -34,7 +33,6 @@ tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration2.ts(
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration2.ts(39,4): error TS2345: Argument of type '[number, number, boolean, boolean]' is not assignable to parameter of type '[any, any, [[any]]]'.
   Types of property '2' are incompatible.
     Type 'boolean' is not assignable to type '[[any]]'.
-      Property '0' is missing in type 'Boolean'.
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration2.ts(40,4): error TS2345: Argument of type '[number, number, [[string]]]' is not assignable to parameter of type '[any, any, [[number]]]'.
   Types of property '2' are incompatible.
     Type '[[string]]' is not assignable to type '[[number]]'.
@@ -78,7 +76,6 @@ tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration2.ts(
 !!! error TS2345:       Type 'number | string[][] | string' is not assignable to type 'number | string[][]'.
 !!! error TS2345:         Type 'string' is not assignable to type 'number | string[][]'.
 !!! error TS2345:           Type 'string' is not assignable to type 'string[][]'.
-!!! error TS2345:             Property 'push' is missing in type 'String'.
     
     
     // If the declaration includes an initializer expression (which is permitted only
@@ -146,7 +143,6 @@ tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration2.ts(
 !!! error TS2345: Argument of type '[number, number, boolean, boolean]' is not assignable to parameter of type '[any, any, [[any]]]'.
 !!! error TS2345:   Types of property '2' are incompatible.
 !!! error TS2345:     Type 'boolean' is not assignable to type '[[any]]'.
-!!! error TS2345:       Property '0' is missing in type 'Boolean'.
     c6([1, 2, [["string"]]]);  // Error, implied type is [any, any, [[number]]]  // Use initializer
        ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2345: Argument of type '[number, number, [[string]]]' is not assignable to parameter of type '[any, any, [[number]]]'.
diff --git a/tests/baselines/reference/destructuringParameterDeclaration4.errors.txt b/tests/baselines/reference/destructuringParameterDeclaration4.errors.txt
index 7e71a2cd75..b08c5b942d 100644
--- a/tests/baselines/reference/destructuringParameterDeclaration4.errors.txt
+++ b/tests/baselines/reference/destructuringParameterDeclaration4.errors.txt
@@ -6,7 +6,6 @@ tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration4.ts(
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration4.ts(22,4): error TS2345: Argument of type '[number, number, string, boolean, boolean]' is not assignable to parameter of type '[any, any, [[any]]]'.
   Types of property '2' are incompatible.
     Type 'string' is not assignable to type '[[any]]'.
-      Property '0' is missing in type 'String'.
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration4.ts(23,4): error TS2345: Argument of type '[number, number]' is not assignable to parameter of type '[any, any, [[any]]]'.
   Property '2' is missing in type '[number, number]'.
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration4.ts(24,4): error TS2345: Argument of type '(number | string)[]' is not assignable to parameter of type 'number[]'.
@@ -53,7 +52,6 @@ tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration4.ts(
 !!! error TS2345: Argument of type '[number, number, string, boolean, boolean]' is not assignable to parameter of type '[any, any, [[any]]]'.
 !!! error TS2345:   Types of property '2' are incompatible.
 !!! error TS2345:     Type 'string' is not assignable to type '[[any]]'.
-!!! error TS2345:       Property '0' is missing in type 'String'.
     a5([1, 2]);                              // Error, parameter type is [any, any, [[any]]]
        ~~~~~~
 !!! error TS2345: Argument of type '[number, number]' is not assignable to parameter of type '[any, any, [[any]]]'.
diff --git a/tests/baselines/reference/destructuringParameterDeclaration5.errors.txt b/tests/baselines/reference/destructuringParameterDeclaration5.errors.txt
index c60e2b75c3..2afb25502c 100644
--- a/tests/baselines/reference/destructuringParameterDeclaration5.errors.txt
+++ b/tests/baselines/reference/destructuringParameterDeclaration5.errors.txt
@@ -1,6 +1,7 @@
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration5.ts(47,4): error TS2345: Argument of type '{ y: Class; }' is not assignable to parameter of type '{ y: D; }'.
   Types of property 'y' are incompatible.
     Type 'Class' is not assignable to type 'D'.
+      Property 'foo' is missing in type 'Class'.
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration5.ts(48,4): error TS2345: Argument of type '{}' is not assignable to parameter of type '{ y: D; }'.
   Property 'y' is missing in type '{}'.
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration5.ts(49,4): error TS2345: Argument of type '{ y: number; }' is not assignable to parameter of type '{ y: D; }'.
@@ -63,6 +64,7 @@ tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration5.ts(
 !!! error TS2345: Argument of type '{ y: Class; }' is not assignable to parameter of type '{ y: D; }'.
 !!! error TS2345:   Types of property 'y' are incompatible.
 !!! error TS2345:     Type 'Class' is not assignable to type 'D'.
+!!! error TS2345:       Property 'foo' is missing in type 'Class'.
     d3({});
        ~~
 !!! error TS2345: Argument of type '{}' is not assignable to parameter of type '{ y: D; }'.
diff --git a/tests/baselines/reference/dontShowCompilerGeneratedMembers.errors.txt b/tests/baselines/reference/dontShowCompilerGeneratedMembers.errors.txt
index c13a6b5fe2..d53571cc4a 100644
--- a/tests/baselines/reference/dontShowCompilerGeneratedMembers.errors.txt
+++ b/tests/baselines/reference/dontShowCompilerGeneratedMembers.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/compiler/dontShowCompilerGeneratedMembers.ts(1,5): error TS2322: Type 'number' is not assignable to type '{ (): any; x: number; }'.
-  Property 'x' is missing in type 'Number'.
 tests/cases/compiler/dontShowCompilerGeneratedMembers.ts(3,6): error TS1139: Type parameter declaration expected.
 tests/cases/compiler/dontShowCompilerGeneratedMembers.ts(4,1): error TS1109: Expression expected.
 
@@ -8,7 +7,6 @@ tests/cases/compiler/dontShowCompilerGeneratedMembers.ts(4,1): error TS1109: Exp
     var f: {
         ~
 !!! error TS2322: Type 'number' is not assignable to type '{ (): any; x: number; }'.
-!!! error TS2322:   Property 'x' is missing in type 'Number'.
         x: number;
         <-
          ~
diff --git a/tests/baselines/reference/enumAssignability.errors.txt b/tests/baselines/reference/enumAssignability.errors.txt
index 1316727076..bfabb5eae8 100644
--- a/tests/baselines/reference/enumAssignability.errors.txt
+++ b/tests/baselines/reference/enumAssignability.errors.txt
@@ -3,23 +3,16 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssi
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(29,9): error TS2322: Type 'E' is not assignable to type 'string'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(30,9): error TS2322: Type 'E' is not assignable to type 'boolean'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(31,9): error TS2322: Type 'E' is not assignable to type 'Date'.
-  Property 'toDateString' is missing in type 'Number'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(33,9): error TS2322: Type 'E' is not assignable to type 'void'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(36,9): error TS2322: Type 'E' is not assignable to type '() => {}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(37,9): error TS2322: Type 'E' is not assignable to type 'Function'.
-  Property 'apply' is missing in type 'Number'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(38,9): error TS2322: Type 'E' is not assignable to type '(x: number) => string'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(39,5): error TS2322: Type 'E' is not assignable to type 'C'.
-  Property 'foo' is missing in type 'Number'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(40,5): error TS2322: Type 'E' is not assignable to type 'I'.
-  Property 'foo' is missing in type 'Number'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(41,9): error TS2322: Type 'E' is not assignable to type 'number[]'.
-  Property 'length' is missing in type 'Number'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(42,9): error TS2322: Type 'E' is not assignable to type '{ foo: string; }'.
-  Property 'foo' is missing in type 'Number'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(43,9): error TS2322: Type 'E' is not assignable to type '<T>(x: T) => T'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(45,9): error TS2322: Type 'E' is not assignable to type 'String'.
-  Property 'charAt' is missing in type 'Number'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(48,9): error TS2322: Type 'E' is not assignable to type 'T'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(49,9): error TS2322: Type 'E' is not assignable to type 'U'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignability.ts(50,9): error TS2322: Type 'E' is not assignable to type 'V'.
@@ -69,7 +62,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssi
         var ee: Date = e;
             ~~
 !!! error TS2322: Type 'E' is not assignable to type 'Date'.
-!!! error TS2322:   Property 'toDateString' is missing in type 'Number'.
         var f: any = e; // ok
         var g: void = e;
             ~
@@ -82,26 +74,21 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssi
         var k: Function = e;
             ~
 !!! error TS2322: Type 'E' is not assignable to type 'Function'.
-!!! error TS2322:   Property 'apply' is missing in type 'Number'.
         var l: (x: number) => string = e;
             ~
 !!! error TS2322: Type 'E' is not assignable to type '(x: number) => string'.
         ac = e;
         ~~
 !!! error TS2322: Type 'E' is not assignable to type 'C'.
-!!! error TS2322:   Property 'foo' is missing in type 'Number'.
         ai = e;
         ~~
 !!! error TS2322: Type 'E' is not assignable to type 'I'.
-!!! error TS2322:   Property 'foo' is missing in type 'Number'.
         var m: number[] = e;
             ~
 !!! error TS2322: Type 'E' is not assignable to type 'number[]'.
-!!! error TS2322:   Property 'length' is missing in type 'Number'.
         var n: { foo: string } = e;
             ~
 !!! error TS2322: Type 'E' is not assignable to type '{ foo: string; }'.
-!!! error TS2322:   Property 'foo' is missing in type 'Number'.
         var o: <T>(x: T) => T = e;
             ~
 !!! error TS2322: Type 'E' is not assignable to type '<T>(x: T) => T'.
@@ -109,7 +96,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssi
         var q: String = e;
             ~
 !!! error TS2322: Type 'E' is not assignable to type 'String'.
-!!! error TS2322:   Property 'charAt' is missing in type 'Number'.
     
         function foo<T, U extends T, V extends Date, A extends Number, B extends E>(x: T, y: U, z: V) {
             x = e;
diff --git a/tests/baselines/reference/enumAssignmentCompat.errors.txt b/tests/baselines/reference/enumAssignmentCompat.errors.txt
index 3cddaf4596..f1a0124714 100644
--- a/tests/baselines/reference/enumAssignmentCompat.errors.txt
+++ b/tests/baselines/reference/enumAssignmentCompat.errors.txt
@@ -1,9 +1,7 @@
 tests/cases/compiler/enumAssignmentCompat.ts(26,5): error TS2322: Type 'typeof W' is not assignable to type 'number'.
 tests/cases/compiler/enumAssignmentCompat.ts(28,5): error TS2322: Type 'W' is not assignable to type 'typeof W'.
-  Property 'D' is missing in type 'Number'.
 tests/cases/compiler/enumAssignmentCompat.ts(30,5): error TS2322: Type 'number' is not assignable to type 'typeof W'.
 tests/cases/compiler/enumAssignmentCompat.ts(32,5): error TS2322: Type 'W' is not assignable to type 'WStatic'.
-  Property 'a' is missing in type 'Number'.
 tests/cases/compiler/enumAssignmentCompat.ts(33,5): error TS2322: Type 'number' is not assignable to type 'WStatic'.
 
 
@@ -40,7 +38,6 @@ tests/cases/compiler/enumAssignmentCompat.ts(33,5): error TS2322: Type 'number'
     var b: typeof W = W.a; // error
         ~
 !!! error TS2322: Type 'W' is not assignable to type 'typeof W'.
-!!! error TS2322:   Property 'D' is missing in type 'Number'.
     var c: typeof W.a = W.a;
     var d: typeof W = 3; // error
         ~
@@ -49,7 +46,6 @@ tests/cases/compiler/enumAssignmentCompat.ts(33,5): error TS2322: Type 'number'
     var f: WStatic = W.a; // error
         ~
 !!! error TS2322: Type 'W' is not assignable to type 'WStatic'.
-!!! error TS2322:   Property 'a' is missing in type 'Number'.
     var g: WStatic = 5; // error
         ~
 !!! error TS2322: Type 'number' is not assignable to type 'WStatic'.
diff --git a/tests/baselines/reference/enumAssignmentCompat2.errors.txt b/tests/baselines/reference/enumAssignmentCompat2.errors.txt
index d87d6acf6a..4e0660eaae 100644
--- a/tests/baselines/reference/enumAssignmentCompat2.errors.txt
+++ b/tests/baselines/reference/enumAssignmentCompat2.errors.txt
@@ -1,9 +1,7 @@
 tests/cases/compiler/enumAssignmentCompat2.ts(25,5): error TS2322: Type 'typeof W' is not assignable to type 'number'.
 tests/cases/compiler/enumAssignmentCompat2.ts(27,5): error TS2322: Type 'W' is not assignable to type 'typeof W'.
-  Property 'a' is missing in type 'Number'.
 tests/cases/compiler/enumAssignmentCompat2.ts(29,5): error TS2322: Type 'number' is not assignable to type 'typeof W'.
 tests/cases/compiler/enumAssignmentCompat2.ts(31,5): error TS2322: Type 'W' is not assignable to type 'WStatic'.
-  Property 'a' is missing in type 'Number'.
 tests/cases/compiler/enumAssignmentCompat2.ts(32,5): error TS2322: Type 'number' is not assignable to type 'WStatic'.
 
 
@@ -39,7 +37,6 @@ tests/cases/compiler/enumAssignmentCompat2.ts(32,5): error TS2322: Type 'number'
     var b: typeof W = W.a; // error
         ~
 !!! error TS2322: Type 'W' is not assignable to type 'typeof W'.
-!!! error TS2322:   Property 'a' is missing in type 'Number'.
     var c: typeof W.a = W.a;
     var d: typeof W = 3; // error
         ~
@@ -48,7 +45,6 @@ tests/cases/compiler/enumAssignmentCompat2.ts(32,5): error TS2322: Type 'number'
     var f: WStatic = W.a; // error
         ~
 !!! error TS2322: Type 'W' is not assignable to type 'WStatic'.
-!!! error TS2322:   Property 'a' is missing in type 'Number'.
     var g: WStatic = 5; // error
         ~
 !!! error TS2322: Type 'number' is not assignable to type 'WStatic'.
diff --git a/tests/baselines/reference/everyTypeWithAnnotationAndInvalidInitializer.errors.txt b/tests/baselines/reference/everyTypeWithAnnotationAndInvalidInitializer.errors.txt
index 1247844247..fc1bcaa545 100644
--- a/tests/baselines/reference/everyTypeWithAnnotationAndInvalidInitializer.errors.txt
+++ b/tests/baselines/reference/everyTypeWithAnnotationAndInvalidInitializer.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/conformance/statements/VariableStatements/everyTypeWithAnnotationAndInvalidInitializer.ts(34,5): error TS2322: Type 'string' is not assignable to type 'number'.
 tests/cases/conformance/statements/VariableStatements/everyTypeWithAnnotationAndInvalidInitializer.ts(35,5): error TS2322: Type 'number' is not assignable to type 'string'.
 tests/cases/conformance/statements/VariableStatements/everyTypeWithAnnotationAndInvalidInitializer.ts(36,5): error TS2322: Type 'number' is not assignable to type 'Date'.
-  Property 'toDateString' is missing in type 'Number'.
 tests/cases/conformance/statements/VariableStatements/everyTypeWithAnnotationAndInvalidInitializer.ts(38,5): error TS2322: Type 'number' is not assignable to type 'void'.
 tests/cases/conformance/statements/VariableStatements/everyTypeWithAnnotationAndInvalidInitializer.ts(40,5): error TS2322: Type 'D<{}>' is not assignable to type 'I'.
   Property 'id' is missing in type 'D<{}>'.
@@ -76,7 +75,6 @@ tests/cases/conformance/statements/VariableStatements/everyTypeWithAnnotationAnd
     var aDate: Date = 9.9;
         ~~~~~
 !!! error TS2322: Type 'number' is not assignable to type 'Date'.
-!!! error TS2322:   Property 'toDateString' is missing in type 'Number'.
     
     var aVoid: void = 9.9;
         ~~~~~
diff --git a/tests/baselines/reference/exportAssignmentConstrainedGenericType.errors.txt b/tests/baselines/reference/exportAssignmentConstrainedGenericType.errors.txt
index 946bc8ee8b..cf63c48925 100644
--- a/tests/baselines/reference/exportAssignmentConstrainedGenericType.errors.txt
+++ b/tests/baselines/reference/exportAssignmentConstrainedGenericType.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/conformance/externalModules/foo_1.ts(2,17): error TS2345: Argument of type 'boolean' is not assignable to parameter of type '{ a: string; b: number; }'.
-  Property 'a' is missing in type 'Boolean'.
 
 
 ==== tests/cases/conformance/externalModules/foo_1.ts (1 errors) ====
@@ -7,7 +6,6 @@ tests/cases/conformance/externalModules/foo_1.ts(2,17): error TS2345: Argument o
     var x = new foo(true); // Should error
                     ~~~~
 !!! error TS2345: Argument of type 'boolean' is not assignable to parameter of type '{ a: string; b: number; }'.
-!!! error TS2345:   Property 'a' is missing in type 'Boolean'.
     var y = new foo({a: "test", b: 42}); // Should be OK
     var z: number = y.test.b;
 ==== tests/cases/conformance/externalModules/foo_0.ts (0 errors) ====
diff --git a/tests/baselines/reference/functionCall7.errors.txt b/tests/baselines/reference/functionCall7.errors.txt
index 19e572fa58..576ea9c266 100644
--- a/tests/baselines/reference/functionCall7.errors.txt
+++ b/tests/baselines/reference/functionCall7.errors.txt
@@ -1,6 +1,5 @@
 tests/cases/compiler/functionCall7.ts(5,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/compiler/functionCall7.ts(6,5): error TS2345: Argument of type 'number' is not assignable to parameter of type 'c1'.
-  Property 'a' is missing in type 'Number'.
 tests/cases/compiler/functionCall7.ts(7,1): error TS2346: Supplied parameters do not match any signature of call target.
 
 
@@ -15,7 +14,6 @@ tests/cases/compiler/functionCall7.ts(7,1): error TS2346: Supplied parameters do
     foo(4);
         ~
 !!! error TS2345: Argument of type 'number' is not assignable to parameter of type 'c1'.
-!!! error TS2345:   Property 'a' is missing in type 'Number'.
     foo();
     ~~~~~
 !!! error TS2346: Supplied parameters do not match any signature of call target.
diff --git a/tests/baselines/reference/functionConstraintSatisfaction2.errors.txt b/tests/baselines/reference/functionConstraintSatisfaction2.errors.txt
index 7b3aa92828..d2299894c5 100644
--- a/tests/baselines/reference/functionConstraintSatisfaction2.errors.txt
+++ b/tests/baselines/reference/functionConstraintSatisfaction2.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/conformance/types/typeParameters/typeArgumentLists/functionConstraintSatisfaction2.ts(5,5): error TS2345: Argument of type 'number' is not assignable to parameter of type 'Function'.
-  Property 'apply' is missing in type 'Number'.
 tests/cases/conformance/types/typeParameters/typeArgumentLists/functionConstraintSatisfaction2.ts(6,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/conformance/types/typeParameters/typeArgumentLists/functionConstraintSatisfaction2.ts(7,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/conformance/types/typeParameters/typeArgumentLists/functionConstraintSatisfaction2.ts(23,14): error TS2345: Argument of type 'Function' is not assignable to parameter of type '(x: string) => string'.
@@ -20,9 +19,11 @@ tests/cases/conformance/types/typeParameters/typeArgumentLists/functionConstrain
   Type 'F2' provides no match for the signature '(x: string): string'
 tests/cases/conformance/types/typeParameters/typeArgumentLists/functionConstraintSatisfaction2.ts(37,10): error TS2345: Argument of type 'T' is not assignable to parameter of type '(x: string) => string'.
   Type '() => void' is not assignable to type '(x: string) => string'.
+    Type 'void' is not assignable to type 'string'.
 tests/cases/conformance/types/typeParameters/typeArgumentLists/functionConstraintSatisfaction2.ts(38,10): error TS2345: Argument of type 'U' is not assignable to parameter of type '(x: string) => string'.
   Type 'T' is not assignable to type '(x: string) => string'.
     Type '() => void' is not assignable to type '(x: string) => string'.
+      Type 'void' is not assignable to type 'string'.
 
 
 ==== tests/cases/conformance/types/typeParameters/typeArgumentLists/functionConstraintSatisfaction2.ts (13 errors) ====
@@ -33,7 +34,6 @@ tests/cases/conformance/types/typeParameters/typeArgumentLists/functionConstrain
     foo(1);
         ~
 !!! error TS2345: Argument of type 'number' is not assignable to parameter of type 'Function'.
-!!! error TS2345:   Property 'apply' is missing in type 'Number'.
     foo(() => { }, 1);
     ~~~~~~~~~~~~~~~~~
 !!! error TS2346: Supplied parameters do not match any signature of call target.
@@ -97,10 +97,12 @@ tests/cases/conformance/types/typeParameters/typeArgumentLists/functionConstrain
              ~
 !!! error TS2345: Argument of type 'T' is not assignable to parameter of type '(x: string) => string'.
 !!! error TS2345:   Type '() => void' is not assignable to type '(x: string) => string'.
+!!! error TS2345:     Type 'void' is not assignable to type 'string'.
         foo2(y);
              ~
 !!! error TS2345: Argument of type 'U' is not assignable to parameter of type '(x: string) => string'.
 !!! error TS2345:   Type 'T' is not assignable to type '(x: string) => string'.
 !!! error TS2345:     Type '() => void' is not assignable to type '(x: string) => string'.
+!!! error TS2345:       Type 'void' is not assignable to type 'string'.
     }
     
\ No newline at end of file
diff --git a/tests/baselines/reference/genericCallWithConstraintsTypeArgumentInference2.errors.txt b/tests/baselines/reference/genericCallWithConstraintsTypeArgumentInference2.errors.txt
index 6ac3c9e670..805bde82b6 100644
--- a/tests/baselines/reference/genericCallWithConstraintsTypeArgumentInference2.errors.txt
+++ b/tests/baselines/reference/genericCallWithConstraintsTypeArgumentInference2.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithConstraintsTypeArgumentInference2.ts(11,26): error TS2345: Argument of type 'number' is not assignable to parameter of type 'Date'.
-  Property 'toDateString' is missing in type 'Number'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithConstraintsTypeArgumentInference2.ts (1 errors) ====
@@ -16,5 +15,4 @@ tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithCon
     var r4 = foo<Date, Date>(1); // error
                              ~
 !!! error TS2345: Argument of type 'number' is not assignable to parameter of type 'Date'.
-!!! error TS2345:   Property 'toDateString' is missing in type 'Number'.
     var r5 = foo<Date, Date>(new Date()); // no error
\ No newline at end of file
diff --git a/tests/baselines/reference/genericCombinators2.errors.txt b/tests/baselines/reference/genericCombinators2.errors.txt
index d590f1030c..5be717109c 100644
--- a/tests/baselines/reference/genericCombinators2.errors.txt
+++ b/tests/baselines/reference/genericCombinators2.errors.txt
@@ -1,6 +1,5 @@
 tests/cases/compiler/genericCombinators2.ts(15,43): error TS2345: Argument of type '(x: number, y: string) => string' is not assignable to parameter of type '(x: number, y: string) => Date'.
   Type 'string' is not assignable to type 'Date'.
-    Property 'toDateString' is missing in type 'String'.
 tests/cases/compiler/genericCombinators2.ts(16,43): error TS2345: Argument of type '(x: number, y: string) => string' is not assignable to parameter of type '(x: number, y: string) => Date'.
   Type 'string' is not assignable to type 'Date'.
 
@@ -24,7 +23,6 @@ tests/cases/compiler/genericCombinators2.ts(16,43): error TS2345: Argument of ty
                                               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2345: Argument of type '(x: number, y: string) => string' is not assignable to parameter of type '(x: number, y: string) => Date'.
 !!! error TS2345:   Type 'string' is not assignable to type 'Date'.
-!!! error TS2345:     Property 'toDateString' is missing in type 'String'.
     var r5b = _.map<number, string, Date>(c2, rf1);
                                               ~~~
 !!! error TS2345: Argument of type '(x: number, y: string) => string' is not assignable to parameter of type '(x: number, y: string) => Date'.
diff --git a/tests/baselines/reference/genericDerivedTypeWithSpecializedBase2.errors.txt b/tests/baselines/reference/genericDerivedTypeWithSpecializedBase2.errors.txt
index 38818b5986..1e5e3b6ee9 100644
--- a/tests/baselines/reference/genericDerivedTypeWithSpecializedBase2.errors.txt
+++ b/tests/baselines/reference/genericDerivedTypeWithSpecializedBase2.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/genericDerivedTypeWithSpecializedBase2.ts(11,1): error TS2322: Type 'B<number>' is not assignable to type 'A<{ length: number; foo: number; }>'.
   Types of property 'x' are incompatible.
     Type 'string' is not assignable to type '{ length: number; foo: number; }'.
-      Property 'foo' is missing in type 'String'.
 
 
 ==== tests/cases/compiler/genericDerivedTypeWithSpecializedBase2.ts (1 errors) ====
@@ -20,5 +19,4 @@ tests/cases/compiler/genericDerivedTypeWithSpecializedBase2.ts(11,1): error TS23
 !!! error TS2322: Type 'B<number>' is not assignable to type 'A<{ length: number; foo: number; }>'.
 !!! error TS2322:   Types of property 'x' are incompatible.
 !!! error TS2322:     Type 'string' is not assignable to type '{ length: number; foo: number; }'.
-!!! error TS2322:       Property 'foo' is missing in type 'String'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/genericRestArgs.errors.txt b/tests/baselines/reference/genericRestArgs.errors.txt
index 99106ebd79..8a97745295 100644
--- a/tests/baselines/reference/genericRestArgs.errors.txt
+++ b/tests/baselines/reference/genericRestArgs.errors.txt
@@ -4,7 +4,6 @@ tests/cases/compiler/genericRestArgs.ts(5,34): error TS2345: Argument of type 's
 tests/cases/compiler/genericRestArgs.ts(10,12): error TS2453: The type argument for type parameter 'T' cannot be inferred from the usage. Consider specifying the type arguments explicitly.
   Type argument candidate 'number' is not a valid type argument because it is not a supertype of candidate 'string'.
 tests/cases/compiler/genericRestArgs.ts(12,30): error TS2345: Argument of type 'number' is not assignable to parameter of type 'any[]'.
-  Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/genericRestArgs.ts (4 errors) ====
@@ -29,5 +28,4 @@ tests/cases/compiler/genericRestArgs.ts(12,30): error TS2345: Argument of type '
     var a2Gb = makeArrayG<any>(1, "");
     var a2Gc = makeArrayG<any[]>(1, ""); // error
                                  ~
-!!! error TS2345: Argument of type 'number' is not assignable to parameter of type 'any[]'.
-!!! error TS2345:   Property 'length' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2345: Argument of type 'number' is not assignable to parameter of type 'any[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/globalIsContextualKeyword.js b/tests/baselines/reference/globalIsContextualKeyword.js
new file mode 100644
index 0000000000..b6fa566c91
--- /dev/null
+++ b/tests/baselines/reference/globalIsContextualKeyword.js
@@ -0,0 +1,34 @@
+//// [globalIsContextualKeyword.ts]
+function a() {
+    let global = 1;
+}
+function b() {
+    class global {}
+}
+
+namespace global {
+}
+
+function foo(global: number) {
+}
+
+let obj = {
+    global: "123"
+}
+
+//// [globalIsContextualKeyword.js]
+function a() {
+    var global = 1;
+}
+function b() {
+    var global = (function () {
+        function global() {
+        }
+        return global;
+    }());
+}
+function foo(global) {
+}
+var obj = {
+    global: "123"
+};
diff --git a/tests/baselines/reference/globalIsContextualKeyword.symbols b/tests/baselines/reference/globalIsContextualKeyword.symbols
new file mode 100644
index 0000000000..edc1cebbc9
--- /dev/null
+++ b/tests/baselines/reference/globalIsContextualKeyword.symbols
@@ -0,0 +1,29 @@
+=== tests/cases/compiler/globalIsContextualKeyword.ts ===
+function a() {
+>a : Symbol(a, Decl(globalIsContextualKeyword.ts, 0, 0))
+
+    let global = 1;
+>global : Symbol(global, Decl(globalIsContextualKeyword.ts, 1, 7))
+}
+function b() {
+>b : Symbol(b, Decl(globalIsContextualKeyword.ts, 2, 1))
+
+    class global {}
+>global : Symbol(global, Decl(globalIsContextualKeyword.ts, 3, 14))
+}
+
+namespace global {
+>global : Symbol(global, Decl(globalIsContextualKeyword.ts, 5, 1))
+}
+
+function foo(global: number) {
+>foo : Symbol(foo, Decl(globalIsContextualKeyword.ts, 8, 1))
+>global : Symbol(global, Decl(globalIsContextualKeyword.ts, 10, 13))
+}
+
+let obj = {
+>obj : Symbol(obj, Decl(globalIsContextualKeyword.ts, 13, 3))
+
+    global: "123"
+>global : Symbol(global, Decl(globalIsContextualKeyword.ts, 13, 11))
+}
diff --git a/tests/baselines/reference/globalIsContextualKeyword.types b/tests/baselines/reference/globalIsContextualKeyword.types
new file mode 100644
index 0000000000..d0bf624af6
--- /dev/null
+++ b/tests/baselines/reference/globalIsContextualKeyword.types
@@ -0,0 +1,32 @@
+=== tests/cases/compiler/globalIsContextualKeyword.ts ===
+function a() {
+>a : () => void
+
+    let global = 1;
+>global : number
+>1 : number
+}
+function b() {
+>b : () => void
+
+    class global {}
+>global : global
+}
+
+namespace global {
+>global : any
+}
+
+function foo(global: number) {
+>foo : (global: number) => void
+>global : number
+}
+
+let obj = {
+>obj : { global: string; }
+>{    global: "123"} : { global: string; }
+
+    global: "123"
+>global : string
+>"123" : string
+}
diff --git a/tests/baselines/reference/importDeclRefereingExternalModuleWithNoResolve.errors.txt b/tests/baselines/reference/importDeclRefereingExternalModuleWithNoResolve.errors.txt
index 34cfe02305..5d70b32aa1 100644
--- a/tests/baselines/reference/importDeclRefereingExternalModuleWithNoResolve.errors.txt
+++ b/tests/baselines/reference/importDeclRefereingExternalModuleWithNoResolve.errors.txt
@@ -1,6 +1,6 @@
 tests/cases/compiler/importDeclRefereingExternalModuleWithNoResolve.ts(1,1): error TS1148: Cannot compile modules unless the '--module' flag is provided. Consider setting the 'module' compiler option in a 'tsconfig.json' file.
 tests/cases/compiler/importDeclRefereingExternalModuleWithNoResolve.ts(1,20): error TS2307: Cannot find module 'externalModule'.
-tests/cases/compiler/importDeclRefereingExternalModuleWithNoResolve.ts(2,16): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+tests/cases/compiler/importDeclRefereingExternalModuleWithNoResolve.ts(2,16): error TS2664: Invalid module name in augmentation, module 'm1' cannot be found.
 tests/cases/compiler/importDeclRefereingExternalModuleWithNoResolve.ts(3,26): error TS2307: Cannot find module 'externalModule'.
 
 
@@ -12,7 +12,7 @@ tests/cases/compiler/importDeclRefereingExternalModuleWithNoResolve.ts(3,26): er
 !!! error TS2307: Cannot find module 'externalModule'.
     declare module "m1" {
                    ~~~~
-!!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+!!! error TS2664: Invalid module name in augmentation, module 'm1' cannot be found.
         import im2 = require("externalModule");
                              ~~~~~~~~~~~~~~~~
 !!! error TS2307: Cannot find module 'externalModule'.
diff --git a/tests/baselines/reference/initializerReferencingConstructorParameters.errors.txt b/tests/baselines/reference/initializerReferencingConstructorParameters.errors.txt
index 623bd53574..eb6744d656 100644
--- a/tests/baselines/reference/initializerReferencingConstructorParameters.errors.txt
+++ b/tests/baselines/reference/initializerReferencingConstructorParameters.errors.txt
@@ -1,9 +1,9 @@
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(4,9): error TS2304: Cannot find name 'x'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(5,15): error TS2304: Cannot find name 'x'.
-tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(10,9): error TS2304: Cannot find name 'x'.
+tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(10,9): error TS2663: Cannot find name 'x'. Did you mean the instance member 'this.x'?
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(11,15): error TS2304: Cannot find name 'x'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(17,15): error TS1003: Identifier expected.
-tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(23,9): error TS2304: Cannot find name 'x'.
+tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(23,9): error TS2663: Cannot find name 'x'. Did you mean the instance member 'this.x'?
 
 
 ==== tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts (6 errors) ====
@@ -22,7 +22,7 @@ tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencin
     class D {
         a = x; // error
             ~
-!!! error TS2304: Cannot find name 'x'.
+!!! error TS2663: Cannot find name 'x'. Did you mean the instance member 'this.x'?
         b: typeof x; // error
                   ~
 !!! error TS2304: Cannot find name 'x'.
@@ -41,6 +41,6 @@ tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencin
         a = this.x; // ok
         b = x; // error
             ~
-!!! error TS2304: Cannot find name 'x'.
+!!! error TS2663: Cannot find name 'x'. Did you mean the instance member 'this.x'?
         constructor(public x: T) { }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/instanceSubtypeCheck2.errors.txt b/tests/baselines/reference/instanceSubtypeCheck2.errors.txt
index ba93c2ef12..81982ac3ec 100644
--- a/tests/baselines/reference/instanceSubtypeCheck2.errors.txt
+++ b/tests/baselines/reference/instanceSubtypeCheck2.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/instanceSubtypeCheck2.ts(5,7): error TS2415: Class 'C2<T>' incorrectly extends base class 'C1<T>'.
   Types of property 'x' are incompatible.
     Type 'string' is not assignable to type 'C2<T>'.
-      Property 'x' is missing in type 'String'.
 
 
 ==== tests/cases/compiler/instanceSubtypeCheck2.ts (1 errors) ====
@@ -14,6 +13,5 @@ tests/cases/compiler/instanceSubtypeCheck2.ts(5,7): error TS2415: Class 'C2<T>'
 !!! error TS2415: Class 'C2<T>' incorrectly extends base class 'C1<T>'.
 !!! error TS2415:   Types of property 'x' are incompatible.
 !!! error TS2415:     Type 'string' is not assignable to type 'C2<T>'.
-!!! error TS2415:       Property 'x' is missing in type 'String'.
         x: string
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/intTypeCheck.errors.txt b/tests/baselines/reference/intTypeCheck.errors.txt
index 3d805a6582..a860f5e360 100644
--- a/tests/baselines/reference/intTypeCheck.errors.txt
+++ b/tests/baselines/reference/intTypeCheck.errors.txt
@@ -9,7 +9,6 @@ tests/cases/compiler/intTypeCheck.ts(101,5): error TS2322: Type 'Base' is not as
 tests/cases/compiler/intTypeCheck.ts(103,5): error TS2322: Type '() => void' is not assignable to type 'i1'.
   Property 'p' is missing in type '() => void'.
 tests/cases/compiler/intTypeCheck.ts(106,5): error TS2322: Type 'boolean' is not assignable to type 'i1'.
-  Property 'p' is missing in type 'Boolean'.
 tests/cases/compiler/intTypeCheck.ts(106,20): error TS1109: Expression expected.
 tests/cases/compiler/intTypeCheck.ts(106,21): error TS2304: Cannot find name 'i1'.
 tests/cases/compiler/intTypeCheck.ts(107,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -38,7 +37,6 @@ tests/cases/compiler/intTypeCheck.ts(134,22): error TS2304: Cannot find name 'i3
 tests/cases/compiler/intTypeCheck.ts(135,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(142,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(148,5): error TS2322: Type 'boolean' is not assignable to type 'i4'.
-  Index signature is missing in type 'Boolean'.
 tests/cases/compiler/intTypeCheck.ts(148,21): error TS1109: Expression expected.
 tests/cases/compiler/intTypeCheck.ts(148,22): error TS2304: Cannot find name 'i4'.
 tests/cases/compiler/intTypeCheck.ts(149,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -52,7 +50,6 @@ tests/cases/compiler/intTypeCheck.ts(157,5): error TS2322: Type 'Base' is not as
 tests/cases/compiler/intTypeCheck.ts(159,5): error TS2322: Type '() => void' is not assignable to type 'i5'.
   Property 'p' is missing in type '() => void'.
 tests/cases/compiler/intTypeCheck.ts(162,5): error TS2322: Type 'boolean' is not assignable to type 'i5'.
-  Property 'p' is missing in type 'Boolean'.
 tests/cases/compiler/intTypeCheck.ts(162,21): error TS1109: Expression expected.
 tests/cases/compiler/intTypeCheck.ts(162,22): error TS2304: Cannot find name 'i5'.
 tests/cases/compiler/intTypeCheck.ts(163,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -83,7 +80,6 @@ tests/cases/compiler/intTypeCheck.ts(190,22): error TS2304: Cannot find name 'i7
 tests/cases/compiler/intTypeCheck.ts(191,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(198,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(204,5): error TS2322: Type 'boolean' is not assignable to type 'i8'.
-  Index signature is missing in type 'Boolean'.
 tests/cases/compiler/intTypeCheck.ts(204,21): error TS1109: Expression expected.
 tests/cases/compiler/intTypeCheck.ts(204,22): error TS2304: Cannot find name 'i8'.
 tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -215,7 +211,6 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
     var obj9: i1 = new <i1> anyVar;
         ~~~~
 !!! error TS2322: Type 'boolean' is not assignable to type 'i1'.
-!!! error TS2322:   Property 'p' is missing in type 'Boolean'.
                        ~
 !!! error TS1109: Expression expected.
                         ~~
@@ -307,7 +302,6 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
     var obj42: i4 = new <i4> anyVar;
         ~~~~~
 !!! error TS2322: Type 'boolean' is not assignable to type 'i4'.
-!!! error TS2322:   Index signature is missing in type 'Boolean'.
                         ~
 !!! error TS1109: Expression expected.
                          ~~
@@ -344,7 +338,6 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
     var obj53: i5 = new <i5> anyVar;
         ~~~~~
 !!! error TS2322: Type 'boolean' is not assignable to type 'i5'.
-!!! error TS2322:   Property 'p' is missing in type 'Boolean'.
                         ~
 !!! error TS1109: Expression expected.
                          ~~
@@ -439,7 +432,6 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
     var obj86: i8 = new <i8> anyVar;
         ~~~~~
 !!! error TS2322: Type 'boolean' is not assignable to type 'i8'.
-!!! error TS2322:   Index signature is missing in type 'Boolean'.
                         ~
 !!! error TS1109: Expression expected.
                          ~~
diff --git a/tests/baselines/reference/interfaceImplementation7.errors.txt b/tests/baselines/reference/interfaceImplementation7.errors.txt
index b297015dfb..1025a1f529 100644
--- a/tests/baselines/reference/interfaceImplementation7.errors.txt
+++ b/tests/baselines/reference/interfaceImplementation7.errors.txt
@@ -4,7 +4,6 @@ tests/cases/compiler/interfaceImplementation7.ts(7,7): error TS2420: Class 'C1'
   Types of property 'name' are incompatible.
     Type '() => string' is not assignable to type '() => { s: string; n: number; }'.
       Type 'string' is not assignable to type '{ s: string; n: number; }'.
-        Property 's' is missing in type 'String'.
 
 
 ==== tests/cases/compiler/interfaceImplementation7.ts (2 errors) ====
@@ -23,7 +22,6 @@ tests/cases/compiler/interfaceImplementation7.ts(7,7): error TS2420: Class 'C1'
 !!! error TS2420:   Types of property 'name' are incompatible.
 !!! error TS2420:     Type '() => string' is not assignable to type '() => { s: string; n: number; }'.
 !!! error TS2420:       Type 'string' is not assignable to type '{ s: string; n: number; }'.
-!!! error TS2420:         Property 's' is missing in type 'String'.
         public name(): string { return ""; }
     }
     
\ No newline at end of file
diff --git a/tests/baselines/reference/intersectionAndUnionTypes.errors.txt b/tests/baselines/reference/intersectionAndUnionTypes.errors.txt
index 4f26cc63ba..d4526c815c 100644
--- a/tests/baselines/reference/intersectionAndUnionTypes.errors.txt
+++ b/tests/baselines/reference/intersectionAndUnionTypes.errors.txt
@@ -1,5 +1,6 @@
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(19,1): error TS2322: Type 'A' is not assignable to type 'A & B'.
   Type 'A' is not assignable to type 'B'.
+    Property 'b' is missing in type 'A'.
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(20,1): error TS2322: Type 'B' is not assignable to type 'A & B'.
   Type 'B' is not assignable to type 'A'.
     Property 'a' is missing in type 'B'.
@@ -7,26 +8,32 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(23,1): e
   Type 'A' is not assignable to type '(A & B) | (C & D)'.
     Type 'A' is not assignable to type 'C & D'.
       Type 'A' is not assignable to type 'C'.
+        Property 'c' is missing in type 'A'.
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(25,1): error TS2322: Type 'C | D' is not assignable to type '(A & B) | (C & D)'.
   Type 'C' is not assignable to type '(A & B) | (C & D)'.
     Type 'C' is not assignable to type 'C & D'.
       Type 'C' is not assignable to type 'D'.
+        Property 'd' is missing in type 'C'.
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(26,1): error TS2322: Type '(A & B) | (C & D)' is not assignable to type 'A & B'.
   Type 'C & D' is not assignable to type 'A & B'.
     Type 'C & D' is not assignable to type 'A'.
       Type 'D' is not assignable to type 'A'.
+        Property 'a' is missing in type 'D'.
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(27,1): error TS2322: Type '(A & B) | (C & D)' is not assignable to type 'A | B'.
   Type 'C & D' is not assignable to type 'A | B'.
     Type 'C & D' is not assignable to type 'B'.
       Type 'D' is not assignable to type 'B'.
+        Property 'b' is missing in type 'D'.
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(28,1): error TS2322: Type '(A & B) | (C & D)' is not assignable to type 'C & D'.
   Type 'A & B' is not assignable to type 'C & D'.
     Type 'A & B' is not assignable to type 'C'.
       Type 'B' is not assignable to type 'C'.
+        Property 'c' is missing in type 'B'.
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(29,1): error TS2322: Type '(A & B) | (C & D)' is not assignable to type 'C | D'.
   Type 'A & B' is not assignable to type 'C | D'.
     Type 'A & B' is not assignable to type 'D'.
       Type 'B' is not assignable to type 'D'.
+        Property 'd' is missing in type 'B'.
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(31,1): error TS2322: Type 'A & B' is not assignable to type '(A | B) & (C | D)'.
   Type 'A & B' is not assignable to type 'C | D'.
     Type 'A & B' is not assignable to type 'D'.
@@ -35,6 +42,7 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(32,1): e
   Type 'A' is not assignable to type '(A | B) & (C | D)'.
     Type 'A' is not assignable to type 'C | D'.
       Type 'A' is not assignable to type 'D'.
+        Property 'd' is missing in type 'A'.
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(33,1): error TS2322: Type 'C & D' is not assignable to type '(A | B) & (C | D)'.
   Type 'C & D' is not assignable to type 'A | B'.
     Type 'C & D' is not assignable to type 'B'.
@@ -43,14 +51,17 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(34,1): e
   Type 'C' is not assignable to type '(A | B) & (C | D)'.
     Type 'C' is not assignable to type 'A | B'.
       Type 'C' is not assignable to type 'B'.
+        Property 'b' is missing in type 'C'.
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(35,1): error TS2322: Type '(A | B) & (C | D)' is not assignable to type 'A & B'.
   Type '(A | B) & (C | D)' is not assignable to type 'A'.
     Type 'C | D' is not assignable to type 'A'.
       Type 'C' is not assignable to type 'A'.
+        Property 'a' is missing in type 'C'.
 tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(37,1): error TS2322: Type '(A | B) & (C | D)' is not assignable to type 'C & D'.
   Type '(A | B) & (C | D)' is not assignable to type 'C'.
     Type 'C | D' is not assignable to type 'C'.
       Type 'D' is not assignable to type 'C'.
+        Property 'c' is missing in type 'D'.
 
 
 ==== tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts (14 errors) ====
@@ -76,6 +87,7 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(37,1): e
     ~~~
 !!! error TS2322: Type 'A' is not assignable to type 'A & B'.
 !!! error TS2322:   Type 'A' is not assignable to type 'B'.
+!!! error TS2322:     Property 'b' is missing in type 'A'.
     anb = b;
     ~~~
 !!! error TS2322: Type 'B' is not assignable to type 'A & B'.
@@ -89,6 +101,7 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(37,1): e
 !!! error TS2322:   Type 'A' is not assignable to type '(A & B) | (C & D)'.
 !!! error TS2322:     Type 'A' is not assignable to type 'C & D'.
 !!! error TS2322:       Type 'A' is not assignable to type 'C'.
+!!! error TS2322:         Property 'c' is missing in type 'A'.
     x = cnd;  // Ok
     x = cod;
     ~
@@ -96,30 +109,35 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(37,1): e
 !!! error TS2322:   Type 'C' is not assignable to type '(A & B) | (C & D)'.
 !!! error TS2322:     Type 'C' is not assignable to type 'C & D'.
 !!! error TS2322:       Type 'C' is not assignable to type 'D'.
+!!! error TS2322:         Property 'd' is missing in type 'C'.
     anb = x;
     ~~~
 !!! error TS2322: Type '(A & B) | (C & D)' is not assignable to type 'A & B'.
 !!! error TS2322:   Type 'C & D' is not assignable to type 'A & B'.
 !!! error TS2322:     Type 'C & D' is not assignable to type 'A'.
 !!! error TS2322:       Type 'D' is not assignable to type 'A'.
+!!! error TS2322:         Property 'a' is missing in type 'D'.
     aob = x;
     ~~~
 !!! error TS2322: Type '(A & B) | (C & D)' is not assignable to type 'A | B'.
 !!! error TS2322:   Type 'C & D' is not assignable to type 'A | B'.
 !!! error TS2322:     Type 'C & D' is not assignable to type 'B'.
 !!! error TS2322:       Type 'D' is not assignable to type 'B'.
+!!! error TS2322:         Property 'b' is missing in type 'D'.
     cnd = x;
     ~~~
 !!! error TS2322: Type '(A & B) | (C & D)' is not assignable to type 'C & D'.
 !!! error TS2322:   Type 'A & B' is not assignable to type 'C & D'.
 !!! error TS2322:     Type 'A & B' is not assignable to type 'C'.
 !!! error TS2322:       Type 'B' is not assignable to type 'C'.
+!!! error TS2322:         Property 'c' is missing in type 'B'.
     cod = x;
     ~~~
 !!! error TS2322: Type '(A & B) | (C & D)' is not assignable to type 'C | D'.
 !!! error TS2322:   Type 'A & B' is not assignable to type 'C | D'.
 !!! error TS2322:     Type 'A & B' is not assignable to type 'D'.
 !!! error TS2322:       Type 'B' is not assignable to type 'D'.
+!!! error TS2322:         Property 'd' is missing in type 'B'.
     
     y = anb;
     ~
@@ -133,6 +151,7 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(37,1): e
 !!! error TS2322:   Type 'A' is not assignable to type '(A | B) & (C | D)'.
 !!! error TS2322:     Type 'A' is not assignable to type 'C | D'.
 !!! error TS2322:       Type 'A' is not assignable to type 'D'.
+!!! error TS2322:         Property 'd' is missing in type 'A'.
     y = cnd;
     ~
 !!! error TS2322: Type 'C & D' is not assignable to type '(A | B) & (C | D)'.
@@ -145,12 +164,14 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(37,1): e
 !!! error TS2322:   Type 'C' is not assignable to type '(A | B) & (C | D)'.
 !!! error TS2322:     Type 'C' is not assignable to type 'A | B'.
 !!! error TS2322:       Type 'C' is not assignable to type 'B'.
+!!! error TS2322:         Property 'b' is missing in type 'C'.
     anb = y;
     ~~~
 !!! error TS2322: Type '(A | B) & (C | D)' is not assignable to type 'A & B'.
 !!! error TS2322:   Type '(A | B) & (C | D)' is not assignable to type 'A'.
 !!! error TS2322:     Type 'C | D' is not assignable to type 'A'.
 !!! error TS2322:       Type 'C' is not assignable to type 'A'.
+!!! error TS2322:         Property 'a' is missing in type 'C'.
     aob = y;  // Ok
     cnd = y;
     ~~~
@@ -158,5 +179,6 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(37,1): e
 !!! error TS2322:   Type '(A | B) & (C | D)' is not assignable to type 'C'.
 !!! error TS2322:     Type 'C | D' is not assignable to type 'C'.
 !!! error TS2322:       Type 'D' is not assignable to type 'C'.
+!!! error TS2322:         Property 'c' is missing in type 'D'.
     cod = y;  // Ok
     
\ No newline at end of file
diff --git a/tests/baselines/reference/invalidBooleanAssignments.errors.txt b/tests/baselines/reference/invalidBooleanAssignments.errors.txt
index 84ced22611..99d32aff9b 100644
--- a/tests/baselines/reference/invalidBooleanAssignments.errors.txt
+++ b/tests/baselines/reference/invalidBooleanAssignments.errors.txt
@@ -3,9 +3,7 @@ tests/cases/conformance/types/primitives/boolean/invalidBooleanAssignments.ts(4,
 tests/cases/conformance/types/primitives/boolean/invalidBooleanAssignments.ts(5,5): error TS2322: Type 'boolean' is not assignable to type 'void'.
 tests/cases/conformance/types/primitives/boolean/invalidBooleanAssignments.ts(9,5): error TS2322: Type 'boolean' is not assignable to type 'E'.
 tests/cases/conformance/types/primitives/boolean/invalidBooleanAssignments.ts(12,5): error TS2322: Type 'boolean' is not assignable to type 'C'.
-  Property 'foo' is missing in type 'Boolean'.
 tests/cases/conformance/types/primitives/boolean/invalidBooleanAssignments.ts(15,5): error TS2322: Type 'boolean' is not assignable to type 'I'.
-  Property 'bar' is missing in type 'Boolean'.
 tests/cases/conformance/types/primitives/boolean/invalidBooleanAssignments.ts(17,5): error TS2322: Type 'boolean' is not assignable to type '() => string'.
 tests/cases/conformance/types/primitives/boolean/invalidBooleanAssignments.ts(21,1): error TS2364: Invalid left-hand side of assignment expression.
 tests/cases/conformance/types/primitives/boolean/invalidBooleanAssignments.ts(24,5): error TS2322: Type 'boolean' is not assignable to type 'T'.
@@ -35,13 +33,11 @@ tests/cases/conformance/types/primitives/boolean/invalidBooleanAssignments.ts(26
     var f: C = x;
         ~
 !!! error TS2322: Type 'boolean' is not assignable to type 'C'.
-!!! error TS2322:   Property 'foo' is missing in type 'Boolean'.
     
     interface I { bar: string }
     var g: I = x;
         ~
 !!! error TS2322: Type 'boolean' is not assignable to type 'I'.
-!!! error TS2322:   Property 'bar' is missing in type 'Boolean'.
     
     var h: { (): string } = x;
         ~
diff --git a/tests/baselines/reference/invalidNumberAssignments.errors.txt b/tests/baselines/reference/invalidNumberAssignments.errors.txt
index 7eb5e6cb89..fd8acaba03 100644
--- a/tests/baselines/reference/invalidNumberAssignments.errors.txt
+++ b/tests/baselines/reference/invalidNumberAssignments.errors.txt
@@ -2,13 +2,9 @@ tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(3,5)
 tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(4,5): error TS2322: Type 'number' is not assignable to type 'string'.
 tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(5,5): error TS2322: Type 'number' is not assignable to type 'void'.
 tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(9,5): error TS2322: Type 'number' is not assignable to type 'C'.
-  Property 'foo' is missing in type 'Number'.
 tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(12,5): error TS2322: Type 'number' is not assignable to type 'I'.
-  Property 'bar' is missing in type 'Number'.
 tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(14,5): error TS2322: Type 'number' is not assignable to type '{ baz: string; }'.
-  Property 'baz' is missing in type 'Number'.
 tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(15,5): error TS2322: Type 'number' is not assignable to type '{ 0: number; }'.
-  Property '0' is missing in type 'Number'.
 tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(18,1): error TS2364: Invalid left-hand side of assignment expression.
 tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(21,5): error TS2322: Type 'number' is not assignable to type 'T'.
 tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(23,1): error TS2364: Invalid left-hand side of assignment expression.
@@ -32,22 +28,18 @@ tests/cases/conformance/types/primitives/number/invalidNumberAssignments.ts(23,1
     var e: C = x;
         ~
 !!! error TS2322: Type 'number' is not assignable to type 'C'.
-!!! error TS2322:   Property 'foo' is missing in type 'Number'.
     
     interface I { bar: string; }
     var f: I = x;
         ~
 !!! error TS2322: Type 'number' is not assignable to type 'I'.
-!!! error TS2322:   Property 'bar' is missing in type 'Number'.
     
     var g: { baz: string } = 1;
         ~
 !!! error TS2322: Type 'number' is not assignable to type '{ baz: string; }'.
-!!! error TS2322:   Property 'baz' is missing in type 'Number'.
     var g2: { 0: number } = 1;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '{ 0: number; }'.
-!!! error TS2322:   Property '0' is missing in type 'Number'.
     
     module M { export var x = 1; }
     M = x;
diff --git a/tests/baselines/reference/invalidStringAssignments.errors.txt b/tests/baselines/reference/invalidStringAssignments.errors.txt
index e67106bef9..d7ac2134dc 100644
--- a/tests/baselines/reference/invalidStringAssignments.errors.txt
+++ b/tests/baselines/reference/invalidStringAssignments.errors.txt
@@ -2,13 +2,9 @@ tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(3,5)
 tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(4,5): error TS2322: Type 'string' is not assignable to type 'number'.
 tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(5,5): error TS2322: Type 'string' is not assignable to type 'void'.
 tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(9,5): error TS2322: Type 'string' is not assignable to type 'C'.
-  Property 'foo' is missing in type 'String'.
 tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(12,5): error TS2322: Type 'string' is not assignable to type 'I'.
-  Property 'bar' is missing in type 'String'.
 tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(14,5): error TS2322: Type 'number' is not assignable to type '{ baz: string; }'.
-  Property 'baz' is missing in type 'Number'.
 tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(15,5): error TS2322: Type 'number' is not assignable to type '{ 0: number; }'.
-  Property '0' is missing in type 'Number'.
 tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(18,1): error TS2364: Invalid left-hand side of assignment expression.
 tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(21,5): error TS2322: Type 'string' is not assignable to type 'T'.
 tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(23,1): error TS2364: Invalid left-hand side of assignment expression.
@@ -33,22 +29,18 @@ tests/cases/conformance/types/primitives/string/invalidStringAssignments.ts(26,5
     var e: C = x;
         ~
 !!! error TS2322: Type 'string' is not assignable to type 'C'.
-!!! error TS2322:   Property 'foo' is missing in type 'String'.
     
     interface I { bar: string; }
     var f: I = x;
         ~
 !!! error TS2322: Type 'string' is not assignable to type 'I'.
-!!! error TS2322:   Property 'bar' is missing in type 'String'.
     
     var g: { baz: string } = 1;
         ~
 !!! error TS2322: Type 'number' is not assignable to type '{ baz: string; }'.
-!!! error TS2322:   Property 'baz' is missing in type 'Number'.
     var g2: { 0: number } = 1;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '{ 0: number; }'.
-!!! error TS2322:   Property '0' is missing in type 'Number'.
     
     module M { export var x = 1; }
     M = x;
diff --git a/tests/baselines/reference/invalidVoidAssignments.errors.txt b/tests/baselines/reference/invalidVoidAssignments.errors.txt
index 9c6be972d3..af8cec6267 100644
--- a/tests/baselines/reference/invalidVoidAssignments.errors.txt
+++ b/tests/baselines/reference/invalidVoidAssignments.errors.txt
@@ -4,9 +4,7 @@ tests/cases/conformance/types/primitives/void/invalidVoidAssignments.ts(5,5): er
 tests/cases/conformance/types/primitives/void/invalidVoidAssignments.ts(9,5): error TS2322: Type 'void' is not assignable to type 'C'.
 tests/cases/conformance/types/primitives/void/invalidVoidAssignments.ts(12,5): error TS2322: Type 'void' is not assignable to type 'I'.
 tests/cases/conformance/types/primitives/void/invalidVoidAssignments.ts(14,5): error TS2322: Type 'number' is not assignable to type '{ baz: string; }'.
-  Property 'baz' is missing in type 'Number'.
 tests/cases/conformance/types/primitives/void/invalidVoidAssignments.ts(15,5): error TS2322: Type 'number' is not assignable to type '{ 0: number; }'.
-  Property '0' is missing in type 'Number'.
 tests/cases/conformance/types/primitives/void/invalidVoidAssignments.ts(18,1): error TS2364: Invalid left-hand side of assignment expression.
 tests/cases/conformance/types/primitives/void/invalidVoidAssignments.ts(21,5): error TS2322: Type 'void' is not assignable to type 'T'.
 tests/cases/conformance/types/primitives/void/invalidVoidAssignments.ts(23,1): error TS2364: Invalid left-hand side of assignment expression.
@@ -42,11 +40,9 @@ tests/cases/conformance/types/primitives/void/invalidVoidAssignments.ts(29,1): e
     var g: { baz: string } = 1;
         ~
 !!! error TS2322: Type 'number' is not assignable to type '{ baz: string; }'.
-!!! error TS2322:   Property 'baz' is missing in type 'Number'.
     var g2: { 0: number } = 1;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '{ 0: number; }'.
-!!! error TS2322:   Property '0' is missing in type 'Number'.
     
     module M { export var x = 1; }
     M = x;
diff --git a/tests/baselines/reference/jsFileCompilationTypeAliasSyntax.errors.txt b/tests/baselines/reference/jsFileCompilationTypeAliasSyntax.errors.txt
index bc4d8e903a..2b5112e1ce 100644
--- a/tests/baselines/reference/jsFileCompilationTypeAliasSyntax.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationTypeAliasSyntax.errors.txt
@@ -1,9 +1,9 @@
 error TS5055: Cannot write file 'tests/cases/compiler/a.js' because it would overwrite input file.
-tests/cases/compiler/a.js(1,1): error TS8008: 'type aliases' can only be used in a .ts file.
+tests/cases/compiler/a.js(1,6): error TS8008: 'type aliases' can only be used in a .ts file.
 
 
 !!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' because it would overwrite input file.
 ==== tests/cases/compiler/a.js (1 errors) ====
     type a = b;
-    ~~~~~~~~~~~
+         ~
 !!! error TS8008: 'type aliases' can only be used in a .ts file.
\ No newline at end of file
diff --git a/tests/baselines/reference/lastPropertyInLiteralWins.errors.txt b/tests/baselines/reference/lastPropertyInLiteralWins.errors.txt
index d503f59c60..ab784eae39 100644
--- a/tests/baselines/reference/lastPropertyInLiteralWins.errors.txt
+++ b/tests/baselines/reference/lastPropertyInLiteralWins.errors.txt
@@ -1,6 +1,8 @@
 tests/cases/compiler/lastPropertyInLiteralWins.ts(7,6): error TS2345: Argument of type '{ thunk: (num: number) => void; }' is not assignable to parameter of type 'Thing'.
   Types of property 'thunk' are incompatible.
     Type '(num: number) => void' is not assignable to type '(str: string) => void'.
+      Types of parameters 'num' and 'str' are incompatible.
+        Type 'number' is not assignable to type 'string'.
 tests/cases/compiler/lastPropertyInLiteralWins.ts(8,5): error TS2300: Duplicate identifier 'thunk'.
 tests/cases/compiler/lastPropertyInLiteralWins.ts(9,5): error TS2300: Duplicate identifier 'thunk'.
 tests/cases/compiler/lastPropertyInLiteralWins.ts(13,5): error TS2300: Duplicate identifier 'thunk'.
@@ -29,6 +31,8 @@ tests/cases/compiler/lastPropertyInLiteralWins.ts(14,5): error TS2300: Duplicate
 !!! error TS2345: Argument of type '{ thunk: (num: number) => void; }' is not assignable to parameter of type 'Thing'.
 !!! error TS2345:   Types of property 'thunk' are incompatible.
 !!! error TS2345:     Type '(num: number) => void' is not assignable to type '(str: string) => void'.
+!!! error TS2345:       Types of parameters 'num' and 'str' are incompatible.
+!!! error TS2345:         Type 'number' is not assignable to type 'string'.
     
     test({ // Should be OK.  Last 'thunk' is of correct type
         thunk: (num: number) => {},
diff --git a/tests/baselines/reference/maxConstraints.errors.txt b/tests/baselines/reference/maxConstraints.errors.txt
index 03e7158f72..a7d07a5b5f 100644
--- a/tests/baselines/reference/maxConstraints.errors.txt
+++ b/tests/baselines/reference/maxConstraints.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/compiler/maxConstraints.ts(8,22): error TS2345: Argument of type 'number' is not assignable to parameter of type 'Comparable<number>'.
-  Property 'compareTo' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/maxConstraints.ts (1 errors) ====
@@ -12,5 +11,4 @@ tests/cases/compiler/maxConstraints.ts(8,22): error TS2345: Argument of type 'nu
     var max2: Comparer = (x, y) => { return (x.compareTo(y) > 0) ? x : y };
     var maxResult = max2(1, 2);
                          ~
-!!! error TS2345: Argument of type 'number' is not assignable to parameter of type 'Comparable<number>'.
-!!! error TS2345:   Property 'compareTo' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2345: Argument of type 'number' is not assignable to parameter of type 'Comparable<number>'.
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationCollidingNamesInAugmentation1.errors.txt b/tests/baselines/reference/moduleAugmentationCollidingNamesInAugmentation1.errors.txt
new file mode 100644
index 0000000000..8e1bc337b3
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationCollidingNamesInAugmentation1.errors.txt
@@ -0,0 +1,40 @@
+tests/cases/compiler/map1.ts(7,15): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/map2.ts(6,15): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+
+
+==== tests/cases/compiler/map1.ts (1 errors) ====
+    
+    import { Observable } from "./observable"
+    
+    (<any>Observable.prototype).map = function() { }
+    
+    declare module "./observable" {
+        interface I {x0}
+                  ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+    }
+    
+==== tests/cases/compiler/map2.ts (1 errors) ====
+    import { Observable } from "./observable"
+    
+    (<any>Observable.prototype).map = function() { }
+    
+    declare module "./observable" {
+        interface I {x1}
+                  ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+    }
+    
+    
+==== tests/cases/compiler/observable.ts (0 errors) ====
+    export declare class Observable<T> {
+        filter(pred: (e:T) => boolean): Observable<T>;
+    }
+    
+==== tests/cases/compiler/main.ts (0 errors) ====
+    import { Observable } from "./observable"
+    import "./map1";
+    import "./map2";
+    
+    let x: Observable<number>;
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationCollidingNamesInAugmentation1.js b/tests/baselines/reference/moduleAugmentationCollidingNamesInAugmentation1.js
new file mode 100644
index 0000000000..60ba221734
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationCollidingNamesInAugmentation1.js
@@ -0,0 +1,75 @@
+//// [tests/cases/compiler/moduleAugmentationCollidingNamesInAugmentation1.ts] ////
+
+//// [map1.ts]
+
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface I {x0}
+}
+
+//// [map2.ts]
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface I {x1}
+}
+
+
+//// [observable.ts]
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+//// [main.ts]
+import { Observable } from "./observable"
+import "./map1";
+import "./map2";
+
+let x: Observable<number>;
+
+
+//// [observable.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+});
+//// [map1.js]
+define(["require", "exports", "./observable"], function (require, exports, observable_1) {
+    "use strict";
+    observable_1.Observable.prototype.map = function () { };
+});
+//// [map2.js]
+define(["require", "exports", "./observable"], function (require, exports, observable_1) {
+    "use strict";
+    observable_1.Observable.prototype.map = function () { };
+});
+//// [main.js]
+define(["require", "exports", "./map1", "./map2"], function (require, exports) {
+    "use strict";
+    var x;
+});
+
+
+//// [observable.d.ts]
+export declare class Observable<T> {
+    filter(pred: (e: T) => boolean): Observable<T>;
+}
+//// [map1.d.ts]
+declare module "./observable" {
+    interface I {
+        x0: any;
+    }
+}
+export {};
+//// [map2.d.ts]
+declare module "./observable" {
+    interface I {
+        x1: any;
+    }
+}
+export {};
+//// [main.d.ts]
diff --git a/tests/baselines/reference/moduleAugmentationDeclarationEmit1.js b/tests/baselines/reference/moduleAugmentationDeclarationEmit1.js
new file mode 100644
index 0000000000..589d0f506e
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationDeclarationEmit1.js
@@ -0,0 +1,68 @@
+//// [tests/cases/compiler/moduleAugmentationDeclarationEmit1.ts] ////
+
+//// [map.ts]
+
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: number;
+    }
+}
+
+//// [observable.ts]
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+export namespace Observable {
+    let someValue: number;
+}
+
+
+//// [main.ts]
+import { Observable } from "./observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
+
+//// [observable.js]
+"use strict";
+var Observable;
+(function (Observable) {
+    var someValue;
+})(Observable = exports.Observable || (exports.Observable = {}));
+//// [map.js]
+"use strict";
+var observable_1 = require("./observable");
+observable_1.Observable.prototype.map = function () { };
+//// [main.js]
+"use strict";
+require("./map");
+var x;
+var y = x.map(function (x) { return x + 1; });
+
+
+//// [observable.d.ts]
+export declare class Observable<T> {
+    filter(pred: (e: T) => boolean): Observable<T>;
+}
+export declare namespace Observable {
+}
+//// [map.d.ts]
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e: T) => U): Observable<U>;
+    }
+    namespace Observable {
+        let someAnotherValue: number;
+    }
+}
+export {};
+//// [main.d.ts]
diff --git a/tests/baselines/reference/moduleAugmentationDeclarationEmit1.symbols b/tests/baselines/reference/moduleAugmentationDeclarationEmit1.symbols
new file mode 100644
index 0000000000..eca44ec774
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationDeclarationEmit1.symbols
@@ -0,0 +1,73 @@
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "./observable"
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+
+(<any>Observable.prototype).map = function() { }
+>Observable.prototype : Symbol(Observable.prototype)
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+>prototype : Symbol(Observable.prototype)
+
+declare module "./observable" {
+    interface Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : Symbol(map, Decl(map.ts, 6, 29))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>proj : Symbol(proj, Decl(map.ts, 7, 15))
+>e : Symbol(e, Decl(map.ts, 7, 22))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+    }
+    namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+
+        let someAnotherValue: number;
+>someAnotherValue : Symbol(someAnotherValue, Decl(map.ts, 10, 11))
+    }
+}
+
+=== tests/cases/compiler/observable.ts ===
+export declare class Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+
+    filter(pred: (e:T) => boolean): Observable<T>;
+>filter : Symbol(filter, Decl(observable.ts, 0, 36))
+>pred : Symbol(pred, Decl(observable.ts, 1, 11))
+>e : Symbol(e, Decl(observable.ts, 1, 18))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+}
+
+export namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+
+    let someValue: number;
+>someValue : Symbol(someValue, Decl(observable.ts, 5, 7))
+}
+
+
+=== tests/cases/compiler/main.ts ===
+import { Observable } from "./observable"
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+
+import "./map";
+
+let x: Observable<number>;
+>x : Symbol(x, Decl(main.ts, 3, 3))
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+
+let y = x.map(x => x + 1);
+>y : Symbol(y, Decl(main.ts, 4, 3))
+>x.map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 3, 3))
+>map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 4, 14))
+>x : Symbol(x, Decl(main.ts, 4, 14))
+
diff --git a/tests/baselines/reference/moduleAugmentationDeclarationEmit1.types b/tests/baselines/reference/moduleAugmentationDeclarationEmit1.types
new file mode 100644
index 0000000000..fad835029c
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationDeclarationEmit1.types
@@ -0,0 +1,83 @@
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "./observable"
+>Observable : typeof Observable
+
+(<any>Observable.prototype).map = function() { }
+>(<any>Observable.prototype).map = function() { } : () => void
+>(<any>Observable.prototype).map : any
+>(<any>Observable.prototype) : any
+><any>Observable.prototype : any
+>Observable.prototype : Observable<any>
+>Observable : typeof Observable
+>prototype : Observable<any>
+>map : any
+>function() { } : () => void
+
+declare module "./observable" {
+    interface Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : <U>(proj: (e: T) => U) => Observable<U>
+>U : U
+>proj : (e: T) => U
+>e : T
+>T : T
+>U : U
+>Observable : Observable<T>
+>U : U
+    }
+    namespace Observable {
+>Observable : typeof Observable
+
+        let someAnotherValue: number;
+>someAnotherValue : number
+    }
+}
+
+=== tests/cases/compiler/observable.ts ===
+export declare class Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+    filter(pred: (e:T) => boolean): Observable<T>;
+>filter : (pred: (e: T) => boolean) => Observable<T>
+>pred : (e: T) => boolean
+>e : T
+>T : T
+>Observable : Observable<T>
+>T : T
+}
+
+export namespace Observable {
+>Observable : typeof Observable
+
+    let someValue: number;
+>someValue : number
+}
+
+
+=== tests/cases/compiler/main.ts ===
+import { Observable } from "./observable"
+>Observable : typeof Observable
+
+import "./map";
+
+let x: Observable<number>;
+>x : Observable<number>
+>Observable : Observable<T>
+
+let y = x.map(x => x + 1);
+>y : Observable<number>
+>x.map(x => x + 1) : Observable<number>
+>x.map : <U>(proj: (e: number) => U) => Observable<U>
+>x : Observable<number>
+>map : <U>(proj: (e: number) => U) => Observable<U>
+>x => x + 1 : (x: number) => number
+>x : number
+>x + 1 : number
+>x : number
+>1 : number
+
diff --git a/tests/baselines/reference/moduleAugmentationDeclarationEmit2.js b/tests/baselines/reference/moduleAugmentationDeclarationEmit2.js
new file mode 100644
index 0000000000..d8fd65a146
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationDeclarationEmit2.js
@@ -0,0 +1,73 @@
+//// [tests/cases/compiler/moduleAugmentationDeclarationEmit2.ts] ////
+
+//// [map.ts]
+
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: string;
+    }
+}
+
+//// [observable.ts]
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+export namespace Observable {
+    export let someValue: number;
+}
+
+
+//// [main.ts]
+import { Observable } from "./observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
+let z1 = Observable.someValue.toFixed();
+let z2 = Observable.someAnotherValue.toLowerCase();
+
+//// [observable.js]
+"use strict";
+var Observable;
+(function (Observable) {
+})(Observable = exports.Observable || (exports.Observable = {}));
+//// [map.js]
+"use strict";
+var observable_1 = require("./observable");
+observable_1.Observable.prototype.map = function () { };
+//// [main.js]
+"use strict";
+var observable_1 = require("./observable");
+require("./map");
+var x;
+var y = x.map(function (x) { return x + 1; });
+var z1 = observable_1.Observable.someValue.toFixed();
+var z2 = observable_1.Observable.someAnotherValue.toLowerCase();
+
+
+//// [observable.d.ts]
+export declare class Observable<T> {
+    filter(pred: (e: T) => boolean): Observable<T>;
+}
+export declare namespace Observable {
+    let someValue: number;
+}
+//// [map.d.ts]
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e: T) => U): Observable<U>;
+    }
+    namespace Observable {
+        let someAnotherValue: string;
+    }
+}
+export {};
+//// [main.d.ts]
diff --git a/tests/baselines/reference/moduleAugmentationDeclarationEmit2.symbols b/tests/baselines/reference/moduleAugmentationDeclarationEmit2.symbols
new file mode 100644
index 0000000000..d0f25f693f
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationDeclarationEmit2.symbols
@@ -0,0 +1,89 @@
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "./observable"
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+
+(<any>Observable.prototype).map = function() { }
+>Observable.prototype : Symbol(Observable.prototype)
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+>prototype : Symbol(Observable.prototype)
+
+declare module "./observable" {
+    interface Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : Symbol(map, Decl(map.ts, 6, 29))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>proj : Symbol(proj, Decl(map.ts, 7, 15))
+>e : Symbol(e, Decl(map.ts, 7, 22))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+    }
+    namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+
+        let someAnotherValue: string;
+>someAnotherValue : Symbol(someAnotherValue, Decl(map.ts, 10, 11))
+    }
+}
+
+=== tests/cases/compiler/observable.ts ===
+export declare class Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+
+    filter(pred: (e:T) => boolean): Observable<T>;
+>filter : Symbol(filter, Decl(observable.ts, 0, 36))
+>pred : Symbol(pred, Decl(observable.ts, 1, 11))
+>e : Symbol(e, Decl(observable.ts, 1, 18))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+}
+
+export namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+
+    export let someValue: number;
+>someValue : Symbol(someValue, Decl(observable.ts, 5, 14))
+}
+
+
+=== tests/cases/compiler/main.ts ===
+import { Observable } from "./observable"
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+
+import "./map";
+
+let x: Observable<number>;
+>x : Symbol(x, Decl(main.ts, 3, 3))
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+
+let y = x.map(x => x + 1);
+>y : Symbol(y, Decl(main.ts, 4, 3))
+>x.map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 3, 3))
+>map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 4, 14))
+>x : Symbol(x, Decl(main.ts, 4, 14))
+
+let z1 = Observable.someValue.toFixed();
+>z1 : Symbol(z1, Decl(main.ts, 5, 3))
+>Observable.someValue.toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+>Observable.someValue : Symbol(Observable.someValue, Decl(observable.ts, 5, 14))
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+>someValue : Symbol(Observable.someValue, Decl(observable.ts, 5, 14))
+>toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+
+let z2 = Observable.someAnotherValue.toLowerCase();
+>z2 : Symbol(z2, Decl(main.ts, 6, 3))
+>Observable.someAnotherValue.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>Observable.someAnotherValue : Symbol(Observable.someAnotherValue, Decl(map.ts, 10, 11))
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+>someAnotherValue : Symbol(Observable.someAnotherValue, Decl(map.ts, 10, 11))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
diff --git a/tests/baselines/reference/moduleAugmentationDeclarationEmit2.types b/tests/baselines/reference/moduleAugmentationDeclarationEmit2.types
new file mode 100644
index 0000000000..85e4ead2ac
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationDeclarationEmit2.types
@@ -0,0 +1,101 @@
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "./observable"
+>Observable : typeof Observable
+
+(<any>Observable.prototype).map = function() { }
+>(<any>Observable.prototype).map = function() { } : () => void
+>(<any>Observable.prototype).map : any
+>(<any>Observable.prototype) : any
+><any>Observable.prototype : any
+>Observable.prototype : Observable<any>
+>Observable : typeof Observable
+>prototype : Observable<any>
+>map : any
+>function() { } : () => void
+
+declare module "./observable" {
+    interface Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : <U>(proj: (e: T) => U) => Observable<U>
+>U : U
+>proj : (e: T) => U
+>e : T
+>T : T
+>U : U
+>Observable : Observable<T>
+>U : U
+    }
+    namespace Observable {
+>Observable : typeof Observable
+
+        let someAnotherValue: string;
+>someAnotherValue : string
+    }
+}
+
+=== tests/cases/compiler/observable.ts ===
+export declare class Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+    filter(pred: (e:T) => boolean): Observable<T>;
+>filter : (pred: (e: T) => boolean) => Observable<T>
+>pred : (e: T) => boolean
+>e : T
+>T : T
+>Observable : Observable<T>
+>T : T
+}
+
+export namespace Observable {
+>Observable : typeof Observable
+
+    export let someValue: number;
+>someValue : number
+}
+
+
+=== tests/cases/compiler/main.ts ===
+import { Observable } from "./observable"
+>Observable : typeof Observable
+
+import "./map";
+
+let x: Observable<number>;
+>x : Observable<number>
+>Observable : Observable<T>
+
+let y = x.map(x => x + 1);
+>y : Observable<number>
+>x.map(x => x + 1) : Observable<number>
+>x.map : <U>(proj: (e: number) => U) => Observable<U>
+>x : Observable<number>
+>map : <U>(proj: (e: number) => U) => Observable<U>
+>x => x + 1 : (x: number) => number
+>x : number
+>x + 1 : number
+>x : number
+>1 : number
+
+let z1 = Observable.someValue.toFixed();
+>z1 : string
+>Observable.someValue.toFixed() : string
+>Observable.someValue.toFixed : (fractionDigits?: number) => string
+>Observable.someValue : number
+>Observable : typeof Observable
+>someValue : number
+>toFixed : (fractionDigits?: number) => string
+
+let z2 = Observable.someAnotherValue.toLowerCase();
+>z2 : string
+>Observable.someAnotherValue.toLowerCase() : string
+>Observable.someAnotherValue.toLowerCase : () => string
+>Observable.someAnotherValue : string
+>Observable : typeof Observable
+>someAnotherValue : string
+>toLowerCase : () => string
+
diff --git a/tests/baselines/reference/moduleAugmentationDisallowedExtensions.errors.txt b/tests/baselines/reference/moduleAugmentationDisallowedExtensions.errors.txt
new file mode 100644
index 0000000000..571b288c04
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationDisallowedExtensions.errors.txt
@@ -0,0 +1,117 @@
+tests/cases/compiler/x.ts(7,9): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(8,9): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(9,11): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(10,10): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(10,14): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(10,23): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(10,38): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(10,43): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(10,48): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(11,15): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(12,15): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(15,11): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(16,14): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(17,10): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/x.ts(18,5): error TS2667: Imports are not permitted in module augmentations. Consider moving them to the enclosing external module.
+tests/cases/compiler/x.ts(18,26): error TS2307: Cannot find module './x0'.
+tests/cases/compiler/x.ts(19,5): error TS2667: Imports are not permitted in module augmentations. Consider moving them to the enclosing external module.
+tests/cases/compiler/x.ts(19,21): error TS2307: Cannot find module './x0'.
+tests/cases/compiler/x.ts(20,5): error TS2666: Exports and export assignments are not permitted in module augmentations.
+tests/cases/compiler/x.ts(20,19): error TS2307: Cannot find module './x0'.
+tests/cases/compiler/x.ts(21,5): error TS2666: Exports and export assignments are not permitted in module augmentations.
+tests/cases/compiler/x.ts(21,21): error TS2307: Cannot find module './x0'.
+tests/cases/compiler/x.ts(25,5): error TS2666: Exports and export assignments are not permitted in module augmentations.
+
+
+==== tests/cases/compiler/x0.ts (0 errors) ====
+    
+    export let a = 1;
+    
+==== tests/cases/compiler/x.ts (23 errors) ====
+    
+    namespace N1 {
+        export let x = 1;
+    }
+    
+    declare module "./observable" {
+        var x: number;
+            ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        let y: number;
+            ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        const z: number;
+              ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        let {x1, y1, z0: {n}, z1: {arr: [el1, el2, el3]}}: {x1: number, y1: string, z0: {n: number}, z1: {arr: number[]} }
+             ~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                 ~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                          ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                                         ~~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                                              ~~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                                                   ~~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        interface A { x }
+                  ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        namespace N {
+                  ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+            export class C {}
+        }
+        class Cls {}
+              ~~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        function foo(): number;
+                 ~~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        type T = number;
+             ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        import * as all from "./x0";
+        ~~~~~~
+!!! error TS2667: Imports are not permitted in module augmentations. Consider moving them to the enclosing external module.
+                             ~~~~~~
+!!! error TS2307: Cannot find module './x0'.
+        import {a} from "./x0";
+        ~~~~~~
+!!! error TS2667: Imports are not permitted in module augmentations. Consider moving them to the enclosing external module.
+                        ~~~~~~
+!!! error TS2307: Cannot find module './x0'.
+        export * from "./x0";
+        ~~~~~~
+!!! error TS2666: Exports and export assignments are not permitted in module augmentations.
+                      ~~~~~~
+!!! error TS2307: Cannot find module './x0'.
+        export {a} from "./x0";
+        ~~~~~~
+!!! error TS2666: Exports and export assignments are not permitted in module augmentations.
+                        ~~~~~~
+!!! error TS2307: Cannot find module './x0'.
+    }
+    
+    declare module "./test" {
+        export = N1;
+        ~~~~~~
+!!! error TS2666: Exports and export assignments are not permitted in module augmentations.
+    }
+    export {}
+    
+==== tests/cases/compiler/observable.ts (0 errors) ====
+    export declare class Observable<T> {
+        filter(pred: (e:T) => boolean): Observable<T>;
+    }
+    export var x = 1;
+    
+==== tests/cases/compiler/test.ts (0 errors) ====
+    export let b = 1;
+    
+==== tests/cases/compiler/main.ts (0 errors) ====
+    import { Observable } from "./observable"
+    import "./x";
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationDisallowedExtensions.js b/tests/baselines/reference/moduleAugmentationDisallowedExtensions.js
new file mode 100644
index 0000000000..8c497d63c4
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationDisallowedExtensions.js
@@ -0,0 +1,67 @@
+//// [tests/cases/compiler/moduleAugmentationDisallowedExtensions.ts] ////
+
+//// [x0.ts]
+
+export let a = 1;
+
+//// [x.ts]
+
+namespace N1 {
+    export let x = 1;
+}
+
+declare module "./observable" {
+    var x: number;
+    let y: number;
+    const z: number;
+    let {x1, y1, z0: {n}, z1: {arr: [el1, el2, el3]}}: {x1: number, y1: string, z0: {n: number}, z1: {arr: number[]} }
+    interface A { x }
+    namespace N {
+        export class C {}
+    }
+    class Cls {}
+    function foo(): number;
+    type T = number;
+    import * as all from "./x0";
+    import {a} from "./x0";
+    export * from "./x0";
+    export {a} from "./x0";
+}
+
+declare module "./test" {
+    export = N1;
+}
+export {}
+
+//// [observable.ts]
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+export var x = 1;
+
+//// [test.ts]
+export let b = 1;
+
+//// [main.ts]
+import { Observable } from "./observable"
+import "./x";
+
+
+//// [x0.js]
+"use strict";
+exports.a = 1;
+//// [x.js]
+"use strict";
+var N1;
+(function (N1) {
+    N1.x = 1;
+})(N1 || (N1 = {}));
+//// [observable.js]
+"use strict";
+exports.x = 1;
+//// [test.js]
+"use strict";
+exports.b = 1;
+//// [main.js]
+"use strict";
+require("./x");
diff --git a/tests/baselines/reference/moduleAugmentationExtendAmbientModule1.js b/tests/baselines/reference/moduleAugmentationExtendAmbientModule1.js
new file mode 100644
index 0000000000..0a8b1b0b4b
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendAmbientModule1.js
@@ -0,0 +1,45 @@
+//// [tests/cases/compiler/moduleAugmentationExtendAmbientModule1.ts] ////
+
+//// [map.ts]
+
+import { Observable } from "observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: number;
+    }
+}
+
+//// [observable.d.ts]
+declare module "observable" {
+    class Observable<T> {
+        filter(pred: (e:T) => boolean): Observable<T>;
+    }
+    namespace Observable {
+        let someValue: number;
+    }
+}
+
+//// [main.ts]
+
+/// <reference path="observable.d.ts"/>
+import { Observable } from "observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
+
+//// [map.js]
+"use strict";
+var observable_1 = require("observable");
+observable_1.Observable.prototype.map = function () { };
+//// [main.js]
+"use strict";
+require("./map");
+var x;
+var y = x.map(function (x) { return x + 1; });
diff --git a/tests/baselines/reference/moduleAugmentationExtendAmbientModule1.symbols b/tests/baselines/reference/moduleAugmentationExtendAmbientModule1.symbols
new file mode 100644
index 0000000000..a471651da0
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendAmbientModule1.symbols
@@ -0,0 +1,75 @@
+=== tests/cases/compiler/main.ts ===
+
+/// <reference path="observable.d.ts"/>
+import { Observable } from "observable"
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+
+import "./map";
+
+let x: Observable<number>;
+>x : Symbol(x, Decl(main.ts, 5, 3))
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+
+let y = x.map(x => x + 1);
+>y : Symbol(y, Decl(main.ts, 6, 3))
+>x.map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 5, 3))
+>map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 6, 14))
+>x : Symbol(x, Decl(main.ts, 6, 14))
+
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "observable"
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+
+(<any>Observable.prototype).map = function() { }
+>Observable.prototype : Symbol(Observable.prototype)
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+>prototype : Symbol(Observable.prototype)
+
+declare module "observable" {
+    interface Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.d.ts, 1, 21), Decl(map.ts, 6, 25))
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : Symbol(map, Decl(map.ts, 6, 29))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>proj : Symbol(proj, Decl(map.ts, 7, 15))
+>e : Symbol(e, Decl(map.ts, 7, 22))
+>T : Symbol(T, Decl(observable.d.ts, 1, 21), Decl(map.ts, 6, 25))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+    }
+    namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+
+        let someAnotherValue: number;
+>someAnotherValue : Symbol(someAnotherValue, Decl(map.ts, 10, 11))
+    }
+}
+
+=== tests/cases/compiler/observable.d.ts ===
+declare module "observable" {
+    class Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.d.ts, 1, 21), Decl(map.ts, 6, 25))
+
+        filter(pred: (e:T) => boolean): Observable<T>;
+>filter : Symbol(filter, Decl(observable.d.ts, 1, 25))
+>pred : Symbol(pred, Decl(observable.d.ts, 2, 15))
+>e : Symbol(e, Decl(observable.d.ts, 2, 22))
+>T : Symbol(T, Decl(observable.d.ts, 1, 21), Decl(map.ts, 6, 25))
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.d.ts, 1, 21), Decl(map.ts, 6, 25))
+    }
+    namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+
+        let someValue: number;
+>someValue : Symbol(someValue, Decl(observable.d.ts, 5, 11))
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationExtendAmbientModule1.types b/tests/baselines/reference/moduleAugmentationExtendAmbientModule1.types
new file mode 100644
index 0000000000..e6ee79e358
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendAmbientModule1.types
@@ -0,0 +1,85 @@
+=== tests/cases/compiler/main.ts ===
+
+/// <reference path="observable.d.ts"/>
+import { Observable } from "observable"
+>Observable : typeof Observable
+
+import "./map";
+
+let x: Observable<number>;
+>x : Observable<number>
+>Observable : Observable<T>
+
+let y = x.map(x => x + 1);
+>y : Observable<number>
+>x.map(x => x + 1) : Observable<number>
+>x.map : <U>(proj: (e: number) => U) => Observable<U>
+>x : Observable<number>
+>map : <U>(proj: (e: number) => U) => Observable<U>
+>x => x + 1 : (x: number) => number
+>x : number
+>x + 1 : number
+>x : number
+>1 : number
+
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "observable"
+>Observable : typeof Observable
+
+(<any>Observable.prototype).map = function() { }
+>(<any>Observable.prototype).map = function() { } : () => void
+>(<any>Observable.prototype).map : any
+>(<any>Observable.prototype) : any
+><any>Observable.prototype : any
+>Observable.prototype : Observable<any>
+>Observable : typeof Observable
+>prototype : Observable<any>
+>map : any
+>function() { } : () => void
+
+declare module "observable" {
+    interface Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : <U>(proj: (e: T) => U) => Observable<U>
+>U : U
+>proj : (e: T) => U
+>e : T
+>T : T
+>U : U
+>Observable : Observable<T>
+>U : U
+    }
+    namespace Observable {
+>Observable : typeof Observable
+
+        let someAnotherValue: number;
+>someAnotherValue : number
+    }
+}
+
+=== tests/cases/compiler/observable.d.ts ===
+declare module "observable" {
+    class Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+        filter(pred: (e:T) => boolean): Observable<T>;
+>filter : (pred: (e: T) => boolean) => Observable<T>
+>pred : (e: T) => boolean
+>e : T
+>T : T
+>Observable : Observable<T>
+>T : T
+    }
+    namespace Observable {
+>Observable : typeof Observable
+
+        let someValue: number;
+>someValue : number
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationExtendAmbientModule2.js b/tests/baselines/reference/moduleAugmentationExtendAmbientModule2.js
new file mode 100644
index 0000000000..733f88e612
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendAmbientModule2.js
@@ -0,0 +1,65 @@
+//// [tests/cases/compiler/moduleAugmentationExtendAmbientModule2.ts] ////
+
+//// [map.ts]
+
+import { Observable } from "observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: string;
+    }
+}
+
+//// [observable.d.ts]
+declare module "observable" {
+    class Observable<T> {
+        filter(pred: (e:T) => boolean): Observable<T>;
+    }
+    namespace Observable {
+        export let someValue: number;
+    }
+}
+
+//// [main.ts]
+
+/// <reference path="observable.d.ts"/>
+import { Observable } from "observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
+let z1 = Observable.someValue.toFixed();
+let z2 = Observable.someAnotherValue.toLowerCase();
+
+//// [map.js]
+"use strict";
+var observable_1 = require("observable");
+observable_1.Observable.prototype.map = function () { };
+//// [main.js]
+"use strict";
+/// <reference path="observable.d.ts"/>
+var observable_1 = require("observable");
+require("./map");
+var x;
+var y = x.map(function (x) { return x + 1; });
+var z1 = observable_1.Observable.someValue.toFixed();
+var z2 = observable_1.Observable.someAnotherValue.toLowerCase();
+
+
+//// [map.d.ts]
+declare module "observable" {
+    interface Observable<T> {
+        map<U>(proj: (e: T) => U): Observable<U>;
+    }
+    namespace Observable {
+        let someAnotherValue: string;
+    }
+}
+export {};
+//// [main.d.ts]
+/// <reference path="observable.d.ts" />
diff --git a/tests/baselines/reference/moduleAugmentationExtendAmbientModule2.symbols b/tests/baselines/reference/moduleAugmentationExtendAmbientModule2.symbols
new file mode 100644
index 0000000000..f907f4d697
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendAmbientModule2.symbols
@@ -0,0 +1,91 @@
+=== tests/cases/compiler/main.ts ===
+
+/// <reference path="observable.d.ts"/>
+import { Observable } from "observable"
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+
+import "./map";
+
+let x: Observable<number>;
+>x : Symbol(x, Decl(main.ts, 5, 3))
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+
+let y = x.map(x => x + 1);
+>y : Symbol(y, Decl(main.ts, 6, 3))
+>x.map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 5, 3))
+>map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 6, 14))
+>x : Symbol(x, Decl(main.ts, 6, 14))
+
+let z1 = Observable.someValue.toFixed();
+>z1 : Symbol(z1, Decl(main.ts, 7, 3))
+>Observable.someValue.toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+>Observable.someValue : Symbol(Observable.someValue, Decl(observable.d.ts, 5, 18))
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+>someValue : Symbol(Observable.someValue, Decl(observable.d.ts, 5, 18))
+>toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+
+let z2 = Observable.someAnotherValue.toLowerCase();
+>z2 : Symbol(z2, Decl(main.ts, 8, 3))
+>Observable.someAnotherValue.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>Observable.someAnotherValue : Symbol(Observable.someAnotherValue, Decl(map.ts, 10, 11))
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+>someAnotherValue : Symbol(Observable.someAnotherValue, Decl(map.ts, 10, 11))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "observable"
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+
+(<any>Observable.prototype).map = function() { }
+>Observable.prototype : Symbol(Observable.prototype)
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+>prototype : Symbol(Observable.prototype)
+
+declare module "observable" {
+    interface Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.d.ts, 1, 21), Decl(map.ts, 6, 25))
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : Symbol(map, Decl(map.ts, 6, 29))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>proj : Symbol(proj, Decl(map.ts, 7, 15))
+>e : Symbol(e, Decl(map.ts, 7, 22))
+>T : Symbol(T, Decl(observable.d.ts, 1, 21), Decl(map.ts, 6, 25))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+    }
+    namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+
+        let someAnotherValue: string;
+>someAnotherValue : Symbol(someAnotherValue, Decl(map.ts, 10, 11))
+    }
+}
+
+=== tests/cases/compiler/observable.d.ts ===
+declare module "observable" {
+    class Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.d.ts, 1, 21), Decl(map.ts, 6, 25))
+
+        filter(pred: (e:T) => boolean): Observable<T>;
+>filter : Symbol(filter, Decl(observable.d.ts, 1, 25))
+>pred : Symbol(pred, Decl(observable.d.ts, 2, 15))
+>e : Symbol(e, Decl(observable.d.ts, 2, 22))
+>T : Symbol(T, Decl(observable.d.ts, 1, 21), Decl(map.ts, 6, 25))
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.d.ts, 1, 21), Decl(map.ts, 6, 25))
+    }
+    namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.d.ts, 0, 29), Decl(observable.d.ts, 3, 5), Decl(map.ts, 5, 29), Decl(map.ts, 8, 5))
+
+        export let someValue: number;
+>someValue : Symbol(someValue, Decl(observable.d.ts, 5, 18))
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationExtendAmbientModule2.types b/tests/baselines/reference/moduleAugmentationExtendAmbientModule2.types
new file mode 100644
index 0000000000..70288e48f0
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendAmbientModule2.types
@@ -0,0 +1,103 @@
+=== tests/cases/compiler/main.ts ===
+
+/// <reference path="observable.d.ts"/>
+import { Observable } from "observable"
+>Observable : typeof Observable
+
+import "./map";
+
+let x: Observable<number>;
+>x : Observable<number>
+>Observable : Observable<T>
+
+let y = x.map(x => x + 1);
+>y : Observable<number>
+>x.map(x => x + 1) : Observable<number>
+>x.map : <U>(proj: (e: number) => U) => Observable<U>
+>x : Observable<number>
+>map : <U>(proj: (e: number) => U) => Observable<U>
+>x => x + 1 : (x: number) => number
+>x : number
+>x + 1 : number
+>x : number
+>1 : number
+
+let z1 = Observable.someValue.toFixed();
+>z1 : string
+>Observable.someValue.toFixed() : string
+>Observable.someValue.toFixed : (fractionDigits?: number) => string
+>Observable.someValue : number
+>Observable : typeof Observable
+>someValue : number
+>toFixed : (fractionDigits?: number) => string
+
+let z2 = Observable.someAnotherValue.toLowerCase();
+>z2 : string
+>Observable.someAnotherValue.toLowerCase() : string
+>Observable.someAnotherValue.toLowerCase : () => string
+>Observable.someAnotherValue : string
+>Observable : typeof Observable
+>someAnotherValue : string
+>toLowerCase : () => string
+
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "observable"
+>Observable : typeof Observable
+
+(<any>Observable.prototype).map = function() { }
+>(<any>Observable.prototype).map = function() { } : () => void
+>(<any>Observable.prototype).map : any
+>(<any>Observable.prototype) : any
+><any>Observable.prototype : any
+>Observable.prototype : Observable<any>
+>Observable : typeof Observable
+>prototype : Observable<any>
+>map : any
+>function() { } : () => void
+
+declare module "observable" {
+    interface Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : <U>(proj: (e: T) => U) => Observable<U>
+>U : U
+>proj : (e: T) => U
+>e : T
+>T : T
+>U : U
+>Observable : Observable<T>
+>U : U
+    }
+    namespace Observable {
+>Observable : typeof Observable
+
+        let someAnotherValue: string;
+>someAnotherValue : string
+    }
+}
+
+=== tests/cases/compiler/observable.d.ts ===
+declare module "observable" {
+    class Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+        filter(pred: (e:T) => boolean): Observable<T>;
+>filter : (pred: (e: T) => boolean) => Observable<T>
+>pred : (e: T) => boolean
+>e : T
+>T : T
+>Observable : Observable<T>
+>T : T
+    }
+    namespace Observable {
+>Observable : typeof Observable
+
+        export let someValue: number;
+>someValue : number
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationExtendFileModule1.js b/tests/baselines/reference/moduleAugmentationExtendFileModule1.js
new file mode 100644
index 0000000000..a539100c2e
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendFileModule1.js
@@ -0,0 +1,49 @@
+//// [tests/cases/compiler/moduleAugmentationExtendFileModule1.ts] ////
+
+//// [map.ts]
+
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: number;
+    }
+}
+
+//// [observable.ts]
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+export namespace Observable {
+    let someValue: number;
+}
+
+
+//// [main.ts]
+import { Observable } from "./observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
+
+//// [observable.js]
+"use strict";
+var Observable;
+(function (Observable) {
+    var someValue;
+})(Observable = exports.Observable || (exports.Observable = {}));
+//// [map.js]
+"use strict";
+var observable_1 = require("./observable");
+observable_1.Observable.prototype.map = function () { };
+//// [main.js]
+"use strict";
+require("./map");
+var x;
+var y = x.map(function (x) { return x + 1; });
diff --git a/tests/baselines/reference/moduleAugmentationExtendFileModule1.symbols b/tests/baselines/reference/moduleAugmentationExtendFileModule1.symbols
new file mode 100644
index 0000000000..eca44ec774
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendFileModule1.symbols
@@ -0,0 +1,73 @@
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "./observable"
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+
+(<any>Observable.prototype).map = function() { }
+>Observable.prototype : Symbol(Observable.prototype)
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+>prototype : Symbol(Observable.prototype)
+
+declare module "./observable" {
+    interface Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : Symbol(map, Decl(map.ts, 6, 29))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>proj : Symbol(proj, Decl(map.ts, 7, 15))
+>e : Symbol(e, Decl(map.ts, 7, 22))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+    }
+    namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+
+        let someAnotherValue: number;
+>someAnotherValue : Symbol(someAnotherValue, Decl(map.ts, 10, 11))
+    }
+}
+
+=== tests/cases/compiler/observable.ts ===
+export declare class Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+
+    filter(pred: (e:T) => boolean): Observable<T>;
+>filter : Symbol(filter, Decl(observable.ts, 0, 36))
+>pred : Symbol(pred, Decl(observable.ts, 1, 11))
+>e : Symbol(e, Decl(observable.ts, 1, 18))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+}
+
+export namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+
+    let someValue: number;
+>someValue : Symbol(someValue, Decl(observable.ts, 5, 7))
+}
+
+
+=== tests/cases/compiler/main.ts ===
+import { Observable } from "./observable"
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+
+import "./map";
+
+let x: Observable<number>;
+>x : Symbol(x, Decl(main.ts, 3, 3))
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+
+let y = x.map(x => x + 1);
+>y : Symbol(y, Decl(main.ts, 4, 3))
+>x.map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 3, 3))
+>map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 4, 14))
+>x : Symbol(x, Decl(main.ts, 4, 14))
+
diff --git a/tests/baselines/reference/moduleAugmentationExtendFileModule1.types b/tests/baselines/reference/moduleAugmentationExtendFileModule1.types
new file mode 100644
index 0000000000..fad835029c
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendFileModule1.types
@@ -0,0 +1,83 @@
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "./observable"
+>Observable : typeof Observable
+
+(<any>Observable.prototype).map = function() { }
+>(<any>Observable.prototype).map = function() { } : () => void
+>(<any>Observable.prototype).map : any
+>(<any>Observable.prototype) : any
+><any>Observable.prototype : any
+>Observable.prototype : Observable<any>
+>Observable : typeof Observable
+>prototype : Observable<any>
+>map : any
+>function() { } : () => void
+
+declare module "./observable" {
+    interface Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : <U>(proj: (e: T) => U) => Observable<U>
+>U : U
+>proj : (e: T) => U
+>e : T
+>T : T
+>U : U
+>Observable : Observable<T>
+>U : U
+    }
+    namespace Observable {
+>Observable : typeof Observable
+
+        let someAnotherValue: number;
+>someAnotherValue : number
+    }
+}
+
+=== tests/cases/compiler/observable.ts ===
+export declare class Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+    filter(pred: (e:T) => boolean): Observable<T>;
+>filter : (pred: (e: T) => boolean) => Observable<T>
+>pred : (e: T) => boolean
+>e : T
+>T : T
+>Observable : Observable<T>
+>T : T
+}
+
+export namespace Observable {
+>Observable : typeof Observable
+
+    let someValue: number;
+>someValue : number
+}
+
+
+=== tests/cases/compiler/main.ts ===
+import { Observable } from "./observable"
+>Observable : typeof Observable
+
+import "./map";
+
+let x: Observable<number>;
+>x : Observable<number>
+>Observable : Observable<T>
+
+let y = x.map(x => x + 1);
+>y : Observable<number>
+>x.map(x => x + 1) : Observable<number>
+>x.map : <U>(proj: (e: number) => U) => Observable<U>
+>x : Observable<number>
+>map : <U>(proj: (e: number) => U) => Observable<U>
+>x => x + 1 : (x: number) => number
+>x : number
+>x + 1 : number
+>x : number
+>1 : number
+
diff --git a/tests/baselines/reference/moduleAugmentationExtendFileModule2.js b/tests/baselines/reference/moduleAugmentationExtendFileModule2.js
new file mode 100644
index 0000000000..389f2119ab
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendFileModule2.js
@@ -0,0 +1,53 @@
+//// [tests/cases/compiler/moduleAugmentationExtendFileModule2.ts] ////
+
+//// [map.ts]
+
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: string;
+    }
+}
+
+//// [observable.ts]
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+export namespace Observable {
+    export let someValue: number;
+}
+
+
+//// [main.ts]
+import { Observable } from "./observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
+let z1 = Observable.someValue.toFixed();
+let z2 = Observable.someAnotherValue.toLowerCase();
+
+//// [observable.js]
+"use strict";
+var Observable;
+(function (Observable) {
+})(Observable = exports.Observable || (exports.Observable = {}));
+//// [map.js]
+"use strict";
+var observable_1 = require("./observable");
+observable_1.Observable.prototype.map = function () { };
+//// [main.js]
+"use strict";
+var observable_1 = require("./observable");
+require("./map");
+var x;
+var y = x.map(function (x) { return x + 1; });
+var z1 = observable_1.Observable.someValue.toFixed();
+var z2 = observable_1.Observable.someAnotherValue.toLowerCase();
diff --git a/tests/baselines/reference/moduleAugmentationExtendFileModule2.symbols b/tests/baselines/reference/moduleAugmentationExtendFileModule2.symbols
new file mode 100644
index 0000000000..d0f25f693f
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendFileModule2.symbols
@@ -0,0 +1,89 @@
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "./observable"
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+
+(<any>Observable.prototype).map = function() { }
+>Observable.prototype : Symbol(Observable.prototype)
+>Observable : Symbol(Observable, Decl(map.ts, 1, 8))
+>prototype : Symbol(Observable.prototype)
+
+declare module "./observable" {
+    interface Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : Symbol(map, Decl(map.ts, 6, 29))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>proj : Symbol(proj, Decl(map.ts, 7, 15))
+>e : Symbol(e, Decl(map.ts, 7, 22))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>U : Symbol(U, Decl(map.ts, 7, 12))
+    }
+    namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+
+        let someAnotherValue: string;
+>someAnotherValue : Symbol(someAnotherValue, Decl(map.ts, 10, 11))
+    }
+}
+
+=== tests/cases/compiler/observable.ts ===
+export declare class Observable<T> {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+
+    filter(pred: (e:T) => boolean): Observable<T>;
+>filter : Symbol(filter, Decl(observable.ts, 0, 36))
+>pred : Symbol(pred, Decl(observable.ts, 1, 11))
+>e : Symbol(e, Decl(observable.ts, 1, 18))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+>T : Symbol(T, Decl(observable.ts, 0, 32), Decl(map.ts, 6, 25))
+}
+
+export namespace Observable {
+>Observable : Symbol(Observable, Decl(observable.ts, 0, 0), Decl(observable.ts, 2, 1), Decl(map.ts, 5, 31), Decl(map.ts, 8, 5))
+
+    export let someValue: number;
+>someValue : Symbol(someValue, Decl(observable.ts, 5, 14))
+}
+
+
+=== tests/cases/compiler/main.ts ===
+import { Observable } from "./observable"
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+
+import "./map";
+
+let x: Observable<number>;
+>x : Symbol(x, Decl(main.ts, 3, 3))
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+
+let y = x.map(x => x + 1);
+>y : Symbol(y, Decl(main.ts, 4, 3))
+>x.map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 3, 3))
+>map : Symbol(Observable.map, Decl(map.ts, 6, 29))
+>x : Symbol(x, Decl(main.ts, 4, 14))
+>x : Symbol(x, Decl(main.ts, 4, 14))
+
+let z1 = Observable.someValue.toFixed();
+>z1 : Symbol(z1, Decl(main.ts, 5, 3))
+>Observable.someValue.toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+>Observable.someValue : Symbol(Observable.someValue, Decl(observable.ts, 5, 14))
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+>someValue : Symbol(Observable.someValue, Decl(observable.ts, 5, 14))
+>toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+
+let z2 = Observable.someAnotherValue.toLowerCase();
+>z2 : Symbol(z2, Decl(main.ts, 6, 3))
+>Observable.someAnotherValue.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>Observable.someAnotherValue : Symbol(Observable.someAnotherValue, Decl(map.ts, 10, 11))
+>Observable : Symbol(Observable, Decl(main.ts, 0, 8))
+>someAnotherValue : Symbol(Observable.someAnotherValue, Decl(map.ts, 10, 11))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
diff --git a/tests/baselines/reference/moduleAugmentationExtendFileModule2.types b/tests/baselines/reference/moduleAugmentationExtendFileModule2.types
new file mode 100644
index 0000000000..85e4ead2ac
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationExtendFileModule2.types
@@ -0,0 +1,101 @@
+=== tests/cases/compiler/map.ts ===
+
+import { Observable } from "./observable"
+>Observable : typeof Observable
+
+(<any>Observable.prototype).map = function() { }
+>(<any>Observable.prototype).map = function() { } : () => void
+>(<any>Observable.prototype).map : any
+>(<any>Observable.prototype) : any
+><any>Observable.prototype : any
+>Observable.prototype : Observable<any>
+>Observable : typeof Observable
+>prototype : Observable<any>
+>map : any
+>function() { } : () => void
+
+declare module "./observable" {
+    interface Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+        map<U>(proj: (e:T) => U): Observable<U>
+>map : <U>(proj: (e: T) => U) => Observable<U>
+>U : U
+>proj : (e: T) => U
+>e : T
+>T : T
+>U : U
+>Observable : Observable<T>
+>U : U
+    }
+    namespace Observable {
+>Observable : typeof Observable
+
+        let someAnotherValue: string;
+>someAnotherValue : string
+    }
+}
+
+=== tests/cases/compiler/observable.ts ===
+export declare class Observable<T> {
+>Observable : Observable<T>
+>T : T
+
+    filter(pred: (e:T) => boolean): Observable<T>;
+>filter : (pred: (e: T) => boolean) => Observable<T>
+>pred : (e: T) => boolean
+>e : T
+>T : T
+>Observable : Observable<T>
+>T : T
+}
+
+export namespace Observable {
+>Observable : typeof Observable
+
+    export let someValue: number;
+>someValue : number
+}
+
+
+=== tests/cases/compiler/main.ts ===
+import { Observable } from "./observable"
+>Observable : typeof Observable
+
+import "./map";
+
+let x: Observable<number>;
+>x : Observable<number>
+>Observable : Observable<T>
+
+let y = x.map(x => x + 1);
+>y : Observable<number>
+>x.map(x => x + 1) : Observable<number>
+>x.map : <U>(proj: (e: number) => U) => Observable<U>
+>x : Observable<number>
+>map : <U>(proj: (e: number) => U) => Observable<U>
+>x => x + 1 : (x: number) => number
+>x : number
+>x + 1 : number
+>x : number
+>1 : number
+
+let z1 = Observable.someValue.toFixed();
+>z1 : string
+>Observable.someValue.toFixed() : string
+>Observable.someValue.toFixed : (fractionDigits?: number) => string
+>Observable.someValue : number
+>Observable : typeof Observable
+>someValue : number
+>toFixed : (fractionDigits?: number) => string
+
+let z2 = Observable.someAnotherValue.toLowerCase();
+>z2 : string
+>Observable.someAnotherValue.toLowerCase() : string
+>Observable.someAnotherValue.toLowerCase : () => string
+>Observable.someAnotherValue : string
+>Observable : typeof Observable
+>someAnotherValue : string
+>toLowerCase : () => string
+
diff --git a/tests/baselines/reference/moduleAugmentationGlobal1.js b/tests/baselines/reference/moduleAugmentationGlobal1.js
new file mode 100644
index 0000000000..99351642a1
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal1.js
@@ -0,0 +1,45 @@
+//// [tests/cases/compiler/moduleAugmentationGlobal1.ts] ////
+
+//// [f1.ts]
+
+export class A {x: number;}
+
+//// [f2.ts]
+import {A} from "./f1";
+
+// change the shape of Array<T>
+declare global {
+    interface Array<T> {
+        getA(): A;
+    }
+}
+
+let x = [1];
+let y = x.getA().x;
+
+
+//// [f1.js]
+"use strict";
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+exports.A = A;
+//// [f2.js]
+"use strict";
+var x = [1];
+var y = x.getA().x;
+
+
+//// [f1.d.ts]
+export declare class A {
+    x: number;
+}
+//// [f2.d.ts]
+import { A } from "./f1";
+declare global  {
+    interface Array<T> {
+        getA(): A;
+    }
+}
diff --git a/tests/baselines/reference/moduleAugmentationGlobal1.symbols b/tests/baselines/reference/moduleAugmentationGlobal1.symbols
new file mode 100644
index 0000000000..36139555c9
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal1.symbols
@@ -0,0 +1,35 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {x: number;}
+>A : Symbol(A, Decl(f1.ts, 0, 0))
+>x : Symbol(x, Decl(f1.ts, 1, 16))
+
+=== tests/cases/compiler/f2.ts ===
+import {A} from "./f1";
+>A : Symbol(A, Decl(f2.ts, 0, 8))
+
+// change the shape of Array<T>
+declare global {
+>global : Symbol(, Decl(f2.ts, 0, 23))
+
+    interface Array<T> {
+>Array : Symbol(Array, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(f2.ts, 3, 16))
+>T : Symbol(T, Decl(lib.d.ts, --, --), Decl(f2.ts, 4, 20))
+
+        getA(): A;
+>getA : Symbol(getA, Decl(f2.ts, 4, 24))
+>A : Symbol(A, Decl(f2.ts, 0, 8))
+    }
+}
+
+let x = [1];
+>x : Symbol(x, Decl(f2.ts, 9, 3))
+
+let y = x.getA().x;
+>y : Symbol(y, Decl(f2.ts, 10, 3))
+>x.getA().x : Symbol(A.x, Decl(f1.ts, 1, 16))
+>x.getA : Symbol(Array.getA, Decl(f2.ts, 4, 24))
+>x : Symbol(x, Decl(f2.ts, 9, 3))
+>getA : Symbol(Array.getA, Decl(f2.ts, 4, 24))
+>x : Symbol(A.x, Decl(f1.ts, 1, 16))
+
diff --git a/tests/baselines/reference/moduleAugmentationGlobal1.types b/tests/baselines/reference/moduleAugmentationGlobal1.types
new file mode 100644
index 0000000000..c1742edd7c
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal1.types
@@ -0,0 +1,38 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {x: number;}
+>A : A
+>x : number
+
+=== tests/cases/compiler/f2.ts ===
+import {A} from "./f1";
+>A : typeof A
+
+// change the shape of Array<T>
+declare global {
+>global : typeof 
+
+    interface Array<T> {
+>Array : T[]
+>T : T
+
+        getA(): A;
+>getA : () => A
+>A : A
+    }
+}
+
+let x = [1];
+>x : number[]
+>[1] : number[]
+>1 : number
+
+let y = x.getA().x;
+>y : number
+>x.getA().x : number
+>x.getA() : A
+>x.getA : () => A
+>x : number[]
+>getA : () => A
+>x : number
+
diff --git a/tests/baselines/reference/moduleAugmentationGlobal2.js b/tests/baselines/reference/moduleAugmentationGlobal2.js
new file mode 100644
index 0000000000..90e8373302
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal2.js
@@ -0,0 +1,45 @@
+//// [tests/cases/compiler/moduleAugmentationGlobal2.ts] ////
+
+//// [f1.ts]
+
+export class A {};
+//// [f2.ts]
+
+// change the shape of Array<T>
+import {A} from "./f1";
+
+declare global {
+    interface Array<T> {
+        getCountAsString(): string;
+    }
+}
+
+let x = [1];
+let y = x.getCountAsString().toLowerCase();
+
+
+//// [f1.js]
+"use strict";
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+exports.A = A;
+;
+//// [f2.js]
+"use strict";
+var x = [1];
+var y = x.getCountAsString().toLowerCase();
+
+
+//// [f1.d.ts]
+export declare class A {
+}
+//// [f2.d.ts]
+declare global  {
+    interface Array<T> {
+        getCountAsString(): string;
+    }
+}
+export {};
diff --git a/tests/baselines/reference/moduleAugmentationGlobal2.symbols b/tests/baselines/reference/moduleAugmentationGlobal2.symbols
new file mode 100644
index 0000000000..4ee2b9bace
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal2.symbols
@@ -0,0 +1,34 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {};
+>A : Symbol(A, Decl(f1.ts, 0, 0))
+
+=== tests/cases/compiler/f2.ts ===
+
+// change the shape of Array<T>
+import {A} from "./f1";
+>A : Symbol(A, Decl(f2.ts, 2, 8))
+
+declare global {
+>global : Symbol(, Decl(f2.ts, 2, 23))
+
+    interface Array<T> {
+>Array : Symbol(Array, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(f2.ts, 4, 16))
+>T : Symbol(T, Decl(lib.d.ts, --, --), Decl(f2.ts, 5, 20))
+
+        getCountAsString(): string;
+>getCountAsString : Symbol(getCountAsString, Decl(f2.ts, 5, 24))
+    }
+}
+
+let x = [1];
+>x : Symbol(x, Decl(f2.ts, 10, 3))
+
+let y = x.getCountAsString().toLowerCase();
+>y : Symbol(y, Decl(f2.ts, 11, 3))
+>x.getCountAsString().toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>x.getCountAsString : Symbol(Array.getCountAsString, Decl(f2.ts, 5, 24))
+>x : Symbol(x, Decl(f2.ts, 10, 3))
+>getCountAsString : Symbol(Array.getCountAsString, Decl(f2.ts, 5, 24))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
diff --git a/tests/baselines/reference/moduleAugmentationGlobal2.types b/tests/baselines/reference/moduleAugmentationGlobal2.types
new file mode 100644
index 0000000000..36ef480d8b
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal2.types
@@ -0,0 +1,38 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {};
+>A : A
+
+=== tests/cases/compiler/f2.ts ===
+
+// change the shape of Array<T>
+import {A} from "./f1";
+>A : typeof A
+
+declare global {
+>global : typeof 
+
+    interface Array<T> {
+>Array : T[]
+>T : T
+
+        getCountAsString(): string;
+>getCountAsString : () => string
+    }
+}
+
+let x = [1];
+>x : number[]
+>[1] : number[]
+>1 : number
+
+let y = x.getCountAsString().toLowerCase();
+>y : string
+>x.getCountAsString().toLowerCase() : string
+>x.getCountAsString().toLowerCase : () => string
+>x.getCountAsString() : string
+>x.getCountAsString : () => string
+>x : number[]
+>getCountAsString : () => string
+>toLowerCase : () => string
+
diff --git a/tests/baselines/reference/moduleAugmentationGlobal3.js b/tests/baselines/reference/moduleAugmentationGlobal3.js
new file mode 100644
index 0000000000..4cff75f5df
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal3.js
@@ -0,0 +1,52 @@
+//// [tests/cases/compiler/moduleAugmentationGlobal3.ts] ////
+
+//// [f1.ts]
+
+export class A {};
+//// [f2.ts]
+
+// change the shape of Array<T>
+import {A} from "./f1";
+
+declare global {
+    interface Array<T> {
+        getCountAsString(): string;
+    }
+}
+
+//// [f3.ts]
+import "./f2";
+
+let x = [1];
+let y = x.getCountAsString().toLowerCase();
+
+
+//// [f1.js]
+"use strict";
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+exports.A = A;
+;
+//// [f2.js]
+"use strict";
+//// [f3.js]
+"use strict";
+require("./f2");
+var x = [1];
+var y = x.getCountAsString().toLowerCase();
+
+
+//// [f1.d.ts]
+export declare class A {
+}
+//// [f2.d.ts]
+declare global  {
+    interface Array<T> {
+        getCountAsString(): string;
+    }
+}
+export {};
+//// [f3.d.ts]
diff --git a/tests/baselines/reference/moduleAugmentationGlobal3.symbols b/tests/baselines/reference/moduleAugmentationGlobal3.symbols
new file mode 100644
index 0000000000..acb9a7b9e5
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal3.symbols
@@ -0,0 +1,37 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {};
+>A : Symbol(A, Decl(f1.ts, 0, 0))
+
+=== tests/cases/compiler/f2.ts ===
+
+// change the shape of Array<T>
+import {A} from "./f1";
+>A : Symbol(A, Decl(f2.ts, 2, 8))
+
+declare global {
+>global : Symbol(, Decl(f2.ts, 2, 23))
+
+    interface Array<T> {
+>Array : Symbol(Array, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(f2.ts, 4, 16))
+>T : Symbol(T, Decl(lib.d.ts, --, --), Decl(f2.ts, 5, 20))
+
+        getCountAsString(): string;
+>getCountAsString : Symbol(getCountAsString, Decl(f2.ts, 5, 24))
+    }
+}
+
+=== tests/cases/compiler/f3.ts ===
+import "./f2";
+
+let x = [1];
+>x : Symbol(x, Decl(f3.ts, 2, 3))
+
+let y = x.getCountAsString().toLowerCase();
+>y : Symbol(y, Decl(f3.ts, 3, 3))
+>x.getCountAsString().toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>x.getCountAsString : Symbol(Array.getCountAsString, Decl(f2.ts, 5, 24))
+>x : Symbol(x, Decl(f3.ts, 2, 3))
+>getCountAsString : Symbol(Array.getCountAsString, Decl(f2.ts, 5, 24))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
diff --git a/tests/baselines/reference/moduleAugmentationGlobal3.types b/tests/baselines/reference/moduleAugmentationGlobal3.types
new file mode 100644
index 0000000000..58d7f30faa
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal3.types
@@ -0,0 +1,41 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {};
+>A : A
+
+=== tests/cases/compiler/f2.ts ===
+
+// change the shape of Array<T>
+import {A} from "./f1";
+>A : typeof A
+
+declare global {
+>global : typeof 
+
+    interface Array<T> {
+>Array : T[]
+>T : T
+
+        getCountAsString(): string;
+>getCountAsString : () => string
+    }
+}
+
+=== tests/cases/compiler/f3.ts ===
+import "./f2";
+
+let x = [1];
+>x : number[]
+>[1] : number[]
+>1 : number
+
+let y = x.getCountAsString().toLowerCase();
+>y : string
+>x.getCountAsString().toLowerCase() : string
+>x.getCountAsString().toLowerCase : () => string
+>x.getCountAsString() : string
+>x.getCountAsString : () => string
+>x : number[]
+>getCountAsString : () => string
+>toLowerCase : () => string
+
diff --git a/tests/baselines/reference/moduleAugmentationGlobal4.errors.txt b/tests/baselines/reference/moduleAugmentationGlobal4.errors.txt
new file mode 100644
index 0000000000..fd3444f56b
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal4.errors.txt
@@ -0,0 +1,25 @@
+tests/cases/compiler/f1.ts(3,15): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/f2.ts(3,15): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+
+
+==== tests/cases/compiler/f1.ts (1 errors) ====
+    
+    declare global {
+        interface Something {x}
+                  ~~~~~~~~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+    }
+    export {};
+==== tests/cases/compiler/f2.ts (1 errors) ====
+    
+    declare global {
+        interface Something {y}
+                  ~~~~~~~~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+    }
+    export {};
+==== tests/cases/compiler/f3.ts (0 errors) ====
+    import "./f1";
+    import "./f2";
+    
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationGlobal4.js b/tests/baselines/reference/moduleAugmentationGlobal4.js
new file mode 100644
index 0000000000..11c5d968df
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal4.js
@@ -0,0 +1,47 @@
+//// [tests/cases/compiler/moduleAugmentationGlobal4.ts] ////
+
+//// [f1.ts]
+
+declare global {
+    interface Something {x}
+}
+export {};
+//// [f2.ts]
+
+declare global {
+    interface Something {y}
+}
+export {};
+//// [f3.ts]
+import "./f1";
+import "./f2";
+
+
+
+//// [f1.js]
+"use strict";
+//// [f2.js]
+"use strict";
+//// [f3.js]
+"use strict";
+require("./f1");
+require("./f2");
+
+
+//// [f1.d.ts]
+declare global  {
+    interface Something {
+        x: any;
+    }
+}
+export {  };
+export {};
+//// [f2.d.ts]
+declare global  {
+    interface Something {
+        y: any;
+    }
+}
+export {  };
+export {};
+//// [f3.d.ts]
diff --git a/tests/baselines/reference/moduleAugmentationGlobal5.errors.txt b/tests/baselines/reference/moduleAugmentationGlobal5.errors.txt
new file mode 100644
index 0000000000..4f1f913376
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal5.errors.txt
@@ -0,0 +1,28 @@
+tests/cases/compiler/f1.d.ts(4,19): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/f2.d.ts(3,19): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+
+
+==== tests/cases/compiler/f3.ts (0 errors) ====
+    /// <reference path="f1.d.ts"/>
+    /// <reference path="f2.d.ts"/>
+    import "A";
+    import "B";
+    
+    
+==== tests/cases/compiler/f1.d.ts (1 errors) ====
+    
+    declare module "A" {
+        global {
+            interface Something {x}
+                      ~~~~~~~~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        }
+    }
+==== tests/cases/compiler/f2.d.ts (1 errors) ====
+    declare module "B" {
+        global {
+            interface Something {y}
+                      ~~~~~~~~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationGlobal5.js b/tests/baselines/reference/moduleAugmentationGlobal5.js
new file mode 100644
index 0000000000..3efdd2dbb9
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal5.js
@@ -0,0 +1,34 @@
+//// [tests/cases/compiler/moduleAugmentationGlobal5.ts] ////
+
+//// [f1.d.ts]
+
+declare module "A" {
+    global {
+        interface Something {x}
+    }
+}
+//// [f2.d.ts]
+declare module "B" {
+    global {
+        interface Something {y}
+    }
+}
+//// [f3.ts]
+/// <reference path="f1.d.ts"/>
+/// <reference path="f2.d.ts"/>
+import "A";
+import "B";
+
+
+
+//// [f3.js]
+"use strict";
+/// <reference path="f1.d.ts"/>
+/// <reference path="f2.d.ts"/>
+require("A");
+require("B");
+
+
+//// [f3.d.ts]
+/// <reference path="f1.d.ts" />
+/// <reference path="f2.d.ts" />
diff --git a/tests/baselines/reference/moduleAugmentationGlobal6.errors.txt b/tests/baselines/reference/moduleAugmentationGlobal6.errors.txt
new file mode 100644
index 0000000000..849c45111a
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal6.errors.txt
@@ -0,0 +1,9 @@
+tests/cases/compiler/moduleAugmentationGlobal6.ts(1,9): error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+
+
+==== tests/cases/compiler/moduleAugmentationGlobal6.ts (1 errors) ====
+    declare global {
+            ~~~~~~
+!!! error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+        interface Array<T> { x }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationGlobal6.js b/tests/baselines/reference/moduleAugmentationGlobal6.js
new file mode 100644
index 0000000000..ac988f670d
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal6.js
@@ -0,0 +1,6 @@
+//// [moduleAugmentationGlobal6.ts]
+declare global {
+    interface Array<T> { x }
+}
+
+//// [moduleAugmentationGlobal6.js]
diff --git a/tests/baselines/reference/moduleAugmentationGlobal6_1.errors.txt b/tests/baselines/reference/moduleAugmentationGlobal6_1.errors.txt
new file mode 100644
index 0000000000..01315f9fcb
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal6_1.errors.txt
@@ -0,0 +1,12 @@
+tests/cases/compiler/moduleAugmentationGlobal6_1.ts(1,1): error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+tests/cases/compiler/moduleAugmentationGlobal6_1.ts(1,1): error TS2670: Augmentations for the global scope should have 'declare' modifier unless they appear in already ambient context.
+
+
+==== tests/cases/compiler/moduleAugmentationGlobal6_1.ts (2 errors) ====
+    global {
+    ~~~~~~
+!!! error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+    ~~~~~~
+!!! error TS2670: Augmentations for the global scope should have 'declare' modifier unless they appear in already ambient context.
+        interface Array<T> { x }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationGlobal6_1.js b/tests/baselines/reference/moduleAugmentationGlobal6_1.js
new file mode 100644
index 0000000000..5ae85debbe
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal6_1.js
@@ -0,0 +1,6 @@
+//// [moduleAugmentationGlobal6_1.ts]
+global {
+    interface Array<T> { x }
+}
+
+//// [moduleAugmentationGlobal6_1.js]
diff --git a/tests/baselines/reference/moduleAugmentationGlobal7.errors.txt b/tests/baselines/reference/moduleAugmentationGlobal7.errors.txt
new file mode 100644
index 0000000000..3ba8003288
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal7.errors.txt
@@ -0,0 +1,11 @@
+tests/cases/compiler/moduleAugmentationGlobal7.ts(2,13): error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+
+
+==== tests/cases/compiler/moduleAugmentationGlobal7.ts (1 errors) ====
+    namespace A {
+        declare global {
+                ~~~~~~
+!!! error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+            interface Array<T> { x }
+        }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationGlobal7.js b/tests/baselines/reference/moduleAugmentationGlobal7.js
new file mode 100644
index 0000000000..54c6ddc0de
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal7.js
@@ -0,0 +1,8 @@
+//// [moduleAugmentationGlobal7.ts]
+namespace A {
+    declare global {
+        interface Array<T> { x }
+    }
+}
+
+//// [moduleAugmentationGlobal7.js]
diff --git a/tests/baselines/reference/moduleAugmentationGlobal7_1.errors.txt b/tests/baselines/reference/moduleAugmentationGlobal7_1.errors.txt
new file mode 100644
index 0000000000..c2e8282f2b
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal7_1.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/compiler/moduleAugmentationGlobal7_1.ts(2,5): error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+tests/cases/compiler/moduleAugmentationGlobal7_1.ts(2,5): error TS2670: Augmentations for the global scope should have 'declare' modifier unless they appear in already ambient context.
+
+
+==== tests/cases/compiler/moduleAugmentationGlobal7_1.ts (2 errors) ====
+    namespace A {
+        global {
+        ~~~~~~
+!!! error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+        ~~~~~~
+!!! error TS2670: Augmentations for the global scope should have 'declare' modifier unless they appear in already ambient context.
+            interface Array<T> { x }
+        }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationGlobal7_1.js b/tests/baselines/reference/moduleAugmentationGlobal7_1.js
new file mode 100644
index 0000000000..745be0d76a
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal7_1.js
@@ -0,0 +1,8 @@
+//// [moduleAugmentationGlobal7_1.ts]
+namespace A {
+    global {
+        interface Array<T> { x }
+    }
+}
+
+//// [moduleAugmentationGlobal7_1.js]
diff --git a/tests/baselines/reference/moduleAugmentationGlobal8.errors.txt b/tests/baselines/reference/moduleAugmentationGlobal8.errors.txt
new file mode 100644
index 0000000000..09c84fea2c
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal8.errors.txt
@@ -0,0 +1,13 @@
+tests/cases/compiler/moduleAugmentationGlobal8.ts(2,13): error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+
+
+==== tests/cases/compiler/moduleAugmentationGlobal8.ts (1 errors) ====
+    namespace A {
+        declare global {
+                ~~~~~~
+!!! error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+            interface Array<T> { x }
+        }
+    }
+    export {}
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationGlobal8.js b/tests/baselines/reference/moduleAugmentationGlobal8.js
new file mode 100644
index 0000000000..261dfd21b5
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal8.js
@@ -0,0 +1,13 @@
+//// [moduleAugmentationGlobal8.ts]
+namespace A {
+    declare global {
+        interface Array<T> { x }
+    }
+}
+export {}
+
+
+//// [moduleAugmentationGlobal8.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+});
diff --git a/tests/baselines/reference/moduleAugmentationGlobal8_1.errors.txt b/tests/baselines/reference/moduleAugmentationGlobal8_1.errors.txt
new file mode 100644
index 0000000000..022a4f5ec1
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal8_1.errors.txt
@@ -0,0 +1,16 @@
+tests/cases/compiler/moduleAugmentationGlobal8_1.ts(2,5): error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+tests/cases/compiler/moduleAugmentationGlobal8_1.ts(2,5): error TS2670: Augmentations for the global scope should have 'declare' modifier unless they appear in already ambient context.
+
+
+==== tests/cases/compiler/moduleAugmentationGlobal8_1.ts (2 errors) ====
+    namespace A {
+        global {
+        ~~~~~~
+!!! error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.
+        ~~~~~~
+!!! error TS2670: Augmentations for the global scope should have 'declare' modifier unless they appear in already ambient context.
+            interface Array<T> { x }
+        }
+    }
+    export {}
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationGlobal8_1.js b/tests/baselines/reference/moduleAugmentationGlobal8_1.js
new file mode 100644
index 0000000000..2ac585a711
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationGlobal8_1.js
@@ -0,0 +1,13 @@
+//// [moduleAugmentationGlobal8_1.ts]
+namespace A {
+    global {
+        interface Array<T> { x }
+    }
+}
+export {}
+
+
+//// [moduleAugmentationGlobal8_1.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+});
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports1.js b/tests/baselines/reference/moduleAugmentationImportsAndExports1.js
new file mode 100644
index 0000000000..7159e7b5d0
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports1.js
@@ -0,0 +1,71 @@
+//// [tests/cases/compiler/moduleAugmentationImportsAndExports1.ts] ////
+
+//// [f1.ts]
+
+export class A {}
+
+//// [f2.ts]
+export class B {
+    n: number;
+}
+
+//// [f3.ts]
+import {A} from "./f1";
+import {B} from "./f2";
+
+A.prototype.foo = function () { return undefined; }
+declare module "./f1" {
+    interface A {
+        foo(): B;
+    }
+}
+
+//// [f4.ts]
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
+
+//// [f1.js]
+"use strict";
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+exports.A = A;
+//// [f2.js]
+"use strict";
+var B = (function () {
+    function B() {
+    }
+    return B;
+}());
+exports.B = B;
+//// [f3.js]
+"use strict";
+var f1_1 = require("./f1");
+f1_1.A.prototype.foo = function () { return undefined; };
+//// [f4.js]
+"use strict";
+require("./f3");
+var a;
+var b = a.foo().n;
+
+
+//// [f1.d.ts]
+export declare class A {
+}
+//// [f2.d.ts]
+export declare class B {
+    n: number;
+}
+//// [f3.d.ts]
+import { B } from "./f2";
+declare module "./f1" {
+    interface A {
+        foo(): B;
+    }
+}
+//// [f4.d.ts]
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports1.symbols b/tests/baselines/reference/moduleAugmentationImportsAndExports1.symbols
new file mode 100644
index 0000000000..c641cad522
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports1.symbols
@@ -0,0 +1,56 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {}
+>A : Symbol(A, Decl(f1.ts, 0, 0), Decl(f3.ts, 4, 23))
+
+=== tests/cases/compiler/f2.ts ===
+export class B {
+>B : Symbol(B, Decl(f2.ts, 0, 0))
+
+    n: number;
+>n : Symbol(n, Decl(f2.ts, 0, 16))
+}
+
+=== tests/cases/compiler/f3.ts ===
+import {A} from "./f1";
+>A : Symbol(A, Decl(f3.ts, 0, 8))
+
+import {B} from "./f2";
+>B : Symbol(B, Decl(f3.ts, 1, 8))
+
+A.prototype.foo = function () { return undefined; }
+>A.prototype.foo : Symbol(A.foo, Decl(f3.ts, 5, 17))
+>A.prototype : Symbol(A.prototype)
+>A : Symbol(A, Decl(f3.ts, 0, 8))
+>prototype : Symbol(A.prototype)
+>foo : Symbol(A.foo, Decl(f3.ts, 5, 17))
+>undefined : Symbol(undefined)
+
+declare module "./f1" {
+    interface A {
+>A : Symbol(A, Decl(f1.ts, 0, 0), Decl(f3.ts, 4, 23))
+
+        foo(): B;
+>foo : Symbol(foo, Decl(f3.ts, 5, 17))
+>B : Symbol(B, Decl(f3.ts, 1, 8))
+    }
+}
+
+=== tests/cases/compiler/f4.ts ===
+import {A} from "./f1";
+>A : Symbol(A, Decl(f4.ts, 0, 8))
+
+import "./f3";
+
+let a: A;
+>a : Symbol(a, Decl(f4.ts, 3, 3))
+>A : Symbol(A, Decl(f4.ts, 0, 8))
+
+let b = a.foo().n;
+>b : Symbol(b, Decl(f4.ts, 4, 3))
+>a.foo().n : Symbol(B.n, Decl(f2.ts, 0, 16))
+>a.foo : Symbol(A.foo, Decl(f3.ts, 5, 17))
+>a : Symbol(a, Decl(f4.ts, 3, 3))
+>foo : Symbol(A.foo, Decl(f3.ts, 5, 17))
+>n : Symbol(B.n, Decl(f2.ts, 0, 16))
+
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports1.types b/tests/baselines/reference/moduleAugmentationImportsAndExports1.types
new file mode 100644
index 0000000000..886a04b54e
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports1.types
@@ -0,0 +1,59 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {}
+>A : A
+
+=== tests/cases/compiler/f2.ts ===
+export class B {
+>B : B
+
+    n: number;
+>n : number
+}
+
+=== tests/cases/compiler/f3.ts ===
+import {A} from "./f1";
+>A : typeof A
+
+import {B} from "./f2";
+>B : typeof B
+
+A.prototype.foo = function () { return undefined; }
+>A.prototype.foo = function () { return undefined; } : () => any
+>A.prototype.foo : () => B
+>A.prototype : A
+>A : typeof A
+>prototype : A
+>foo : () => B
+>function () { return undefined; } : () => any
+>undefined : undefined
+
+declare module "./f1" {
+    interface A {
+>A : A
+
+        foo(): B;
+>foo : () => B
+>B : B
+    }
+}
+
+=== tests/cases/compiler/f4.ts ===
+import {A} from "./f1";
+>A : typeof A
+
+import "./f3";
+
+let a: A;
+>a : A
+>A : A
+
+let b = a.foo().n;
+>b : number
+>a.foo().n : number
+>a.foo() : B
+>a.foo : () => B
+>a : A
+>foo : () => B
+>n : number
+
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports2.errors.txt b/tests/baselines/reference/moduleAugmentationImportsAndExports2.errors.txt
new file mode 100644
index 0000000000..deb3881e20
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports2.errors.txt
@@ -0,0 +1,73 @@
+tests/cases/compiler/f3.ts(3,13): error TS2339: Property 'foo' does not exist on type 'A'.
+tests/cases/compiler/f3.ts(11,5): error TS2667: Imports are not permitted in module augmentations. Consider moving them to the enclosing external module.
+tests/cases/compiler/f3.ts(11,21): error TS2307: Cannot find module './f2'.
+tests/cases/compiler/f3.ts(12,5): error TS2666: Exports and export assignments are not permitted in module augmentations.
+tests/cases/compiler/f3.ts(12,21): error TS2307: Cannot find module './f2'.
+tests/cases/compiler/f3.ts(13,12): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/f3.ts(13,16): error TS4000: Import declaration 'I' is using private name 'N'.
+tests/cases/compiler/f3.ts(14,12): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/f3.ts(14,16): error TS4000: Import declaration 'C' is using private name 'N'.
+tests/cases/compiler/f3.ts(16,15): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/f4.ts(5,11): error TS2339: Property 'foo' does not exist on type 'A'.
+
+
+==== tests/cases/compiler/f1.ts (0 errors) ====
+    
+    export class A {}
+    
+==== tests/cases/compiler/f2.ts (0 errors) ====
+    export class B {
+        n: number;
+    }
+    
+==== tests/cases/compiler/f3.ts (10 errors) ====
+    import {A} from "./f1";
+    
+    A.prototype.foo = function () { return undefined; }
+                ~~~
+!!! error TS2339: Property 'foo' does not exist on type 'A'.
+    
+    namespace N {
+        export interface Ifc { a }
+        export interface Cls { a }
+    }
+    
+    declare module "./f1" {
+        import {B} from "./f2";
+        ~~~~~~
+!!! error TS2667: Imports are not permitted in module augmentations. Consider moving them to the enclosing external module.
+                        ~~~~~~
+!!! error TS2307: Cannot find module './f2'.
+        export {B} from "./f2";
+        ~~~~~~
+!!! error TS2666: Exports and export assignments are not permitted in module augmentations.
+                        ~~~~~~
+!!! error TS2307: Cannot find module './f2'.
+        import I = N.Ifc;
+               ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                   ~
+!!! error TS4000: Import declaration 'I' is using private name 'N'.
+        import C = N.Cls;
+               ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                   ~
+!!! error TS4000: Import declaration 'C' is using private name 'N'.
+        // should have explicit export
+        interface A {
+                  ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+            foo(): B;
+            bar(): I;
+            baz(): C;
+        }
+    }
+    
+==== tests/cases/compiler/f4.ts (1 errors) ====
+    import {A} from "./f1";
+    import "./f3";
+    
+    let a: A;
+    let b = a.foo().n;
+              ~~~
+!!! error TS2339: Property 'foo' does not exist on type 'A'.
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports2.js b/tests/baselines/reference/moduleAugmentationImportsAndExports2.js
new file mode 100644
index 0000000000..3a4a807a33
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports2.js
@@ -0,0 +1,76 @@
+//// [tests/cases/compiler/moduleAugmentationImportsAndExports2.ts] ////
+
+//// [f1.ts]
+
+export class A {}
+
+//// [f2.ts]
+export class B {
+    n: number;
+}
+
+//// [f3.ts]
+import {A} from "./f1";
+
+A.prototype.foo = function () { return undefined; }
+
+namespace N {
+    export interface Ifc { a }
+    export interface Cls { a }
+}
+
+declare module "./f1" {
+    import {B} from "./f2";
+    export {B} from "./f2";
+    import I = N.Ifc;
+    import C = N.Cls;
+    // should have explicit export
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+
+//// [f4.ts]
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
+
+//// [f1.js]
+"use strict";
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+exports.A = A;
+//// [f2.js]
+"use strict";
+var B = (function () {
+    function B() {
+    }
+    return B;
+}());
+exports.B = B;
+//// [f3.js]
+"use strict";
+var f1_1 = require("./f1");
+f1_1.A.prototype.foo = function () { return undefined; };
+//// [f4.js]
+"use strict";
+require("./f3");
+var a;
+var b = a.foo().n;
+
+
+//// [f1.d.ts]
+export declare class A {
+}
+//// [f2.d.ts]
+export declare class B {
+    n: number;
+}
+//// [f4.d.ts]
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports3.errors.txt b/tests/baselines/reference/moduleAugmentationImportsAndExports3.errors.txt
new file mode 100644
index 0000000000..a7c8fa2cff
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports3.errors.txt
@@ -0,0 +1,56 @@
+tests/cases/compiler/f3.ts(11,5): error TS2667: Imports are not permitted in module augmentations. Consider moving them to the enclosing external module.
+tests/cases/compiler/f3.ts(11,21): error TS2307: Cannot find module './f2'.
+tests/cases/compiler/f3.ts(12,12): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/f3.ts(12,16): error TS4000: Import declaration 'I' is using private name 'N'.
+tests/cases/compiler/f3.ts(13,12): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/f3.ts(13,16): error TS4000: Import declaration 'C' is using private name 'N'.
+
+
+==== tests/cases/compiler/f1.ts (0 errors) ====
+    
+    export class A {}
+    
+==== tests/cases/compiler/f2.ts (0 errors) ====
+    export class B {
+        n: number;
+    }
+    
+==== tests/cases/compiler/f3.ts (6 errors) ====
+    import {A} from "./f1";
+    
+    A.prototype.foo = function () { return undefined; }
+    
+    namespace N {
+        export interface Ifc { a }
+        export interface Cls { a }
+    }
+    
+    declare module "./f1" {
+        import {B} from "./f2";
+        ~~~~~~
+!!! error TS2667: Imports are not permitted in module augmentations. Consider moving them to the enclosing external module.
+                        ~~~~~~
+!!! error TS2307: Cannot find module './f2'.
+        import I = N.Ifc;
+               ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                   ~
+!!! error TS4000: Import declaration 'I' is using private name 'N'.
+        import C = N.Cls;
+               ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                   ~
+!!! error TS4000: Import declaration 'C' is using private name 'N'.
+        interface A {
+            foo(): B;
+            bar(): I;
+            baz(): C;
+        }
+    }
+    
+==== tests/cases/compiler/f4.ts (0 errors) ====
+    import {A} from "./f1";
+    import "./f3";
+    
+    let a: A;
+    let b = a.foo().n;
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports3.js b/tests/baselines/reference/moduleAugmentationImportsAndExports3.js
new file mode 100644
index 0000000000..d872a79e98
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports3.js
@@ -0,0 +1,74 @@
+//// [tests/cases/compiler/moduleAugmentationImportsAndExports3.ts] ////
+
+//// [f1.ts]
+
+export class A {}
+
+//// [f2.ts]
+export class B {
+    n: number;
+}
+
+//// [f3.ts]
+import {A} from "./f1";
+
+A.prototype.foo = function () { return undefined; }
+
+namespace N {
+    export interface Ifc { a }
+    export interface Cls { a }
+}
+
+declare module "./f1" {
+    import {B} from "./f2";
+    import I = N.Ifc;
+    import C = N.Cls;
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+
+//// [f4.ts]
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
+
+//// [f1.js]
+"use strict";
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+exports.A = A;
+//// [f2.js]
+"use strict";
+var B = (function () {
+    function B() {
+    }
+    return B;
+}());
+exports.B = B;
+//// [f3.js]
+"use strict";
+var f1_1 = require("./f1");
+f1_1.A.prototype.foo = function () { return undefined; };
+//// [f4.js]
+"use strict";
+require("./f3");
+var a;
+var b = a.foo().n;
+
+
+//// [f1.d.ts]
+export declare class A {
+}
+//// [f2.d.ts]
+export declare class B {
+    n: number;
+}
+//// [f4.d.ts]
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports4.js b/tests/baselines/reference/moduleAugmentationImportsAndExports4.js
new file mode 100644
index 0000000000..5309555581
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports4.js
@@ -0,0 +1,68 @@
+//// [tests/cases/compiler/moduleAugmentationImportsAndExports4.ts] ////
+
+//// [f1.ts]
+
+export class A {}
+
+//// [f2.ts]
+export class B {
+    n: number;
+}
+
+//// [f3.ts]
+import {A} from "./f1";
+import {B} from "./f2";
+
+A.prototype.foo = function () { return undefined; }
+
+namespace N {
+    export interface Ifc { a: number; }
+    export interface Cls { b: number; }
+}
+import I = N.Ifc;
+import C = N.Cls;
+
+declare module "./f1" {
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+
+//// [f4.ts]
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
+let c = a.bar().a;
+let d = a.baz().b;
+
+//// [f1.js]
+"use strict";
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+exports.A = A;
+//// [f2.js]
+"use strict";
+var B = (function () {
+    function B() {
+    }
+    return B;
+}());
+exports.B = B;
+//// [f3.js]
+"use strict";
+var f1_1 = require("./f1");
+f1_1.A.prototype.foo = function () { return undefined; };
+//// [f4.js]
+"use strict";
+require("./f3");
+var a;
+var b = a.foo().n;
+var c = a.bar().a;
+var d = a.baz().b;
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports4.symbols b/tests/baselines/reference/moduleAugmentationImportsAndExports4.symbols
new file mode 100644
index 0000000000..94dc05519d
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports4.symbols
@@ -0,0 +1,101 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {}
+>A : Symbol(A, Decl(f1.ts, 0, 0), Decl(f3.ts, 12, 23))
+
+=== tests/cases/compiler/f2.ts ===
+export class B {
+>B : Symbol(B, Decl(f2.ts, 0, 0))
+
+    n: number;
+>n : Symbol(n, Decl(f2.ts, 0, 16))
+}
+
+=== tests/cases/compiler/f3.ts ===
+import {A} from "./f1";
+>A : Symbol(A, Decl(f3.ts, 0, 8))
+
+import {B} from "./f2";
+>B : Symbol(B, Decl(f3.ts, 1, 8))
+
+A.prototype.foo = function () { return undefined; }
+>A.prototype.foo : Symbol(A.foo, Decl(f3.ts, 13, 17))
+>A.prototype : Symbol(A.prototype)
+>A : Symbol(A, Decl(f3.ts, 0, 8))
+>prototype : Symbol(A.prototype)
+>foo : Symbol(A.foo, Decl(f3.ts, 13, 17))
+>undefined : Symbol(undefined)
+
+namespace N {
+>N : Symbol(N, Decl(f3.ts, 3, 51))
+
+    export interface Ifc { a: number; }
+>Ifc : Symbol(Ifc, Decl(f3.ts, 5, 13))
+>a : Symbol(a, Decl(f3.ts, 6, 26))
+
+    export interface Cls { b: number; }
+>Cls : Symbol(Cls, Decl(f3.ts, 6, 39))
+>b : Symbol(b, Decl(f3.ts, 7, 26))
+}
+import I = N.Ifc;
+>I : Symbol(I, Decl(f3.ts, 8, 1))
+>N : Symbol(N, Decl(f3.ts, 3, 51))
+>Ifc : Symbol(I, Decl(f3.ts, 5, 13))
+
+import C = N.Cls;
+>C : Symbol(C, Decl(f3.ts, 9, 17))
+>N : Symbol(N, Decl(f3.ts, 3, 51))
+>Cls : Symbol(C, Decl(f3.ts, 6, 39))
+
+declare module "./f1" {
+    interface A {
+>A : Symbol(A, Decl(f1.ts, 0, 0), Decl(f3.ts, 12, 23))
+
+        foo(): B;
+>foo : Symbol(foo, Decl(f3.ts, 13, 17))
+>B : Symbol(B, Decl(f3.ts, 1, 8))
+
+        bar(): I;
+>bar : Symbol(bar, Decl(f3.ts, 14, 17))
+>I : Symbol(I, Decl(f3.ts, 8, 1))
+
+        baz(): C;
+>baz : Symbol(baz, Decl(f3.ts, 15, 17))
+>C : Symbol(C, Decl(f3.ts, 9, 17))
+    }
+}
+
+=== tests/cases/compiler/f4.ts ===
+import {A} from "./f1";
+>A : Symbol(A, Decl(f4.ts, 0, 8))
+
+import "./f3";
+
+let a: A;
+>a : Symbol(a, Decl(f4.ts, 3, 3))
+>A : Symbol(A, Decl(f4.ts, 0, 8))
+
+let b = a.foo().n;
+>b : Symbol(b, Decl(f4.ts, 4, 3))
+>a.foo().n : Symbol(B.n, Decl(f2.ts, 0, 16))
+>a.foo : Symbol(A.foo, Decl(f3.ts, 13, 17))
+>a : Symbol(a, Decl(f4.ts, 3, 3))
+>foo : Symbol(A.foo, Decl(f3.ts, 13, 17))
+>n : Symbol(B.n, Decl(f2.ts, 0, 16))
+
+let c = a.bar().a;
+>c : Symbol(c, Decl(f4.ts, 5, 3))
+>a.bar().a : Symbol(N.Ifc.a, Decl(f3.ts, 6, 26))
+>a.bar : Symbol(A.bar, Decl(f3.ts, 14, 17))
+>a : Symbol(a, Decl(f4.ts, 3, 3))
+>bar : Symbol(A.bar, Decl(f3.ts, 14, 17))
+>a : Symbol(N.Ifc.a, Decl(f3.ts, 6, 26))
+
+let d = a.baz().b;
+>d : Symbol(d, Decl(f4.ts, 6, 3))
+>a.baz().b : Symbol(N.Cls.b, Decl(f3.ts, 7, 26))
+>a.baz : Symbol(A.baz, Decl(f3.ts, 15, 17))
+>a : Symbol(a, Decl(f4.ts, 3, 3))
+>baz : Symbol(A.baz, Decl(f3.ts, 15, 17))
+>b : Symbol(N.Cls.b, Decl(f3.ts, 7, 26))
+
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports4.types b/tests/baselines/reference/moduleAugmentationImportsAndExports4.types
new file mode 100644
index 0000000000..454dc5d27e
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports4.types
@@ -0,0 +1,106 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {}
+>A : A
+
+=== tests/cases/compiler/f2.ts ===
+export class B {
+>B : B
+
+    n: number;
+>n : number
+}
+
+=== tests/cases/compiler/f3.ts ===
+import {A} from "./f1";
+>A : typeof A
+
+import {B} from "./f2";
+>B : typeof B
+
+A.prototype.foo = function () { return undefined; }
+>A.prototype.foo = function () { return undefined; } : () => any
+>A.prototype.foo : () => B
+>A.prototype : A
+>A : typeof A
+>prototype : A
+>foo : () => B
+>function () { return undefined; } : () => any
+>undefined : undefined
+
+namespace N {
+>N : any
+
+    export interface Ifc { a: number; }
+>Ifc : Ifc
+>a : number
+
+    export interface Cls { b: number; }
+>Cls : Cls
+>b : number
+}
+import I = N.Ifc;
+>I : any
+>N : any
+>Ifc : I
+
+import C = N.Cls;
+>C : any
+>N : any
+>Cls : C
+
+declare module "./f1" {
+    interface A {
+>A : A
+
+        foo(): B;
+>foo : () => B
+>B : B
+
+        bar(): I;
+>bar : () => I
+>I : I
+
+        baz(): C;
+>baz : () => C
+>C : C
+    }
+}
+
+=== tests/cases/compiler/f4.ts ===
+import {A} from "./f1";
+>A : typeof A
+
+import "./f3";
+
+let a: A;
+>a : A
+>A : A
+
+let b = a.foo().n;
+>b : number
+>a.foo().n : number
+>a.foo() : B
+>a.foo : () => B
+>a : A
+>foo : () => B
+>n : number
+
+let c = a.bar().a;
+>c : number
+>a.bar().a : number
+>a.bar() : N.Ifc
+>a.bar : () => N.Ifc
+>a : A
+>bar : () => N.Ifc
+>a : number
+
+let d = a.baz().b;
+>d : number
+>a.baz().b : number
+>a.baz() : N.Cls
+>a.baz : () => N.Cls
+>a : A
+>baz : () => N.Cls
+>b : number
+
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports5.errors.txt b/tests/baselines/reference/moduleAugmentationImportsAndExports5.errors.txt
new file mode 100644
index 0000000000..5f78345388
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports5.errors.txt
@@ -0,0 +1,46 @@
+tests/cases/compiler/f3.ts(10,12): error TS4000: Import declaration 'I' is using private name 'N'.
+tests/cases/compiler/f3.ts(11,12): error TS4000: Import declaration 'C' is using private name 'N'.
+
+
+==== tests/cases/compiler/f1.ts (0 errors) ====
+    
+    export class A {}
+    
+==== tests/cases/compiler/f2.ts (0 errors) ====
+    export class B {
+        n: number;
+    }
+    
+==== tests/cases/compiler/f3.ts (2 errors) ====
+    import {A} from "./f1";
+    import {B} from "./f2";
+    
+    A.prototype.foo = function () { return undefined; }
+    
+    namespace N {
+        export interface Ifc { a: number; }
+        export interface Cls { b: number; }
+    }
+    import I = N.Ifc;
+               ~
+!!! error TS4000: Import declaration 'I' is using private name 'N'.
+    import C = N.Cls;
+               ~
+!!! error TS4000: Import declaration 'C' is using private name 'N'.
+    
+    declare module "./f1" {
+        interface A {
+            foo(): B;
+            bar(): I;
+            baz(): C;
+        }
+    }
+    
+==== tests/cases/compiler/f4.ts (0 errors) ====
+    import {A} from "./f1";
+    import "./f3";
+    
+    let a: A;
+    let b = a.foo().n;
+    let c = a.bar().a;
+    let d = a.baz().b;
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports5.js b/tests/baselines/reference/moduleAugmentationImportsAndExports5.js
new file mode 100644
index 0000000000..c9b622ccf2
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports5.js
@@ -0,0 +1,78 @@
+//// [tests/cases/compiler/moduleAugmentationImportsAndExports5.ts] ////
+
+//// [f1.ts]
+
+export class A {}
+
+//// [f2.ts]
+export class B {
+    n: number;
+}
+
+//// [f3.ts]
+import {A} from "./f1";
+import {B} from "./f2";
+
+A.prototype.foo = function () { return undefined; }
+
+namespace N {
+    export interface Ifc { a: number; }
+    export interface Cls { b: number; }
+}
+import I = N.Ifc;
+import C = N.Cls;
+
+declare module "./f1" {
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+
+//// [f4.ts]
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
+let c = a.bar().a;
+let d = a.baz().b;
+
+//// [f1.js]
+"use strict";
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+exports.A = A;
+//// [f2.js]
+"use strict";
+var B = (function () {
+    function B() {
+    }
+    return B;
+}());
+exports.B = B;
+//// [f3.js]
+"use strict";
+var f1_1 = require("./f1");
+f1_1.A.prototype.foo = function () { return undefined; };
+//// [f4.js]
+"use strict";
+require("./f3");
+var a;
+var b = a.foo().n;
+var c = a.bar().a;
+var d = a.baz().b;
+
+
+//// [f1.d.ts]
+export declare class A {
+}
+//// [f2.d.ts]
+export declare class B {
+    n: number;
+}
+//// [f4.d.ts]
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports6.js b/tests/baselines/reference/moduleAugmentationImportsAndExports6.js
new file mode 100644
index 0000000000..f0b297720b
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports6.js
@@ -0,0 +1,97 @@
+//// [tests/cases/compiler/moduleAugmentationImportsAndExports6.ts] ////
+
+//// [f1.ts]
+
+export class A {}
+
+//// [f2.ts]
+export class B {
+    n: number;
+}
+
+//// [f3.ts]
+import {A} from "./f1";
+import {B} from "./f2";
+
+A.prototype.foo = function () { return undefined; }
+
+export namespace N {
+    export interface Ifc { a: number; }
+    export interface Cls { b: number; }
+}
+import I = N.Ifc;
+import C = N.Cls;
+
+declare module "./f1" {
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+
+//// [f4.ts]
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
+let c = a.bar().a;
+let d = a.baz().b;
+
+//// [f1.js]
+"use strict";
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+exports.A = A;
+//// [f2.js]
+"use strict";
+var B = (function () {
+    function B() {
+    }
+    return B;
+}());
+exports.B = B;
+//// [f3.js]
+"use strict";
+var f1_1 = require("./f1");
+f1_1.A.prototype.foo = function () { return undefined; };
+//// [f4.js]
+"use strict";
+require("./f3");
+var a;
+var b = a.foo().n;
+var c = a.bar().a;
+var d = a.baz().b;
+
+
+//// [f1.d.ts]
+export declare class A {
+}
+//// [f2.d.ts]
+export declare class B {
+    n: number;
+}
+//// [f3.d.ts]
+import { B } from "./f2";
+export declare namespace N {
+    interface Ifc {
+        a: number;
+    }
+    interface Cls {
+        b: number;
+    }
+}
+import I = N.Ifc;
+import C = N.Cls;
+declare module "./f1" {
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+//// [f4.d.ts]
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports6.symbols b/tests/baselines/reference/moduleAugmentationImportsAndExports6.symbols
new file mode 100644
index 0000000000..92952ef94b
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports6.symbols
@@ -0,0 +1,101 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {}
+>A : Symbol(A, Decl(f1.ts, 0, 0), Decl(f3.ts, 12, 23))
+
+=== tests/cases/compiler/f2.ts ===
+export class B {
+>B : Symbol(B, Decl(f2.ts, 0, 0))
+
+    n: number;
+>n : Symbol(n, Decl(f2.ts, 0, 16))
+}
+
+=== tests/cases/compiler/f3.ts ===
+import {A} from "./f1";
+>A : Symbol(A, Decl(f3.ts, 0, 8))
+
+import {B} from "./f2";
+>B : Symbol(B, Decl(f3.ts, 1, 8))
+
+A.prototype.foo = function () { return undefined; }
+>A.prototype.foo : Symbol(A.foo, Decl(f3.ts, 13, 17))
+>A.prototype : Symbol(A.prototype)
+>A : Symbol(A, Decl(f3.ts, 0, 8))
+>prototype : Symbol(A.prototype)
+>foo : Symbol(A.foo, Decl(f3.ts, 13, 17))
+>undefined : Symbol(undefined)
+
+export namespace N {
+>N : Symbol(N, Decl(f3.ts, 3, 51))
+
+    export interface Ifc { a: number; }
+>Ifc : Symbol(Ifc, Decl(f3.ts, 5, 20))
+>a : Symbol(a, Decl(f3.ts, 6, 26))
+
+    export interface Cls { b: number; }
+>Cls : Symbol(Cls, Decl(f3.ts, 6, 39))
+>b : Symbol(b, Decl(f3.ts, 7, 26))
+}
+import I = N.Ifc;
+>I : Symbol(I, Decl(f3.ts, 8, 1))
+>N : Symbol(N, Decl(f3.ts, 3, 51))
+>Ifc : Symbol(I, Decl(f3.ts, 5, 20))
+
+import C = N.Cls;
+>C : Symbol(C, Decl(f3.ts, 9, 17))
+>N : Symbol(N, Decl(f3.ts, 3, 51))
+>Cls : Symbol(C, Decl(f3.ts, 6, 39))
+
+declare module "./f1" {
+    interface A {
+>A : Symbol(A, Decl(f1.ts, 0, 0), Decl(f3.ts, 12, 23))
+
+        foo(): B;
+>foo : Symbol(foo, Decl(f3.ts, 13, 17))
+>B : Symbol(B, Decl(f3.ts, 1, 8))
+
+        bar(): I;
+>bar : Symbol(bar, Decl(f3.ts, 14, 17))
+>I : Symbol(I, Decl(f3.ts, 8, 1))
+
+        baz(): C;
+>baz : Symbol(baz, Decl(f3.ts, 15, 17))
+>C : Symbol(C, Decl(f3.ts, 9, 17))
+    }
+}
+
+=== tests/cases/compiler/f4.ts ===
+import {A} from "./f1";
+>A : Symbol(A, Decl(f4.ts, 0, 8))
+
+import "./f3";
+
+let a: A;
+>a : Symbol(a, Decl(f4.ts, 3, 3))
+>A : Symbol(A, Decl(f4.ts, 0, 8))
+
+let b = a.foo().n;
+>b : Symbol(b, Decl(f4.ts, 4, 3))
+>a.foo().n : Symbol(B.n, Decl(f2.ts, 0, 16))
+>a.foo : Symbol(A.foo, Decl(f3.ts, 13, 17))
+>a : Symbol(a, Decl(f4.ts, 3, 3))
+>foo : Symbol(A.foo, Decl(f3.ts, 13, 17))
+>n : Symbol(B.n, Decl(f2.ts, 0, 16))
+
+let c = a.bar().a;
+>c : Symbol(c, Decl(f4.ts, 5, 3))
+>a.bar().a : Symbol(N.Ifc.a, Decl(f3.ts, 6, 26))
+>a.bar : Symbol(A.bar, Decl(f3.ts, 14, 17))
+>a : Symbol(a, Decl(f4.ts, 3, 3))
+>bar : Symbol(A.bar, Decl(f3.ts, 14, 17))
+>a : Symbol(N.Ifc.a, Decl(f3.ts, 6, 26))
+
+let d = a.baz().b;
+>d : Symbol(d, Decl(f4.ts, 6, 3))
+>a.baz().b : Symbol(N.Cls.b, Decl(f3.ts, 7, 26))
+>a.baz : Symbol(A.baz, Decl(f3.ts, 15, 17))
+>a : Symbol(a, Decl(f4.ts, 3, 3))
+>baz : Symbol(A.baz, Decl(f3.ts, 15, 17))
+>b : Symbol(N.Cls.b, Decl(f3.ts, 7, 26))
+
diff --git a/tests/baselines/reference/moduleAugmentationImportsAndExports6.types b/tests/baselines/reference/moduleAugmentationImportsAndExports6.types
new file mode 100644
index 0000000000..0c201599b5
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationImportsAndExports6.types
@@ -0,0 +1,106 @@
+=== tests/cases/compiler/f1.ts ===
+
+export class A {}
+>A : A
+
+=== tests/cases/compiler/f2.ts ===
+export class B {
+>B : B
+
+    n: number;
+>n : number
+}
+
+=== tests/cases/compiler/f3.ts ===
+import {A} from "./f1";
+>A : typeof A
+
+import {B} from "./f2";
+>B : typeof B
+
+A.prototype.foo = function () { return undefined; }
+>A.prototype.foo = function () { return undefined; } : () => any
+>A.prototype.foo : () => B
+>A.prototype : A
+>A : typeof A
+>prototype : A
+>foo : () => B
+>function () { return undefined; } : () => any
+>undefined : undefined
+
+export namespace N {
+>N : any
+
+    export interface Ifc { a: number; }
+>Ifc : Ifc
+>a : number
+
+    export interface Cls { b: number; }
+>Cls : Cls
+>b : number
+}
+import I = N.Ifc;
+>I : any
+>N : any
+>Ifc : I
+
+import C = N.Cls;
+>C : any
+>N : any
+>Cls : C
+
+declare module "./f1" {
+    interface A {
+>A : A
+
+        foo(): B;
+>foo : () => B
+>B : B
+
+        bar(): I;
+>bar : () => I
+>I : I
+
+        baz(): C;
+>baz : () => C
+>C : C
+    }
+}
+
+=== tests/cases/compiler/f4.ts ===
+import {A} from "./f1";
+>A : typeof A
+
+import "./f3";
+
+let a: A;
+>a : A
+>A : A
+
+let b = a.foo().n;
+>b : number
+>a.foo().n : number
+>a.foo() : B
+>a.foo : () => B
+>a : A
+>foo : () => B
+>n : number
+
+let c = a.bar().a;
+>c : number
+>a.bar().a : number
+>a.bar() : N.Ifc
+>a.bar : () => N.Ifc
+>a : A
+>bar : () => N.Ifc
+>a : number
+
+let d = a.baz().b;
+>d : number
+>a.baz().b : number
+>a.baz() : N.Cls
+>a.baz : () => N.Cls
+>a : A
+>baz : () => N.Cls
+>b : number
+
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule1.js b/tests/baselines/reference/moduleAugmentationInAmbientModule1.js
new file mode 100644
index 0000000000..aecb8954d5
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule1.js
@@ -0,0 +1,39 @@
+//// [tests/cases/compiler/moduleAugmentationInAmbientModule1.ts] ////
+
+//// [O.d.ts]
+
+
+declare module "Observable" {
+    class Observable {}
+}
+
+declare module "M" {
+    class Cls { x: number }
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+    module "Observable" {
+        interface Observable {
+            foo(): Cls;
+        }
+    }
+}
+
+//// [main.ts]
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+let x: Observable;
+x.foo().x;
+
+
+//// [main.js]
+/// <reference path="O.d.ts" />
+"use strict";
+var x;
+x.foo().x;
+
+
+//// [main.d.ts]
+/// <reference path="O.d.ts" />
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule1.symbols b/tests/baselines/reference/moduleAugmentationInAmbientModule1.symbols
new file mode 100644
index 0000000000..b59f0766ee
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule1.symbols
@@ -0,0 +1,46 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+
+let x: Observable;
+>x : Symbol(x, Decl(main.ts, 3, 3))
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+
+x.foo().x;
+>x.foo().x : Symbol(Cls.x, Decl(O.d.ts, 7, 15))
+>x.foo : Symbol(Observable.foo, Decl(O.d.ts, 13, 30))
+>x : Symbol(x, Decl(main.ts, 3, 3))
+>foo : Symbol(Observable.foo, Decl(O.d.ts, 13, 30))
+>x : Symbol(Cls.x, Decl(O.d.ts, 7, 15))
+
+=== tests/cases/compiler/O.d.ts ===
+
+
+declare module "Observable" {
+    class Observable {}
+>Observable : Symbol(Observable, Decl(O.d.ts, 2, 29), Decl(O.d.ts, 12, 25))
+}
+
+declare module "M" {
+    class Cls { x: number }
+>Cls : Symbol(Cls, Decl(O.d.ts, 6, 20))
+>x : Symbol(x, Decl(O.d.ts, 7, 15))
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+>Cls : Symbol(Cls, Decl(O.d.ts, 11, 12))
+
+    module "Observable" {
+        interface Observable {
+>Observable : Symbol(Observable, Decl(O.d.ts, 2, 29), Decl(O.d.ts, 12, 25))
+
+            foo(): Cls;
+>foo : Symbol(foo, Decl(O.d.ts, 13, 30))
+>Cls : Symbol(Cls, Decl(O.d.ts, 11, 12))
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule1.types b/tests/baselines/reference/moduleAugmentationInAmbientModule1.types
new file mode 100644
index 0000000000..0be2a787cb
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule1.types
@@ -0,0 +1,47 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+>Observable : typeof Observable
+
+let x: Observable;
+>x : Observable
+>Observable : Observable
+
+x.foo().x;
+>x.foo().x : number
+>x.foo() : Cls
+>x.foo : () => Cls
+>x : Observable
+>foo : () => Cls
+>x : number
+
+=== tests/cases/compiler/O.d.ts ===
+
+
+declare module "Observable" {
+    class Observable {}
+>Observable : Observable
+}
+
+declare module "M" {
+    class Cls { x: number }
+>Cls : Cls
+>x : number
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+>Cls : typeof Cls
+
+    module "Observable" {
+        interface Observable {
+>Observable : Observable
+
+            foo(): Cls;
+>foo : () => Cls
+>Cls : Cls
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule2.js b/tests/baselines/reference/moduleAugmentationInAmbientModule2.js
new file mode 100644
index 0000000000..5529afc674
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule2.js
@@ -0,0 +1,36 @@
+//// [tests/cases/compiler/moduleAugmentationInAmbientModule2.ts] ////
+
+//// [O.d.ts]
+
+declare module "Observable" {
+    class Observable {}
+}
+
+declare module "M" {
+    class Cls { x: number }
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+    module "Observable" {
+        interface Observable {
+            foo(): Cls;
+        }
+    }
+}
+
+//// [main.ts]
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+import "Map";
+let x: Observable;
+x.foo().x;
+
+
+//// [main.js]
+/// <reference path="O.d.ts" />
+"use strict";
+require("Map");
+var x;
+x.foo().x;
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule2.symbols b/tests/baselines/reference/moduleAugmentationInAmbientModule2.symbols
new file mode 100644
index 0000000000..6308e67b3b
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule2.symbols
@@ -0,0 +1,46 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+
+import "Map";
+let x: Observable;
+>x : Symbol(x, Decl(main.ts, 4, 3))
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+
+x.foo().x;
+>x.foo().x : Symbol(Cls.x, Decl(O.d.ts, 6, 15))
+>x.foo : Symbol(Observable.foo, Decl(O.d.ts, 12, 30))
+>x : Symbol(x, Decl(main.ts, 4, 3))
+>foo : Symbol(Observable.foo, Decl(O.d.ts, 12, 30))
+>x : Symbol(Cls.x, Decl(O.d.ts, 6, 15))
+
+=== tests/cases/compiler/O.d.ts ===
+
+declare module "Observable" {
+    class Observable {}
+>Observable : Symbol(Observable, Decl(O.d.ts, 1, 29), Decl(O.d.ts, 11, 25))
+}
+
+declare module "M" {
+    class Cls { x: number }
+>Cls : Symbol(Cls, Decl(O.d.ts, 5, 20))
+>x : Symbol(x, Decl(O.d.ts, 6, 15))
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+>Cls : Symbol(Cls, Decl(O.d.ts, 10, 12))
+
+    module "Observable" {
+        interface Observable {
+>Observable : Symbol(Observable, Decl(O.d.ts, 1, 29), Decl(O.d.ts, 11, 25))
+
+            foo(): Cls;
+>foo : Symbol(foo, Decl(O.d.ts, 12, 30))
+>Cls : Symbol(Cls, Decl(O.d.ts, 10, 12))
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule2.types b/tests/baselines/reference/moduleAugmentationInAmbientModule2.types
new file mode 100644
index 0000000000..31ea8904c2
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule2.types
@@ -0,0 +1,47 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+>Observable : typeof Observable
+
+import "Map";
+let x: Observable;
+>x : Observable
+>Observable : Observable
+
+x.foo().x;
+>x.foo().x : number
+>x.foo() : Cls
+>x.foo : () => Cls
+>x : Observable
+>foo : () => Cls
+>x : number
+
+=== tests/cases/compiler/O.d.ts ===
+
+declare module "Observable" {
+    class Observable {}
+>Observable : Observable
+}
+
+declare module "M" {
+    class Cls { x: number }
+>Cls : Cls
+>x : number
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+>Cls : typeof Cls
+
+    module "Observable" {
+        interface Observable {
+>Observable : Observable
+
+            foo(): Cls;
+>foo : () => Cls
+>Cls : Cls
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule3.js b/tests/baselines/reference/moduleAugmentationInAmbientModule3.js
new file mode 100644
index 0000000000..3a94c50ef1
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule3.js
@@ -0,0 +1,47 @@
+//// [tests/cases/compiler/moduleAugmentationInAmbientModule3.ts] ////
+
+//// [O.d.ts]
+
+declare module "Observable" {
+    class Observable {}
+}
+
+declare module "M" {
+    class Cls { x: number }
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+    module "Observable" {
+        interface Observable {
+            foo(): Cls;
+        }
+    }
+}
+
+declare module "Map" {
+    class Cls2 { x2: number }
+    module "Observable" {
+        interface Observable {
+            foo2(): Cls2;
+        }
+    }
+}
+
+//// [main.ts]
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+import "Map";
+let x: Observable;
+x.foo().x;
+x.foo2().x2;
+
+
+//// [main.js]
+/// <reference path="O.d.ts" />
+"use strict";
+require("Map");
+var x;
+x.foo().x;
+x.foo2().x2;
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule3.symbols b/tests/baselines/reference/moduleAugmentationInAmbientModule3.symbols
new file mode 100644
index 0000000000..34eea56753
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule3.symbols
@@ -0,0 +1,69 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+
+import "Map";
+let x: Observable;
+>x : Symbol(x, Decl(main.ts, 4, 3))
+>Observable : Symbol(Observable, Decl(main.ts, 2, 8))
+
+x.foo().x;
+>x.foo().x : Symbol(Cls.x, Decl(O.d.ts, 6, 15))
+>x.foo : Symbol(Observable.foo, Decl(O.d.ts, 12, 30))
+>x : Symbol(x, Decl(main.ts, 4, 3))
+>foo : Symbol(Observable.foo, Decl(O.d.ts, 12, 30))
+>x : Symbol(Cls.x, Decl(O.d.ts, 6, 15))
+
+x.foo2().x2;
+>x.foo2().x2 : Symbol(Cls2.x2, Decl(O.d.ts, 19, 16))
+>x.foo2 : Symbol(Observable.foo2, Decl(O.d.ts, 21, 30))
+>x : Symbol(x, Decl(main.ts, 4, 3))
+>foo2 : Symbol(Observable.foo2, Decl(O.d.ts, 21, 30))
+>x2 : Symbol(Cls2.x2, Decl(O.d.ts, 19, 16))
+
+=== tests/cases/compiler/O.d.ts ===
+
+declare module "Observable" {
+    class Observable {}
+>Observable : Symbol(Observable, Decl(O.d.ts, 1, 29), Decl(O.d.ts, 11, 25), Decl(O.d.ts, 20, 25))
+}
+
+declare module "M" {
+    class Cls { x: number }
+>Cls : Symbol(Cls, Decl(O.d.ts, 5, 20))
+>x : Symbol(x, Decl(O.d.ts, 6, 15))
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+>Cls : Symbol(Cls, Decl(O.d.ts, 10, 12))
+
+    module "Observable" {
+        interface Observable {
+>Observable : Symbol(Observable, Decl(O.d.ts, 1, 29), Decl(O.d.ts, 11, 25), Decl(O.d.ts, 20, 25))
+
+            foo(): Cls;
+>foo : Symbol(foo, Decl(O.d.ts, 12, 30))
+>Cls : Symbol(Cls, Decl(O.d.ts, 10, 12))
+        }
+    }
+}
+
+declare module "Map" {
+    class Cls2 { x2: number }
+>Cls2 : Symbol(Cls2, Decl(O.d.ts, 18, 22))
+>x2 : Symbol(x2, Decl(O.d.ts, 19, 16))
+
+    module "Observable" {
+        interface Observable {
+>Observable : Symbol(Observable, Decl(O.d.ts, 1, 29), Decl(O.d.ts, 11, 25), Decl(O.d.ts, 20, 25))
+
+            foo2(): Cls2;
+>foo2 : Symbol(foo2, Decl(O.d.ts, 21, 30))
+>Cls2 : Symbol(Cls2, Decl(O.d.ts, 18, 22))
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule3.types b/tests/baselines/reference/moduleAugmentationInAmbientModule3.types
new file mode 100644
index 0000000000..2cec5edc6b
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule3.types
@@ -0,0 +1,71 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+>Observable : typeof Observable
+
+import "Map";
+let x: Observable;
+>x : Observable
+>Observable : Observable
+
+x.foo().x;
+>x.foo().x : number
+>x.foo() : Cls
+>x.foo : () => Cls
+>x : Observable
+>foo : () => Cls
+>x : number
+
+x.foo2().x2;
+>x.foo2().x2 : number
+>x.foo2() : Cls2
+>x.foo2 : () => Cls2
+>x : Observable
+>foo2 : () => Cls2
+>x2 : number
+
+=== tests/cases/compiler/O.d.ts ===
+
+declare module "Observable" {
+    class Observable {}
+>Observable : Observable
+}
+
+declare module "M" {
+    class Cls { x: number }
+>Cls : Cls
+>x : number
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+>Cls : typeof Cls
+
+    module "Observable" {
+        interface Observable {
+>Observable : Observable
+
+            foo(): Cls;
+>foo : () => Cls
+>Cls : Cls
+        }
+    }
+}
+
+declare module "Map" {
+    class Cls2 { x2: number }
+>Cls2 : Cls2
+>x2 : number
+
+    module "Observable" {
+        interface Observable {
+>Observable : Observable
+
+            foo2(): Cls2;
+>foo2 : () => Cls2
+>Cls2 : Cls2
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule4.js b/tests/baselines/reference/moduleAugmentationInAmbientModule4.js
new file mode 100644
index 0000000000..bf0339d310
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule4.js
@@ -0,0 +1,50 @@
+//// [tests/cases/compiler/moduleAugmentationInAmbientModule4.ts] ////
+
+//// [O.d.ts]
+
+declare module "Observable" {
+    class Observable {}
+}
+
+declare module "M" {
+    class Cls { x: number }
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+    module "Observable" {
+        interface Observable {
+            foo(): Cls;
+        }
+    }
+}
+
+//// [O2.d.ts]
+declare module "Map" {
+    class Cls2 { x2: number }
+    module "Observable" {
+        interface Observable {
+            foo2(): Cls2;
+        }
+    }
+}
+
+//// [main.ts]
+/// <reference path="O.d.ts" />
+/// <reference path="O2.d.ts" />
+
+import {Observable} from "Observable";
+import "Map";
+let x: Observable;
+x.foo().x;
+x.foo2().x2;
+
+
+//// [main.js]
+/// <reference path="O.d.ts" />
+/// <reference path="O2.d.ts" />
+"use strict";
+require("Map");
+var x;
+x.foo().x;
+x.foo2().x2;
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule4.symbols b/tests/baselines/reference/moduleAugmentationInAmbientModule4.symbols
new file mode 100644
index 0000000000..55658c2a52
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule4.symbols
@@ -0,0 +1,71 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="O.d.ts" />
+/// <reference path="O2.d.ts" />
+
+import {Observable} from "Observable";
+>Observable : Symbol(Observable, Decl(main.ts, 3, 8))
+
+import "Map";
+let x: Observable;
+>x : Symbol(x, Decl(main.ts, 5, 3))
+>Observable : Symbol(Observable, Decl(main.ts, 3, 8))
+
+x.foo().x;
+>x.foo().x : Symbol(Cls.x, Decl(O.d.ts, 6, 15))
+>x.foo : Symbol(Observable.foo, Decl(O.d.ts, 12, 30))
+>x : Symbol(x, Decl(main.ts, 5, 3))
+>foo : Symbol(Observable.foo, Decl(O.d.ts, 12, 30))
+>x : Symbol(Cls.x, Decl(O.d.ts, 6, 15))
+
+x.foo2().x2;
+>x.foo2().x2 : Symbol(Cls2.x2, Decl(O2.d.ts, 1, 16))
+>x.foo2 : Symbol(Observable.foo2, Decl(O2.d.ts, 3, 30))
+>x : Symbol(x, Decl(main.ts, 5, 3))
+>foo2 : Symbol(Observable.foo2, Decl(O2.d.ts, 3, 30))
+>x2 : Symbol(Cls2.x2, Decl(O2.d.ts, 1, 16))
+
+=== tests/cases/compiler/O.d.ts ===
+
+declare module "Observable" {
+    class Observable {}
+>Observable : Symbol(Observable, Decl(O.d.ts, 1, 29), Decl(O.d.ts, 11, 25), Decl(O2.d.ts, 2, 25))
+}
+
+declare module "M" {
+    class Cls { x: number }
+>Cls : Symbol(Cls, Decl(O.d.ts, 5, 20))
+>x : Symbol(x, Decl(O.d.ts, 6, 15))
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+>Cls : Symbol(Cls, Decl(O.d.ts, 10, 12))
+
+    module "Observable" {
+        interface Observable {
+>Observable : Symbol(Observable, Decl(O.d.ts, 1, 29), Decl(O.d.ts, 11, 25), Decl(O2.d.ts, 2, 25))
+
+            foo(): Cls;
+>foo : Symbol(foo, Decl(O.d.ts, 12, 30))
+>Cls : Symbol(Cls, Decl(O.d.ts, 10, 12))
+        }
+    }
+}
+
+=== tests/cases/compiler/O2.d.ts ===
+declare module "Map" {
+    class Cls2 { x2: number }
+>Cls2 : Symbol(Cls2, Decl(O2.d.ts, 0, 22))
+>x2 : Symbol(x2, Decl(O2.d.ts, 1, 16))
+
+    module "Observable" {
+        interface Observable {
+>Observable : Symbol(Observable, Decl(O.d.ts, 1, 29), Decl(O.d.ts, 11, 25), Decl(O2.d.ts, 2, 25))
+
+            foo2(): Cls2;
+>foo2 : Symbol(foo2, Decl(O2.d.ts, 3, 30))
+>Cls2 : Symbol(Cls2, Decl(O2.d.ts, 0, 22))
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule4.types b/tests/baselines/reference/moduleAugmentationInAmbientModule4.types
new file mode 100644
index 0000000000..04791aef86
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule4.types
@@ -0,0 +1,73 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="O.d.ts" />
+/// <reference path="O2.d.ts" />
+
+import {Observable} from "Observable";
+>Observable : typeof Observable
+
+import "Map";
+let x: Observable;
+>x : Observable
+>Observable : Observable
+
+x.foo().x;
+>x.foo().x : number
+>x.foo() : Cls
+>x.foo : () => Cls
+>x : Observable
+>foo : () => Cls
+>x : number
+
+x.foo2().x2;
+>x.foo2().x2 : number
+>x.foo2() : Cls2
+>x.foo2 : () => Cls2
+>x : Observable
+>foo2 : () => Cls2
+>x2 : number
+
+=== tests/cases/compiler/O.d.ts ===
+
+declare module "Observable" {
+    class Observable {}
+>Observable : Observable
+}
+
+declare module "M" {
+    class Cls { x: number }
+>Cls : Cls
+>x : number
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+>Cls : typeof Cls
+
+    module "Observable" {
+        interface Observable {
+>Observable : Observable
+
+            foo(): Cls;
+>foo : () => Cls
+>Cls : Cls
+        }
+    }
+}
+
+=== tests/cases/compiler/O2.d.ts ===
+declare module "Map" {
+    class Cls2 { x2: number }
+>Cls2 : Cls2
+>x2 : number
+
+    module "Observable" {
+        interface Observable {
+>Observable : Observable
+
+            foo2(): Cls2;
+>foo2 : () => Cls2
+>Cls2 : Cls2
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule5.js b/tests/baselines/reference/moduleAugmentationInAmbientModule5.js
new file mode 100644
index 0000000000..fab9cebb17
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule5.js
@@ -0,0 +1,35 @@
+//// [tests/cases/compiler/moduleAugmentationInAmbientModule5.ts] ////
+
+//// [array.d.ts]
+
+declare module "A" {
+    class A { x: number; }
+}
+
+declare module "array" {
+    import {A} from "A";
+    global {
+        interface Array<T> {
+            getA(): A;
+        }
+    }
+}
+
+//// [f.ts]
+/// <reference path="array.d.ts"/>
+import "array";
+
+let x = [1];
+let y = x.getA().x;
+
+
+//// [f.js]
+"use strict";
+/// <reference path="array.d.ts"/>
+require("array");
+var x = [1];
+var y = x.getA().x;
+
+
+//// [f.d.ts]
+/// <reference path="array.d.ts" />
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule5.symbols b/tests/baselines/reference/moduleAugmentationInAmbientModule5.symbols
new file mode 100644
index 0000000000..a663efca64
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule5.symbols
@@ -0,0 +1,41 @@
+=== tests/cases/compiler/f.ts ===
+/// <reference path="array.d.ts"/>
+import "array";
+
+let x = [1];
+>x : Symbol(x, Decl(f.ts, 3, 3))
+
+let y = x.getA().x;
+>y : Symbol(y, Decl(f.ts, 4, 3))
+>x.getA().x : Symbol(A.x, Decl(array.d.ts, 2, 13))
+>x.getA : Symbol(Array.getA, Decl(array.d.ts, 8, 28))
+>x : Symbol(x, Decl(f.ts, 3, 3))
+>getA : Symbol(Array.getA, Decl(array.d.ts, 8, 28))
+>x : Symbol(A.x, Decl(array.d.ts, 2, 13))
+
+=== tests/cases/compiler/array.d.ts ===
+
+declare module "A" {
+    class A { x: number; }
+>A : Symbol(A, Decl(array.d.ts, 1, 20))
+>x : Symbol(x, Decl(array.d.ts, 2, 13))
+}
+
+declare module "array" {
+    import {A} from "A";
+>A : Symbol(A, Decl(array.d.ts, 6, 12))
+
+    global {
+>global : Symbol(, Decl(array.d.ts, 6, 24))
+
+        interface Array<T> {
+>Array : Symbol(Array, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(array.d.ts, 7, 12))
+>T : Symbol(T, Decl(lib.d.ts, --, --), Decl(array.d.ts, 8, 24))
+
+            getA(): A;
+>getA : Symbol(getA, Decl(array.d.ts, 8, 28))
+>A : Symbol(A, Decl(array.d.ts, 6, 12))
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationInAmbientModule5.types b/tests/baselines/reference/moduleAugmentationInAmbientModule5.types
new file mode 100644
index 0000000000..d04cdca489
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationInAmbientModule5.types
@@ -0,0 +1,44 @@
+=== tests/cases/compiler/f.ts ===
+/// <reference path="array.d.ts"/>
+import "array";
+
+let x = [1];
+>x : number[]
+>[1] : number[]
+>1 : number
+
+let y = x.getA().x;
+>y : number
+>x.getA().x : number
+>x.getA() : A
+>x.getA : () => A
+>x : number[]
+>getA : () => A
+>x : number
+
+=== tests/cases/compiler/array.d.ts ===
+
+declare module "A" {
+    class A { x: number; }
+>A : A
+>x : number
+}
+
+declare module "array" {
+    import {A} from "A";
+>A : typeof A
+
+    global {
+>global : typeof 
+
+        interface Array<T> {
+>Array : T[]
+>T : T
+
+            getA(): A;
+>getA : () => A
+>A : A
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationNoNewNames.errors.txt b/tests/baselines/reference/moduleAugmentationNoNewNames.errors.txt
new file mode 100644
index 0000000000..7c7f17cd64
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationNoNewNames.errors.txt
@@ -0,0 +1,47 @@
+tests/cases/compiler/map.ts(10,11): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/map.ts(11,9): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/map.ts(11,20): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/map.ts(12,13): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/map.ts(12,19): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/map.ts(13,12): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+
+
+==== tests/cases/compiler/map.ts (6 errors) ====
+    
+    import { Observable } from "./observable"
+    
+    (<any>Observable.prototype).map = function() { }
+    
+    declare module "./observable" {
+        interface Observable<T> {
+            map<U>(proj: (e:T) => U): Observable<U>
+        }
+        class Bar {}
+              ~~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        let y: number, z: string;
+            ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                       ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        let {a: x, b: x1}: {a: number, b: number};
+                ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+                      ~~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        module Z {}
+               ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+    }
+    
+==== tests/cases/compiler/observable.ts (0 errors) ====
+    export declare class Observable<T> {
+        filter(pred: (e:T) => boolean): Observable<T>;
+    }
+    
+==== tests/cases/compiler/main.ts (0 errors) ====
+    import { Observable } from "./observable"
+    import "./map";
+    
+    let x: Observable<number>;
+    let y = x.map(x => x + 1);
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleAugmentationNoNewNames.js b/tests/baselines/reference/moduleAugmentationNoNewNames.js
new file mode 100644
index 0000000000..ccd4a66849
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationNoNewNames.js
@@ -0,0 +1,41 @@
+//// [tests/cases/compiler/moduleAugmentationNoNewNames.ts] ////
+
+//// [map.ts]
+
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    class Bar {}
+    let y: number, z: string;
+    let {a: x, b: x1}: {a: number, b: number};
+    module Z {}
+}
+
+//// [observable.ts]
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+//// [main.ts]
+import { Observable } from "./observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
+
+//// [observable.js]
+"use strict";
+//// [map.js]
+"use strict";
+var observable_1 = require("./observable");
+observable_1.Observable.prototype.map = function () { };
+//// [main.js]
+"use strict";
+require("./map");
+var x;
+var y = x.map(function (x) { return x + 1; });
diff --git a/tests/baselines/reference/moduleAugmentationsBundledOutput1.js b/tests/baselines/reference/moduleAugmentationsBundledOutput1.js
new file mode 100644
index 0000000000..92916206e7
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsBundledOutput1.js
@@ -0,0 +1,142 @@
+//// [tests/cases/compiler/moduleAugmentationsBundledOutput1.ts] ////
+
+//// [m1.ts]
+
+export class Cls {
+}
+
+//// [m2.ts]
+import {Cls} from "./m1";
+(<any>Cls.prototype).foo = function() { return 1; };
+(<any>Cls.prototype).bar = function() { return "1"; };
+
+declare module "./m1" {
+    interface Cls {
+        foo(): number;
+    }
+}
+
+declare module "./m1" {
+    interface Cls {
+        bar(): string;
+    }
+}
+
+//// [m3.ts]
+export class C1 { x: number }
+export class C2 { x: string }
+
+//// [m4.ts]
+import {Cls} from "./m1";
+import {C1, C2} from "./m3";
+(<any>Cls.prototype).baz1 = function() { return undefined };
+(<any>Cls.prototype).baz2 = function() { return undefined };
+
+declare module "./m1" {
+    interface Cls {
+        baz1(): C1;
+    }
+}
+
+declare module "./m1" {
+    interface Cls {
+        baz2(): C2;
+    }
+}
+
+//// [test.ts]
+import { Cls } from "./m1";
+import "m2";
+import "m4";
+let c: Cls;
+c.foo().toExponential();
+c.bar().toLowerCase();
+c.baz1().x.toExponential();
+c.baz2().x.toLowerCase();
+
+
+//// [out.js]
+define("m1", ["require", "exports"], function (require, exports) {
+    "use strict";
+    var Cls = (function () {
+        function Cls() {
+        }
+        return Cls;
+    }());
+    exports.Cls = Cls;
+});
+define("m2", ["require", "exports", "m1"], function (require, exports, m1_1) {
+    "use strict";
+    m1_1.Cls.prototype.foo = function () { return 1; };
+    m1_1.Cls.prototype.bar = function () { return "1"; };
+});
+define("m3", ["require", "exports"], function (require, exports) {
+    "use strict";
+    var C1 = (function () {
+        function C1() {
+        }
+        return C1;
+    }());
+    exports.C1 = C1;
+    var C2 = (function () {
+        function C2() {
+        }
+        return C2;
+    }());
+    exports.C2 = C2;
+});
+define("m4", ["require", "exports", "m1"], function (require, exports, m1_2) {
+    "use strict";
+    m1_2.Cls.prototype.baz1 = function () { return undefined; };
+    m1_2.Cls.prototype.baz2 = function () { return undefined; };
+});
+define("test", ["require", "exports", "m2", "m4"], function (require, exports) {
+    "use strict";
+    var c;
+    c.foo().toExponential();
+    c.bar().toLowerCase();
+    c.baz1().x.toExponential();
+    c.baz2().x.toLowerCase();
+});
+
+
+//// [out.d.ts]
+declare module "m1" {
+    export class Cls {
+    }
+}
+declare module "m2" {
+    module "m1" {
+        interface Cls {
+            foo(): number;
+        }
+    }
+    module "m1" {
+        interface Cls {
+            bar(): string;
+        }
+    }
+}
+declare module "m3" {
+    export class C1 {
+        x: number;
+    }
+    export class C2 {
+        x: string;
+    }
+}
+declare module "m4" {
+    import { C1, C2 } from "m3";
+    module "m1" {
+        interface Cls {
+            baz1(): C1;
+        }
+    }
+    module "m1" {
+        interface Cls {
+            baz2(): C2;
+        }
+    }
+}
+declare module "test" {
+}
diff --git a/tests/baselines/reference/moduleAugmentationsBundledOutput1.symbols b/tests/baselines/reference/moduleAugmentationsBundledOutput1.symbols
new file mode 100644
index 0000000000..47160cbc17
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsBundledOutput1.symbols
@@ -0,0 +1,129 @@
+=== tests/cases/compiler/m1.ts ===
+
+export class Cls {
+>Cls : Symbol(Cls, Decl(m1.ts, 0, 0), Decl(m2.ts, 4, 23), Decl(m2.ts, 10, 23), Decl(m4.ts, 5, 23), Decl(m4.ts, 11, 23))
+}
+
+=== tests/cases/compiler/m2.ts ===
+import {Cls} from "./m1";
+>Cls : Symbol(Cls, Decl(m2.ts, 0, 8))
+
+(<any>Cls.prototype).foo = function() { return 1; };
+>Cls.prototype : Symbol(Cls.prototype)
+>Cls : Symbol(Cls, Decl(m2.ts, 0, 8))
+>prototype : Symbol(Cls.prototype)
+
+(<any>Cls.prototype).bar = function() { return "1"; };
+>Cls.prototype : Symbol(Cls.prototype)
+>Cls : Symbol(Cls, Decl(m2.ts, 0, 8))
+>prototype : Symbol(Cls.prototype)
+
+declare module "./m1" {
+    interface Cls {
+>Cls : Symbol(Cls, Decl(m1.ts, 0, 0), Decl(m2.ts, 4, 23), Decl(m2.ts, 10, 23), Decl(m4.ts, 5, 23), Decl(m4.ts, 11, 23))
+
+        foo(): number;
+>foo : Symbol(foo, Decl(m2.ts, 5, 19))
+    }
+}
+
+declare module "./m1" {
+    interface Cls {
+>Cls : Symbol(Cls, Decl(m1.ts, 0, 0), Decl(m2.ts, 4, 23), Decl(m2.ts, 10, 23), Decl(m4.ts, 5, 23), Decl(m4.ts, 11, 23))
+
+        bar(): string;
+>bar : Symbol(bar, Decl(m2.ts, 11, 19))
+    }
+}
+
+=== tests/cases/compiler/m3.ts ===
+export class C1 { x: number }
+>C1 : Symbol(C1, Decl(m3.ts, 0, 0))
+>x : Symbol(x, Decl(m3.ts, 0, 17))
+
+export class C2 { x: string }
+>C2 : Symbol(C2, Decl(m3.ts, 0, 29))
+>x : Symbol(x, Decl(m3.ts, 1, 17))
+
+=== tests/cases/compiler/m4.ts ===
+import {Cls} from "./m1";
+>Cls : Symbol(Cls, Decl(m4.ts, 0, 8))
+
+import {C1, C2} from "./m3";
+>C1 : Symbol(C1, Decl(m4.ts, 1, 8))
+>C2 : Symbol(C2, Decl(m4.ts, 1, 11))
+
+(<any>Cls.prototype).baz1 = function() { return undefined };
+>Cls.prototype : Symbol(Cls.prototype)
+>Cls : Symbol(Cls, Decl(m4.ts, 0, 8))
+>prototype : Symbol(Cls.prototype)
+>undefined : Symbol(undefined)
+
+(<any>Cls.prototype).baz2 = function() { return undefined };
+>Cls.prototype : Symbol(Cls.prototype)
+>Cls : Symbol(Cls, Decl(m4.ts, 0, 8))
+>prototype : Symbol(Cls.prototype)
+>undefined : Symbol(undefined)
+
+declare module "./m1" {
+    interface Cls {
+>Cls : Symbol(Cls, Decl(m1.ts, 0, 0), Decl(m2.ts, 4, 23), Decl(m2.ts, 10, 23), Decl(m4.ts, 5, 23), Decl(m4.ts, 11, 23))
+
+        baz1(): C1;
+>baz1 : Symbol(baz1, Decl(m4.ts, 6, 19))
+>C1 : Symbol(C1, Decl(m4.ts, 1, 8))
+    }
+}
+
+declare module "./m1" {
+    interface Cls {
+>Cls : Symbol(Cls, Decl(m1.ts, 0, 0), Decl(m2.ts, 4, 23), Decl(m2.ts, 10, 23), Decl(m4.ts, 5, 23), Decl(m4.ts, 11, 23))
+
+        baz2(): C2;
+>baz2 : Symbol(baz2, Decl(m4.ts, 12, 19))
+>C2 : Symbol(C2, Decl(m4.ts, 1, 11))
+    }
+}
+
+=== tests/cases/compiler/test.ts ===
+import { Cls } from "./m1";
+>Cls : Symbol(Cls, Decl(test.ts, 0, 8))
+
+import "m2";
+import "m4";
+let c: Cls;
+>c : Symbol(c, Decl(test.ts, 3, 3))
+>Cls : Symbol(Cls, Decl(test.ts, 0, 8))
+
+c.foo().toExponential();
+>c.foo().toExponential : Symbol(Number.toExponential, Decl(lib.d.ts, --, --))
+>c.foo : Symbol(Cls.foo, Decl(m2.ts, 5, 19))
+>c : Symbol(c, Decl(test.ts, 3, 3))
+>foo : Symbol(Cls.foo, Decl(m2.ts, 5, 19))
+>toExponential : Symbol(Number.toExponential, Decl(lib.d.ts, --, --))
+
+c.bar().toLowerCase();
+>c.bar().toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>c.bar : Symbol(Cls.bar, Decl(m2.ts, 11, 19))
+>c : Symbol(c, Decl(test.ts, 3, 3))
+>bar : Symbol(Cls.bar, Decl(m2.ts, 11, 19))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
+c.baz1().x.toExponential();
+>c.baz1().x.toExponential : Symbol(Number.toExponential, Decl(lib.d.ts, --, --))
+>c.baz1().x : Symbol(C1.x, Decl(m3.ts, 0, 17))
+>c.baz1 : Symbol(Cls.baz1, Decl(m4.ts, 6, 19))
+>c : Symbol(c, Decl(test.ts, 3, 3))
+>baz1 : Symbol(Cls.baz1, Decl(m4.ts, 6, 19))
+>x : Symbol(C1.x, Decl(m3.ts, 0, 17))
+>toExponential : Symbol(Number.toExponential, Decl(lib.d.ts, --, --))
+
+c.baz2().x.toLowerCase();
+>c.baz2().x.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>c.baz2().x : Symbol(C2.x, Decl(m3.ts, 1, 17))
+>c.baz2 : Symbol(Cls.baz2, Decl(m4.ts, 12, 19))
+>c : Symbol(c, Decl(test.ts, 3, 3))
+>baz2 : Symbol(Cls.baz2, Decl(m4.ts, 12, 19))
+>x : Symbol(C2.x, Decl(m3.ts, 1, 17))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
diff --git a/tests/baselines/reference/moduleAugmentationsBundledOutput1.types b/tests/baselines/reference/moduleAugmentationsBundledOutput1.types
new file mode 100644
index 0000000000..80e9127905
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsBundledOutput1.types
@@ -0,0 +1,163 @@
+=== tests/cases/compiler/m1.ts ===
+
+export class Cls {
+>Cls : Cls
+}
+
+=== tests/cases/compiler/m2.ts ===
+import {Cls} from "./m1";
+>Cls : typeof Cls
+
+(<any>Cls.prototype).foo = function() { return 1; };
+>(<any>Cls.prototype).foo = function() { return 1; } : () => number
+>(<any>Cls.prototype).foo : any
+>(<any>Cls.prototype) : any
+><any>Cls.prototype : any
+>Cls.prototype : Cls
+>Cls : typeof Cls
+>prototype : Cls
+>foo : any
+>function() { return 1; } : () => number
+>1 : number
+
+(<any>Cls.prototype).bar = function() { return "1"; };
+>(<any>Cls.prototype).bar = function() { return "1"; } : () => string
+>(<any>Cls.prototype).bar : any
+>(<any>Cls.prototype) : any
+><any>Cls.prototype : any
+>Cls.prototype : Cls
+>Cls : typeof Cls
+>prototype : Cls
+>bar : any
+>function() { return "1"; } : () => string
+>"1" : string
+
+declare module "./m1" {
+    interface Cls {
+>Cls : Cls
+
+        foo(): number;
+>foo : () => number
+    }
+}
+
+declare module "./m1" {
+    interface Cls {
+>Cls : Cls
+
+        bar(): string;
+>bar : () => string
+    }
+}
+
+=== tests/cases/compiler/m3.ts ===
+export class C1 { x: number }
+>C1 : C1
+>x : number
+
+export class C2 { x: string }
+>C2 : C2
+>x : string
+
+=== tests/cases/compiler/m4.ts ===
+import {Cls} from "./m1";
+>Cls : typeof Cls
+
+import {C1, C2} from "./m3";
+>C1 : typeof C1
+>C2 : typeof C2
+
+(<any>Cls.prototype).baz1 = function() { return undefined };
+>(<any>Cls.prototype).baz1 = function() { return undefined } : () => any
+>(<any>Cls.prototype).baz1 : any
+>(<any>Cls.prototype) : any
+><any>Cls.prototype : any
+>Cls.prototype : Cls
+>Cls : typeof Cls
+>prototype : Cls
+>baz1 : any
+>function() { return undefined } : () => any
+>undefined : undefined
+
+(<any>Cls.prototype).baz2 = function() { return undefined };
+>(<any>Cls.prototype).baz2 = function() { return undefined } : () => any
+>(<any>Cls.prototype).baz2 : any
+>(<any>Cls.prototype) : any
+><any>Cls.prototype : any
+>Cls.prototype : Cls
+>Cls : typeof Cls
+>prototype : Cls
+>baz2 : any
+>function() { return undefined } : () => any
+>undefined : undefined
+
+declare module "./m1" {
+    interface Cls {
+>Cls : Cls
+
+        baz1(): C1;
+>baz1 : () => C1
+>C1 : C1
+    }
+}
+
+declare module "./m1" {
+    interface Cls {
+>Cls : Cls
+
+        baz2(): C2;
+>baz2 : () => C2
+>C2 : C2
+    }
+}
+
+=== tests/cases/compiler/test.ts ===
+import { Cls } from "./m1";
+>Cls : typeof Cls
+
+import "m2";
+import "m4";
+let c: Cls;
+>c : Cls
+>Cls : Cls
+
+c.foo().toExponential();
+>c.foo().toExponential() : string
+>c.foo().toExponential : (fractionDigits?: number) => string
+>c.foo() : number
+>c.foo : () => number
+>c : Cls
+>foo : () => number
+>toExponential : (fractionDigits?: number) => string
+
+c.bar().toLowerCase();
+>c.bar().toLowerCase() : string
+>c.bar().toLowerCase : () => string
+>c.bar() : string
+>c.bar : () => string
+>c : Cls
+>bar : () => string
+>toLowerCase : () => string
+
+c.baz1().x.toExponential();
+>c.baz1().x.toExponential() : string
+>c.baz1().x.toExponential : (fractionDigits?: number) => string
+>c.baz1().x : number
+>c.baz1() : C1
+>c.baz1 : () => C1
+>c : Cls
+>baz1 : () => C1
+>x : number
+>toExponential : (fractionDigits?: number) => string
+
+c.baz2().x.toLowerCase();
+>c.baz2().x.toLowerCase() : string
+>c.baz2().x.toLowerCase : () => string
+>c.baz2().x : string
+>c.baz2() : C2
+>c.baz2 : () => C2
+>c : Cls
+>baz2 : () => C2
+>x : string
+>toLowerCase : () => string
+
diff --git a/tests/baselines/reference/moduleAugmentationsImports1.js b/tests/baselines/reference/moduleAugmentationsImports1.js
new file mode 100644
index 0000000000..2c635a0719
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports1.js
@@ -0,0 +1,104 @@
+//// [tests/cases/compiler/moduleAugmentationsImports1.ts] ////
+
+//// [a.ts]
+
+export class A {}
+
+//// [b.ts]
+export class B {x: number;}
+
+//// [c.d.ts]
+declare module "C" {
+    class Cls {y: string; }
+}
+
+//// [d.ts]
+/// <reference path="c.d.ts"/>
+
+import {A} from "./a";
+import {B} from "./b";
+import {Cls} from "C";
+
+A.prototype.getB = function () { return undefined; }
+A.prototype.getCls = function () { return undefined; }
+
+declare module "./a" {
+    interface A {
+        getB(): B;
+    }
+}
+
+declare module "./a" {
+    interface A {
+        getCls(): Cls;
+    }
+}
+
+//// [main.ts]
+import {A} from "./a";
+import "d";
+
+let a: A;
+let b = a.getB().x.toFixed();
+let c = a.getCls().y.toLowerCase();
+
+//// [f.js]
+define("a", ["require", "exports"], function (require, exports) {
+    "use strict";
+    var A = (function () {
+        function A() {
+        }
+        return A;
+    }());
+    exports.A = A;
+});
+define("b", ["require", "exports"], function (require, exports) {
+    "use strict";
+    var B = (function () {
+        function B() {
+        }
+        return B;
+    }());
+    exports.B = B;
+});
+/// <reference path="c.d.ts"/>
+define("d", ["require", "exports", "a"], function (require, exports, a_1) {
+    "use strict";
+    a_1.A.prototype.getB = function () { return undefined; };
+    a_1.A.prototype.getCls = function () { return undefined; };
+});
+define("main", ["require", "exports", "d"], function (require, exports) {
+    "use strict";
+    var a;
+    var b = a.getB().x.toFixed();
+    var c = a.getCls().y.toLowerCase();
+});
+
+
+//// [f.d.ts]
+/// <reference path="tests/cases/compiler/c.d.ts" />
+declare module "a" {
+    export class A {
+    }
+}
+declare module "b" {
+    export class B {
+        x: number;
+    }
+}
+declare module "d" {
+    import { B } from "b";
+    import { Cls } from "C";
+    module "a" {
+        interface A {
+            getB(): B;
+        }
+    }
+    module "a" {
+        interface A {
+            getCls(): Cls;
+        }
+    }
+}
+declare module "main" {
+}
diff --git a/tests/baselines/reference/moduleAugmentationsImports1.symbols b/tests/baselines/reference/moduleAugmentationsImports1.symbols
new file mode 100644
index 0000000000..38ef8f5522
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports1.symbols
@@ -0,0 +1,95 @@
+=== tests/cases/compiler/a.ts ===
+
+export class A {}
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.ts, 9, 22), Decl(d.ts, 15, 22))
+
+=== tests/cases/compiler/b.ts ===
+export class B {x: number;}
+>B : Symbol(B, Decl(b.ts, 0, 0))
+>x : Symbol(x, Decl(b.ts, 0, 16))
+
+=== tests/cases/compiler/c.d.ts ===
+declare module "C" {
+    class Cls {y: string; }
+>Cls : Symbol(Cls, Decl(c.d.ts, 0, 20))
+>y : Symbol(y, Decl(c.d.ts, 1, 15))
+}
+
+=== tests/cases/compiler/d.ts ===
+/// <reference path="c.d.ts"/>
+
+import {A} from "./a";
+>A : Symbol(A, Decl(d.ts, 2, 8))
+
+import {B} from "./b";
+>B : Symbol(B, Decl(d.ts, 3, 8))
+
+import {Cls} from "C";
+>Cls : Symbol(Cls, Decl(d.ts, 4, 8))
+
+A.prototype.getB = function () { return undefined; }
+>A.prototype.getB : Symbol(A.getB, Decl(d.ts, 10, 17))
+>A.prototype : Symbol(A.prototype)
+>A : Symbol(A, Decl(d.ts, 2, 8))
+>prototype : Symbol(A.prototype)
+>getB : Symbol(A.getB, Decl(d.ts, 10, 17))
+>undefined : Symbol(undefined)
+
+A.prototype.getCls = function () { return undefined; }
+>A.prototype.getCls : Symbol(A.getCls, Decl(d.ts, 16, 17))
+>A.prototype : Symbol(A.prototype)
+>A : Symbol(A, Decl(d.ts, 2, 8))
+>prototype : Symbol(A.prototype)
+>getCls : Symbol(A.getCls, Decl(d.ts, 16, 17))
+>undefined : Symbol(undefined)
+
+declare module "./a" {
+    interface A {
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.ts, 9, 22), Decl(d.ts, 15, 22))
+
+        getB(): B;
+>getB : Symbol(getB, Decl(d.ts, 10, 17))
+>B : Symbol(B, Decl(d.ts, 3, 8))
+    }
+}
+
+declare module "./a" {
+    interface A {
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.ts, 9, 22), Decl(d.ts, 15, 22))
+
+        getCls(): Cls;
+>getCls : Symbol(getCls, Decl(d.ts, 16, 17))
+>Cls : Symbol(Cls, Decl(d.ts, 4, 8))
+    }
+}
+
+=== tests/cases/compiler/main.ts ===
+import {A} from "./a";
+>A : Symbol(A, Decl(main.ts, 0, 8))
+
+import "d";
+
+let a: A;
+>a : Symbol(a, Decl(main.ts, 3, 3))
+>A : Symbol(A, Decl(main.ts, 0, 8))
+
+let b = a.getB().x.toFixed();
+>b : Symbol(b, Decl(main.ts, 4, 3))
+>a.getB().x.toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+>a.getB().x : Symbol(B.x, Decl(b.ts, 0, 16))
+>a.getB : Symbol(A.getB, Decl(d.ts, 10, 17))
+>a : Symbol(a, Decl(main.ts, 3, 3))
+>getB : Symbol(A.getB, Decl(d.ts, 10, 17))
+>x : Symbol(B.x, Decl(b.ts, 0, 16))
+>toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+
+let c = a.getCls().y.toLowerCase();
+>c : Symbol(c, Decl(main.ts, 5, 3))
+>a.getCls().y.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>a.getCls().y : Symbol(Cls.y, Decl(c.d.ts, 1, 15))
+>a.getCls : Symbol(A.getCls, Decl(d.ts, 16, 17))
+>a : Symbol(a, Decl(main.ts, 3, 3))
+>getCls : Symbol(A.getCls, Decl(d.ts, 16, 17))
+>y : Symbol(Cls.y, Decl(c.d.ts, 1, 15))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
diff --git a/tests/baselines/reference/moduleAugmentationsImports1.types b/tests/baselines/reference/moduleAugmentationsImports1.types
new file mode 100644
index 0000000000..bf0bfee0a7
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports1.types
@@ -0,0 +1,103 @@
+=== tests/cases/compiler/a.ts ===
+
+export class A {}
+>A : A
+
+=== tests/cases/compiler/b.ts ===
+export class B {x: number;}
+>B : B
+>x : number
+
+=== tests/cases/compiler/c.d.ts ===
+declare module "C" {
+    class Cls {y: string; }
+>Cls : Cls
+>y : string
+}
+
+=== tests/cases/compiler/d.ts ===
+/// <reference path="c.d.ts"/>
+
+import {A} from "./a";
+>A : typeof A
+
+import {B} from "./b";
+>B : typeof B
+
+import {Cls} from "C";
+>Cls : typeof Cls
+
+A.prototype.getB = function () { return undefined; }
+>A.prototype.getB = function () { return undefined; } : () => any
+>A.prototype.getB : () => B
+>A.prototype : A
+>A : typeof A
+>prototype : A
+>getB : () => B
+>function () { return undefined; } : () => any
+>undefined : undefined
+
+A.prototype.getCls = function () { return undefined; }
+>A.prototype.getCls = function () { return undefined; } : () => any
+>A.prototype.getCls : () => Cls
+>A.prototype : A
+>A : typeof A
+>prototype : A
+>getCls : () => Cls
+>function () { return undefined; } : () => any
+>undefined : undefined
+
+declare module "./a" {
+    interface A {
+>A : A
+
+        getB(): B;
+>getB : () => B
+>B : B
+    }
+}
+
+declare module "./a" {
+    interface A {
+>A : A
+
+        getCls(): Cls;
+>getCls : () => Cls
+>Cls : Cls
+    }
+}
+
+=== tests/cases/compiler/main.ts ===
+import {A} from "./a";
+>A : typeof A
+
+import "d";
+
+let a: A;
+>a : A
+>A : A
+
+let b = a.getB().x.toFixed();
+>b : string
+>a.getB().x.toFixed() : string
+>a.getB().x.toFixed : (fractionDigits?: number) => string
+>a.getB().x : number
+>a.getB() : B
+>a.getB : () => B
+>a : A
+>getB : () => B
+>x : number
+>toFixed : (fractionDigits?: number) => string
+
+let c = a.getCls().y.toLowerCase();
+>c : string
+>a.getCls().y.toLowerCase() : string
+>a.getCls().y.toLowerCase : () => string
+>a.getCls().y : string
+>a.getCls() : Cls
+>a.getCls : () => Cls
+>a : A
+>getCls : () => Cls
+>y : string
+>toLowerCase : () => string
+
diff --git a/tests/baselines/reference/moduleAugmentationsImports2.js b/tests/baselines/reference/moduleAugmentationsImports2.js
new file mode 100644
index 0000000000..f70426b49b
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports2.js
@@ -0,0 +1,114 @@
+//// [tests/cases/compiler/moduleAugmentationsImports2.ts] ////
+
+//// [a.ts]
+
+export class A {}
+
+//// [b.ts]
+export class B {x: number;}
+
+//// [c.d.ts]
+declare module "C" {
+    class Cls {y: string; }
+}
+
+//// [d.ts]
+/// <reference path="c.d.ts"/>
+
+import {A} from "./a";
+import {B} from "./b";
+
+A.prototype.getB = function () { return undefined; }
+
+declare module "./a" {
+    interface A {
+        getB(): B;
+    }
+}
+
+//// [e.ts]
+import {A} from "./a";
+import {Cls} from "C";
+
+A.prototype.getCls = function () { return undefined; }
+
+declare module "./a" {
+    interface A {
+        getCls(): Cls;
+    }
+}
+
+//// [main.ts]
+import {A} from "./a";
+import "d";
+import "e";
+
+let a: A;
+let b = a.getB().x.toFixed();
+let c = a.getCls().y.toLowerCase();
+
+//// [f.js]
+define("a", ["require", "exports"], function (require, exports) {
+    "use strict";
+    var A = (function () {
+        function A() {
+        }
+        return A;
+    }());
+    exports.A = A;
+});
+define("b", ["require", "exports"], function (require, exports) {
+    "use strict";
+    var B = (function () {
+        function B() {
+        }
+        return B;
+    }());
+    exports.B = B;
+});
+/// <reference path="c.d.ts"/>
+define("d", ["require", "exports", "a"], function (require, exports, a_1) {
+    "use strict";
+    a_1.A.prototype.getB = function () { return undefined; };
+});
+define("e", ["require", "exports", "a"], function (require, exports, a_2) {
+    "use strict";
+    a_2.A.prototype.getCls = function () { return undefined; };
+});
+define("main", ["require", "exports", "d", "e"], function (require, exports) {
+    "use strict";
+    var a;
+    var b = a.getB().x.toFixed();
+    var c = a.getCls().y.toLowerCase();
+});
+
+
+//// [f.d.ts]
+/// <reference path="tests/cases/compiler/c.d.ts" />
+declare module "a" {
+    export class A {
+    }
+}
+declare module "b" {
+    export class B {
+        x: number;
+    }
+}
+declare module "d" {
+    import { B } from "b";
+    module "a" {
+        interface A {
+            getB(): B;
+        }
+    }
+}
+declare module "e" {
+    import { Cls } from "C";
+    module "a" {
+        interface A {
+            getCls(): Cls;
+        }
+    }
+}
+declare module "main" {
+}
diff --git a/tests/baselines/reference/moduleAugmentationsImports2.symbols b/tests/baselines/reference/moduleAugmentationsImports2.symbols
new file mode 100644
index 0000000000..643ccf20eb
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports2.symbols
@@ -0,0 +1,100 @@
+=== tests/cases/compiler/a.ts ===
+
+export class A {}
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.ts, 7, 22), Decl(e.ts, 5, 22))
+
+=== tests/cases/compiler/b.ts ===
+export class B {x: number;}
+>B : Symbol(B, Decl(b.ts, 0, 0))
+>x : Symbol(x, Decl(b.ts, 0, 16))
+
+=== tests/cases/compiler/c.d.ts ===
+declare module "C" {
+    class Cls {y: string; }
+>Cls : Symbol(Cls, Decl(c.d.ts, 0, 20))
+>y : Symbol(y, Decl(c.d.ts, 1, 15))
+}
+
+=== tests/cases/compiler/d.ts ===
+/// <reference path="c.d.ts"/>
+
+import {A} from "./a";
+>A : Symbol(A, Decl(d.ts, 2, 8))
+
+import {B} from "./b";
+>B : Symbol(B, Decl(d.ts, 3, 8))
+
+A.prototype.getB = function () { return undefined; }
+>A.prototype.getB : Symbol(A.getB, Decl(d.ts, 8, 17))
+>A.prototype : Symbol(A.prototype)
+>A : Symbol(A, Decl(d.ts, 2, 8))
+>prototype : Symbol(A.prototype)
+>getB : Symbol(A.getB, Decl(d.ts, 8, 17))
+>undefined : Symbol(undefined)
+
+declare module "./a" {
+    interface A {
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.ts, 7, 22), Decl(e.ts, 5, 22))
+
+        getB(): B;
+>getB : Symbol(getB, Decl(d.ts, 8, 17))
+>B : Symbol(B, Decl(d.ts, 3, 8))
+    }
+}
+
+=== tests/cases/compiler/e.ts ===
+import {A} from "./a";
+>A : Symbol(A, Decl(e.ts, 0, 8))
+
+import {Cls} from "C";
+>Cls : Symbol(Cls, Decl(e.ts, 1, 8))
+
+A.prototype.getCls = function () { return undefined; }
+>A.prototype.getCls : Symbol(A.getCls, Decl(e.ts, 6, 17))
+>A.prototype : Symbol(A.prototype)
+>A : Symbol(A, Decl(e.ts, 0, 8))
+>prototype : Symbol(A.prototype)
+>getCls : Symbol(A.getCls, Decl(e.ts, 6, 17))
+>undefined : Symbol(undefined)
+
+declare module "./a" {
+    interface A {
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.ts, 7, 22), Decl(e.ts, 5, 22))
+
+        getCls(): Cls;
+>getCls : Symbol(getCls, Decl(e.ts, 6, 17))
+>Cls : Symbol(Cls, Decl(e.ts, 1, 8))
+    }
+}
+
+=== tests/cases/compiler/main.ts ===
+import {A} from "./a";
+>A : Symbol(A, Decl(main.ts, 0, 8))
+
+import "d";
+import "e";
+
+let a: A;
+>a : Symbol(a, Decl(main.ts, 4, 3))
+>A : Symbol(A, Decl(main.ts, 0, 8))
+
+let b = a.getB().x.toFixed();
+>b : Symbol(b, Decl(main.ts, 5, 3))
+>a.getB().x.toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+>a.getB().x : Symbol(B.x, Decl(b.ts, 0, 16))
+>a.getB : Symbol(A.getB, Decl(d.ts, 8, 17))
+>a : Symbol(a, Decl(main.ts, 4, 3))
+>getB : Symbol(A.getB, Decl(d.ts, 8, 17))
+>x : Symbol(B.x, Decl(b.ts, 0, 16))
+>toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+
+let c = a.getCls().y.toLowerCase();
+>c : Symbol(c, Decl(main.ts, 6, 3))
+>a.getCls().y.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>a.getCls().y : Symbol(Cls.y, Decl(c.d.ts, 1, 15))
+>a.getCls : Symbol(A.getCls, Decl(e.ts, 6, 17))
+>a : Symbol(a, Decl(main.ts, 4, 3))
+>getCls : Symbol(A.getCls, Decl(e.ts, 6, 17))
+>y : Symbol(Cls.y, Decl(c.d.ts, 1, 15))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
diff --git a/tests/baselines/reference/moduleAugmentationsImports2.types b/tests/baselines/reference/moduleAugmentationsImports2.types
new file mode 100644
index 0000000000..56b4062560
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports2.types
@@ -0,0 +1,108 @@
+=== tests/cases/compiler/a.ts ===
+
+export class A {}
+>A : A
+
+=== tests/cases/compiler/b.ts ===
+export class B {x: number;}
+>B : B
+>x : number
+
+=== tests/cases/compiler/c.d.ts ===
+declare module "C" {
+    class Cls {y: string; }
+>Cls : Cls
+>y : string
+}
+
+=== tests/cases/compiler/d.ts ===
+/// <reference path="c.d.ts"/>
+
+import {A} from "./a";
+>A : typeof A
+
+import {B} from "./b";
+>B : typeof B
+
+A.prototype.getB = function () { return undefined; }
+>A.prototype.getB = function () { return undefined; } : () => any
+>A.prototype.getB : () => B
+>A.prototype : A
+>A : typeof A
+>prototype : A
+>getB : () => B
+>function () { return undefined; } : () => any
+>undefined : undefined
+
+declare module "./a" {
+    interface A {
+>A : A
+
+        getB(): B;
+>getB : () => B
+>B : B
+    }
+}
+
+=== tests/cases/compiler/e.ts ===
+import {A} from "./a";
+>A : typeof A
+
+import {Cls} from "C";
+>Cls : typeof Cls
+
+A.prototype.getCls = function () { return undefined; }
+>A.prototype.getCls = function () { return undefined; } : () => any
+>A.prototype.getCls : () => Cls
+>A.prototype : A
+>A : typeof A
+>prototype : A
+>getCls : () => Cls
+>function () { return undefined; } : () => any
+>undefined : undefined
+
+declare module "./a" {
+    interface A {
+>A : A
+
+        getCls(): Cls;
+>getCls : () => Cls
+>Cls : Cls
+    }
+}
+
+=== tests/cases/compiler/main.ts ===
+import {A} from "./a";
+>A : typeof A
+
+import "d";
+import "e";
+
+let a: A;
+>a : A
+>A : A
+
+let b = a.getB().x.toFixed();
+>b : string
+>a.getB().x.toFixed() : string
+>a.getB().x.toFixed : (fractionDigits?: number) => string
+>a.getB().x : number
+>a.getB() : B
+>a.getB : () => B
+>a : A
+>getB : () => B
+>x : number
+>toFixed : (fractionDigits?: number) => string
+
+let c = a.getCls().y.toLowerCase();
+>c : string
+>a.getCls().y.toLowerCase() : string
+>a.getCls().y.toLowerCase : () => string
+>a.getCls().y : string
+>a.getCls() : Cls
+>a.getCls : () => Cls
+>a : A
+>getCls : () => Cls
+>y : string
+>toLowerCase : () => string
+
diff --git a/tests/baselines/reference/moduleAugmentationsImports3.js b/tests/baselines/reference/moduleAugmentationsImports3.js
new file mode 100644
index 0000000000..3654583b5c
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports3.js
@@ -0,0 +1,101 @@
+//// [tests/cases/compiler/moduleAugmentationsImports3.ts] ////
+
+//// [a.ts]
+
+export class A {}
+
+//// [b.ts]
+export class B {x: number;}
+
+//// [c.d.ts]
+declare module "C" {
+    class Cls {y: string; }
+}
+
+//// [d.d.ts]
+declare module "D" {
+    import {A} from "a";
+    import {B} from "b";
+    module "a" {
+        interface A {
+            getB(): B;
+        }
+    }
+}
+
+//// [e.ts]
+/// <reference path="c.d.ts"/>
+import {A} from "./a";
+import {Cls} from "C";
+
+A.prototype.getCls = function () { return undefined; }
+
+declare module "./a" {
+    interface A {
+        getCls(): Cls;
+    }
+}
+
+//// [main.ts]
+/// <reference path="d.d.ts"/>
+import {A} from "./a";
+import "D";
+import "e";
+
+let a: A;
+let b = a.getB().x.toFixed();
+let c = a.getCls().y.toLowerCase();
+
+//// [f.js]
+define("a", ["require", "exports"], function (require, exports) {
+    "use strict";
+    var A = (function () {
+        function A() {
+        }
+        return A;
+    }());
+    exports.A = A;
+});
+define("b", ["require", "exports"], function (require, exports) {
+    "use strict";
+    var B = (function () {
+        function B() {
+        }
+        return B;
+    }());
+    exports.B = B;
+});
+define("e", ["require", "exports", "a"], function (require, exports, a_1) {
+    "use strict";
+    a_1.A.prototype.getCls = function () { return undefined; };
+});
+define("main", ["require", "exports", "D", "e"], function (require, exports) {
+    "use strict";
+    var a;
+    var b = a.getB().x.toFixed();
+    var c = a.getCls().y.toLowerCase();
+});
+
+
+//// [f.d.ts]
+/// <reference path="tests/cases/compiler/c.d.ts" />
+/// <reference path="tests/cases/compiler/d.d.ts" />
+declare module "a" {
+    export class A {
+    }
+}
+declare module "b" {
+    export class B {
+        x: number;
+    }
+}
+declare module "e" {
+    import { Cls } from "C";
+    module "a" {
+        interface A {
+            getCls(): Cls;
+        }
+    }
+}
+declare module "main" {
+}
diff --git a/tests/baselines/reference/moduleAugmentationsImports3.symbols b/tests/baselines/reference/moduleAugmentationsImports3.symbols
new file mode 100644
index 0000000000..db8eee074c
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports3.symbols
@@ -0,0 +1,94 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="d.d.ts"/>
+import {A} from "./a";
+>A : Symbol(A, Decl(main.ts, 1, 8))
+
+import "D";
+import "e";
+
+let a: A;
+>a : Symbol(a, Decl(main.ts, 5, 3))
+>A : Symbol(A, Decl(main.ts, 1, 8))
+
+let b = a.getB().x.toFixed();
+>b : Symbol(b, Decl(main.ts, 6, 3))
+>a.getB().x.toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+>a.getB().x : Symbol(B.x, Decl(b.ts, 0, 16))
+>a.getB : Symbol(A.getB, Decl(d.d.ts, 4, 21))
+>a : Symbol(a, Decl(main.ts, 5, 3))
+>getB : Symbol(A.getB, Decl(d.d.ts, 4, 21))
+>x : Symbol(B.x, Decl(b.ts, 0, 16))
+>toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+
+let c = a.getCls().y.toLowerCase();
+>c : Symbol(c, Decl(main.ts, 7, 3))
+>a.getCls().y.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>a.getCls().y : Symbol(Cls.y, Decl(c.d.ts, 1, 15))
+>a.getCls : Symbol(A.getCls, Decl(e.ts, 7, 17))
+>a : Symbol(a, Decl(main.ts, 5, 3))
+>getCls : Symbol(A.getCls, Decl(e.ts, 7, 17))
+>y : Symbol(Cls.y, Decl(c.d.ts, 1, 15))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
+=== tests/cases/compiler/a.ts ===
+
+export class A {}
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.d.ts, 3, 16), Decl(e.ts, 6, 22))
+
+=== tests/cases/compiler/b.ts ===
+export class B {x: number;}
+>B : Symbol(B, Decl(b.ts, 0, 0))
+>x : Symbol(x, Decl(b.ts, 0, 16))
+
+=== tests/cases/compiler/c.d.ts ===
+declare module "C" {
+    class Cls {y: string; }
+>Cls : Symbol(Cls, Decl(c.d.ts, 0, 20))
+>y : Symbol(y, Decl(c.d.ts, 1, 15))
+}
+
+=== tests/cases/compiler/d.d.ts ===
+declare module "D" {
+    import {A} from "a";
+>A : Symbol(A, Decl(d.d.ts, 1, 12))
+
+    import {B} from "b";
+>B : Symbol(B, Decl(d.d.ts, 2, 12))
+
+    module "a" {
+        interface A {
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.d.ts, 3, 16), Decl(e.ts, 6, 22))
+
+            getB(): B;
+>getB : Symbol(getB, Decl(d.d.ts, 4, 21))
+>B : Symbol(B, Decl(d.d.ts, 2, 12))
+        }
+    }
+}
+
+=== tests/cases/compiler/e.ts ===
+/// <reference path="c.d.ts"/>
+import {A} from "./a";
+>A : Symbol(A, Decl(e.ts, 1, 8))
+
+import {Cls} from "C";
+>Cls : Symbol(Cls, Decl(e.ts, 2, 8))
+
+A.prototype.getCls = function () { return undefined; }
+>A.prototype.getCls : Symbol(A.getCls, Decl(e.ts, 7, 17))
+>A.prototype : Symbol(A.prototype)
+>A : Symbol(A, Decl(e.ts, 1, 8))
+>prototype : Symbol(A.prototype)
+>getCls : Symbol(A.getCls, Decl(e.ts, 7, 17))
+>undefined : Symbol(undefined)
+
+declare module "./a" {
+    interface A {
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.d.ts, 3, 16), Decl(e.ts, 6, 22))
+
+        getCls(): Cls;
+>getCls : Symbol(getCls, Decl(e.ts, 7, 17))
+>Cls : Symbol(Cls, Decl(e.ts, 2, 8))
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationsImports3.types b/tests/baselines/reference/moduleAugmentationsImports3.types
new file mode 100644
index 0000000000..04d17296c5
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports3.types
@@ -0,0 +1,100 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="d.d.ts"/>
+import {A} from "./a";
+>A : typeof A
+
+import "D";
+import "e";
+
+let a: A;
+>a : A
+>A : A
+
+let b = a.getB().x.toFixed();
+>b : string
+>a.getB().x.toFixed() : string
+>a.getB().x.toFixed : (fractionDigits?: number) => string
+>a.getB().x : number
+>a.getB() : B
+>a.getB : () => B
+>a : A
+>getB : () => B
+>x : number
+>toFixed : (fractionDigits?: number) => string
+
+let c = a.getCls().y.toLowerCase();
+>c : string
+>a.getCls().y.toLowerCase() : string
+>a.getCls().y.toLowerCase : () => string
+>a.getCls().y : string
+>a.getCls() : Cls
+>a.getCls : () => Cls
+>a : A
+>getCls : () => Cls
+>y : string
+>toLowerCase : () => string
+
+=== tests/cases/compiler/a.ts ===
+
+export class A {}
+>A : A
+
+=== tests/cases/compiler/b.ts ===
+export class B {x: number;}
+>B : B
+>x : number
+
+=== tests/cases/compiler/c.d.ts ===
+declare module "C" {
+    class Cls {y: string; }
+>Cls : Cls
+>y : string
+}
+
+=== tests/cases/compiler/d.d.ts ===
+declare module "D" {
+    import {A} from "a";
+>A : typeof A
+
+    import {B} from "b";
+>B : typeof B
+
+    module "a" {
+        interface A {
+>A : A
+
+            getB(): B;
+>getB : () => B
+>B : B
+        }
+    }
+}
+
+=== tests/cases/compiler/e.ts ===
+/// <reference path="c.d.ts"/>
+import {A} from "./a";
+>A : typeof A
+
+import {Cls} from "C";
+>Cls : typeof Cls
+
+A.prototype.getCls = function () { return undefined; }
+>A.prototype.getCls = function () { return undefined; } : () => any
+>A.prototype.getCls : () => Cls
+>A.prototype : A
+>A : typeof A
+>prototype : A
+>getCls : () => Cls
+>function () { return undefined; } : () => any
+>undefined : undefined
+
+declare module "./a" {
+    interface A {
+>A : A
+
+        getCls(): Cls;
+>getCls : () => Cls
+>Cls : Cls
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationsImports4.js b/tests/baselines/reference/moduleAugmentationsImports4.js
new file mode 100644
index 0000000000..9b64016113
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports4.js
@@ -0,0 +1,90 @@
+//// [tests/cases/compiler/moduleAugmentationsImports4.ts] ////
+
+//// [a.ts]
+
+export class A {}
+
+//// [b.ts]
+export class B {x: number;}
+
+//// [c.d.ts]
+declare module "C" {
+    class Cls {y: string; }
+}
+
+//// [d.d.ts]
+declare module "D" {
+    import {A} from "a";
+    import {B} from "b";
+    module "a" {
+        interface A {
+            getB(): B;
+        }
+    }
+}
+
+//// [e.d.ts]
+/// <reference path="c.d.ts"/>
+declare module "E" {
+    import {A} from "a";
+    import {Cls} from "C";
+
+    module "a" {
+        interface A {
+            getCls(): Cls;
+        }
+    }
+}
+
+//// [main.ts]
+/// <reference path="d.d.ts"/>
+/// <reference path="e.d.ts"/>
+import {A} from "./a";
+import "D";
+import "E";
+
+let a: A;
+let b = a.getB().x.toFixed();
+let c = a.getCls().y.toLowerCase();
+
+//// [f.js]
+define("a", ["require", "exports"], function (require, exports) {
+    "use strict";
+    var A = (function () {
+        function A() {
+        }
+        return A;
+    }());
+    exports.A = A;
+});
+define("b", ["require", "exports"], function (require, exports) {
+    "use strict";
+    var B = (function () {
+        function B() {
+        }
+        return B;
+    }());
+    exports.B = B;
+});
+define("main", ["require", "exports", "D", "E"], function (require, exports) {
+    "use strict";
+    var a;
+    var b = a.getB().x.toFixed();
+    var c = a.getCls().y.toLowerCase();
+});
+
+
+//// [f.d.ts]
+/// <reference path="tests/cases/compiler/d.d.ts" />
+/// <reference path="tests/cases/compiler/e.d.ts" />
+declare module "a" {
+    export class A {
+    }
+}
+declare module "b" {
+    export class B {
+        x: number;
+    }
+}
+declare module "main" {
+}
diff --git a/tests/baselines/reference/moduleAugmentationsImports4.symbols b/tests/baselines/reference/moduleAugmentationsImports4.symbols
new file mode 100644
index 0000000000..8d203de851
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports4.symbols
@@ -0,0 +1,89 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="d.d.ts"/>
+/// <reference path="e.d.ts"/>
+import {A} from "./a";
+>A : Symbol(A, Decl(main.ts, 2, 8))
+
+import "D";
+import "E";
+
+let a: A;
+>a : Symbol(a, Decl(main.ts, 6, 3))
+>A : Symbol(A, Decl(main.ts, 2, 8))
+
+let b = a.getB().x.toFixed();
+>b : Symbol(b, Decl(main.ts, 7, 3))
+>a.getB().x.toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+>a.getB().x : Symbol(B.x, Decl(b.ts, 0, 16))
+>a.getB : Symbol(A.getB, Decl(d.d.ts, 4, 21))
+>a : Symbol(a, Decl(main.ts, 6, 3))
+>getB : Symbol(A.getB, Decl(d.d.ts, 4, 21))
+>x : Symbol(B.x, Decl(b.ts, 0, 16))
+>toFixed : Symbol(Number.toFixed, Decl(lib.d.ts, --, --))
+
+let c = a.getCls().y.toLowerCase();
+>c : Symbol(c, Decl(main.ts, 8, 3))
+>a.getCls().y.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>a.getCls().y : Symbol(Cls.y, Decl(c.d.ts, 1, 15))
+>a.getCls : Symbol(A.getCls, Decl(e.d.ts, 6, 21))
+>a : Symbol(a, Decl(main.ts, 6, 3))
+>getCls : Symbol(A.getCls, Decl(e.d.ts, 6, 21))
+>y : Symbol(Cls.y, Decl(c.d.ts, 1, 15))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+
+=== tests/cases/compiler/a.ts ===
+
+export class A {}
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.d.ts, 3, 16), Decl(e.d.ts, 5, 16))
+
+=== tests/cases/compiler/b.ts ===
+export class B {x: number;}
+>B : Symbol(B, Decl(b.ts, 0, 0))
+>x : Symbol(x, Decl(b.ts, 0, 16))
+
+=== tests/cases/compiler/c.d.ts ===
+declare module "C" {
+    class Cls {y: string; }
+>Cls : Symbol(Cls, Decl(c.d.ts, 0, 20))
+>y : Symbol(y, Decl(c.d.ts, 1, 15))
+}
+
+=== tests/cases/compiler/d.d.ts ===
+declare module "D" {
+    import {A} from "a";
+>A : Symbol(A, Decl(d.d.ts, 1, 12))
+
+    import {B} from "b";
+>B : Symbol(B, Decl(d.d.ts, 2, 12))
+
+    module "a" {
+        interface A {
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.d.ts, 3, 16), Decl(e.d.ts, 5, 16))
+
+            getB(): B;
+>getB : Symbol(getB, Decl(d.d.ts, 4, 21))
+>B : Symbol(B, Decl(d.d.ts, 2, 12))
+        }
+    }
+}
+
+=== tests/cases/compiler/e.d.ts ===
+/// <reference path="c.d.ts"/>
+declare module "E" {
+    import {A} from "a";
+>A : Symbol(A, Decl(e.d.ts, 2, 12))
+
+    import {Cls} from "C";
+>Cls : Symbol(Cls, Decl(e.d.ts, 3, 12))
+
+    module "a" {
+        interface A {
+>A : Symbol(A, Decl(a.ts, 0, 0), Decl(d.d.ts, 3, 16), Decl(e.d.ts, 5, 16))
+
+            getCls(): Cls;
+>getCls : Symbol(getCls, Decl(e.d.ts, 6, 21))
+>Cls : Symbol(Cls, Decl(e.d.ts, 3, 12))
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/moduleAugmentationsImports4.types b/tests/baselines/reference/moduleAugmentationsImports4.types
new file mode 100644
index 0000000000..53d570e14e
--- /dev/null
+++ b/tests/baselines/reference/moduleAugmentationsImports4.types
@@ -0,0 +1,93 @@
+=== tests/cases/compiler/main.ts ===
+/// <reference path="d.d.ts"/>
+/// <reference path="e.d.ts"/>
+import {A} from "./a";
+>A : typeof A
+
+import "D";
+import "E";
+
+let a: A;
+>a : A
+>A : A
+
+let b = a.getB().x.toFixed();
+>b : string
+>a.getB().x.toFixed() : string
+>a.getB().x.toFixed : (fractionDigits?: number) => string
+>a.getB().x : number
+>a.getB() : B
+>a.getB : () => B
+>a : A
+>getB : () => B
+>x : number
+>toFixed : (fractionDigits?: number) => string
+
+let c = a.getCls().y.toLowerCase();
+>c : string
+>a.getCls().y.toLowerCase() : string
+>a.getCls().y.toLowerCase : () => string
+>a.getCls().y : string
+>a.getCls() : Cls
+>a.getCls : () => Cls
+>a : A
+>getCls : () => Cls
+>y : string
+>toLowerCase : () => string
+
+=== tests/cases/compiler/a.ts ===
+
+export class A {}
+>A : A
+
+=== tests/cases/compiler/b.ts ===
+export class B {x: number;}
+>B : B
+>x : number
+
+=== tests/cases/compiler/c.d.ts ===
+declare module "C" {
+    class Cls {y: string; }
+>Cls : Cls
+>y : string
+}
+
+=== tests/cases/compiler/d.d.ts ===
+declare module "D" {
+    import {A} from "a";
+>A : typeof A
+
+    import {B} from "b";
+>B : typeof B
+
+    module "a" {
+        interface A {
+>A : A
+
+            getB(): B;
+>getB : () => B
+>B : B
+        }
+    }
+}
+
+=== tests/cases/compiler/e.d.ts ===
+/// <reference path="c.d.ts"/>
+declare module "E" {
+    import {A} from "a";
+>A : typeof A
+
+    import {Cls} from "C";
+>Cls : typeof Cls
+
+    module "a" {
+        interface A {
+>A : A
+
+            getCls(): Cls;
+>getCls : () => Cls
+>Cls : Cls
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/numericIndexerConstraint1.errors.txt b/tests/baselines/reference/numericIndexerConstraint1.errors.txt
index 42cf293fe6..0d4bb17002 100644
--- a/tests/baselines/reference/numericIndexerConstraint1.errors.txt
+++ b/tests/baselines/reference/numericIndexerConstraint1.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/compiler/numericIndexerConstraint1.ts(3,5): error TS2322: Type 'number' is not assignable to type 'Foo'.
-  Property 'foo' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/numericIndexerConstraint1.ts (1 errors) ====
@@ -8,5 +7,4 @@ tests/cases/compiler/numericIndexerConstraint1.ts(3,5): error TS2322: Type 'numb
     var result: Foo = x["one"]; // error
         ~~~~~~
 !!! error TS2322: Type 'number' is not assignable to type 'Foo'.
-!!! error TS2322:   Property 'foo' is missing in type 'Number'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/objectLiteralIndexerErrors.errors.txt b/tests/baselines/reference/objectLiteralIndexerErrors.errors.txt
index c35e49f02a..f825c41631 100644
--- a/tests/baselines/reference/objectLiteralIndexerErrors.errors.txt
+++ b/tests/baselines/reference/objectLiteralIndexerErrors.errors.txt
@@ -1,6 +1,7 @@
 tests/cases/compiler/objectLiteralIndexerErrors.ts(13,5): error TS2322: Type '{ [x: string]: A; [x: number]: A; 0: A; x: B; }' is not assignable to type '{ [s: string]: A; [n: number]: B; }'.
   Index signatures are incompatible.
     Type 'A' is not assignable to type 'B'.
+      Property 'y' is missing in type 'A'.
 
 
 ==== tests/cases/compiler/objectLiteralIndexerErrors.ts (1 errors) ====
@@ -21,4 +22,5 @@ tests/cases/compiler/objectLiteralIndexerErrors.ts(13,5): error TS2322: Type '{
 !!! error TS2322: Type '{ [x: string]: A; [x: number]: A; 0: A; x: B; }' is not assignable to type '{ [s: string]: A; [n: number]: B; }'.
 !!! error TS2322:   Index signatures are incompatible.
 !!! error TS2322:     Type 'A' is not assignable to type 'B'.
+!!! error TS2322:       Property 'y' is missing in type 'A'.
     o1 = { x: c, 0: a }; // string indexer is any, number indexer is A
\ No newline at end of file
diff --git a/tests/baselines/reference/parseClassDeclarationInStrictModeByDefaultInES6.errors.txt b/tests/baselines/reference/parseClassDeclarationInStrictModeByDefaultInES6.errors.txt
index e1b0bb3452..6f45030a65 100644
--- a/tests/baselines/reference/parseClassDeclarationInStrictModeByDefaultInES6.errors.txt
+++ b/tests/baselines/reference/parseClassDeclarationInStrictModeByDefaultInES6.errors.txt
@@ -2,7 +2,6 @@ tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeBy
 tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts(5,17): error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
 tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts(6,9): error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
 tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts(6,9): error TS2322: Type 'string' is not assignable to type 'IArguments'.
-  Property 'callee' is missing in type 'String'.
 
 
 ==== tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts (4 errors) ====
@@ -20,6 +19,5 @@ tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeBy
 !!! error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
             ~~~~~~~~~
 !!! error TS2322: Type 'string' is not assignable to type 'IArguments'.
-!!! error TS2322:   Property 'callee' is missing in type 'String'.
         }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserharness.errors.txt b/tests/baselines/reference/parserharness.errors.txt
index 66afa3d010..963ce12ddf 100644
--- a/tests/baselines/reference/parserharness.errors.txt
+++ b/tests/baselines/reference/parserharness.errors.txt
@@ -7,11 +7,11 @@ tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(25,17): er
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(41,12): error TS2304: Cannot find name 'ActiveXObject'.
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(43,19): error TS2304: Cannot find name 'require'.
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(44,14): error TS2304: Cannot find name 'require'.
-tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(341,13): error TS2304: Cannot find name 'errorHandlerStack'.
-tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(347,13): error TS2304: Cannot find name 'errorHandlerStack'.
-tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(351,17): error TS2304: Cannot find name 'errorHandlerStack'.
-tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(354,17): error TS2304: Cannot find name 'errorHandlerStack'.
-tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(354,35): error TS2304: Cannot find name 'errorHandlerStack'.
+tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(341,13): error TS2662: Cannot find name 'errorHandlerStack'. Did you mean the static member 'Runnable.errorHandlerStack'?
+tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(347,13): error TS2662: Cannot find name 'errorHandlerStack'. Did you mean the static member 'Runnable.errorHandlerStack'?
+tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(351,17): error TS2662: Cannot find name 'errorHandlerStack'. Did you mean the static member 'Runnable.errorHandlerStack'?
+tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(354,17): error TS2662: Cannot find name 'errorHandlerStack'. Did you mean the static member 'Runnable.errorHandlerStack'?
+tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(354,35): error TS2662: Cannot find name 'errorHandlerStack'. Did you mean the static member 'Runnable.errorHandlerStack'?
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(691,50): error TS2304: Cannot find name 'ITextWriter'.
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(716,47): error TS2503: Cannot find namespace 'TypeScript'.
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(721,62): error TS2304: Cannot find name 'ITextWriter'.
@@ -471,7 +471,7 @@ tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(2030,32):
             static pushGlobalErrorHandler(done: IDone) {
                 errorHandlerStack.push(function (e) {
                 ~~~~~~~~~~~~~~~~~
-!!! error TS2304: Cannot find name 'errorHandlerStack'.
+!!! error TS2662: Cannot find name 'errorHandlerStack'. Did you mean the static member 'Runnable.errorHandlerStack'?
                     done(e);
                 });
             }
@@ -479,20 +479,20 @@ tests/cases/conformance/parser/ecmascript5/RealWorld/parserharness.ts(2030,32):
             static popGlobalErrorHandler() {
                 errorHandlerStack.pop();
                 ~~~~~~~~~~~~~~~~~
-!!! error TS2304: Cannot find name 'errorHandlerStack'.
+!!! error TS2662: Cannot find name 'errorHandlerStack'. Did you mean the static member 'Runnable.errorHandlerStack'?
             }
     
             static handleError(e: Error) {
                 if (errorHandlerStack.length === 0) {
                     ~~~~~~~~~~~~~~~~~
-!!! error TS2304: Cannot find name 'errorHandlerStack'.
+!!! error TS2662: Cannot find name 'errorHandlerStack'. Did you mean the static member 'Runnable.errorHandlerStack'?
                     IO.printLine('Global error: ' + e);
                 } else {
                     errorHandlerStack[errorHandlerStack.length - 1](e);
                     ~~~~~~~~~~~~~~~~~
-!!! error TS2304: Cannot find name 'errorHandlerStack'.
+!!! error TS2662: Cannot find name 'errorHandlerStack'. Did you mean the static member 'Runnable.errorHandlerStack'?
                                       ~~~~~~~~~~~~~~~~~
-!!! error TS2304: Cannot find name 'errorHandlerStack'.
+!!! error TS2662: Cannot find name 'errorHandlerStack'. Did you mean the static member 'Runnable.errorHandlerStack'?
                 }
             }
         }
diff --git a/tests/baselines/reference/parserindenter.errors.txt b/tests/baselines/reference/parserindenter.errors.txt
index a332abab7b..8ccc922071 100644
--- a/tests/baselines/reference/parserindenter.errors.txt
+++ b/tests/baselines/reference/parserindenter.errors.txt
@@ -28,7 +28,7 @@ tests/cases/conformance/parser/ecmascript5/RealWorld/parserindenter.ts(152,63):
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserindenter.ts(153,30): error TS2304: Cannot find name 'List_TextEditInfo'.
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserindenter.ts(155,32): error TS2304: Cannot find name 'AuthorTokenKind'.
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserindenter.ts(182,79): error TS2503: Cannot find namespace 'Services'.
-tests/cases/conformance/parser/ecmascript5/RealWorld/parserindenter.ts(183,20): error TS2304: Cannot find name 'GetIndentSizeFromText'.
+tests/cases/conformance/parser/ecmascript5/RealWorld/parserindenter.ts(183,20): error TS2662: Cannot find name 'GetIndentSizeFromText'. Did you mean the static member 'Indenter.GetIndentSizeFromText'?
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserindenter.ts(186,67): error TS2503: Cannot find namespace 'Services'.
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserindenter.ts(207,50): error TS2304: Cannot find name 'TokenSpan'.
 tests/cases/conformance/parser/ecmascript5/RealWorld/parserindenter.ts(207,67): error TS2304: Cannot find name 'ParseNode'.
@@ -373,7 +373,7 @@ tests/cases/conformance/parser/ecmascript5/RealWorld/parserindenter.ts(736,38):
 !!! error TS2503: Cannot find namespace 'Services'.
                 return GetIndentSizeFromText(indentText, editorOptions, /*includeNonIndentChars:*/ false);
                        ~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2304: Cannot find name 'GetIndentSizeFromText'.
+!!! error TS2662: Cannot find name 'GetIndentSizeFromText'. Did you mean the static member 'Indenter.GetIndentSizeFromText'?
             }
     
             static GetIndentSizeFromText(text: string, editorOptions: Services.EditorOptions, includeNonIndentChars: boolean): number {
diff --git a/tests/baselines/reference/privacyGloImportParseErrors.errors.txt b/tests/baselines/reference/privacyGloImportParseErrors.errors.txt
index 236418a10a..05bb3559f1 100644
--- a/tests/baselines/reference/privacyGloImportParseErrors.errors.txt
+++ b/tests/baselines/reference/privacyGloImportParseErrors.errors.txt
@@ -1,3 +1,4 @@
+tests/cases/compiler/privacyGloImportParseErrors.ts(22,5): error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
 tests/cases/compiler/privacyGloImportParseErrors.ts(22,27): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 tests/cases/compiler/privacyGloImportParseErrors.ts(30,20): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 tests/cases/compiler/privacyGloImportParseErrors.ts(49,29): error TS4000: Import declaration 'm1_im2_private' is using private name 'm1_M2_private'.
@@ -13,12 +14,12 @@ tests/cases/compiler/privacyGloImportParseErrors.ts(125,45): error TS1147: Impor
 tests/cases/compiler/privacyGloImportParseErrors.ts(133,9): error TS1038: A 'declare' modifier cannot be used in an already ambient context.
 tests/cases/compiler/privacyGloImportParseErrors.ts(133,24): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 tests/cases/compiler/privacyGloImportParseErrors.ts(138,16): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
-tests/cases/compiler/privacyGloImportParseErrors.ts(141,12): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+tests/cases/compiler/privacyGloImportParseErrors.ts(141,12): error TS2664: Invalid module name in augmentation, module 'abc3' cannot be found.
 tests/cases/compiler/privacyGloImportParseErrors.ts(146,25): error TS1147: Import declarations in a namespace cannot reference a module.
 tests/cases/compiler/privacyGloImportParseErrors.ts(149,29): error TS1147: Import declarations in a namespace cannot reference a module.
 
 
-==== tests/cases/compiler/privacyGloImportParseErrors.ts (18 errors) ====
+==== tests/cases/compiler/privacyGloImportParseErrors.ts (19 errors) ====
     module m1 {
         export module m1_M1_public {
             export class c1 {
@@ -41,6 +42,8 @@ tests/cases/compiler/privacyGloImportParseErrors.ts(149,29): error TS1147: Impor
         }
     
         export declare module "m1_M3_public" {
+        ~~~~~~
+!!! error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
                               ~~~~~~~~~~~~~~
 !!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
             export function f1();
@@ -191,7 +194,7 @@ tests/cases/compiler/privacyGloImportParseErrors.ts(149,29): error TS1147: Impor
         }
         module "abc3" {
                ~~~~~~
-!!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+!!! error TS2664: Invalid module name in augmentation, module 'abc3' cannot be found.
         }
     }
     
diff --git a/tests/baselines/reference/privacyImportParseErrors.errors.txt b/tests/baselines/reference/privacyImportParseErrors.errors.txt
index 5bae45f405..1826ac7226 100644
--- a/tests/baselines/reference/privacyImportParseErrors.errors.txt
+++ b/tests/baselines/reference/privacyImportParseErrors.errors.txt
@@ -1,3 +1,4 @@
+tests/cases/compiler/privacyImportParseErrors.ts(22,5): error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
 tests/cases/compiler/privacyImportParseErrors.ts(22,27): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 tests/cases/compiler/privacyImportParseErrors.ts(30,20): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 tests/cases/compiler/privacyImportParseErrors.ts(59,37): error TS1147: Import declarations in a namespace cannot reference a module.
@@ -6,6 +7,7 @@ tests/cases/compiler/privacyImportParseErrors.ts(69,37): error TS1147: Import de
 tests/cases/compiler/privacyImportParseErrors.ts(69,37): error TS2307: Cannot find module 'm1_M4_private'.
 tests/cases/compiler/privacyImportParseErrors.ts(81,43): error TS1147: Import declarations in a namespace cannot reference a module.
 tests/cases/compiler/privacyImportParseErrors.ts(82,43): error TS1147: Import declarations in a namespace cannot reference a module.
+tests/cases/compiler/privacyImportParseErrors.ts(106,5): error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
 tests/cases/compiler/privacyImportParseErrors.ts(106,27): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 tests/cases/compiler/privacyImportParseErrors.ts(114,20): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 tests/cases/compiler/privacyImportParseErrors.ts(143,37): error TS1147: Import declarations in a namespace cannot reference a module.
@@ -14,31 +16,35 @@ tests/cases/compiler/privacyImportParseErrors.ts(153,37): error TS1147: Import d
 tests/cases/compiler/privacyImportParseErrors.ts(153,37): error TS2307: Cannot find module 'm2_M4_private'.
 tests/cases/compiler/privacyImportParseErrors.ts(166,43): error TS1147: Import declarations in a namespace cannot reference a module.
 tests/cases/compiler/privacyImportParseErrors.ts(167,43): error TS1147: Import declarations in a namespace cannot reference a module.
-tests/cases/compiler/privacyImportParseErrors.ts(180,23): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
-tests/cases/compiler/privacyImportParseErrors.ts(198,23): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+tests/cases/compiler/privacyImportParseErrors.ts(180,1): error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
+tests/cases/compiler/privacyImportParseErrors.ts(180,23): error TS2664: Invalid module name in augmentation, module 'glo_M2_public' cannot be found.
+tests/cases/compiler/privacyImportParseErrors.ts(198,1): error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
+tests/cases/compiler/privacyImportParseErrors.ts(198,23): error TS2664: Invalid module name in augmentation, module 'glo_M4_private' cannot be found.
 tests/cases/compiler/privacyImportParseErrors.ts(218,34): error TS2307: Cannot find module 'glo_M2_public'.
 tests/cases/compiler/privacyImportParseErrors.ts(238,34): error TS2307: Cannot find module 'glo_M4_private'.
 tests/cases/compiler/privacyImportParseErrors.ts(251,40): error TS2307: Cannot find module 'glo_M2_public'.
 tests/cases/compiler/privacyImportParseErrors.ts(252,40): error TS2307: Cannot find module 'glo_M4_private'.
-tests/cases/compiler/privacyImportParseErrors.ts(255,23): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+tests/cases/compiler/privacyImportParseErrors.ts(255,1): error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
+tests/cases/compiler/privacyImportParseErrors.ts(255,23): error TS2664: Invalid module name in augmentation, module 'use_glo_M1_public' cannot be found.
 tests/cases/compiler/privacyImportParseErrors.ts(258,45): error TS2304: Cannot find name 'use_glo_M1_public'.
 tests/cases/compiler/privacyImportParseErrors.ts(261,39): error TS2304: Cannot find name 'use_glo_M1_public'.
 tests/cases/compiler/privacyImportParseErrors.ts(264,40): error TS2307: Cannot find module 'glo_M2_public'.
 tests/cases/compiler/privacyImportParseErrors.ts(273,38): error TS1147: Import declarations in a namespace cannot reference a module.
 tests/cases/compiler/privacyImportParseErrors.ts(277,45): error TS1147: Import declarations in a namespace cannot reference a module.
-tests/cases/compiler/privacyImportParseErrors.ts(284,16): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+tests/cases/compiler/privacyImportParseErrors.ts(284,16): error TS2664: Invalid module name in augmentation, module 'use_glo_M3_private' cannot be found.
 tests/cases/compiler/privacyImportParseErrors.ts(287,46): error TS2304: Cannot find name 'use_glo_M3_private'.
 tests/cases/compiler/privacyImportParseErrors.ts(290,40): error TS2304: Cannot find name 'use_glo_M3_private'.
 tests/cases/compiler/privacyImportParseErrors.ts(293,41): error TS2307: Cannot find module 'glo_M4_private'.
 tests/cases/compiler/privacyImportParseErrors.ts(302,38): error TS1147: Import declarations in a namespace cannot reference a module.
 tests/cases/compiler/privacyImportParseErrors.ts(306,45): error TS1147: Import declarations in a namespace cannot reference a module.
-tests/cases/compiler/privacyImportParseErrors.ts(312,16): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+tests/cases/compiler/privacyImportParseErrors.ts(312,16): error TS2664: Invalid module name in augmentation, module 'anotherParseError' cannot be found.
 tests/cases/compiler/privacyImportParseErrors.ts(314,9): error TS1038: A 'declare' modifier cannot be used in an already ambient context.
 tests/cases/compiler/privacyImportParseErrors.ts(314,24): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 tests/cases/compiler/privacyImportParseErrors.ts(319,16): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 tests/cases/compiler/privacyImportParseErrors.ts(322,12): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+tests/cases/compiler/privacyImportParseErrors.ts(326,1): error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
 tests/cases/compiler/privacyImportParseErrors.ts(326,9): error TS1029: 'export' modifier must precede 'declare' modifier.
-tests/cases/compiler/privacyImportParseErrors.ts(326,23): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+tests/cases/compiler/privacyImportParseErrors.ts(326,23): error TS2664: Invalid module name in augmentation, module 'anotherParseError2' cannot be found.
 tests/cases/compiler/privacyImportParseErrors.ts(328,9): error TS1038: A 'declare' modifier cannot be used in an already ambient context.
 tests/cases/compiler/privacyImportParseErrors.ts(328,24): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
 tests/cases/compiler/privacyImportParseErrors.ts(333,16): error TS2435: Ambient modules cannot be nested in other modules or namespaces.
@@ -49,7 +55,7 @@ tests/cases/compiler/privacyImportParseErrors.ts(350,25): error TS1147: Import d
 tests/cases/compiler/privacyImportParseErrors.ts(353,29): error TS1147: Import declarations in a namespace cannot reference a module.
 
 
-==== tests/cases/compiler/privacyImportParseErrors.ts (49 errors) ====
+==== tests/cases/compiler/privacyImportParseErrors.ts (55 errors) ====
     export module m1 {
         export module m1_M1_public {
             export class c1 {
@@ -72,6 +78,8 @@ tests/cases/compiler/privacyImportParseErrors.ts(353,29): error TS1147: Import d
         }
     
         export declare module "m1_M3_public" {
+        ~~~~~~
+!!! error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
                               ~~~~~~~~~~~~~~
 !!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
             export function f1();
@@ -172,6 +180,8 @@ tests/cases/compiler/privacyImportParseErrors.ts(353,29): error TS1147: Import d
         }
     
         export declare module "m2_M3_public" {
+        ~~~~~~
+!!! error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
                               ~~~~~~~~~~~~~~
 !!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
             export function f1();
@@ -262,8 +272,10 @@ tests/cases/compiler/privacyImportParseErrors.ts(353,29): error TS1147: Import d
     }
     
     export declare module "glo_M2_public" {
+    ~~~~~~
+!!! error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
                           ~~~~~~~~~~~~~~~
-!!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+!!! error TS2664: Invalid module name in augmentation, module 'glo_M2_public' cannot be found.
         export function f1();
         export class c1 {
         }
@@ -282,8 +294,10 @@ tests/cases/compiler/privacyImportParseErrors.ts(353,29): error TS1147: Import d
     }
     
     export declare module "glo_M4_private" {
+    ~~~~~~
+!!! error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
                           ~~~~~~~~~~~~~~~~
-!!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+!!! error TS2664: Invalid module name in augmentation, module 'glo_M4_private' cannot be found.
         export function f1();
         export class c1 {
         }
@@ -349,8 +363,10 @@ tests/cases/compiler/privacyImportParseErrors.ts(353,29): error TS1147: Import d
     
     
     export declare module "use_glo_M1_public" {
+    ~~~~~~
+!!! error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
                           ~~~~~~~~~~~~~~~~~~~
-!!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+!!! error TS2664: Invalid module name in augmentation, module 'use_glo_M1_public' cannot be found.
         import use_glo_M1_public = glo_M1_public;
         export var use_glo_M1_public_v1_public: { new (): use_glo_M1_public.c1; };
         export var use_glo_M1_public_v2_public: use_glo_M1_public;
@@ -391,7 +407,7 @@ tests/cases/compiler/privacyImportParseErrors.ts(353,29): error TS1147: Import d
     
     declare module "use_glo_M3_private" {
                    ~~~~~~~~~~~~~~~~~~~~
-!!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+!!! error TS2664: Invalid module name in augmentation, module 'use_glo_M3_private' cannot be found.
         import use_glo_M3_private = glo_M3_private;
         export var use_glo_M3_private_v1_public: { new (): use_glo_M3_private.c1; };
         export var use_glo_M3_private_v2_public: use_glo_M3_private;
@@ -431,7 +447,7 @@ tests/cases/compiler/privacyImportParseErrors.ts(353,29): error TS1147: Import d
     
     declare module "anotherParseError" {
                    ~~~~~~~~~~~~~~~~~~~
-!!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+!!! error TS2664: Invalid module name in augmentation, module 'anotherParseError' cannot be found.
         module m2 {
             declare module "abc" {
             ~~~~~~~
@@ -454,10 +470,12 @@ tests/cases/compiler/privacyImportParseErrors.ts(353,29): error TS1147: Import d
     }
     
     declare export module "anotherParseError2" {
+    ~~~~~~~
+!!! error TS2668: 'export' modifier cannot be applied to ambient modules and module augmentations since they are always visible.
             ~~~~~~
 !!! error TS1029: 'export' modifier must precede 'declare' modifier.
                           ~~~~~~~~~~~~~~~~~~~~
-!!! error TS2435: Ambient modules cannot be nested in other modules or namespaces.
+!!! error TS2664: Invalid module name in augmentation, module 'anotherParseError2' cannot be found.
         module m2 {
             declare module "abc" {
             ~~~~~~~
diff --git a/tests/baselines/reference/promiseChaining1.errors.txt b/tests/baselines/reference/promiseChaining1.errors.txt
index bd3e52fcc1..7396d03059 100644
--- a/tests/baselines/reference/promiseChaining1.errors.txt
+++ b/tests/baselines/reference/promiseChaining1.errors.txt
@@ -1,6 +1,5 @@
 tests/cases/compiler/promiseChaining1.ts(7,50): error TS2345: Argument of type '(x: S) => string' is not assignable to parameter of type '(x: S) => Function'.
   Type 'string' is not assignable to type 'Function'.
-    Property 'apply' is missing in type 'String'.
 
 
 ==== tests/cases/compiler/promiseChaining1.ts (1 errors) ====
@@ -14,7 +13,6 @@ tests/cases/compiler/promiseChaining1.ts(7,50): error TS2345: Argument of type '
                                                      ~~~~~~~~~~
 !!! error TS2345: Argument of type '(x: S) => string' is not assignable to parameter of type '(x: S) => Function'.
 !!! error TS2345:   Type 'string' is not assignable to type 'Function'.
-!!! error TS2345:     Property 'apply' is missing in type 'String'.
             return new Chain2(result);
         }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/promiseChaining2.errors.txt b/tests/baselines/reference/promiseChaining2.errors.txt
index f12baebd4d..a31c4335da 100644
--- a/tests/baselines/reference/promiseChaining2.errors.txt
+++ b/tests/baselines/reference/promiseChaining2.errors.txt
@@ -1,6 +1,5 @@
 tests/cases/compiler/promiseChaining2.ts(7,45): error TS2345: Argument of type '(x: S) => string' is not assignable to parameter of type '(x: S) => Function'.
   Type 'string' is not assignable to type 'Function'.
-    Property 'apply' is missing in type 'String'.
 
 
 ==== tests/cases/compiler/promiseChaining2.ts (1 errors) ====
@@ -14,7 +13,6 @@ tests/cases/compiler/promiseChaining2.ts(7,45): error TS2345: Argument of type '
                                                 ~~~~~~~~~~
 !!! error TS2345: Argument of type '(x: S) => string' is not assignable to parameter of type '(x: S) => Function'.
 !!! error TS2345:   Type 'string' is not assignable to type 'Function'.
-!!! error TS2345:     Property 'apply' is missing in type 'String'.
             return new Chain2(result);
         }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/promisePermutations.errors.txt b/tests/baselines/reference/promisePermutations.errors.txt
index a74938f5dd..4edfff05a5 100644
--- a/tests/baselines/reference/promisePermutations.errors.txt
+++ b/tests/baselines/reference/promisePermutations.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/promisePermutations.ts(74,70): error TS2345: Argument of type '(x: number) => IPromise<number>' is not assignable to parameter of type '(value: IPromise<number>) => IPromise<number>'.
   Types of parameters 'x' and 'value' are incompatible.
     Type 'number' is not assignable to type 'IPromise<number>'.
-      Property 'then' is missing in type 'Number'.
 tests/cases/compiler/promisePermutations.ts(79,19): error TS2345: Argument of type '(x: number, y?: string) => IPromise<string>' is not assignable to parameter of type '(value: string) => IPromise<string>'.
   Types of parameters 'x' and 'value' are incompatible.
     Type 'number' is not assignable to type 'string'.
@@ -157,7 +156,6 @@ tests/cases/compiler/promisePermutations.ts(160,21): error TS2345: Argument of t
 !!! error TS2345: Argument of type '(x: number) => IPromise<number>' is not assignable to parameter of type '(value: IPromise<number>) => IPromise<number>'.
 !!! error TS2345:   Types of parameters 'x' and 'value' are incompatible.
 !!! error TS2345:     Type 'number' is not assignable to type 'IPromise<number>'.
-!!! error TS2345:       Property 'then' is missing in type 'Number'.
     
     var r4: IPromise<string>;
     var sIPromise: (x: any) => IPromise<string>;
diff --git a/tests/baselines/reference/promisePermutations2.errors.txt b/tests/baselines/reference/promisePermutations2.errors.txt
index 8afceeae0f..dda9a08b38 100644
--- a/tests/baselines/reference/promisePermutations2.errors.txt
+++ b/tests/baselines/reference/promisePermutations2.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/promisePermutations2.ts(73,70): error TS2345: Argument of type '(x: number) => IPromise<number>' is not assignable to parameter of type '(value: IPromise<number>) => IPromise<number>'.
   Types of parameters 'x' and 'value' are incompatible.
     Type 'number' is not assignable to type 'IPromise<number>'.
-      Property 'then' is missing in type 'Number'.
 tests/cases/compiler/promisePermutations2.ts(78,19): error TS2345: Argument of type '(x: number, y?: string) => IPromise<string>' is not assignable to parameter of type '(value: string) => IPromise<string>'.
   Types of parameters 'x' and 'value' are incompatible.
     Type 'number' is not assignable to type 'string'.
@@ -156,7 +155,6 @@ tests/cases/compiler/promisePermutations2.ts(159,21): error TS2345: Argument of
 !!! error TS2345: Argument of type '(x: number) => IPromise<number>' is not assignable to parameter of type '(value: IPromise<number>) => IPromise<number>'.
 !!! error TS2345:   Types of parameters 'x' and 'value' are incompatible.
 !!! error TS2345:     Type 'number' is not assignable to type 'IPromise<number>'.
-!!! error TS2345:       Property 'then' is missing in type 'Number'.
     
     var r4: IPromise<string>;
     var sIPromise: (x: any) => IPromise<string>;
diff --git a/tests/baselines/reference/promisePermutations3.errors.txt b/tests/baselines/reference/promisePermutations3.errors.txt
index b17021a02b..c6c2bca62a 100644
--- a/tests/baselines/reference/promisePermutations3.errors.txt
+++ b/tests/baselines/reference/promisePermutations3.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/promisePermutations3.ts(68,69): error TS2345: Argument of type '(x: number) => IPromise<number>' is not assignable to parameter of type '(value: IPromise<number>) => IPromise<number>'.
   Types of parameters 'x' and 'value' are incompatible.
     Type 'number' is not assignable to type 'IPromise<number>'.
-      Property 'then' is missing in type 'Number'.
 tests/cases/compiler/promisePermutations3.ts(73,70): error TS2345: Argument of type '(x: number) => IPromise<number>' is not assignable to parameter of type '(value: IPromise<number>) => IPromise<number>'.
   Types of parameters 'x' and 'value' are incompatible.
     Type 'number' is not assignable to type 'IPromise<number>'.
@@ -159,7 +158,6 @@ tests/cases/compiler/promisePermutations3.ts(165,21): error TS2345: Argument of
 !!! error TS2345: Argument of type '(x: number) => IPromise<number>' is not assignable to parameter of type '(value: IPromise<number>) => IPromise<number>'.
 !!! error TS2345:   Types of parameters 'x' and 'value' are incompatible.
 !!! error TS2345:     Type 'number' is not assignable to type 'IPromise<number>'.
-!!! error TS2345:       Property 'then' is missing in type 'Number'.
     var s3: Promise<number>;
     var s3a = s3.then(testFunction3, testFunction3, testFunction3);
     var s3b = s3.then(testFunction3P, testFunction3P, testFunction3P);
diff --git a/tests/baselines/reference/qualify.errors.txt b/tests/baselines/reference/qualify.errors.txt
index f38fc93ccd..c3447664c9 100644
--- a/tests/baselines/reference/qualify.errors.txt
+++ b/tests/baselines/reference/qualify.errors.txt
@@ -1,7 +1,5 @@
 tests/cases/compiler/qualify.ts(21,13): error TS2322: Type 'number' is not assignable to type 'I'.
-  Property 'p' is missing in type 'Number'.
 tests/cases/compiler/qualify.ts(30,13): error TS2322: Type 'number' is not assignable to type 'I2'.
-  Property 'q' is missing in type 'Number'.
 tests/cases/compiler/qualify.ts(45,13): error TS2322: Type 'I4' is not assignable to type 'I3'.
   Property 'zeep' is missing in type 'I4'.
 tests/cases/compiler/qualify.ts(46,13): error TS2322: Type 'I4' is not assignable to type 'I3[]'.
@@ -40,7 +38,6 @@ tests/cases/compiler/qualify.ts(58,5): error TS2322: Type 'I' is not assignable
             var z:I=3;
                 ~
 !!! error TS2322: Type 'number' is not assignable to type 'I'.
-!!! error TS2322:   Property 'p' is missing in type 'Number'.
             export interface I2 {
                 q;
             }
@@ -52,7 +49,6 @@ tests/cases/compiler/qualify.ts(58,5): error TS2322: Type 'I' is not assignable
             var z:T.U.I2=3;
                 ~
 !!! error TS2322: Type 'number' is not assignable to type 'I2'.
-!!! error TS2322:   Property 'q' is missing in type 'Number'.
         }
     }
     
diff --git a/tests/baselines/reference/recursiveClassReferenceTest.errors.txt b/tests/baselines/reference/recursiveClassReferenceTest.errors.txt
index 088d7222f4..4a1a6f1782 100644
--- a/tests/baselines/reference/recursiveClassReferenceTest.errors.txt
+++ b/tests/baselines/reference/recursiveClassReferenceTest.errors.txt
@@ -1,6 +1,6 @@
 tests/cases/compiler/recursiveClassReferenceTest.ts(16,19): error TS2304: Cannot find name 'Element'.
-tests/cases/compiler/recursiveClassReferenceTest.ts(56,11): error TS2304: Cannot find name 'domNode'.
-tests/cases/compiler/recursiveClassReferenceTest.ts(88,36): error TS2304: Cannot find name 'mode'.
+tests/cases/compiler/recursiveClassReferenceTest.ts(56,11): error TS2663: Cannot find name 'domNode'. Did you mean the instance member 'this.domNode'?
+tests/cases/compiler/recursiveClassReferenceTest.ts(88,36): error TS2663: Cannot find name 'mode'. Did you mean the instance member 'this.mode'?
 tests/cases/compiler/recursiveClassReferenceTest.ts(95,21): error TS2345: Argument of type 'Window' is not assignable to parameter of type 'IMode'.
   Property 'getInitialState' is missing in type 'Window'.
 
@@ -65,7 +65,7 @@ tests/cases/compiler/recursiveClassReferenceTest.ts(95,21): error TS2345: Argume
     		public getDomNode() {
     			return domNode;
     			       ~~~~~~~
-!!! error TS2304: Cannot find name 'domNode'.
+!!! error TS2663: Cannot find name 'domNode'. Did you mean the instance member 'this.domNode'?
     		}
     		
     		public destroy() {
@@ -99,7 +99,7 @@ tests/cases/compiler/recursiveClassReferenceTest.ts(95,21): error TS2345: Argume
     		
     		public getMode(): IMode { return mode; }
     		                                 ~~~~
-!!! error TS2304: Cannot find name 'mode'.
+!!! error TS2663: Cannot find name 'mode'. Did you mean the instance member 'this.mode'?
     	}
     	
     	export class Mode extends AbstractMode {
diff --git a/tests/baselines/reference/restArgAssignmentCompat.errors.txt b/tests/baselines/reference/restArgAssignmentCompat.errors.txt
index 2ea0739509..c17d28cb28 100644
--- a/tests/baselines/reference/restArgAssignmentCompat.errors.txt
+++ b/tests/baselines/reference/restArgAssignmentCompat.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/compiler/restArgAssignmentCompat.ts(7,1): error TS2322: Type '(...x: number[]) => void' is not assignable to type '(x: number[], y: string) => void'.
   Types of parameters 'x' and 'x' are incompatible.
     Type 'number' is not assignable to type 'number[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/restArgAssignmentCompat.ts (1 errors) ====
@@ -16,6 +15,5 @@ tests/cases/compiler/restArgAssignmentCompat.ts(7,1): error TS2322: Type '(...x:
 !!! error TS2322: Type '(...x: number[]) => void' is not assignable to type '(x: number[], y: string) => void'.
 !!! error TS2322:   Types of parameters 'x' and 'x' are incompatible.
 !!! error TS2322:     Type 'number' is not assignable to type 'number[]'.
-!!! error TS2322:       Property 'length' is missing in type 'Number'.
     n([4], 'foo');
     
\ No newline at end of file
diff --git a/tests/baselines/reference/returnInConstructor1.errors.txt b/tests/baselines/reference/returnInConstructor1.errors.txt
index dbe3b9e5ee..30f629f9f8 100644
--- a/tests/baselines/reference/returnInConstructor1.errors.txt
+++ b/tests/baselines/reference/returnInConstructor1.errors.txt
@@ -1,8 +1,6 @@
 tests/cases/compiler/returnInConstructor1.ts(11,16): error TS2322: Type 'number' is not assignable to type 'B'.
-  Property 'foo' is missing in type 'Number'.
 tests/cases/compiler/returnInConstructor1.ts(11,16): error TS2409: Return type of constructor signature must be assignable to the instance type of the class
 tests/cases/compiler/returnInConstructor1.ts(25,16): error TS2322: Type 'string' is not assignable to type 'D'.
-  Property 'foo' is missing in type 'String'.
 tests/cases/compiler/returnInConstructor1.ts(25,16): error TS2409: Return type of constructor signature must be assignable to the instance type of the class
 tests/cases/compiler/returnInConstructor1.ts(39,16): error TS2322: Type '{ foo: number; }' is not assignable to type 'F'.
   Types of property 'foo' are incompatible.
@@ -28,7 +26,6 @@ tests/cases/compiler/returnInConstructor1.ts(55,16): error TS2409: Return type o
             return 1; // error
                    ~
 !!! error TS2322: Type 'number' is not assignable to type 'B'.
-!!! error TS2322:   Property 'foo' is missing in type 'Number'.
                    ~
 !!! error TS2409: Return type of constructor signature must be assignable to the instance type of the class
         }
@@ -47,7 +44,6 @@ tests/cases/compiler/returnInConstructor1.ts(55,16): error TS2409: Return type o
             return "test"; // error
                    ~~~~~~
 !!! error TS2322: Type 'string' is not assignable to type 'D'.
-!!! error TS2322:   Property 'foo' is missing in type 'String'.
                    ~~~~~~
 !!! error TS2409: Return type of constructor signature must be assignable to the instance type of the class
         }
diff --git a/tests/baselines/reference/scannertest1.errors.txt b/tests/baselines/reference/scannertest1.errors.txt
index 14a19b2885..3831dbe398 100644
--- a/tests/baselines/reference/scannertest1.errors.txt
+++ b/tests/baselines/reference/scannertest1.errors.txt
@@ -1,14 +1,14 @@
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(1,1): error TS6053: File 'tests/cases/conformance/scanner/ecmascript5/References.ts' not found.
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(5,21): error TS2304: Cannot find name 'CharacterCodes'.
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(5,47): error TS2304: Cannot find name 'CharacterCodes'.
-tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(9,16): error TS2304: Cannot find name 'isDecimalDigit'.
+tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(9,16): error TS2662: Cannot find name 'isDecimalDigit'. Did you mean the static member 'CharacterInfo.isDecimalDigit'?
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(10,22): error TS2304: Cannot find name 'CharacterCodes'.
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(10,47): error TS2304: Cannot find name 'CharacterCodes'.
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(11,22): error TS2304: Cannot find name 'CharacterCodes'.
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(11,47): error TS2304: Cannot find name 'CharacterCodes'.
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(15,9): error TS2304: Cannot find name 'Debug'.
-tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(15,22): error TS2304: Cannot find name 'isHexDigit'.
-tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(16,16): error TS2304: Cannot find name 'isDecimalDigit'.
+tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(15,22): error TS2662: Cannot find name 'isHexDigit'. Did you mean the static member 'CharacterInfo.isHexDigit'?
+tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(16,16): error TS2662: Cannot find name 'isDecimalDigit'. Did you mean the static member 'CharacterInfo.isDecimalDigit'?
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(17,20): error TS2304: Cannot find name 'CharacterCodes'.
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(18,21): error TS2304: Cannot find name 'CharacterCodes'.
 tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(18,46): error TS2304: Cannot find name 'CharacterCodes'.
@@ -33,7 +33,7 @@ tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(20,23): error TS2304
         public static isHexDigit(c: number): boolean {
             return isDecimalDigit(c) ||
                    ~~~~~~~~~~~~~~
-!!! error TS2304: Cannot find name 'isDecimalDigit'.
+!!! error TS2662: Cannot find name 'isDecimalDigit'. Did you mean the static member 'CharacterInfo.isDecimalDigit'?
                    (c >= CharacterCodes.A && c <= CharacterCodes.F) ||
                          ~~~~~~~~~~~~~~
 !!! error TS2304: Cannot find name 'CharacterCodes'.
@@ -51,10 +51,10 @@ tests/cases/conformance/scanner/ecmascript5/scannertest1.ts(20,23): error TS2304
             ~~~~~
 !!! error TS2304: Cannot find name 'Debug'.
                          ~~~~~~~~~~
-!!! error TS2304: Cannot find name 'isHexDigit'.
+!!! error TS2662: Cannot find name 'isHexDigit'. Did you mean the static member 'CharacterInfo.isHexDigit'?
             return isDecimalDigit(c)
                    ~~~~~~~~~~~~~~
-!!! error TS2304: Cannot find name 'isDecimalDigit'.
+!!! error TS2662: Cannot find name 'isDecimalDigit'. Did you mean the static member 'CharacterInfo.isDecimalDigit'?
                 ? (c - CharacterCodes._0)
                        ~~~~~~~~~~~~~~
 !!! error TS2304: Cannot find name 'CharacterCodes'.
diff --git a/tests/baselines/reference/scopeCheckExtendedClassInsidePublicMethod2.errors.txt b/tests/baselines/reference/scopeCheckExtendedClassInsidePublicMethod2.errors.txt
index c59171bdf0..378e20f19b 100644
--- a/tests/baselines/reference/scopeCheckExtendedClassInsidePublicMethod2.errors.txt
+++ b/tests/baselines/reference/scopeCheckExtendedClassInsidePublicMethod2.errors.txt
@@ -1,5 +1,5 @@
-tests/cases/compiler/scopeCheckExtendedClassInsidePublicMethod2.ts(4,7): error TS2304: Cannot find name 'v'.
-tests/cases/compiler/scopeCheckExtendedClassInsidePublicMethod2.ts(6,7): error TS2304: Cannot find name 's'.
+tests/cases/compiler/scopeCheckExtendedClassInsidePublicMethod2.ts(4,7): error TS2663: Cannot find name 'v'. Did you mean the instance member 'this.v'?
+tests/cases/compiler/scopeCheckExtendedClassInsidePublicMethod2.ts(6,7): error TS2662: Cannot find name 's'. Did you mean the static member 'D.s'?
 
 
 ==== tests/cases/compiler/scopeCheckExtendedClassInsidePublicMethod2.ts (2 errors) ====
@@ -8,10 +8,10 @@ tests/cases/compiler/scopeCheckExtendedClassInsidePublicMethod2.ts(6,7): error T
        public c() {
           v = 1;
           ~
-!!! error TS2304: Cannot find name 'v'.
+!!! error TS2663: Cannot find name 'v'. Did you mean the instance member 'this.v'?
           this.p = 1;
           s = 1;
           ~
-!!! error TS2304: Cannot find name 's'.
+!!! error TS2662: Cannot find name 's'. Did you mean the static member 'D.s'?
        }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/scopeCheckExtendedClassInsideStaticMethod1.errors.txt b/tests/baselines/reference/scopeCheckExtendedClassInsideStaticMethod1.errors.txt
index a6ecd48827..dd3e5ef446 100644
--- a/tests/baselines/reference/scopeCheckExtendedClassInsideStaticMethod1.errors.txt
+++ b/tests/baselines/reference/scopeCheckExtendedClassInsideStaticMethod1.errors.txt
@@ -1,6 +1,6 @@
 tests/cases/compiler/scopeCheckExtendedClassInsideStaticMethod1.ts(4,7): error TS2304: Cannot find name 'v'.
 tests/cases/compiler/scopeCheckExtendedClassInsideStaticMethod1.ts(5,12): error TS2339: Property 'p' does not exist on type 'typeof D'.
-tests/cases/compiler/scopeCheckExtendedClassInsideStaticMethod1.ts(6,7): error TS2304: Cannot find name 's'.
+tests/cases/compiler/scopeCheckExtendedClassInsideStaticMethod1.ts(6,7): error TS2662: Cannot find name 's'. Did you mean the static member 'D.s'?
 
 
 ==== tests/cases/compiler/scopeCheckExtendedClassInsideStaticMethod1.ts (3 errors) ====
@@ -15,6 +15,6 @@ tests/cases/compiler/scopeCheckExtendedClassInsideStaticMethod1.ts(6,7): error T
 !!! error TS2339: Property 'p' does not exist on type 'typeof D'.
           s = 1;
           ~
-!!! error TS2304: Cannot find name 's'.
+!!! error TS2662: Cannot find name 's'. Did you mean the static member 'D.s'?
        }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/scopeCheckInsidePublicMethod1.errors.txt b/tests/baselines/reference/scopeCheckInsidePublicMethod1.errors.txt
index 5c9473a787..ec93fea736 100644
--- a/tests/baselines/reference/scopeCheckInsidePublicMethod1.errors.txt
+++ b/tests/baselines/reference/scopeCheckInsidePublicMethod1.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/scopeCheckInsidePublicMethod1.ts(4,7): error TS2304: Cannot find name 's'.
+tests/cases/compiler/scopeCheckInsidePublicMethod1.ts(4,7): error TS2662: Cannot find name 's'. Did you mean the static member 'C.s'?
 
 
 ==== tests/cases/compiler/scopeCheckInsidePublicMethod1.ts (1 errors) ====
@@ -7,6 +7,6 @@ tests/cases/compiler/scopeCheckInsidePublicMethod1.ts(4,7): error TS2304: Cannot
        public a() {
           s = 1; // ERR
           ~
-!!! error TS2304: Cannot find name 's'.
+!!! error TS2662: Cannot find name 's'. Did you mean the static member 'C.s'?
        }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/staticClassMemberError.errors.txt b/tests/baselines/reference/staticClassMemberError.errors.txt
index 9483e3387b..43a2cd6934 100644
--- a/tests/baselines/reference/staticClassMemberError.errors.txt
+++ b/tests/baselines/reference/staticClassMemberError.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/staticClassMemberError.ts(4,3): error TS2304: Cannot find name 's'.
+tests/cases/compiler/staticClassMemberError.ts(4,3): error TS2662: Cannot find name 's'. Did you mean the static member 'C.s'?
 tests/cases/compiler/staticClassMemberError.ts(9,10): error TS2300: Duplicate identifier 'Foo'.
 tests/cases/compiler/staticClassMemberError.ts(9,10): error TS2391: Function implementation is missing or not immediately following the declaration.
 tests/cases/compiler/staticClassMemberError.ts(10,7): error TS2300: Duplicate identifier 'Foo'.
@@ -10,7 +10,7 @@ tests/cases/compiler/staticClassMemberError.ts(10,7): error TS2300: Duplicate id
     	public a() {
     		s = 1;
     		~
-!!! error TS2304: Cannot find name 's'.
+!!! error TS2662: Cannot find name 's'. Did you mean the static member 'C.s'?
     	}
     }
     
diff --git a/tests/baselines/reference/staticVisibility.errors.txt b/tests/baselines/reference/staticVisibility.errors.txt
index dccad4a2e2..a92cb7f88c 100644
--- a/tests/baselines/reference/staticVisibility.errors.txt
+++ b/tests/baselines/reference/staticVisibility.errors.txt
@@ -1,5 +1,5 @@
-tests/cases/compiler/staticVisibility.ts(10,9): error TS2304: Cannot find name 's'.
-tests/cases/compiler/staticVisibility.ts(13,9): error TS2304: Cannot find name 'b'.
+tests/cases/compiler/staticVisibility.ts(10,9): error TS2662: Cannot find name 's'. Did you mean the static member 'C1.s'?
+tests/cases/compiler/staticVisibility.ts(13,9): error TS2662: Cannot find name 'b'. Did you mean the static member 'C1.b'?
 tests/cases/compiler/staticVisibility.ts(18,9): error TS2304: Cannot find name 'v'.
 tests/cases/compiler/staticVisibility.ts(19,14): error TS2339: Property 'p' does not exist on type 'typeof C1'.
 tests/cases/compiler/staticVisibility.ts(31,12): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
@@ -19,12 +19,12 @@ tests/cases/compiler/staticVisibility.ts(33,29): error TS2304: Cannot find name
     
             s = 1; // should be error
             ~
-!!! error TS2304: Cannot find name 's'.
+!!! error TS2662: Cannot find name 's'. Did you mean the static member 'C1.s'?
             C1.s = 1; // should be ok
     
             b(); // should be error
             ~
-!!! error TS2304: Cannot find name 'b'.
+!!! error TS2662: Cannot find name 'b'. Did you mean the static member 'C1.b'?
             C1.b(); // should be ok
         }
     
diff --git a/tests/baselines/reference/subtypingWithNumericIndexer4.errors.txt b/tests/baselines/reference/subtypingWithNumericIndexer4.errors.txt
index 5dd39e0ad6..3f6de942d2 100644
--- a/tests/baselines/reference/subtypingWithNumericIndexer4.errors.txt
+++ b/tests/baselines/reference/subtypingWithNumericIndexer4.errors.txt
@@ -1,11 +1,9 @@
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithNumericIndexer4.ts(11,7): error TS2415: Class 'B' incorrectly extends base class 'A'.
   Index signatures are incompatible.
     Type 'string' is not assignable to type 'Derived'.
-      Property 'bar' is missing in type 'String'.
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithNumericIndexer4.ts(20,11): error TS2415: Class 'B' incorrectly extends base class 'A<Base>'.
   Index signatures are incompatible.
     Type 'string' is not assignable to type 'Base'.
-      Property 'foo' is missing in type 'String'.
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithNumericIndexer4.ts(20,23): error TS2344: Type 'Base' does not satisfy the constraint 'Derived'.
   Property 'bar' is missing in type 'Base'.
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithNumericIndexer4.ts(24,11): error TS2415: Class 'B3<T>' incorrectly extends base class 'A<T>'.
@@ -29,7 +27,6 @@ tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingW
 !!! error TS2415: Class 'B' incorrectly extends base class 'A'.
 !!! error TS2415:   Index signatures are incompatible.
 !!! error TS2415:     Type 'string' is not assignable to type 'Derived'.
-!!! error TS2415:       Property 'bar' is missing in type 'String'.
         [x: number]: string; // error
     }
     
@@ -43,7 +40,6 @@ tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingW
 !!! error TS2415: Class 'B' incorrectly extends base class 'A<Base>'.
 !!! error TS2415:   Index signatures are incompatible.
 !!! error TS2415:     Type 'string' is not assignable to type 'Base'.
-!!! error TS2415:       Property 'foo' is missing in type 'String'.
                           ~~~~
 !!! error TS2344: Type 'Base' does not satisfy the constraint 'Derived'.
 !!! error TS2344:   Property 'bar' is missing in type 'Base'.
diff --git a/tests/baselines/reference/subtypingWithObjectMembers.errors.txt b/tests/baselines/reference/subtypingWithObjectMembers.errors.txt
index e292c0867a..a5d4152b45 100644
--- a/tests/baselines/reference/subtypingWithObjectMembers.errors.txt
+++ b/tests/baselines/reference/subtypingWithObjectMembers.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithObjectMembers.ts(12,7): error TS2415: Class 'B' incorrectly extends base class 'A'.
   Types of property 'bar' are incompatible.
     Type 'string' is not assignable to type 'Base'.
-      Property 'foo' is missing in type 'String'.
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithObjectMembers.ts(22,7): error TS2415: Class 'B2' incorrectly extends base class 'A2'.
   Types of property '2.0' are incompatible.
     Type 'string' is not assignable to type 'Base'.
@@ -36,7 +35,6 @@ tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingW
 !!! error TS2415: Class 'B' incorrectly extends base class 'A'.
 !!! error TS2415:   Types of property 'bar' are incompatible.
 !!! error TS2415:     Type 'string' is not assignable to type 'Base'.
-!!! error TS2415:       Property 'foo' is missing in type 'String'.
         foo: Derived; // ok
         bar: string; // error
     }
diff --git a/tests/baselines/reference/subtypingWithObjectMembers2.errors.txt b/tests/baselines/reference/subtypingWithObjectMembers2.errors.txt
index 3d46a6e5dc..cdcc54c5ee 100644
--- a/tests/baselines/reference/subtypingWithObjectMembers2.errors.txt
+++ b/tests/baselines/reference/subtypingWithObjectMembers2.errors.txt
@@ -1,7 +1,6 @@
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithObjectMembers2.ts(17,15): error TS2430: Interface 'B' incorrectly extends interface 'A'.
   Types of property 'bar' are incompatible.
     Type 'string' is not assignable to type 'Base'.
-      Property 'foo' is missing in type 'String'.
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithObjectMembers2.ts(27,15): error TS2430: Interface 'B2' incorrectly extends interface 'A2'.
   Types of property '2.0' are incompatible.
     Type 'string' is not assignable to type 'Base'.
@@ -41,7 +40,6 @@ tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingW
 !!! error TS2430: Interface 'B' incorrectly extends interface 'A'.
 !!! error TS2430:   Types of property 'bar' are incompatible.
 !!! error TS2430:     Type 'string' is not assignable to type 'Base'.
-!!! error TS2430:       Property 'foo' is missing in type 'String'.
             foo: Derived; // ok
             bar: string; // error
         }
diff --git a/tests/baselines/reference/subtypingWithStringIndexer4.errors.txt b/tests/baselines/reference/subtypingWithStringIndexer4.errors.txt
index 4aa889444e..8d4328cdd2 100644
--- a/tests/baselines/reference/subtypingWithStringIndexer4.errors.txt
+++ b/tests/baselines/reference/subtypingWithStringIndexer4.errors.txt
@@ -1,11 +1,9 @@
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithStringIndexer4.ts(11,7): error TS2415: Class 'B' incorrectly extends base class 'A'.
   Index signatures are incompatible.
     Type 'string' is not assignable to type 'Derived'.
-      Property 'bar' is missing in type 'String'.
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithStringIndexer4.ts(20,11): error TS2415: Class 'B' incorrectly extends base class 'A<Base>'.
   Index signatures are incompatible.
     Type 'string' is not assignable to type 'Base'.
-      Property 'foo' is missing in type 'String'.
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithStringIndexer4.ts(20,23): error TS2344: Type 'Base' does not satisfy the constraint 'Derived'.
   Property 'bar' is missing in type 'Base'.
 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithStringIndexer4.ts(24,11): error TS2415: Class 'B3<T>' incorrectly extends base class 'A<T>'.
@@ -29,7 +27,6 @@ tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingW
 !!! error TS2415: Class 'B' incorrectly extends base class 'A'.
 !!! error TS2415:   Index signatures are incompatible.
 !!! error TS2415:     Type 'string' is not assignable to type 'Derived'.
-!!! error TS2415:       Property 'bar' is missing in type 'String'.
         [x: string]: string; // error
     }
     
@@ -43,7 +40,6 @@ tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingW
 !!! error TS2415: Class 'B' incorrectly extends base class 'A<Base>'.
 !!! error TS2415:   Index signatures are incompatible.
 !!! error TS2415:     Type 'string' is not assignable to type 'Base'.
-!!! error TS2415:       Property 'foo' is missing in type 'String'.
                           ~~~~
 !!! error TS2344: Type 'Base' does not satisfy the constraint 'Derived'.
 !!! error TS2344:   Property 'bar' is missing in type 'Base'.
diff --git a/tests/baselines/reference/typeArgumentConstraintResolution1.errors.txt b/tests/baselines/reference/typeArgumentConstraintResolution1.errors.txt
index d7cf5e83b8..1131b6e1a6 100644
--- a/tests/baselines/reference/typeArgumentConstraintResolution1.errors.txt
+++ b/tests/baselines/reference/typeArgumentConstraintResolution1.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/compiler/typeArgumentConstraintResolution1.ts(4,12): error TS2345: Argument of type 'string' is not assignable to parameter of type 'Date'.
-  Property 'toDateString' is missing in type 'String'.
 tests/cases/compiler/typeArgumentConstraintResolution1.ts(11,12): error TS2345: Argument of type 'string' is not assignable to parameter of type 'Date'.
 
 
@@ -10,7 +9,6 @@ tests/cases/compiler/typeArgumentConstraintResolution1.ts(11,12): error TS2345:
     foo1<Date>(""); // should error
                ~~
 !!! error TS2345: Argument of type 'string' is not assignable to parameter of type 'Date'.
-!!! error TS2345:   Property 'toDateString' is missing in type 'String'.
     
     
     
diff --git a/tests/baselines/reference/typeGuardFunctionErrors.errors.txt b/tests/baselines/reference/typeGuardFunctionErrors.errors.txt
index 4756b83b30..9ecad00767 100644
--- a/tests/baselines/reference/typeGuardFunctionErrors.errors.txt
+++ b/tests/baselines/reference/typeGuardFunctionErrors.errors.txt
@@ -44,7 +44,6 @@ tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(98,22)
 tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(98,25): error TS1005: ';' expected.
 tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(98,27): error TS1005: ';' expected.
 tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(105,16): error TS2322: Type 'boolean' is not assignable to type 'D'.
-  Property 'm1' is missing in type 'Boolean'.
 tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(105,16): error TS2409: Return type of constructor signature must be assignable to the instance type of the class
 tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(111,16): error TS2408: Setters cannot return a value.
 tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(120,22): error TS2304: Cannot find name 'p1'.
@@ -249,7 +248,6 @@ tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(137,39
             return true;
                    ~~~~
 !!! error TS2322: Type 'boolean' is not assignable to type 'D'.
-!!! error TS2322:   Property 'm1' is missing in type 'Boolean'.
                    ~~~~
 !!! error TS2409: Return type of constructor signature must be assignable to the instance type of the class
         }
diff --git a/tests/baselines/reference/typeGuardOfFormTypeOfPrimitiveSubtype.js b/tests/baselines/reference/typeGuardOfFormTypeOfPrimitiveSubtype.js
new file mode 100644
index 0000000000..0bd0389017
--- /dev/null
+++ b/tests/baselines/reference/typeGuardOfFormTypeOfPrimitiveSubtype.js
@@ -0,0 +1,45 @@
+//// [typeGuardOfFormTypeOfPrimitiveSubtype.ts]
+let a: {};
+let b: {toString(): string};
+if (typeof a === "number") {
+    let c: number = a;
+}
+if (typeof a === "string") {
+    let c: string = a;
+}
+if (typeof a === "boolean") {
+    let c: boolean = a;
+}
+
+if (typeof b === "number") {
+    let c: number = b;
+}
+if (typeof b === "string") {
+    let c: string = b;
+}
+if (typeof b === "boolean") {
+    let c: boolean = b;
+}
+
+
+//// [typeGuardOfFormTypeOfPrimitiveSubtype.js]
+var a;
+var b;
+if (typeof a === "number") {
+    var c = a;
+}
+if (typeof a === "string") {
+    var c = a;
+}
+if (typeof a === "boolean") {
+    var c = a;
+}
+if (typeof b === "number") {
+    var c = b;
+}
+if (typeof b === "string") {
+    var c = b;
+}
+if (typeof b === "boolean") {
+    var c = b;
+}
diff --git a/tests/baselines/reference/typeGuardOfFormTypeOfPrimitiveSubtype.symbols b/tests/baselines/reference/typeGuardOfFormTypeOfPrimitiveSubtype.symbols
new file mode 100644
index 0000000000..da962b6060
--- /dev/null
+++ b/tests/baselines/reference/typeGuardOfFormTypeOfPrimitiveSubtype.symbols
@@ -0,0 +1,52 @@
+=== tests/cases/conformance/expressions/typeGuards/typeGuardOfFormTypeOfPrimitiveSubtype.ts ===
+let a: {};
+>a : Symbol(a, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 0, 3))
+
+let b: {toString(): string};
+>b : Symbol(b, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 1, 3))
+>toString : Symbol(toString, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 1, 8))
+
+if (typeof a === "number") {
+>a : Symbol(a, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 0, 3))
+
+    let c: number = a;
+>c : Symbol(c, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 3, 7))
+>a : Symbol(a, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 0, 3))
+}
+if (typeof a === "string") {
+>a : Symbol(a, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 0, 3))
+
+    let c: string = a;
+>c : Symbol(c, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 6, 7))
+>a : Symbol(a, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 0, 3))
+}
+if (typeof a === "boolean") {
+>a : Symbol(a, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 0, 3))
+
+    let c: boolean = a;
+>c : Symbol(c, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 9, 7))
+>a : Symbol(a, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 0, 3))
+}
+
+if (typeof b === "number") {
+>b : Symbol(b, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 1, 3))
+
+    let c: number = b;
+>c : Symbol(c, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 13, 7))
+>b : Symbol(b, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 1, 3))
+}
+if (typeof b === "string") {
+>b : Symbol(b, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 1, 3))
+
+    let c: string = b;
+>c : Symbol(c, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 16, 7))
+>b : Symbol(b, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 1, 3))
+}
+if (typeof b === "boolean") {
+>b : Symbol(b, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 1, 3))
+
+    let c: boolean = b;
+>c : Symbol(c, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 19, 7))
+>b : Symbol(b, Decl(typeGuardOfFormTypeOfPrimitiveSubtype.ts, 1, 3))
+}
+
diff --git a/tests/baselines/reference/typeGuardOfFormTypeOfPrimitiveSubtype.types b/tests/baselines/reference/typeGuardOfFormTypeOfPrimitiveSubtype.types
new file mode 100644
index 0000000000..7e88ca5cb9
--- /dev/null
+++ b/tests/baselines/reference/typeGuardOfFormTypeOfPrimitiveSubtype.types
@@ -0,0 +1,70 @@
+=== tests/cases/conformance/expressions/typeGuards/typeGuardOfFormTypeOfPrimitiveSubtype.ts ===
+let a: {};
+>a : {}
+
+let b: {toString(): string};
+>b : { toString(): string; }
+>toString : () => string
+
+if (typeof a === "number") {
+>typeof a === "number" : boolean
+>typeof a : string
+>a : {}
+>"number" : string
+
+    let c: number = a;
+>c : number
+>a : number
+}
+if (typeof a === "string") {
+>typeof a === "string" : boolean
+>typeof a : string
+>a : {}
+>"string" : string
+
+    let c: string = a;
+>c : string
+>a : string
+}
+if (typeof a === "boolean") {
+>typeof a === "boolean" : boolean
+>typeof a : string
+>a : {}
+>"boolean" : string
+
+    let c: boolean = a;
+>c : boolean
+>a : boolean
+}
+
+if (typeof b === "number") {
+>typeof b === "number" : boolean
+>typeof b : string
+>b : { toString(): string; }
+>"number" : string
+
+    let c: number = b;
+>c : number
+>b : number
+}
+if (typeof b === "string") {
+>typeof b === "string" : boolean
+>typeof b : string
+>b : { toString(): string; }
+>"string" : string
+
+    let c: string = b;
+>c : string
+>b : string
+}
+if (typeof b === "boolean") {
+>typeof b === "boolean" : boolean
+>typeof b : string
+>b : { toString(): string; }
+>"boolean" : string
+
+    let c: boolean = b;
+>c : boolean
+>b : boolean
+}
+
diff --git a/tests/baselines/reference/typeName1.errors.txt b/tests/baselines/reference/typeName1.errors.txt
index 84c8be360b..152a5b951e 100644
--- a/tests/baselines/reference/typeName1.errors.txt
+++ b/tests/baselines/reference/typeName1.errors.txt
@@ -1,31 +1,19 @@
 tests/cases/compiler/typeName1.ts(9,5): error TS2322: Type 'number' is not assignable to type '{ f(s: string): number; f(n: number): string; }'.
-  Property 'f' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(10,5): error TS2322: Type 'number' is not assignable to type '{ f(s: string): number; }'.
-  Property 'f' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(11,5): error TS2322: Type 'number' is not assignable to type '{ (s: string): number; (n: number): string; }'.
 tests/cases/compiler/typeName1.ts(12,5): error TS2322: Type 'number' is not assignable to type '{ x: any; y: any; z: number; f(n: number): string; f(s: string): number; }'.
-  Property 'x' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(13,5): error TS2322: Type 'number' is not assignable to type '{ (s: string): number; (n: number): string; x: any; y: any; z: number; f(n: number): string; f(s: string): number; }'.
-  Property 'x' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(14,5): error TS2322: Type 'number' is not assignable to type '{ z: number; f: { (n: number): string; (s: string): number; }; }'.
-  Property 'z' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(15,5): error TS2322: Type 'number' is not assignable to type '(s: string) => boolean'.
 tests/cases/compiler/typeName1.ts(16,5): error TS2322: Type 'number' is not assignable to type '{ (): boolean; [s: string]: { x: any; y: any; }; [n: number]: { x: any; y: any; }; z: I; }'.
-  Property 'z' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(16,10): error TS2411: Property 'z' of type 'I' is not assignable to string index type '{ x: any; y: any; }'.
 tests/cases/compiler/typeName1.ts(17,5): error TS2322: Type 'number' is not assignable to type 'I'.
-  Property 'k' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(18,5): error TS2322: Type 'number' is not assignable to type 'I[][][][]'.
-  Property 'length' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(19,5): error TS2322: Type 'number' is not assignable to type '{ z: I; x: boolean; }[][]'.
-  Property 'length' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(20,5): error TS2322: Type 'number' is not assignable to type '{ z: I; x: boolean; y: (s: string) => boolean; w: { (): boolean; [s: string]: { x: any; y: any; }; [n: number]: { x: any; y: any; }; z: I; }; }[][]'.
-  Property 'length' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(20,50): error TS2411: Property 'z' of type 'I' is not assignable to string index type '{ x: any; y: any; }'.
 tests/cases/compiler/typeName1.ts(21,5): error TS2322: Type 'number' is not assignable to type '{ (): {}; new (): number; new (n: number): number; x: string; w: { y: number; }; }'.
-  Property 'x' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(22,5): error TS2322: Type 'number' is not assignable to type '{ (): string; f(x: number): boolean; p: any; q: any; }'.
-  Property 'f' is missing in type 'Number'.
 tests/cases/compiler/typeName1.ts(23,5): error TS2322: Type 'typeof C' is not assignable to type 'number'.
 
 
@@ -41,61 +29,49 @@ tests/cases/compiler/typeName1.ts(23,5): error TS2322: Type 'typeof C' is not as
     var x1:{ f(s:string):number;f(n:number):string; }=3;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '{ f(s: string): number; f(n: number): string; }'.
-!!! error TS2322:   Property 'f' is missing in type 'Number'.
     var x2:{ f(s:string):number; } =3;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '{ f(s: string): number; }'.
-!!! error TS2322:   Property 'f' is missing in type 'Number'.
     var x3:{ (s:string):number;(n:number):string; }=3;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '{ (s: string): number; (n: number): string; }'.
     var x4:{ x;y;z:number;f(n:number):string;f(s:string):number; }=3;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '{ x: any; y: any; z: number; f(n: number): string; f(s: string): number; }'.
-!!! error TS2322:   Property 'x' is missing in type 'Number'.
     var x5:{ (s:string):number;(n:number):string;x;y;z:number;f(n:number):string;f(s:string):number; }=3;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '{ (s: string): number; (n: number): string; x: any; y: any; z: number; f(n: number): string; f(s: string): number; }'.
-!!! error TS2322:   Property 'x' is missing in type 'Number'.
     var x6:{ z:number;f:{(n:number):string;(s:string):number;}; }=3;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '{ z: number; f: { (n: number): string; (s: string): number; }; }'.
-!!! error TS2322:   Property 'z' is missing in type 'Number'.
     var x7:(s:string)=>boolean=3;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '(s: string) => boolean'.
     var x8:{ z:I;[s:string]:{ x; y; };[n:number]:{x; y;};():boolean; }=3;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type '{ (): boolean; [s: string]: { x: any; y: any; }; [n: number]: { x: any; y: any; }; z: I; }'.
-!!! error TS2322:   Property 'z' is missing in type 'Number'.
              ~~~~
 !!! error TS2411: Property 'z' of type 'I' is not assignable to string index type '{ x: any; y: any; }'.
     var x9:I=3;
         ~~
 !!! error TS2322: Type 'number' is not assignable to type 'I'.
-!!! error TS2322:   Property 'k' is missing in type 'Number'.
     var x10:I[][][][]=3;
         ~~~
 !!! error TS2322: Type 'number' is not assignable to type 'I[][][][]'.
-!!! error TS2322:   Property 'length' is missing in type 'Number'.
     var x11:{z:I;x:boolean;}[][]=3;
         ~~~
 !!! error TS2322: Type 'number' is not assignable to type '{ z: I; x: boolean; }[][]'.
-!!! error TS2322:   Property 'length' is missing in type 'Number'.
     var x12:{z:I;x:boolean;y:(s:string)=>boolean;w:{ z:I;[s:string]:{ x; y; };[n:number]:{x; y;};():boolean; };}[][]=3;
         ~~~
 !!! error TS2322: Type 'number' is not assignable to type '{ z: I; x: boolean; y: (s: string) => boolean; w: { (): boolean; [s: string]: { x: any; y: any; }; [n: number]: { x: any; y: any; }; z: I; }; }[][]'.
-!!! error TS2322:   Property 'length' is missing in type 'Number'.
                                                      ~~~~
 !!! error TS2411: Property 'z' of type 'I' is not assignable to string index type '{ x: any; y: any; }'.
     var x13:{ new(): number; new(n:number):number; x: string; w: {y: number;}; (): {}; } = 3;
         ~~~
 !!! error TS2322: Type 'number' is not assignable to type '{ (): {}; new (): number; new (n: number): number; x: string; w: { y: number; }; }'.
-!!! error TS2322:   Property 'x' is missing in type 'Number'.
     var x14:{ f(x:number):boolean; p; q; ():string; }=3;
         ~~~
 !!! error TS2322: Type 'number' is not assignable to type '{ (): string; f(x: number): boolean; p: any; q: any; }'.
-!!! error TS2322:   Property 'f' is missing in type 'Number'.
     var x15:number=C;
         ~~~
 !!! error TS2322: Type 'typeof C' is not assignable to type 'number'.
diff --git a/tests/baselines/reference/typeOfOnTypeArg.errors.txt b/tests/baselines/reference/typeOfOnTypeArg.errors.txt
index 8562b7f134..46b48983f2 100644
--- a/tests/baselines/reference/typeOfOnTypeArg.errors.txt
+++ b/tests/baselines/reference/typeOfOnTypeArg.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/compiler/typeOfOnTypeArg.ts(7,6): error TS2345: Argument of type 'number' is not assignable to parameter of type '{ '': number; }'.
-  Property '''' is missing in type 'Number'.
 
 
 ==== tests/cases/compiler/typeOfOnTypeArg.ts (1 errors) ====
@@ -12,5 +11,4 @@ tests/cases/compiler/typeOfOnTypeArg.ts(7,6): error TS2345: Argument of type 'nu
     fill(32);
          ~~
 !!! error TS2345: Argument of type 'number' is not assignable to parameter of type '{ '': number; }'.
-!!! error TS2345:   Property '''' is missing in type 'Number'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/typeParameterAsTypeParameterConstraint2.errors.txt b/tests/baselines/reference/typeParameterAsTypeParameterConstraint2.errors.txt
index 282e942e0f..0e148cb568 100644
--- a/tests/baselines/reference/typeParameterAsTypeParameterConstraint2.errors.txt
+++ b/tests/baselines/reference/typeParameterAsTypeParameterConstraint2.errors.txt
@@ -10,7 +10,6 @@ tests/cases/conformance/types/typeParameters/typeArgumentLists/typeParameterAsTy
 tests/cases/conformance/types/typeParameters/typeArgumentLists/typeParameterAsTypeParameterConstraint2.ts(18,10): error TS2345: Argument of type 'string[]' is not assignable to parameter of type '{ length: any[]; }'.
   Types of property 'length' are incompatible.
     Type 'number' is not assignable to type 'any[]'.
-      Property 'length' is missing in type 'Number'.
 
 
 ==== tests/cases/conformance/types/typeParameters/typeArgumentLists/typeParameterAsTypeParameterConstraint2.ts (6 errors) ====
@@ -49,5 +48,4 @@ tests/cases/conformance/types/typeParameters/typeArgumentLists/typeParameterAsTy
              ~~~~
 !!! error TS2345: Argument of type 'string[]' is not assignable to parameter of type '{ length: any[]; }'.
 !!! error TS2345:   Types of property 'length' are incompatible.
-!!! error TS2345:     Type 'number' is not assignable to type 'any[]'.
-!!! error TS2345:       Property 'length' is missing in type 'Number'.
\ No newline at end of file
+!!! error TS2345:     Type 'number' is not assignable to type 'any[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/undefinedTypeAssignment1.errors.txt b/tests/baselines/reference/undefinedTypeAssignment1.errors.txt
index b8dd74a58a..61021a463a 100644
--- a/tests/baselines/reference/undefinedTypeAssignment1.errors.txt
+++ b/tests/baselines/reference/undefinedTypeAssignment1.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/compiler/undefinedTypeAssignment1.ts(1,1): error TS2397: Declaration name conflicts with built-in global identifier 'undefined'.
+tests/cases/compiler/undefinedTypeAssignment1.ts(1,6): error TS2397: Declaration name conflicts with built-in global identifier 'undefined'.
 
 
 ==== tests/cases/compiler/undefinedTypeAssignment1.ts (1 errors) ====
     type undefined = string;
-    ~~~~~~~~~~~~~~~~~~~~~~~~
+         ~~~~~~~~~
 !!! error TS2397: Declaration name conflicts with built-in global identifier 'undefined'.
     function p(undefined = "wat") {
     	return undefined;
diff --git a/tests/baselines/reference/unqualifiedCallToClassStatic1.errors.txt b/tests/baselines/reference/unqualifiedCallToClassStatic1.errors.txt
index af9edd115e..4152c182d4 100644
--- a/tests/baselines/reference/unqualifiedCallToClassStatic1.errors.txt
+++ b/tests/baselines/reference/unqualifiedCallToClassStatic1.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/unqualifiedCallToClassStatic1.ts(4,3): error TS2304: Cannot find name 'foo'.
+tests/cases/compiler/unqualifiedCallToClassStatic1.ts(4,3): error TS2662: Cannot find name 'foo'. Did you mean the static member 'Vector.foo'?
 
 
 ==== tests/cases/compiler/unqualifiedCallToClassStatic1.ts (1 errors) ====
@@ -7,6 +7,6 @@ tests/cases/compiler/unqualifiedCallToClassStatic1.ts(4,3): error TS2304: Cannot
       // 'foo' cannot be called in an unqualified manner.
       foo();
       ~~~
-!!! error TS2304: Cannot find name 'foo'.
+!!! error TS2662: Cannot find name 'foo'. Did you mean the static member 'Vector.foo'?
      }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/wrappedRecursiveGenericType.errors.txt b/tests/baselines/reference/wrappedRecursiveGenericType.errors.txt
index 5afc7361a2..da97e05713 100644
--- a/tests/baselines/reference/wrappedRecursiveGenericType.errors.txt
+++ b/tests/baselines/reference/wrappedRecursiveGenericType.errors.txt
@@ -1,5 +1,4 @@
 tests/cases/compiler/wrappedRecursiveGenericType.ts(13,1): error TS2322: Type 'number' is not assignable to type 'X<number>'.
-  Property 'e' is missing in type 'Number'.
 tests/cases/compiler/wrappedRecursiveGenericType.ts(14,1): error TS2322: Type 'number' is not assignable to type 'X<number>'.
 
 
@@ -19,7 +18,6 @@ tests/cases/compiler/wrappedRecursiveGenericType.ts(14,1): error TS2322: Type 'n
     x.a.b.val = 5;     // val -> X<number> (This should be an error)
     ~~~~~~~~~
 !!! error TS2322: Type 'number' is not assignable to type 'X<number>'.
-!!! error TS2322:   Property 'e' is missing in type 'Number'.
     x.a.b.a.val = 5;   // val -> X<number> (This should be an error)
     ~~~~~~~~~~~
 !!! error TS2322: Type 'number' is not assignable to type 'X<number>'.
\ No newline at end of file
diff --git a/tests/cases/compiler/accessInstanceMemberFromStaticMethod01.ts b/tests/cases/compiler/accessInstanceMemberFromStaticMethod01.ts
new file mode 100644
index 0000000000..cdca697f13
--- /dev/null
+++ b/tests/cases/compiler/accessInstanceMemberFromStaticMethod01.ts
@@ -0,0 +1,7 @@
+class C {
+    static foo: string;
+
+    bar() {
+        let k = foo;
+    }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/accessStaticMemberFromInstanceMethod01.ts b/tests/cases/compiler/accessStaticMemberFromInstanceMethod01.ts
new file mode 100644
index 0000000000..654ae39aac
--- /dev/null
+++ b/tests/cases/compiler/accessStaticMemberFromInstanceMethod01.ts
@@ -0,0 +1,7 @@
+class C {
+    foo: string;
+
+    static bar() {
+        let k = foo;
+    }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/capturedLetConstInLoop11.ts b/tests/cases/compiler/capturedLetConstInLoop11.ts
new file mode 100644
index 0000000000..bda0cec9d6
--- /dev/null
+++ b/tests/cases/compiler/capturedLetConstInLoop11.ts
@@ -0,0 +1,13 @@
+for (;;) {
+    let x = 1;
+    () => x;
+}
+
+function foo() {
+    for (;;) {
+        const a = 0;
+        switch(a) {
+            case 0: return () => a;
+        }
+    }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/capturedLetConstInLoop11_ES6.ts b/tests/cases/compiler/capturedLetConstInLoop11_ES6.ts
new file mode 100644
index 0000000000..24005ed483
--- /dev/null
+++ b/tests/cases/compiler/capturedLetConstInLoop11_ES6.ts
@@ -0,0 +1,14 @@
+// @target: ES6
+for (;;) {
+    let x = 1;
+    () => x;
+}
+
+function foo() {
+    for (;;) {
+        const a = 0;
+        switch(a) {
+            case 0: return () => a;
+        }
+    }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/declarationEmit_UnknownImport.ts b/tests/cases/compiler/declarationEmit_UnknownImport.ts
new file mode 100644
index 0000000000..9f6344322b
--- /dev/null
+++ b/tests/cases/compiler/declarationEmit_UnknownImport.ts
@@ -0,0 +1,6 @@
+// @target: es5
+// @module: commonjs
+// @declaration: true
+
+import Foo = SomeNonExistingName
+export {Foo}
\ No newline at end of file
diff --git a/tests/cases/compiler/declarationEmit_UnknownImport2.ts b/tests/cases/compiler/declarationEmit_UnknownImport2.ts
new file mode 100644
index 0000000000..035d1d860c
--- /dev/null
+++ b/tests/cases/compiler/declarationEmit_UnknownImport2.ts
@@ -0,0 +1,6 @@
+// @target: es5
+// @module: commonjs
+// @declaration: true
+
+import Foo From './Foo'; // Syntax error
+export default Foo
\ No newline at end of file
diff --git a/tests/cases/compiler/globalIsContextualKeyword.ts b/tests/cases/compiler/globalIsContextualKeyword.ts
new file mode 100644
index 0000000000..ceae834a26
--- /dev/null
+++ b/tests/cases/compiler/globalIsContextualKeyword.ts
@@ -0,0 +1,16 @@
+function a() {
+    let global = 1;
+}
+function b() {
+    class global {}
+}
+
+namespace global {
+}
+
+function foo(global: number) {
+}
+
+let obj = {
+    global: "123"
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationCollidingNamesInAugmentation1.ts b/tests/cases/compiler/moduleAugmentationCollidingNamesInAugmentation1.ts
new file mode 100644
index 0000000000..7cbb78a333
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationCollidingNamesInAugmentation1.ts
@@ -0,0 +1,33 @@
+// @module: amd
+// @declaration: true
+
+// @filename: map1.ts
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface I {x0}
+}
+
+// @filename: map2.ts
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface I {x1}
+}
+
+
+// @filename: observable.ts
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+// @filename: main.ts
+import { Observable } from "./observable"
+import "./map1";
+import "./map2";
+
+let x: Observable<number>;
diff --git a/tests/cases/compiler/moduleAugmentationDeclarationEmit1.ts b/tests/cases/compiler/moduleAugmentationDeclarationEmit1.ts
new file mode 100644
index 0000000000..460cdfc53b
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationDeclarationEmit1.ts
@@ -0,0 +1,33 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: map.ts
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: number;
+    }
+}
+
+// @filename: observable.ts
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+export namespace Observable {
+    let someValue: number;
+}
+
+
+// @filename: main.ts
+import { Observable } from "./observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationDeclarationEmit2.ts b/tests/cases/compiler/moduleAugmentationDeclarationEmit2.ts
new file mode 100644
index 0000000000..22cb439267
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationDeclarationEmit2.ts
@@ -0,0 +1,35 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: map.ts
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: string;
+    }
+}
+
+// @filename: observable.ts
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+export namespace Observable {
+    export let someValue: number;
+}
+
+
+// @filename: main.ts
+import { Observable } from "./observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
+let z1 = Observable.someValue.toFixed();
+let z2 = Observable.someAnotherValue.toLowerCase();
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationDisallowedExtensions.ts b/tests/cases/compiler/moduleAugmentationDisallowedExtensions.ts
new file mode 100644
index 0000000000..b4b286db50
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationDisallowedExtensions.ts
@@ -0,0 +1,46 @@
+// @module: commonjs
+
+// @filename: x0.ts
+export let a = 1;
+
+// @filename: x.ts
+
+namespace N1 {
+    export let x = 1;
+}
+
+declare module "./observable" {
+    var x: number;
+    let y: number;
+    const z: number;
+    let {x1, y1, z0: {n}, z1: {arr: [el1, el2, el3]}}: {x1: number, y1: string, z0: {n: number}, z1: {arr: number[]} }
+    interface A { x }
+    namespace N {
+        export class C {}
+    }
+    class Cls {}
+    function foo(): number;
+    type T = number;
+    import * as all from "./x0";
+    import {a} from "./x0";
+    export * from "./x0";
+    export {a} from "./x0";
+}
+
+declare module "./test" {
+    export = N1;
+}
+export {}
+
+// @filename: observable.ts
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+export var x = 1;
+
+// @filename: test.ts
+export let b = 1;
+
+// @filename: main.ts
+import { Observable } from "./observable"
+import "./x";
diff --git a/tests/cases/compiler/moduleAugmentationExtendAmbientModule1.ts b/tests/cases/compiler/moduleAugmentationExtendAmbientModule1.ts
new file mode 100644
index 0000000000..b8b144fcc1
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationExtendAmbientModule1.ts
@@ -0,0 +1,34 @@
+// @module: commonjs
+
+// @filename: map.ts
+import { Observable } from "observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: number;
+    }
+}
+
+// @filename: observable.d.ts
+declare module "observable" {
+    class Observable<T> {
+        filter(pred: (e:T) => boolean): Observable<T>;
+    }
+    namespace Observable {
+        let someValue: number;
+    }
+}
+
+// @filename: main.ts
+
+/// <reference path="observable.d.ts"/>
+import { Observable } from "observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationExtendAmbientModule2.ts b/tests/cases/compiler/moduleAugmentationExtendAmbientModule2.ts
new file mode 100644
index 0000000000..6e6614ce9f
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationExtendAmbientModule2.ts
@@ -0,0 +1,37 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: map.ts
+import { Observable } from "observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: string;
+    }
+}
+
+// @filename: observable.d.ts
+declare module "observable" {
+    class Observable<T> {
+        filter(pred: (e:T) => boolean): Observable<T>;
+    }
+    namespace Observable {
+        export let someValue: number;
+    }
+}
+
+// @filename: main.ts
+
+/// <reference path="observable.d.ts"/>
+import { Observable } from "observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
+let z1 = Observable.someValue.toFixed();
+let z2 = Observable.someAnotherValue.toLowerCase();
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationExtendFileModule1.ts b/tests/cases/compiler/moduleAugmentationExtendFileModule1.ts
new file mode 100644
index 0000000000..f87757b487
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationExtendFileModule1.ts
@@ -0,0 +1,32 @@
+// @module: commonjs
+
+// @filename: map.ts
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: number;
+    }
+}
+
+// @filename: observable.ts
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+export namespace Observable {
+    let someValue: number;
+}
+
+
+// @filename: main.ts
+import { Observable } from "./observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationExtendFileModule2.ts b/tests/cases/compiler/moduleAugmentationExtendFileModule2.ts
new file mode 100644
index 0000000000..454e514879
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationExtendFileModule2.ts
@@ -0,0 +1,34 @@
+// @module: commonjs
+
+// @filename: map.ts
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    namespace Observable {
+        let someAnotherValue: string;
+    }
+}
+
+// @filename: observable.ts
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+export namespace Observable {
+    export let someValue: number;
+}
+
+
+// @filename: main.ts
+import { Observable } from "./observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
+let z1 = Observable.someValue.toFixed();
+let z2 = Observable.someAnotherValue.toLowerCase();
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationGlobal1.ts b/tests/cases/compiler/moduleAugmentationGlobal1.ts
new file mode 100644
index 0000000000..bef373ff13
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal1.ts
@@ -0,0 +1,18 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: f1.ts
+export class A {x: number;}
+
+// @filename: f2.ts
+import {A} from "./f1";
+
+// change the shape of Array<T>
+declare global {
+    interface Array<T> {
+        getA(): A;
+    }
+}
+
+let x = [1];
+let y = x.getA().x;
diff --git a/tests/cases/compiler/moduleAugmentationGlobal2.ts b/tests/cases/compiler/moduleAugmentationGlobal2.ts
new file mode 100644
index 0000000000..5a5c44f110
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal2.ts
@@ -0,0 +1,18 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: f1.ts
+export class A {};
+// @filename: f2.ts
+
+// change the shape of Array<T>
+import {A} from "./f1";
+
+declare global {
+    interface Array<T> {
+        getCountAsString(): string;
+    }
+}
+
+let x = [1];
+let y = x.getCountAsString().toLowerCase();
diff --git a/tests/cases/compiler/moduleAugmentationGlobal3.ts b/tests/cases/compiler/moduleAugmentationGlobal3.ts
new file mode 100644
index 0000000000..5986b689c5
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal3.ts
@@ -0,0 +1,21 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: f1.ts
+export class A {};
+// @filename: f2.ts
+
+// change the shape of Array<T>
+import {A} from "./f1";
+
+declare global {
+    interface Array<T> {
+        getCountAsString(): string;
+    }
+}
+
+// @filename: f3.ts
+import "./f2";
+
+let x = [1];
+let y = x.getCountAsString().toLowerCase();
diff --git a/tests/cases/compiler/moduleAugmentationGlobal4.ts b/tests/cases/compiler/moduleAugmentationGlobal4.ts
new file mode 100644
index 0000000000..44ba2ba9c5
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal4.ts
@@ -0,0 +1,18 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: f1.ts
+declare global {
+    interface Something {x}
+}
+export {};
+// @filename: f2.ts
+
+declare global {
+    interface Something {y}
+}
+export {};
+// @filename: f3.ts
+import "./f1";
+import "./f2";
+
diff --git a/tests/cases/compiler/moduleAugmentationGlobal5.ts b/tests/cases/compiler/moduleAugmentationGlobal5.ts
new file mode 100644
index 0000000000..6d2920fd55
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal5.ts
@@ -0,0 +1,21 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: f1.d.ts
+declare module "A" {
+    global {
+        interface Something {x}
+    }
+}
+// @filename: f2.d.ts
+declare module "B" {
+    global {
+        interface Something {y}
+    }
+}
+// @filename: f3.ts
+/// <reference path="f1.d.ts"/>
+/// <reference path="f2.d.ts"/>
+import "A";
+import "B";
+
diff --git a/tests/cases/compiler/moduleAugmentationGlobal6.ts b/tests/cases/compiler/moduleAugmentationGlobal6.ts
new file mode 100644
index 0000000000..37e5e33725
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal6.ts
@@ -0,0 +1,3 @@
+declare global {
+    interface Array<T> { x }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationGlobal6_1.ts b/tests/cases/compiler/moduleAugmentationGlobal6_1.ts
new file mode 100644
index 0000000000..d255b7f831
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal6_1.ts
@@ -0,0 +1,3 @@
+global {
+    interface Array<T> { x }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationGlobal7.ts b/tests/cases/compiler/moduleAugmentationGlobal7.ts
new file mode 100644
index 0000000000..66dd41c8bc
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal7.ts
@@ -0,0 +1,5 @@
+namespace A {
+    declare global {
+        interface Array<T> { x }
+    }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationGlobal7_1.ts b/tests/cases/compiler/moduleAugmentationGlobal7_1.ts
new file mode 100644
index 0000000000..b7d99dfd41
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal7_1.ts
@@ -0,0 +1,5 @@
+namespace A {
+    global {
+        interface Array<T> { x }
+    }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationGlobal8.ts b/tests/cases/compiler/moduleAugmentationGlobal8.ts
new file mode 100644
index 0000000000..e28b07d6bf
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal8.ts
@@ -0,0 +1,8 @@
+// @target: es5
+// @module: amd
+namespace A {
+    declare global {
+        interface Array<T> { x }
+    }
+}
+export {}
diff --git a/tests/cases/compiler/moduleAugmentationGlobal8_1.ts b/tests/cases/compiler/moduleAugmentationGlobal8_1.ts
new file mode 100644
index 0000000000..9031e4742b
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationGlobal8_1.ts
@@ -0,0 +1,8 @@
+// @target: es5
+// @module: amd
+namespace A {
+    global {
+        interface Array<T> { x }
+    }
+}
+export {}
diff --git a/tests/cases/compiler/moduleAugmentationImportsAndExports1.ts b/tests/cases/compiler/moduleAugmentationImportsAndExports1.ts
new file mode 100644
index 0000000000..165057cf02
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationImportsAndExports1.ts
@@ -0,0 +1,28 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: f1.ts
+export class A {}
+
+// @filename: f2.ts
+export class B {
+    n: number;
+}
+
+// @filename: f3.ts
+import {A} from "./f1";
+import {B} from "./f2";
+
+A.prototype.foo = function () { return undefined; }
+declare module "./f1" {
+    interface A {
+        foo(): B;
+    }
+}
+
+// @filename: f4.ts
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationImportsAndExports2.ts b/tests/cases/compiler/moduleAugmentationImportsAndExports2.ts
new file mode 100644
index 0000000000..8e76475c40
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationImportsAndExports2.ts
@@ -0,0 +1,40 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: f1.ts
+export class A {}
+
+// @filename: f2.ts
+export class B {
+    n: number;
+}
+
+// @filename: f3.ts
+import {A} from "./f1";
+
+A.prototype.foo = function () { return undefined; }
+
+namespace N {
+    export interface Ifc { a }
+    export interface Cls { a }
+}
+
+declare module "./f1" {
+    import {B} from "./f2";
+    export {B} from "./f2";
+    import I = N.Ifc;
+    import C = N.Cls;
+    // should have explicit export
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+
+// @filename: f4.ts
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationImportsAndExports3.ts b/tests/cases/compiler/moduleAugmentationImportsAndExports3.ts
new file mode 100644
index 0000000000..ea1d5e435d
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationImportsAndExports3.ts
@@ -0,0 +1,38 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: f1.ts
+export class A {}
+
+// @filename: f2.ts
+export class B {
+    n: number;
+}
+
+// @filename: f3.ts
+import {A} from "./f1";
+
+A.prototype.foo = function () { return undefined; }
+
+namespace N {
+    export interface Ifc { a }
+    export interface Cls { a }
+}
+
+declare module "./f1" {
+    import {B} from "./f2";
+    import I = N.Ifc;
+    import C = N.Cls;
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+
+// @filename: f4.ts
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationImportsAndExports4.ts b/tests/cases/compiler/moduleAugmentationImportsAndExports4.ts
new file mode 100644
index 0000000000..3f3b9e1940
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationImportsAndExports4.ts
@@ -0,0 +1,39 @@
+// @module: commonjs
+
+// @filename: f1.ts
+export class A {}
+
+// @filename: f2.ts
+export class B {
+    n: number;
+}
+
+// @filename: f3.ts
+import {A} from "./f1";
+import {B} from "./f2";
+
+A.prototype.foo = function () { return undefined; }
+
+namespace N {
+    export interface Ifc { a: number; }
+    export interface Cls { b: number; }
+}
+import I = N.Ifc;
+import C = N.Cls;
+
+declare module "./f1" {
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+
+// @filename: f4.ts
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
+let c = a.bar().a;
+let d = a.baz().b;
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationImportsAndExports5.ts b/tests/cases/compiler/moduleAugmentationImportsAndExports5.ts
new file mode 100644
index 0000000000..8dbff8f7cc
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationImportsAndExports5.ts
@@ -0,0 +1,40 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: f1.ts
+export class A {}
+
+// @filename: f2.ts
+export class B {
+    n: number;
+}
+
+// @filename: f3.ts
+import {A} from "./f1";
+import {B} from "./f2";
+
+A.prototype.foo = function () { return undefined; }
+
+namespace N {
+    export interface Ifc { a: number; }
+    export interface Cls { b: number; }
+}
+import I = N.Ifc;
+import C = N.Cls;
+
+declare module "./f1" {
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+
+// @filename: f4.ts
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
+let c = a.bar().a;
+let d = a.baz().b;
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationImportsAndExports6.ts b/tests/cases/compiler/moduleAugmentationImportsAndExports6.ts
new file mode 100644
index 0000000000..e9e216cbbb
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationImportsAndExports6.ts
@@ -0,0 +1,40 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: f1.ts
+export class A {}
+
+// @filename: f2.ts
+export class B {
+    n: number;
+}
+
+// @filename: f3.ts
+import {A} from "./f1";
+import {B} from "./f2";
+
+A.prototype.foo = function () { return undefined; }
+
+export namespace N {
+    export interface Ifc { a: number; }
+    export interface Cls { b: number; }
+}
+import I = N.Ifc;
+import C = N.Cls;
+
+declare module "./f1" {
+    interface A {
+        foo(): B;
+        bar(): I;
+        baz(): C;
+    }
+}
+
+// @filename: f4.ts
+import {A} from "./f1";
+import "./f3";
+
+let a: A;
+let b = a.foo().n;
+let c = a.bar().a;
+let d = a.baz().b;
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationInAmbientModule1.ts b/tests/cases/compiler/moduleAugmentationInAmbientModule1.ts
new file mode 100644
index 0000000000..07b7ccb99c
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationInAmbientModule1.ts
@@ -0,0 +1,28 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: O.d.ts
+
+declare module "Observable" {
+    class Observable {}
+}
+
+declare module "M" {
+    class Cls { x: number }
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+    module "Observable" {
+        interface Observable {
+            foo(): Cls;
+        }
+    }
+}
+
+// @filename: main.ts
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+let x: Observable;
+x.foo().x;
diff --git a/tests/cases/compiler/moduleAugmentationInAmbientModule2.ts b/tests/cases/compiler/moduleAugmentationInAmbientModule2.ts
new file mode 100644
index 0000000000..e297947857
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationInAmbientModule2.ts
@@ -0,0 +1,28 @@
+// @module: commonjs
+// @declaration: true;
+// @filename: O.d.ts
+
+declare module "Observable" {
+    class Observable {}
+}
+
+declare module "M" {
+    class Cls { x: number }
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+    module "Observable" {
+        interface Observable {
+            foo(): Cls;
+        }
+    }
+}
+
+// @filename: main.ts
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+import "Map";
+let x: Observable;
+x.foo().x;
diff --git a/tests/cases/compiler/moduleAugmentationInAmbientModule3.ts b/tests/cases/compiler/moduleAugmentationInAmbientModule3.ts
new file mode 100644
index 0000000000..bc233294ed
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationInAmbientModule3.ts
@@ -0,0 +1,38 @@
+// @module: commonjs
+// @declaration: true;
+// @filename: O.d.ts
+
+declare module "Observable" {
+    class Observable {}
+}
+
+declare module "M" {
+    class Cls { x: number }
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+    module "Observable" {
+        interface Observable {
+            foo(): Cls;
+        }
+    }
+}
+
+declare module "Map" {
+    class Cls2 { x2: number }
+    module "Observable" {
+        interface Observable {
+            foo2(): Cls2;
+        }
+    }
+}
+
+// @filename: main.ts
+/// <reference path="O.d.ts" />
+
+import {Observable} from "Observable";
+import "Map";
+let x: Observable;
+x.foo().x;
+x.foo2().x2;
diff --git a/tests/cases/compiler/moduleAugmentationInAmbientModule4.ts b/tests/cases/compiler/moduleAugmentationInAmbientModule4.ts
new file mode 100644
index 0000000000..59386ad3d0
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationInAmbientModule4.ts
@@ -0,0 +1,40 @@
+// @module: commonjs
+// @declaration: true;
+// @filename: O.d.ts
+
+declare module "Observable" {
+    class Observable {}
+}
+
+declare module "M" {
+    class Cls { x: number }
+}
+
+declare module "Map" {
+    import { Cls } from "M";
+    module "Observable" {
+        interface Observable {
+            foo(): Cls;
+        }
+    }
+}
+
+// @filename: O2.d.ts
+declare module "Map" {
+    class Cls2 { x2: number }
+    module "Observable" {
+        interface Observable {
+            foo2(): Cls2;
+        }
+    }
+}
+
+// @filename: main.ts
+/// <reference path="O.d.ts" />
+/// <reference path="O2.d.ts" />
+
+import {Observable} from "Observable";
+import "Map";
+let x: Observable;
+x.foo().x;
+x.foo2().x2;
diff --git a/tests/cases/compiler/moduleAugmentationInAmbientModule5.ts b/tests/cases/compiler/moduleAugmentationInAmbientModule5.ts
new file mode 100644
index 0000000000..5068ba396c
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationInAmbientModule5.ts
@@ -0,0 +1,23 @@
+// @module: commonjs
+// @declaration: true
+
+// @filename: array.d.ts
+declare module "A" {
+    class A { x: number; }
+}
+
+declare module "array" {
+    import {A} from "A";
+    global {
+        interface Array<T> {
+            getA(): A;
+        }
+    }
+}
+
+// @filename: f.ts
+/// <reference path="array.d.ts"/>
+import "array";
+
+let x = [1];
+let y = x.getA().x;
diff --git a/tests/cases/compiler/moduleAugmentationNoNewNames.ts b/tests/cases/compiler/moduleAugmentationNoNewNames.ts
new file mode 100644
index 0000000000..2ab82ba5f0
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationNoNewNames.ts
@@ -0,0 +1,28 @@
+// @module: commonjs
+
+// @filename: map.ts
+import { Observable } from "./observable"
+
+(<any>Observable.prototype).map = function() { }
+
+declare module "./observable" {
+    interface Observable<T> {
+        map<U>(proj: (e:T) => U): Observable<U>
+    }
+    class Bar {}
+    let y: number, z: string;
+    let {a: x, b: x1}: {a: number, b: number};
+    module Z {}
+}
+
+// @filename: observable.ts
+export declare class Observable<T> {
+    filter(pred: (e:T) => boolean): Observable<T>;
+}
+
+// @filename: main.ts
+import { Observable } from "./observable"
+import "./map";
+
+let x: Observable<number>;
+let y = x.map(x => x + 1);
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationsBundledOutput1.ts b/tests/cases/compiler/moduleAugmentationsBundledOutput1.ts
new file mode 100644
index 0000000000..e633e355d8
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationsBundledOutput1.ts
@@ -0,0 +1,57 @@
+// @target: es5
+// @module: amd
+// @declaration: true
+// @out: out.js
+
+// @filename: m1.ts
+export class Cls {
+}
+
+// @filename: m2.ts
+import {Cls} from "./m1";
+(<any>Cls.prototype).foo = function() { return 1; };
+(<any>Cls.prototype).bar = function() { return "1"; };
+
+declare module "./m1" {
+    interface Cls {
+        foo(): number;
+    }
+}
+
+declare module "./m1" {
+    interface Cls {
+        bar(): string;
+    }
+}
+
+// @filename: m3.ts
+export class C1 { x: number }
+export class C2 { x: string }
+
+// @filename: m4.ts
+import {Cls} from "./m1";
+import {C1, C2} from "./m3";
+(<any>Cls.prototype).baz1 = function() { return undefined };
+(<any>Cls.prototype).baz2 = function() { return undefined };
+
+declare module "./m1" {
+    interface Cls {
+        baz1(): C1;
+    }
+}
+
+declare module "./m1" {
+    interface Cls {
+        baz2(): C2;
+    }
+}
+
+// @filename: test.ts
+import { Cls } from "./m1";
+import "m2";
+import "m4";
+let c: Cls;
+c.foo().toExponential();
+c.bar().toLowerCase();
+c.baz1().x.toExponential();
+c.baz2().x.toLowerCase();
diff --git a/tests/cases/compiler/moduleAugmentationsImports1.ts b/tests/cases/compiler/moduleAugmentationsImports1.ts
new file mode 100644
index 0000000000..ad029bdfc4
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationsImports1.ts
@@ -0,0 +1,44 @@
+// @module: amd
+// @declaration: true
+// @out: f.js
+
+// @filename: a.ts
+export class A {}
+
+// @filename: b.ts
+export class B {x: number;}
+
+// @filename: c.d.ts
+declare module "C" {
+    class Cls {y: string; }
+}
+
+// @filename: d.ts
+/// <reference path="c.d.ts"/>
+
+import {A} from "./a";
+import {B} from "./b";
+import {Cls} from "C";
+
+A.prototype.getB = function () { return undefined; }
+A.prototype.getCls = function () { return undefined; }
+
+declare module "./a" {
+    interface A {
+        getB(): B;
+    }
+}
+
+declare module "./a" {
+    interface A {
+        getCls(): Cls;
+    }
+}
+
+// @filename: main.ts
+import {A} from "./a";
+import "d";
+
+let a: A;
+let b = a.getB().x.toFixed();
+let c = a.getCls().y.toLowerCase();
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationsImports2.ts b/tests/cases/compiler/moduleAugmentationsImports2.ts
new file mode 100644
index 0000000000..bf5b4b1cd1
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationsImports2.ts
@@ -0,0 +1,49 @@
+// @module: amd
+// @declaration: true
+// @out: f.js
+
+// @filename: a.ts
+export class A {}
+
+// @filename: b.ts
+export class B {x: number;}
+
+// @filename: c.d.ts
+declare module "C" {
+    class Cls {y: string; }
+}
+
+// @filename: d.ts
+/// <reference path="c.d.ts"/>
+
+import {A} from "./a";
+import {B} from "./b";
+
+A.prototype.getB = function () { return undefined; }
+
+declare module "./a" {
+    interface A {
+        getB(): B;
+    }
+}
+
+// @filename: e.ts
+import {A} from "./a";
+import {Cls} from "C";
+
+A.prototype.getCls = function () { return undefined; }
+
+declare module "./a" {
+    interface A {
+        getCls(): Cls;
+    }
+}
+
+// @filename: main.ts
+import {A} from "./a";
+import "d";
+import "e";
+
+let a: A;
+let b = a.getB().x.toFixed();
+let c = a.getCls().y.toLowerCase();
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationsImports3.ts b/tests/cases/compiler/moduleAugmentationsImports3.ts
new file mode 100644
index 0000000000..92cc6c73a3
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationsImports3.ts
@@ -0,0 +1,48 @@
+// @module: amd
+// @declaration: true
+// @out: f.js
+
+// @filename: a.ts
+export class A {}
+
+// @filename: b.ts
+export class B {x: number;}
+
+// @filename: c.d.ts
+declare module "C" {
+    class Cls {y: string; }
+}
+
+// @filename: d.d.ts
+declare module "D" {
+    import {A} from "a";
+    import {B} from "b";
+    module "a" {
+        interface A {
+            getB(): B;
+        }
+    }
+}
+
+// @filename: e.ts
+/// <reference path="c.d.ts"/>
+import {A} from "./a";
+import {Cls} from "C";
+
+A.prototype.getCls = function () { return undefined; }
+
+declare module "./a" {
+    interface A {
+        getCls(): Cls;
+    }
+}
+
+// @filename: main.ts
+/// <reference path="d.d.ts"/>
+import {A} from "./a";
+import "D";
+import "e";
+
+let a: A;
+let b = a.getB().x.toFixed();
+let c = a.getCls().y.toLowerCase();
\ No newline at end of file
diff --git a/tests/cases/compiler/moduleAugmentationsImports4.ts b/tests/cases/compiler/moduleAugmentationsImports4.ts
new file mode 100644
index 0000000000..5e48954c09
--- /dev/null
+++ b/tests/cases/compiler/moduleAugmentationsImports4.ts
@@ -0,0 +1,49 @@
+// @module: amd
+// @declaration: true
+// @out: f.js
+
+// @filename: a.ts
+export class A {}
+
+// @filename: b.ts
+export class B {x: number;}
+
+// @filename: c.d.ts
+declare module "C" {
+    class Cls {y: string; }
+}
+
+// @filename: d.d.ts
+declare module "D" {
+    import {A} from "a";
+    import {B} from "b";
+    module "a" {
+        interface A {
+            getB(): B;
+        }
+    }
+}
+
+// @filename: e.d.ts
+/// <reference path="c.d.ts"/>
+declare module "E" {
+    import {A} from "a";
+    import {Cls} from "C";
+
+    module "a" {
+        interface A {
+            getCls(): Cls;
+        }
+    }
+}
+
+// @filename: main.ts
+/// <reference path="d.d.ts"/>
+/// <reference path="e.d.ts"/>
+import {A} from "./a";
+import "D";
+import "E";
+
+let a: A;
+let b = a.getB().x.toFixed();
+let c = a.getCls().y.toLowerCase();
\ No newline at end of file
diff --git a/tests/cases/conformance/expressions/typeGuards/typeGuardOfFormTypeOfPrimitiveSubtype.ts b/tests/cases/conformance/expressions/typeGuards/typeGuardOfFormTypeOfPrimitiveSubtype.ts
new file mode 100644
index 0000000000..b0493db428
--- /dev/null
+++ b/tests/cases/conformance/expressions/typeGuards/typeGuardOfFormTypeOfPrimitiveSubtype.ts
@@ -0,0 +1,21 @@
+let a: {};
+let b: {toString(): string};
+if (typeof a === "number") {
+    let c: number = a;
+}
+if (typeof a === "string") {
+    let c: string = a;
+}
+if (typeof a === "boolean") {
+    let c: boolean = a;
+}
+
+if (typeof b === "number") {
+    let c: number = b;
+}
+if (typeof b === "string") {
+    let c: string = b;
+}
+if (typeof b === "boolean") {
+    let c: boolean = b;
+}
diff --git a/tests/cases/fourslash/formattingGlobalAugmentation1.ts b/tests/cases/fourslash/formattingGlobalAugmentation1.ts
new file mode 100644
index 0000000000..0499100653
--- /dev/null
+++ b/tests/cases/fourslash/formattingGlobalAugmentation1.ts
@@ -0,0 +1,8 @@
+/// <reference path="fourslash.ts"/>
+
+/////*1*/declare          global                      {
+////}
+
+format.document();
+goTo.marker("1");
+verify.currentLineContentIs("declare global {");
\ No newline at end of file
diff --git a/tests/cases/fourslash/formattingGlobalAugmentation2.ts b/tests/cases/fourslash/formattingGlobalAugmentation2.ts
new file mode 100644
index 0000000000..74f05e1a93
--- /dev/null
+++ b/tests/cases/fourslash/formattingGlobalAugmentation2.ts
@@ -0,0 +1,10 @@
+/// <reference path="fourslash.ts"/>
+
+////declare module "A" {
+/////*1*/                  global                {
+////    }
+////}
+
+format.document();
+goTo.marker("1");
+verify.currentLineContentIs("    global {");
\ No newline at end of file
diff --git a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics8.ts b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics8.ts
index ba2d9faae8..562f42124a 100644
--- a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics8.ts
+++ b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics8.ts
@@ -7,8 +7,8 @@
 verify.getSemanticDiagnostics(`[
   {
     "message": "'type aliases' can only be used in a .ts file.",
-    "start": 0,
-    "length": 11,
+    "start": 5,
+    "length": 1,
     "category": "error",
     "code": 8008
   }
diff --git a/tests/cases/fourslash/getPropertySymbolsFromBaseTypesDoesntCrash.ts b/tests/cases/fourslash/getPropertySymbolsFromBaseTypesDoesntCrash.ts
new file mode 100644
index 0000000000..0c89de63a4
--- /dev/null
+++ b/tests/cases/fourslash/getPropertySymbolsFromBaseTypesDoesntCrash.ts
@@ -0,0 +1,9 @@
+/// <reference path='fourslash.ts'/>
+
+// @Filename: file1.ts
+//// class ClassA implements IInterface {
+////     private /*1*/value: number;
+//// }
+
+goTo.marker("1");
+verify.documentHighlightsAtPositionCount(1, ["file1.ts"]);
\ No newline at end of file
diff --git a/tests/cases/fourslash/indentationInAugmentations1.ts b/tests/cases/fourslash/indentationInAugmentations1.ts
new file mode 100644
index 0000000000..8a9b81fdd6
--- /dev/null
+++ b/tests/cases/fourslash/indentationInAugmentations1.ts
@@ -0,0 +1,9 @@
+/// <reference path="fourslash.ts"/>
+
+// @module: amd
+//// export {}
+//// declare global {/*1*/
+    
+goTo.marker("1");
+edit.insertLine("");
+verify.indentationIs(4);
\ No newline at end of file
diff --git a/tests/cases/fourslash/indentationInAugmentations2.ts b/tests/cases/fourslash/indentationInAugmentations2.ts
new file mode 100644
index 0000000000..df2400207b
--- /dev/null
+++ b/tests/cases/fourslash/indentationInAugmentations2.ts
@@ -0,0 +1,8 @@
+/// <reference path="fourslash.ts"/>
+
+//// declare module "A" {
+////    global {/*1*/
+    
+goTo.marker("1");
+edit.insertLine("");
+verify.indentationIs(8);
\ No newline at end of file