merge with origin/master

2015-12-17 21:30:47 -08:00 · 2015-12-17 21:30:47 -08:00 · ae7d687a77
commit ae7d687a77
parent 314b162882 0163675464
58 changed files with 2635 additions and 772 deletions
--- a/Jakefile.js
+++ b/Jakefile.js
@ -924,7 +924,8 @@ function lintFileAsync(options, path, cb) {
 var lintTargets = compilerSources
    .concat(harnessCoreSources)
    .concat(serverCoreSources)
-    .concat(scriptSources);
+    .concat(scriptSources)
+    .concat([path.join(servicesDirectory, "services.ts")]);

 desc("Runs tslint on the compiler sources");
 task("lint", ["build-rules"], function() {
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@ -3507,7 +3507,7 @@ namespace ts {

        function findMatchingSignature(signatureList: Signature[], signature: Signature, partialMatch: boolean, ignoreReturnTypes: boolean): Signature {
            for (const s of signatureList) {
-                if (compareSignatures(s, signature, partialMatch, ignoreReturnTypes, compareTypes)) {
+                if (compareSignaturesIdentical(s, signature, partialMatch, ignoreReturnTypes, compareTypesIdentical)) {
                    return s;
                }
            }
@ -3768,11 +3768,14 @@ namespace ts {
        function createUnionOrIntersectionProperty(containingType: UnionOrIntersectionType, name: string): Symbol {
            const types = containingType.types;
            let props: Symbol[];
+            // Flags we want to propagate to the result if they exist in all source symbols
+            let commonFlags = (containingType.flags & TypeFlags.Intersection) ? SymbolFlags.Optional : SymbolFlags.None;
            for (const current of types) {
                const type = getApparentType(current);
                if (type !== unknownType) {
                    const prop = getPropertyOfType(type, name);
                    if (prop && !(getDeclarationFlagsFromSymbol(prop) & (NodeFlags.Private | NodeFlags.Protected))) {
+                        commonFlags &= prop.flags;
                        if (!props) {
                            props = [prop];
                        }
@ -3800,7 +3803,12 @@ namespace ts {
                }
                propTypes.push(getTypeOfSymbol(prop));
            }
-            const result = <TransientSymbol>createSymbol(SymbolFlags.Property | SymbolFlags.Transient | SymbolFlags.SyntheticProperty, name);
+            const result = <TransientSymbol>createSymbol(
+                SymbolFlags.Property |
+                SymbolFlags.Transient |
+                SymbolFlags.SyntheticProperty |
+                commonFlags,
+                name);
            result.containingType = containingType;
            result.declarations = declarations;
            result.type = containingType.flags & TypeFlags.Union ? getUnionType(propTypes) : getIntersectionType(propTypes);
@ -4959,7 +4967,7 @@ namespace ts {
            return checkTypeRelatedTo(source, target, identityRelation, /*errorNode*/ undefined);
        }

-        function compareTypes(source: Type, target: Type): Ternary {
+        function compareTypesIdentical(source: Type, target: Type): Ternary {
            return checkTypeRelatedTo(source, target, identityRelation, /*errorNode*/ undefined) ? Ternary.True : Ternary.False;
        }

@ -4979,10 +4987,96 @@ namespace ts {
            return checkTypeRelatedTo(source, target, assignableRelation, errorNode, headMessage, containingMessageChain);
        }

-        function isSignatureAssignableTo(source: Signature, target: Signature): boolean {
-            const sourceType = getOrCreateTypeFromSignature(source);
-            const targetType = getOrCreateTypeFromSignature(target);
-            return checkTypeRelatedTo(sourceType, targetType, assignableRelation, /*errorNode*/ undefined);
+        /**
+         * See signatureRelatedTo, compareSignaturesIdentical
+         */
+        function isSignatureAssignableTo(source: Signature, target: Signature, ignoreReturnTypes: boolean): boolean {
+            // TODO (drosen): De-duplicate code between related functions.
+            if (source === target) {
+                return true;
+            }
+            if (!target.hasRestParameter && source.minArgumentCount > target.parameters.length) {
+                return false;
+            }
+
+            // 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);
+
+            const sourceMax = getNumNonRestParameters(source);
+            const targetMax = getNumNonRestParameters(target);
+            const checkCount = getNumParametersToCheckForSignatureRelatability(source, sourceMax, target, targetMax);
+            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);
+                if (!related) {
+                    return false;
+                }
+            }
+
+            if (!ignoreReturnTypes) {
+                const targetReturnType = getReturnTypeOfSignature(target);
+                if (targetReturnType === voidType) {
+                    return true;
+                }
+                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;
+                    }
+                }
+
+                return isTypeAssignableTo(sourceReturnType, targetReturnType);
+            }
+
+            return true;
+        }
+
+        function isImplementationCompatibleWithOverload(implementation: Signature, overload: Signature): boolean {
+            const erasedSource = getErasedSignature(implementation);
+            const erasedTarget = getErasedSignature(overload);
+
+            // First see if the return types are compatible in either direction.
+            const sourceReturnType = getReturnTypeOfSignature(erasedSource);
+            const targetReturnType = getReturnTypeOfSignature(erasedTarget);
+            if (targetReturnType === voidType
+                || checkTypeRelatedTo(targetReturnType, sourceReturnType, assignableRelation, /*errorNode*/ undefined)
+                || checkTypeRelatedTo(sourceReturnType, targetReturnType, assignableRelation, /*errorNode*/ undefined)) {
+
+                return isSignatureAssignableTo(erasedSource, erasedTarget, /*ignoreReturnTypes*/ true);
+            }
+
+            return false;
+        }
+
+        function getNumNonRestParameters(signature: Signature) {
+            const numParams = signature.parameters.length;
+            return signature.hasRestParameter ?
+                numParams - 1 :
+                numParams;
+        }
+
+        function getNumParametersToCheckForSignatureRelatability(source: Signature, sourceNonRestParamCount: number, target: Signature, targetNonRestParamCount: number) {
+            if (source.hasRestParameter === target.hasRestParameter) {
+                if (source.hasRestParameter) {
+                    // If both have rest parameters, get the max and add 1 to
+                    // compensate for the rest parameter.
+                    return Math.max(sourceNonRestParamCount, targetNonRestParamCount) + 1;
+                }
+                else {
+                    return Math.min(sourceNonRestParamCount, targetNonRestParamCount);
+                }
+            }
+            else {
+                // Return the count for whichever signature doesn't have rest parameters.
+                return source.hasRestParameter ?
+                    targetNonRestParamCount :
+                    sourceNonRestParamCount;
+            }
        }

        /**
@ -5574,7 +5668,7 @@ namespace ts {
                                shouldElaborateErrors = false;
                            }
                        }
-                        // don't elaborate the primitive apparent types (like Number) 
+                        // don't elaborate the primitive apparent types (like Number)
                        // because the actual primitives will have already been reported.
                        if (shouldElaborateErrors && !isPrimitiveApparentType(source)) {
                            reportError(Diagnostics.Type_0_provides_no_match_for_the_signature_1,
@ -5621,7 +5715,11 @@ namespace ts {
                }
            }

+            /**
+             * See signatureAssignableTo, signatureAssignableTo
+             */
            function signatureRelatedTo(source: Signature, target: Signature, reportErrors: boolean): Ternary {
+                // TODO (drosen): De-duplicate code between related functions.
                if (source === target) {
                    return Ternary.True;
                }
@ -5673,10 +5771,12 @@ namespace ts {
                }

                const targetReturnType = getReturnTypeOfSignature(target);
-                if (targetReturnType === voidType) return result;
+                if (targetReturnType === voidType) {
+                    return result;
+                }
                const sourceReturnType = getReturnTypeOfSignature(source);

-                // The follow block preserves old behavior forbidding boolean returning functions from being assignable to type guard returning functions
+                // 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) {
@ -5697,7 +5797,7 @@ namespace ts {
                }
                let result = Ternary.True;
                for (let i = 0, len = sourceSignatures.length; i < len; ++i) {
-                    const related = compareSignatures(sourceSignatures[i], targetSignatures[i], /*partialMatch*/ false, /*ignoreReturnTypes*/ false, isRelatedTo);
+                    const related = compareSignaturesIdentical(sourceSignatures[i], targetSignatures[i], /*partialMatch*/ false, /*ignoreReturnTypes*/ false, isRelatedTo);
                    if (!related) {
                        return Ternary.False;
                    }
@ -5830,7 +5930,7 @@ namespace ts {
        }

        function isPropertyIdenticalTo(sourceProp: Symbol, targetProp: Symbol): boolean {
-            return compareProperties(sourceProp, targetProp, compareTypes) !== Ternary.False;
+            return compareProperties(sourceProp, targetProp, compareTypesIdentical) !== Ternary.False;
        }

        function compareProperties(sourceProp: Symbol, targetProp: Symbol, compareTypes: (source: Type, target: Type) => Ternary): Ternary {
@ -5877,7 +5977,11 @@ namespace ts {
            return false;
        }

-        function compareSignatures(source: Signature, target: Signature, partialMatch: boolean, ignoreReturnTypes: boolean, compareTypes: (s: Type, t: Type) => Ternary): Ternary {
+        /**
+         * See signatureRelatedTo, compareSignaturesIdentical
+         */
+        function compareSignaturesIdentical(source: Signature, target: Signature, partialMatch: boolean, ignoreReturnTypes: boolean, compareTypes: (s: Type, t: Type) => Ternary): Ternary {
+            // TODO (drosen): De-duplicate code between related functions.
            if (source === target) {
                return Ternary.True;
            }
@ -7605,7 +7709,7 @@ namespace ts {
                        // This signature will contribute to contextual union signature
                        signatureList = [signature];
                    }
-                    else if (!compareSignatures(signatureList[0], signature, /*partialMatch*/ false, /*ignoreReturnTypes*/ true, compareTypes)) {
+                    else if (!compareSignaturesIdentical(signatureList[0], signature, /*partialMatch*/ false, /*ignoreReturnTypes*/ true, compareTypesIdentical)) {
                        // Signatures aren't identical, do not use
                        return undefined;
                    }
@ -8280,9 +8384,9 @@ namespace ts {
                            // Props is of type 'any' or unknown
                            return links.resolvedJsxType = attributesType;
                        }
-                        else if (!(attributesType.flags & TypeFlags.ObjectType)) {
-                            // Props is not an object type
-                            error(node.tagName, Diagnostics.JSX_element_attributes_type_0_must_be_an_object_type, typeToString(attributesType));
+                        else if (attributesType.flags & TypeFlags.Union) {
+                            // Props cannot be a union type
+                            error(node.tagName, Diagnostics.JSX_element_attributes_type_0_may_not_be_a_union_type, typeToString(attributesType));
                            return links.resolvedJsxType = anyType;
                        }
                        else {
@ -11626,7 +11730,7 @@ namespace ts {
            }

            for (const otherSignature of signaturesToCheck) {
-                if (!otherSignature.hasStringLiterals && isSignatureAssignableTo(signature, otherSignature)) {
+                if (!otherSignature.hasStringLiterals && isSignatureAssignableTo(signature, otherSignature, /*ignoreReturnTypes*/ false)) {
                    return;
                }
            }
@ -11873,7 +11977,7 @@ namespace ts {
                        //
                        // The implementation is completely unrelated to the specialized signature, yet we do not check this.
                        for (const signature of signatures) {
-                            if (!signature.hasStringLiterals && !isSignatureAssignableTo(bodySignature, signature)) {
+                            if (!signature.hasStringLiterals && !isImplementationCompatibleWithOverload(bodySignature, signature)) {
                                error(signature.declaration, Diagnostics.Overload_signature_is_not_compatible_with_function_implementation);
                                break;
                            }
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@ -1691,7 +1691,7 @@
        "category": "Error",
        "code": 2528
    },
-    "JSX element attributes type '{0}' must be an object type.": {
+    "JSX element attributes type '{0}' may not be a union type.": {
        "category": "Error",
        "code": 2600
    },
--- a/src/services/services.ts
+++ b/src/services/services.ts
--- a/tests/baselines/reference/conformanceFunctionOverloads.js
+++ b/tests/baselines/reference/conformanceFunctionOverloads.js
@ -1,37 +0,0 @@
-//// [conformanceFunctionOverloads.ts]
-// Function overloads do not emit code
-
-// Function overload signature with optional parameter
-
-// Function overload signature with optional parameter
-
-// Function overloads with generic and non-generic overloads
-
-// Function overloads whose only difference is returning different unconstrained generic parameters
-
-// Function overloads whose only difference is returning different constrained generic parameters
-
-// Function overloads that differ only by type parameter constraints
-
-// Function overloads with matching accessibility
-
-// Function overloads with matching export
-
-// Function overloads with more params than implementation signature
-
-// Function overloads where return types are same infinitely recursive type reference
-
-
-
-//// [conformanceFunctionOverloads.js]
-// Function overloads do not emit code
-// Function overload signature with optional parameter
-// Function overload signature with optional parameter
-// Function overloads with generic and non-generic overloads
-// Function overloads whose only difference is returning different unconstrained generic parameters
-// Function overloads whose only difference is returning different constrained generic parameters
-// Function overloads that differ only by type parameter constraints
-// Function overloads with matching accessibility
-// Function overloads with matching export
-// Function overloads with more params than implementation signature
-// Function overloads where return types are same infinitely recursive type reference
--- a/tests/baselines/reference/conformanceFunctionOverloads.symbols
+++ b/tests/baselines/reference/conformanceFunctionOverloads.symbols
@ -1,25 +0,0 @@
-=== tests/cases/conformance/functions/conformanceFunctionOverloads.ts ===
-// Function overloads do not emit code
-No type information for this code.
-No type information for this code.// Function overload signature with optional parameter
-No type information for this code.
-No type information for this code.// Function overload signature with optional parameter
-No type information for this code.
-No type information for this code.// Function overloads with generic and non-generic overloads
-No type information for this code.
-No type information for this code.// Function overloads whose only difference is returning different unconstrained generic parameters
-No type information for this code.
-No type information for this code.// Function overloads whose only difference is returning different constrained generic parameters
-No type information for this code.
-No type information for this code.// Function overloads that differ only by type parameter constraints
-No type information for this code.
-No type information for this code.// Function overloads with matching accessibility
-No type information for this code.
-No type information for this code.// Function overloads with matching export
-No type information for this code.
-No type information for this code.// Function overloads with more params than implementation signature
-No type information for this code.
-No type information for this code.// Function overloads where return types are same infinitely recursive type reference
-No type information for this code.
-No type information for this code.
-No type information for this code.
--- a/tests/baselines/reference/conformanceFunctionOverloads.types
+++ b/tests/baselines/reference/conformanceFunctionOverloads.types
@ -1,25 +0,0 @@
-=== tests/cases/conformance/functions/conformanceFunctionOverloads.ts ===
-// Function overloads do not emit code
-No type information for this code.
-No type information for this code.// Function overload signature with optional parameter
-No type information for this code.
-No type information for this code.// Function overload signature with optional parameter
-No type information for this code.
-No type information for this code.// Function overloads with generic and non-generic overloads
-No type information for this code.
-No type information for this code.// Function overloads whose only difference is returning different unconstrained generic parameters
-No type information for this code.
-No type information for this code.// Function overloads whose only difference is returning different constrained generic parameters
-No type information for this code.
-No type information for this code.// Function overloads that differ only by type parameter constraints
-No type information for this code.
-No type information for this code.// Function overloads with matching accessibility
-No type information for this code.
-No type information for this code.// Function overloads with matching export
-No type information for this code.
-No type information for this code.// Function overloads with more params than implementation signature
-No type information for this code.
-No type information for this code.// Function overloads where return types are same infinitely recursive type reference
-No type information for this code.
-No type information for this code.
-No type information for this code.
--- a/tests/baselines/reference/functionOverloadCompatibilityWithVoid01.errors.txt
+++ b/tests/baselines/reference/functionOverloadCompatibilityWithVoid01.errors.txt
@ -0,0 +1,10 @@
+tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid01.ts(1,10): error TS2394: Overload signature is not compatible with function implementation.
+
+
+==== tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid01.ts (1 errors) ====
+    function f(x: string): number;
+             ~
+!!! error TS2394: Overload signature is not compatible with function implementation.
+    function f(x: string): void {
+        return;
+    } 
--- a/tests/baselines/reference/functionOverloadCompatibilityWithVoid01.js
+++ b/tests/baselines/reference/functionOverloadCompatibilityWithVoid01.js
@ -0,0 +1,10 @@
+//// [functionOverloadCompatibilityWithVoid01.ts]
+function f(x: string): number;
+function f(x: string): void {
+    return;
+} 
+
+//// [functionOverloadCompatibilityWithVoid01.js]
+function f(x) {
+    return;
+}
--- a/tests/baselines/reference/functionOverloadCompatibilityWithVoid02.js
+++ b/tests/baselines/reference/functionOverloadCompatibilityWithVoid02.js
@ -0,0 +1,10 @@
+//// [functionOverloadCompatibilityWithVoid02.ts]
+function f(x: string): void;
+function f(x: string): number {
+    return 0;
+} 
+
+//// [functionOverloadCompatibilityWithVoid02.js]
+function f(x) {
+    return 0;
+}
--- a/tests/baselines/reference/functionOverloadCompatibilityWithVoid02.symbols
+++ b/tests/baselines/reference/functionOverloadCompatibilityWithVoid02.symbols
@ -0,0 +1,11 @@
+=== tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid02.ts ===
+function f(x: string): void;
+>f : Symbol(f, Decl(functionOverloadCompatibilityWithVoid02.ts, 0, 0), Decl(functionOverloadCompatibilityWithVoid02.ts, 0, 28))
+>x : Symbol(x, Decl(functionOverloadCompatibilityWithVoid02.ts, 0, 11))
+
+function f(x: string): number {
+>f : Symbol(f, Decl(functionOverloadCompatibilityWithVoid02.ts, 0, 0), Decl(functionOverloadCompatibilityWithVoid02.ts, 0, 28))
+>x : Symbol(x, Decl(functionOverloadCompatibilityWithVoid02.ts, 1, 11))
+
+    return 0;
+} 
--- a/tests/baselines/reference/functionOverloadCompatibilityWithVoid02.types
+++ b/tests/baselines/reference/functionOverloadCompatibilityWithVoid02.types
@ -0,0 +1,12 @@
+=== tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid02.ts ===
+function f(x: string): void;
+>f : (x: string) => void
+>x : string
+
+function f(x: string): number {
+>f : (x: string) => void
+>x : string
+
+    return 0;
+>0 : number
+} 
--- a/tests/baselines/reference/functionOverloadCompatibilityWithVoid03.js
+++ b/tests/baselines/reference/functionOverloadCompatibilityWithVoid03.js
@ -0,0 +1,10 @@
+//// [functionOverloadCompatibilityWithVoid03.ts]
+function f(x: string): void;
+function f(x: string): void {
+    return;
+} 
+
+//// [functionOverloadCompatibilityWithVoid03.js]
+function f(x) {
+    return;
+}
--- a/tests/baselines/reference/functionOverloadCompatibilityWithVoid03.symbols
+++ b/tests/baselines/reference/functionOverloadCompatibilityWithVoid03.symbols
@ -0,0 +1,11 @@
+=== tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid03.ts ===
+function f(x: string): void;
+>f : Symbol(f, Decl(functionOverloadCompatibilityWithVoid03.ts, 0, 0), Decl(functionOverloadCompatibilityWithVoid03.ts, 0, 28))
+>x : Symbol(x, Decl(functionOverloadCompatibilityWithVoid03.ts, 0, 11))
+
+function f(x: string): void {
+>f : Symbol(f, Decl(functionOverloadCompatibilityWithVoid03.ts, 0, 0), Decl(functionOverloadCompatibilityWithVoid03.ts, 0, 28))
+>x : Symbol(x, Decl(functionOverloadCompatibilityWithVoid03.ts, 1, 11))
+
+    return;
+} 
--- a/tests/baselines/reference/functionOverloadCompatibilityWithVoid03.types
+++ b/tests/baselines/reference/functionOverloadCompatibilityWithVoid03.types
@ -0,0 +1,11 @@
+=== tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid03.ts ===
+function f(x: string): void;
+>f : (x: string) => void
+>x : string
+
+function f(x: string): void {
+>f : (x: string) => void
+>x : string
+
+    return;
+} 
--- a/tests/baselines/reference/functionOverloads22.errors.txt
+++ b/tests/baselines/reference/functionOverloads22.errors.txt
@ -1,10 +0,0 @@
-tests/cases/compiler/functionOverloads22.ts(2,10): error TS2394: Overload signature is not compatible with function implementation.
-
-
-==== tests/cases/compiler/functionOverloads22.ts (1 errors) ====
-    function foo(bar:number):{a:number;}[];
-    function foo(bar:string):{a:number; b:string;}[];
-             ~~~
-!!! error TS2394: Overload signature is not compatible with function implementation.
-    function foo(bar:any):{a:any;b?:any;}[] { return [{a:""}] }
-    
--- a/tests/baselines/reference/functionOverloads22.symbols
+++ b/tests/baselines/reference/functionOverloads22.symbols
@ -0,0 +1,19 @@
+=== tests/cases/compiler/functionOverloads22.ts ===
+function foo(bar:number):{a:number;}[];
+>foo : Symbol(foo, Decl(functionOverloads22.ts, 0, 0), Decl(functionOverloads22.ts, 0, 39), Decl(functionOverloads22.ts, 1, 49))
+>bar : Symbol(bar, Decl(functionOverloads22.ts, 0, 13))
+>a : Symbol(a, Decl(functionOverloads22.ts, 0, 26))
+
+function foo(bar:string):{a:number; b:string;}[];
+>foo : Symbol(foo, Decl(functionOverloads22.ts, 0, 0), Decl(functionOverloads22.ts, 0, 39), Decl(functionOverloads22.ts, 1, 49))
+>bar : Symbol(bar, Decl(functionOverloads22.ts, 1, 13))
+>a : Symbol(a, Decl(functionOverloads22.ts, 1, 26))
+>b : Symbol(b, Decl(functionOverloads22.ts, 1, 35))
+
+function foo(bar:any):{a:any;b?:any;}[] { return [{a:""}] }
+>foo : Symbol(foo, Decl(functionOverloads22.ts, 0, 0), Decl(functionOverloads22.ts, 0, 39), Decl(functionOverloads22.ts, 1, 49))
+>bar : Symbol(bar, Decl(functionOverloads22.ts, 2, 13))
+>a : Symbol(a, Decl(functionOverloads22.ts, 2, 23))
+>b : Symbol(b, Decl(functionOverloads22.ts, 2, 29))
+>a : Symbol(a, Decl(functionOverloads22.ts, 2, 51))
+
--- a/tests/baselines/reference/functionOverloads22.types
+++ b/tests/baselines/reference/functionOverloads22.types
@ -0,0 +1,22 @@
+=== tests/cases/compiler/functionOverloads22.ts ===
+function foo(bar:number):{a:number;}[];
+>foo : { (bar: number): { a: number; }[]; (bar: string): { a: number; b: string; }[]; }
+>bar : number
+>a : number
+
+function foo(bar:string):{a:number; b:string;}[];
+>foo : { (bar: number): { a: number; }[]; (bar: string): { a: number; b: string; }[]; }
+>bar : string
+>a : number
+>b : string
+
+function foo(bar:any):{a:any;b?:any;}[] { return [{a:""}] }
+>foo : { (bar: number): { a: number; }[]; (bar: string): { a: number; b: string; }[]; }
+>bar : any
+>a : any
+>b : any
+>[{a:""}] : { a: string; }[]
+>{a:""} : { a: string; }
+>a : string
+>"" : string
+
--- a/tests/baselines/reference/functionOverloads43.js
+++ b/tests/baselines/reference/functionOverloads43.js
@ -0,0 +1,24 @@
+//// [functionOverloads43.ts]
+function foo(bar: { a:number }[]): number;
+function foo(bar: { a:string }[]): string;
+function foo([x]: { a:number | string }[]): string | number {
+    if (x) {
+        return x.a;
+    }
+    
+    return undefined;
+}
+
+var x = foo([{a: "str"}]);
+var y = foo([{a: 100}]);
+
+//// [functionOverloads43.js]
+function foo(_a) {
+    var x = _a[0];
+    if (x) {
+        return x.a;
+    }
+    return undefined;
+}
+var x = foo([{ a: "str" }]);
+var y = foo([{ a: 100 }]);
--- a/tests/baselines/reference/functionOverloads43.symbols
+++ b/tests/baselines/reference/functionOverloads43.symbols
@ -0,0 +1,39 @@
+=== tests/cases/compiler/functionOverloads43.ts ===
+function foo(bar: { a:number }[]): number;
+>foo : Symbol(foo, Decl(functionOverloads43.ts, 0, 0), Decl(functionOverloads43.ts, 0, 42), Decl(functionOverloads43.ts, 1, 42))
+>bar : Symbol(bar, Decl(functionOverloads43.ts, 0, 13))
+>a : Symbol(a, Decl(functionOverloads43.ts, 0, 19))
+
+function foo(bar: { a:string }[]): string;
+>foo : Symbol(foo, Decl(functionOverloads43.ts, 0, 0), Decl(functionOverloads43.ts, 0, 42), Decl(functionOverloads43.ts, 1, 42))
+>bar : Symbol(bar, Decl(functionOverloads43.ts, 1, 13))
+>a : Symbol(a, Decl(functionOverloads43.ts, 1, 19))
+
+function foo([x]: { a:number | string }[]): string | number {
+>foo : Symbol(foo, Decl(functionOverloads43.ts, 0, 0), Decl(functionOverloads43.ts, 0, 42), Decl(functionOverloads43.ts, 1, 42))
+>x : Symbol(x, Decl(functionOverloads43.ts, 2, 14))
+>a : Symbol(a, Decl(functionOverloads43.ts, 2, 19))
+
+    if (x) {
+>x : Symbol(x, Decl(functionOverloads43.ts, 2, 14))
+
+        return x.a;
+>x.a : Symbol(a, Decl(functionOverloads43.ts, 2, 19))
+>x : Symbol(x, Decl(functionOverloads43.ts, 2, 14))
+>a : Symbol(a, Decl(functionOverloads43.ts, 2, 19))
+    }
+    
+    return undefined;
+>undefined : Symbol(undefined)
+}
+
+var x = foo([{a: "str"}]);
+>x : Symbol(x, Decl(functionOverloads43.ts, 10, 3))
+>foo : Symbol(foo, Decl(functionOverloads43.ts, 0, 0), Decl(functionOverloads43.ts, 0, 42), Decl(functionOverloads43.ts, 1, 42))
+>a : Symbol(a, Decl(functionOverloads43.ts, 10, 14))
+
+var y = foo([{a: 100}]);
+>y : Symbol(y, Decl(functionOverloads43.ts, 11, 3))
+>foo : Symbol(foo, Decl(functionOverloads43.ts, 0, 0), Decl(functionOverloads43.ts, 0, 42), Decl(functionOverloads43.ts, 1, 42))
+>a : Symbol(a, Decl(functionOverloads43.ts, 11, 14))
+
--- a/tests/baselines/reference/functionOverloads43.types
+++ b/tests/baselines/reference/functionOverloads43.types
@ -0,0 +1,47 @@
+=== tests/cases/compiler/functionOverloads43.ts ===
+function foo(bar: { a:number }[]): number;
+>foo : { (bar: { a: number; }[]): number; (bar: { a: string; }[]): string; }
+>bar : { a: number; }[]
+>a : number
+
+function foo(bar: { a:string }[]): string;
+>foo : { (bar: { a: number; }[]): number; (bar: { a: string; }[]): string; }
+>bar : { a: string; }[]
+>a : string
+
+function foo([x]: { a:number | string }[]): string | number {
+>foo : { (bar: { a: number; }[]): number; (bar: { a: string; }[]): string; }
+>x : { a: number | string; }
+>a : number | string
+
+    if (x) {
+>x : { a: number | string; }
+
+        return x.a;
+>x.a : number | string
+>x : { a: number | string; }
+>a : number | string
+    }
+    
+    return undefined;
+>undefined : undefined
+}
+
+var x = foo([{a: "str"}]);
+>x : string
+>foo([{a: "str"}]) : string
+>foo : { (bar: { a: number; }[]): number; (bar: { a: string; }[]): string; }
+>[{a: "str"}] : { a: string; }[]
+>{a: "str"} : { a: string; }
+>a : string
+>"str" : string
+
+var y = foo([{a: 100}]);
+>y : number
+>foo([{a: 100}]) : number
+>foo : { (bar: { a: number; }[]): number; (bar: { a: string; }[]): string; }
+>[{a: 100}] : { a: number; }[]
+>{a: 100} : { a: number; }
+>a : number
+>100 : number
+
--- a/tests/baselines/reference/functionOverloads44.js
+++ b/tests/baselines/reference/functionOverloads44.js
@ -0,0 +1,37 @@
+//// [functionOverloads44.ts]
+interface Animal { animal }
+interface Dog extends Animal { dog }
+interface Cat extends Animal { cat }
+
+function foo1(bar: { a:number }[]): Dog;
+function foo1(bar: { a:string }[]): Animal;
+function foo1([x]: { a:number | string }[]): Dog {
+    return undefined;
+}
+
+function foo2(bar: { a:number }[]): Cat;
+function foo2(bar: { a:string }[]): Cat | Dog;
+function foo2([x]: { a:number | string }[]): Cat {
+    return undefined;
+}
+
+
+var x1 = foo1([{a: "str"}]);
+var y1 = foo1([{a: 100}]);
+
+var x2 = foo2([{a: "str"}]);
+var y2 = foo2([{a: 100}]);
+
+//// [functionOverloads44.js]
+function foo1(_a) {
+    var x = _a[0];
+    return undefined;
+}
+function foo2(_a) {
+    var x = _a[0];
+    return undefined;
+}
+var x1 = foo1([{ a: "str" }]);
+var y1 = foo1([{ a: 100 }]);
+var x2 = foo2([{ a: "str" }]);
+var y2 = foo2([{ a: 100 }]);
--- a/tests/baselines/reference/functionOverloads44.symbols
+++ b/tests/baselines/reference/functionOverloads44.symbols
@ -0,0 +1,81 @@
+=== tests/cases/compiler/functionOverloads44.ts ===
+interface Animal { animal }
+>Animal : Symbol(Animal, Decl(functionOverloads44.ts, 0, 0))
+>animal : Symbol(animal, Decl(functionOverloads44.ts, 0, 18))
+
+interface Dog extends Animal { dog }
+>Dog : Symbol(Dog, Decl(functionOverloads44.ts, 0, 27))
+>Animal : Symbol(Animal, Decl(functionOverloads44.ts, 0, 0))
+>dog : Symbol(dog, Decl(functionOverloads44.ts, 1, 30))
+
+interface Cat extends Animal { cat }
+>Cat : Symbol(Cat, Decl(functionOverloads44.ts, 1, 36))
+>Animal : Symbol(Animal, Decl(functionOverloads44.ts, 0, 0))
+>cat : Symbol(cat, Decl(functionOverloads44.ts, 2, 30))
+
+function foo1(bar: { a:number }[]): Dog;
+>foo1 : Symbol(foo1, Decl(functionOverloads44.ts, 2, 36), Decl(functionOverloads44.ts, 4, 40), Decl(functionOverloads44.ts, 5, 43))
+>bar : Symbol(bar, Decl(functionOverloads44.ts, 4, 14))
+>a : Symbol(a, Decl(functionOverloads44.ts, 4, 20))
+>Dog : Symbol(Dog, Decl(functionOverloads44.ts, 0, 27))
+
+function foo1(bar: { a:string }[]): Animal;
+>foo1 : Symbol(foo1, Decl(functionOverloads44.ts, 2, 36), Decl(functionOverloads44.ts, 4, 40), Decl(functionOverloads44.ts, 5, 43))
+>bar : Symbol(bar, Decl(functionOverloads44.ts, 5, 14))
+>a : Symbol(a, Decl(functionOverloads44.ts, 5, 20))
+>Animal : Symbol(Animal, Decl(functionOverloads44.ts, 0, 0))
+
+function foo1([x]: { a:number | string }[]): Dog {
+>foo1 : Symbol(foo1, Decl(functionOverloads44.ts, 2, 36), Decl(functionOverloads44.ts, 4, 40), Decl(functionOverloads44.ts, 5, 43))
+>x : Symbol(x, Decl(functionOverloads44.ts, 6, 15))
+>a : Symbol(a, Decl(functionOverloads44.ts, 6, 20))
+>Dog : Symbol(Dog, Decl(functionOverloads44.ts, 0, 27))
+
+    return undefined;
+>undefined : Symbol(undefined)
+}
+
+function foo2(bar: { a:number }[]): Cat;
+>foo2 : Symbol(foo2, Decl(functionOverloads44.ts, 8, 1), Decl(functionOverloads44.ts, 10, 40), Decl(functionOverloads44.ts, 11, 46))
+>bar : Symbol(bar, Decl(functionOverloads44.ts, 10, 14))
+>a : Symbol(a, Decl(functionOverloads44.ts, 10, 20))
+>Cat : Symbol(Cat, Decl(functionOverloads44.ts, 1, 36))
+
+function foo2(bar: { a:string }[]): Cat | Dog;
+>foo2 : Symbol(foo2, Decl(functionOverloads44.ts, 8, 1), Decl(functionOverloads44.ts, 10, 40), Decl(functionOverloads44.ts, 11, 46))
+>bar : Symbol(bar, Decl(functionOverloads44.ts, 11, 14))
+>a : Symbol(a, Decl(functionOverloads44.ts, 11, 20))
+>Cat : Symbol(Cat, Decl(functionOverloads44.ts, 1, 36))
+>Dog : Symbol(Dog, Decl(functionOverloads44.ts, 0, 27))
+
+function foo2([x]: { a:number | string }[]): Cat {
+>foo2 : Symbol(foo2, Decl(functionOverloads44.ts, 8, 1), Decl(functionOverloads44.ts, 10, 40), Decl(functionOverloads44.ts, 11, 46))
+>x : Symbol(x, Decl(functionOverloads44.ts, 12, 15))
+>a : Symbol(a, Decl(functionOverloads44.ts, 12, 20))
+>Cat : Symbol(Cat, Decl(functionOverloads44.ts, 1, 36))
+
+    return undefined;
+>undefined : Symbol(undefined)
+}
+
+
+var x1 = foo1([{a: "str"}]);
+>x1 : Symbol(x1, Decl(functionOverloads44.ts, 17, 3))
+>foo1 : Symbol(foo1, Decl(functionOverloads44.ts, 2, 36), Decl(functionOverloads44.ts, 4, 40), Decl(functionOverloads44.ts, 5, 43))
+>a : Symbol(a, Decl(functionOverloads44.ts, 17, 16))
+
+var y1 = foo1([{a: 100}]);
+>y1 : Symbol(y1, Decl(functionOverloads44.ts, 18, 3))
+>foo1 : Symbol(foo1, Decl(functionOverloads44.ts, 2, 36), Decl(functionOverloads44.ts, 4, 40), Decl(functionOverloads44.ts, 5, 43))
+>a : Symbol(a, Decl(functionOverloads44.ts, 18, 16))
+
+var x2 = foo2([{a: "str"}]);
+>x2 : Symbol(x2, Decl(functionOverloads44.ts, 20, 3))
+>foo2 : Symbol(foo2, Decl(functionOverloads44.ts, 8, 1), Decl(functionOverloads44.ts, 10, 40), Decl(functionOverloads44.ts, 11, 46))
+>a : Symbol(a, Decl(functionOverloads44.ts, 20, 16))
+
+var y2 = foo2([{a: 100}]);
+>y2 : Symbol(y2, Decl(functionOverloads44.ts, 21, 3))
+>foo2 : Symbol(foo2, Decl(functionOverloads44.ts, 8, 1), Decl(functionOverloads44.ts, 10, 40), Decl(functionOverloads44.ts, 11, 46))
+>a : Symbol(a, Decl(functionOverloads44.ts, 21, 16))
+
--- a/tests/baselines/reference/functionOverloads44.types
+++ b/tests/baselines/reference/functionOverloads44.types
@ -0,0 +1,97 @@
+=== tests/cases/compiler/functionOverloads44.ts ===
+interface Animal { animal }
+>Animal : Animal
+>animal : any
+
+interface Dog extends Animal { dog }
+>Dog : Dog
+>Animal : Animal
+>dog : any
+
+interface Cat extends Animal { cat }
+>Cat : Cat
+>Animal : Animal
+>cat : any
+
+function foo1(bar: { a:number }[]): Dog;
+>foo1 : { (bar: { a: number; }[]): Dog; (bar: { a: string; }[]): Animal; }
+>bar : { a: number; }[]
+>a : number
+>Dog : Dog
+
+function foo1(bar: { a:string }[]): Animal;
+>foo1 : { (bar: { a: number; }[]): Dog; (bar: { a: string; }[]): Animal; }
+>bar : { a: string; }[]
+>a : string
+>Animal : Animal
+
+function foo1([x]: { a:number | string }[]): Dog {
+>foo1 : { (bar: { a: number; }[]): Dog; (bar: { a: string; }[]): Animal; }
+>x : { a: number | string; }
+>a : number | string
+>Dog : Dog
+
+    return undefined;
+>undefined : undefined
+}
+
+function foo2(bar: { a:number }[]): Cat;
+>foo2 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Cat | Dog; }
+>bar : { a: number; }[]
+>a : number
+>Cat : Cat
+
+function foo2(bar: { a:string }[]): Cat | Dog;
+>foo2 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Cat | Dog; }
+>bar : { a: string; }[]
+>a : string
+>Cat : Cat
+>Dog : Dog
+
+function foo2([x]: { a:number | string }[]): Cat {
+>foo2 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Cat | Dog; }
+>x : { a: number | string; }
+>a : number | string
+>Cat : Cat
+
+    return undefined;
+>undefined : undefined
+}
+
+
+var x1 = foo1([{a: "str"}]);
+>x1 : Animal
+>foo1([{a: "str"}]) : Animal
+>foo1 : { (bar: { a: number; }[]): Dog; (bar: { a: string; }[]): Animal; }
+>[{a: "str"}] : { a: string; }[]
+>{a: "str"} : { a: string; }
+>a : string
+>"str" : string
+
+var y1 = foo1([{a: 100}]);
+>y1 : Dog
+>foo1([{a: 100}]) : Dog
+>foo1 : { (bar: { a: number; }[]): Dog; (bar: { a: string; }[]): Animal; }
+>[{a: 100}] : { a: number; }[]
+>{a: 100} : { a: number; }
+>a : number
+>100 : number
+
+var x2 = foo2([{a: "str"}]);
+>x2 : Cat | Dog
+>foo2([{a: "str"}]) : Cat | Dog
+>foo2 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Cat | Dog; }
+>[{a: "str"}] : { a: string; }[]
+>{a: "str"} : { a: string; }
+>a : string
+>"str" : string
+
+var y2 = foo2([{a: 100}]);
+>y2 : Cat
+>foo2([{a: 100}]) : Cat
+>foo2 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Cat | Dog; }
+>[{a: 100}] : { a: number; }[]
+>{a: 100} : { a: number; }
+>a : number
+>100 : number
+
--- a/tests/baselines/reference/functionOverloads45.js
+++ b/tests/baselines/reference/functionOverloads45.js
@ -0,0 +1,37 @@
+//// [functionOverloads45.ts]
+interface Animal { animal }
+interface Dog extends Animal { dog }
+interface Cat extends Animal { cat }
+
+function foo1(bar: { a:number }[]): Cat;
+function foo1(bar: { a:string }[]): Dog;
+function foo1([x]: { a:number | string }[]): Animal {
+    return undefined;
+}
+
+function foo2(bar: { a:number }[]): Cat;
+function foo2(bar: { a:string }[]): Dog;
+function foo2([x]: { a:number | string }[]): Cat | Dog {
+    return undefined;
+}
+
+
+var x1 = foo1([{a: "str"}]);
+var y1 = foo1([{a: 100}]);
+
+var x2 = foo2([{a: "str"}]);
+var y2 = foo2([{a: 100}]);
+
+//// [functionOverloads45.js]
+function foo1(_a) {
+    var x = _a[0];
+    return undefined;
+}
+function foo2(_a) {
+    var x = _a[0];
+    return undefined;
+}
+var x1 = foo1([{ a: "str" }]);
+var y1 = foo1([{ a: 100 }]);
+var x2 = foo2([{ a: "str" }]);
+var y2 = foo2([{ a: 100 }]);
--- a/tests/baselines/reference/functionOverloads45.symbols
+++ b/tests/baselines/reference/functionOverloads45.symbols
@ -0,0 +1,81 @@
+=== tests/cases/compiler/functionOverloads45.ts ===
+interface Animal { animal }
+>Animal : Symbol(Animal, Decl(functionOverloads45.ts, 0, 0))
+>animal : Symbol(animal, Decl(functionOverloads45.ts, 0, 18))
+
+interface Dog extends Animal { dog }
+>Dog : Symbol(Dog, Decl(functionOverloads45.ts, 0, 27))
+>Animal : Symbol(Animal, Decl(functionOverloads45.ts, 0, 0))
+>dog : Symbol(dog, Decl(functionOverloads45.ts, 1, 30))
+
+interface Cat extends Animal { cat }
+>Cat : Symbol(Cat, Decl(functionOverloads45.ts, 1, 36))
+>Animal : Symbol(Animal, Decl(functionOverloads45.ts, 0, 0))
+>cat : Symbol(cat, Decl(functionOverloads45.ts, 2, 30))
+
+function foo1(bar: { a:number }[]): Cat;
+>foo1 : Symbol(foo1, Decl(functionOverloads45.ts, 2, 36), Decl(functionOverloads45.ts, 4, 40), Decl(functionOverloads45.ts, 5, 40))
+>bar : Symbol(bar, Decl(functionOverloads45.ts, 4, 14))
+>a : Symbol(a, Decl(functionOverloads45.ts, 4, 20))
+>Cat : Symbol(Cat, Decl(functionOverloads45.ts, 1, 36))
+
+function foo1(bar: { a:string }[]): Dog;
+>foo1 : Symbol(foo1, Decl(functionOverloads45.ts, 2, 36), Decl(functionOverloads45.ts, 4, 40), Decl(functionOverloads45.ts, 5, 40))
+>bar : Symbol(bar, Decl(functionOverloads45.ts, 5, 14))
+>a : Symbol(a, Decl(functionOverloads45.ts, 5, 20))
+>Dog : Symbol(Dog, Decl(functionOverloads45.ts, 0, 27))
+
+function foo1([x]: { a:number | string }[]): Animal {
+>foo1 : Symbol(foo1, Decl(functionOverloads45.ts, 2, 36), Decl(functionOverloads45.ts, 4, 40), Decl(functionOverloads45.ts, 5, 40))
+>x : Symbol(x, Decl(functionOverloads45.ts, 6, 15))
+>a : Symbol(a, Decl(functionOverloads45.ts, 6, 20))
+>Animal : Symbol(Animal, Decl(functionOverloads45.ts, 0, 0))
+
+    return undefined;
+>undefined : Symbol(undefined)
+}
+
+function foo2(bar: { a:number }[]): Cat;
+>foo2 : Symbol(foo2, Decl(functionOverloads45.ts, 8, 1), Decl(functionOverloads45.ts, 10, 40), Decl(functionOverloads45.ts, 11, 40))
+>bar : Symbol(bar, Decl(functionOverloads45.ts, 10, 14))
+>a : Symbol(a, Decl(functionOverloads45.ts, 10, 20))
+>Cat : Symbol(Cat, Decl(functionOverloads45.ts, 1, 36))
+
+function foo2(bar: { a:string }[]): Dog;
+>foo2 : Symbol(foo2, Decl(functionOverloads45.ts, 8, 1), Decl(functionOverloads45.ts, 10, 40), Decl(functionOverloads45.ts, 11, 40))
+>bar : Symbol(bar, Decl(functionOverloads45.ts, 11, 14))
+>a : Symbol(a, Decl(functionOverloads45.ts, 11, 20))
+>Dog : Symbol(Dog, Decl(functionOverloads45.ts, 0, 27))
+
+function foo2([x]: { a:number | string }[]): Cat | Dog {
+>foo2 : Symbol(foo2, Decl(functionOverloads45.ts, 8, 1), Decl(functionOverloads45.ts, 10, 40), Decl(functionOverloads45.ts, 11, 40))
+>x : Symbol(x, Decl(functionOverloads45.ts, 12, 15))
+>a : Symbol(a, Decl(functionOverloads45.ts, 12, 20))
+>Cat : Symbol(Cat, Decl(functionOverloads45.ts, 1, 36))
+>Dog : Symbol(Dog, Decl(functionOverloads45.ts, 0, 27))
+
+    return undefined;
+>undefined : Symbol(undefined)
+}
+
+
+var x1 = foo1([{a: "str"}]);
+>x1 : Symbol(x1, Decl(functionOverloads45.ts, 17, 3))
+>foo1 : Symbol(foo1, Decl(functionOverloads45.ts, 2, 36), Decl(functionOverloads45.ts, 4, 40), Decl(functionOverloads45.ts, 5, 40))
+>a : Symbol(a, Decl(functionOverloads45.ts, 17, 16))
+
+var y1 = foo1([{a: 100}]);
+>y1 : Symbol(y1, Decl(functionOverloads45.ts, 18, 3))
+>foo1 : Symbol(foo1, Decl(functionOverloads45.ts, 2, 36), Decl(functionOverloads45.ts, 4, 40), Decl(functionOverloads45.ts, 5, 40))
+>a : Symbol(a, Decl(functionOverloads45.ts, 18, 16))
+
+var x2 = foo2([{a: "str"}]);
+>x2 : Symbol(x2, Decl(functionOverloads45.ts, 20, 3))
+>foo2 : Symbol(foo2, Decl(functionOverloads45.ts, 8, 1), Decl(functionOverloads45.ts, 10, 40), Decl(functionOverloads45.ts, 11, 40))
+>a : Symbol(a, Decl(functionOverloads45.ts, 20, 16))
+
+var y2 = foo2([{a: 100}]);
+>y2 : Symbol(y2, Decl(functionOverloads45.ts, 21, 3))
+>foo2 : Symbol(foo2, Decl(functionOverloads45.ts, 8, 1), Decl(functionOverloads45.ts, 10, 40), Decl(functionOverloads45.ts, 11, 40))
+>a : Symbol(a, Decl(functionOverloads45.ts, 21, 16))
+
--- a/tests/baselines/reference/functionOverloads45.types
+++ b/tests/baselines/reference/functionOverloads45.types
@ -0,0 +1,97 @@
+=== tests/cases/compiler/functionOverloads45.ts ===
+interface Animal { animal }
+>Animal : Animal
+>animal : any
+
+interface Dog extends Animal { dog }
+>Dog : Dog
+>Animal : Animal
+>dog : any
+
+interface Cat extends Animal { cat }
+>Cat : Cat
+>Animal : Animal
+>cat : any
+
+function foo1(bar: { a:number }[]): Cat;
+>foo1 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Dog; }
+>bar : { a: number; }[]
+>a : number
+>Cat : Cat
+
+function foo1(bar: { a:string }[]): Dog;
+>foo1 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Dog; }
+>bar : { a: string; }[]
+>a : string
+>Dog : Dog
+
+function foo1([x]: { a:number | string }[]): Animal {
+>foo1 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Dog; }
+>x : { a: number | string; }
+>a : number | string
+>Animal : Animal
+
+    return undefined;
+>undefined : undefined
+}
+
+function foo2(bar: { a:number }[]): Cat;
+>foo2 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Dog; }
+>bar : { a: number; }[]
+>a : number
+>Cat : Cat
+
+function foo2(bar: { a:string }[]): Dog;
+>foo2 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Dog; }
+>bar : { a: string; }[]
+>a : string
+>Dog : Dog
+
+function foo2([x]: { a:number | string }[]): Cat | Dog {
+>foo2 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Dog; }
+>x : { a: number | string; }
+>a : number | string
+>Cat : Cat
+>Dog : Dog
+
+    return undefined;
+>undefined : undefined
+}
+
+
+var x1 = foo1([{a: "str"}]);
+>x1 : Dog
+>foo1([{a: "str"}]) : Dog
+>foo1 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Dog; }
+>[{a: "str"}] : { a: string; }[]
+>{a: "str"} : { a: string; }
+>a : string
+>"str" : string
+
+var y1 = foo1([{a: 100}]);
+>y1 : Cat
+>foo1([{a: 100}]) : Cat
+>foo1 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Dog; }
+>[{a: 100}] : { a: number; }[]
+>{a: 100} : { a: number; }
+>a : number
+>100 : number
+
+var x2 = foo2([{a: "str"}]);
+>x2 : Dog
+>foo2([{a: "str"}]) : Dog
+>foo2 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Dog; }
+>[{a: "str"}] : { a: string; }[]
+>{a: "str"} : { a: string; }
+>a : string
+>"str" : string
+
+var y2 = foo2([{a: 100}]);
+>y2 : Cat
+>foo2([{a: 100}]) : Cat
+>foo2 : { (bar: { a: number; }[]): Cat; (bar: { a: string; }[]): Dog; }
+>[{a: 100}] : { a: number; }[]
+>{a: 100} : { a: number; }
+>a : number
+>100 : number
+
--- a/tests/baselines/reference/overloadOnConstConstraintChecks4.errors.txt
+++ b/tests/baselines/reference/overloadOnConstConstraintChecks4.errors.txt
@ -1,19 +0,0 @@
-tests/cases/compiler/overloadOnConstConstraintChecks4.ts(9,10): error TS2394: Overload signature is not compatible with function implementation.
-
-
-==== tests/cases/compiler/overloadOnConstConstraintChecks4.ts (1 errors) ====
-    class Z { }
-    class A extends Z { private x = 1 }
-    class B extends A {}
-    class C extends A {
-        public foo() { }
-    }
-    function foo(name: 'hi'): B;
-    function foo(name: 'bye'): C;
-    function foo(name: string): A; // error
-             ~~~
-!!! error TS2394: Overload signature is not compatible with function implementation.
-    function foo(name: any): Z {
-        return null;
-    }
-    
--- a/tests/baselines/reference/overloadOnConstConstraintChecks4.js
+++ b/tests/baselines/reference/overloadOnConstConstraintChecks4.js
@ -7,7 +7,7 @@ class C extends A {
 }
 function foo(name: 'hi'): B;
 function foo(name: 'bye'): C;
-function foo(name: string): A; // error
+function foo(name: string): A;
 function foo(name: any): Z {
    return null;
 }
--- a/tests/baselines/reference/overloadOnConstConstraintChecks4.symbols
+++ b/tests/baselines/reference/overloadOnConstConstraintChecks4.symbols
@ -0,0 +1,43 @@
+=== tests/cases/compiler/overloadOnConstConstraintChecks4.ts ===
+class Z { }
+>Z : Symbol(Z, Decl(overloadOnConstConstraintChecks4.ts, 0, 0))
+
+class A extends Z { private x = 1 }
+>A : Symbol(A, Decl(overloadOnConstConstraintChecks4.ts, 0, 11))
+>Z : Symbol(Z, Decl(overloadOnConstConstraintChecks4.ts, 0, 0))
+>x : Symbol(x, Decl(overloadOnConstConstraintChecks4.ts, 1, 19))
+
+class B extends A {}
+>B : Symbol(B, Decl(overloadOnConstConstraintChecks4.ts, 1, 35))
+>A : Symbol(A, Decl(overloadOnConstConstraintChecks4.ts, 0, 11))
+
+class C extends A {
+>C : Symbol(C, Decl(overloadOnConstConstraintChecks4.ts, 2, 20))
+>A : Symbol(A, Decl(overloadOnConstConstraintChecks4.ts, 0, 11))
+
+    public foo() { }
+>foo : Symbol(foo, Decl(overloadOnConstConstraintChecks4.ts, 3, 19))
+}
+function foo(name: 'hi'): B;
+>foo : Symbol(foo, Decl(overloadOnConstConstraintChecks4.ts, 5, 1), Decl(overloadOnConstConstraintChecks4.ts, 6, 28), Decl(overloadOnConstConstraintChecks4.ts, 7, 29), Decl(overloadOnConstConstraintChecks4.ts, 8, 30))
+>name : Symbol(name, Decl(overloadOnConstConstraintChecks4.ts, 6, 13))
+>B : Symbol(B, Decl(overloadOnConstConstraintChecks4.ts, 1, 35))
+
+function foo(name: 'bye'): C;
+>foo : Symbol(foo, Decl(overloadOnConstConstraintChecks4.ts, 5, 1), Decl(overloadOnConstConstraintChecks4.ts, 6, 28), Decl(overloadOnConstConstraintChecks4.ts, 7, 29), Decl(overloadOnConstConstraintChecks4.ts, 8, 30))
+>name : Symbol(name, Decl(overloadOnConstConstraintChecks4.ts, 7, 13))
+>C : Symbol(C, Decl(overloadOnConstConstraintChecks4.ts, 2, 20))
+
+function foo(name: string): A;
+>foo : Symbol(foo, Decl(overloadOnConstConstraintChecks4.ts, 5, 1), Decl(overloadOnConstConstraintChecks4.ts, 6, 28), Decl(overloadOnConstConstraintChecks4.ts, 7, 29), Decl(overloadOnConstConstraintChecks4.ts, 8, 30))
+>name : Symbol(name, Decl(overloadOnConstConstraintChecks4.ts, 8, 13))
+>A : Symbol(A, Decl(overloadOnConstConstraintChecks4.ts, 0, 11))
+
+function foo(name: any): Z {
+>foo : Symbol(foo, Decl(overloadOnConstConstraintChecks4.ts, 5, 1), Decl(overloadOnConstConstraintChecks4.ts, 6, 28), Decl(overloadOnConstConstraintChecks4.ts, 7, 29), Decl(overloadOnConstConstraintChecks4.ts, 8, 30))
+>name : Symbol(name, Decl(overloadOnConstConstraintChecks4.ts, 9, 13))
+>Z : Symbol(Z, Decl(overloadOnConstConstraintChecks4.ts, 0, 0))
+
+    return null;
+}
+
--- a/tests/baselines/reference/overloadOnConstConstraintChecks4.types
+++ b/tests/baselines/reference/overloadOnConstConstraintChecks4.types
@ -0,0 +1,45 @@
+=== tests/cases/compiler/overloadOnConstConstraintChecks4.ts ===
+class Z { }
+>Z : Z
+
+class A extends Z { private x = 1 }
+>A : A
+>Z : Z
+>x : number
+>1 : number
+
+class B extends A {}
+>B : B
+>A : A
+
+class C extends A {
+>C : C
+>A : A
+
+    public foo() { }
+>foo : () => void
+}
+function foo(name: 'hi'): B;
+>foo : { (name: "hi"): B; (name: "bye"): C; (name: string): A; }
+>name : "hi"
+>B : B
+
+function foo(name: 'bye'): C;
+>foo : { (name: "hi"): B; (name: "bye"): C; (name: string): A; }
+>name : "bye"
+>C : C
+
+function foo(name: string): A;
+>foo : { (name: "hi"): B; (name: "bye"): C; (name: string): A; }
+>name : string
+>A : A
+
+function foo(name: any): Z {
+>foo : { (name: "hi"): B; (name: "bye"): C; (name: string): A; }
+>name : any
+>Z : Z
+
+    return null;
+>null : null
+}
+
--- a/tests/baselines/reference/stringLiteralTypesAsTags01.js
+++ b/tests/baselines/reference/stringLiteralTypesAsTags01.js
@ -20,7 +20,7 @@ function hasKind(entity: Entity, kind: "A"): entity is A;
 function hasKind(entity: Entity, kind: "B"): entity is B;
 function hasKind(entity: Entity, kind: Kind): entity is Entity;
 function hasKind(entity: Entity, kind: Kind): boolean {
-    return kind === is;
+    return entity.kind === kind;
 }

 let x: A = {
@ -44,7 +44,7 @@ else {

 //// [stringLiteralTypesAsTags01.js]
 function hasKind(entity, kind) {
-    return kind === is;
+    return entity.kind === kind;
 }
 var x = {
    kind: "A",
--- a/tests/baselines/reference/stringLiteralTypesAsTags01.symbols
+++ b/tests/baselines/reference/stringLiteralTypesAsTags01.symbols
@ -0,0 +1,112 @@
+=== tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags01.ts ===
+
+type Kind = "A" | "B"
+>Kind : Symbol(Kind, Decl(stringLiteralTypesAsTags01.ts, 0, 0))
+
+interface Entity {
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags01.ts, 1, 21))
+
+    kind: Kind;
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags01.ts, 3, 18))
+>Kind : Symbol(Kind, Decl(stringLiteralTypesAsTags01.ts, 0, 0))
+}
+
+interface A extends Entity {
+>A : Symbol(A, Decl(stringLiteralTypesAsTags01.ts, 5, 1))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags01.ts, 1, 21))
+
+    kind: "A";
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags01.ts, 7, 28))
+
+    a: number;
+>a : Symbol(a, Decl(stringLiteralTypesAsTags01.ts, 8, 14))
+}
+
+interface B extends Entity {
+>B : Symbol(B, Decl(stringLiteralTypesAsTags01.ts, 10, 1))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags01.ts, 1, 21))
+
+    kind: "B";
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags01.ts, 12, 28))
+
+    b: string;
+>b : Symbol(b, Decl(stringLiteralTypesAsTags01.ts, 13, 14))
+}
+
+function hasKind(entity: Entity, kind: "A"): entity is A;
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags01.ts, 15, 1), Decl(stringLiteralTypesAsTags01.ts, 17, 57), Decl(stringLiteralTypesAsTags01.ts, 18, 57), Decl(stringLiteralTypesAsTags01.ts, 19, 63))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags01.ts, 17, 17))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags01.ts, 1, 21))
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags01.ts, 17, 32))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags01.ts, 17, 17))
+>A : Symbol(A, Decl(stringLiteralTypesAsTags01.ts, 5, 1))
+
+function hasKind(entity: Entity, kind: "B"): entity is B;
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags01.ts, 15, 1), Decl(stringLiteralTypesAsTags01.ts, 17, 57), Decl(stringLiteralTypesAsTags01.ts, 18, 57), Decl(stringLiteralTypesAsTags01.ts, 19, 63))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags01.ts, 18, 17))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags01.ts, 1, 21))
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags01.ts, 18, 32))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags01.ts, 18, 17))
+>B : Symbol(B, Decl(stringLiteralTypesAsTags01.ts, 10, 1))
+
+function hasKind(entity: Entity, kind: Kind): entity is Entity;
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags01.ts, 15, 1), Decl(stringLiteralTypesAsTags01.ts, 17, 57), Decl(stringLiteralTypesAsTags01.ts, 18, 57), Decl(stringLiteralTypesAsTags01.ts, 19, 63))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags01.ts, 19, 17))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags01.ts, 1, 21))
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags01.ts, 19, 32))
+>Kind : Symbol(Kind, Decl(stringLiteralTypesAsTags01.ts, 0, 0))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags01.ts, 19, 17))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags01.ts, 1, 21))
+
+function hasKind(entity: Entity, kind: Kind): boolean {
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags01.ts, 15, 1), Decl(stringLiteralTypesAsTags01.ts, 17, 57), Decl(stringLiteralTypesAsTags01.ts, 18, 57), Decl(stringLiteralTypesAsTags01.ts, 19, 63))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags01.ts, 20, 17))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags01.ts, 1, 21))
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags01.ts, 20, 32))
+>Kind : Symbol(Kind, Decl(stringLiteralTypesAsTags01.ts, 0, 0))
+
+    return entity.kind === kind;
+>entity.kind : Symbol(Entity.kind, Decl(stringLiteralTypesAsTags01.ts, 3, 18))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags01.ts, 20, 17))
+>kind : Symbol(Entity.kind, Decl(stringLiteralTypesAsTags01.ts, 3, 18))
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags01.ts, 20, 32))
+}
+
+let x: A = {
+>x : Symbol(x, Decl(stringLiteralTypesAsTags01.ts, 24, 3))
+>A : Symbol(A, Decl(stringLiteralTypesAsTags01.ts, 5, 1))
+
+    kind: "A",
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags01.ts, 24, 12))
+
+    a: 100,
+>a : Symbol(a, Decl(stringLiteralTypesAsTags01.ts, 25, 14))
+}
+
+if (hasKind(x, "A")) {
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags01.ts, 15, 1), Decl(stringLiteralTypesAsTags01.ts, 17, 57), Decl(stringLiteralTypesAsTags01.ts, 18, 57), Decl(stringLiteralTypesAsTags01.ts, 19, 63))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags01.ts, 24, 3))
+
+    let a = x;
+>a : Symbol(a, Decl(stringLiteralTypesAsTags01.ts, 30, 7))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags01.ts, 24, 3))
+}
+else {
+    let b = x;
+>b : Symbol(b, Decl(stringLiteralTypesAsTags01.ts, 33, 7))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags01.ts, 24, 3))
+}
+
+if (!hasKind(x, "B")) {
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags01.ts, 15, 1), Decl(stringLiteralTypesAsTags01.ts, 17, 57), Decl(stringLiteralTypesAsTags01.ts, 18, 57), Decl(stringLiteralTypesAsTags01.ts, 19, 63))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags01.ts, 24, 3))
+
+    let c = x;
+>c : Symbol(c, Decl(stringLiteralTypesAsTags01.ts, 37, 7))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags01.ts, 24, 3))
+}
+else {
+    let d = x;
+>d : Symbol(d, Decl(stringLiteralTypesAsTags01.ts, 40, 7))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags01.ts, 24, 3))
+}
--- a/tests/baselines/reference/stringLiteralTypesAsTags01.types
+++ b/tests/baselines/reference/stringLiteralTypesAsTags01.types
@ -0,0 +1,121 @@
+=== tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags01.ts ===
+
+type Kind = "A" | "B"
+>Kind : "A" | "B"
+
+interface Entity {
+>Entity : Entity
+
+    kind: Kind;
+>kind : "A" | "B"
+>Kind : "A" | "B"
+}
+
+interface A extends Entity {
+>A : A
+>Entity : Entity
+
+    kind: "A";
+>kind : "A"
+
+    a: number;
+>a : number
+}
+
+interface B extends Entity {
+>B : B
+>Entity : Entity
+
+    kind: "B";
+>kind : "B"
+
+    b: string;
+>b : string
+}
+
+function hasKind(entity: Entity, kind: "A"): entity is A;
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; (entity: Entity, kind: "A" | "B"): entity is Entity; }
+>entity : Entity
+>Entity : Entity
+>kind : "A"
+>entity : any
+>A : A
+
+function hasKind(entity: Entity, kind: "B"): entity is B;
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; (entity: Entity, kind: "A" | "B"): entity is Entity; }
+>entity : Entity
+>Entity : Entity
+>kind : "B"
+>entity : any
+>B : B
+
+function hasKind(entity: Entity, kind: Kind): entity is Entity;
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; (entity: Entity, kind: "A" | "B"): entity is Entity; }
+>entity : Entity
+>Entity : Entity
+>kind : "A" | "B"
+>Kind : "A" | "B"
+>entity : any
+>Entity : Entity
+
+function hasKind(entity: Entity, kind: Kind): boolean {
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; (entity: Entity, kind: "A" | "B"): entity is Entity; }
+>entity : Entity
+>Entity : Entity
+>kind : "A" | "B"
+>Kind : "A" | "B"
+
+    return entity.kind === kind;
+>entity.kind === kind : boolean
+>entity.kind : "A" | "B"
+>entity : Entity
+>kind : "A" | "B"
+>kind : "A" | "B"
+}
+
+let x: A = {
+>x : A
+>A : A
+>{    kind: "A",    a: 100,} : { kind: "A"; a: number; }
+
+    kind: "A",
+>kind : "A"
+>"A" : "A"
+
+    a: 100,
+>a : number
+>100 : number
+}
+
+if (hasKind(x, "A")) {
+>hasKind(x, "A") : entity is A
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; (entity: Entity, kind: "A" | "B"): entity is Entity; }
+>x : A
+>"A" : "A"
+
+    let a = x;
+>a : A
+>x : A
+}
+else {
+    let b = x;
+>b : A
+>x : A
+}
+
+if (!hasKind(x, "B")) {
+>!hasKind(x, "B") : boolean
+>hasKind(x, "B") : entity is B
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; (entity: Entity, kind: "A" | "B"): entity is Entity; }
+>x : A
+>"B" : "B"
+
+    let c = x;
+>c : A
+>x : A
+}
+else {
+    let d = x;
+>d : A
+>x : A
+}
--- a/tests/baselines/reference/stringLiteralTypesAsTags02.errors.txt
+++ b/tests/baselines/reference/stringLiteralTypesAsTags02.errors.txt
@ -1,8 +1,8 @@
-tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags01.ts(20,10): error TS2394: Overload signature is not compatible with function implementation.
-tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags01.ts(22,21): error TS2304: Cannot find name 'is'.
+tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags02.ts(18,10): error TS2382: Specialized overload signature is not assignable to any non-specialized signature.
+tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags02.ts(19,10): error TS2382: Specialized overload signature is not assignable to any non-specialized signature.


-==== tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags01.ts (2 errors) ====
+==== tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags02.ts (2 errors) ====
    
    type Kind = "A" | "B"
    
@ -21,14 +21,13 @@ tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags01.ts(22,21)
    }
    
    function hasKind(entity: Entity, kind: "A"): entity is A;
-    function hasKind(entity: Entity, kind: "B"): entity is B;
-    function hasKind(entity: Entity, kind: Kind): entity is Entity;
             ~~~~~~~
-!!! error TS2394: Overload signature is not compatible with function implementation.
-    function hasKind(entity: Entity, kind: Kind): boolean {
-        return kind === is;
-                        ~~
-!!! error TS2304: Cannot find name 'is'.
+!!! error TS2382: Specialized overload signature is not assignable to any non-specialized signature.
+    function hasKind(entity: Entity, kind: "B"): entity is B;
+             ~~~~~~~
+!!! error TS2382: Specialized overload signature is not assignable to any non-specialized signature.
+    function hasKind(entity: Entity, kind: Kind): entity is (A | B) {
+        return entity.kind === kind;
    }
    
    let x: A = {
--- a/tests/baselines/reference/stringLiteralTypesAsTags02.js
+++ b/tests/baselines/reference/stringLiteralTypesAsTags02.js
@ -0,0 +1,81 @@
+//// [stringLiteralTypesAsTags02.ts]
+
+type Kind = "A" | "B"
+
+interface Entity {
+    kind: Kind;
+}
+
+interface A extends Entity {
+    kind: "A";
+    a: number;
+}
+
+interface B extends Entity {
+    kind: "B";
+    b: string;
+}
+
+function hasKind(entity: Entity, kind: "A"): entity is A;
+function hasKind(entity: Entity, kind: "B"): entity is B;
+function hasKind(entity: Entity, kind: Kind): entity is (A | B) {
+    return entity.kind === kind;
+}
+
+let x: A = {
+    kind: "A",
+    a: 100,
+}
+
+if (hasKind(x, "A")) {
+    let a = x;
+}
+else {
+    let b = x;
+}
+
+if (!hasKind(x, "B")) {
+    let c = x;
+}
+else {
+    let d = x;
+}
+
+//// [stringLiteralTypesAsTags02.js]
+function hasKind(entity, kind) {
+    return entity.kind === kind;
+}
+var x = {
+    kind: "A",
+    a: 100
+};
+if (hasKind(x, "A")) {
+    var a = x;
+}
+else {
+    var b = x;
+}
+if (!hasKind(x, "B")) {
+    var c = x;
+}
+else {
+    var d = x;
+}
+
+
+//// [stringLiteralTypesAsTags02.d.ts]
+declare type Kind = "A" | "B";
+interface Entity {
+    kind: Kind;
+}
+interface A extends Entity {
+    kind: "A";
+    a: number;
+}
+interface B extends Entity {
+    kind: "B";
+    b: string;
+}
+declare function hasKind(entity: Entity, kind: "A"): entity is A;
+declare function hasKind(entity: Entity, kind: "B"): entity is B;
+declare let x: A;
--- a/tests/baselines/reference/stringLiteralTypesAsTags03.js
+++ b/tests/baselines/reference/stringLiteralTypesAsTags03.js
@ -0,0 +1,85 @@
+//// [stringLiteralTypesAsTags03.ts]
+
+type Kind = "A" | "B"
+
+interface Entity {
+    kind: Kind;
+}
+
+interface A extends Entity {
+    kind: "A";
+    a: number;
+}
+
+interface B extends Entity {
+    kind: "B";
+    b: string;
+}
+
+// Currently (2015-12-14), we write '"A" | "A"' and '"B" | "B"' to avoid
+// interpreting respective overloads as "specialized" signatures.
+// That way, we can avoid the need to look for a compatible overload
+// signature and simply check compatibility with the implementation.
+function hasKind(entity: Entity, kind: "A" | "A"): entity is A;
+function hasKind(entity: Entity, kind: "B" | "B"): entity is B;
+function hasKind(entity: Entity, kind: Kind): entity is Entity {
+    return entity.kind === kind;
+}
+
+let x: A = {
+    kind: "A",
+    a: 100,
+}
+
+if (hasKind(x, "A")) {
+    let a = x;
+}
+else {
+    let b = x;
+}
+
+if (!hasKind(x, "B")) {
+    let c = x;
+}
+else {
+    let d = x;
+}
+
+//// [stringLiteralTypesAsTags03.js]
+function hasKind(entity, kind) {
+    return entity.kind === kind;
+}
+var x = {
+    kind: "A",
+    a: 100
+};
+if (hasKind(x, "A")) {
+    var a = x;
+}
+else {
+    var b = x;
+}
+if (!hasKind(x, "B")) {
+    var c = x;
+}
+else {
+    var d = x;
+}
+
+
+//// [stringLiteralTypesAsTags03.d.ts]
+declare type Kind = "A" | "B";
+interface Entity {
+    kind: Kind;
+}
+interface A extends Entity {
+    kind: "A";
+    a: number;
+}
+interface B extends Entity {
+    kind: "B";
+    b: string;
+}
+declare function hasKind(entity: Entity, kind: "A" | "A"): entity is A;
+declare function hasKind(entity: Entity, kind: "B" | "B"): entity is B;
+declare let x: A;
--- a/tests/baselines/reference/stringLiteralTypesAsTags03.symbols
+++ b/tests/baselines/reference/stringLiteralTypesAsTags03.symbols
@ -0,0 +1,109 @@
+=== tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags03.ts ===
+
+type Kind = "A" | "B"
+>Kind : Symbol(Kind, Decl(stringLiteralTypesAsTags03.ts, 0, 0))
+
+interface Entity {
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags03.ts, 1, 21))
+
+    kind: Kind;
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags03.ts, 3, 18))
+>Kind : Symbol(Kind, Decl(stringLiteralTypesAsTags03.ts, 0, 0))
+}
+
+interface A extends Entity {
+>A : Symbol(A, Decl(stringLiteralTypesAsTags03.ts, 5, 1))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags03.ts, 1, 21))
+
+    kind: "A";
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags03.ts, 7, 28))
+
+    a: number;
+>a : Symbol(a, Decl(stringLiteralTypesAsTags03.ts, 8, 14))
+}
+
+interface B extends Entity {
+>B : Symbol(B, Decl(stringLiteralTypesAsTags03.ts, 10, 1))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags03.ts, 1, 21))
+
+    kind: "B";
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags03.ts, 12, 28))
+
+    b: string;
+>b : Symbol(b, Decl(stringLiteralTypesAsTags03.ts, 13, 14))
+}
+
+// Currently (2015-12-14), we write '"A" | "A"' and '"B" | "B"' to avoid
+// interpreting respective overloads as "specialized" signatures.
+// That way, we can avoid the need to look for a compatible overload
+// signature and simply check compatibility with the implementation.
+function hasKind(entity: Entity, kind: "A" | "A"): entity is A;
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags03.ts, 15, 1), Decl(stringLiteralTypesAsTags03.ts, 21, 63), Decl(stringLiteralTypesAsTags03.ts, 22, 63))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags03.ts, 21, 17))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags03.ts, 1, 21))
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags03.ts, 21, 32))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags03.ts, 21, 17))
+>A : Symbol(A, Decl(stringLiteralTypesAsTags03.ts, 5, 1))
+
+function hasKind(entity: Entity, kind: "B" | "B"): entity is B;
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags03.ts, 15, 1), Decl(stringLiteralTypesAsTags03.ts, 21, 63), Decl(stringLiteralTypesAsTags03.ts, 22, 63))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags03.ts, 22, 17))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags03.ts, 1, 21))
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags03.ts, 22, 32))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags03.ts, 22, 17))
+>B : Symbol(B, Decl(stringLiteralTypesAsTags03.ts, 10, 1))
+
+function hasKind(entity: Entity, kind: Kind): entity is Entity {
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags03.ts, 15, 1), Decl(stringLiteralTypesAsTags03.ts, 21, 63), Decl(stringLiteralTypesAsTags03.ts, 22, 63))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags03.ts, 23, 17))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags03.ts, 1, 21))
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags03.ts, 23, 32))
+>Kind : Symbol(Kind, Decl(stringLiteralTypesAsTags03.ts, 0, 0))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags03.ts, 23, 17))
+>Entity : Symbol(Entity, Decl(stringLiteralTypesAsTags03.ts, 1, 21))
+
+    return entity.kind === kind;
+>entity.kind : Symbol(Entity.kind, Decl(stringLiteralTypesAsTags03.ts, 3, 18))
+>entity : Symbol(entity, Decl(stringLiteralTypesAsTags03.ts, 23, 17))
+>kind : Symbol(Entity.kind, Decl(stringLiteralTypesAsTags03.ts, 3, 18))
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags03.ts, 23, 32))
+}
+
+let x: A = {
+>x : Symbol(x, Decl(stringLiteralTypesAsTags03.ts, 27, 3))
+>A : Symbol(A, Decl(stringLiteralTypesAsTags03.ts, 5, 1))
+
+    kind: "A",
+>kind : Symbol(kind, Decl(stringLiteralTypesAsTags03.ts, 27, 12))
+
+    a: 100,
+>a : Symbol(a, Decl(stringLiteralTypesAsTags03.ts, 28, 14))
+}
+
+if (hasKind(x, "A")) {
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags03.ts, 15, 1), Decl(stringLiteralTypesAsTags03.ts, 21, 63), Decl(stringLiteralTypesAsTags03.ts, 22, 63))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags03.ts, 27, 3))
+
+    let a = x;
+>a : Symbol(a, Decl(stringLiteralTypesAsTags03.ts, 33, 7))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags03.ts, 27, 3))
+}
+else {
+    let b = x;
+>b : Symbol(b, Decl(stringLiteralTypesAsTags03.ts, 36, 7))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags03.ts, 27, 3))
+}
+
+if (!hasKind(x, "B")) {
+>hasKind : Symbol(hasKind, Decl(stringLiteralTypesAsTags03.ts, 15, 1), Decl(stringLiteralTypesAsTags03.ts, 21, 63), Decl(stringLiteralTypesAsTags03.ts, 22, 63))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags03.ts, 27, 3))
+
+    let c = x;
+>c : Symbol(c, Decl(stringLiteralTypesAsTags03.ts, 40, 7))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags03.ts, 27, 3))
+}
+else {
+    let d = x;
+>d : Symbol(d, Decl(stringLiteralTypesAsTags03.ts, 43, 7))
+>x : Symbol(x, Decl(stringLiteralTypesAsTags03.ts, 27, 3))
+}
--- a/tests/baselines/reference/stringLiteralTypesAsTags03.types
+++ b/tests/baselines/reference/stringLiteralTypesAsTags03.types
@ -0,0 +1,118 @@
+=== tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags03.ts ===
+
+type Kind = "A" | "B"
+>Kind : "A" | "B"
+
+interface Entity {
+>Entity : Entity
+
+    kind: Kind;
+>kind : "A" | "B"
+>Kind : "A" | "B"
+}
+
+interface A extends Entity {
+>A : A
+>Entity : Entity
+
+    kind: "A";
+>kind : "A"
+
+    a: number;
+>a : number
+}
+
+interface B extends Entity {
+>B : B
+>Entity : Entity
+
+    kind: "B";
+>kind : "B"
+
+    b: string;
+>b : string
+}
+
+// Currently (2015-12-14), we write '"A" | "A"' and '"B" | "B"' to avoid
+// interpreting respective overloads as "specialized" signatures.
+// That way, we can avoid the need to look for a compatible overload
+// signature and simply check compatibility with the implementation.
+function hasKind(entity: Entity, kind: "A" | "A"): entity is A;
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; }
+>entity : Entity
+>Entity : Entity
+>kind : "A"
+>entity : any
+>A : A
+
+function hasKind(entity: Entity, kind: "B" | "B"): entity is B;
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; }
+>entity : Entity
+>Entity : Entity
+>kind : "B"
+>entity : any
+>B : B
+
+function hasKind(entity: Entity, kind: Kind): entity is Entity {
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; }
+>entity : Entity
+>Entity : Entity
+>kind : "A" | "B"
+>Kind : "A" | "B"
+>entity : any
+>Entity : Entity
+
+    return entity.kind === kind;
+>entity.kind === kind : boolean
+>entity.kind : "A" | "B"
+>entity : Entity
+>kind : "A" | "B"
+>kind : "A" | "B"
+}
+
+let x: A = {
+>x : A
+>A : A
+>{    kind: "A",    a: 100,} : { kind: "A"; a: number; }
+
+    kind: "A",
+>kind : "A"
+>"A" : "A"
+
+    a: 100,
+>a : number
+>100 : number
+}
+
+if (hasKind(x, "A")) {
+>hasKind(x, "A") : entity is A
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; }
+>x : A
+>"A" : "A"
+
+    let a = x;
+>a : A
+>x : A
+}
+else {
+    let b = x;
+>b : A
+>x : A
+}
+
+if (!hasKind(x, "B")) {
+>!hasKind(x, "B") : boolean
+>hasKind(x, "B") : entity is B
+>hasKind : { (entity: Entity, kind: "A"): entity is A; (entity: Entity, kind: "B"): entity is B; }
+>x : A
+>"B" : "B"
+
+    let c = x;
+>c : A
+>x : A
+}
+else {
+    let d = x;
+>d : A
+>x : A
+}
--- a/tests/baselines/reference/stringLiteralTypesOverloads01.errors.txt
+++ b/tests/baselines/reference/stringLiteralTypesOverloads01.errors.txt
@ -1,59 +0,0 @@
-tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloads01.ts(11,10): error TS2354: No best common type exists among return expressions.
-
-
-==== tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloads01.ts (1 errors) ====
-    
-    type PrimitiveName = 'string' | 'number' | 'boolean';
-    
-    function getFalsyPrimitive(x: "string"): string;
-    function getFalsyPrimitive(x: "number"): number;
-    function getFalsyPrimitive(x: "boolean"): boolean;
-    function getFalsyPrimitive(x: "boolean" | "string"): boolean | string;
-    function getFalsyPrimitive(x: "boolean" | "number"): boolean | number;
-    function getFalsyPrimitive(x: "number" | "string"): number | string;
-    function getFalsyPrimitive(x: "number" | "string" | "boolean"): number | string | boolean;
-    function getFalsyPrimitive(x: PrimitiveName) {
-             ~~~~~~~~~~~~~~~~~
-!!! error TS2354: No best common type exists among return expressions.
-        if (x === "string") {
-            return "";
-        }
-        if (x === "number") {
-            return 0;
-        }
-        if (x === "boolean") {
-            return false;
-        }
-    
-        // Should be unreachable.
-        throw "Invalid value";
-    }
-    
-    namespace Consts1 {
-        const EMPTY_STRING = getFalsyPrimitive("string");
-        const ZERO = getFalsyPrimitive('number');
-        const FALSE = getFalsyPrimitive("boolean");
-    }
-    
-    const string: "string" = "string"
-    const number: "number" = "number"
-    const boolean: "boolean" = "boolean"
-    
-    const stringOrNumber = string || number;
-    const stringOrBoolean = string || boolean;
-    const booleanOrNumber = number || boolean;
-    const stringOrBooleanOrNumber = stringOrBoolean || number;
-    
-    namespace Consts2 {
-        const EMPTY_STRING = getFalsyPrimitive(string);
-        const ZERO = getFalsyPrimitive(number);
-        const FALSE = getFalsyPrimitive(boolean);
-    
-        const a = getFalsyPrimitive(stringOrNumber);
-        const b = getFalsyPrimitive(stringOrBoolean);
-        const c = getFalsyPrimitive(booleanOrNumber);
-        const d = getFalsyPrimitive(stringOrBooleanOrNumber);
-    }
-    
-    
-    
--- a/tests/baselines/reference/stringLiteralTypesOverloads01.js
+++ b/tests/baselines/reference/stringLiteralTypesOverloads01.js
@ -9,7 +9,7 @@ function getFalsyPrimitive(x: "boolean" | "string"): boolean | string;
 function getFalsyPrimitive(x: "boolean" | "number"): boolean | number;
 function getFalsyPrimitive(x: "number" | "string"): number | string;
 function getFalsyPrimitive(x: "number" | "string" | "boolean"): number | string | boolean;
-function getFalsyPrimitive(x: PrimitiveName) {
+function getFalsyPrimitive(x: PrimitiveName): number | string | boolean {
    if (x === "string") {
        return "";
    }
--- a/tests/baselines/reference/stringLiteralTypesOverloads01.symbols
+++ b/tests/baselines/reference/stringLiteralTypesOverloads01.symbols
@ -0,0 +1,144 @@
+=== tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloads01.ts ===
+
+type PrimitiveName = 'string' | 'number' | 'boolean';
+>PrimitiveName : Symbol(PrimitiveName, Decl(stringLiteralTypesOverloads01.ts, 0, 0))
+
+function getFalsyPrimitive(x: "string"): string;
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 3, 27))
+
+function getFalsyPrimitive(x: "number"): number;
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 4, 27))
+
+function getFalsyPrimitive(x: "boolean"): boolean;
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 5, 27))
+
+function getFalsyPrimitive(x: "boolean" | "string"): boolean | string;
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 6, 27))
+
+function getFalsyPrimitive(x: "boolean" | "number"): boolean | number;
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 7, 27))
+
+function getFalsyPrimitive(x: "number" | "string"): number | string;
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 8, 27))
+
+function getFalsyPrimitive(x: "number" | "string" | "boolean"): number | string | boolean;
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 9, 27))
+
+function getFalsyPrimitive(x: PrimitiveName): number | string | boolean {
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 10, 27))
+>PrimitiveName : Symbol(PrimitiveName, Decl(stringLiteralTypesOverloads01.ts, 0, 0))
+
+    if (x === "string") {
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 10, 27))
+
+        return "";
+    }
+    if (x === "number") {
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 10, 27))
+
+        return 0;
+    }
+    if (x === "boolean") {
+>x : Symbol(x, Decl(stringLiteralTypesOverloads01.ts, 10, 27))
+
+        return false;
+    }
+
+    // Should be unreachable.
+    throw "Invalid value";
+}
+
+namespace Consts1 {
+>Consts1 : Symbol(Consts1, Decl(stringLiteralTypesOverloads01.ts, 23, 1))
+
+    const EMPTY_STRING = getFalsyPrimitive("string");
+>EMPTY_STRING : Symbol(EMPTY_STRING, Decl(stringLiteralTypesOverloads01.ts, 26, 9))
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+
+    const ZERO = getFalsyPrimitive('number');
+>ZERO : Symbol(ZERO, Decl(stringLiteralTypesOverloads01.ts, 27, 9))
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+
+    const FALSE = getFalsyPrimitive("boolean");
+>FALSE : Symbol(FALSE, Decl(stringLiteralTypesOverloads01.ts, 28, 9))
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+}
+
+const string: "string" = "string"
+>string : Symbol(string, Decl(stringLiteralTypesOverloads01.ts, 31, 5))
+
+const number: "number" = "number"
+>number : Symbol(number, Decl(stringLiteralTypesOverloads01.ts, 32, 5))
+
+const boolean: "boolean" = "boolean"
+>boolean : Symbol(boolean, Decl(stringLiteralTypesOverloads01.ts, 33, 5))
+
+const stringOrNumber = string || number;
+>stringOrNumber : Symbol(stringOrNumber, Decl(stringLiteralTypesOverloads01.ts, 35, 5))
+>string : Symbol(string, Decl(stringLiteralTypesOverloads01.ts, 31, 5))
+>number : Symbol(number, Decl(stringLiteralTypesOverloads01.ts, 32, 5))
+
+const stringOrBoolean = string || boolean;
+>stringOrBoolean : Symbol(stringOrBoolean, Decl(stringLiteralTypesOverloads01.ts, 36, 5))
+>string : Symbol(string, Decl(stringLiteralTypesOverloads01.ts, 31, 5))
+>boolean : Symbol(boolean, Decl(stringLiteralTypesOverloads01.ts, 33, 5))
+
+const booleanOrNumber = number || boolean;
+>booleanOrNumber : Symbol(booleanOrNumber, Decl(stringLiteralTypesOverloads01.ts, 37, 5))
+>number : Symbol(number, Decl(stringLiteralTypesOverloads01.ts, 32, 5))
+>boolean : Symbol(boolean, Decl(stringLiteralTypesOverloads01.ts, 33, 5))
+
+const stringOrBooleanOrNumber = stringOrBoolean || number;
+>stringOrBooleanOrNumber : Symbol(stringOrBooleanOrNumber, Decl(stringLiteralTypesOverloads01.ts, 38, 5))
+>stringOrBoolean : Symbol(stringOrBoolean, Decl(stringLiteralTypesOverloads01.ts, 36, 5))
+>number : Symbol(number, Decl(stringLiteralTypesOverloads01.ts, 32, 5))
+
+namespace Consts2 {
+>Consts2 : Symbol(Consts2, Decl(stringLiteralTypesOverloads01.ts, 38, 58))
+
+    const EMPTY_STRING = getFalsyPrimitive(string);
+>EMPTY_STRING : Symbol(EMPTY_STRING, Decl(stringLiteralTypesOverloads01.ts, 41, 9))
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>string : Symbol(string, Decl(stringLiteralTypesOverloads01.ts, 31, 5))
+
+    const ZERO = getFalsyPrimitive(number);
+>ZERO : Symbol(ZERO, Decl(stringLiteralTypesOverloads01.ts, 42, 9))
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>number : Symbol(number, Decl(stringLiteralTypesOverloads01.ts, 32, 5))
+
+    const FALSE = getFalsyPrimitive(boolean);
+>FALSE : Symbol(FALSE, Decl(stringLiteralTypesOverloads01.ts, 43, 9))
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>boolean : Symbol(boolean, Decl(stringLiteralTypesOverloads01.ts, 33, 5))
+
+    const a = getFalsyPrimitive(stringOrNumber);
+>a : Symbol(a, Decl(stringLiteralTypesOverloads01.ts, 45, 9))
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>stringOrNumber : Symbol(stringOrNumber, Decl(stringLiteralTypesOverloads01.ts, 35, 5))
+
+    const b = getFalsyPrimitive(stringOrBoolean);
+>b : Symbol(b, Decl(stringLiteralTypesOverloads01.ts, 46, 9))
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>stringOrBoolean : Symbol(stringOrBoolean, Decl(stringLiteralTypesOverloads01.ts, 36, 5))
+
+    const c = getFalsyPrimitive(booleanOrNumber);
+>c : Symbol(c, Decl(stringLiteralTypesOverloads01.ts, 47, 9))
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>booleanOrNumber : Symbol(booleanOrNumber, Decl(stringLiteralTypesOverloads01.ts, 37, 5))
+
+    const d = getFalsyPrimitive(stringOrBooleanOrNumber);
+>d : Symbol(d, Decl(stringLiteralTypesOverloads01.ts, 48, 9))
+>getFalsyPrimitive : Symbol(getFalsyPrimitive, Decl(stringLiteralTypesOverloads01.ts, 1, 53), Decl(stringLiteralTypesOverloads01.ts, 3, 48), Decl(stringLiteralTypesOverloads01.ts, 4, 48), Decl(stringLiteralTypesOverloads01.ts, 5, 50), Decl(stringLiteralTypesOverloads01.ts, 6, 70), Decl(stringLiteralTypesOverloads01.ts, 7, 70), Decl(stringLiteralTypesOverloads01.ts, 8, 68), Decl(stringLiteralTypesOverloads01.ts, 9, 90))
+>stringOrBooleanOrNumber : Symbol(stringOrBooleanOrNumber, Decl(stringLiteralTypesOverloads01.ts, 38, 5))
+}
+
+
+
--- a/tests/baselines/reference/stringLiteralTypesOverloads01.types
+++ b/tests/baselines/reference/stringLiteralTypesOverloads01.types
@ -0,0 +1,174 @@
+=== tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloads01.ts ===
+
+type PrimitiveName = 'string' | 'number' | 'boolean';
+>PrimitiveName : "string" | "number" | "boolean"
+
+function getFalsyPrimitive(x: "string"): string;
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>x : "string"
+
+function getFalsyPrimitive(x: "number"): number;
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>x : "number"
+
+function getFalsyPrimitive(x: "boolean"): boolean;
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>x : "boolean"
+
+function getFalsyPrimitive(x: "boolean" | "string"): boolean | string;
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>x : "boolean" | "string"
+
+function getFalsyPrimitive(x: "boolean" | "number"): boolean | number;
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>x : "boolean" | "number"
+
+function getFalsyPrimitive(x: "number" | "string"): number | string;
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>x : "number" | "string"
+
+function getFalsyPrimitive(x: "number" | "string" | "boolean"): number | string | boolean;
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>x : "number" | "string" | "boolean"
+
+function getFalsyPrimitive(x: PrimitiveName): number | string | boolean {
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>x : "string" | "number" | "boolean"
+>PrimitiveName : "string" | "number" | "boolean"
+
+    if (x === "string") {
+>x === "string" : boolean
+>x : "string" | "number" | "boolean"
+>"string" : string
+
+        return "";
+>"" : string
+    }
+    if (x === "number") {
+>x === "number" : boolean
+>x : "string" | "number" | "boolean"
+>"number" : string
+
+        return 0;
+>0 : number
+    }
+    if (x === "boolean") {
+>x === "boolean" : boolean
+>x : "string" | "number" | "boolean"
+>"boolean" : string
+
+        return false;
+>false : boolean
+    }
+
+    // Should be unreachable.
+    throw "Invalid value";
+>"Invalid value" : string
+}
+
+namespace Consts1 {
+>Consts1 : typeof Consts1
+
+    const EMPTY_STRING = getFalsyPrimitive("string");
+>EMPTY_STRING : string
+>getFalsyPrimitive("string") : string
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>"string" : "string"
+
+    const ZERO = getFalsyPrimitive('number');
+>ZERO : number
+>getFalsyPrimitive('number') : number
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>'number' : "number"
+
+    const FALSE = getFalsyPrimitive("boolean");
+>FALSE : boolean
+>getFalsyPrimitive("boolean") : boolean
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>"boolean" : "boolean"
+}
+
+const string: "string" = "string"
+>string : "string"
+>"string" : "string"
+
+const number: "number" = "number"
+>number : "number"
+>"number" : "number"
+
+const boolean: "boolean" = "boolean"
+>boolean : "boolean"
+>"boolean" : "boolean"
+
+const stringOrNumber = string || number;
+>stringOrNumber : "string" | "number"
+>string || number : "string" | "number"
+>string : "string"
+>number : "number"
+
+const stringOrBoolean = string || boolean;
+>stringOrBoolean : "string" | "boolean"
+>string || boolean : "string" | "boolean"
+>string : "string"
+>boolean : "boolean"
+
+const booleanOrNumber = number || boolean;
+>booleanOrNumber : "number" | "boolean"
+>number || boolean : "number" | "boolean"
+>number : "number"
+>boolean : "boolean"
+
+const stringOrBooleanOrNumber = stringOrBoolean || number;
+>stringOrBooleanOrNumber : "string" | "boolean" | "number"
+>stringOrBoolean || number : "string" | "boolean" | "number"
+>stringOrBoolean : "string" | "boolean"
+>number : "number"
+
+namespace Consts2 {
+>Consts2 : typeof Consts2
+
+    const EMPTY_STRING = getFalsyPrimitive(string);
+>EMPTY_STRING : string
+>getFalsyPrimitive(string) : string
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>string : "string"
+
+    const ZERO = getFalsyPrimitive(number);
+>ZERO : number
+>getFalsyPrimitive(number) : number
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>number : "number"
+
+    const FALSE = getFalsyPrimitive(boolean);
+>FALSE : boolean
+>getFalsyPrimitive(boolean) : boolean
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>boolean : "boolean"
+
+    const a = getFalsyPrimitive(stringOrNumber);
+>a : number | string
+>getFalsyPrimitive(stringOrNumber) : number | string
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>stringOrNumber : "string" | "number"
+
+    const b = getFalsyPrimitive(stringOrBoolean);
+>b : boolean | string
+>getFalsyPrimitive(stringOrBoolean) : boolean | string
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>stringOrBoolean : "string" | "boolean"
+
+    const c = getFalsyPrimitive(booleanOrNumber);
+>c : boolean | number
+>getFalsyPrimitive(booleanOrNumber) : boolean | number
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>booleanOrNumber : "number" | "boolean"
+
+    const d = getFalsyPrimitive(stringOrBooleanOrNumber);
+>d : number | string | boolean
+>getFalsyPrimitive(stringOrBooleanOrNumber) : number | string | boolean
+>getFalsyPrimitive : { (x: "string"): string; (x: "number"): number; (x: "boolean"): boolean; (x: "boolean" | "string"): boolean | string; (x: "boolean" | "number"): boolean | number; (x: "number" | "string"): number | string; (x: "number" | "string" | "boolean"): number | string | boolean; }
+>stringOrBooleanOrNumber : "string" | "boolean" | "number"
+}
+
+
+
--- a/tests/baselines/reference/tsxAttributeResolution11.errors.txt
+++ b/tests/baselines/reference/tsxAttributeResolution11.errors.txt
@ -0,0 +1,33 @@
+tests/cases/conformance/jsx/file.tsx(11,22): error TS2339: Property 'bar' does not exist on type 'IntrinsicAttributes & { ref?: string; }'.
+
+
+==== tests/cases/conformance/jsx/react.d.ts (0 errors) ====
+    
+    declare module JSX {
+    	interface Element { }
+    	interface IntrinsicElements {
+    	}
+    	interface ElementAttributesProperty {
+    		props;
+    	}
+    	interface IntrinsicAttributes {
+    		ref?: string;
+    	}
+    }
+    
+==== tests/cases/conformance/jsx/file.tsx (1 errors) ====
+    class MyComponent {  
+      render() {
+      }
+    
+      props: {
+    	  ref?: string;
+      }
+    }
+    
+    // Should be an OK
+    var x = <MyComponent bar='world' />;
+                         ~~~
+!!! error TS2339: Property 'bar' does not exist on type 'IntrinsicAttributes & { ref?: string; }'.
+    
+    
--- a/tests/baselines/reference/tsxAttributeResolution11.js
+++ b/tests/baselines/reference/tsxAttributeResolution11.js
@ -0,0 +1,41 @@
+//// [tests/cases/conformance/jsx/tsxAttributeResolution11.tsx] ////
+
+//// [react.d.ts]
+
+declare module JSX {
+	interface Element { }
+	interface IntrinsicElements {
+	}
+	interface ElementAttributesProperty {
+		props;
+	}
+	interface IntrinsicAttributes {
+		ref?: string;
+	}
+}
+
+//// [file.tsx]
+class MyComponent {  
+  render() {
+  }
+
+  props: {
+	  ref?: string;
+  }
+}
+
+// Should be an OK
+var x = <MyComponent bar='world' />;
+
+
+
+//// [file.jsx]
+var MyComponent = (function () {
+    function MyComponent() {
+    }
+    MyComponent.prototype.render = function () {
+    };
+    return MyComponent;
+}());
+// Should be an OK
+var x = <MyComponent bar='world'/>;
--- a/tests/cases/compiler/functionOverloads43.ts
+++ b/tests/cases/compiler/functionOverloads43.ts
@ -0,0 +1,12 @@
+function foo(bar: { a:number }[]): number;
+function foo(bar: { a:string }[]): string;
+function foo([x]: { a:number | string }[]): string | number {
+    if (x) {
+        return x.a;
+    }
+    
+    return undefined;
+}
+
+var x = foo([{a: "str"}]);
+var y = foo([{a: 100}]);
--- a/tests/cases/compiler/functionOverloads44.ts
+++ b/tests/cases/compiler/functionOverloads44.ts
@ -0,0 +1,22 @@
+interface Animal { animal }
+interface Dog extends Animal { dog }
+interface Cat extends Animal { cat }
+
+function foo1(bar: { a:number }[]): Dog;
+function foo1(bar: { a:string }[]): Animal;
+function foo1([x]: { a:number | string }[]): Dog {
+    return undefined;
+}
+
+function foo2(bar: { a:number }[]): Cat;
+function foo2(bar: { a:string }[]): Cat | Dog;
+function foo2([x]: { a:number | string }[]): Cat {
+    return undefined;
+}
+
+
+var x1 = foo1([{a: "str"}]);
+var y1 = foo1([{a: 100}]);
+
+var x2 = foo2([{a: "str"}]);
+var y2 = foo2([{a: 100}]);
--- a/tests/cases/compiler/functionOverloads45.ts
+++ b/tests/cases/compiler/functionOverloads45.ts
@ -0,0 +1,22 @@
+interface Animal { animal }
+interface Dog extends Animal { dog }
+interface Cat extends Animal { cat }
+
+function foo1(bar: { a:number }[]): Cat;
+function foo1(bar: { a:string }[]): Dog;
+function foo1([x]: { a:number | string }[]): Animal {
+    return undefined;
+}
+
+function foo2(bar: { a:number }[]): Cat;
+function foo2(bar: { a:string }[]): Dog;
+function foo2([x]: { a:number | string }[]): Cat | Dog {
+    return undefined;
+}
+
+
+var x1 = foo1([{a: "str"}]);
+var y1 = foo1([{a: 100}]);
+
+var x2 = foo2([{a: "str"}]);
+var y2 = foo2([{a: 100}]);
--- a/tests/cases/compiler/overloadOnConstConstraintChecks4.ts
+++ b/tests/cases/compiler/overloadOnConstConstraintChecks4.ts
@ -6,7 +6,7 @@ class C extends A {
 }
 function foo(name: 'hi'): B;
 function foo(name: 'bye'): C;
-function foo(name: string): A; // error
+function foo(name: string): A;
 function foo(name: any): Z {
    return null;
 }
--- a/tests/cases/conformance/functions/conformanceFunctionOverloads.ts
+++ b/tests/cases/conformance/functions/conformanceFunctionOverloads.ts
@ -1,22 +0,0 @@
-// Function overloads do not emit code
-
-// Function overload signature with optional parameter
-
-// Function overload signature with optional parameter
-
-// Function overloads with generic and non-generic overloads
-
-// Function overloads whose only difference is returning different unconstrained generic parameters
-
-// Function overloads whose only difference is returning different constrained generic parameters
-
-// Function overloads that differ only by type parameter constraints
-
-// Function overloads with matching accessibility
-
-// Function overloads with matching export
-
-// Function overloads with more params than implementation signature
-
-// Function overloads where return types are same infinitely recursive type reference
-
--- a/tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid01.ts
+++ b/tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid01.ts
@ -0,0 +1,4 @@
+function f(x: string): number;
+function f(x: string): void {
+    return;
+} 
--- a/tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid02.ts
+++ b/tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid02.ts
@ -0,0 +1,4 @@
+function f(x: string): void;
+function f(x: string): number {
+    return 0;
+} 
--- a/tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid03.ts
+++ b/tests/cases/conformance/functions/functionOverloadCompatibilityWithVoid03.ts
@ -0,0 +1,4 @@
+function f(x: string): void;
+function f(x: string): void {
+    return;
+} 
--- a/tests/cases/conformance/jsx/tsxAttributeResolution11.tsx
+++ b/tests/cases/conformance/jsx/tsxAttributeResolution11.tsx
@ -0,0 +1,29 @@
+//@jsx: preserve
+//@module: amd
+
+//@filename: react.d.ts
+declare module JSX {
+	interface Element { }
+	interface IntrinsicElements {
+	}
+	interface ElementAttributesProperty {
+		props;
+	}
+	interface IntrinsicAttributes {
+		ref?: string;
+	}
+}
+
+//@filename: file.tsx
+class MyComponent {  
+  render() {
+  }
+
+  props: {
+	  ref?: string;
+  }
+}
+
+// Should be an OK
+var x = <MyComponent bar='world' />;
+
--- a/tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags01.ts
+++ b/tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags01.ts
@ -20,7 +20,7 @@ function hasKind(entity: Entity, kind: "A"): entity is A;
 function hasKind(entity: Entity, kind: "B"): entity is B;
 function hasKind(entity: Entity, kind: Kind): entity is Entity;
 function hasKind(entity: Entity, kind: Kind): boolean {
-    return kind === is;
+    return entity.kind === kind;
 }

 let x: A = {
--- a/tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags02.ts
+++ b/tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags02.ts
@ -0,0 +1,42 @@
+// @declaration: true
+
+type Kind = "A" | "B"
+
+interface Entity {
+    kind: Kind;
+}
+
+interface A extends Entity {
+    kind: "A";
+    a: number;
+}
+
+interface B extends Entity {
+    kind: "B";
+    b: string;
+}
+
+function hasKind(entity: Entity, kind: "A"): entity is A;
+function hasKind(entity: Entity, kind: "B"): entity is B;
+function hasKind(entity: Entity, kind: Kind): entity is (A | B) {
+    return entity.kind === kind;
+}
+
+let x: A = {
+    kind: "A",
+    a: 100,
+}
+
+if (hasKind(x, "A")) {
+    let a = x;
+}
+else {
+    let b = x;
+}
+
+if (!hasKind(x, "B")) {
+    let c = x;
+}
+else {
+    let d = x;
+}
--- a/tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags03.ts
+++ b/tests/cases/conformance/types/stringLiteral/stringLiteralTypesAsTags03.ts
@ -0,0 +1,46 @@
+// @declaration: true
+
+type Kind = "A" | "B"
+
+interface Entity {
+    kind: Kind;
+}
+
+interface A extends Entity {
+    kind: "A";
+    a: number;
+}
+
+interface B extends Entity {
+    kind: "B";
+    b: string;
+}
+
+// Currently (2015-12-14), we write '"A" | "A"' and '"B" | "B"' to avoid
+// interpreting respective overloads as "specialized" signatures.
+// That way, we can avoid the need to look for a compatible overload
+// signature and simply check compatibility with the implementation.
+function hasKind(entity: Entity, kind: "A" | "A"): entity is A;
+function hasKind(entity: Entity, kind: "B" | "B"): entity is B;
+function hasKind(entity: Entity, kind: Kind): entity is Entity {
+    return entity.kind === kind;
+}
+
+let x: A = {
+    kind: "A",
+    a: 100,
+}
+
+if (hasKind(x, "A")) {
+    let a = x;
+}
+else {
+    let b = x;
+}
+
+if (!hasKind(x, "B")) {
+    let c = x;
+}
+else {
+    let d = x;
+}
--- a/tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloads01.ts
+++ b/tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloads01.ts
@ -9,7 +9,7 @@ function getFalsyPrimitive(x: "boolean" | "string"): boolean | string;
 function getFalsyPrimitive(x: "boolean" | "number"): boolean | number;
 function getFalsyPrimitive(x: "number" | "string"): number | string;
 function getFalsyPrimitive(x: "number" | "string" | "boolean"): number | string | boolean;
-function getFalsyPrimitive(x: PrimitiveName) {
+function getFalsyPrimitive(x: PrimitiveName): number | string | boolean {
    if (x === "string") {
        return "";
    }