diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 0ae33d08fd..494570c85c 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -388,23 +388,28 @@ module ts {
             bindChildren(node, /*symbolKind:*/ 0, /*isBlockScopeContainer:*/ true);
         }
 
-        function bindBlockScopedVariableDeclaration(node: Declaration) {
+        function bindBlockScopedDeclaration(node: Declaration, symbolKind: SymbolFlags, symbolExcludes: SymbolFlags) {
             switch (blockScopeContainer.kind) {
                 case SyntaxKind.ModuleDeclaration:
-                    declareModuleMember(node, SymbolFlags.BlockScopedVariable, SymbolFlags.BlockScopedVariableExcludes);
+                    declareModuleMember(node, symbolKind, symbolExcludes);
                     break;
                 case SyntaxKind.SourceFile:
                     if (isExternalModule(<SourceFile>container)) {
-                        declareModuleMember(node, SymbolFlags.BlockScopedVariable, SymbolFlags.BlockScopedVariableExcludes);
+                        declareModuleMember(node, symbolKind, symbolExcludes);
                         break;
                     }
+                    // fall through.
                 default:
                     if (!blockScopeContainer.locals) {
                         blockScopeContainer.locals = {};
                     }
-                    declareSymbol(blockScopeContainer.locals, undefined, node, SymbolFlags.BlockScopedVariable, SymbolFlags.BlockScopedVariableExcludes);
+                    declareSymbol(blockScopeContainer.locals, undefined, node, symbolKind, symbolExcludes);
             }
-            bindChildren(node, SymbolFlags.BlockScopedVariable, /*isBlockScopeContainer*/ false);
+            bindChildren(node, symbolKind, /*isBlockScopeContainer*/ false);
+        }
+
+        function bindBlockScopedVariableDeclaration(node: Declaration) {
+            bindBlockScopedDeclaration(node, SymbolFlags.BlockScopedVariable, SymbolFlags.BlockScopedVariableExcludes);
         }
 
         function getDestructuringParameterName(node: Declaration) {
@@ -493,7 +498,7 @@ module ts {
                     bindCatchVariableDeclaration(<CatchClause>node);
                     break;
                 case SyntaxKind.ClassDeclaration:
-                    bindDeclaration(<Declaration>node, SymbolFlags.Class, SymbolFlags.ClassExcludes, /*isBlockScopeContainer*/ false);
+                    bindBlockScopedDeclaration(<Declaration>node, SymbolFlags.Class, SymbolFlags.ClassExcludes);
                     break;
                 case SyntaxKind.InterfaceDeclaration:
                     bindDeclaration(<Declaration>node, SymbolFlags.Interface, SymbolFlags.InterfaceExcludes, /*isBlockScopeContainer*/ false);
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 3ce7fe5e1c..f0882a51c4 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -9760,6 +9760,10 @@ module ts {
                 grammarErrorOnNode(node, Diagnostics.class_declarations_are_only_supported_directly_inside_a_module_or_as_a_top_level_declaration);
             }
 
+            if (!node.name && !(node.flags & NodeFlags.Default)) {
+                grammarErrorOnFirstToken(node, Diagnostics.A_class_declaration_without_the_default_modifier_must_have_a_name);
+            }
+
             checkGrammarClassDeclarationHeritageClauses(node);
             checkDecorators(node);
             if (node.name) {
diff --git a/src/compiler/diagnosticInformationMap.generated.ts b/src/compiler/diagnosticInformationMap.generated.ts
index 3e9017786e..b141ce607f 100644
--- a/src/compiler/diagnosticInformationMap.generated.ts
+++ b/src/compiler/diagnosticInformationMap.generated.ts
@@ -167,6 +167,7 @@ module ts {
         Decorators_cannot_be_applied_to_multiple_get_Slashset_accessors_of_the_same_name: { code: 1207, category: DiagnosticCategory.Error, key: "Decorators cannot be applied to multiple get/set accessors of the same name." },
         Cannot_compile_non_external_modules_when_the_separateCompilation_flag_is_provided: { code: 1208, category: DiagnosticCategory.Error, key: "Cannot compile non-external modules when the '--separateCompilation' flag is provided." },
         Ambient_const_enums_are_not_allowed_when_the_separateCompilation_flag_is_provided: { code: 1209, category: DiagnosticCategory.Error, key: "Ambient const enums are not allowed when the '--separateCompilation' flag is provided." },
+        A_class_declaration_without_the_default_modifier_must_have_a_name: { code: 1210, category: DiagnosticCategory.Error, key: "A class declaration without the 'default' modifier must have a name" },
         Duplicate_identifier_0: { code: 2300, category: DiagnosticCategory.Error, key: "Duplicate identifier '{0}'." },
         Initializer_of_instance_member_variable_0_cannot_reference_identifier_1_declared_in_the_constructor: { code: 2301, category: DiagnosticCategory.Error, key: "Initializer of instance member variable '{0}' cannot reference identifier '{1}' declared in the constructor." },
         Static_members_cannot_reference_class_type_parameters: { code: 2302, category: DiagnosticCategory.Error, key: "Static members cannot reference class type parameters." },
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index f6edb3150b..cafc1f5efa 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -659,6 +659,10 @@
         "category": "Error",
         "code": 1209
     },
+    "A class declaration without the 'default' modifier must have a name": {
+        "category": "Error",
+        "code": 1210
+    },
     "Duplicate identifier '{0}'.": {
         "category": "Error",
         "code": 2300
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index 6ec4ea2389..5d4bf9df3e 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -262,6 +262,7 @@ module ts {
                 switch (node.kind) {
                     case SyntaxKind.FunctionDeclaration:
                     case SyntaxKind.ClassDeclaration:
+                    case SyntaxKind.ClassExpression:
                         generateNameForFunctionOrClassDeclaration(<Declaration>node);
                         break;
                     case SyntaxKind.ModuleDeclaration:
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 2972fba397..7a28ad0441 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -4764,7 +4764,7 @@ module ts {
             node.decorators = decorators;
             setModifiers(node, modifiers);
             parseExpected(SyntaxKind.ClassKeyword);
-            node.name = node.flags & NodeFlags.Default ? parseOptionalIdentifier() : parseIdentifier();
+            node.name = parseOptionalIdentifier();
             node.typeParameters = parseTypeParameters();
             node.heritageClauses = parseHeritageClauses(/*isClassHeritageClause:*/ true);
 
diff --git a/src/services/navigationBar.ts b/src/services/navigationBar.ts
index c6463aba73..e475827837 100644
--- a/src/services/navigationBar.ts
+++ b/src/services/navigationBar.ts
@@ -418,10 +418,10 @@ module ts.NavigationBar {
             }
 
             function createFunctionItem(node: FunctionDeclaration) {
-                if ((node.name || node.flags & NodeFlags.Default) && node.body && node.body.kind === SyntaxKind.Block) {
+                if (node.body && node.body.kind === SyntaxKind.Block) {
                     let childItems = getItemsWorker(sortNodes((<Block>node.body).statements), createChildItem);
 
-                    return getNavigationBarItem((!node.name && node.flags & NodeFlags.Default) ? "default": node.name.text ,
+                    return getNavigationBarItem(!node.name ? "default": node.name.text ,
                         ts.ScriptElementKind.functionElement,
                         getNodeModifiers(node),
                         [getNodeSpan(node)],
@@ -470,7 +470,7 @@ module ts.NavigationBar {
                     childItems = getItemsWorker(sortNodes(nodes), createChildItem);
                 }
 
-                var nodeName = !node.name && (node.flags & NodeFlags.Default) ? "default" : node.name.text;
+                var nodeName = !node.name ? "default" : node.name.text;
 
                 return getNavigationBarItem(
                     nodeName,
diff --git a/tests/baselines/reference/anonymousClassExpression1.errors.txt b/tests/baselines/reference/anonymousClassExpression1.errors.txt
new file mode 100644
index 0000000000..db4c5b4ce3
--- /dev/null
+++ b/tests/baselines/reference/anonymousClassExpression1.errors.txt
@@ -0,0 +1,9 @@
+tests/cases/compiler/anonymousClassExpression1.ts(2,19): error TS9003: 'class' expressions are not currently supported.
+
+
+==== tests/cases/compiler/anonymousClassExpression1.ts (1 errors) ====
+    function f() {
+        return typeof class {} === "function";
+                      ~~~~~
+!!! error TS9003: 'class' expressions are not currently supported.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/anonymousClassExpression1.js b/tests/baselines/reference/anonymousClassExpression1.js
new file mode 100644
index 0000000000..78cf5b05c5
--- /dev/null
+++ b/tests/baselines/reference/anonymousClassExpression1.js
@@ -0,0 +1,13 @@
+//// [anonymousClassExpression1.ts]
+function f() {
+    return typeof class {} === "function";
+}
+
+//// [anonymousClassExpression1.js]
+function f() {
+    return typeof (function () {
+        function default_1() {
+        }
+        return default_1;
+    })() === "function";
+}
diff --git a/tests/baselines/reference/classDeclarationBlockScoping1.errors.txt b/tests/baselines/reference/classDeclarationBlockScoping1.errors.txt
new file mode 100644
index 0000000000..4f15007bb2
--- /dev/null
+++ b/tests/baselines/reference/classDeclarationBlockScoping1.errors.txt
@@ -0,0 +1,13 @@
+tests/cases/compiler/classDeclarationBlockScoping1.ts(5,11): error TS9004: 'class' declarations are only supported directly inside a module or as a top level declaration.
+
+
+==== tests/cases/compiler/classDeclarationBlockScoping1.ts (1 errors) ====
+    class C {
+    }
+    
+    {
+        class C {
+              ~
+!!! error TS9004: 'class' declarations are only supported directly inside a module or as a top level declaration.
+        }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/classDeclarationBlockScoping1.js b/tests/baselines/reference/classDeclarationBlockScoping1.js
new file mode 100644
index 0000000000..717c2f788c
--- /dev/null
+++ b/tests/baselines/reference/classDeclarationBlockScoping1.js
@@ -0,0 +1,22 @@
+//// [classDeclarationBlockScoping1.ts]
+class C {
+}
+
+{
+    class C {
+    }
+}
+
+//// [classDeclarationBlockScoping1.js]
+var C = (function () {
+    function C() {
+    }
+    return C;
+})();
+{
+    var C = (function () {
+        function C() {
+        }
+        return C;
+    })();
+}
diff --git a/tests/baselines/reference/classDeclarationBlockScoping2.errors.txt b/tests/baselines/reference/classDeclarationBlockScoping2.errors.txt
new file mode 100644
index 0000000000..2a9885e110
--- /dev/null
+++ b/tests/baselines/reference/classDeclarationBlockScoping2.errors.txt
@@ -0,0 +1,18 @@
+tests/cases/compiler/classDeclarationBlockScoping2.ts(2,11): error TS9004: 'class' declarations are only supported directly inside a module or as a top level declaration.
+tests/cases/compiler/classDeclarationBlockScoping2.ts(5,15): error TS9004: 'class' declarations are only supported directly inside a module or as a top level declaration.
+
+
+==== tests/cases/compiler/classDeclarationBlockScoping2.ts (2 errors) ====
+    function f() {
+        class C {}
+              ~
+!!! error TS9004: 'class' declarations are only supported directly inside a module or as a top level declaration.
+        var c1 = C;
+        {
+            class C {}
+                  ~
+!!! error TS9004: 'class' declarations are only supported directly inside a module or as a top level declaration.
+            var c2 = C;
+        }
+        return C === c1;
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/classDeclarationBlockScoping2.js b/tests/baselines/reference/classDeclarationBlockScoping2.js
new file mode 100644
index 0000000000..9e46807711
--- /dev/null
+++ b/tests/baselines/reference/classDeclarationBlockScoping2.js
@@ -0,0 +1,29 @@
+//// [classDeclarationBlockScoping2.ts]
+function f() {
+    class C {}
+    var c1 = C;
+    {
+        class C {}
+        var c2 = C;
+    }
+    return C === c1;
+}
+
+//// [classDeclarationBlockScoping2.js]
+function f() {
+    var C = (function () {
+        function C() {
+        }
+        return C;
+    })();
+    var c1 = C;
+    {
+        var C = (function () {
+            function C() {
+            }
+            return C;
+        })();
+        var c2 = C;
+    }
+    return C === c1;
+}
diff --git a/tests/baselines/reference/classWithPredefinedTypesAsNames2.errors.txt b/tests/baselines/reference/classWithPredefinedTypesAsNames2.errors.txt
index 73cb373180..84c258b550 100644
--- a/tests/baselines/reference/classWithPredefinedTypesAsNames2.errors.txt
+++ b/tests/baselines/reference/classWithPredefinedTypesAsNames2.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/classes/classDeclarations/classWithPredefinedTypesAsNames2.ts(3,7): error TS1003: Identifier expected.
+tests/cases/conformance/classes/classDeclarations/classWithPredefinedTypesAsNames2.ts(3,7): error TS1005: '{' expected.
 
 
 ==== tests/cases/conformance/classes/classDeclarations/classWithPredefinedTypesAsNames2.ts (1 errors) ====
@@ -6,4 +6,4 @@ tests/cases/conformance/classes/classDeclarations/classWithPredefinedTypesAsName
     
     class void {}
           ~~~~
-!!! error TS1003: Identifier expected.
\ No newline at end of file
+!!! error TS1005: '{' expected.
\ No newline at end of file
diff --git a/tests/baselines/reference/classWithPredefinedTypesAsNames2.js b/tests/baselines/reference/classWithPredefinedTypesAsNames2.js
index a47adcbe32..91ff735acc 100644
--- a/tests/baselines/reference/classWithPredefinedTypesAsNames2.js
+++ b/tests/baselines/reference/classWithPredefinedTypesAsNames2.js
@@ -5,9 +5,9 @@ class void {}
 
 //// [classWithPredefinedTypesAsNames2.js]
 // classes cannot use predefined types as names
-var  = (function () {
-    function () {
+var default_1 = (function () {
+    function default_1() {
     }
-    return ;
+    return default_1;
 })();
 void {};
diff --git a/tests/baselines/reference/externModule.errors.txt b/tests/baselines/reference/externModule.errors.txt
index d16c71ab05..8d4126350c 100644
--- a/tests/baselines/reference/externModule.errors.txt
+++ b/tests/baselines/reference/externModule.errors.txt
@@ -8,9 +8,13 @@ tests/cases/compiler/externModule.ts(18,6): error TS2390: Constructor implementa
 tests/cases/compiler/externModule.ts(20,13): error TS2391: Function implementation is missing or not immediately following the declaration.
 tests/cases/compiler/externModule.ts(26,13): error TS2391: Function implementation is missing or not immediately following the declaration.
 tests/cases/compiler/externModule.ts(28,13): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/externModule.ts(32,11): error TS2304: Cannot find name 'XDate'.
+tests/cases/compiler/externModule.ts(34,7): error TS2304: Cannot find name 'XDate'.
+tests/cases/compiler/externModule.ts(36,7): error TS2304: Cannot find name 'XDate'.
+tests/cases/compiler/externModule.ts(37,3): error TS2304: Cannot find name 'XDate'.
 
 
-==== tests/cases/compiler/externModule.ts (10 errors) ====
+==== tests/cases/compiler/externModule.ts (14 errors) ====
     declare module {
     ~~~~~~~
 !!! error TS2304: Cannot find name 'declare'.
@@ -63,10 +67,18 @@ tests/cases/compiler/externModule.ts(28,13): error TS2391: Function implementati
     }
     
     var d=new XDate();
+              ~~~~~
+!!! error TS2304: Cannot find name 'XDate'.
     d.getDay();
     d=new XDate(1978,2);
+          ~~~~~
+!!! error TS2304: Cannot find name 'XDate'.
     d.getXDate();
     var n=XDate.parse("3/2/2004");
+          ~~~~~
+!!! error TS2304: Cannot find name 'XDate'.
     n=XDate.UTC(1964,2,1);
+      ~~~~~
+!!! error TS2304: Cannot find name 'XDate'.
     
     
\ No newline at end of file
diff --git a/tests/baselines/reference/objectTypesWithPredefinedTypesAsName2.errors.txt b/tests/baselines/reference/objectTypesWithPredefinedTypesAsName2.errors.txt
index 32a693abdc..f2dbd67230 100644
--- a/tests/baselines/reference/objectTypesWithPredefinedTypesAsName2.errors.txt
+++ b/tests/baselines/reference/objectTypesWithPredefinedTypesAsName2.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/types/specifyingTypes/predefinedTypes/objectTypesWithPredefinedTypesAsName2.ts(3,7): error TS1003: Identifier expected.
+tests/cases/conformance/types/specifyingTypes/predefinedTypes/objectTypesWithPredefinedTypesAsName2.ts(3,7): error TS1005: '{' expected.
 
 
 ==== tests/cases/conformance/types/specifyingTypes/predefinedTypes/objectTypesWithPredefinedTypesAsName2.ts (1 errors) ====
@@ -6,4 +6,4 @@ tests/cases/conformance/types/specifyingTypes/predefinedTypes/objectTypesWithPre
     
     class void {} // parse error unlike the others
           ~~~~
-!!! error TS1003: Identifier expected.
\ No newline at end of file
+!!! error TS1005: '{' expected.
\ No newline at end of file
diff --git a/tests/baselines/reference/objectTypesWithPredefinedTypesAsName2.js b/tests/baselines/reference/objectTypesWithPredefinedTypesAsName2.js
index b47901b2f0..974744f187 100644
--- a/tests/baselines/reference/objectTypesWithPredefinedTypesAsName2.js
+++ b/tests/baselines/reference/objectTypesWithPredefinedTypesAsName2.js
@@ -5,9 +5,9 @@ class void {} // parse error unlike the others
 
 //// [objectTypesWithPredefinedTypesAsName2.js]
 // it is an error to use a predefined type as a type name
-var  = (function () {
-    function () {
+var default_1 = (function () {
+    function default_1() {
     }
-    return ;
+    return default_1;
 })();
 void {}; // parse error unlike the others
diff --git a/tests/baselines/reference/parserInvalidIdentifiersInVariableStatements1.errors.txt b/tests/baselines/reference/parserInvalidIdentifiersInVariableStatements1.errors.txt
index 35b279b443..d7245fc708 100644
--- a/tests/baselines/reference/parserInvalidIdentifiersInVariableStatements1.errors.txt
+++ b/tests/baselines/reference/parserInvalidIdentifiersInVariableStatements1.errors.txt
@@ -1,6 +1,6 @@
 tests/cases/conformance/parser/ecmascript5/ErrorRecovery/VariableLists/parserInvalidIdentifiersInVariableStatements1.ts(1,5): error TS1134: Variable declaration expected.
 tests/cases/conformance/parser/ecmascript5/ErrorRecovery/VariableLists/parserInvalidIdentifiersInVariableStatements1.ts(3,5): error TS1134: Variable declaration expected.
-tests/cases/conformance/parser/ecmascript5/ErrorRecovery/VariableLists/parserInvalidIdentifiersInVariableStatements1.ts(3,10): error TS1003: Identifier expected.
+tests/cases/conformance/parser/ecmascript5/ErrorRecovery/VariableLists/parserInvalidIdentifiersInVariableStatements1.ts(3,10): error TS1005: '{' expected.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/ErrorRecovery/VariableLists/parserInvalidIdentifiersInVariableStatements1.ts (3 errors) ====
@@ -12,6 +12,6 @@ tests/cases/conformance/parser/ecmascript5/ErrorRecovery/VariableLists/parserInv
         ~~~~~
 !!! error TS1134: Variable declaration expected.
              ~
-!!! error TS1003: Identifier expected.
+!!! error TS1005: '{' expected.
     var bar;
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parserInvalidIdentifiersInVariableStatements1.js b/tests/baselines/reference/parserInvalidIdentifiersInVariableStatements1.js
index 422b012246..e6b9c9fa1b 100644
--- a/tests/baselines/reference/parserInvalidIdentifiersInVariableStatements1.js
+++ b/tests/baselines/reference/parserInvalidIdentifiersInVariableStatements1.js
@@ -9,10 +9,10 @@ var bar;
 var ;
 var foo;
 var ;
-var  = (function () {
-    function () {
+var default_1 = (function () {
+    function default_1() {
     }
-    return ;
+    return default_1;
 })();
 ;
 var bar;
diff --git a/tests/cases/compiler/anonymousClassExpression1.ts b/tests/cases/compiler/anonymousClassExpression1.ts
new file mode 100644
index 0000000000..594ac09251
--- /dev/null
+++ b/tests/cases/compiler/anonymousClassExpression1.ts
@@ -0,0 +1,3 @@
+function f() {
+    return typeof class {} === "function";
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/classDeclarationBlockScoping1.ts b/tests/cases/compiler/classDeclarationBlockScoping1.ts
new file mode 100644
index 0000000000..b6012f785b
--- /dev/null
+++ b/tests/cases/compiler/classDeclarationBlockScoping1.ts
@@ -0,0 +1,7 @@
+class C {
+}
+
+{
+    class C {
+    }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/classDeclarationBlockScoping2.ts b/tests/cases/compiler/classDeclarationBlockScoping2.ts
new file mode 100644
index 0000000000..2a0c4c1213
--- /dev/null
+++ b/tests/cases/compiler/classDeclarationBlockScoping2.ts
@@ -0,0 +1,9 @@
+function f() {
+    class C {}
+    var c1 = C;
+    {
+        class C {}
+        var c2 = C;
+    }
+    return C === c1;
+}
\ No newline at end of file
diff --git a/tests/cases/fourslash/scriptLexicalStructureItems2.ts b/tests/cases/fourslash/scriptLexicalStructureItems2.ts
index 7022c082ce..3b94260ddb 100644
--- a/tests/cases/fourslash/scriptLexicalStructureItems2.ts
+++ b/tests/cases/fourslash/scriptLexicalStructureItems2.ts
@@ -8,5 +8,5 @@ edit.insertLine("module A");
 edit.insert("export class ");
 
 // should not crash
-verify.getScriptLexicalStructureListCount(1);
+verify.getScriptLexicalStructureListCount(2);
 
diff --git a/tests/cases/fourslash/scriptLexicalStructureMissingName2.ts b/tests/cases/fourslash/scriptLexicalStructureMissingName2.ts
index b805427ff6..bf0dc03899 100644
--- a/tests/cases/fourslash/scriptLexicalStructureMissingName2.ts
+++ b/tests/cases/fourslash/scriptLexicalStructureMissingName2.ts
@@ -8,4 +8,4 @@
 
 
 // The class is unnamed, so its method is not included either.
-verify.getScriptLexicalStructureListCount(0);
+verify.getScriptLexicalStructureListCount(2);