Allow duplicate identifiers as long as their declarations span multiple blocks

Fixes #8675

src/compiler/checker.ts

@@ -12954,6 +12954,82 @@ namespace ts {
             }
         }
 
+        function checkClassForDuplicateDeclarations(node: ClassLikeDeclaration) {
+            const getter = 1, setter = 2, property = getter | setter;
+
+            const instanceNames: Map<number> = {};
+            const staticNames: Map<number> = {};
+            for (const member of node.members) {
+                if (member.kind === SyntaxKind.Constructor) {
+                    for (const param of (member as ConstructorDeclaration).parameters) {
+                        if (isParameterPropertyDeclaration(param)) {
+                            addName(instanceNames, param.name, (param.name as Identifier).text, property);
+                        }
+                    }
+                }
+                else {
+                    const static = forEach(member.modifiers, m => m.kind === SyntaxKind.StaticKeyword);
+                    const names = static ? staticNames : instanceNames;
+
+                    const memberName = member.name && getPropertyNameForPropertyNameNode(member.name);
+                    switch (member.kind) {
+                        case SyntaxKind.GetAccessor:
+                            addName(names, member.name, memberName, getter);
+                            break;
+
+                        case SyntaxKind.SetAccessor:
+                            addName(names, member.name, memberName, setter);
+                            break;
+
+                        case SyntaxKind.PropertyDeclaration:
+                            addName(names, member.name, memberName, property);
+                            break;
+                    }
+                }
+            }
+
+            function addName(names: Map<number>, location: Node, name: string, meaning: number) {
+                if (hasProperty(names, name)) {
+                    const prev = names[name];
+                    if (prev & meaning) {
+                        error(location, Diagnostics.Duplicate_identifier_0, getTextOfNode(location));
+                    }
+                    else {
+                        names[name] = prev | meaning;
+                    }
+                }
+                else {
+                    names[name] = meaning;
+                }
+            }
+        }
+
+        function checkObjectTypeForDuplicateDeclarations(node: TypeLiteralNode | InterfaceDeclaration) {
+            const names: Map<boolean> = {};
+            for (const member of node.members) {
+                if (member.kind == SyntaxKind.PropertySignature) {
+                    let memberName: string;
+                    switch (member.name.kind) {
+                        case SyntaxKind.StringLiteral:
+                        case SyntaxKind.NumericLiteral:
+                        case SyntaxKind.Identifier:
+                            memberName = (member.name as LiteralExpression | Identifier).text;
+                            break;
+                        default:
+                            continue;
+                    }
+
+                    if (hasProperty(names, memberName)) {
+                        error(member.symbol.valueDeclaration.name, Diagnostics.Duplicate_identifier_0, memberName);
+                        error(member.name, Diagnostics.Duplicate_identifier_0, memberName);
+                    }
+                    else {
+                        names[memberName] = true;
+                    }
+                }
+            }
+        }
+
         function checkTypeForDuplicateIndexSignatures(node: Node) {
             if (node.kind === SyntaxKind.InterfaceDeclaration) {
                 const nodeSymbol = getSymbolOfNode(node);
@@ -13238,6 +13314,7 @@ namespace ts {
                 const type = getTypeFromTypeLiteralOrFunctionOrConstructorTypeNode(node);
                 checkIndexConstraints(type);
                 checkTypeForDuplicateIndexSignatures(node);
+                checkObjectTypeForDuplicateDeclarations(node);
             }
         }
 
@@ -14430,6 +14507,10 @@ namespace ts {
                 if (node.initializer) {
                     checkTypeAssignableTo(checkExpressionCached(node.initializer), declarationType, node, /*headMessage*/ undefined);
                 }
+                if (!areDeclarationFlagsIdentical(node, symbol.valueDeclaration)) {
+                    error(symbol.valueDeclaration.name, Diagnostics.All_declarations_of_0_must_have_identical_modifiers, declarationNameToString(node.name));
+                    error(node.name, Diagnostics.All_declarations_of_0_must_have_identical_modifiers, declarationNameToString(node.name));
+                }
             }
             if (node.kind !== SyntaxKind.PropertyDeclaration && node.kind !== SyntaxKind.PropertySignature) {
                 // We know we don't have a binding pattern or computed name here
@@ -14444,6 +14525,21 @@ namespace ts {
             }
         }
 
+        function areDeclarationFlagsIdentical(left: Declaration, right: Declaration) {
+            if (hasQuestionToken(left) !== hasQuestionToken(right)) {
+                return false;
+            }
+
+            const interestingFlags = NodeFlags.Private |
+                NodeFlags.Protected |
+                NodeFlags.Async |
+                NodeFlags.Abstract |
+                NodeFlags.Readonly |
+                NodeFlags.Static;
+
+            return (left.flags & interestingFlags) === (right.flags & interestingFlags);
+        }
+
         function checkVariableDeclaration(node: VariableDeclaration) {
             checkGrammarVariableDeclaration(node);
             return checkVariableLikeDeclaration(node);
@@ -15237,6 +15333,7 @@ namespace ts {
             const typeWithThis = getTypeWithThisArgument(type);
             const staticType = <ObjectType>getTypeOfSymbol(symbol);
             checkTypeParameterListsIdentical(node, symbol);
+            checkClassForDuplicateDeclarations(node);
 
             const baseTypeNode = getClassExtendsHeritageClauseElement(node);
             if (baseTypeNode) {
@@ -15514,6 +15611,7 @@ namespace ts {
                         checkIndexConstraints(type);
                     }
                 }
+                checkObjectTypeForDuplicateDeclarations(node);
             }
             forEach(getInterfaceBaseTypeNodes(node), heritageElement => {
                 if (!isSupportedExpressionWithTypeArguments(heritageElement)) {
@@ -18152,7 +18250,6 @@ namespace ts {
                     name.kind === SyntaxKind.ComputedPropertyName) {
                     // If the name is not a ComputedPropertyName, the grammar checking will skip it
                     checkGrammarComputedPropertyName(<ComputedPropertyName>name);
-                    continue;
                 }
 
                 if (prop.kind === SyntaxKind.ShorthandPropertyAssignment && !inDestructuring && (<ShorthandPropertyAssignment>prop).objectAssignmentInitializer) {
@@ -18198,17 +18295,22 @@ namespace ts {
                     Debug.fail("Unexpected syntax kind:" + prop.kind);
                 }
 
-                if (!hasProperty(seen, (<Identifier>name).text)) {
-                    seen[(<Identifier>name).text] = currentKind;
+                const effectiveName = getPropertyNameForPropertyNameNode(name);
+                if (effectiveName === undefined) {
+                    continue;
+                }
+
+                if (!hasProperty(seen, effectiveName)) {
+                    seen[effectiveName] = currentKind;
                 }
                 else {
-                    const existingKind = seen[(<Identifier>name).text];
+                    const existingKind = seen[effectiveName];
                     if (currentKind === Property && existingKind === Property) {
-                        continue;
+                        grammarErrorOnNode(name, Diagnostics.Duplicate_identifier_0, getTextOfNode(name));
                     }
                     else if ((currentKind & GetOrSetAccessor) && (existingKind & GetOrSetAccessor)) {
                         if (existingKind !== GetOrSetAccessor && currentKind !== existingKind) {
-                            seen[(<Identifier>name).text] = currentKind | existingKind;
+                            seen[effectiveName] = currentKind | existingKind;
                         }
                         else {
                             return grammarErrorOnNode(name, Diagnostics.An_object_literal_cannot_have_multiple_get_Slashset_accessors_with_the_same_name);

src/compiler/diagnosticMessages.json

@@ -1927,6 +1927,10 @@
         "category": "Error",
         "code": 2686
     },
+    "All declarations of '{0}' must have identical modifiers.": {
+        "category": "Error",
+        "code": 2687
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000

src/compiler/types.ts

@@ -2025,7 +2025,7 @@ namespace ts {
         BlockScopedVariableExcludes = Value,
 
         ParameterExcludes = Value,
-        PropertyExcludes = Value,
+        PropertyExcludes = None,
         EnumMemberExcludes = Value,
         FunctionExcludes = Value & ~(Function | ValueModule),
         ClassExcludes = (Value | Type) & ~(ValueModule | Interface), // class-interface mergability done in checker.ts

src/compiler/utilities.ts

@@ -1774,7 +1774,7 @@ namespace ts {
     }
 
     export function getPropertyNameForPropertyNameNode(name: DeclarationName): string {
-        if (name.kind === SyntaxKind.Identifier || name.kind === SyntaxKind.StringLiteral || name.kind === SyntaxKind.NumericLiteral) {
+        if (name.kind === SyntaxKind.Identifier || name.kind === SyntaxKind.StringLiteral || name.kind === SyntaxKind.NumericLiteral || name.kind === SyntaxKind.Parameter) {
             return (<Identifier | LiteralExpression>name).text;
         }
         if (name.kind === SyntaxKind.ComputedPropertyName) {

tests/baselines/reference/binaryIntegerLiteralError.errors.txt

@@ -1,11 +1,8 @@
 tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/binaryIntegerLiteralError.ts(2,17): error TS1005: ',' expected.
 tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/binaryIntegerLiteralError.ts(3,17): error TS1005: ',' expected.
-tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/binaryIntegerLiteralError.ts(6,5): error TS2300: Duplicate identifier '0b11010'.
-tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/binaryIntegerLiteralError.ts(7,5): error TS2300: Duplicate identifier '26'.
-tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/binaryIntegerLiteralError.ts(8,5): error TS2300: Duplicate identifier '"26"'.
 
 
-==== tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/binaryIntegerLiteralError.ts (5 errors) ====
+==== tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/binaryIntegerLiteralError.ts (2 errors) ====
     // error
     var bin1 = 0B1102110;
                     ~~~~
@@ -16,13 +13,7 @@ tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/binaryIntegerLiteralErr
     
     var obj1 = {
         0b11010: "hi",
-        ~~~~~~~
-!!! error TS2300: Duplicate identifier '0b11010'.
         26: "Hello",
-        ~~
-!!! error TS2300: Duplicate identifier '26'.
         "26": "world",
-        ~~~~
-!!! error TS2300: Duplicate identifier '"26"'.
     };
     

tests/baselines/reference/callSignaturesWithParameterInitializers2.errors.txt

@@ -1,12 +1,10 @@
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/callSignaturesWithParameterInitializers2.ts(4,14): error TS2371: A parameter initializer is only allowed in a function or constructor implementation.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/callSignaturesWithParameterInitializers2.ts(11,9): error TS2371: A parameter initializer is only allowed in a function or constructor implementation.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/callSignaturesWithParameterInitializers2.ts(20,5): error TS2300: Duplicate identifier 'foo'.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/callSignaturesWithParameterInitializers2.ts(20,9): error TS2371: A parameter initializer is only allowed in a function or constructor implementation.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/callSignaturesWithParameterInitializers2.ts(20,15): error TS1005: '{' expected.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/callSignaturesWithParameterInitializers2.ts(21,5): error TS2300: Duplicate identifier 'foo'.
 
 
-==== tests/cases/conformance/types/objectTypeLiteral/callSignatures/callSignaturesWithParameterInitializers2.ts (6 errors) ====
+==== tests/cases/conformance/types/objectTypeLiteral/callSignatures/callSignaturesWithParameterInitializers2.ts (4 errors) ====
     // Optional parameters allow initializers only in implementation signatures
     // All the below declarations are errors
     
@@ -31,15 +29,11 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/callSignaturesWit
     
     var b = {
         foo(x = 1), // error
-        ~~~
-!!! error TS2300: Duplicate identifier 'foo'.
             ~~~~~
 !!! error TS2371: A parameter initializer is only allowed in a function or constructor implementation.
                   ~
 !!! error TS1005: '{' expected.
         foo(x = 1) { }, // error
-        ~~~
-!!! error TS2300: Duplicate identifier 'foo'.
     }
     
     b.foo();

tests/baselines/reference/classAndInterfaceMergeConflictingMembers.errors.txt

@@ -1,44 +1,38 @@
-tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(2,12): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(6,5): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(10,15): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(14,5): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(18,13): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(22,5): error TS2300: Duplicate identifier 'x'.
+tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(10,15): error TS2686: All declarations of 'x' must have identical modifiers.
+tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(14,5): error TS2686: All declarations of 'x' must have identical modifiers.
+tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(18,13): error TS2686: All declarations of 'x' must have identical modifiers.
+tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts(22,5): error TS2686: All declarations of 'x' must have identical modifiers.
 
 
-==== tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts (6 errors) ====
+==== tests/cases/conformance/classes/classDeclarations/classAndInterfaceMergeConflictingMembers.ts (4 errors) ====
     declare class C1 {
         public x : number;
-               ~
-!!! error TS2300: Duplicate identifier 'x'.
     }
     
     interface C1 {
         x : number;
-        ~
-!!! error TS2300: Duplicate identifier 'x'.
     }
     
     declare class C2 {
         protected x : number;
                   ~
-!!! error TS2300: Duplicate identifier 'x'.
+!!! error TS2686: All declarations of 'x' must have identical modifiers.
     }
     
     interface C2 {
         x : number;
         ~
-!!! error TS2300: Duplicate identifier 'x'.
+!!! error TS2686: All declarations of 'x' must have identical modifiers.
     }
     
     declare class C3 {
         private x : number;
                 ~
-!!! error TS2300: Duplicate identifier 'x'.
+!!! error TS2686: All declarations of 'x' must have identical modifiers.
     }
     
     interface C3 {
         x : number;
         ~
-!!! error TS2300: Duplicate identifier 'x'.
+!!! error TS2686: All declarations of 'x' must have identical modifiers.
     }

tests/baselines/reference/classAndInterfaceWithSameName.errors.txt

@@ -1,27 +0,0 @@
-tests/cases/conformance/classes/classDeclarations/classAndInterfaceWithSameName.ts(1,11): error TS2300: Duplicate identifier 'foo'.
-tests/cases/conformance/classes/classDeclarations/classAndInterfaceWithSameName.ts(2,15): error TS2300: Duplicate identifier 'foo'.
-tests/cases/conformance/classes/classDeclarations/classAndInterfaceWithSameName.ts(6,9): error TS2300: Duplicate identifier 'bar'.
-tests/cases/conformance/classes/classDeclarations/classAndInterfaceWithSameName.ts(10,9): error TS2300: Duplicate identifier 'bar'.
-
-
-==== tests/cases/conformance/classes/classDeclarations/classAndInterfaceWithSameName.ts (4 errors) ====
-    class C { foo: string; }
-              ~~~
-!!! error TS2300: Duplicate identifier 'foo'.
-    interface C { foo: string; }
-                  ~~~
-!!! error TS2300: Duplicate identifier 'foo'.
-    
-    module M {
-        class D {
-            bar: string;
-            ~~~
-!!! error TS2300: Duplicate identifier 'bar'.
-        }
-    
-        interface D {
-            bar: string;
-            ~~~
-!!! error TS2300: Duplicate identifier 'bar'.
-        }
-    }

tests/baselines/reference/classAndInterfaceWithSameName.symbols

@@ -0,0 +1,26 @@
+=== tests/cases/conformance/classes/classDeclarations/classAndInterfaceWithSameName.ts ===
+class C { foo: string; }
+>C : Symbol(C, Decl(classAndInterfaceWithSameName.ts, 0, 0), Decl(classAndInterfaceWithSameName.ts, 0, 24))
+>foo : Symbol(C.foo, Decl(classAndInterfaceWithSameName.ts, 0, 9), Decl(classAndInterfaceWithSameName.ts, 1, 13))
+
+interface C { foo: string; }
+>C : Symbol(C, Decl(classAndInterfaceWithSameName.ts, 0, 0), Decl(classAndInterfaceWithSameName.ts, 0, 24))
+>foo : Symbol(C.foo, Decl(classAndInterfaceWithSameName.ts, 0, 9), Decl(classAndInterfaceWithSameName.ts, 1, 13))
+
+module M {
+>M : Symbol(M, Decl(classAndInterfaceWithSameName.ts, 1, 28))
+
+    class D {
+>D : Symbol(D, Decl(classAndInterfaceWithSameName.ts, 3, 10), Decl(classAndInterfaceWithSameName.ts, 6, 5))
+
+        bar: string;
+>bar : Symbol(D.bar, Decl(classAndInterfaceWithSameName.ts, 4, 13), Decl(classAndInterfaceWithSameName.ts, 8, 17))
+    }
+
+    interface D {
+>D : Symbol(D, Decl(classAndInterfaceWithSameName.ts, 3, 10), Decl(classAndInterfaceWithSameName.ts, 6, 5))
+
+        bar: string;
+>bar : Symbol(D.bar, Decl(classAndInterfaceWithSameName.ts, 4, 13), Decl(classAndInterfaceWithSameName.ts, 8, 17))
+    }
+}

tests/baselines/reference/classAndInterfaceWithSameName.types

@@ -0,0 +1,26 @@
+=== tests/cases/conformance/classes/classDeclarations/classAndInterfaceWithSameName.ts ===
+class C { foo: string; }
+>C : C
+>foo : string
+
+interface C { foo: string; }
+>C : C
+>foo : string
+
+module M {
+>M : typeof M
+
+    class D {
+>D : D
+
+        bar: string;
+>bar : string
+    }
+
+    interface D {
+>D : D
+
+        bar: string;
+>bar : string
+    }
+}

tests/baselines/reference/constructSignatureWithAccessibilityModifiersOnParameters2.errors.txt

@@ -1,12 +1,8 @@
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(4,17): error TS2369: A parameter property is only allowed in a constructor implementation.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(4,24): error TS2300: Duplicate identifier 'x'.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(4,27): error TS2369: A parameter property is only allowed in a constructor implementation.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(4,35): error TS2300: Duplicate identifier 'y'.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(5,24): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(5,35): error TS2300: Duplicate identifier 'y'.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(9,17): error TS2369: A parameter property is only allowed in a constructor implementation.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(9,25): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(10,24): error TS2300: Duplicate identifier 'x'.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(9,25): error TS2686: All declarations of 'x' must have identical modifiers.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(10,24): error TS2686: All declarations of 'x' must have identical modifiers.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(14,17): error TS2369: A parameter property is only allowed in a constructor implementation.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(19,10): error TS2369: A parameter property is only allowed in a constructor implementation.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(20,10): error TS2369: A parameter property is only allowed in a constructor implementation.
@@ -18,24 +14,16 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatur
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts(35,10): error TS2369: A parameter property is only allowed in a constructor implementation.
 
 
-==== tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts (18 errors) ====
+==== tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatureWithAccessibilityModifiersOnParameters2.ts (14 errors) ====
     // Parameter properties are not valid in overloads of constructors
     
     class C {
         constructor(public x, private y);
                     ~~~~~~~~
 !!! error TS2369: A parameter property is only allowed in a constructor implementation.
-                           ~
-!!! error TS2300: Duplicate identifier 'x'.
                               ~~~~~~~~~
 !!! error TS2369: A parameter property is only allowed in a constructor implementation.
-                                      ~
-!!! error TS2300: Duplicate identifier 'y'.
         constructor(public x, private y) { }
-                           ~
-!!! error TS2300: Duplicate identifier 'x'.
-                                      ~
-!!! error TS2300: Duplicate identifier 'y'.
     }
     
     class C2 {
@@ -43,10 +31,10 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/constructSignatur
                     ~~~~~~~~~
 !!! error TS2369: A parameter property is only allowed in a constructor implementation.
                             ~
-!!! error TS2300: Duplicate identifier 'x'.
+!!! error TS2686: All declarations of 'x' must have identical modifiers.
         constructor(public x) { }
                            ~
-!!! error TS2300: Duplicate identifier 'x'.
+!!! error TS2686: All declarations of 'x' must have identical modifiers.
     }
     
     class C3 {

tests/baselines/reference/constructorParameterProperties2.errors.txt

@@ -1,12 +1,13 @@
-tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts(10,5): error TS2300: Duplicate identifier 'y'.
 tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts(11,24): error TS2300: Duplicate identifier 'y'.
-tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts(18,5): error TS2300: Duplicate identifier 'y'.
+tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts(18,5): error TS2686: All declarations of 'y' must have identical modifiers.
 tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts(19,25): error TS2300: Duplicate identifier 'y'.
-tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts(26,5): error TS2300: Duplicate identifier 'y'.
+tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts(19,25): error TS2686: All declarations of 'y' must have identical modifiers.
+tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts(26,5): error TS2686: All declarations of 'y' must have identical modifiers.
 tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts(27,27): error TS2300: Duplicate identifier 'y'.
+tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts(27,27): error TS2686: All declarations of 'y' must have identical modifiers.
 
 
-==== tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts (6 errors) ====
+==== tests/cases/conformance/classes/constructorDeclarations/constructorParameters/constructorParameterProperties2.ts (7 errors) ====
     class C {
         y: number;
         constructor(y: number) { } // ok
@@ -17,8 +18,6 @@ tests/cases/conformance/classes/constructorDeclarations/constructorParameters/co
     
     class D {
         y: number;
-        ~
-!!! error TS2300: Duplicate identifier 'y'.
         constructor(public y: number) { } // error
                            ~
 !!! error TS2300: Duplicate identifier 'y'.
@@ -30,10 +29,12 @@ tests/cases/conformance/classes/constructorDeclarations/constructorParameters/co
     class E {
         y: number;
         ~
-!!! error TS2300: Duplicate identifier 'y'.
+!!! error TS2686: All declarations of 'y' must have identical modifiers.
         constructor(private y: number) { } // error
                             ~
 !!! error TS2300: Duplicate identifier 'y'.
+                            ~
+!!! error TS2686: All declarations of 'y' must have identical modifiers.
     }
     
     var e: E;
@@ -42,10 +43,12 @@ tests/cases/conformance/classes/constructorDeclarations/constructorParameters/co
     class F {
         y: number;
         ~
-!!! error TS2300: Duplicate identifier 'y'.
+!!! error TS2686: All declarations of 'y' must have identical modifiers.
         constructor(protected y: number) { } // error
                               ~
 !!! error TS2300: Duplicate identifier 'y'.
+                              ~
+!!! error TS2686: All declarations of 'y' must have identical modifiers.
     }
     
     var f: F;

tests/baselines/reference/derivedInterfaceIncompatibleWithBaseIndexer.errors.txt

@@ -4,12 +4,10 @@ tests/cases/conformance/interfaces/interfaceDeclarations/derivedInterfaceIncompa
 tests/cases/conformance/interfaces/interfaceDeclarations/derivedInterfaceIncompatibleWithBaseIndexer.ts(11,5): error TS2412: Property ''1'' of type '{ y: number; }' is not assignable to numeric index type '{ x: number; y: number; }'.
 tests/cases/conformance/interfaces/interfaceDeclarations/derivedInterfaceIncompatibleWithBaseIndexer.ts(15,5): error TS2411: Property 'foo' of type '{ y: number; }' is not assignable to string index type '{ x: number; }'.
 tests/cases/conformance/interfaces/interfaceDeclarations/derivedInterfaceIncompatibleWithBaseIndexer.ts(19,5): error TS2411: Property 'foo' of type '() => { x: number; }' is not assignable to string index type '{ x: number; }'.
-tests/cases/conformance/interfaces/interfaceDeclarations/derivedInterfaceIncompatibleWithBaseIndexer.ts(24,5): error TS2300: Duplicate identifier '1'.
 tests/cases/conformance/interfaces/interfaceDeclarations/derivedInterfaceIncompatibleWithBaseIndexer.ts(24,5): error TS2412: Property '1' of type '{ x: number; }' is not assignable to numeric index type '{ x: number; y: number; }'.
-tests/cases/conformance/interfaces/interfaceDeclarations/derivedInterfaceIncompatibleWithBaseIndexer.ts(28,5): error TS2300: Duplicate identifier ''1''.
 
 
-==== tests/cases/conformance/interfaces/interfaceDeclarations/derivedInterfaceIncompatibleWithBaseIndexer.ts (9 errors) ====
+==== tests/cases/conformance/interfaces/interfaceDeclarations/derivedInterfaceIncompatibleWithBaseIndexer.ts (7 errors) ====
     interface Base {
         [x: number]: { x: number; y: number; };
         [x: string]: { x: number; }
@@ -46,14 +44,10 @@ tests/cases/conformance/interfaces/interfaceDeclarations/derivedInterfaceIncompa
     // satisifies string indexer but not numeric indexer
     interface Derived5 extends Base {
         1: { x: number } // error
-        ~
-!!! error TS2300: Duplicate identifier '1'.
         ~~~~~~~~~~~~~~~~
 !!! error TS2412: Property '1' of type '{ x: number; }' is not assignable to numeric index type '{ x: number; y: number; }'.
     }
     
     interface Derived5 extends Base {
         '1': { x: number } // error
-        ~~~
-!!! error TS2300: Duplicate identifier ''1''.
     }

tests/baselines/reference/duplicateClassElements.errors.txt

@@ -1,4 +1,3 @@
-tests/cases/compiler/duplicateClassElements.ts(2,12): error TS2300: Duplicate identifier 'a'.
 tests/cases/compiler/duplicateClassElements.ts(3,12): error TS2300: Duplicate identifier 'a'.
 tests/cases/compiler/duplicateClassElements.ts(4,12): error TS2393: Duplicate function implementation.
 tests/cases/compiler/duplicateClassElements.ts(6,12): error TS2393: Duplicate function implementation.
@@ -15,10 +14,9 @@ tests/cases/compiler/duplicateClassElements.ts(23,9): error TS2300: Duplicate id
 tests/cases/compiler/duplicateClassElements.ts(26,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
 tests/cases/compiler/duplicateClassElements.ts(26,9): error TS2300: Duplicate identifier 'z'.
 tests/cases/compiler/duplicateClassElements.ts(29,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/duplicateClassElements.ts(29,9): error TS2300: Duplicate identifier 'x2'.
 tests/cases/compiler/duplicateClassElements.ts(32,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/duplicateClassElements.ts(32,9): error TS2300: Duplicate identifier 'x2'.
 tests/cases/compiler/duplicateClassElements.ts(34,12): error TS2300: Duplicate identifier 'x2'.
+tests/cases/compiler/duplicateClassElements.ts(34,12): error TS2403: Subsequent variable declarations must have the same type.  Variable 'x2' must be of type 'number', but here has type 'any'.
 tests/cases/compiler/duplicateClassElements.ts(36,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
 tests/cases/compiler/duplicateClassElements.ts(36,9): error TS2300: Duplicate identifier 'z2'.
 tests/cases/compiler/duplicateClassElements.ts(39,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
@@ -26,11 +24,9 @@ tests/cases/compiler/duplicateClassElements.ts(39,9): error TS2300: Duplicate id
 tests/cases/compiler/duplicateClassElements.ts(41,12): error TS2300: Duplicate identifier 'z2'.
 
 
-==== tests/cases/compiler/duplicateClassElements.ts (26 errors) ====
+==== tests/cases/compiler/duplicateClassElements.ts (24 errors) ====
     class a {
         public a;
-               ~
-!!! error TS2300: Duplicate identifier 'a'.
         public a;
                ~
 !!! error TS2300: Duplicate identifier 'a'.
@@ -90,19 +86,17 @@ tests/cases/compiler/duplicateClassElements.ts(41,12): error TS2300: Duplicate i
         get x2() {
             ~~
 !!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            ~~
-!!! error TS2300: Duplicate identifier 'x2'.
             return 10;
         }
         set x2(_x: number) {
             ~~
 !!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            ~~
-!!! error TS2300: Duplicate identifier 'x2'.
         }
         public x2;
                ~~
 !!! error TS2300: Duplicate identifier 'x2'.
+               ~~
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x2' must be of type 'number', but here has type 'any'.
     
         get z2() {
             ~~

tests/baselines/reference/duplicateIdentifierComputedName.errors.txt

@@ -0,0 +1,11 @@
+tests/cases/compiler/duplicateIdentifierComputedName.ts(3,5): error TS2300: Duplicate identifier 'a'.
+
+
+==== tests/cases/compiler/duplicateIdentifierComputedName.ts (1 errors) ====
+    class C {
+        ["a"]: string;
+        ["a"]: string;
+        ~~~~~
+!!! error TS2300: Duplicate identifier 'a'.
+    }
+    

tests/baselines/reference/duplicateIdentifierComputedName.js

@@ -0,0 +1,13 @@
+//// [duplicateIdentifierComputedName.ts]
+class C {
+    ["a"]: string;
+    ["a"]: string;
+}
+
+
+//// [duplicateIdentifierComputedName.js]
+var C = (function () {
+    function C() {
+    }
+    return C;
+}());

tests/baselines/reference/duplicateIdentifierDifferentModifiers.errors.txt

@@ -0,0 +1,37 @@
+tests/cases/compiler/duplicateIdentifierDifferentModifiers.ts(2,15): error TS2686: All declarations of 'x' must have identical modifiers.
+tests/cases/compiler/duplicateIdentifierDifferentModifiers.ts(3,15): error TS2686: All declarations of 'x' must have identical modifiers.
+tests/cases/compiler/duplicateIdentifierDifferentModifiers.ts(16,11): error TS2686: All declarations of 'y' must have identical modifiers.
+tests/cases/compiler/duplicateIdentifierDifferentModifiers.ts(20,3): error TS2686: All declarations of 'y' must have identical modifiers.
+
+
+==== tests/cases/compiler/duplicateIdentifierDifferentModifiers.ts (4 errors) ====
+    // Not OK
+    interface B { x; }
+                  ~
+!!! error TS2686: All declarations of 'x' must have identical modifiers.
+    interface B { x?; }
+                  ~
+!!! error TS2686: All declarations of 'x' must have identical modifiers.
+    
+    // OK
+    class A {
+      public y: string;
+    }
+    
+    interface A {
+      y: string;
+    }
+    
+    // Not OK
+    class C {
+      private y: string;
+              ~
+!!! error TS2686: All declarations of 'y' must have identical modifiers.
+    }
+    
+    interface C {
+      y: string;
+      ~
+!!! error TS2686: All declarations of 'y' must have identical modifiers.
+    }
+    

tests/baselines/reference/duplicateIdentifierDifferentModifiers.js

@@ -0,0 +1,37 @@
+//// [duplicateIdentifierDifferentModifiers.ts]
+// Not OK
+interface B { x; }
+interface B { x?; }
+
+// OK
+class A {
+  public y: string;
+}
+
+interface A {
+  y: string;
+}
+
+// Not OK
+class C {
+  private y: string;
+}
+
+interface C {
+  y: string;
+}
+
+
+//// [duplicateIdentifierDifferentModifiers.js]
+// OK
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+// Not OK
+var C = (function () {
+    function C() {
+    }
+    return C;
+}());

tests/baselines/reference/duplicateIdentifierDifferentSpelling.errors.txt

@@ -0,0 +1,16 @@
+tests/cases/compiler/duplicateIdentifierDifferentSpelling.ts(3,3): error TS2300: Duplicate identifier '3'.
+tests/cases/compiler/duplicateIdentifierDifferentSpelling.ts(6,21): error TS2300: Duplicate identifier '3'.
+
+
+==== tests/cases/compiler/duplicateIdentifierDifferentSpelling.ts (2 errors) ====
+    class A {
+      0b11 = '';
+      3 = '';
+      ~
+!!! error TS2300: Duplicate identifier '3'.
+    }
+    
+    var X = { 0b11: '', 3: '' };
+                        ~
+!!! error TS2300: Duplicate identifier '3'.
+    

tests/baselines/reference/duplicateIdentifierDifferentSpelling.js

@@ -0,0 +1,18 @@
+//// [duplicateIdentifierDifferentSpelling.ts]
+class A {
+  0b11 = '';
+  3 = '';
+}
+
+var X = { 0b11: '', 3: '' };
+
+
+//// [duplicateIdentifierDifferentSpelling.js]
+var A = (function () {
+    function A() {
+        this[3] = '';
+        this[3] = '';
+    }
+    return A;
+}());
+var X = { 3: '', 3: '' };

tests/baselines/reference/duplicateObjectLiteralProperty.errors.txt

@@ -1,8 +1,6 @@
-tests/cases/compiler/duplicateObjectLiteralProperty.ts(2,5): error TS2300: Duplicate identifier 'a'.
 tests/cases/compiler/duplicateObjectLiteralProperty.ts(4,5): error TS2300: Duplicate identifier 'a'.
 tests/cases/compiler/duplicateObjectLiteralProperty.ts(5,5): error TS2300: Duplicate identifier '\u0061'.
 tests/cases/compiler/duplicateObjectLiteralProperty.ts(6,5): error TS2300: Duplicate identifier 'a'.
-tests/cases/compiler/duplicateObjectLiteralProperty.ts(7,9): error TS2300: Duplicate identifier 'c'.
 tests/cases/compiler/duplicateObjectLiteralProperty.ts(8,9): error TS2300: Duplicate identifier '"c"'.
 tests/cases/compiler/duplicateObjectLiteralProperty.ts(14,9): error TS2300: Duplicate identifier 'a'.
 tests/cases/compiler/duplicateObjectLiteralProperty.ts(15,9): error TS2300: Duplicate identifier 'a'.
@@ -10,11 +8,9 @@ tests/cases/compiler/duplicateObjectLiteralProperty.ts(16,9): error TS1118: An o
 tests/cases/compiler/duplicateObjectLiteralProperty.ts(16,9): error TS2300: Duplicate identifier 'a'.
 
 
-==== tests/cases/compiler/duplicateObjectLiteralProperty.ts (10 errors) ====
+==== tests/cases/compiler/duplicateObjectLiteralProperty.ts (8 errors) ====
     var x = {
         a: 1,
-        ~
-!!! error TS2300: Duplicate identifier 'a'.
         b: true, // OK
         a: 56,   // Duplicate
         ~
@@ -26,8 +22,6 @@ tests/cases/compiler/duplicateObjectLiteralProperty.ts(16,9): error TS2300: Dupl
         ~
 !!! error TS2300: Duplicate identifier 'a'.
             c: 1,
-            ~
-!!! error TS2300: Duplicate identifier 'c'.
             "c": 56, // Duplicate
             ~~~
 !!! error TS2300: Duplicate identifier '"c"'.

tests/baselines/reference/duplicatePropertiesInStrictMode.errors.txt

@@ -1,14 +1,11 @@
-tests/cases/compiler/duplicatePropertiesInStrictMode.ts(3,3): error TS2300: Duplicate identifier 'x'.
 tests/cases/compiler/duplicatePropertiesInStrictMode.ts(4,3): error TS1117: An object literal cannot have multiple properties with the same name in strict mode.
 tests/cases/compiler/duplicatePropertiesInStrictMode.ts(4,3): error TS2300: Duplicate identifier 'x'.
 
 
-==== tests/cases/compiler/duplicatePropertiesInStrictMode.ts (3 errors) ====
+==== tests/cases/compiler/duplicatePropertiesInStrictMode.ts (2 errors) ====
     "use strict";
     var x = {
       x: 1,
-      ~
-!!! error TS2300: Duplicate identifier 'x'.
       x: 2
       ~
 !!! error TS1117: An object literal cannot have multiple properties with the same name in strict mode.

tests/baselines/reference/duplicatePropertyNames.errors.txt

@@ -2,11 +2,9 @@ tests/cases/conformance/types/members/duplicatePropertyNames.ts(4,5): error TS23
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(5,5): error TS2300: Duplicate identifier 'foo'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(14,5): error TS2300: Duplicate identifier 'foo'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(15,5): error TS2300: Duplicate identifier 'foo'.
-tests/cases/conformance/types/members/duplicatePropertyNames.ts(19,5): error TS2300: Duplicate identifier 'foo'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(20,5): error TS2300: Duplicate identifier 'foo'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(22,5): error TS2393: Duplicate function implementation.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(23,5): error TS2393: Duplicate function implementation.
-tests/cases/conformance/types/members/duplicatePropertyNames.ts(25,5): error TS2300: Duplicate identifier 'baz'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(26,5): error TS2300: Duplicate identifier 'baz'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(30,5): error TS2300: Duplicate identifier 'foo'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(31,5): error TS2300: Duplicate identifier 'foo'.
@@ -14,13 +12,11 @@ tests/cases/conformance/types/members/duplicatePropertyNames.ts(35,5): error TS2
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(36,5): error TS2300: Duplicate identifier 'foo'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(38,5): error TS2300: Duplicate identifier 'bar'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(39,5): error TS2300: Duplicate identifier 'bar'.
-tests/cases/conformance/types/members/duplicatePropertyNames.ts(43,5): error TS2300: Duplicate identifier 'foo'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(44,5): error TS2300: Duplicate identifier 'foo'.
-tests/cases/conformance/types/members/duplicatePropertyNames.ts(45,5): error TS2300: Duplicate identifier 'bar'.
 tests/cases/conformance/types/members/duplicatePropertyNames.ts(46,5): error TS2300: Duplicate identifier 'bar'.
 
 
-==== tests/cases/conformance/types/members/duplicatePropertyNames.ts (20 errors) ====
+==== tests/cases/conformance/types/members/duplicatePropertyNames.ts (16 errors) ====
     // duplicate property names are an error in all types
     
     interface Number {
@@ -48,8 +44,6 @@ tests/cases/conformance/types/members/duplicatePropertyNames.ts(46,5): error TS2
     
     class C {
         foo: string;
-        ~~~
-!!! error TS2300: Duplicate identifier 'foo'.
         foo: string;
         ~~~
 !!! error TS2300: Duplicate identifier 'foo'.
@@ -62,8 +56,6 @@ tests/cases/conformance/types/members/duplicatePropertyNames.ts(46,5): error TS2
 !!! error TS2393: Duplicate function implementation.
     
         baz = () => { }
-        ~~~
-!!! error TS2300: Duplicate identifier 'baz'.
         baz = () => { }
         ~~~
 !!! error TS2300: Duplicate identifier 'baz'.
@@ -96,14 +88,10 @@ tests/cases/conformance/types/members/duplicatePropertyNames.ts(46,5): error TS2
     
     var b = {
         foo: '',
-        ~~~
-!!! error TS2300: Duplicate identifier 'foo'.
         foo: '',
         ~~~
 !!! error TS2300: Duplicate identifier 'foo'.
         bar: () => { },
-        ~~~
-!!! error TS2300: Duplicate identifier 'bar'.
         bar: () => { }
         ~~~
 !!! error TS2300: Duplicate identifier 'bar'.

tests/baselines/reference/duplicateStringNamedProperty1.errors.txt

@@ -1,4 +1,4 @@
-tests/cases/compiler/duplicateStringNamedProperty1.ts(2,5): error TS2300: Duplicate identifier '"artist"'.
+tests/cases/compiler/duplicateStringNamedProperty1.ts(2,5): error TS2300: Duplicate identifier 'artist'.
 tests/cases/compiler/duplicateStringNamedProperty1.ts(3,5): error TS2300: Duplicate identifier 'artist'.
 
 
@@ -6,7 +6,7 @@ tests/cases/compiler/duplicateStringNamedProperty1.ts(3,5): error TS2300: Duplic
     export interface Album {
         "artist": string;
         ~~~~~~~~
-!!! error TS2300: Duplicate identifier '"artist"'.
+!!! error TS2300: Duplicate identifier 'artist'.
         artist: string;
         ~~~~~~
 !!! error TS2300: Duplicate identifier 'artist'.

tests/baselines/reference/gettersAndSettersErrors.errors.txt

@@ -1,8 +1,7 @@
 tests/cases/compiler/gettersAndSettersErrors.ts(2,16): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/gettersAndSettersErrors.ts(2,16): error TS2300: Duplicate identifier 'Foo'.
 tests/cases/compiler/gettersAndSettersErrors.ts(3,16): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/gettersAndSettersErrors.ts(3,16): error TS2300: Duplicate identifier 'Foo'.
 tests/cases/compiler/gettersAndSettersErrors.ts(5,12): error TS2300: Duplicate identifier 'Foo'.
+tests/cases/compiler/gettersAndSettersErrors.ts(5,12): error TS2403: Subsequent variable declarations must have the same type.  Variable 'Foo' must be of type 'string', but here has type 'number'.
 tests/cases/compiler/gettersAndSettersErrors.ts(6,16): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
 tests/cases/compiler/gettersAndSettersErrors.ts(7,16): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
 tests/cases/compiler/gettersAndSettersErrors.ts(11,17): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
@@ -11,22 +10,20 @@ tests/cases/compiler/gettersAndSettersErrors.ts(12,16): error TS1056: Accessors
 tests/cases/compiler/gettersAndSettersErrors.ts(12,16): error TS2379: Getter and setter accessors do not agree in visibility.
 
 
-==== tests/cases/compiler/gettersAndSettersErrors.ts (11 errors) ====
+==== tests/cases/compiler/gettersAndSettersErrors.ts (10 errors) ====
     class C {
         public get Foo() { return "foo";} // ok
                    ~~~
 !!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-                   ~~~
-!!! error TS2300: Duplicate identifier 'Foo'.
         public set Foo(foo:string) {} // ok
                    ~~~
 !!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-                   ~~~
-!!! error TS2300: Duplicate identifier 'Foo'.
     
         public Foo = 0; // error - duplicate identifier Foo - confirmed
                ~~~
 !!! error TS2300: Duplicate identifier 'Foo'.
+               ~~~
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'Foo' must be of type 'string', but here has type 'number'.
         public get Goo(v:string):string {return null;} // error - getters must not have a parameter
                    ~~~
 !!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.

tests/baselines/reference/interfaceDeclaration1.errors.txt

@@ -2,6 +2,7 @@ tests/cases/compiler/interfaceDeclaration1.ts(2,5): error TS2300: Duplicate iden
 tests/cases/compiler/interfaceDeclaration1.ts(3,5): error TS2300: Duplicate identifier 'item'.
 tests/cases/compiler/interfaceDeclaration1.ts(7,5): error TS2300: Duplicate identifier 'item'.
 tests/cases/compiler/interfaceDeclaration1.ts(8,5): error TS2300: Duplicate identifier 'item'.
+tests/cases/compiler/interfaceDeclaration1.ts(8,5): error TS2403: Subsequent variable declarations must have the same type.  Variable 'item' must be of type 'any', but here has type 'number'.
 tests/cases/compiler/interfaceDeclaration1.ts(22,11): error TS2310: Type 'I5' recursively references itself as a base type.
 tests/cases/compiler/interfaceDeclaration1.ts(35,7): error TS2420: Class 'C1' incorrectly implements interface 'I3'.
   Property 'prototype' is missing in type 'C1'.
@@ -10,7 +11,7 @@ tests/cases/compiler/interfaceDeclaration1.ts(52,11): error TS2320: Interface 'i
   Named property 'foo' of types 'i10' and 'i11' are not identical.
 
 
-==== tests/cases/compiler/interfaceDeclaration1.ts (8 errors) ====
+==== tests/cases/compiler/interfaceDeclaration1.ts (9 errors) ====
     interface I1 {
         item:number;
         ~~~~
@@ -27,6 +28,8 @@ tests/cases/compiler/interfaceDeclaration1.ts(52,11): error TS2320: Interface 'i
         item:number;
         ~~~~
 !!! error TS2300: Duplicate identifier 'item'.
+        ~~~~
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'item' must be of type 'any', but here has type 'number'.
     }
     
     interface I3 {

tests/baselines/reference/jsFileCompilationBindMultipleDefaultExports.errors.txt

@@ -1,15 +1,9 @@
-tests/cases/compiler/a.js(1,22): error TS2528: A module cannot have multiple default exports.
-tests/cases/compiler/a.js(3,1): error TS2528: A module cannot have multiple default exports.
 tests/cases/compiler/a.js(3,16): error TS1109: Expression expected.
 
 
-==== tests/cases/compiler/a.js (3 errors) ====
+==== tests/cases/compiler/a.js (1 errors) ====
     export default class a {
-                         ~
-!!! error TS2528: A module cannot have multiple default exports.
     }
     export default var a = 10;
-    ~~~~~~~~~~~~~~
-!!! error TS2528: A module cannot have multiple default exports.
                    ~~~
 !!! error TS1109: Expression expected.

tests/baselines/reference/jsFileCompilationBindStrictModeErrors.errors.txt

@@ -1,6 +1,4 @@
-tests/cases/compiler/a.js(3,5): error TS2300: Duplicate identifier 'a'.
 tests/cases/compiler/a.js(5,5): error TS1117: An object literal cannot have multiple properties with the same name in strict mode.
-tests/cases/compiler/a.js(5,5): error TS2300: Duplicate identifier 'a'.
 tests/cases/compiler/a.js(7,5): error TS1212: Identifier expected. 'let' is a reserved word in strict mode
 tests/cases/compiler/a.js(8,8): error TS1102: 'delete' cannot be called on an identifier in strict mode.
 tests/cases/compiler/a.js(10,10): error TS1100: Invalid use of 'eval' in strict mode.
@@ -14,18 +12,14 @@ tests/cases/compiler/d.js(2,9): error TS1121: Octal literals are not allowed in
 tests/cases/compiler/d.js(2,11): error TS1005: ',' expected.
 
 
-==== tests/cases/compiler/a.js (8 errors) ====
+==== tests/cases/compiler/a.js (6 errors) ====
     "use strict";
     var a = {
         a: "hello", // error
-        ~
-!!! error TS2300: Duplicate identifier 'a'.
         b: 10,
         a: 10 // error
         ~
 !!! error TS1117: An object literal cannot have multiple properties with the same name in strict mode.
-        ~
-!!! error TS2300: Duplicate identifier 'a'.
     };
     var let = 10; // error
         ~~~

tests/baselines/reference/lastPropertyInLiteralWins.errors.txt

@@ -3,13 +3,11 @@ tests/cases/compiler/lastPropertyInLiteralWins.ts(7,6): error TS2345: Argument o
     Type '(num: number) => void' is not assignable to type '(str: string) => void'.
       Types of parameters 'num' and 'str' are incompatible.
         Type 'string' is not assignable to type 'number'.
-tests/cases/compiler/lastPropertyInLiteralWins.ts(8,5): error TS2300: Duplicate identifier 'thunk'.
 tests/cases/compiler/lastPropertyInLiteralWins.ts(9,5): error TS2300: Duplicate identifier 'thunk'.
-tests/cases/compiler/lastPropertyInLiteralWins.ts(13,5): error TS2300: Duplicate identifier 'thunk'.
 tests/cases/compiler/lastPropertyInLiteralWins.ts(14,5): error TS2300: Duplicate identifier 'thunk'.
 
 
-==== tests/cases/compiler/lastPropertyInLiteralWins.ts (5 errors) ====
+==== tests/cases/compiler/lastPropertyInLiteralWins.ts (3 errors) ====
     interface Thing {
         thunk: (str: string) => void;
     }
@@ -20,8 +18,6 @@ tests/cases/compiler/lastPropertyInLiteralWins.ts(14,5): error TS2300: Duplicate
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
         thunk: (str: string) => {},
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-        ~~~~~
-!!! error TS2300: Duplicate identifier 'thunk'.
         thunk: (num: number) => {}
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
         ~~~~~
@@ -36,8 +32,6 @@ tests/cases/compiler/lastPropertyInLiteralWins.ts(14,5): error TS2300: Duplicate
     
     test({ // Should be OK.  Last 'thunk' is of correct type
         thunk: (num: number) => {},
-        ~~~~~
-!!! error TS2300: Duplicate identifier 'thunk'.
         thunk: (str: string) => {}
         ~~~~~
 !!! error TS2300: Duplicate identifier 'thunk'.

tests/baselines/reference/memberOverride.errors.txt

@@ -1,14 +1,11 @@
-tests/cases/compiler/memberOverride.ts(4,5): error TS2300: Duplicate identifier 'a'.
 tests/cases/compiler/memberOverride.ts(5,5): error TS2300: Duplicate identifier 'a'.
 
 
-==== tests/cases/compiler/memberOverride.ts (2 errors) ====
+==== tests/cases/compiler/memberOverride.ts (1 errors) ====
     // An object initialiser accepts the first definition for the same property with a different type signature
     // Should compile, since the second declaration of a overrides the first
     var x = {
         a: "", 
-        ~
-!!! error TS2300: Duplicate identifier 'a'.
         a: 5
         ~
 !!! error TS2300: Duplicate identifier 'a'.

tests/baselines/reference/mergedInterfacesWithConflictingPropertyNames.errors.txt

@@ -1,35 +1,28 @@
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts(2,5): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts(6,5): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts(11,9): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts(15,9): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts(33,9): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts(39,9): error TS2300: Duplicate identifier 'x'.
+tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts(6,5): error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'string', but here has type 'number'.
+tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts(15,9): error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'T', but here has type 'number'.
+tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts(39,9): error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'T', but here has type 'number'.
 
 
-==== tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts (6 errors) ====
+==== tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames.ts (3 errors) ====
     interface A {
         x: string; // error
-        ~
-!!! error TS2300: Duplicate identifier 'x'.
     }
     
     interface A {
         x: number;
         ~
-!!! error TS2300: Duplicate identifier 'x'.
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'string', but here has type 'number'.
     }
     
     module M {
         interface A<T> {
             x: T;
-            ~
-!!! error TS2300: Duplicate identifier 'x'.
         }
     
         interface A<T> {
             x: number;  // error
             ~
-!!! error TS2300: Duplicate identifier 'x'.
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'T', but here has type 'number'.
         }
     }
     
@@ -48,8 +41,6 @@ tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConfli
     module M3 {
         export interface A<T> {
             x: T;
-            ~
-!!! error TS2300: Duplicate identifier 'x'.
         }
     }
     
@@ -57,6 +48,6 @@ tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConfli
         export interface A<T> {
             x: number;  // error
             ~
-!!! error TS2300: Duplicate identifier 'x'.
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'T', but here has type 'number'.
         }
     }

tests/baselines/reference/mergedInterfacesWithConflictingPropertyNames2.errors.txt

@@ -1,62 +0,0 @@
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames2.ts(2,5): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames2.ts(6,5): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames2.ts(11,9): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames2.ts(15,9): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames2.ts(33,9): error TS2300: Duplicate identifier 'x'.
-tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames2.ts(39,9): error TS2300: Duplicate identifier 'x'.
-
-
-==== tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames2.ts (6 errors) ====
-    interface A {
-        x: string; // error
-        ~
-!!! error TS2300: Duplicate identifier 'x'.
-    }
-    
-    interface A {
-        x: string; // error
-        ~
-!!! error TS2300: Duplicate identifier 'x'.
-    }
-    
-    module M {
-        interface A<T> {
-            x: T;
-            ~
-!!! error TS2300: Duplicate identifier 'x'.
-        }
-    
-        interface A<T> {
-            x: T;  // error
-            ~
-!!! error TS2300: Duplicate identifier 'x'.
-        }
-    }
-    
-    module M2 {
-        interface A<T> {
-            x: T;
-        }   
-    }
-    
-    module M2 {
-        interface A<T> {
-            x: T;  // ok, different declaration space than other M2
-        }
-    }
-    
-    module M3 {
-        export interface A<T> {
-            x: T;
-            ~
-!!! error TS2300: Duplicate identifier 'x'.
-        }
-    }
-    
-    module M3 {
-        export interface A<T> {
-            x: T;  // error
-            ~
-!!! error TS2300: Duplicate identifier 'x'.
-        }
-    }

tests/baselines/reference/mergedInterfacesWithConflictingPropertyNames2.symbols

@@ -0,0 +1,88 @@
+=== tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames2.ts ===
+interface A {
+>A : Symbol(A, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 0, 0), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 2, 1))
+
+    x: string; // error
+>x : Symbol(A.x, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 0, 13), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 4, 13))
+}
+
+interface A {
+>A : Symbol(A, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 0, 0), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 2, 1))
+
+    x: string; // error
+>x : Symbol(A.x, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 0, 13), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 4, 13))
+}
+
+module M {
+>M : Symbol(M, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 6, 1))
+
+    interface A<T> {
+>A : Symbol(A, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 8, 10), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 11, 5))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 9, 16), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 13, 16))
+
+        x: T;
+>x : Symbol(A.x, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 9, 20), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 13, 20))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 9, 16), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 13, 16))
+    }
+
+    interface A<T> {
+>A : Symbol(A, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 8, 10), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 11, 5))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 9, 16), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 13, 16))
+
+        x: T;  // error
+>x : Symbol(A.x, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 9, 20), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 13, 20))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 9, 16), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 13, 16))
+    }
+}
+
+module M2 {
+>M2 : Symbol(M2, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 16, 1), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 22, 1))
+
+    interface A<T> {
+>A : Symbol(A, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 18, 11))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 19, 16))
+
+        x: T;
+>x : Symbol(A.x, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 19, 20))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 19, 16))
+    }   
+}
+
+module M2 {
+>M2 : Symbol(M2, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 16, 1), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 22, 1))
+
+    interface A<T> {
+>A : Symbol(A, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 24, 11))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 25, 16))
+
+        x: T;  // ok, different declaration space than other M2
+>x : Symbol(A.x, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 25, 20))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 25, 16))
+    }
+}
+
+module M3 {
+>M3 : Symbol(M3, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 28, 1), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 34, 1))
+
+    export interface A<T> {
+>A : Symbol(A, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 30, 11), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 36, 11))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 31, 23), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 37, 23))
+
+        x: T;
+>x : Symbol(A.x, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 31, 27), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 37, 27))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 31, 23), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 37, 23))
+    }
+}
+
+module M3 {
+>M3 : Symbol(M3, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 28, 1), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 34, 1))
+
+    export interface A<T> {
+>A : Symbol(A, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 30, 11), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 36, 11))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 31, 23), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 37, 23))
+
+        x: T;  // error
+>x : Symbol(A.x, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 31, 27), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 37, 27))
+>T : Symbol(T, Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 31, 23), Decl(mergedInterfacesWithConflictingPropertyNames2.ts, 37, 23))
+    }
+}

tests/baselines/reference/mergedInterfacesWithConflictingPropertyNames2.types

@@ -0,0 +1,88 @@
+=== tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithConflictingPropertyNames2.ts ===
+interface A {
+>A : A
+
+    x: string; // error
+>x : string
+}
+
+interface A {
+>A : A
+
+    x: string; // error
+>x : string
+}
+
+module M {
+>M : any
+
+    interface A<T> {
+>A : A<T>
+>T : T
+
+        x: T;
+>x : T
+>T : T
+    }
+
+    interface A<T> {
+>A : A<T>
+>T : T
+
+        x: T;  // error
+>x : T
+>T : T
+    }
+}
+
+module M2 {
+>M2 : any
+
+    interface A<T> {
+>A : A<T>
+>T : T
+
+        x: T;
+>x : T
+>T : T
+    }   
+}
+
+module M2 {
+>M2 : any
+
+    interface A<T> {
+>A : A<T>
+>T : T
+
+        x: T;  // ok, different declaration space than other M2
+>x : T
+>T : T
+    }
+}
+
+module M3 {
+>M3 : any
+
+    export interface A<T> {
+>A : A<T>
+>T : T
+
+        x: T;
+>x : T
+>T : T
+    }
+}
+
+module M3 {
+>M3 : any
+
+    export interface A<T> {
+>A : A<T>
+>T : T
+
+        x: T;  // error
+>x : T
+>T : T
+    }
+}

tests/baselines/reference/multipleDefaultExports01.errors.txt

@@ -1,13 +1,16 @@
+tests/cases/conformance/es6/modules/m1.ts(2,22): error TS2323: Cannot redeclare exported variable 'default'.
 tests/cases/conformance/es6/modules/m1.ts(2,22): error TS2528: A module cannot have multiple default exports.
 tests/cases/conformance/es6/modules/m1.ts(6,25): error TS2528: A module cannot have multiple default exports.
-tests/cases/conformance/es6/modules/m1.ts(11,1): error TS2528: A module cannot have multiple default exports.
+tests/cases/conformance/es6/modules/m1.ts(11,1): error TS2323: Cannot redeclare exported variable 'default'.
 tests/cases/conformance/es6/modules/m2.ts(3,1): error TS2348: Value of type 'typeof foo' is not callable. Did you mean to include 'new'?
 
 
-==== tests/cases/conformance/es6/modules/m1.ts (3 errors) ====
+==== tests/cases/conformance/es6/modules/m1.ts (4 errors) ====
     
     export default class foo {
                          ~~~
+!!! error TS2323: Cannot redeclare exported variable 'default'.
+                         ~~~
 !!! error TS2528: A module cannot have multiple default exports.
     
     }
@@ -21,7 +24,7 @@ tests/cases/conformance/es6/modules/m2.ts(3,1): error TS2348: Value of type 'typ
     var x = 10;
     export default x;
     ~~~~~~~~~~~~~~~~~
-!!! error TS2528: A module cannot have multiple default exports.
+!!! error TS2323: Cannot redeclare exported variable 'default'.
     
 ==== tests/cases/conformance/es6/modules/m2.ts (1 errors) ====
     import Entity from "./m1"

tests/baselines/reference/numericClassMembers1.errors.txt

@@ -1,26 +1,20 @@
-tests/cases/compiler/numericClassMembers1.ts(2,3): error TS2300: Duplicate identifier '0'.
-tests/cases/compiler/numericClassMembers1.ts(3,3): error TS2300: Duplicate identifier '0.0'.
-tests/cases/compiler/numericClassMembers1.ts(7,3): error TS2300: Duplicate identifier '0.0'.
-tests/cases/compiler/numericClassMembers1.ts(8,2): error TS2300: Duplicate identifier ''0''.
+tests/cases/compiler/numericClassMembers1.ts(3,3): error TS2300: Duplicate identifier '0'.
+tests/cases/compiler/numericClassMembers1.ts(8,2): error TS2300: Duplicate identifier '0'.
 
 
-==== tests/cases/compiler/numericClassMembers1.ts (4 errors) ====
+==== tests/cases/compiler/numericClassMembers1.ts (2 errors) ====
     class C234 {
       0 = 1; 
-      ~
-!!! error TS2300: Duplicate identifier '0'.
       0.0 = 2;
       ~~~
-!!! error TS2300: Duplicate identifier '0.0'.
+!!! error TS2300: Duplicate identifier '0'.
     }
      
     class C235 { 
       0.0 = 1;
-      ~~~
-!!! error TS2300: Duplicate identifier '0.0'.
      '0' = 2;
      ~~~
-!!! error TS2300: Duplicate identifier ''0''.
+!!! error TS2300: Duplicate identifier '0'.
     }
     
     class C236 {

tests/baselines/reference/numericNamedPropertyDuplicates.errors.txt

@@ -1,27 +1,19 @@
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(2,5): error TS2300: Duplicate identifier '1'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(3,5): error TS2300: Duplicate identifier '1.0'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(4,12): error TS2300: Duplicate identifier '2'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(3,5): error TS2300: Duplicate identifier '1'.
 tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(5,12): error TS2300: Duplicate identifier '2'.
 tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(9,5): error TS2300: Duplicate identifier '2'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(10,5): error TS2300: Duplicate identifier '2.'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(10,5): error TS2300: Duplicate identifier '2'.
 tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(14,5): error TS2300: Duplicate identifier '1'.
 tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(15,5): error TS2300: Duplicate identifier '1'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(19,5): error TS2300: Duplicate identifier '2'.
 tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(20,5): error TS1005: ',' expected.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts(20,5): error TS2300: Duplicate identifier '2'.
 
 
-==== tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts (11 errors) ====
+==== tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedPropertyDuplicates.ts (7 errors) ====
     class C {
         1: number;
-        ~
-!!! error TS2300: Duplicate identifier '1'.
         1.0: number;
         ~~~
-!!! error TS2300: Duplicate identifier '1.0'.
+!!! error TS2300: Duplicate identifier '1'.
         static 2: number;
-               ~
-!!! error TS2300: Duplicate identifier '2'.
         static 2: number;
                ~
 !!! error TS2300: Duplicate identifier '2'.
@@ -33,7 +25,7 @@ tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedP
 !!! error TS2300: Duplicate identifier '2'.
         2.: number;
         ~~
-!!! error TS2300: Duplicate identifier '2.'.
+!!! error TS2300: Duplicate identifier '2'.
     }
     
     var a: {
@@ -47,11 +39,7 @@ tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericNamedP
     
     var b = {
         2: 1
-        ~
-!!! error TS2300: Duplicate identifier '2'.
         2: 1
         ~
 !!! error TS1005: ',' expected.
-        ~
-!!! error TS2300: Duplicate identifier '2'.
     }

tests/baselines/reference/numericStringNamedPropertyEquivalence.errors.txt

@@ -1,30 +1,27 @@
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(4,5): error TS2300: Duplicate identifier '"1"'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(6,5): error TS2300: Duplicate identifier '1.0'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(10,5): error TS2300: Duplicate identifier '"1"'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(6,5): error TS2300: Duplicate identifier '1'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(10,5): error TS2300: Duplicate identifier '1'.
 tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(12,5): error TS2300: Duplicate identifier '1'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(16,5): error TS2300: Duplicate identifier '"1"'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(17,5): error TS2300: Duplicate identifier '1.0'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(21,5): error TS2300: Duplicate identifier '"0"'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(16,5): error TS2300: Duplicate identifier '1'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(17,5): error TS2300: Duplicate identifier '1'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(17,5): error TS2403: Subsequent variable declarations must have the same type.  Variable '1.0' must be of type 'number', but here has type 'string'.
 tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts(22,5): error TS2300: Duplicate identifier '0'.
 
 
-==== tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts (8 errors) ====
+==== tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericStringNamedPropertyEquivalence.ts (7 errors) ====
     // Each of these types has an error in it. 
     // String named and numeric named properties conflict if they would be equivalent after ToNumber on the property name.
     class C {
         "1": number;
-        ~~~
-!!! error TS2300: Duplicate identifier '"1"'.
         "1.0": number; // not a duplicate
         1.0: number;
         ~~~
-!!! error TS2300: Duplicate identifier '1.0'.
+!!! error TS2300: Duplicate identifier '1'.
     }
     
     interface I {
         "1": number;
         ~~~
-!!! error TS2300: Duplicate identifier '"1"'.
+!!! error TS2300: Duplicate identifier '1'.
         "1.": number; // not a duplicate
         1: number;
         ~
@@ -34,16 +31,16 @@ tests/cases/conformance/types/objectTypeLiteral/propertySignatures/numericString
     var a: {
         "1": number;
         ~~~
-!!! error TS2300: Duplicate identifier '"1"'.
+!!! error TS2300: Duplicate identifier '1'.
         1.0: string;
         ~~~
-!!! error TS2300: Duplicate identifier '1.0'.
+!!! error TS2300: Duplicate identifier '1'.
+        ~~~
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable '1.0' must be of type 'number', but here has type 'string'.
     }
     
     var b = {
         "0": '',
-        ~~~
-!!! error TS2300: Duplicate identifier '"0"'.
         0: ''
         ~
 !!! error TS2300: Duplicate identifier '0'.

tests/baselines/reference/objectLiteralErrors.errors.txt

@@ -1,39 +1,21 @@
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(3,12): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(3,18): error TS2300: Duplicate identifier 'a'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(4,12): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(4,19): error TS2300: Duplicate identifier 'a'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(5,12): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(5,18): error TS2300: Duplicate identifier 'a'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(6,12): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(6,21): error TS2300: Duplicate identifier 'a'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(7,12): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(7,19): error TS2300: Duplicate identifier 'a'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(8,12): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(8,18): error TS2300: Duplicate identifier ''a''.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(9,12): error TS2300: Duplicate identifier ''a''.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(9,20): error TS2300: Duplicate identifier 'a'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(10,12): error TS2300: Duplicate identifier ''a''.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(10,20): error TS2300: Duplicate identifier '"a"'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(11,12): error TS2300: Duplicate identifier ''a''.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(11,20): error TS2300: Duplicate identifier ''a''.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(12,13): error TS2300: Duplicate identifier '"a"'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(12,21): error TS2300: Duplicate identifier ''a''.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(13,13): error TS2300: Duplicate identifier '1.0'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(13,21): error TS2300: Duplicate identifier ''1''.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(14,13): error TS2300: Duplicate identifier '0'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(14,19): error TS2300: Duplicate identifier '0'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(15,13): error TS2300: Duplicate identifier '0'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(15,19): error TS2300: Duplicate identifier '0'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(16,13): error TS2300: Duplicate identifier '0'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(16,19): error TS2300: Duplicate identifier '0x0'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(17,13): error TS2300: Duplicate identifier '0'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(17,19): error TS1085: Octal literals are not available when targeting ECMAScript 5 and higher.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(17,19): error TS2300: Duplicate identifier '000'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(18,13): error TS2300: Duplicate identifier '"100"'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(18,23): error TS2300: Duplicate identifier '1e2'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(19,13): error TS2300: Duplicate identifier '0x20'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(19,22): error TS2300: Duplicate identifier '3.2e1'.
-tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(20,13): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(20,25): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(23,12): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(23,22): error TS1119: An object literal cannot have property and accessor with the same name.
@@ -96,99 +78,63 @@ tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(45,16)
 tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts(45,55): error TS2380: 'get' and 'set' accessor must have the same type.
 
 
-==== tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts (96 errors) ====
+==== tests/cases/conformance/expressions/objectLiterals/objectLiteralErrors.ts (78 errors) ====
     
     // Multiple properties with the same name
     var e1 = { a: 0, a: 0 };
-               ~
-!!! error TS2300: Duplicate identifier 'a'.
                      ~
 !!! error TS2300: Duplicate identifier 'a'.
     var e2 = { a: '', a: '' };
-               ~
-!!! error TS2300: Duplicate identifier 'a'.
                       ~
 !!! error TS2300: Duplicate identifier 'a'.
     var e3 = { a: 0, a: '' };
-               ~
-!!! error TS2300: Duplicate identifier 'a'.
                      ~
 !!! error TS2300: Duplicate identifier 'a'.
     var e4 = { a: true, a: false };
-               ~
-!!! error TS2300: Duplicate identifier 'a'.
                         ~
 !!! error TS2300: Duplicate identifier 'a'.
     var e5 = { a: {}, a: {} };
-               ~
-!!! error TS2300: Duplicate identifier 'a'.
                       ~
 !!! error TS2300: Duplicate identifier 'a'.
     var e6 = { a: 0, 'a': 0 };
-               ~
-!!! error TS2300: Duplicate identifier 'a'.
                      ~~~
 !!! error TS2300: Duplicate identifier ''a''.
     var e7 = { 'a': 0, a: 0 };
-               ~~~
-!!! error TS2300: Duplicate identifier ''a''.
                        ~
 !!! error TS2300: Duplicate identifier 'a'.
     var e8 = { 'a': 0, "a": 0 };
-               ~~~
-!!! error TS2300: Duplicate identifier ''a''.
                        ~~~
 !!! error TS2300: Duplicate identifier '"a"'.
     var e9 = { 'a': 0, 'a': 0 };
-               ~~~
-!!! error TS2300: Duplicate identifier ''a''.
                        ~~~
 !!! error TS2300: Duplicate identifier ''a''.
     var e10 = { "a": 0, 'a': 0 };
-                ~~~
-!!! error TS2300: Duplicate identifier '"a"'.
                         ~~~
 !!! error TS2300: Duplicate identifier ''a''.
     var e11 = { 1.0: 0, '1': 0 };
-                ~~~
-!!! error TS2300: Duplicate identifier '1.0'.
                         ~~~
 !!! error TS2300: Duplicate identifier ''1''.
     var e12 = { 0: 0, 0: 0 };
-                ~
-!!! error TS2300: Duplicate identifier '0'.
                       ~
 !!! error TS2300: Duplicate identifier '0'.
     var e13 = { 0: 0, 0: 0 };
-                ~
-!!! error TS2300: Duplicate identifier '0'.
                       ~
 !!! error TS2300: Duplicate identifier '0'.
     var e14 = { 0: 0, 0x0: 0 };
-                ~
-!!! error TS2300: Duplicate identifier '0'.
                       ~~~
 !!! error TS2300: Duplicate identifier '0x0'.
     var e14 = { 0: 0, 000: 0 };
-                ~
-!!! error TS2300: Duplicate identifier '0'.
                       ~~~
 !!! error TS1085: Octal literals are not available when targeting ECMAScript 5 and higher.
                       ~~~
 !!! error TS2300: Duplicate identifier '000'.
     var e15 = { "100": 0, 1e2: 0 };
-                ~~~~~
-!!! error TS2300: Duplicate identifier '"100"'.
                           ~~~
 !!! error TS2300: Duplicate identifier '1e2'.
     var e16 = { 0x20: 0, 3.2e1: 0 };
-                ~~~~
-!!! error TS2300: Duplicate identifier '0x20'.
                          ~~~~~
 !!! error TS2300: Duplicate identifier '3.2e1'.
     var e17 = { a: 0, b: 1, a: 0 };
-                ~
-!!! error TS2300: Duplicate identifier 'a'.
                             ~
 !!! error TS2300: Duplicate identifier 'a'.
     

tests/baselines/reference/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.errors.txt

@@ -7,16 +7,13 @@ tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPr
 tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts(9,8): error TS1005: ':' expected.
 tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts(10,10): error TS1005: ':' expected.
 tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts(12,1): error TS1005: ':' expected.
-tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts(15,5): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts(15,6): error TS1005: ':' expected.
-tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts(16,5): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts(16,6): error TS1005: ':' expected.
-tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts(17,5): error TS2300: Duplicate identifier 'a'.
 tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts(17,6): error TS1005: ':' expected.
 tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts(20,17): error TS1005: ':' expected.
 
 
-==== tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts (16 errors) ====
+==== tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPropertiesErrorFromNotUsingIdentifier.ts (13 errors) ====
     // errors
     var y = {
         "stringLiteral",
@@ -50,18 +47,12 @@ tests/cases/conformance/es6/shorthandPropertyAssignment/objectLiteralShorthandPr
     
     var x = {
         a.b,
-        ~
-!!! error TS2300: Duplicate identifier 'a'.
          ~
 !!! error TS1005: ':' expected.
         a["ss"],
-        ~
-!!! error TS2300: Duplicate identifier 'a'.
          ~
 !!! error TS1005: ':' expected.
         a[1],
-        ~
-!!! error TS2300: Duplicate identifier 'a'.
          ~
 !!! error TS1005: ':' expected.
     };

tests/baselines/reference/objectTypeWithDuplicateNumericProperty.errors.txt

@@ -1,38 +1,34 @@
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(5,5): error TS2300: Duplicate identifier '1'.
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(6,5): error TS2300: Duplicate identifier '1.0'.
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(7,5): error TS2300: Duplicate identifier '1.'.
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(8,5): error TS2300: Duplicate identifier '1.00'.
+tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(6,5): error TS2300: Duplicate identifier '1'.
+tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(7,5): error TS2300: Duplicate identifier '1'.
+tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(8,5): error TS2300: Duplicate identifier '1'.
 tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(12,5): error TS2300: Duplicate identifier '1'.
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(13,5): error TS2300: Duplicate identifier '1.0'.
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(14,5): error TS2300: Duplicate identifier '1.'.
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(15,5): error TS2300: Duplicate identifier '1.00'.
+tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(13,5): error TS2300: Duplicate identifier '1'.
+tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(14,5): error TS2300: Duplicate identifier '1'.
+tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(15,5): error TS2300: Duplicate identifier '1'.
 tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(19,5): error TS2300: Duplicate identifier '1'.
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(20,5): error TS2300: Duplicate identifier '1.0'.
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(21,5): error TS2300: Duplicate identifier '1.'.
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(22,5): error TS2300: Duplicate identifier '1.00'.
-tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(26,5): error TS2300: Duplicate identifier '1'.
+tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(20,5): error TS2300: Duplicate identifier '1'.
+tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(21,5): error TS2300: Duplicate identifier '1'.
+tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(22,5): error TS2300: Duplicate identifier '1'.
 tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(27,5): error TS2300: Duplicate identifier '1.0'.
 tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(28,5): error TS2300: Duplicate identifier '1.'.
 tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(29,5): error TS2300: Duplicate identifier '1.00'.
 
 
-==== tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts (16 errors) ====
+==== tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts (14 errors) ====
     // numeric properties must be distinct after a ToNumber operation
     // so the below are all errors
     
     class C {
         1;
-        ~
-!!! error TS2300: Duplicate identifier '1'.
         1.0;
         ~~~
-!!! error TS2300: Duplicate identifier '1.0'.
+!!! error TS2300: Duplicate identifier '1'.
         1.;
         ~~
-!!! error TS2300: Duplicate identifier '1.'.
+!!! error TS2300: Duplicate identifier '1'.
         1.00;
         ~~~~
-!!! error TS2300: Duplicate identifier '1.00'.
+!!! error TS2300: Duplicate identifier '1'.
     }
     
     interface I {
@@ -41,13 +37,13 @@ tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(
 !!! error TS2300: Duplicate identifier '1'.
         1.0;
         ~~~
-!!! error TS2300: Duplicate identifier '1.0'.
+!!! error TS2300: Duplicate identifier '1'.
         1.;
         ~~
-!!! error TS2300: Duplicate identifier '1.'.
+!!! error TS2300: Duplicate identifier '1'.
         1.00;
         ~~~~
-!!! error TS2300: Duplicate identifier '1.00'.
+!!! error TS2300: Duplicate identifier '1'.
     }
     
     var a: {
@@ -56,19 +52,17 @@ tests/cases/conformance/types/members/objectTypeWithDuplicateNumericProperty.ts(
 !!! error TS2300: Duplicate identifier '1'.
         1.0;
         ~~~
-!!! error TS2300: Duplicate identifier '1.0'.
+!!! error TS2300: Duplicate identifier '1'.
         1.;
         ~~
-!!! error TS2300: Duplicate identifier '1.'.
+!!! error TS2300: Duplicate identifier '1'.
         1.00;
         ~~~~
-!!! error TS2300: Duplicate identifier '1.00'.
+!!! error TS2300: Duplicate identifier '1'.
     }
     
     var b = {
         1: 1,
-        ~
-!!! error TS2300: Duplicate identifier '1'.
         1.0: 1,
         ~~~
 !!! error TS2300: Duplicate identifier '1.0'.

tests/baselines/reference/octalIntegerLiteralError.errors.txt

@@ -1,11 +1,8 @@
 tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/octalIntegerLiteralError.ts(2,19): error TS1005: ',' expected.
 tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/octalIntegerLiteralError.ts(3,18): error TS1005: ',' expected.
-tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/octalIntegerLiteralError.ts(6,5): error TS2300: Duplicate identifier '0O45436'.
-tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/octalIntegerLiteralError.ts(7,5): error TS2300: Duplicate identifier '19230'.
-tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/octalIntegerLiteralError.ts(8,5): error TS2300: Duplicate identifier '"19230"'.
 
 
-==== tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/octalIntegerLiteralError.ts (5 errors) ====
+==== tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/octalIntegerLiteralError.ts (2 errors) ====
     // error
     var oct1 = 0O13334823;
                       ~~~
@@ -16,13 +13,7 @@ tests/cases/conformance/es6/binaryAndOctalIntegerLiteral/octalIntegerLiteralErro
     
     var obj1 = {
         0O45436: "hi",
-        ~~~~~~~
-!!! error TS2300: Duplicate identifier '0O45436'.
         19230: "Hello",
-        ~~~~~
-!!! error TS2300: Duplicate identifier '19230'.
         "19230": "world",
-        ~~~~~~~
-!!! error TS2300: Duplicate identifier '"19230"'.
     };
     

tests/baselines/reference/optionalPropertiesSyntax.errors.txt

@@ -5,7 +5,9 @@ tests/cases/compiler/optionalPropertiesSyntax.ts(12,5): error TS1131: Property o
 tests/cases/compiler/optionalPropertiesSyntax.ts(18,11): error TS1005: ';' expected.
 tests/cases/compiler/optionalPropertiesSyntax.ts(18,12): error TS1131: Property or signature expected.
 tests/cases/compiler/optionalPropertiesSyntax.ts(24,5): error TS2300: Duplicate identifier 'prop'.
+tests/cases/compiler/optionalPropertiesSyntax.ts(24,5): error TS2686: All declarations of 'prop' must have identical modifiers.
 tests/cases/compiler/optionalPropertiesSyntax.ts(25,5): error TS2300: Duplicate identifier 'prop'.
+tests/cases/compiler/optionalPropertiesSyntax.ts(25,5): error TS2686: All declarations of 'prop' must have identical modifiers.
 tests/cases/compiler/optionalPropertiesSyntax.ts(32,5): error TS2375: Duplicate number index signature.
 tests/cases/compiler/optionalPropertiesSyntax.ts(32,18): error TS1005: ';' expected.
 tests/cases/compiler/optionalPropertiesSyntax.ts(32,19): error TS1131: Property or signature expected.
@@ -14,7 +16,7 @@ tests/cases/compiler/optionalPropertiesSyntax.ts(33,7): error TS2375: Duplicate
 tests/cases/compiler/optionalPropertiesSyntax.ts(34,5): error TS2375: Duplicate number index signature.
 
 
-==== tests/cases/compiler/optionalPropertiesSyntax.ts (14 errors) ====
+==== tests/cases/compiler/optionalPropertiesSyntax.ts (16 errors) ====
     interface fnSigs {
         //functions signatures can be optional
         fn(): void;
@@ -53,9 +55,13 @@ tests/cases/compiler/optionalPropertiesSyntax.ts(34,5): error TS2375: Duplicate
         prop: any;
         ~~~~
 !!! error TS2300: Duplicate identifier 'prop'.
+        ~~~~
+!!! error TS2686: All declarations of 'prop' must have identical modifiers.
         prop?: any;
         ~~~~
 !!! error TS2300: Duplicate identifier 'prop'.
+        ~~~~
+!!! error TS2686: All declarations of 'prop' must have identical modifiers.
         prop2?: any;
     }
     

tests/baselines/reference/parameterPropertyInConstructor2.errors.txt

@@ -1,10 +1,8 @@
 tests/cases/compiler/parameterPropertyInConstructor2.ts(3,5): error TS2394: Overload signature is not compatible with function implementation.
 tests/cases/compiler/parameterPropertyInConstructor2.ts(3,17): error TS2369: A parameter property is only allowed in a constructor implementation.
-tests/cases/compiler/parameterPropertyInConstructor2.ts(3,24): error TS2300: Duplicate identifier 'names'.
-tests/cases/compiler/parameterPropertyInConstructor2.ts(4,24): error TS2300: Duplicate identifier 'names'.
 
 
-==== tests/cases/compiler/parameterPropertyInConstructor2.ts (4 errors) ====
+==== tests/cases/compiler/parameterPropertyInConstructor2.ts (2 errors) ====
     module mod {
       class Customers {
         constructor(public names: string);
@@ -12,11 +10,7 @@ tests/cases/compiler/parameterPropertyInConstructor2.ts(4,24): error TS2300: Dup
 !!! error TS2394: Overload signature is not compatible with function implementation.
                     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2369: A parameter property is only allowed in a constructor implementation.
-                           ~~~~~
-!!! error TS2300: Duplicate identifier 'names'.
         constructor(public names: string, public ages: number) {
-                           ~~~~~
-!!! error TS2300: Duplicate identifier 'names'.
         }
       }
     }

tests/baselines/reference/parser0_004152.errors.txt

@@ -1,7 +1,6 @@
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,28): error TS2304: Cannot find name 'DisplayPosition'.
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,45): error TS1137: Expression or comma expected.
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,46): error TS1005: ';' expected.
-tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,48): error TS2300: Duplicate identifier '3'.
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,49): error TS1005: ';' expected.
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,51): error TS2300: Duplicate identifier '3'.
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,52): error TS1005: ';' expected.
@@ -11,7 +10,6 @@ tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,57): error T
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,58): error TS1005: ';' expected.
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,60): error TS2300: Duplicate identifier '3'.
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,61): error TS1005: ';' expected.
-tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,63): error TS2300: Duplicate identifier '0'.
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,64): error TS1005: ';' expected.
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,66): error TS2300: Duplicate identifier '3'.
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,67): error TS1005: ';' expected.
@@ -34,7 +32,7 @@ tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(2,97): error T
 tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(3,25): error TS2304: Cannot find name 'SeedCoords'.
 
 
-==== tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts (34 errors) ====
+==== tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts (32 errors) ====
     export class Game {
         private position = new DisplayPosition([), 3, 3, 3, 3, 3, 0, 3, 3, 3, 3, 3, 3, 0], NoMove, 0);
                                ~~~~~~~~~~~~~~~
@@ -43,8 +41,6 @@ tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(3,25): error T
 !!! error TS1137: Expression or comma expected.
                                                  ~
 !!! error TS1005: ';' expected.
-                                                   ~
-!!! error TS2300: Duplicate identifier '3'.
                                                     ~
 !!! error TS1005: ';' expected.
                                                       ~
@@ -63,8 +59,6 @@ tests/cases/conformance/parser/ecmascript5/Fuzz/parser0_004152.ts(3,25): error T
 !!! error TS2300: Duplicate identifier '3'.
                                                                 ~
 !!! error TS1005: ';' expected.
-                                                                  ~
-!!! error TS2300: Duplicate identifier '0'.
                                                                    ~
 !!! error TS1005: ';' expected.
                                                                      ~

tests/baselines/reference/parserComputedPropertyName5.errors.txt

@@ -1,9 +1,12 @@
+tests/cases/conformance/parser/ecmascript6/ComputedPropertyNames/parserComputedPropertyName5.ts(1,11): error TS1042: 'public' modifier cannot be used here.
 tests/cases/conformance/parser/ecmascript6/ComputedPropertyNames/parserComputedPropertyName5.ts(1,22): error TS2378: A 'get' accessor must return a value.
 tests/cases/conformance/parser/ecmascript6/ComputedPropertyNames/parserComputedPropertyName5.ts(1,23): error TS2304: Cannot find name 'e'.
 
 
-==== tests/cases/conformance/parser/ecmascript6/ComputedPropertyNames/parserComputedPropertyName5.ts (2 errors) ====
+==== tests/cases/conformance/parser/ecmascript6/ComputedPropertyNames/parserComputedPropertyName5.ts (3 errors) ====
     var v = { public get [e]() { } };
+              ~~~~~~
+!!! error TS1042: 'public' modifier cannot be used here.
                          ~~~
 !!! error TS2378: A 'get' accessor must return a value.
                           ~

tests/baselines/reference/propertyNamedPrototype.errors.txt

@@ -1,10 +0,0 @@
-tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedPrototype.ts(3,12): error TS2300: Duplicate identifier 'prototype'.
-
-
-==== tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedPrototype.ts (1 errors) ====
-    class C {
-        prototype: number; // ok
-        static prototype: C; // error
-               ~~~~~~~~~
-!!! error TS2300: Duplicate identifier 'prototype'.
-    }

tests/baselines/reference/propertyNamedPrototype.symbols

@@ -0,0 +1,11 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedPrototype.ts ===
+class C {
+>C : Symbol(C, Decl(propertyNamedPrototype.ts, 0, 0))
+
+    prototype: number; // ok
+>prototype : Symbol(C.prototype, Decl(propertyNamedPrototype.ts, 0, 9))
+
+    static prototype: C; // error
+>prototype : Symbol(C.prototype, Decl(propertyNamedPrototype.ts, 1, 22))
+>C : Symbol(C, Decl(propertyNamedPrototype.ts, 0, 0))
+}

tests/baselines/reference/propertyNamedPrototype.types

@@ -0,0 +1,11 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedPrototype.ts ===
+class C {
+>C : C
+
+    prototype: number; // ok
+>prototype : number
+
+    static prototype: C; // error
+>prototype : C
+>C : C
+}

tests/baselines/reference/reassignStaticProp.errors.txt

@@ -1,17 +1,17 @@
-tests/cases/compiler/reassignStaticProp.ts(3,12): error TS2300: Duplicate identifier 'bar'.
 tests/cases/compiler/reassignStaticProp.ts(5,12): error TS2300: Duplicate identifier 'bar'.
+tests/cases/compiler/reassignStaticProp.ts(5,12): error TS2403: Subsequent variable declarations must have the same type.  Variable 'bar' must be of type 'number', but here has type 'string'.
 
 
 ==== tests/cases/compiler/reassignStaticProp.ts (2 errors) ====
     class foo {
      
         static bar = 1;
-               ~~~
-!!! error TS2300: Duplicate identifier 'bar'.
      
         static bar:string; // errror - duplicate id
                ~~~
 !!! error TS2300: Duplicate identifier 'bar'.
+               ~~~
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'bar' must be of type 'number', but here has type 'string'.
      
     }
      

tests/baselines/reference/staticPrototypeProperty.errors.txt

@@ -1,8 +1,7 @@
 tests/cases/compiler/staticPrototypeProperty.ts(2,11): error TS2300: Duplicate identifier 'prototype'.
-tests/cases/compiler/staticPrototypeProperty.ts(6,11): error TS2300: Duplicate identifier 'prototype'.
 
 
-==== tests/cases/compiler/staticPrototypeProperty.ts (2 errors) ====
+==== tests/cases/compiler/staticPrototypeProperty.ts (1 errors) ====
     class C {
        static prototype() { }
               ~~~~~~~~~
@@ -11,6 +10,4 @@ tests/cases/compiler/staticPrototypeProperty.ts(6,11): error TS2300: Duplicate i
      
     class C2 {
        static prototype;
-              ~~~~~~~~~
-!!! error TS2300: Duplicate identifier 'prototype'.
     }

tests/baselines/reference/stringLiteralTypesInImplementationSignatures2.errors.txt

@@ -1,8 +1,7 @@
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/stringLiteralTypesInImplementationSignatures2.ts(26,5): error TS2300: Duplicate identifier 'foo'.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/stringLiteralTypesInImplementationSignatures2.ts(27,5): error TS2300: Duplicate identifier 'foo'.
 
 
-==== tests/cases/conformance/types/objectTypeLiteral/callSignatures/stringLiteralTypesInImplementationSignatures2.ts (2 errors) ====
+==== tests/cases/conformance/types/objectTypeLiteral/callSignatures/stringLiteralTypesInImplementationSignatures2.ts (1 errors) ====
     // String literal types are only valid in overload signatures
     
     function foo(x: any);
@@ -29,8 +28,6 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/stringLiteralType
     
     var b = {
         foo(x: 'hi') { },
-        ~~~
-!!! error TS2300: Duplicate identifier 'foo'.
         foo(x: 'a') { },
         ~~~
 !!! error TS2300: Duplicate identifier 'foo'.

tests/baselines/reference/stringNamedPropertyDuplicates.errors.txt

@@ -1,57 +1,45 @@
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(2,5): error TS2300: Duplicate identifier '"a b"'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(3,5): error TS2300: Duplicate identifier '"a b"'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(4,12): error TS2300: Duplicate identifier '"c d"'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(5,12): error TS2300: Duplicate identifier '"c d"'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(9,5): error TS2300: Duplicate identifier '"a b"'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(10,5): error TS2300: Duplicate identifier '"a b"'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(14,5): error TS2300: Duplicate identifier '"a b"'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(15,5): error TS2300: Duplicate identifier '"a b"'.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(19,5): error TS2300: Duplicate identifier '"a b"'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(3,5): error TS2300: Duplicate identifier 'a b'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(5,12): error TS2300: Duplicate identifier 'c d'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(9,5): error TS2300: Duplicate identifier 'a b'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(10,5): error TS2300: Duplicate identifier 'a b'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(14,5): error TS2300: Duplicate identifier 'a b'.
+tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(15,5): error TS2300: Duplicate identifier 'a b'.
 tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(20,5): error TS1005: ',' expected.
-tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts(20,5): error TS2300: Duplicate identifier '"a b"'.
 
 
-==== tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts (11 errors) ====
+==== tests/cases/conformance/types/objectTypeLiteral/propertySignatures/stringNamedPropertyDuplicates.ts (7 errors) ====
     class C {
         "a b": number;
-        ~~~~~
-!!! error TS2300: Duplicate identifier '"a b"'.
         "a b": number;
         ~~~~~
-!!! error TS2300: Duplicate identifier '"a b"'.
+!!! error TS2300: Duplicate identifier 'a b'.
+        static "c d": number;
         static "c d": number;
                ~~~~~
-!!! error TS2300: Duplicate identifier '"c d"'.
-        static "c d": number;
-               ~~~~~
-!!! error TS2300: Duplicate identifier '"c d"'.
+!!! error TS2300: Duplicate identifier 'c d'.
     }
     
     interface I {
         "a b": number;
         ~~~~~
-!!! error TS2300: Duplicate identifier '"a b"'.
+!!! error TS2300: Duplicate identifier 'a b'.
         "a b": number;
         ~~~~~
-!!! error TS2300: Duplicate identifier '"a b"'.
+!!! error TS2300: Duplicate identifier 'a b'.
     }
     
     var a: {
         "a b": number;
         ~~~~~
-!!! error TS2300: Duplicate identifier '"a b"'.
+!!! error TS2300: Duplicate identifier 'a b'.
         "a b": number;
         ~~~~~
-!!! error TS2300: Duplicate identifier '"a b"'.
+!!! error TS2300: Duplicate identifier 'a b'.
     }
     
     var b = {
         "a b": 1
-        ~~~~~
-!!! error TS2300: Duplicate identifier '"a b"'.
         "a b": 1
         ~~~~~
 !!! error TS1005: ',' expected.
-        ~~~~~
-!!! error TS2300: Duplicate identifier '"a b"'.
     }

tests/baselines/reference/symbolProperty36.errors.txt

@@ -1,12 +1,9 @@
-tests/cases/conformance/es6/Symbols/symbolProperty36.ts(2,5): error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
 tests/cases/conformance/es6/Symbols/symbolProperty36.ts(3,5): error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
 
 
-==== tests/cases/conformance/es6/Symbols/symbolProperty36.ts (2 errors) ====
+==== tests/cases/conformance/es6/Symbols/symbolProperty36.ts (1 errors) ====
     var x = {
         [Symbol.isConcatSpreadable]: 0,
-        ~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
         [Symbol.isConcatSpreadable]: 1
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.

tests/baselines/reference/symbolProperty37.errors.txt

@@ -1,13 +0,0 @@
-tests/cases/conformance/es6/Symbols/symbolProperty37.ts(2,5): error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
-tests/cases/conformance/es6/Symbols/symbolProperty37.ts(3,5): error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
-
-
-==== tests/cases/conformance/es6/Symbols/symbolProperty37.ts (2 errors) ====
-    interface I {
-        [Symbol.isConcatSpreadable]: string;
-        ~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
-        [Symbol.isConcatSpreadable]: string;
-        ~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
-    }

tests/baselines/reference/symbolProperty37.symbols

@@ -0,0 +1,14 @@
+=== tests/cases/conformance/es6/Symbols/symbolProperty37.ts ===
+interface I {
+>I : Symbol(I, Decl(symbolProperty37.ts, 0, 0))
+
+    [Symbol.isConcatSpreadable]: string;
+>Symbol.isConcatSpreadable : Symbol(SymbolConstructor.isConcatSpreadable, Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+>Symbol : Symbol(Symbol, Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --))
+>isConcatSpreadable : Symbol(SymbolConstructor.isConcatSpreadable, Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+
+    [Symbol.isConcatSpreadable]: string;
+>Symbol.isConcatSpreadable : Symbol(SymbolConstructor.isConcatSpreadable, Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+>Symbol : Symbol(Symbol, Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --))
+>isConcatSpreadable : Symbol(SymbolConstructor.isConcatSpreadable, Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+}

tests/baselines/reference/symbolProperty37.types

@@ -0,0 +1,14 @@
+=== tests/cases/conformance/es6/Symbols/symbolProperty37.ts ===
+interface I {
+>I : I
+
+    [Symbol.isConcatSpreadable]: string;
+>Symbol.isConcatSpreadable : symbol
+>Symbol : SymbolConstructor
+>isConcatSpreadable : symbol
+
+    [Symbol.isConcatSpreadable]: string;
+>Symbol.isConcatSpreadable : symbol
+>Symbol : SymbolConstructor
+>isConcatSpreadable : symbol
+}

tests/baselines/reference/symbolProperty38.errors.txt

@@ -1,15 +0,0 @@
-tests/cases/conformance/es6/Symbols/symbolProperty38.ts(2,5): error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
-tests/cases/conformance/es6/Symbols/symbolProperty38.ts(5,5): error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
-
-
-==== tests/cases/conformance/es6/Symbols/symbolProperty38.ts (2 errors) ====
-    interface I {
-        [Symbol.isConcatSpreadable]: string;
-        ~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
-    }
-    interface I {
-        [Symbol.isConcatSpreadable]: string;
-        ~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2300: Duplicate identifier '[Symbol.isConcatSpreadable]'.
-    }

tests/baselines/reference/symbolProperty38.symbols

@@ -0,0 +1,17 @@
+=== tests/cases/conformance/es6/Symbols/symbolProperty38.ts ===
+interface I {
+>I : Symbol(I, Decl(symbolProperty38.ts, 0, 0), Decl(symbolProperty38.ts, 2, 1))
+
+    [Symbol.isConcatSpreadable]: string;
+>Symbol.isConcatSpreadable : Symbol(SymbolConstructor.isConcatSpreadable, Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+>Symbol : Symbol(Symbol, Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --))
+>isConcatSpreadable : Symbol(SymbolConstructor.isConcatSpreadable, Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+}
+interface I {
+>I : Symbol(I, Decl(symbolProperty38.ts, 0, 0), Decl(symbolProperty38.ts, 2, 1))
+
+    [Symbol.isConcatSpreadable]: string;
+>Symbol.isConcatSpreadable : Symbol(SymbolConstructor.isConcatSpreadable, Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+>Symbol : Symbol(Symbol, Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --))
+>isConcatSpreadable : Symbol(SymbolConstructor.isConcatSpreadable, Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+}

tests/baselines/reference/symbolProperty38.types

@@ -0,0 +1,17 @@
+=== tests/cases/conformance/es6/Symbols/symbolProperty38.ts ===
+interface I {
+>I : I
+
+    [Symbol.isConcatSpreadable]: string;
+>Symbol.isConcatSpreadable : symbol
+>Symbol : SymbolConstructor
+>isConcatSpreadable : symbol
+}
+interface I {
+>I : I
+
+    [Symbol.isConcatSpreadable]: string;
+>Symbol.isConcatSpreadable : symbol
+>Symbol : SymbolConstructor
+>isConcatSpreadable : symbol
+}

tests/baselines/reference/symbolProperty44.errors.txt

@@ -1,8 +1,9 @@
 tests/cases/conformance/es6/Symbols/symbolProperty44.ts(2,9): error TS2300: Duplicate identifier '[Symbol.hasInstance]'.
 tests/cases/conformance/es6/Symbols/symbolProperty44.ts(5,9): error TS2300: Duplicate identifier '[Symbol.hasInstance]'.
+tests/cases/conformance/es6/Symbols/symbolProperty44.ts(5,9): error TS2300: Duplicate identifier '__@hasInstance'.
 
 
-==== tests/cases/conformance/es6/Symbols/symbolProperty44.ts (2 errors) ====
+==== tests/cases/conformance/es6/Symbols/symbolProperty44.ts (3 errors) ====
     class C {
         get [Symbol.hasInstance]() {
             ~~~~~~~~~~~~~~~~~~~~
@@ -12,6 +13,8 @@ tests/cases/conformance/es6/Symbols/symbolProperty44.ts(5,9): error TS2300: Dupl
         get [Symbol.hasInstance]() {
             ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2300: Duplicate identifier '[Symbol.hasInstance]'.
+            ~~~~~~~~~~~~~~~~~~~~
+!!! error TS2300: Duplicate identifier '__@hasInstance'.
             return "";
         }
     }

tests/cases/compiler/duplicateIdentifierComputedName.ts

@@ -0,0 +1,4 @@
+class C {
+    ["a"]: string;
+    ["a"]: string;
+}

tests/cases/compiler/duplicateIdentifierDifferentModifiers.ts

@@ -0,0 +1,21 @@
+// Not OK
+interface B { x; }
+interface B { x?; }
+
+// OK
+class A {
+  public y: string;
+}
+
+interface A {
+  y: string;
+}
+
+// Not OK
+class C {
+  private y: string;
+}
+
+interface C {
+  y: string;
+}

tests/cases/compiler/duplicateIdentifierDifferentSpelling.ts

@@ -0,0 +1,6 @@
+class A {
+  0b11 = '';
+  3 = '';
+}
+
+var X = { 0b11: '', 3: '' };