microsoft · ahejlsberg · Sep 30, 2015 · Sep 21, 2015 · Sep 21, 2015 · Sep 21, 2015
diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
@@ -88,6 +88,7 @@ namespace ts {
         let container: Node;
         let blockScopeContainer: Node;
         let lastContainer: Node;
+        let seenThisKeyword: boolean;
 
         // If this file is an external module, then it is automatically in strict-mode according to
         // ES6.  If it is not an external module, then we'll determine if it is in strict mode or
@@ -329,7 +330,14 @@ namespace ts {
                 blockScopeContainer.locals = undefined;
             }
 
-            forEachChild(node, bind);
+            if (node.kind === SyntaxKind.InterfaceDeclaration) {
+                seenThisKeyword = false;
+                forEachChild(node, bind);
+                node.flags = seenThisKeyword ? node.flags | NodeFlags.ContainsThis : node.flags & ~NodeFlags.ContainsThis;
+            }
+            else {
+                forEachChild(node, bind);
+            }
 
             container = saveContainer;
             parent = saveParent;
@@ -851,6 +859,9 @@ namespace ts {
                     return checkStrictModePrefixUnaryExpression(<PrefixUnaryExpression>node);
                 case SyntaxKind.WithStatement:
                     return checkStrictModeWithStatement(<WithStatement>node);
+                case SyntaxKind.ThisKeyword:
+                    seenThisKeyword = true;
+                    return;
 
                 case SyntaxKind.TypeParameter:
                     return declareSymbolAndAddToSymbolTable(<Declaration>node, SymbolFlags.TypeParameter, SymbolFlags.TypeParameterExcludes);

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
diff --git a/src/compiler/declarationEmitter.ts b/src/compiler/declarationEmitter.ts
@@ -52,6 +52,7 @@ namespace ts {
         let enclosingDeclaration: Node;
         let currentSourceFile: SourceFile;
         let reportedDeclarationError = false;
+        let errorNameNode: DeclarationName;
         let emitJsDocComments = compilerOptions.removeComments ? function (declaration: Node) { } : writeJsDocComments;
         let emit = compilerOptions.stripInternal ? stripInternal : emitNode;
 
@@ -152,6 +153,7 @@ namespace ts {
         function createAndSetNewTextWriterWithSymbolWriter(): EmitTextWriterWithSymbolWriter {
             let writer = <EmitTextWriterWithSymbolWriter>createTextWriter(newLine);
             writer.trackSymbol = trackSymbol;
+            writer.reportInaccessibleThisError = reportInaccessibleThisError;
             writer.writeKeyword = writer.write;
             writer.writeOperator = writer.write;
             writer.writePunctuation = writer.write;
@@ -257,6 +259,13 @@ namespace ts {
             handleSymbolAccessibilityError(resolver.isSymbolAccessible(symbol, enclosingDeclaration, meaning));
         }
 
+        function reportInaccessibleThisError() {
+            if (errorNameNode) {
+                diagnostics.push(createDiagnosticForNode(errorNameNode, Diagnostics.The_inferred_type_of_0_references_an_inaccessible_this_type_A_type_annotation_is_necessary,
+                    declarationNameToString(errorNameNode)));
+            }
+        }
+
         function writeTypeOfDeclaration(declaration: AccessorDeclaration | VariableLikeDeclaration, type: TypeNode, getSymbolAccessibilityDiagnostic: GetSymbolAccessibilityDiagnostic) {
             writer.getSymbolAccessibilityDiagnostic = getSymbolAccessibilityDiagnostic;
             write(": ");
@@ -265,7 +274,9 @@ namespace ts {
                 emitType(type);
             }
             else {
+                errorNameNode = declaration.name;
                 resolver.writeTypeOfDeclaration(declaration, enclosingDeclaration, TypeFormatFlags.UseTypeOfFunction, writer);
+                errorNameNode = undefined;
             }
         }
 
@@ -277,7 +288,9 @@ namespace ts {
                 emitType(signature.type);
             }
             else {
+                errorNameNode = signature.name;
                 resolver.writeReturnTypeOfSignatureDeclaration(signature, enclosingDeclaration, TypeFormatFlags.UseTypeOfFunction, writer);
+                errorNameNode = undefined;
             }
         }
 
@@ -326,6 +339,7 @@ namespace ts {
                 case SyntaxKind.BooleanKeyword:
                 case SyntaxKind.SymbolKeyword:
                 case SyntaxKind.VoidKeyword:
+                case SyntaxKind.ThisKeyword:
                 case SyntaxKind.StringLiteral:
                     return writeTextOfNode(currentSourceFile, type);
                 case SyntaxKind.ExpressionWithTypeArguments:

diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
@@ -1652,6 +1652,14 @@
         "category": "Error",
         "code": 2525
     },
+    "A 'this' type is available only in a non-static member of a class or interface.": {
+        "category": "Error",
+        "code": 2526
+    },
+    "The inferred type of '{0}' references an inaccessible 'this' type. A type annotation is necessary.": {
+        "category": "Error",
+        "code": 2527
+    },
     "JSX element attributes type '{0}' must be an object type.": {
         "category": "Error",
         "code": 2600

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
@@ -2360,6 +2360,7 @@ namespace ts {
                     let node = tryParse(parseKeywordAndNoDot);
                     return node || parseTypeReferenceOrTypePredicate();
                 case SyntaxKind.VoidKeyword:
+                case SyntaxKind.ThisKeyword:
                     return parseTokenNode<TypeNode>();
                 case SyntaxKind.TypeOfKeyword:
                     return parseTypeQuery();
@@ -2382,6 +2383,7 @@ namespace ts {
                 case SyntaxKind.BooleanKeyword:
                 case SyntaxKind.SymbolKeyword:
                 case SyntaxKind.VoidKeyword:
+                case SyntaxKind.ThisKeyword:
                 case SyntaxKind.TypeOfKeyword:
                 case SyntaxKind.OpenBraceToken:
                 case SyntaxKind.OpenBracketToken:

diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -376,6 +376,7 @@ namespace ts {
         OctalLiteral =      0x00010000,  // Octal numeric literal
         Namespace =         0x00020000,  // Namespace declaration
         ExportContext =     0x00040000,  // Export context (initialized by binding)
+        ContainsThis =      0x00080000,  // Interface contains references to "this"
 
         Modifier = Export | Ambient | Public | Private | Protected | Static | Abstract | Default | Async,
         AccessibilityModifier = Public | Private | Protected,
@@ -1496,6 +1497,7 @@ namespace ts {
         // declaration emitter to help determine if it should patch up the final declaration file
         // with import statements it previously saw (but chose not to emit).
         trackSymbol(symbol: Symbol, enclosingDeclaration?: Node, meaning?: SymbolFlags): void;
+        reportInaccessibleThisError(): void;
     }
 
     export const enum TypeFormatFlags {
@@ -1797,6 +1799,7 @@ namespace ts {
         /* @internal */
         ContainsAnyFunctionType = 0x00800000,  // Type is or contains object literal type
         ESSymbol                = 0x01000000,  // Type of symbol primitive introduced in ES6
+        ThisType                = 0x02000000,  // This type
 
         /* @internal */
         Intrinsic = Any | String | Number | Boolean | ESSymbol | Void | Undefined | Null,
@@ -1842,6 +1845,7 @@ namespace ts {
         typeParameters: TypeParameter[];           // Type parameters (undefined if non-generic)
         outerTypeParameters: TypeParameter[];      // Outer type parameters (undefined if none)
         localTypeParameters: TypeParameter[];      // Local type parameters (undefined if none)
+        thisType: TypeParameter;                   // The "this" type (undefined if none)
         /* @internal */
         resolvedBaseConstructorType?: Type;        // Resolved base constructor type of class
         /* @internal */
@@ -1856,10 +1860,17 @@ namespace ts {
         declaredNumberIndexType: Type;             // Declared numeric index type
     }
 
-    // Type references (TypeFlags.Reference)
+    // Type references (TypeFlags.Reference). When a class or interface has type parameters or
+    // a "this" type, references to the class or interface are made using type references. The
+    // typeArguments property specififes the types to substitute for the type parameters of the
+    // class or interface and optionally includes an extra element that specifies the type to
+    // substitute for "this" in the resulting instantiation. When no extra argument is present,
+    // the type reference itself is substituted for "this". The typeArguments property is undefined
+    // if the class or interface has no type parameters and the reference isn't specifying an
+    // explicit "this" argument.
     export interface TypeReference extends ObjectType {
         target: GenericType;    // Type reference target
-        typeArguments: Type[];  // Type reference type arguments
+        typeArguments: Type[];  // Type reference type arguments (undefined if none)
     }
 
     // Generic class and interface types

diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
@@ -65,7 +65,8 @@ namespace ts {
                 increaseIndent: () => { },
                 decreaseIndent: () => { },
                 clear: () => str = "",
-                trackSymbol: () => { }
+                trackSymbol: () => { },
+                reportInaccessibleThisError: () => { }
             };
         }
 
@@ -468,13 +469,12 @@ namespace ts {
                 else if (node.parent.kind === SyntaxKind.PropertyAccessExpression && (<PropertyAccessExpression>node.parent).name === node) {
                     node = node.parent;
                 }
-            // fall through
-            case SyntaxKind.QualifiedName:
-            case SyntaxKind.PropertyAccessExpression:
                 // At this point, node is either a qualified name or an identifier
                 Debug.assert(node.kind === SyntaxKind.Identifier || node.kind === SyntaxKind.QualifiedName || node.kind === SyntaxKind.PropertyAccessExpression,
                     "'node' was expected to be a qualified name, identifier or property access in 'isTypeNode'.");
-
+            case SyntaxKind.QualifiedName:
+            case SyntaxKind.PropertyAccessExpression:
+            case SyntaxKind.ThisKeyword:
                 let parent = node.parent;
                 if (parent.kind === SyntaxKind.TypeQuery) {
                     return false;
@@ -733,6 +733,9 @@ namespace ts {
                 case SyntaxKind.Constructor:
                 case SyntaxKind.GetAccessor:
                 case SyntaxKind.SetAccessor:
+                case SyntaxKind.CallSignature:
+                case SyntaxKind.ConstructSignature:
+                case SyntaxKind.IndexSignature:
                 case SyntaxKind.EnumDeclaration:
                 case SyntaxKind.SourceFile:
                     return node;
@@ -895,7 +898,6 @@ namespace ts {
 
     export function isExpression(node: Node): boolean {
         switch (node.kind) {
-            case SyntaxKind.ThisKeyword:
             case SyntaxKind.SuperKeyword:
             case SyntaxKind.NullKeyword:
             case SyntaxKind.TrueKeyword:
@@ -928,6 +930,7 @@ namespace ts {
             case SyntaxKind.JsxElement:
             case SyntaxKind.JsxSelfClosingElement:
             case SyntaxKind.YieldExpression:
+            case SyntaxKind.AwaitExpression:
                 return true;
             case SyntaxKind.QualifiedName:
                 while (node.parent.kind === SyntaxKind.QualifiedName) {
@@ -941,6 +944,7 @@ namespace ts {
             // fall through
             case SyntaxKind.NumericLiteral:
             case SyntaxKind.StringLiteral:
+            case SyntaxKind.ThisKeyword:
                 let parent = node.parent;
                 switch (parent.kind) {
                     case SyntaxKind.VariableDeclaration:

diff --git a/src/services/services.ts b/src/services/services.ts
@@ -725,7 +725,7 @@ namespace ts {
         }
         getBaseTypes(): ObjectType[] {
             return this.flags & (TypeFlags.Class | TypeFlags.Interface)
-                ? this.checker.getBaseTypes(<TypeObject & InterfaceType>this)
+                ? this.checker.getBaseTypes(<InterfaceType><Type>this)
                 : undefined;
         }
     }
@@ -6249,7 +6249,8 @@ namespace ts {
             }
 
             return node.parent.kind === SyntaxKind.TypeReference ||
-                (node.parent.kind === SyntaxKind.ExpressionWithTypeArguments && !isExpressionWithTypeArgumentsInClassExtendsClause(<ExpressionWithTypeArguments>node.parent));
+                (node.parent.kind === SyntaxKind.ExpressionWithTypeArguments && !isExpressionWithTypeArgumentsInClassExtendsClause(<ExpressionWithTypeArguments>node.parent)) ||
+                node.kind === SyntaxKind.ThisKeyword && !isExpression(node);
         }
 
         function isNamespaceReference(node: Node): boolean {

diff --git a/src/services/utilities.ts b/src/services/utilities.ts
@@ -626,7 +626,8 @@ namespace ts {
             increaseIndent: () => { indent++; },
             decreaseIndent: () => { indent--; },
             clear: resetWriter,
-            trackSymbol: () => { }
+            trackSymbol: () => { },
+            reportInaccessibleThisError: () => { }
         };
 
         function writeIndent() {

diff --git a/tests/baselines/reference/2dArrays.types b/tests/baselines/reference/2dArrays.types
@@ -28,7 +28,7 @@ class Board {
 >this.ships.every(function (val) { return val.isSunk; }) : boolean
 >this.ships.every : (callbackfn: (value: Ship, index: number, array: Ship[]) => boolean, thisArg?: any) => boolean
 >this.ships : Ship[]
->this : Board
+>this : this
 >ships : Ship[]
 >every : (callbackfn: (value: Ship, index: number, array: Ship[]) => boolean, thisArg?: any) => boolean
 >function (val) { return val.isSunk; } : (val: Ship) => boolean

diff --git a/tests/baselines/reference/accessOverriddenBaseClassMember1.types b/tests/baselines/reference/accessOverriddenBaseClassMember1.types
@@ -15,11 +15,11 @@ class Point {
 >"x=" + this.x : string
 >"x=" : string
 >this.x : number
->this : Point
+>this : this
 >x : number
 >" y=" : string
 >this.y : number
->this : Point
+>this : this
 >y : number
     }
 }
@@ -50,7 +50,7 @@ class ColoredPoint extends Point {
 >toString : () => string
 >" color=" : string
 >this.color : string
->this : ColoredPoint
+>this : this
 >color : string
     }
 }

diff --git a/tests/baselines/reference/aliasUsageInAccessorsOfClass.types b/tests/baselines/reference/aliasUsageInAccessorsOfClass.types
@@ -26,7 +26,7 @@ class C2 {
 
         return this.x;
 >this.x : IHasVisualizationModel
->this : C2
+>this : this
 >x : IHasVisualizationModel
     }
     set A(x) {

diff --git a/tests/baselines/reference/ambiguousCallsWhereReturnTypesAgree.types b/tests/baselines/reference/ambiguousCallsWhereReturnTypesAgree.types
@@ -31,7 +31,7 @@ class TestClass {
         this.bar(x); // should not error
 >this.bar(x) : void
 >this.bar : { (x: string): void; (x: string[]): void; }
->this : TestClass
+>this : this
 >bar : { (x: string): void; (x: string[]): void; }
 >x : any
     }
@@ -71,7 +71,7 @@ class TestClass2 {
         return this.bar(x); // should not error
 >this.bar(x) : number
 >this.bar : { (x: string): number; (x: string[]): number; }
->this : TestClass2
+>this : this
 >bar : { (x: string): number; (x: string[]): number; }
 >x : any
     }

diff --git a/tests/baselines/reference/amdModuleName1.types b/tests/baselines/reference/amdModuleName1.types
@@ -10,7 +10,7 @@ class Foo {
         this.x = 5;
 >this.x = 5 : number
 >this.x : number
->this : Foo
+>this : this
 >x : number
 >5 : number
     }

diff --git a/tests/baselines/reference/arityAndOrderCompatibility01.errors.txt b/tests/baselines/reference/arityAndOrderCompatibility01.errors.txt
@@ -34,6 +34,8 @@ tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(25,5): error
 tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(26,5): error TS2322: Type 'StrNum' is not assignable to type '[string]'.
   Types of property 'pop' are incompatible.
     Type '() => string | number' is not assignable to type '() => string'.
+      Type 'string | number' is not assignable to type 'string'.
+        Type 'number' is not assignable to type 'string'.
 tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(27,5): error TS2322: Type '{ 0: string; 1: number; }' is not assignable to type '[string]'.
   Property 'length' is missing in type '{ 0: string; 1: number; }'.
 tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(28,5): error TS2322: Type '[string, number]' is not assignable to type '[number, string]'.
@@ -125,6 +127,8 @@ tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(30,5): error
 !!! error TS2322: Type 'StrNum' is not assignable to type '[string]'.
 !!! error TS2322:   Types of property 'pop' are incompatible.
 !!! error TS2322:     Type '() => string | number' is not assignable to type '() => string'.
+!!! error TS2322:       Type 'string | number' is not assignable to type 'string'.
+!!! error TS2322:         Type 'number' is not assignable to type 'string'.
     var m3: [string] = z;
         ~~
 !!! error TS2322: Type '{ 0: string; 1: number; }' is not assignable to type '[string]'.