Typed 'this' in object literal methods

src/compiler/types.ts

@@ -519,6 +519,8 @@
         /* @internal */ localSymbol?: Symbol;           // Local symbol declared by node (initialized by binding only for exported nodes)
         /* @internal */ flowNode?: FlowNode;            // Associated FlowNode (initialized by binding)
         /* @internal */ emitNode?: EmitNode;            // Associated EmitNode (initialized by transforms)
+        /* @internal */ contextualType?: Type;          // Used to temporarily assign a contextual type during overload resolution
+        /* @internal */ contextualMapper?: TypeMapper;  // Mapper for contextual type
     }
 
     export interface NodeArray<T extends Node> extends Array<T>, TextRange {
@@ -957,7 +959,6 @@
 
     export interface Expression extends Node {
         _expressionBrand: any;
-        contextualType?: Type;  // Used to temporarily assign a contextual type during overload resolution
     }
 
     export interface OmittedExpression extends Expression {

src/lib/es5.d.ts

@@ -147,22 +147,22 @@ interface ObjectConstructor {
       * @param o Object to use as a prototype. May be null
       * @param properties JavaScript object that contains one or more property descriptors.
       */
-    create(o: object | null, properties: PropertyDescriptorMap): any;
+    create(o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any;
 
     /**
       * Adds a property to an object, or modifies attributes of an existing property.
       * @param o Object on which to add or modify the property. This can be a native JavaScript object (that is, a user-defined object or a built in object) or a DOM object.
       * @param p The property name.
       * @param attributes Descriptor for the property. It can be for a data property or an accessor property.
       */
-    defineProperty(o: any, p: string, attributes: PropertyDescriptor): any;
+    defineProperty(o: any, p: string, attributes: PropertyDescriptor & ThisType<any>): any;
 
     /**
       * Adds one or more properties to an object, and/or modifies attributes of existing properties.
       * @param o Object on which to add or modify the properties. This can be a native JavaScript object or a DOM object.
       * @param properties JavaScript object that contains one or more descriptor objects. Each descriptor object describes a data property or an accessor property.
       */
-    defineProperties(o: any, properties: PropertyDescriptorMap): any;
+    defineProperties(o: any, properties: PropertyDescriptorMap & ThisType<any>): any;
 
     /**
       * Prevents the modification of attributes of existing properties, and prevents the addition of new properties.
@@ -1366,6 +1366,11 @@ type Record<K extends string, T> = {
     [P in K]: T;
 }
 
+/**
+ * Marker for contextual 'this' type
+ */
+interface ThisType<T> { }
+
 /**
   * Represents a raw buffer of binary data, which is used to store data for the
   * different typed arrays. ArrayBuffers cannot be read from or written to directly,

tests/baselines/reference/declarationEmitThisPredicates02.errors.txt

@@ -13,7 +13,7 @@ tests/cases/conformance/declarationEmit/typePredicates/declarationEmitThisPredic
         m(): this is Foo {
              ~~~~
 !!! error TS2526: A 'this' type is available only in a non-static member of a class or interface.
-            let dis = this as Foo;
+            let dis = this as {} as Foo;
             return dis.a != null && dis.b != null && dis.c != null;
         }
     }

tests/baselines/reference/declarationEmitThisPredicates02.js

@@ -8,7 +8,7 @@ export interface Foo {
 
 export const obj = {
     m(): this is Foo {
-        let dis = this as Foo;
+        let dis = this as {} as Foo;
         return dis.a != null && dis.b != null && dis.c != null;
     }
 }

tests/baselines/reference/declarationEmitThisPredicatesWithPrivateName02.errors.txt

@@ -16,7 +16,7 @@ tests/cases/conformance/declarationEmit/typePredicates/declarationEmitThisPredic
         m(): this is Foo {
              ~~~~
 !!! error TS2526: A 'this' type is available only in a non-static member of a class or interface.
-            let dis = this as Foo;
+            let dis = this as {} as Foo;
             return dis.a != null && dis.b != null && dis.c != null;
         }
     }

tests/baselines/reference/declarationEmitThisPredicatesWithPrivateName02.js

@@ -8,7 +8,7 @@ interface Foo {
 
 export const obj = {
     m(): this is Foo {
-        let dis = this as Foo;
+        let dis = this as {} as Foo;
         return dis.a != null && dis.b != null && dis.c != null;
     }
 }

tests/baselines/reference/getterSetterNonAccessor.types

@@ -9,9 +9,9 @@ function setFunc(v){}
 
 Object.defineProperty({}, "0", <PropertyDescriptor>({
 >Object.defineProperty({}, "0", <PropertyDescriptor>({          get: getFunc,          set: setFunc,          configurable: true      })) : any
->Object.defineProperty : (o: any, p: string, attributes: PropertyDescriptor) => any
+>Object.defineProperty : (o: any, p: string, attributes: PropertyDescriptor & ThisType<any>) => any
 >Object : ObjectConstructor
->defineProperty : (o: any, p: string, attributes: PropertyDescriptor) => any
+>defineProperty : (o: any, p: string, attributes: PropertyDescriptor & ThisType<any>) => any
 >{} : {}
 >"0" : "0"
 ><PropertyDescriptor>({          get: getFunc,          set: setFunc,          configurable: true      }) : PropertyDescriptor

tests/baselines/reference/looseThisTypeInFunctions.errors.txt

@@ -1,12 +1,14 @@
-tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(21,1): error TS2322: Type '(this: C, m: number) => number' is not assignable to type '(this: void, m: number) => number'.
+tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(22,1): error TS2322: Type '(this: C, m: number) => number' is not assignable to type '(this: void, m: number) => number'.
   The 'this' types of each signature are incompatible.
     Type 'void' is not assignable to type 'C'.
-tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(33,28): error TS2339: Property 'length' does not exist on type 'number'.
-tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(37,9): error TS2684: The 'this' context of type 'void' is not assignable to method's 'this' of type 'I'.
-tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(46,20): error TS2339: Property 'length' does not exist on type 'number'.
+tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(26,27): error TS2339: Property 'length' does not exist on type 'number'.
+tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(34,28): error TS2339: Property 'length' does not exist on type 'number'.
+tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(38,9): error TS2684: The 'this' context of type 'void' is not assignable to method's 'this' of type 'I'.
+tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(47,20): error TS2339: Property 'length' does not exist on type 'number'.
 
 
-==== tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts (4 errors) ====
+==== tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts (5 errors) ====
+
     interface I {
         n: number;
         explicitThis(this: this, m: number): number;
@@ -36,6 +38,8 @@ tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(46,20): error
         n: 101,
         explicitThis: function (m: number) {
             return m + this.n.length; // error, 'length' does not exist on 'number'
+                              ~~~~~~
+!!! error TS2339: Property 'length' does not exist on type 'number'.
         },
         implicitThis(m: number): number { return m; }
     };

tests/baselines/reference/looseThisTypeInFunctions.js

@@ -1,4 +1,5 @@
 //// [looseThisTypeInFunctions.ts]
+
 interface I {
     n: number;
     explicitThis(this: this, m: number): number;

tests/baselines/reference/objectCreate.types

@@ -9,17 +9,17 @@ declare var union: null | { a: number, b: string };
 var n = Object.create(null);             // object
 >n : any
 >Object.create(null) : any
->Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >null : null
 
 var t = Object.create({ a: 1, b: "" });  // {a: number, b: string }
 >t : any
 >Object.create({ a: 1, b: "" }) : any
->Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >{ a: 1, b: "" } : { a: number; b: string; }
 >a : number
 >1 : 1
@@ -29,43 +29,43 @@ var t = Object.create({ a: 1, b: "" });  // {a: number, b: string }
 var u = Object.create(union);            // object | {a: number, b: string }
 >u : any
 >Object.create(union) : any
->Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >union : { a: number; b: string; } | null
 
 var e = Object.create({});               // {}
 >e : any
 >Object.create({}) : any
->Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >{} : {}
 
 var o = Object.create(<object>{});       // object
 >o : any
 >Object.create(<object>{}) : any
->Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 ><object>{} : object
 >{} : {}
 
 var a = Object.create(null, {});           // any
 >a : any
 >Object.create(null, {}) : any
->Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >null : null
 >{} : {}
 
 var a = Object.create({ a: 1, b: "" }, {});
 >a : any
 >Object.create({ a: 1, b: "" }, {}) : any
->Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >{ a: 1, b: "" } : { a: number; b: string; }
 >a : number
 >1 : 1
@@ -76,27 +76,27 @@ var a = Object.create({ a: 1, b: "" }, {});
 var a = Object.create(union, {});
 >a : any
 >Object.create(union, {}) : any
->Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >union : { a: number; b: string; } | null
 >{} : {}
 
 var a = Object.create({}, {});
 >a : any
 >Object.create({}, {}) : any
->Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >{} : {}
 >{} : {}
 
 var a = Object.create(<object>{}, {});
 >a : any
 >Object.create(<object>{}, {}) : any
->Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap): any; }
+>create : { (o: object | null): any; (o: object | null, properties: PropertyDescriptorMap & ThisType<any>): any; }
 ><object>{} : object
 >{} : {}
 >{} : {}

tests/baselines/reference/objectCreate2.types

@@ -9,17 +9,17 @@ declare var union: null | { a: number, b: string };
 var n = Object.create(null);             // any
 >n : any
 >Object.create(null) : any
->Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >null : null
 
 var t = Object.create({ a: 1, b: "" });  // {a: number, b: string }
 >t : any
 >Object.create({ a: 1, b: "" }) : any
->Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >{ a: 1, b: "" } : { a: number; b: string; }
 >a : number
 >1 : 1
@@ -29,43 +29,43 @@ var t = Object.create({ a: 1, b: "" });  // {a: number, b: string }
 var u = Object.create(union);            // {a: number, b: string }
 >u : any
 >Object.create(union) : any
->Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >union : { a: number; b: string; }
 
 var e = Object.create({});               // {}
 >e : any
 >Object.create({}) : any
->Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >{} : {}
 
 var o = Object.create(<object>{});       // object
 >o : any
 >Object.create(<object>{}) : any
->Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 ><object>{} : object
 >{} : {}
 
 var a = Object.create(null, {});           // any
 >a : any
 >Object.create(null, {}) : any
->Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >null : null
 >{} : {}
 
 var a = Object.create({ a: 1, b: "" }, {});
 >a : any
 >Object.create({ a: 1, b: "" }, {}) : any
->Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >{ a: 1, b: "" } : { a: number; b: string; }
 >a : number
 >1 : 1
@@ -76,27 +76,27 @@ var a = Object.create({ a: 1, b: "" }, {});
 var a = Object.create(union, {});
 >a : any
 >Object.create(union, {}) : any
->Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >union : { a: number; b: string; }
 >{} : {}
 
 var a = Object.create({}, {});
 >a : any
 >Object.create({}, {}) : any
->Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >{} : {}
 >{} : {}
 
 var a = Object.create(<object>{}, {});
 >a : any
 >Object.create(<object>{}, {}) : any
->Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>Object.create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 >Object : ObjectConstructor
->create : { (o: object): any; (o: object, properties: PropertyDescriptorMap): any; }
+>create : { (o: object): any; (o: object, properties: PropertyDescriptorMap & ThisType<any>): any; }
 ><object>{} : object
 >{} : {}
 >{} : {}