Merge pull request #17252 from Microsoft/contextually-type-this-in-object-literals-in-javascript

Contextually type this in object literals in JS

Author: sandersn

src/compiler/checker.ts

@@ -12662,7 +12662,7 @@ namespace ts {
                     }
                 }
             }
-            if (noImplicitThis) {
+            if (noImplicitThis || isInJavaScriptFile(func)) {
                 const containingLiteral = getContainingObjectLiteral(func);
                 if (containingLiteral) {
                     // We have an object literal method. Check if the containing object literal has a contextual type

tests/baselines/reference/contextualThisTypeInJavascript.symbols

@@ -0,0 +1,28 @@
+=== tests/cases/conformance/types/thisType/context.js ===
+const obj = {
+>obj : Symbol(obj, Decl(context.js, 0, 5))
+
+    prop: 2,
+>prop : Symbol(prop, Decl(context.js, 0, 13))
+
+    method() {
+>method : Symbol(method, Decl(context.js, 1, 12))
+
+        this;
+>this : Symbol(obj, Decl(context.js, 0, 11))
+
+        this.prop;
+>this.prop : Symbol(prop, Decl(context.js, 0, 13))
+>this : Symbol(obj, Decl(context.js, 0, 11))
+>prop : Symbol(prop, Decl(context.js, 0, 13))
+
+        this.method;
+>this.method : Symbol(method, Decl(context.js, 1, 12))
+>this : Symbol(obj, Decl(context.js, 0, 11))
+>method : Symbol(method, Decl(context.js, 1, 12))
+
+        this.unknown; // ok, obj has a string indexer
+>this : Symbol(obj, Decl(context.js, 0, 11))
+    }
+}
+

tests/baselines/reference/contextualThisTypeInJavascript.types

@@ -0,0 +1,32 @@
+=== tests/cases/conformance/types/thisType/context.js ===
+const obj = {
+>obj : { [x: string]: any; prop: number; method(): void; }
+>{    prop: 2,    method() {        this;        this.prop;        this.method;        this.unknown; // ok, obj has a string indexer    }} : { [x: string]: any; prop: number; method(): void; }
+
+    prop: 2,
+>prop : number
+>2 : 2
+
+    method() {
+>method : () => void
+
+        this;
+>this : { [x: string]: any; prop: number; method(): void; }
+
+        this.prop;
+>this.prop : number
+>this : { [x: string]: any; prop: number; method(): void; }
+>prop : number
+
+        this.method;
+>this.method : () => void
+>this : { [x: string]: any; prop: number; method(): void; }
+>method : () => void
+
+        this.unknown; // ok, obj has a string indexer
+>this.unknown : any
+>this : { [x: string]: any; prop: number; method(): void; }
+>unknown : any
+    }
+}
+

tests/cases/conformance/types/thisType/contextualThisTypeInJavascript.ts

@@ -0,0 +1,13 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @Filename: context.js
+const obj = {
+    prop: 2,
+    method() {
+        this;
+        this.prop;
+        this.method;
+        this.unknown; // ok, obj has a string indexer
+    }
+}