Don't contextually type this in exports.f = function() { ... }

Author: Andy Hanson

src/compiler/checker.ts

@@ -12780,7 +12780,8 @@ namespace ts {
                     }
                 }
             }
-            if (noImplicitThis || isInJavaScriptFile(func)) {
+            const inJs = isInJavaScriptFile(func);
+            if (noImplicitThis || inJs) {
                 const containingLiteral = getContainingObjectLiteral(func);
                 if (containingLiteral) {
                     // We have an object literal method. Check if the containing object literal has a contextual type
@@ -12807,10 +12808,20 @@ namespace ts {
                 }
                 // In an assignment of the form 'obj.xxx = function(...)' or 'obj[xxx] = function(...)', the
                 // contextual type for 'this' is 'obj'.
-                if (func.parent.kind === SyntaxKind.BinaryExpression && (<BinaryExpression>func.parent).operatorToken.kind === SyntaxKind.EqualsToken) {
-                    const target = (<BinaryExpression>func.parent).left;
+                const { parent } = func;
+                if (parent.kind === SyntaxKind.BinaryExpression && (<BinaryExpression>parent).operatorToken.kind === SyntaxKind.EqualsToken) {
+                    const target = (<BinaryExpression>parent).left;
                     if (target.kind === SyntaxKind.PropertyAccessExpression || target.kind === SyntaxKind.ElementAccessExpression) {
-                        return checkExpressionCached((<PropertyAccessExpression | ElementAccessExpression>target).expression);
+                        const { expression } = target as PropertyAccessExpression | ElementAccessExpression;
+                        // Don't contextually type `this` as `exports` in `exports.Point = function(x, y) { this.x = x; this.y = y; }`
+                        if (inJs && isIdentifier(expression)) {
+                            const sourceFile = getSourceFileOfNode(parent);
+                            if (sourceFile.commonJsModuleIndicator && getResolvedSymbol(expression) === sourceFile.symbol) {
+                                return undefined;
+                            }
+                        }
+
+                        return checkExpressionCached(expression);
                     }
                 }
             }

tests/baselines/reference/commonjsAccessExports.symbols

@@ -9,3 +9,22 @@ exports.x;
 >exports : Symbol("/a", Decl(a.js, 0, 0))
 >x : Symbol(x, Decl(a.js, 0, 0))
 
+// Works nested
+{
+    // 'exports' does not provide a contextual type to a function-class
+    exports.Cls = function() {
+>exports.Cls : Symbol(Cls, Decl(a.js, 4, 1))
+>exports : Symbol(Cls, Decl(a.js, 4, 1))
+>Cls : Symbol(Cls, Decl(a.js, 4, 1))
+
+        this.x = 0;
+>x : Symbol((Anonymous function).x, Decl(a.js, 6, 30))
+    }
+}
+
+const instance = new exports.Cls();
+>instance : Symbol(instance, Decl(a.js, 11, 5))
+>exports.Cls : Symbol(Cls, Decl(a.js, 4, 1))
+>exports : Symbol("/a", Decl(a.js, 0, 0))
+>Cls : Symbol(Cls, Decl(a.js, 4, 1))
+

tests/baselines/reference/commonjsAccessExports.types

@@ -11,3 +11,29 @@ exports.x;
 >exports : typeof "/a"
 >x : number
 
+// Works nested
+{
+    // 'exports' does not provide a contextual type to a function-class
+    exports.Cls = function() {
+>exports.Cls = function() {        this.x = 0;    } : () => void
+>exports.Cls : () => void
+>exports : typeof "/a"
+>Cls : () => void
+>function() {        this.x = 0;    } : () => void
+
+        this.x = 0;
+>this.x = 0 : 0
+>this.x : any
+>this : any
+>x : any
+>0 : 0
+    }
+}
+
+const instance = new exports.Cls();
+>instance : { x: number; }
+>new exports.Cls() : { x: number; }
+>exports.Cls : () => void
+>exports : typeof "/a"
+>Cls : () => void
+

tests/baselines/reference/typeFromParamTagForFunction.symbols

@@ -8,18 +8,15 @@ declare var module: any, exports: any;
 >exports : Symbol(exports, Decl(node.d.ts, 1, 24))
 
 === tests/cases/conformance/salsa/a-ext.js ===
-function A() {
+exports. A = function() {
+>exports. A : Symbol(A, Decl(a-ext.js, 0, 0))
+>exports : Symbol(A, Decl(a-ext.js, 0, 0))
 >A : Symbol(A, Decl(a-ext.js, 0, 0))
 
     this.x = 1;
->x : Symbol(A.x, Decl(a-ext.js, 0, 14))
+>x : Symbol((Anonymous function).x, Decl(a-ext.js, 0, 25))
 
 };
-exports.A = A;
->exports.A : Symbol(A, Decl(a-ext.js, 2, 2))
->exports : Symbol(A, Decl(a-ext.js, 2, 2))
->A : Symbol(A, Decl(a-ext.js, 2, 2))
->A : Symbol(A, Decl(a-ext.js, 0, 0))
 
 === tests/cases/conformance/salsa/a.js ===
 const { A } = require("./a-ext");
@@ -31,9 +28,9 @@ const { A } = require("./a-ext");
 function a(p) { p.x; }
 >a : Symbol(a, Decl(a.js, 0, 33))
 >p : Symbol(p, Decl(a.js, 3, 11))
->p.x : Symbol(A.x, Decl(a-ext.js, 0, 14))
+>p.x : Symbol((Anonymous function).x, Decl(a-ext.js, 0, 25))
 >p : Symbol(p, Decl(a.js, 3, 11))
->x : Symbol(A.x, Decl(a-ext.js, 0, 14))
+>x : Symbol((Anonymous function).x, Decl(a-ext.js, 0, 25))
 
 === tests/cases/conformance/salsa/b-ext.js ===
 exports.B = class {

tests/baselines/reference/typeFromParamTagForFunction.types

@@ -8,8 +8,12 @@ declare var module: any, exports: any;
 >exports : any
 
 === tests/cases/conformance/salsa/a-ext.js ===
-function A() {
+exports. A = function() {
+>exports. A = function() {    this.x = 1;} : () => void
+>exports. A : () => void
+>exports : typeof "tests/cases/conformance/salsa/a-ext"
 >A : () => void
+>function() {    this.x = 1;} : () => void
 
     this.x = 1;
 >this.x = 1 : 1
@@ -19,12 +23,6 @@ function A() {
 >1 : 1
 
 };
-exports.A = A;
->exports.A = A : () => void
->exports.A : () => void
->exports : typeof "tests/cases/conformance/salsa/a-ext"
->A : () => void
->A : () => void
 
 === tests/cases/conformance/salsa/a.js ===
 const { A } = require("./a-ext");

tests/cases/compiler/commonjsAccessExports.ts

@@ -6,3 +6,13 @@
 // @Filename: /a.js
 exports.x = 0;
 exports.x;
+
+// Works nested
+{
+    // 'exports' does not provide a contextual type to a function-class
+    exports.Cls = function() {
+        this.x = 0;
+    }
+}
+
+const instance = new exports.Cls();

tests/cases/conformance/salsa/typeFromParamTagForFunction.ts

@@ -7,10 +7,9 @@ declare function require(id: string): any;
 declare var module: any, exports: any;
 
 // @filename: a-ext.js
-function A() {
+exports. A = function() {
     this.x = 1;
 };
-exports.A = A;
 
 // @filename: a.js
 const { A } = require("./a-ext");