Emit function name when emitting arrow functions in ES5

src/compiler/transformers/es2015.ts

@@ -424,7 +424,11 @@ namespace ts {
                     return visitFunctionDeclaration(node as FunctionDeclaration);
 
                 case SyntaxKind.ArrowFunction:
-                    return visitArrowFunction(node as ArrowFunction);
+                    let name: string | undefined;
+                    if (node.parent && isVariableDeclaration(node.parent) && isIdentifier(node.parent.name)) {
+                        name = `${node.parent.name.escapedText}`;
+                    }
+                    return visitArrowFunction(node as ArrowFunction, name);
 
                 case SyntaxKind.FunctionExpression:
                     return visitFunctionExpression(node as FunctionExpression);
@@ -1771,7 +1775,7 @@ namespace ts {
          *
          * @param node An ArrowFunction node.
          */
-        function visitArrowFunction(node: ArrowFunction) {
+        function visitArrowFunction(node: ArrowFunction, name?: string) {
             if (node.transformFlags & TransformFlags.ContainsLexicalThis && !(hierarchyFacts & HierarchyFacts.StaticInitializer)) {
                 hierarchyFacts |= HierarchyFacts.CapturedLexicalThis;
             }
@@ -1782,7 +1786,7 @@ namespace ts {
             const func = factory.createFunctionExpression(
                 /*modifiers*/ undefined,
                 /*asteriskToken*/ undefined,
-                /*name*/ undefined,
+                /*name*/ name ? createNonCollidingName(name, node) : undefined,
                 /*typeParameters*/ undefined,
                 visitParameterList(node.parameters, visitor, context),
                 /*type*/ undefined,
@@ -4353,4 +4357,21 @@ namespace ts {
             return isIdentifier(expression) && expression.escapedText === "arguments";
         }
     }
+
+    function createNonCollidingName(name: string, node: Node): string {
+        const identifiers = new Set<string>();
+        forEachFreeIdentifier(node, (identifier) => {
+            identifiers.add(`${identifier.escapedText}`);
+        });
+
+        return createUniqueName(name, 0, identifiers);
+    }
+
+    function createUniqueName(name: string, counter: number, existingNames: Set<string>): string {
+        const fullName = counter === 0 ? name : `${name}_${counter}`;
+        if (!existingNames.has(fullName)) {
+            return fullName;
+        }
+        return createUniqueName(name, counter + 1, existingNames);
+    }
 }

src/compiler/utilities.ts

@@ -7414,4 +7414,27 @@ namespace ts {
     export function escapeSnippetText(text: string): string {
         return text.replace(/\$/gm, "\\$");
     }
+
+    /**
+     * A free identifier is an identifier that can be accessed through name lookup as a local variable.
+     * In the expression `x.y`, `x` is a free identifier, but `y` is not.
+     */
+    export function forEachFreeIdentifier(node: Node, cb: (id: Identifier) => void): void {
+        if (isIdentifier(node) && isFreeIdentifier(node)) cb(node);
+        forEachChild(node, child => forEachFreeIdentifier(child, cb));
+    }
+
+    export function isFreeIdentifier(node: Identifier): boolean {
+        const { parent } = node;
+        switch (parent.kind) {
+            case SyntaxKind.PropertyAccessExpression:
+                return (parent as PropertyAccessExpression).name !== node;
+            case SyntaxKind.BindingElement:
+                return (parent as BindingElement).propertyName !== node;
+            case SyntaxKind.ImportSpecifier:
+                return (parent as ImportSpecifier).propertyName !== node;
+            default:
+                return true;
+        }
+    }
 }

src/services/codefixes/convertToEsModule.ts

@@ -517,29 +517,6 @@ namespace ts.codefix {
         return map;
     }
 
-    /**
-     * A free identifier is an identifier that can be accessed through name lookup as a local variable.
-     * In the expression `x.y`, `x` is a free identifier, but `y` is not.
-     */
-    function forEachFreeIdentifier(node: Node, cb: (id: Identifier) => void): void {
-        if (isIdentifier(node) && isFreeIdentifier(node)) cb(node);
-        node.forEachChild(child => forEachFreeIdentifier(child, cb));
-    }
-
-    function isFreeIdentifier(node: Identifier): boolean {
-        const { parent } = node;
-        switch (parent.kind) {
-            case SyntaxKind.PropertyAccessExpression:
-                return (parent as PropertyAccessExpression).name !== node;
-            case SyntaxKind.BindingElement:
-                return (parent as BindingElement).propertyName !== node;
-            case SyntaxKind.ImportSpecifier:
-                return (parent as ImportSpecifier).propertyName !== node;
-            default:
-                return true;
-        }
-    }
-
     // Node helpers
 
     function functionExpressionToDeclaration(name: string | undefined, additionalModifiers: readonly Modifier[], fn: FunctionExpression | ArrowFunction | MethodDeclaration, useSitesToUnqualify: ESMap<Node, Node> | undefined): FunctionDeclaration {

tests/baselines/reference/ArrowFunction4.js

@@ -4,5 +4,5 @@ var v = (a, b) => {
 };
 
 //// [ArrowFunction4.js]
-var v = function (a, b) {
+var v = function v(a, b) {
 };

tests/baselines/reference/abstractPropertyInConstructor.js

@@ -121,7 +121,7 @@ var AbstractClass = /** @class */ (function () {
         }
         this.cb(str);
         // OK, reference is inside function
-        var innerFunction = function () {
+        var innerFunction = function innerFunction() {
             return _this.prop;
         };
         // OK, references are to another instance

tests/baselines/reference/arrowFunctionContexts.js

@@ -114,7 +114,7 @@ var __extends = (this && this.__extends) || (function () {
 var _this = this;
 // Arrow function used in with statement
 with (window) {
-    var p = function () { return _this; };
+    var p = function p() { return _this; };
 }
 // Arrow function as argument to super call
 var Base = /** @class */ (function () {
@@ -147,16 +147,16 @@ var E;
 // Arrow function as module variable initializer
 var M;
 (function (M) {
-    M.a = function (s) { return ''; };
-    var b = function (s) { return s; };
+    M.a = function a(s) { return ''; };
+    var b = function b(s) { return s; };
 })(M || (M = {}));
 // Repeat above for module members that are functions? (necessary to redo all of them?)
 var M2;
 (function (M2) {
     var _this = this;
     // Arrow function used in with statement
     with (window) {
-        var p = function () { return _this; };
+        var p = function p() { return _this; };
     }
     // Arrow function as argument to super call
     var Base = /** @class */ (function () {
@@ -189,8 +189,8 @@ var M2;
     // Arrow function as module variable initializer
     var M;
     (function (M) {
-        M.a = function (s) { return ''; };
-        var b = function (s) { return s; };
+        M.a = function a(s) { return ''; };
+        var b = function b(s) { return s; };
     })(M || (M = {}));
 })(M2 || (M2 = {}));
 // <Identifier>(ParamList) => { ... } is a generic arrow function

tests/baselines/reference/arrowFunctionExpressions.js

@@ -104,42 +104,42 @@ function tryCatchFn() {
 var a = function (p) { return p.length; };
 var a = function (p) { return p.length; };
 // Identifier => Block is equivalent to(Identifier) => Block
-var b = function (j) { return 0; };
-var b = function (j) { return 0; };
+var b = function b(j) { return 0; };
+var b = function b(j) { return 0; };
 // Identifier => AssignmentExpression is equivalent to(Identifier) => AssignmentExpression
 var c;
-var d = function (n) { return c = n; };
-var d = function (n) { return c = n; };
+var d = function d(n) { return c = n; };
+var d = function d(n) { return c = n; };
 var d;
 // Binding patterns in arrow functions
-var p1 = function (_a) {
+var p1 = function p1(_a) {
     var a = _a[0];
 };
-var p2 = function (_a) {
+var p2 = function p2(_a) {
     var a = _a.slice(0);
 };
-var p3 = function (_a) {
+var p3 = function p3(_a) {
     var a = _a[1];
 };
-var p4 = function (_a) {
+var p4 = function p4(_a) {
     var a = _a.slice(1);
 };
-var p5 = function (_a) {
+var p5 = function p5(_a) {
     var _b = _a[0], a = _b === void 0 ? 1 : _b;
 };
-var p6 = function (_a) {
+var p6 = function p6(_a) {
     var a = _a.a;
 };
-var p7 = function (_a) {
+var p7 = function p7(_a) {
     var b = _a.a.b;
 };
-var p8 = function (_a) {
+var p8 = function p8(_a) {
     var _b = _a.a, a = _b === void 0 ? 1 : _b;
 };
-var p9 = function (_a) {
+var p9 = function p9(_a) {
     var _b = _a.a, _c = _b === void 0 ? { b: 1 } : _b, _d = _c.b, b = _d === void 0 ? 1 : _d;
 };
-var p10 = function (_a) {
+var p10 = function p10(_a) {
     var _b = _a[0], value = _b.value, done = _b.done;
 };
 // Arrow function used in class member initializer
@@ -152,8 +152,8 @@ var MyClass = /** @class */ (function () {
     }
     MyClass.prototype.fn = function () {
         var _this = this;
-        var m = function (n) { return n + 1; };
-        var p = function (n) { return n && _this; };
+        var m = function m(n) { return n + 1; };
+        var p = function p(n) { return n && _this; };
     };
     return MyClass;
 }());
@@ -174,7 +174,7 @@ function someOtherFn() {
 // Arrow function used in nested function in function
 function outerFn() {
     function innerFn() {
-        var arrowFn = function () { };
+        var arrowFn = function arrowFn() { };
         var p = arrowFn();
         var p;
     }
@@ -204,12 +204,12 @@ h.toExponential();
 function tryCatchFn() {
     var _this = this;
     try {
-        var x = function () { return _this; };
+        var x = function x() { return _this; };
     }
     catch (e) {
-        var t = function () { return e + _this; };
+        var t = function t() { return e + _this; };
     }
     finally {
-        var m = function () { return _this + ''; };
+        var m = function m() { return _this + ''; };
     }
 }

tests/baselines/reference/arrowFunctionMissingCurlyWithSemicolon.js

@@ -6,6 +6,6 @@ var square = (x: number) => x * x;
 
 //// [arrowFunctionMissingCurlyWithSemicolon.js]
 // Should error at semicolon.
-var f = function () { return ; };
+var f = function f() { return ; };
 var b = 1 * 2 * 3 * 4;
 var square = function (x) { return x * x; };

tests/baselines/reference/arrowFunctionWithObjectLiteralBody5.js

@@ -10,5 +10,5 @@ var d = () => ((<Error>({ name: "foo", message: "bar" })));
 //// [arrowFunctionWithObjectLiteralBody5.js]
 var a = function () { return ({ name: "foo", message: "bar" }); };
 var b = function () { return ({ name: "foo", message: "bar" }); };
-var c = function () { return ({ name: "foo", message: "bar" }); };
+var c = function c() { return ({ name: "foo", message: "bar" }); };
 var d = function () { return ({ name: "foo", message: "bar" }); };

tests/baselines/reference/arrowFunctionWithParameterNameAsync_es2017.js

@@ -2,4 +2,4 @@
 const x = async => async;
 
 //// [arrowFunctionWithParameterNameAsync_es2017.js]
-var x = function (async) { return async; };
+var x = function x(async) { return async; };

tests/baselines/reference/arrowFunctionWithParameterNameAsync_es5.js

@@ -2,4 +2,4 @@
 const x = async => async;
 
 //// [arrowFunctionWithParameterNameAsync_es5.js]
-var x = function (async) { return async; };
+var x = function x(async) { return async; };

tests/baselines/reference/arrowFunctionWithParameterNameAsync_es6.js

@@ -2,4 +2,4 @@
 const x = async => async;
 
 //// [arrowFunctionWithParameterNameAsync_es6.js]
-var x = function (async) { return async; };
+var x = function x(async) { return async; };

tests/baselines/reference/arrowFunctionsMissingTokens.js

@@ -68,37 +68,37 @@ module okay {
 //// [arrowFunctionsMissingTokens.js]
 var missingArrowsWithCurly;
 (function (missingArrowsWithCurly) {
-    var a = function () { };
+    var a = function a() { };
     var b = function () { };
-    var c = function (x) { };
+    var c = function c(x) { };
     var d = function (x, y) { };
     var e = function (x, y) { };
 })(missingArrowsWithCurly || (missingArrowsWithCurly = {}));
 var missingCurliesWithArrow;
 (function (missingCurliesWithArrow) {
     var withStatement;
     (function (withStatement) {
-        var a = function () { var k = 10; };
+        var a = function a() { var k = 10; };
         var b = function () { var k = 10; };
-        var c = function (x) { var k = 10; };
+        var c = function c(x) { var k = 10; };
         var d = function (x, y) { var k = 10; };
         var e = function (x, y) { var k = 10; };
-        var f = function () { var k = 10; };
+        var f = function f() { var k = 10; };
     })(withStatement || (withStatement = {}));
     var withoutStatement;
     (function (withoutStatement) {
-        var a = function () { return ; };
+        var a = function a() { return ; };
     })(withoutStatement || (withoutStatement = {}));
     ;
     var b = function () { return ; };
 })(missingCurliesWithArrow || (missingCurliesWithArrow = {}));
-var c = function (x) { return ; };
+var c = function c(x) { return ; };
 ;
 var d = function (x, y) { return ; };
 ;
 var e = function (x, y) { return ; };
 ;
-var f = function () { return ; };
+var f = function f() { return ; };
 var ce_nEst_pas_une_arrow_function;
 (function (ce_nEst_pas_une_arrow_function) {
     var a = ();
@@ -109,9 +109,9 @@ var ce_nEst_pas_une_arrow_function;
 })(ce_nEst_pas_une_arrow_function || (ce_nEst_pas_une_arrow_function = {}));
 var okay;
 (function (okay) {
-    var a = function () { };
+    var a = function a() { };
     var b = function () { };
-    var c = function (x) { };
+    var c = function c(x) { };
     var d = function (x, y) { };
     var e = function (x, y) { };
 })(okay || (okay = {}));

tests/baselines/reference/assertionTypePredicates1.js

@@ -213,7 +213,7 @@ var __extends = (this && this.__extends) || (function () {
         d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
     };
 })();
-var assert = function (value) { };
+var assert = function assert(value) { };
 function f01(x) {
     if (!!true) {
         assert(typeof x === "string");

tests/baselines/reference/assertionTypePredicates2.js

@@ -37,12 +37,12 @@ exports.main = void 0;
  * @param {A} a
  * @returns { asserts a is B }
  */
-var foo = function (a) {
+var foo = function foo(a) {
     if ( /** @type { B } */(a).y !== 0)
         throw TypeError();
     return undefined;
 };
-var main = function () {
+var main = function main() {
     /** @type { A } */
     var a = { x: 1 };
     foo(a);

tests/baselines/reference/asyncArrowFunction2_es5.js

@@ -3,5 +3,5 @@ var f = (await) => {
 }
 
 //// [asyncArrowFunction2_es5.js]
-var f = function (await) {
+var f = function f(await) {
 };

tests/baselines/reference/asyncArrowFunction4_es5.js

@@ -3,5 +3,5 @@ var await = () => {
 }
 
 //// [asyncArrowFunction4_es5.js]
-var await = function () {
+var await = function await() {
 };

tests/baselines/reference/asyncMethodWithSuper_es5.js

@@ -92,7 +92,7 @@ var B = /** @class */ (function (_super) {
         return __awaiter(this, void 0, void 0, function () {
             var f, a, b;
             return __generator(this, function (_a) {
-                f = function () { };
+                f = function f() { };
                 // call with property access
                 _super.prototype.x.call(this);
                 // call with element access