Transform call expressions on private names to properly bind this

src/compiler/transformers/esnext.ts

@@ -165,6 +165,8 @@ namespace ts {
                     return visitVariableStatement(node as VariableStatement);
                 case SyntaxKind.ComputedPropertyName:
                     return visitComputedPropertyName(node as ComputedPropertyName);
+                case SyntaxKind.CallExpression:
+                    return visitCallExpression(node as CallExpression);
                 default:
                     return visitEachChild(node, visitor, context);
             }
@@ -606,6 +608,40 @@ namespace ts {
             return visitEachChild(node, visitor, context);
         }
 
+        function visitCallExpression(node: CallExpression) {
+            if (isPrivateNamedPropertyAccess(node.expression)) {
+                // Transform call expressions of private names to properly bind the `this` parameter.
+                let exprForPropertyAccess: Expression = node.expression.expression;
+                let receiver = node.expression.expression;
+                if (!isSimpleInlineableExpression(node.expression.expression)) {
+                    const generatedName = getGeneratedNameForNode(node);
+                    hoistVariableDeclaration(generatedName);
+                    exprForPropertyAccess = setOriginalNode(
+                        createAssignment(generatedName, exprForPropertyAccess),
+                        node.expression.expression
+                    );
+                    receiver = generatedName;
+                }
+                return visitNode(
+                    updateCall(
+                        node,
+                        createPropertyAccess(
+                            updatePropertyAccess(
+                                node.expression,
+                                exprForPropertyAccess,
+                                node.expression.name
+                            ),
+                            "call"
+                        ),
+                        /*typeArguments*/ undefined,
+                        [receiver, ...node.arguments]
+                    ),
+                    visitor
+                );
+            }
+            return visitEachChild(node, visitor, context);
+        }
+
         function enableSubstitutionForClassAliases() {
             if ((enabledSubstitutions & ESNextSubstitutionFlags.ClassAliases) === 0) {
                 enabledSubstitutions |= ESNextSubstitutionFlags.ClassAliases;

tests/baselines/reference/privateNameFieldCallExpression.js

@@ -0,0 +1,29 @@
+//// [privateNameFieldCallExpression.ts]
+class A {
+    #fieldFunc = () => this.x = 10;
+    x = 1;
+    test() {
+        this.#fieldFunc();
+        const func = this.#fieldFunc;
+        func();
+    }
+}
+
+
+//// [privateNameFieldCallExpression.js]
+var _classPrivateFieldGet = function (receiver, privateMap) { if (!privateMap.has(receiver)) { throw new TypeError("attempted to get private field on non-instance"); } return privateMap.get(receiver); };
+var _fieldFunc;
+var A = /** @class */ (function () {
+    function A() {
+        var _this = this;
+        _fieldFunc.set(this, function () { return _this.x = 10; });
+        this.x = 1;
+    }
+    A.prototype.test = function () {
+        _classPrivateFieldGet(this, _fieldFunc).call(this);
+        var func = _classPrivateFieldGet(this, _fieldFunc);
+        func();
+    };
+    return A;
+}());
+_fieldFunc = new WeakMap();

tests/baselines/reference/privateNameFieldCallExpression.symbols

@@ -0,0 +1,30 @@
+=== tests/cases/conformance/classes/members/privateNames/privateNameFieldCallExpression.ts ===
+class A {
+>A : Symbol(A, Decl(privateNameFieldCallExpression.ts, 0, 0))
+
+    #fieldFunc = () => this.x = 10;
+>#fieldFunc : Symbol(A[#fieldFunc], Decl(privateNameFieldCallExpression.ts, 0, 9))
+>this.x : Symbol(A.x, Decl(privateNameFieldCallExpression.ts, 1, 35))
+>this : Symbol(A, Decl(privateNameFieldCallExpression.ts, 0, 0))
+>x : Symbol(A.x, Decl(privateNameFieldCallExpression.ts, 1, 35))
+
+    x = 1;
+>x : Symbol(A.x, Decl(privateNameFieldCallExpression.ts, 1, 35))
+
+    test() {
+>test : Symbol(A.test, Decl(privateNameFieldCallExpression.ts, 2, 10))
+
+        this.#fieldFunc();
+>this.#fieldFunc : Symbol(A[#fieldFunc], Decl(privateNameFieldCallExpression.ts, 0, 9))
+>this : Symbol(A, Decl(privateNameFieldCallExpression.ts, 0, 0))
+
+        const func = this.#fieldFunc;
+>func : Symbol(func, Decl(privateNameFieldCallExpression.ts, 5, 13))
+>this.#fieldFunc : Symbol(A[#fieldFunc], Decl(privateNameFieldCallExpression.ts, 0, 9))
+>this : Symbol(A, Decl(privateNameFieldCallExpression.ts, 0, 0))
+
+        func();
+>func : Symbol(func, Decl(privateNameFieldCallExpression.ts, 5, 13))
+    }
+}
+

tests/baselines/reference/privateNameFieldCallExpression.types

@@ -0,0 +1,36 @@
+=== tests/cases/conformance/classes/members/privateNames/privateNameFieldCallExpression.ts ===
+class A {
+>A : A
+
+    #fieldFunc = () => this.x = 10;
+>#fieldFunc : () => number
+>() => this.x = 10 : () => number
+>this.x = 10 : 10
+>this.x : number
+>this : this
+>x : number
+>10 : 10
+
+    x = 1;
+>x : number
+>1 : 1
+
+    test() {
+>test : () => void
+
+        this.#fieldFunc();
+>this.#fieldFunc() : number
+>this.#fieldFunc : () => number
+>this : this
+
+        const func = this.#fieldFunc;
+>func : () => number
+>this.#fieldFunc : () => number
+>this : this
+
+        func();
+>func() : number
+>func : () => number
+    }
+}
+

tests/cases/conformance/classes/members/privateNames/privateNameFieldCallExpression.ts

@@ -0,0 +1,9 @@
+class A {
+    #fieldFunc = () => this.x = 10;
+    x = 1;
+    test() {
+        this.#fieldFunc();
+        const func = this.#fieldFunc;
+        func();
+    }
+}