Fix decorated class methods with Symbol names to emit valid code

internal/transformers/tstransforms/legacydecorators.go

@@ -165,6 +165,23 @@ func (tx *LegacyDecoratorsTransformer) visitParamerDeclaration(node *ast.Paramet
 	return updated
 }
 
+// visitPropertyNameOfClassElement visits the property name of a class element.
+// Computed property names with decorators need hoisting because the name expression
+// must be evaluated once and referenced in both the property definition and the
+// decorator call.
+func (tx *LegacyDecoratorsTransformer) visitPropertyNameOfClassElement(member *ast.Node) *ast.Node {
+	name := member.Name()
+	if ast.IsComputedPropertyName(name) && ast.HasDecorators(member) {
+		expression := tx.Visitor().VisitNode(name.AsComputedPropertyName().Expression)
+		if expression != nil && !transformers.IsSimpleInlineableExpression(expression) {
+			generatedName := tx.Factory().NewGeneratedNameForNode(name)
+			tx.EmitContext().AddVariableDeclaration(generatedName)
+			return tx.Factory().UpdateComputedPropertyName(name.AsComputedPropertyName(), tx.Factory().NewAssignmentExpression(generatedName, expression))
+		}
+	}
+	return tx.Visitor().VisitNode(name)
+}
+
 func (tx *LegacyDecoratorsTransformer) visitPropertyDeclaration(node *ast.PropertyDeclaration) *ast.Node {
 	if (node.Flags & ast.NodeFlagsAmbient) != 0 {
 		return nil
@@ -177,7 +194,7 @@ func (tx *LegacyDecoratorsTransformer) visitPropertyDeclaration(node *ast.Proper
 		tx.Factory().UpdatePropertyDeclaration(
 			node,
 			tx.Visitor().VisitModifiers(node.Modifiers()),
-			tx.Visitor().VisitNode(node.Name()),
+			tx.visitPropertyNameOfClassElement(node.AsNode()),
 			nil,
 			nil,
 			tx.Visitor().VisitNode(node.Initializer),
@@ -191,7 +208,7 @@ func (tx *LegacyDecoratorsTransformer) visitGetAccessorDeclaration(node *ast.Get
 		tx.Factory().UpdateGetAccessorDeclaration(
 			node,
 			tx.Visitor().VisitModifiers(node.Modifiers()),
-			tx.Visitor().VisitNode(node.Name()),
+			tx.visitPropertyNameOfClassElement(node.AsNode()),
 			nil,
 			tx.Visitor().VisitNodes(node.Parameters),
 			nil,
@@ -207,7 +224,7 @@ func (tx *LegacyDecoratorsTransformer) visitSetAccessorDeclaration(node *ast.Set
 		tx.Factory().UpdateSetAccessorDeclaration(
 			node,
 			tx.Visitor().VisitModifiers(node.Modifiers()),
-			tx.Visitor().VisitNode(node.Name()),
+			tx.visitPropertyNameOfClassElement(node.AsNode()),
 			nil,
 			tx.Visitor().VisitNodes(node.Parameters),
 			nil,
@@ -224,7 +241,7 @@ func (tx *LegacyDecoratorsTransformer) visitMethodDeclaration(node *ast.MethodDe
 			node,
 			tx.Visitor().VisitModifiers(node.Modifiers()),
 			node.AsteriskToken,
-			tx.Visitor().VisitNode(node.Name()),
+			tx.visitPropertyNameOfClassElement(node.AsNode()),
 			nil,
 			nil,
 			tx.Visitor().VisitNodes(node.Parameters),

testdata/baselines/reference/compiler/legacyDecoratorSymbolMethodName.js

@@ -0,0 +1,36 @@
+//// [tests/cases/compiler/legacyDecoratorSymbolMethodName.ts] ////
+
+//// [legacyDecoratorSymbolMethodName.ts]
+export class A {
+  @(fakeDecorator as any)
+  [Symbol()]() {}
+}
+
+function fakeDecorator() {}
+
+
+//// [legacyDecoratorSymbolMethodName.js]
+"use strict";
+var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
+    var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
+    if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
+    else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
+    return c > 3 && r && Object.defineProperty(target, key, r), r;
+};
+var __metadata = (this && this.__metadata) || function (k, v) {
+    if (typeof Reflect === "object" && typeof Reflect.metadata === "function") return Reflect.metadata(k, v);
+};
+var _a;
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.A = void 0;
+class A {
+    [_a = Symbol()]() { }
+}
+exports.A = A;
+__decorate([
+    fakeDecorator,
+    __metadata("design:type", Function),
+    __metadata("design:paramtypes", []),
+    __metadata("design:returntype", void 0)
+], A.prototype, _a, null);
+function fakeDecorator() { }

testdata/baselines/reference/compiler/legacyDecoratorSymbolMethodName.symbols

@@ -0,0 +1,17 @@
+//// [tests/cases/compiler/legacyDecoratorSymbolMethodName.ts] ////
+
+=== legacyDecoratorSymbolMethodName.ts ===
+export class A {
+>A : Symbol(A, Decl(legacyDecoratorSymbolMethodName.ts, 0, 0))
+
+  @(fakeDecorator as any)
+>fakeDecorator : Symbol(fakeDecorator, Decl(legacyDecoratorSymbolMethodName.ts, 3, 1))
+
+  [Symbol()]() {}
+>[Symbol()] : Symbol(A[Symbol()], Decl(legacyDecoratorSymbolMethodName.ts, 0, 16))
+>Symbol : Symbol(Symbol, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2019.symbol.d.ts, --, --))
+}
+
+function fakeDecorator() {}
+>fakeDecorator : Symbol(fakeDecorator, Decl(legacyDecoratorSymbolMethodName.ts, 3, 1))
+

testdata/baselines/reference/compiler/legacyDecoratorSymbolMethodName.types

@@ -0,0 +1,20 @@
+//// [tests/cases/compiler/legacyDecoratorSymbolMethodName.ts] ////
+
+=== legacyDecoratorSymbolMethodName.ts ===
+export class A {
+>A : A
+
+  @(fakeDecorator as any)
+>(fakeDecorator as any) : any
+>fakeDecorator as any : any
+>fakeDecorator : () => void
+
+  [Symbol()]() {}
+>[Symbol()] : () => void
+>Symbol() : symbol
+>Symbol : SymbolConstructor
+}
+
+function fakeDecorator() {}
+>fakeDecorator : () => void
+