Allow accessor properties in ambient contexts when targeting ES5

src/compiler/checker.ts

@@ -53029,7 +53029,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             if (languageVersion < ScriptTarget.ES2015 && isPrivateIdentifier(node.name)) {
                 return grammarErrorOnNode(node.name, Diagnostics.Private_identifiers_are_only_available_when_targeting_ECMAScript_2015_and_higher);
             }
-            if (languageVersion < ScriptTarget.ES2015 && isAutoAccessorPropertyDeclaration(node)) {
+            if (languageVersion < ScriptTarget.ES2015 && isAutoAccessorPropertyDeclaration(node) && !(node.flags & NodeFlags.Ambient)) {
                 return grammarErrorOnNode(node.name, Diagnostics.Properties_with_the_accessor_modifier_are_only_available_when_targeting_ECMAScript_2015_and_higher);
             }
             if (isAutoAccessorPropertyDeclaration(node) && checkGrammarForInvalidQuestionMark(node.questionToken, Diagnostics.An_accessor_property_cannot_be_declared_optional)) {

tests/baselines/reference/accessorInAmbientContextES5.errors.txt

@@ -0,0 +1,32 @@
+accessorInAmbientContextES5.ts(25,14): error TS18045: Properties with the 'accessor' modifier are only available when targeting ECMAScript 2015 and higher.
+
+
+==== accessorInAmbientContextES5.ts (1 errors) ====
+    // Should allow accessor in ambient contexts even when targeting ES5
+
+    declare class AmbientClass {
+        accessor prop1: string;
+        static accessor prop2: number;
+        private accessor prop3: boolean;
+        private static accessor prop4: symbol;
+    }
+
+    declare namespace AmbientNamespace {
+        class C {
+            accessor prop: string;
+        }
+    }
+
+    // Should also work in .d.ts files (simulated with declare)
+    declare module "some-module" {
+        export class ExportedClass {
+            accessor value: any;
+        }
+    }
+
+    // Regular class should still error when targeting ES5
+    class RegularClass {
+        accessor shouldError: string; // Should still error
+                 ~~~~~~~~~~~
+!!! error TS18045: Properties with the 'accessor' modifier are only available when targeting ECMAScript 2015 and higher.
+    }

tests/baselines/reference/accessorInAmbientContextES5.js

@@ -0,0 +1,81 @@
+//// [tests/cases/compiler/accessorInAmbientContextES5.ts] ////
+
+//// [accessorInAmbientContextES5.ts]
+// Should allow accessor in ambient contexts even when targeting ES5
+
+declare class AmbientClass {
+    accessor prop1: string;
+    static accessor prop2: number;
+    private accessor prop3: boolean;
+    private static accessor prop4: symbol;
+}
+
+declare namespace AmbientNamespace {
+    class C {
+        accessor prop: string;
+    }
+}
+
+// Should also work in .d.ts files (simulated with declare)
+declare module "some-module" {
+    export class ExportedClass {
+        accessor value: any;
+    }
+}
+
+// Regular class should still error when targeting ES5
+class RegularClass {
+    accessor shouldError: string; // Should still error
+}
+
+//// [accessorInAmbientContextES5.js]
+// Should allow accessor in ambient contexts even when targeting ES5
+var __classPrivateFieldGet = (this && this.__classPrivateFieldGet) || function (receiver, state, kind, f) {
+    if (kind === "a" && !f) throw new TypeError("Private accessor was defined without a getter");
+    if (typeof state === "function" ? receiver !== state || !f : !state.has(receiver)) throw new TypeError("Cannot read private member from an object whose class did not declare it");
+    return kind === "m" ? f : kind === "a" ? f.call(receiver) : f ? f.value : state.get(receiver);
+};
+var __classPrivateFieldSet = (this && this.__classPrivateFieldSet) || function (receiver, state, value, kind, f) {
+    if (kind === "m") throw new TypeError("Private method is not writable");
+    if (kind === "a" && !f) throw new TypeError("Private accessor was defined without a setter");
+    if (typeof state === "function" ? receiver !== state || !f : !state.has(receiver)) throw new TypeError("Cannot write private member to an object whose class did not declare it");
+    return (kind === "a" ? f.call(receiver, value) : f ? f.value = value : state.set(receiver, value)), value;
+};
+var _RegularClass_shouldError_accessor_storage;
+// Regular class should still error when targeting ES5
+var RegularClass = /** @class */ (function () {
+    function RegularClass() {
+        _RegularClass_shouldError_accessor_storage.set(this, void 0);
+    }
+    Object.defineProperty(RegularClass.prototype, "shouldError", {
+        get: function () { return __classPrivateFieldGet(this, _RegularClass_shouldError_accessor_storage, "f"); } // Should still error
+        ,
+        set: function (value) { __classPrivateFieldSet(this, _RegularClass_shouldError_accessor_storage, value, "f"); },
+        enumerable: false,
+        configurable: true
+    });
+    return RegularClass;
+}());
+_RegularClass_shouldError_accessor_storage = new WeakMap();
+
+
+//// [accessorInAmbientContextES5.d.ts]
+declare class AmbientClass {
+    accessor prop1: string;
+    static accessor prop2: number;
+    private accessor prop3;
+    private static accessor prop4;
+}
+declare namespace AmbientNamespace {
+    class C {
+        accessor prop: string;
+    }
+}
+declare module "some-module" {
+    class ExportedClass {
+        accessor value: any;
+    }
+}
+declare class RegularClass {
+    accessor shouldError: string;
+}

tests/baselines/reference/accessorInAmbientContextES5.symbols

@@ -0,0 +1,51 @@
+//// [tests/cases/compiler/accessorInAmbientContextES5.ts] ////
+
+=== accessorInAmbientContextES5.ts ===
+// Should allow accessor in ambient contexts even when targeting ES5
+
+declare class AmbientClass {
+>AmbientClass : Symbol(AmbientClass, Decl(accessorInAmbientContextES5.ts, 0, 0))
+
+    accessor prop1: string;
+>prop1 : Symbol(AmbientClass.prop1, Decl(accessorInAmbientContextES5.ts, 2, 28))
+
+    static accessor prop2: number;
+>prop2 : Symbol(AmbientClass.prop2, Decl(accessorInAmbientContextES5.ts, 3, 27))
+
+    private accessor prop3: boolean;
+>prop3 : Symbol(AmbientClass.prop3, Decl(accessorInAmbientContextES5.ts, 4, 34))
+
+    private static accessor prop4: symbol;
+>prop4 : Symbol(AmbientClass.prop4, Decl(accessorInAmbientContextES5.ts, 5, 36))
+}
+
+declare namespace AmbientNamespace {
+>AmbientNamespace : Symbol(AmbientNamespace, Decl(accessorInAmbientContextES5.ts, 7, 1))
+
+    class C {
+>C : Symbol(C, Decl(accessorInAmbientContextES5.ts, 9, 36))
+
+        accessor prop: string;
+>prop : Symbol(C.prop, Decl(accessorInAmbientContextES5.ts, 10, 13))
+    }
+}
+
+// Should also work in .d.ts files (simulated with declare)
+declare module "some-module" {
+>"some-module" : Symbol("some-module", Decl(accessorInAmbientContextES5.ts, 13, 1))
+
+    export class ExportedClass {
+>ExportedClass : Symbol(ExportedClass, Decl(accessorInAmbientContextES5.ts, 16, 30))
+
+        accessor value: any;
+>value : Symbol(ExportedClass.value, Decl(accessorInAmbientContextES5.ts, 17, 32))
+    }
+}
+
+// Regular class should still error when targeting ES5
+class RegularClass {
+>RegularClass : Symbol(RegularClass, Decl(accessorInAmbientContextES5.ts, 20, 1))
+
+    accessor shouldError: string; // Should still error
+>shouldError : Symbol(RegularClass.shouldError, Decl(accessorInAmbientContextES5.ts, 23, 20))
+}

tests/baselines/reference/accessorInAmbientContextES5.types

@@ -0,0 +1,64 @@
+//// [tests/cases/compiler/accessorInAmbientContextES5.ts] ////
+
+=== accessorInAmbientContextES5.ts ===
+// Should allow accessor in ambient contexts even when targeting ES5
+
+declare class AmbientClass {
+>AmbientClass : AmbientClass
+>             : ^^^^^^^^^^^^
+
+    accessor prop1: string;
+>prop1 : string
+>      : ^^^^^^
+
+    static accessor prop2: number;
+>prop2 : number
+>      : ^^^^^^
+
+    private accessor prop3: boolean;
+>prop3 : boolean
+>      : ^^^^^^^
+
+    private static accessor prop4: symbol;
+>prop4 : symbol
+>      : ^^^^^^
+}
+
+declare namespace AmbientNamespace {
+>AmbientNamespace : typeof AmbientNamespace
+>                 : ^^^^^^^^^^^^^^^^^^^^^^^
+
+    class C {
+>C : C
+>  : ^
+
+        accessor prop: string;
+>prop : string
+>     : ^^^^^^
+    }
+}
+
+// Should also work in .d.ts files (simulated with declare)
+declare module "some-module" {
+>"some-module" : typeof import("some-module")
+>              : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+    export class ExportedClass {
+>ExportedClass : ExportedClass
+>              : ^^^^^^^^^^^^^
+
+        accessor value: any;
+>value : any
+>      : ^^^
+    }
+}
+
+// Regular class should still error when targeting ES5
+class RegularClass {
+>RegularClass : RegularClass
+>             : ^^^^^^^^^^^^
+
+    accessor shouldError: string; // Should still error
+>shouldError : string
+>            : ^^^^^^
+}

tests/cases/compiler/accessorInAmbientContextES5.ts

@@ -0,0 +1,29 @@
+// @target: es5
+// @declaration: true
+
+// Should allow accessor in ambient contexts even when targeting ES5
+
+declare class AmbientClass {
+    accessor prop1: string;
+    static accessor prop2: number;
+    private accessor prop3: boolean;
+    private static accessor prop4: symbol;
+}
+
+declare namespace AmbientNamespace {
+    class C {
+        accessor prop: string;
+    }
+}
+
+// Should also work in .d.ts files (simulated with declare)
+declare module "some-module" {
+    export class ExportedClass {
+        accessor value: any;
+    }
+}
+
+// Regular class should still error when targeting ES5
+class RegularClass {
+    accessor shouldError: string; // Should still error
+}