Fix Iterator.prototype.constructor (#1060)

TC39 in its wisdom decided the property should be an accessor with a
setter that enforces certain properties on the set value. Make it so.

Author: bnoordhuis

quickjs.c

@@ -454,6 +454,7 @@ struct JSContext {
     JSValue error_prepare_stack;
     JSValue error_stack_trace_limit;
     JSValue iterator_ctor;
+    JSValue iterator_ctor_getset;
     JSValue iterator_proto;
     JSValue async_iterator_proto;
     JSValue array_proto_values;
@@ -2303,6 +2304,7 @@ JSContext *JS_NewContextRaw(JSRuntime *rt)
         ctx->class_proto[i] = JS_NULL;
     ctx->array_ctor = JS_NULL;
     ctx->iterator_ctor = JS_NULL;
+    ctx->iterator_ctor_getset = JS_NULL;
     ctx->regexp_ctor = JS_NULL;
     ctx->promise_ctor = JS_NULL;
     ctx->error_ctor = JS_NULL;
@@ -2433,6 +2435,7 @@ static void JS_MarkContext(JSRuntime *rt, JSContext *ctx,
         JS_MarkValue(rt, ctx->class_proto[i], mark_func);
     }
     JS_MarkValue(rt, ctx->iterator_ctor, mark_func);
+    JS_MarkValue(rt, ctx->iterator_ctor_getset, mark_func);
     JS_MarkValue(rt, ctx->async_iterator_proto, mark_func);
     JS_MarkValue(rt, ctx->promise_ctor, mark_func);
     JS_MarkValue(rt, ctx->array_ctor, mark_func);
@@ -2503,6 +2506,7 @@ void JS_FreeContext(JSContext *ctx)
     }
     js_free_rt(rt, ctx->class_proto);
     JS_FreeValue(ctx, ctx->iterator_ctor);
+    JS_FreeValue(ctx, ctx->iterator_ctor_getset);
     JS_FreeValue(ctx, ctx->async_iterator_proto);
     JS_FreeValue(ctx, ctx->promise_ctor);
     JS_FreeValue(ctx, ctx->array_ctor);
@@ -41672,6 +41676,26 @@ static const JSCFunctionListEntry js_iterator_wrap_proto_funcs[] = {
     JS_ITERATOR_NEXT_DEF("return", 0, js_iterator_wrap_next, GEN_MAGIC_RETURN ),
 };
 
+static JSValue js_iterator_constructor_getset(JSContext *ctx,
+                                              JSValueConst this_val,
+                                              int argc, JSValueConst *argv,
+                                              int magic,
+                                              JSValueConst *func_data)
+{
+    int ret;
+
+    if (argc > 0) { // if setter
+        if (!JS_IsObject(argv[0]))
+            return JS_ThrowTypeErrorNotAnObject(ctx);
+        ret = JS_DefinePropertyValue(ctx, this_val, JS_ATOM_constructor,
+                                     js_dup(argv[0]),
+                                     JS_PROP_WRITABLE | JS_PROP_CONFIGURABLE);
+        if (ret < 0)
+            return JS_EXCEPTION;
+    }
+    return js_dup(func_data[0]);
+}
+
 static JSValue js_iterator_constructor(JSContext *ctx, JSValueConst new_target,
                                        int argc, JSValueConst *argv)
 {
@@ -53275,6 +53299,16 @@ void JS_AddIntrinsicBaseObjects(JSContext *ctx)
                                countof(js_iterator_proto_funcs));
     obj = JS_NewGlobalCConstructor(ctx, "Iterator", js_iterator_constructor, 0,
                                    ctx->class_proto[JS_CLASS_ITERATOR]);
+    // quirk: Iterator.prototype.constructor is an accessor property
+    // TODO(bnoordhuis) mildly inefficient because JS_NewGlobalCConstructor
+    // first creates a .constructor value property that we then replace with
+    // an accessor
+    ctx->iterator_ctor_getset = JS_NewCFunctionData(ctx, js_iterator_constructor_getset,
+                                                    0, 0, 1, vc(&obj));
+    JS_DefineProperty(ctx, ctx->class_proto[JS_CLASS_ITERATOR],
+                      JS_ATOM_constructor, JS_UNDEFINED,
+                      ctx->iterator_ctor_getset, ctx->iterator_ctor_getset,
+                      JS_PROP_HAS_GET|JS_PROP_HAS_SET|JS_PROP_WRITABLE|JS_PROP_CONFIGURABLE);
     ctx->iterator_ctor = js_dup(obj);
     JS_SetPropertyFunctionList(ctx, obj,
                                js_iterator_funcs,

test262_errors.txt

@@ -24,10 +24,6 @@ test262/test/built-ins/AsyncFromSyncIteratorPrototype/throw/throw-undefined-retu
 test262/test/built-ins/AsyncFromSyncIteratorPrototype/throw/throw-undefined-return-not-object.js:72: strict mode: TypeError: $DONE() not called
 test262/test/built-ins/AsyncFromSyncIteratorPrototype/throw/throw-undefined-return-object.js:66: TypeError: $DONE() not called
 test262/test/built-ins/AsyncFromSyncIteratorPrototype/throw/throw-undefined-return-object.js:66: strict mode: TypeError: $DONE() not called
-test262/test/built-ins/Iterator/prototype/constructor/prop-desc.js:10: Test262Error: Expected SameValue(«"undefined"», «"function"») to be true
-test262/test/built-ins/Iterator/prototype/constructor/prop-desc.js:10: strict mode: Test262Error: Expected SameValue(«"undefined"», «"function"») to be true
-test262/test/built-ins/Iterator/prototype/constructor/weird-setter.js:23: TypeError: cannot read property 'call' of undefined
-test262/test/built-ins/Iterator/prototype/constructor/weird-setter.js:23: strict mode: TypeError: cannot read property 'call' of undefined
 test262/test/built-ins/Object/defineProperties/typedarray-backed-by-resizable-buffer.js:20: Test262Error: Expected a TypeError to be thrown but no exception was thrown at all
 test262/test/built-ins/Object/defineProperties/typedarray-backed-by-resizable-buffer.js:20: strict mode: Test262Error: Expected a TypeError to be thrown but no exception was thrown at all
 test262/test/built-ins/Object/defineProperty/coerced-P-grow.js:45: TypeError: out-of-bound index in typed array