Add function name to "not a constructor" errors (#1207)

Include the function name (if known) in the error message, to make
debugging easier. Not a complete fix but still an improvement.

Refs: #991

Author: bnoordhuis

quickjs.c

@@ -7232,6 +7232,25 @@ static JSValue JS_ThrowStackOverflow(JSContext *ctx)
     return JS_ThrowRangeError(ctx, "Maximum call stack size exceeded");
 }
 
+static JSValue JS_ThrowTypeErrorNotAConstructor(JSContext *ctx,
+                                                JSValueConst func_obj)
+{
+    JSObject *p;
+    JSAtom name;
+
+    if (JS_TAG_OBJECT != JS_VALUE_GET_TAG(func_obj))
+        goto fini;
+    p = JS_VALUE_GET_OBJ(func_obj);
+    if (!js_class_has_bytecode(p->class_id))
+        goto fini;
+    name = p->u.func.function_bytecode->func_name;
+    if (name == JS_ATOM_NULL)
+        goto fini;
+    return JS_ThrowTypeErrorAtom(ctx, "%s is not a constructor", name);
+fini:
+    return JS_ThrowTypeError(ctx, "not a constructor");
+}
+
 static JSValue JS_ThrowTypeErrorNotAFunction(JSContext *ctx)
 {
     return JS_ThrowTypeError(ctx, "not a function");
@@ -18822,7 +18841,7 @@ static JSValue JS_CallConstructorInternal(JSContext *ctx,
         goto not_a_function;
     p = JS_VALUE_GET_OBJ(func_obj);
     if (unlikely(!p->is_constructor))
-        return JS_ThrowTypeError(ctx, "not a constructor");
+        return JS_ThrowTypeErrorNotAConstructor(ctx, func_obj);
     if (unlikely(p->class_id != JS_CLASS_BYTECODE_FUNCTION)) {
         JSClassCall *call_func;
         call_func = ctx->rt->class_array[p->class_id].call;
@@ -38668,8 +38687,9 @@ static JSValue JS_SpeciesConstructor(JSContext *ctx, JSValueConst obj,
     if (JS_IsUndefined(species) || JS_IsNull(species))
         return js_dup(defaultConstructor);
     if (!JS_IsConstructor(ctx, species)) {
+        JS_ThrowTypeErrorNotAConstructor(ctx, species);
         JS_FreeValue(ctx, species);
-        return JS_ThrowTypeError(ctx, "not a constructor");
+        return JS_EXCEPTION;
     }
     return species;
 }
@@ -47555,7 +47575,7 @@ static JSValue js_reflect_construct(JSContext *ctx, JSValueConst this_val,
     if (argc > 2) {
         new_target = argv[2];
         if (!JS_IsConstructor(ctx, new_target))
-            return JS_ThrowTypeError(ctx, "not a constructor");
+            return JS_ThrowTypeErrorNotAConstructor(ctx, new_target);
     } else {
         new_target = func;
     }
@@ -48475,7 +48495,7 @@ static JSValue js_proxy_call_constructor(JSContext *ctx, JSValueConst func_obj,
     if (!s)
         return JS_EXCEPTION;
     if (!JS_IsConstructor(ctx, s->target))
-        return JS_ThrowTypeError(ctx, "not a constructor");
+        return JS_ThrowTypeErrorNotAConstructor(ctx, s->target);
     if (JS_IsUndefined(method))
         return JS_CallConstructor2(ctx, s->target, new_target, argc, argv);
     arg_array = js_create_array(ctx, argc, argv);
@@ -48707,7 +48727,7 @@ static JSValue js_symbol_constructor(JSContext *ctx, JSValueConst new_target,
     JSString *p;
 
     if (!JS_IsUndefined(new_target))
-        return JS_ThrowTypeError(ctx, "not a constructor");
+        return JS_ThrowTypeErrorNotAConstructor(ctx, new_target);
     if (argc == 0 || JS_IsUndefined(argv[0])) {
         p = NULL;
     } else {
@@ -53317,7 +53337,7 @@ static JSValue js_bigint_constructor(JSContext *ctx,
                                      int argc, JSValueConst *argv)
 {
     if (!JS_IsUndefined(new_target))
-        return JS_ThrowTypeError(ctx, "not a constructor");
+        return JS_ThrowTypeErrorNotAConstructor(ctx, new_target);
     return JS_ToBigIntCtorFree(ctx, js_dup(argv[0]));
 }
 

tests/test_language.js

@@ -259,6 +259,15 @@ function test_delete()
     assert(err, true, "delete");
 }
 
+function test_constructor()
+{
+    function *G() {}
+    let ex
+    try { new G() } catch (ex_) { ex = ex_ }
+    assert(ex instanceof TypeError)
+    assert(ex.message, "G is not a constructor")
+}
+
 function test_prototype()
 {
     var f = function f() { };
@@ -718,6 +727,7 @@ test_eq();
 test_inc_dec();
 test_op2();
 test_delete();
+test_constructor();
 test_prototype();
 test_arguments();
 test_class();