set prototype in JSON.parse; fixes #578

Author: mmoskal

devs/run-tests/basic.ts

@@ -503,6 +503,14 @@ function testInstanceOf() {
     const obj = {}
     isEq(obj instanceof Object, true)
     isEq(obj instanceof Error, false)
+
+    const json = JSON.parse("{}")
+    isEq(json instanceof Object, true)
+    isEq(json instanceof Error, false)
+
+    const foo = new Foo(12)
+    isEq(foo instanceof Object, true)
+    isEq(foo instanceof Foo, true)
 }
 
 class Foo {

runtime/devicescript/json.c

@@ -270,7 +270,8 @@ static value_t parse_array(parser_t *state) {
 
 static value_t parse_object(parser_t *state) {
     devs_ctx_t *ctx = state->ctx;
-    devs_map_t *arr = devs_map_try_alloc(ctx, 0);
+    devs_map_t *arr =
+        devs_map_try_alloc(ctx, devs_get_builtin_object(ctx, DEVS_BUILTIN_OBJECT_OBJECT_PROTOTYPE));
     if (!arr)
         return devs_undefined;
     value_t ret = devs_value_from_gc_obj(ctx, arr);