Add Dart_IsFuture. To be used in Dartium implementation of Promises.

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index d354726ad32fc1ed15a940ca264be2b9e9582e1f..24ec09d5621d05aef4591a065457f819b04b5273 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -1870,6 +1870,29 @@ DART_EXPORT bool Dart_IsByteBuffer(Dart_Handle handle) {
 }
 
 
+DART_EXPORT bool Dart_IsFuture(Dart_Handle handle) {
+  TRACE_API_CALL(CURRENT_FUNC);
+  Isolate* isolate = Isolate::Current();
+  DARTSCOPE(isolate);
+  const Object& obj = Object::Handle(isolate, Api::UnwrapHandle(handle));
+  if (obj.IsInstance()) {

[siva, 2014/09/19 17:38:35]

ReusableObjectHandleScope reused_obj_handle(isolate);
const Instance& obj = Api::UnwrapInstanceHandle(reused_obj, handle);
if (!obj.IsNull() {
  ...
  ...
}
return false;

[rmacnak, 2014/09/19 21:32:02]

Trips the assert as the reusable handle is used in LookupClass.

[siva, 2014/09/19 21:59:37]

In that case you could restructure it as:

Class obj_classs = Class::Handle(isolate);
{
  ReusableObjectHandleScope reused_obj_handle(isolate);
  const Instance& obj = Api::UnwrapInstanceHandle(reused_obj, handle);
  if (obj.IsNull() {
    return false;
  }
  obj_class ^= obj.clazz();
}
....
....
....
return is_future;

+    const Library& core_lib = Library::Handle(Library::AsyncLibrary());

[siva, 2014/09/19 17:38:35]

replace core_lib with async_lib for the variable name.

[rmacnak, 2014/09/19 21:32:03]

Done.

+    const Class& future_class =
+        Class::Handle(core_lib.LookupClass(Symbols::Future()));

[siva, 2014/09/19 17:38:35]

Class::Handle(isolate, ....);

[rmacnak, 2014/09/19 21:32:02]

Done.

+    ASSERT(!future_class.IsNull());
+    const Class& obj_class = Class::Handle(isolate, obj.clazz());
+    Error& malformed_type_error = Error::Handle(isolate);
+    bool is_future = obj_class.IsSubtypeOf(TypeArguments::Handle(isolate),

[siva, 2014/09/19 17:38:36]

IsSubTypeOf(Object::null_type_arguments(),
            future_class,
            Object::null_type_arguments(),
            &malformed_type_error);

[rmacnak, 2014/09/19 21:32:02]

Done. (And two other occurrences in this file.)

+                                           future_class,
+                                           TypeArguments::Handle(isolate),
+                                           &malformed_type_error);
+    ASSERT(malformed_type_error.IsNull());  // Type is a raw Future.
+    return is_future;
+  }
+  return false;
+}
+
+
 // --- Instances ----
 
 DART_EXPORT Dart_Handle Dart_InstanceGetType(Dart_Handle instance) {