[es6] Partially implement Reflect.preventExtensions.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 8f4915cefd55bbab5f0f19b70a41ad7a08a8e734..fdf2c61c24f652373ed49aace35f1155639a3132 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -164,6 +164,31 @@ typedef ZoneList<Handle<Object> > ZoneObjectList;
   RETURN_ON_EXCEPTION_VALUE(isolate, call, MaybeHandle<T>())
 
 
+// Macros for Maybe.
+
+#define ASSIGN_OR_RETURN_EXCEPTION(isolate, T, dst, call) \
+  T dst;                                                  \

[rossberg, 2015/10/19 14:33:08]

I'm afraid you can't do that, this breaks the macro. It now is not a single
statement anymore.

[neis, 2015/10/20 07:58:35]

Done.

+  do {                                                    \
+    Maybe<T> result_of_the_call = (call);                 \
+    if (result_of_the_call.IsNothing()) {                 \
+      DCHECK((isolate)->has_pending_exception());         \
+      return isolate->heap()->exception();                \
+    }                                                     \
+    dst = result_of_the_call.FromJust();                  \
+  } while (false)
+
+
+#define ASSIGN_OR_RETURN(T, dst, call, value) \
+  T dst;                                      \
+  do {                                        \
+    Maybe<T> result_of_the_call = (call);     \
+    if (result_of_the_call.IsNothing()) {     \
+      return value;                           \
+    }                                         \
+    dst = result_of_the_call.FromJust();      \
+  } while (false)
+
+
 #define FOR_EACH_ISOLATE_ADDRESS_NAME(C)                \
   C(Handler, handler)                                   \
   C(CEntryFP, c_entry_fp)                               \