Patch classes do not need to be finalized

runtime/vm/class_finalizer.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/class_finalizer.h"
 
 #include "vm/code_generator.h"
 #include "vm/flags.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
@@ skipping 2288 matching lines @@
     ASSERT(Array::Handle(cls.functions()).Length() == 0);
   }
 }
 
 
 void ClassFinalizer::FinalizeClass(const Class& cls) {
   HANDLESCOPE(Isolate::Current());
   if (cls.is_finalized()) {
     return;
   }
+  if (cls.is_patch()) {
+    // The fields and functions of a patch class are copied to the
+    // patched class after parsing. There is nothing to finalize.

[Ivan Posva, 2015/01/03 01:14:19]

We should also make sure that we do not waste a class id on the patch class.

[hausner, 2015/01/05 20:56:29]

As per our off-line conversation, I'm leaving this as is. Assigning a class id
is done at the lowest level when allocating a new class object. Changing this
would be outside of this CL.

+    ASSERT(Array::Handle(cls.functions()).Length() == 0);
+    ASSERT(Array::Handle(cls.fields()).Length() == 0);
+    cls.set_is_finalized();
+    return;
+  }
   if (FLAG_trace_class_finalization) {
     OS::Print("Finalize %s\n", cls.ToCString());
   }
   if (cls.IsMixinApplication()) {
     // Copy instance methods and fields from the mixin class.
     // This has to happen before the check whether the methods of
     // the class conflict with inherited methods.
     ApplyMixinMembers(cls);
   }
   // Ensure super class is finalized.
@@ skipping 831 matching lines @@
   ASSERT(fields_array.Length() == ByteBuffer::NumberOfFields());
   field ^= fields_array.At(0);
   ASSERT(field.Offset() == ByteBuffer::data_offset());
   name ^= field.name();
   expected_name ^= String::New("_data");
   ASSERT(String::EqualsIgnoringPrivateKey(name, expected_name));
 #endif
 }
 
 }  // namespace dart