Fix for issue 6623 - Canonicalize implicit static closure objects.

runtime/vm/raw_object.h

 // Copyright (c) 2012, 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.
 
 #ifndef VM_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/globals.h"
 #include "vm/token.h"
@@ skipping 554 matching lines @@
 class RawClosureData : public RawObject {
  private:
   RAW_HEAP_OBJECT_IMPLEMENTATION(ClosureData);
 
   RawObject** from() {
     return reinterpret_cast<RawObject**>(&ptr()->context_scope_);
   }
   RawContextScope* context_scope_;
   RawFunction* parent_function_;  // Enclosing function of this local function.
   RawClass* signature_class_;
-  RawCode* closure_allocation_stub_;  // Stub code for allocation of closures.
+  union {
+    RawInstance* closure_;  // Closure object for static implicit closures.
+    RawCode* closure_allocation_stub_;  // Stub code for allocation of closures.
+  };
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&ptr()->closure_allocation_stub_);
   }
 };
 
 
 class RawRedirectionData : public RawObject {
  private:
   RAW_HEAP_OBJECT_IMPLEMENTATION(RedirectionData);
 
@@ skipping 1028 matching lines @@
          kExternalUint64ArrayCid == kExternalInt8ArrayCid + 7 &&
          kExternalFloat32ArrayCid == kExternalInt8ArrayCid + 8 &&
          kExternalFloat64ArrayCid == kExternalInt8ArrayCid + 9 &&
          kStacktraceCid == kExternalInt8ArrayCid + 10);
   return (index >= kExternalInt8ArrayCid && index <= kExternalFloat64ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_