Implement const expressions for local variables

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 876 matching lines @@
 
 class RawContextScope : public RawObject {
   RAW_HEAP_OBJECT_IMPLEMENTATION(ContextScope);
 
   // TODO(iposva): Switch to convential enum offset based structure to avoid
   // alignment mishaps.
   struct VariableDesc {
     RawSmi* token_pos;
     RawString* name;
     RawBool* is_final;
-    RawAbstractType* type;
+    RawBool* is_const;
+    union {
+      RawAbstractType* type;
+      RawInstance* value;  // iff is_const is true
+    };
     RawSmi* context_index;
     RawSmi* context_level;
   };
 
   intptr_t num_variables_;
 
   // Variable length data follows here.
   RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->data_[0]); }
   RawObject* data_[0];
   RawObject** to(intptr_t num_vars) {
@@ skipping 702 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_