Fix error message when assigning to a local const variable

runtime/vm/flow_graph_builder.cc

 // 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.
 
 #include "vm/flow_graph_builder.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/ast_printer.h"
 #include "vm/bit_vector.h"
 #include "vm/class_finalizer.h"
@@ skipping 714 matching lines @@
                                     kEmitStoreBarrier);
     Do(store);
     return ExitTempLocalScope(tmp_var);
   } else {
     return new StoreLocalInstr(local, value);
   }
 }
 
 
 Definition* EffectGraphVisitor::BuildLoadLocal(const LocalVariable& local) {
-  if (local.is_captured()) {
+  if (local.IsConst()) {
+    return new ConstantInstr(*local.ConstValue());
+  } else if (local.is_captured()) {
     intptr_t delta =
         owner()->context_level() - local.owner()->context_level();
     ASSERT(delta >= 0);
     Value* context = Bind(new CurrentContextInstr());
     while (delta-- > 0) {
       context = Bind(new LoadFieldInstr(
           context, Context::parent_offset(), Type::ZoneHandle()));
     }
     return new LoadFieldInstr(context,
                               Context::variable_offset(local.index()),
@@ skipping 3173 matching lines @@
                                   LanguageError::kError,
                                   Heap::kNew,
                                   "FlowGraphBuilder Bailout: %s %s",
                                   String::Handle(function.name()).ToCString(),
                                   reason));
   Isolate::Current()->long_jump_base()->Jump(1, error);
 }
 
 
 }  // namespace dart