Use a VariableUse instead of VariableDeclaration for left-hand side of

pkg/compiler/lib/src/js/rewrite_async.dart

 // Copyright (c) 2015, 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.
 
 library rewrite_async;
 
 // TODO(sigurdm): Throws in catch-handlers are handled wrong.
 // TODO(sigurdm): Avoid using variables in templates. It could blow up memory
 // use.
 
@@ skipping 1595 matching lines @@
   @override
   void visitVariableDeclarationList(js.VariableDeclarationList node) {
     // Declaration of local variables is hoisted outside the helper but the
     // initialization is done here.
     for (js.VariableInitialization initialization in node.declarations) {
       js.VariableDeclaration declaration = initialization.declaration;
       localVariables.add(declaration);
       if (initialization.value != null) {
         withExpression(initialization.value, (js.Expression value) {
           addStatement(new js.ExpressionStatement(
-              new js.Assignment(declaration, value)));
+              new js.Assignment(new js.VariableUse(declaration.name), value)));
         }, store: false);
       }
     }
   }
 
   @override
   void visitVariableInitialization(js.VariableInitialization node) {
     unreachable(node);
   }
 
@@ skipping 517 matching lines @@
     loopsAndSwitches.removeLast();
     return condition || body;
   }
 
   @override
   bool visitDartYield(js.DartYield node) {
     visit(node.expression);
     return true;
   }
 }