Implement correct scope of for-in expression.

pkg/fasta/lib/src/kernel/body_builder.dart

 // Copyright (c) 2016, 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 fasta.body_builder;
 
 import 'package:dart_parser/src/parser.dart' show
     FormalParameterType,
     optional;
 
@@ skipping 1660 matching lines @@
       continueTarget.resolveContinues(body);
     }
     Statement result = new DoStatement(body, condition);
     if (breakTarget.hasUsers) {
       result = new LabeledStatement(result);
       breakTarget.resolveBreaks(result);
     }
     exitLoopOrSwitch(result);
   }
 
+  void beginForInExpression(Token token) {
+    enterLocalScope(scope.parent);
+  }
+
+  void endForInExpression(Token token) {
+    debugEvent("ForInExpression");
+    Expression expression = popForValue();
+    exitLocalScope();
+    push(expression ?? NullValue.Expression);
+  }
+
   void endForIn(
       Token awaitToken, Token forToken, Token inKeyword, Token endToken) {
     debugEvent("ForIn");
     Statement body = popStatement();
     Expression expression = popForValue();
     var lvalue = pop();
     exitLocalScope();
     JumpTarget continueTarget = exitContinueTarget();
     JumpTarget breakTarget = exitBreakTarget();
     if (continueTarget.hasUsers) {
@@ skipping 814 matching lines @@
   } else if (node is TypeDeclarationBuilder) {
     return node.name;
   } else if (node is PrefixBuilder) {
     return node.name;
   } else if (node is ThisPropertyAccessor) {
     return node.name.name;
   } else {
     return internalError("Unhandled: ${node.runtimeType}");
   }
 }