anchor.diff:  
   class StatementBuilder extends GeneralizingAstVisitor<ast.Statement> {
     final ExpressionScope scope;
  -  final LabelStack breakStack, continueStack;
  +  LabelStack breakStack, continueStack;
   
     StatementBuilder(this.scope, [this.breakStack, this.continueStack]);
   
  
positive.code:       currentCase = null;
      }
      // Now that the label environment is set up, build the bodies.
      var innerBuilder = new StatementBuilder(scope, breakNode, continueNode);
      for (int i = 0; i < cases.length; ++i) {
        var blockNodes = <ast.Statement>[];
        for (var statement in bodies[i]) {
          innerBuilder.buildBlockMember(statement, blockNodes);
        }
        if (blockNodes.isEmpty || !isBreakingStatement(blockNodes.last)) {
          if (i < cases.length - 1) {
  
negative.code:     }
      var expression = scope.buildExpression(node.expression);
      var result = new ast.SwitchStatement(expression, cases);
      this.breakStack = oldBreak;
      this.continueStack = oldContinue;
      return makeBreakTarget(result, breakNode);
    }
  
  