anchor.diff:  
     @override
     Local getLocalVariable(ir.VariableDeclaration node) {
  -    return _variableMap.putIfAbsent(node, () {
  -      JLocal local = new JLocal(node.name, currentMember,
  +    final variableMap = _variableMap ??= {};
  +    return variableMap.putIfAbsent(node, () {
  +      JLocal local = JLocal(node.name, currentMember,
             isRegularParameter: node.parent is ir.FunctionNode);
  -      _locals.register<JLocal, LocalData>(local, new LocalData(node));
  +      _locals.register<JLocal, LocalData>(local, LocalData(node));
         return local;
       });
     }
  
positive.code:       }
      }
      _breaksAsContinue = source.readTreeNodes();
      source.end(tag);
    }
  
  
negative.code:   int jumpIndex = 0;
    int labelIndex = 0;
    final MemberEntity member;
    final Map<ir.TreeNode, JJumpTarget> jumpTargetMap = {};
    final Set<ir.BreakStatement> breaksAsContinue = {};
  
    JumpVisitor(this.member);
  
  