anchor.diff:        NodeChangeForMethodInvocation();
   
     @override
  -  NodeChange visitCompilationUnit(CompilationUnit node) =>
  -      NodeChangeForCompilationUnit();
  -
  -  @override
     NodeChange visitNode(AstNode node) =>
         throw StateError('Unexpected node type: ${node.runtimeType}');
   
  
positive.code:   }
  }
  
  /// Implementation of [NodeChange] specialized for operating on
  /// [CompilationUnit] nodes.
  class NodeChangeForCompilationUnit extends NodeChange<CompilationUnit> {
    NodeChangeForCompilationUnit() : super._();
  
    bool removeLanguageVersionComment = false;
  
    @override
    EditPlan _apply(CompilationUnit node, FixAggregator aggregator) {
  
negative.code:     }
      innerPlans.addAll(aggregator.innerPlansForNode(node));
      return aggregator.planner.passThrough(node, innerPlans: innerPlans);
    }
  }
  
  