anchor.diff:  class FlowAnalysisDebug<Node extends Object, Statement extends Node,
           Expression extends Object, Variable extends Object, Type extends Object>
       implements FlowAnalysis<Node, Statement, Expression, Variable, Type> {
  -  _FlowAnalysisImpl<Node, Statement, Expression, Variable, Type> _wrapped;
  +  FlowAnalysis<Node, Statement, Expression, Variable, Type> _wrapped;
   
     bool _exceptionOccurred = false;
   
  
positive.code:     _wrap('write($variable, $writtenType, $writtenExpression)',
          () => _wrapped.write(variable, writtenType, writtenExpression));
    }
  
    T _wrap<T>(String description, T callback(),
        {bool isQuery: false, bool? isPure}) {
  
negative.code:         _current.write(variable, writtenType, newSsaNode, typeOperations);
    }
  
    @override
    void _dumpState() {
      print('  current: $_current');
      print('  expressionWithInfo: $_expressionWithInfo');
  