anchor.diff:  import 'package:analyzer/src/generated/variable_type_provider.dart';
   import 'package:front_end/src/fasta/flow_analysis/flow_analysis.dart';
   
  +class AnalyzerFunctionBodyAccess
  +    implements FunctionBodyAccess<VariableElement> {
  +  final FunctionBody node;
  +
  +  AnalyzerFunctionBodyAccess(this.node);
  +
  +  @override
  +  bool isPotentiallyMutatedInClosure(VariableElement variable) {
  +    return node.isPotentiallyMutatedInClosure(variable);
  +  }
  +
  +  @override
  +  bool isPotentiallyMutatedInScope(VariableElement variable) {
  +    return node.isPotentiallyMutatedInScope(variable);
  +  }
  +}
  +
  +class AnalyzerNodeOperations implements NodeOperations<Expression> {
  +  const AnalyzerNodeOperations();
  +
  +  @override
  +  Expression unwrapParenthesized(Expression node) {
  +    return node.unParenthesized;
  +  }
  +}
  +
   /// The helper for performing flow analysis during resolution.
   ///
   /// It contains related precomputed data, result, and non-trivial pieces of
  
positive.code:       flow = FlowAnalysis<Statement, Expression, VariableElement, DartType>(
          _nodeOperations,
          _typeOperations,
          _FunctionBodyAccess(node),
        );
      }
  
  
negative.code:   }
  }
  
  class _TypeSystemTypeOperations
      implements TypeOperations<VariableElement, DartType> {
    final TypeSystem typeSystem;
  