anchor.diff:          FunctionReferenceResolver(this, _isNonNullableByDefault);
     }
   
  +  /// Return the element representing the function containing the current node,
  +  /// or `null` if the current node is not contained in a function.
  +  ///
  +  /// @return the element representing the function containing the current node
  +  ExecutableElement? get enclosingFunction => _enclosingFunction;
  +
     bool get isConstructorTearoffsEnabled =>
         _featureSet.isEnabled(Feature.constructor_tearoffs);
   
  
positive.code: 
    @override
    void visitExtensionDeclaration(ExtensionDeclaration node) {
      try {
        super.visitExtensionDeclaration(node);
        node.accept(elementResolver);
        node.accept(typeAnalyzer);
      } finally {
        _thisType = null;
      }
    }
  
negative.code:       super.visitFunctionExpression(node);
      } finally {
        nameScope = outerScope;
      }
    }
  
  