anchor.diff:    @override
     get session => mixin.session;
   
  +  @override
  +  get source => mixin.source;
  +
  +  @override
  +  get nameOffset => -1;
  +
     /// Returns true iff this class was declared using the syntax
     /// `class B = A with M;`, i.e., if it is an explicitly named mixin
     /// application.
  
positive.code:   // we will never need to support any members that we don't use locally.
    @override
    noSuchMethod(Invocation invocation) {
      _severe("Missing MixinApplication member");
    }
  }
  
  
negative.code:     final resolvedLibrary =
          await target.session.getResolvedLibraryByElement(target.library);
      final targetDeclaration = resolvedLibrary.getElementDeclaration(target);
      final unit = targetDeclaration.resolvedUnit.unit;
      final location = unit.lineInfo?.getLocation(nameOffset);
      if (location != null) {
        locationString = "${location.lineNumber}:${location.columnNumber}";
  