anchor.diff:        : super(fileSystem, platformKernel, strongMode: strongMode);
   
     @override
  -  Future<Program> compile(Uri script) async {
  +  Future<Program> compileInternal(Uri script) async {
       if (generator == null) {
         generator = await IncrementalKernelGenerator.newInstance(options, script);
       }
  
positive.code:       : super(fileSystem, platformKernel, strongMode: strongMode);
  
    @override
    Future<Program> compile(Uri script) async {
      return requireMain
          ? kernelForProgram(script, options)
          : kernelForBuildUnit([script], options..chaseDependencies = true);
  
negative.code: ///
  library runtime.tools.kernel_service;
  
  import 'dart:async' show Future, ZoneSpecification, runZoned;
  import 'dart:io' show Platform, stderr hide FileSystemEntity;
  import 'dart:isolate';
  import 'dart:typed_data' show Uint8List;
  
  