anchor.diff:  import 'dart:convert' show json;
   import 'dart:io';
   import 'package:args/args.dart' show ArgParser;
  +import 'package:build_integration/file_system/multi_root.dart';
   import 'package:dev_compiler/src/compiler/module_builder.dart';
   import 'package:dev_compiler/src/compiler/shared_command.dart'
       show SharedCompilerOptions;
  
positive.code: import 'package:front_end/src/api_unstable/ddc.dart'
      show
          CompilerOptions,
          kernelForModule,
          DiagnosticMessage,
          printDiagnosticMessage,
          Severity;
  import 'package:kernel/kernel.dart';
  import 'package:kernel/target/targets.dart';
  import 'package:path/path.dart' as p;
  
negative.code:     var mapPath = '$jsPath.map';
      await Directory(jsDir).create();
      var jsCode = jsProgramToCode(jsModule, format,
          jsUrl: jsPath,
          mapUrl: mapPath,
          buildSourceMap: true,
          customScheme: customScheme);
      await File(jsPath).writeAsString(jsCode.code);
      await File(mapPath).writeAsString(json.encode(jsCode.sourceMap));
    }
  