anchor.diff:      String incrementalCompilerByteStorePath,
       String packagesPath,
       List<String> fileSystemRoots,
  -    String fileSystemScheme}) async {
  +    String fileSystemScheme,
  +  }) async {
       final String frontendServer = artifacts.getArtifactPath(
         Artifact.frontendServerSnapshotForEngineDartSdk
       );
  
positive.code: typedef void CompilerMessageConsumer(String message);
  
  class CompilerOutput {
    String outputFilename;
    int errorCount;
  
    CompilerOutput(this.outputFilename, this.errorCount);
  }
  
  class _StdoutHandler {
  
negative.code: class KernelCompiler {
    const KernelCompiler();
  
    Future<CompilerOutput> compile({
      String sdkRoot,
      String mainPath,
      String outputFilePath,
      String depFilePath,
  