anchor.diff:            'used, and where dill filesize does not matter, and the gain is '
             'improved speed.',
         defaultsTo: false,
  +      hide: true)
  +  ..addMultiOption('enable-experiment',
  +      help: 'Comma separated list of experimental features, eg set-literals.',
         hide: true);
   
   String usage = '''
  
positive.code: // that would replace api used below. This api was made private in
  // an effort to discourage further use.
  // ignore_for_file: implementation_imports
  import 'package:front_end/src/api_unstable/vm.dart';
  import 'package:kernel/ast.dart';
  import 'package:kernel/binary/ast_to_binary.dart';
  
negative.code:       ..sdkSummary = sdkRoot.resolve(platformKernelDill)
        ..verbose = options['verbose']
        ..embedSourceText = options['embed-source-text']
        ..experimentalFlags = parseExperimentalFlags(
            options['enable-experiment'], (msg) => errors.add(msg))
        ..onDiagnostic = (DiagnosticMessage message) {
          bool printMessage;
          switch (message.severity) {
  