anchor.diff:  import 'package:front_end/src/fasta/kernel/kernel_builder.dart';
   import "package:front_end/src/fasta/kernel/kernel_target.dart";
   import 'package:front_end/src/fasta/modifier.dart' as Modifier;
  +import 'package:front_end/src/fasta/parser/async_modifier.dart';
   import 'package:front_end/src/fasta/parser/parser.dart';
   import 'package:front_end/src/fasta/scanner.dart';
   import 'package:front_end/src/fasta/ticker.dart';
  
positive.code:   }
  
    T _parse<T>(
        String source, void parseFunction(Parser parser, Token previousToken)) {
      ScannerResult scan = scanString(source);
  
      return CompilerContext.runWithOptions(options, (CompilerContext c) {
  
negative.code: import '../../generated/parser_test.dart';
  import '../../generated/test_support.dart';
  
  /// Implementation of [AbstractParserTestCase] specialized for testing building
  /// Analyzer AST using the fasta [Forest] API.
  class FastaBodyBuilderTestCase extends Object
      with ParserTestHelpers
      implements AbstractParserTestCase {
  