anchor.diff:  
     @override
     AwaitExpression parseAwaitExpression(String code) {
  -    return parseExpression(code);
  +    return parseExpression(code, inAsync: true);
     }
   
     @override
  
positive.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 {
  
negative.code: 
    FastaBodyBuilderTestCase(this.resolveTypes);
  
    analyzer.Parser get parser => new ParserProxy(this);
  
    TypeProvider get typeProvider => _typeProvider;
  
    @override
  