Rollback instrumentation during analysis and validate resolved ASTs instead.

pkg/front_end/lib/src/fasta/testing/validating_instrumentation.dart

 // Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:front_end/src/base/instrumentation.dart';
 import 'package:front_end/src/fasta/messages.dart';
 import 'package:front_end/src/fasta/scanner.dart';
 import 'package:front_end/src/fasta/scanner/io.dart';
 
 /// Implementation of [Instrumentation] which checks property/value pairs
 /// against expectations encoded in source files using "/*@...*/" comments.
 class ValidatingInstrumentation implements Instrumentation {
   static final _ESCAPE_SEQUENCE = new RegExp(r'\\(.)');
 
   /// Map from feature names to the property names they are short for.
   static const _FEATURES = const {
     'inference': const [
       'topType',
       'typeArg',
+      'typeArgs',
       'promotedType',
       'type',
       'returnType'
     ],
   };
 
   /// Map from file URI to the as-yet unsatisfied expectations from that file,
   /// organized by file offset.
   final _unsatisfiedExpectations = <Uri, Map<int, List<_Expectation>>>{};
 
@@ skipping 187 matching lines @@
       this.property, this.value, this.commentOffset, this.commentLength);
 }
 
 class _Fix {
   final int offset;
   final int length;
   final String replacement;
 
   _Fix(this.offset, this.length, this.replacement);
 }