anchor.diff:    const ThrowsMatcher([Matcher matcher]) : _matcher = matcher, super(matcher);
   
     Description describeMismatch(item, Description mismatchDescription,
  -                               MatchState matchState,
  +                               Map matchState,
                                  bool verbose) {
       if (item is! Function && item is! Future) {
         return mismatchDescription.add(' not a Function or Future');
       }
   
  -    if (_matcher == null ||  matchState.state == null) {
  +    if (_matcher == null ||  matchState == null) {
         return mismatchDescription.add(' did not throw any exception');
       }
   
  
positive.code: library unittest;
  
  import 'package:unittest/unittest.dart';
  import '../lib/mirrors.dart';
  import 'dart:async';
  
  export 'package:unittest/unittest.dart';
  
negative.code:     messageMatcher.describe(description);
    }
  
    Description describeMismatch(item, Description mismatchDescription, Map matchState,
                                 bool verbose) {
      var e = matchState['exception'];
  
      mismatchDescription.add('threw ').addDescriptionOf(e);
  
  