Change IllegalArgumentException to ArgumentError.

pkg/unittest/string_matchers.dart

 // Copyright (c) 2012, 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 file.
 
 /**
  * Returns a matcher which matches if the match argument is a string and
  * is equal to [value] when compared case-insensitively.
  */
 Matcher equalsIgnoringCase(String value) => new _IsEqualIgnoringCase(value);
 
@@ skipping 153 matching lines @@
 
 class _MatchesRegExp extends _StringMatcher {
   RegExp _regexp;
 
   _MatchesRegExp(re) {
     if (re is String) {
       _regexp = new RegExp(re);
     } else if (re is RegExp) {
       _regexp = re;
     } else {
-      throw new IllegalArgumentException('matches requires a regexp or string');
+      throw new ArgumentError('matches requires a regexp or string');
     }
   }
 
   bool matches(String item, MatchState matchState) =>
         _regexp.hasMatch(item);
 
   Description describe(Description description) =>
       description.add("match '${_regexp.pattern}'");
 }
 
 // String matchers match against a string. We add this intermediate
 // class to give better mismatch error messages than the base Matcher class.
 /* abstract */ class _StringMatcher extends BaseMatcher {
   const _StringMatcher();
   Description describeMismatch(item, Description mismatchDescription,
                                MatchState matchState, bool verbose) {
     if (!(item is String)) {
       return mismatchDescription.
           addDescriptionOf(item).
           add(' not a string');
     } else {
       return super.describeMismatch(item, mismatchDescription,
           matchState, verbose);
     }
   }
 }