Handling of wrong types of arguments in the File API.

runtime/lib/string.dart

 // Copyright (c) 2011, 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.
 
 /**
  * [StringBase] contains common methods used by concrete String implementations,
  * e.g., OneByteString.
  */
 class StringBase {
 
@@ skipping 162 matching lines @@
     }
     int last = len - 1;
     for (int i = last; last >= first; last--) {
       if (!_isWhitespace(this.charCodeAt(last))) {
         break;
       }
     }
     return substringUnchecked_(first, last + 1);
   }
 
-  bool contains(Pattern other, int startIndex) {
+  bool contains(Pattern other, [int startIndex = 0]) {
     if (other is String) {
       return indexOf(other, startIndex) >= 0;
     }
     return other.allMatches(this.substring(startIndex)).iterator().hasNext();
   }
 
   String replaceFirst(Pattern from, String to) {
     if (from is RegExp) {
       throw "Unimplemented String.replace with RegExp";
     }
@@ skipping 242 matching lines @@
     for (int g in groups) {
       result.add(group(g));
     }
     return result;
   }
 
   final int _start;
   final String str;
   final String pattern;
 }