Specialize instance calls when the call receiver is the method receiver and the method class has a …

runtime/lib/string_patch.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.
 
 const int _maxAscii = 0x7f;
 const int _maxLatin1 = 0xff;
 const int _maxUtf16 = 0xffff;
 const int _maxUnicode = 0x10ffff;
 
 patch class String {
@@ skipping 29 matching lines @@
   /* patch */ const factory String.fromEnvironment(String name,
                                                    {String defaultValue})
       native "String_fromEnvironment";
 }
 
 
 /**
  * [_StringBase] contains common methods used by concrete String
  * implementations, e.g., _OneByteString.
  */
-class _StringBase {
+abstract class _StringBase {
   // Constants used by replaceAll encoding of string slices between matches.
   // A string slice (start+length) is encoded in a single Smi to save memory
   // overhead in the common case.
   // We use fewer bits for length (11 bits) than for the start index (19+ bits).
   // For long strings, it's possible to have many large indices,
   // but it's unlikely to have many long lengths since slices don't overlap.
   // If there are few matches in a long string, then there are few long slices,
   // and if there are many matches, there'll likely be many short slices.
   //
   // Encoding is: 0((start << _lengthBits) | length)
@@ skipping 1290 matching lines @@
     int end = index + _pattern.length;
     _current = new _StringMatch(index, _input, _pattern);
     // Empty match, don't start at same location again.
     if (end == _index) end++;
     _index = end;
     return true;
   }
 
   Match get current => _current;
 }