Add a type annotation to _identRegExp.

lib/src/path_observer.dart

 // Copyright (c) 2013, 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.
 
 library observe.src.path_observer;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:math' show min;
 
@@ skipping 310 matching lines @@
   }
 
   if (_logger.isLoggable(Level.FINER)) {
     _logger.finer("can't set $property in $object");
   }
   return false;
 }
 
 // From: https://github.com/rafaelw/ChangeSummary/blob/master/change_summary.js
 
-final _identRegExp = () {
+final RegExp _identRegExp = () {
   const identStart = '[\$_a-zA-Z]';
   const identPart = '[\$_a-zA-Z0-9]';
   return new RegExp('^$identStart+$identPart*\$');
 }();
 
 _isIdent(s) => _identRegExp.hasMatch(s);
 
 // Dart note: refactored to convert to codepoints once and operate on codepoints
 // rather than characters.
 class _PathParser {
@@ skipping 569 matching lines @@
       if (observer._isOpen) observer._iterateObjects(observe);
     }
 
     for (var observer in _observers.toList(growable: false)) {
       if (observer._isOpen) observer._check();
     }
   }
 }
 
 const int _MAX_DIRTY_CHECK_CYCLES = 1000;