Make RegExp's constructor non-const.

utils/pub/yaml/model.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.
 
 // This file contains the node classes for the internal representations of YAML
 // documents. These nodes are used for both the serialization tree and the
 // representation graph.
 
 /** A tag that indicates the type of a YAML node. */
 class _Tag {
@@ skipping 128 matching lines @@
    * Returns the canonical serialization of the value of the scalar. If the
    * value isn't given, the result of this will be "null".
    */
   String get canonicalContent {
     if (value == null || value is bool || value is int) return '$value';
 
     if (value is num) {
       // 20 is the maximum value for this argument, which we use since YAML
       // doesn't specify a maximum.
       return value.toStringAsExponential(20).
-        replaceFirst(const RegExp("0+e"), "e");
+        replaceFirst(new RegExp("0+e"), "e");
     }
 
     if (value is String) {
       // TODO(nweiz): This could be faster if we used a RegExp to check for
       // special characters and short-circuited if they didn't exist.
 
       var escapedValue = value.charCodes.map((c) {
         switch (c) {
         case _Parser.TAB: return "\\t";
         case _Parser.LF: return "\\n";
@@ skipping 69 matching lines @@
   String toString() {
     var strContent = Strings.join(content.keys.
         map((k) => '${k}: ${content[k]}'), ', ');
     return '$tag {$strContent}';
   }
 
   int get hashCode => super.hashCode ^ _hashCode(content);
 
   visit(_Visitor v) => v.visitMapping(this);
 }