Don't use regular expressions in Loader.

lib/src/yaml_node_wrapper.dart

 // Copyright (c) 2014, 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 yaml.yaml_node_wrapper;
 
 import 'dart:collection';
 
 import 'package:collection/collection.dart' as pkg_collection;
 import 'package:source_span/source_span.dart';
@@ skipping 41 matching lines @@
 
 /// The implementation of [YamlMapWrapper.nodes] as a wrapper around the Dart
 /// map.
 class _YamlMapNodes extends MapBase<dynamic, YamlNode>
     with pkg_collection.UnmodifiableMapMixin<dynamic, YamlNode> {
   final Map _dartMap;
 
   final SourceSpan _span;
 
   Iterable get keys => _dartMap.keys.map((key) =>
-      new YamlScalar.internal(key, _span, ScalarStyle.ANY));
+      new YamlScalar.internalWithSpan(key, _span));
 
   _YamlMapNodes(this._dartMap, this._span);
 
   YamlNode operator [](Object key) {
     // Use "as" here because key being assigned to invalidates type propagation.
     if (key is YamlScalar) key = (key as YamlScalar).value;
     if (!_dartMap.containsKey(key)) return null;
     return _nodeForValue(_dartMap[key], _span);
   }
 
@@ skipping 71 matching lines @@
 
   int get hashCode => _dartList.hashCode;
 
   operator ==(Object other) =>
       other is _YamlListNodes && other._dartList == _dartList;
 }
 
 YamlNode _nodeForValue(value, SourceSpan span) {
   if (value is Map) return new YamlMapWrapper._(value, span);
   if (value is List) return new YamlListWrapper._(value, span);
-  return new YamlScalar.internal(value, span, ScalarStyle.ANY);
+  return new YamlScalar.internalWithSpan(value, span);
 }