Don't use regular expressions in Loader.

lib/yaml.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.
 
 library yaml;
 
 import 'src/loader.dart';
 import 'src/style.dart';
 import 'src/yaml_document.dart';
 import 'src/yaml_exception.dart';
@@ skipping 35 matching lines @@
 /// Loads a single document from a YAML string as a [YamlDocument].
 ///
 /// This is just like [loadYaml], except that where [loadYaml] would return a
 /// normal Dart value this returns a [YamlDocument] instead. This allows the
 /// caller to access document metadata.
 YamlDocument loadYamlDocument(String yaml, {sourceUrl}) {
   var loader = new Loader(yaml, sourceUrl: sourceUrl);
   var document = loader.load();
   if (document == null) {
     return new YamlDocument.internal(
-        new YamlScalar.internal(null, loader.span, ScalarStyle.ANY),
+        new YamlScalar.internalWithSpan(null, loader.span),
         loader.span, null, const []);
   }
 
   var nextDocument = loader.load();
   if (nextDocument != null) {
     throw new YamlException("Only expected one document.", nextDocument.span);
   }
 
   return document;
 }
@@ skipping 36 matching lines @@
 
   var documents = [];
   var document = loader.load();
   while (document != null) {
     documents.add(document);
     document = loader.load();
   }
 
   return documents;
 }