Fix busted type parameters in yaml.

pkg/yaml/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_maps/source_maps.dart';
 
 import 'null_span.dart';
 import 'yaml_node.dart';
 
 /// A wrapper that makes a normal Dart map behave like a [YamlMap].
 class YamlMapWrapper extends MapBase
-    with pkg_collection.UnmodifiableMapMixin<dynamic, YamlNode>
+    with pkg_collection.UnmodifiableMapMixin
     implements YamlMap {
   final Map _dartMap;
 
   final Span span;
 
   final Map<dynamic, YamlNode> nodes;
 
   Map get value => this;
 
   Iterable get keys => _dartMap.keys;
@@ skipping 26 matching lines @@
   final Map _dartMap;
 
   final Span _span;
 
   Iterable get keys =>
       _dartMap.keys.map((key) => new YamlScalar.internal(key, _span));
 
   _YamlMapNodes(this._dartMap, this._span);
 
   YamlNode operator [](Object key) {
-    if (key is YamlScalar) key = key.value;
+    // Use "as" here because key being assigned to invalidates local type
+    // inference.

[Bob Nystrom, 2014/06/24 20:03:49]

"local type inference" -> "type propagation"

[nweiz, 2014/06/24 20:04:45]

Done.

+    if (key is YamlScalar) key = (key as YamlScalar).value;
     if (!_dartMap.containsKey(key)) return null;
     return _nodeForValue(_dartMap[key], _span);
   }
 
   int get hashCode => _dartMap.hashCode;
 
   operator ==(Object other) =>
       other is _YamlMapNodes && other._dartMap == _dartMap;
 }
 
@@ skipping 65 matching lines @@
 
   operator ==(Object other) =>
       other is _YamlListNodes && other._dartList == _dartList;
 }
 
 YamlNode _nodeForValue(value, Span 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);
 }