Require two type arguments for map literals (issue 4522).

utils/pub/yaml/composer.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.
 
 /**
  * Takes a parsed YAML document (what the spec calls the "serialization tree")
  * and resolves aliases, resolves tags, and parses scalars to produce the
  * "representation graph".
  */
 class _Composer extends _Visitor {
   /** The root node of the serialization tree. */
   _Node root;
 
   /**
    * Map from anchor names to the most recent representation graph node with
    * that anchor.
    */
   Map<String, _Node> anchors;
 
   /**
    * The next id to use for the represenation graph's anchors. The spec doesn't
    * use anchors in the representation graph, but we do so that the constructor
    * can ensure that the same node in the representation graph produces the same
    * native object.
    */
   int idCounter;
 
-  _Composer(this.root) : this.anchors = <_Node>{}, this.idCounter = 0;
+  _Composer(this.root) : this.anchors = <String, _Node>{}, this.idCounter = 0;
 
   /** Runs the Composer to produce a representation graph. */
   _Node compose() => root.visit(this);
 
   /** Returns the anchor to which an alias node refers. */
   _Node visitAlias(_AliasNode alias) {
     if (!anchors.containsKey(alias.anchor)) {
       throw new YamlException("no anchor for alias ${alias.anchor}");
     }
     return anchors[alias.anchor];
@@ skipping 133 matching lines @@
           value: Math.parseDouble("NaN"));
     }
 
     return null;
   }
 
   /** Parses a string scalar. */
   _ScalarNode parseString(String content) =>
     new _ScalarNode(_Tag.yaml("str"), value: content);
 }