Add new constructors to YamlNode subclasses.

pkg/yaml/lib/src/constructor.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.constructor;
 
 import 'equality.dart';
 import 'model.dart';
 import 'visitor.dart';
 import 'yaml_node.dart';
 
 /// Takes a parsed and composed YAML document (what the spec calls the
 /// "representation graph") and creates native Dart objects that represent that
 /// document.
 class Constructor extends Visitor {
   /// The root node of the representation graph.
   final Node _root;
 
   /// Map from anchor names to the most recent Dart node with that anchor.
   final _anchors = <String, YamlNode>{};
 
   Constructor(this._root);
 
   /// Runs the Constructor to produce a Dart object.
   YamlNode construct() => _root.visit(this);
 
   /// Returns the value of a scalar.
   YamlScalar visitScalar(ScalarNode scalar) =>
-      new YamlScalar(scalar.value, scalar.span);
+      new YamlScalar.internal(scalar.value, scalar.span);
 
   /// Converts a sequence into a List of Dart objects.
   YamlList visitSequence(SequenceNode seq) {
     var anchor = getAnchor(seq);
     if (anchor != null) return anchor;
     var nodes = [];
-    var dartSeq = setAnchor(seq, new YamlList(nodes, seq.span));
+    var dartSeq = setAnchor(seq, new YamlList.internal(nodes, seq.span));
     nodes.addAll(super.visitSequence(seq));
     return dartSeq;
   }
 
   /// Converts a mapping into a [Map] of Dart objects.
   YamlMap visitMapping(MappingNode map) {
     var anchor = getAnchor(map);
     if (anchor != null) return anchor;
     var nodes = deepEqualsMap();
-    var dartMap = setAnchor(map, new YamlMap(nodes, map.span));
+    var dartMap = setAnchor(map, new YamlMap.internal(nodes, map.span));
     super.visitMapping(map).forEach((k, v) => nodes[k] = v);
     return dartMap;
   }
 
   /// Returns a new Dart object wrapping the object that already represents
   /// [anchored], if such a thing exists.
   YamlNode getAnchor(Node anchored) {
     if (anchored.anchor == null) return null;
     var value = _anchors[anchored.anchor];
     if (value == null) return null;
 
     // Re-wrap [value]'s contents so that it's associated with the span of the
     // anchor rather than its original definition.
-    if (value is YamlMap) return new YamlMap(value.nodes, anchored.span);
-    if (value is YamlList) return new YamlList(value.nodes, anchored.span);
-    assert(value is YamlScalar);
-    return new YamlScalar(value.value, anchored.span);
+    if (value is YamlMap) {
+      return new YamlMap.internal(value.nodes, anchored.span);
+    } else if (value is YamlList) {
+      return new YamlList.internal(value.nodes, anchored.span);
+    } else {
+      assert(value is YamlScalar);
+      return new YamlScalar.internal(value.value, anchored.span);
+    }
   }
 
   /// Records that [value] is the Dart object representing [anchored].
   YamlNode setAnchor(Node anchored, YamlNode value) {
     if (anchored.anchor == null) return value;
     _anchors[anchored.anchor] = value;
     return value;
   }
 }