Extend Iterable instead of implementing it.

sdk/lib/_internal/compiler/implementation/tree/nodes.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.
 
 part of tree;
 
 abstract class Visitor<R> {
   const Visitor();
 
   R visitNode(Node node);
@@ skipping 448 matching lines @@
     if (endToken != null) return endToken;
     if (nodes != null) {
       Link<Node> link = nodes;
       if (link.isEmpty) return beginToken;
       while (!link.tail.isEmpty) link = link.tail;
       if (link.head.getEndToken() != null) return link.head.getEndToken();
       if (link.head.getBeginToken() != null) return link.head.getBeginToken();
     }
     return beginToken;
   }
+
+  // ------------------- Iterable methods -------------------------------------
+  //
+  // TODO(floitsch): these functions should be pulled in through a mixin
+  // mechanism.
+  Collection mappedBy(f(Node element)) {
+    List result = [];
+    for (Node element in this) result.add(f(element));
+    return result;
+  }
+
+  Collection<Node> where(bool f(Node element)) {
+    List result = <Node>[];
+    for (Node element in this) if (f(element)) result.add(element);
+    return result;
+  }
+
+  bool contains(Node element) {
+    for (Node e in this) {
+      if (e == element) return true;
+    }
+    return false;
+  }
+
+  void forEach(void f(Node element)) {
+    for (Node element in this) f(element);
+  }
+
+  dynamic reduce(var initialValue,
+                 dynamic combine(var previousValue, Node element)) {
+    var value = initialValue;
+    for (Node element in this) value = combine(value, element);
+    return value;
+  }
+
+  bool every(bool f(Node element)) {
+    for (Node element in this) {
+      if (!f(element)) return false;
+    }
+    return true;
+  }
+
+  bool some(bool f(Node element)) {
+    for (Node element in this) {
+      if (f(element)) return true;
+    }
+    return false;
+  }
 }
 
 class Block extends Statement {
   final NodeList statements;
 
   Block(this.statements);
 
   Block asBlock() => this;
 
   accept(Visitor visitor) => visitor.visitBlock(this);
@@ skipping 1516 matching lines @@
  * argument).
  *
  * TODO(ahe): This method is controversial, the team needs to discuss
  * if top-level methods are acceptable and what naming conventions to
  * use.
  */
 initializerDo(Node node, f(Node node)) {
   SendSet send = node.asSendSet();
   if (send != null) return f(send.arguments.head);
 }