Steps towards making dart2js JS AST templates an indepentent library.

pkg/compiler/lib/src/js/template.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.
 
 part of js;
 
 class TemplateManager {
   Map<String, Template> expressionTemplates = new Map<String, Template>();
   Map<String, Template> statementTemplates = new Map<String, Template>();
 
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   Instantiator visitAwait(Await node) {
     Instantiator makeExpression = visit(node.expression);
     return (arguments) {
       return new Await(makeExpression(arguments));
     };
   }
 }
 
 /**
- * InterpolatedNodeAnalysis extract [InterpolatedNode]s from AST.
+ * InterpolatedNodeAnalysis determines which AST trees contain
+ * [InterpolatedNode]s, and the names of the named interpolated nodes.
  */
 class InterpolatedNodeAnalysis extends BaseVisitor {
-  final Setlet<Node> containsInterpolatedNode = new Setlet<Node>();
-  final List<InterpolatedNode> interpolatedNodes = <InterpolatedNode>[];
-  final Setlet<String> holeNames = new Setlet<String>();
+  final Set<Node> containsInterpolatedNode = new Set<Node>();
+  final Set<String> holeNames = new Set<String>();
   int count = 0;
 
   InterpolatedNodeAnalysis();
 
   bool containsInterpolatedNodes(Node node) =>
       containsInterpolatedNode.contains(node);
 
   void visit(Node node) {
     node.accept(this);
   }
 
   void visitNode(Node node) {
     int before = count;
     node.visitChildren(this);
     if (count != before) containsInterpolatedNode.add(node);
     return null;
   }
 
   visitInterpolatedNode(InterpolatedNode node) {
-    interpolatedNodes.add(node);
     containsInterpolatedNode.add(node);
     if (node.isNamed) holeNames.add(node.nameOrPosition);
     ++count;
   }
 }