Implement string interpolation up to SSA.

dart/frog/leg/resolver.dart

 // Copyright (c) 2011, 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.
 
 class TreeElements {
   Map<Node, Element> map;
   TreeElements() : map = new LinkedHashMap<Node, Element>();
   operator []=(Node node, Element element) => map[node] = element;
   operator [](Node node) => map[node];
 }
@@ skipping 420 matching lines @@
     cancel(node, "Unimplemented");
   }
 
   visitLiteralList(LiteralList node) {
     visit(node.elements);
   }
 
   visitConditional(Conditional node) {
     node.visitChildren(this);
   }
+
+  visitStringInterpolation(StringInterpolation node) {
+    node.visitChildren(this);
+  }
+
+  visitStringInterpolationPart(StringInterpolationPart node) {
+    node.visitChildren(this);
+  }
 }
 
 class ClassResolverVisitor extends AbstractVisitor<Type> {
   Compiler compiler;
   Scope context;
 
   ClassResolverVisitor(Compiler compiler)
     : this.compiler = compiler, context = new TopScope(compiler.universe);
 
   Type visitClassNode(ClassNode node) {
@@ skipping 153 matching lines @@
 class TopScope extends Scope {
   Universe universe;
 
   TopScope(Universe this.universe) : super(null, null);
   Element lookup(SourceString name) => universe.find(name);
 
   Element add(Element element) {
     throw "Cannot add an element in the top scope";
   }
 }