Make string juxtaposition combine properly with string interpolations.

frog/leg/tree/unparser.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 Unparser implements Visitor {
   StringBuffer sb;
   final bool printDebugInfo;
 
   Unparser([this.printDebugInfo = false]);
 
@@ skipping 101 matching lines @@
   }
 
   visitLiteralInt(LiteralInt node) {
     add(node.token.value);
   }
 
   visitLiteralString(LiteralString node) {
     add(node.token.value);
   }
 
-  visitLiteralStringJuxtaposition(LiteralStringJuxtaposition node) {
-    for (Link<Expression> literals = node.literals;
-         !literals.isEmpty();
-         literals = literals.tail) {
-      visit(literals.head);
-      if (!literals.tail.isEmpty()) {
-        sb.add(" ");
-      }
-    }
+  visitStringJuxtaposition(LiteralStringJuxtaposition node) {
+    visit(node.first);
+    sb.add(" ");
+    visit(node.second);
   }
 
   visitLiteralNull(LiteralNull node) {
     add(node.token.value);
   }
 
   visitNewExpression(NewExpression node) {
     add(node.newToken.value);
     sb.add(' ');
     visit(node.send);
@@ skipping 246 matching lines @@
       sb.add(' ');
     }
     visit(node.name);
     if (node.typeParameters !== null) {
       visit(node.typeParameters);
     }
     visit(node.formals);
     add(node.endToken.value);
   }
 }