Add related types check to analyze_dart2js_test

pkg/js_ast/lib/src/printer.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 js_ast;
 
 
 typedef String Renamer(Name);
 
 class JavaScriptPrintingOptions {
@@ skipping 118 matching lines @@
   }
 
   void spaceOut() {
     if (!shouldCompressOutput) out(" ", isWhitespace: true);
   }
 
   String lastAddedString = null;
 
   int get lastCharCode {
     if (lastAddedString == null) return 0;
-    assert(lastAddedString.length != "");
+    assert(lastAddedString.length != 0);
     return lastAddedString.codeUnitAt(lastAddedString.length - 1);
   }
 
   void out(String str, {bool isWhitespace: false}) {
     if (str != "") {
       if (pendingSemicolon) {
         if (!shouldCompressOutput) {
           _emit(";");
         } else if (str != "}") {
           // We want to output newline instead of semicolon because it makes
@@ skipping 1331 matching lines @@
     }
   }
 
   EnterExitNode exitNode(JavaScriptPrintingContext context, int position) {
     // Enter must happen before exit.
     addToNode(context, position);
     context.exitNode(node, startPosition, position, closingPosition);
     return parent;
   }
 }