Two different classes may have the same *name*.

dart/utils/uri/uri.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.
 
 #library('uri');
 
 /**
  * A parsed URI, inspired by:
  * http://closure-library.googlecode.com/svn/docs/class_goog_Uri.html
  */
@@ skipping 151 matching lines @@
   bool hasAuthority() {
     return (userInfo != "") || (domain != "") || (port != 0);
   }
 
   String toString() {
     StringBuffer sb = new StringBuffer();
     _addIfNonEmpty(sb, scheme, scheme, ':');
     if (hasAuthority() || (scheme == "file")) {
       sb.add("//");
       _addIfNonEmpty(sb, userInfo, userInfo, "@");
-      sb.add(domain);
+      sb.add(domain === null ? "null" : domain);
       if (port != 0) {
         sb.add(":");
         sb.add(port.toString());
       }
     }
-    sb.add(path);
+    sb.add(path === null ? "null" : path);
     _addIfNonEmpty(sb, query, "?", query);
     _addIfNonEmpty(sb, fragment, "#", fragment);
     return sb.toString();
   }
 
   static void _addIfNonEmpty(StringBuffer sb, String test,
                              String first, String second) {
     if ("" != test) {
-      sb.add(first);
-      sb.add(second);
+      sb.add(first === null ? "null" : first);
+      sb.add(second === null ? "null" : second);
     }
   }
 }
 
 String merge(String base, String reference) {
   if (base == "") return "/$reference";
   return base.substring(0, base.lastIndexOf("/") + 1) + "$reference";
 }
 
 String removeDotSegments(String path) {
   List<String> output = [];
   bool appendSlash = false;
   for (String segment in path.split("/")) {
     appendSlash = false;
     if (segment == "..") {
       if (!output.isEmpty() &&
           ((output.length != 1) || (output[0] != ""))) output.removeLast();
       appendSlash = true;
     } else if ("." == segment) {
       appendSlash = true;
     } else {
       output.add(segment);
     }
   }
   if (appendSlash) output.add("");
   return Strings.join(output, "/");
 }