Add start/end to Uri.parse, allowing you to parse a substring without creating a new String object.

tests/corelib/uri_parse_test.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.
 
 import "package:expect/expect.dart";
 
 
 void testUriCombi() {
   var schemes = ["", "file", "ws", "ftp"];
   var fragments = ["", "#", "#f", "#fragment", "#l:?/"];
   var queries = ["", "?", "?q", "?query", "?q:/"];
-  var paths = ["/", "/x", "/x/y", "/x/y/", "/x:y"];
+  var paths = ["/", "/x", "/x/y", "/x/y/", "/x:y", "x", "x/y", "x/y/"];
   var userInfos = ["", "x", "xxx", "x:4", "xxx:444", "x:4:x"];
   var hosts = ["", "h", "hhh", "h:4", "hhh:444", "[::1.2.3.4]"];
 
   void check(uriString, scheme, fragment, query, path, user, host) {
-    var uri = Uri.parse(uriString);
-    Expect.equals(scheme, uri.scheme);
-    var uriFragment = uri.fragment;
-    if (fragment.startsWith('#')) uriFragment = "#$uriFragment";
-    Expect.equals(fragment, uriFragment);
-    var uriQuery = uri.query;
-    if (query.startsWith('?')) uriQuery = "?$uriQuery";
-    Expect.equals(query, uriQuery);
-    Expect.equals(path, uri.path);
-    Expect.equals(user, uri.userInfo);
-    var uriHost = uri.host;
-    if (host.startsWith("[")) uriHost = "[$uriHost]";
-    if (uri.port != 0) uriHost += ":${uri.port}";
-    Expect.equals(host, uriHost);
+    for (var uri in [Uri.parse(uriString),
+                     Uri.parse(">\u{10000}>$uriString<\u{10000}<",
+                               4, uriString.length + 4),
+                     Uri.parse("http://example.com/$uriString#?:/[]\"",
+                               19, uriString.length + 19),
+                     Uri.parse(uriString * 3,
+                               uriString.length, uriString.length * 2)]) {
+      String name = "$uriString -> $uri";
+      Expect.equals(scheme, uri.scheme, name);
+      var uriFragment = uri.fragment;
+      if (fragment.startsWith('#')) uriFragment = "#$uriFragment";
+      Expect.equals(fragment, uriFragment, name);
+      var uriQuery = uri.query;
+      if (query.startsWith('?')) uriQuery = "?$uriQuery";
+      Expect.equals(query, uriQuery, name);
+      Expect.equals(path, uri.path, name);
+      Expect.equals(user, uri.userInfo, name);
+      var uriHost = uri.host;
+      if (host.startsWith("[")) uriHost = "[$uriHost]";
+      if (uri.port != 0) uriHost += ":${uri.port}";
+      Expect.equals(host, uriHost, name);
+    }
   }
 
   for (var scheme in schemes) {
     for (var fragment in fragments) {
       for (var query in queries) {
         for (var path in paths) {
+          // File scheme URIs always get a leading slash.
+          if (scheme == "file" && !path.startsWith('/')) continue;
           for (var user in userInfos) {
             for (var host in hosts) {
               var auth = host;
               var s = scheme;
               if (user.isNotEmpty) auth = "$user@$auth";
               if (auth.isNotEmpty) auth = "//$auth";
+              if (auth.isNotEmpty && !path.startsWith('/')) continue;
               check("$scheme${scheme.isEmpty ? "" : ":"}"
                         "$auth$path$query$fragment",
                     scheme,
                     fragment,
                     query,
                     path,
                     user,
                     host);
             }
           }
         }
       }
     }
   }
 }
 
 void main() {
   testUriCombi();
 }