Create associated packages for the dart:collection and dart:async libs.

sdk/lib/_internal/pub/lib/src/version.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.
 
 /// Handles version numbers, following the [Semantic Versioning][semver] spec.
 ///
 /// [semver]: http://semver.org/
 library pub.version;
 
 import 'dart:math';
 
-import 'package:collection_helpers/equality.dart';
+import 'package:collection/equality.dart';
 
 /// Regex that matches a version number at the beginning of a string.
 final _START_VERSION = new RegExp(
     r'^'                                        // Start at beginning.
     r'(\d+).(\d+).(\d+)'                        // Version number.
     r'(-([0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*))?'    // Pre-release.
     r'(\+([0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*))?'); // Build.
 
 /// Like [_START_VERSION] but matches the entire string.
 final _COMPLETE_VERSION = new RegExp("${_START_VERSION.pattern}\$");
@@ skipping 501 matching lines @@
 
 class _EmptyVersion implements VersionConstraint {
   const _EmptyVersion();
 
   bool get isEmpty => true;
   bool get isAny => false;
   bool allows(Version other) => false;
   VersionConstraint intersect(VersionConstraint other) => this;
   String toString() => '<empty>';
 }