Use pub_semver package in pub.

sdk/lib/_internal/pub_generated/lib/src/cached_package.dart

 library pub.cached_package;
 import 'package:path/path.dart' as p;
+import 'package:pub_semver/pub_semver.dart';
 import 'package:yaml/yaml.dart';
 import 'barback/transformer_config.dart';
 import 'io.dart';
 import 'package.dart';
 import 'pubspec.dart';
-import 'version.dart';
 class CachedPackage extends Package {
   final String _cacheDir;
   CachedPackage(Package inner, this._cacheDir)
       : super(new _CachedPubspec(inner.pubspec), inner.dir);
   String path(String part1, [String part2, String part3, String part4,
       String part5, String part6, String part7]) {
     if (_pathInCache(part1)) {
       return p.join(_cacheDir, part1, part2, part3, part4, part5, part6, part7);
     } else {
       return super.path(part1, part2, part3, part4, part5, part6, part7);
@@ skipping 26 matching lines @@
   List<PackageDep> get dependencyOverrides => _inner.dependencyOverrides;
   PubspecEnvironment get environment => _inner.environment;
   String get publishTo => _inner.publishTo;
   Map<String, String> get executables => _inner.executables;
   bool get isPrivate => _inner.isPrivate;
   bool get isEmpty => _inner.isEmpty;
   List<PubspecException> get allErrors => _inner.allErrors;
   List<Set<TransformerConfig>> get transformers => const [];
   _CachedPubspec(this._inner);
 }