Create a "PackageRef" class that defines a versionless package reference.

sdk/lib/_internal/pub/test/version_solver_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.
 
 library pub_update_test;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:unittest/unittest.dart';
@@ skipping 922 matching lines @@
     _packages.putIfAbsent(description, () => new Map<Version, Package>());
     _packages[description][package.version] = package;
   }
 }
 
 Package mockPackage(String description, String version,
                     Map dependencyStrings) {
   var sdkConstraint = null;
 
   // Build the pubspec dependencies.
-  var dependencies = <PackageRef>[];
-  var devDependencies = <PackageRef>[];
+  var dependencies = <PackageDep>[];
+  var devDependencies = <PackageDep>[];
 
   dependencyStrings.forEach((name, constraint) {
     parseSource(name, (isDev, name, source) {
       var packageName = name.replaceFirst(new RegExp(r"-[^-]+$"), "");
       constraint = new VersionConstraint.parse(constraint);
 
       if (name == 'sdk') {
         sdkConstraint = constraint;
         return;
       }
 
-      var ref = new PackageRef(packageName, source, constraint, name);
+      var dep = new PackageDep(packageName, source, constraint, name);
 
       if (isDev) {
-        devDependencies.add(ref);
+        devDependencies.add(dep);
       } else {
-        dependencies.add(ref);
+        dependencies.add(dep);
       }
     });
   });
 
   var name = description.replaceFirst(new RegExp(r"-[^-]+$"), "");
   var pubspec = new Pubspec(
       name, new Version.parse(version), dependencies, devDependencies,
       new PubspecEnvironment(sdkConstraint));
   return new Package.inMemory(pubspec);
 }
@@ skipping 17 matching lines @@
   };
 
   var match = new RegExp(r"(.*) from (.*)").firstMatch(description);
   if (match != null) {
     name = match[1];
     source = sourceNames[match[2]];
   }
 
   callback(isDev, name, source);
 }