Make Comparable generic.

utils/pub/package.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 package;
 
 import 'dart:async';
 
 import '../../pkg/path/lib/path.dart' as path;
 
@@ skipping 67 matching lines @@
   String toString() => '$name $version ($dir)';
 }
 
 /// An unambiguous resolved reference to a package. A package ID contains enough
 /// information to correctly install the package.
 ///
 /// Note that it's possible for multiple distinct package IDs to point to
 /// different directories that happen to contain identical packages. For
 /// example, the same package may be available from multiple sources. As far as
 /// Pub is concerned, those packages are different.
-class PackageId implements Comparable {
+class PackageId implements Comparable<PackageId> {
   /// The name of the package being identified.
   final String name;
 
   /// The [Source] used to look up this package given its [description]. If
   /// this is a root package ID, this will be `null`.
   final Source source;
 
   /// The package's version.
   final Version version;
 
@@ skipping 23 matching lines @@
            other.source == source &&
            other.version == version;
   }
 
   String toString() {
     if (isRoot) return "$name $version (root)";
     if (source.isDefault) return "$name $version";
     return "$name $version from $source";
   }
 
-  int compareTo(Comparable other) {
-    if (other is! PackageId) throw new ArgumentError(other);
-
+  int compareTo(PackageId other) {
     var sourceComp = source.name.compareTo(other.source.name);
     if (sourceComp != 0) return sourceComp;
 
     var nameComp = name.compareTo(other.name);
     if (nameComp != 0) return nameComp;
 
     return version.compareTo(other.version);
   }
 
   /// Returns the pubspec for this package.
@@ skipping 63 matching lines @@
 
 class PubspecNameMismatchException implements Exception {
   final String expectedName;
   final String actualName;
 
   PubspecNameMismatchException(this.expectedName, this.actualName);
 
   String toString() => 'The name you specified for your dependency, '
     '"$expectedName", doesn\'t match the name "$actualName" in its pubspec.';
 }