Refactor Source.

sdk/lib/_internal/pub/lib/src/command/cache_list.dart

Index: sdk/lib/_internal/pub/lib/src/command/cache_list.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command/cache_list.dart b/sdk/lib/_internal/pub/lib/src/command/cache_list.dart
index 18408e520c744ea155f1c3bbdcafd60de191c800..39d67e68b7466321c61530a2491644f1a4105c61 100644
--- a/sdk/lib/_internal/pub/lib/src/command/cache_list.dart
+++ b/sdk/lib/_internal/pub/lib/src/command/cache_list.dart
@@ -9,6 +9,7 @@ import 'dart:convert';
 
 import '../command.dart';
 import '../log.dart' as log;
+import '../source/cached.dart';
 
 /// Handles the `cache list` pub command.
 class CacheListCommand extends PubCommand {
@@ -21,7 +22,8 @@ class CacheListCommand extends PubCommand {
     // TODO(keertip): Add flag to list packages from non default sources.
     var packagesObj = <String, Map>{};
 
-    for (var package in cache.sources.defaultSource.getCachedPackages()) {
+    var source = cache.sources.defaultSource as CachedSource;
+    for (var package in source.getCachedPackages()) {
       var packageInfo = packagesObj.putIfAbsent(package.name, () => {});
       packageInfo[package.version.toString()] = {'location': package.dir};
     }