Validate that a package doesn't depend on itself.

utils/pub/validator/dependency.dart

Index: utils/pub/validator/dependency.dart
diff --git a/utils/pub/validator/dependency.dart b/utils/pub/validator/dependency.dart
index 66d2ae22f53cddb804d42096f8d7c2cb46674fc3..50655f30f982060754fb1075e587115342458f9d 100644
--- a/utils/pub/validator/dependency.dart
+++ b/utils/pub/validator/dependency.dart
@@ -31,6 +31,14 @@ class DependencyValidator extends Validator {
         return _warnAboutConstraint(dependency);
       }
 
+      if (dependency.name == entrypoint.root.name) {
+        warnings.add('You don\'t need to explicitly depend on your own '
+                'package.\n'
+            'Pub will make "package:${entrypoint.root.name}" imports work '
+                'automatically.');

[Bob Nystrom, 2013/01/03 20:52:45]

I find the future tense here a bit confusing. How about:

'Pub enables "package:${entrypoint.root.name}" imports implicitly.'

[nweiz, 2013/01/03 21:08:12]

Done.

+        return;
+      }
+
       return new Future.immediate(null);
     });
   }