Don't allow packages to depend on themselves.

sdk/lib/_internal/pub/test/pubspec_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 pubspec_test;
 
 import 'package:unittest/unittest.dart';
 
 import '../lib/src/pubspec.dart';
 import '../lib/src/source.dart';
@@ skipping 85 matching lines @@
       expectFormatError('''
 dependencies:
   foo:
     mock: ok
 dev_dependencies:
   foo:
     mock: ok
 ''');
     });
 
+    test("throws if it dependes on itself", () {
+      expectFormatError('''
+name: myapp
+dependencies:
+  myapp:
+    mock: ok
+''');
+    });
+
+    test("throws if it has a dev dependency on itself", () {
+      expectFormatError('''
+name: myapp
+dev_dependencies:
+  myapp:
+    mock: ok
+''');
+    });
+
     test("throws if the description isn't valid", () {
       expectFormatError('''
 dependencies:
   foo:
     mock: bad
 ''');
     });
 
     test("throws if 'name' is not a string", () {
       expectFormatError('name: [not, a, string]');
@@ skipping 98 matching lines @@
 
       test("throws if the sdk isn't a valid version constraint", () {
         expectFormatError('''
 environment:
   sdk: "oopies"
 ''');
       });
     });
   });
 }