Add test for recursive type

Author: misakwa

tests/test_hook.py

@@ -130,3 +130,8 @@ def test_load_slots():
     p_str = pickle.dumps(bob)
 
     assert pickle.loads(p_str) == bob
+
+    # works for recursive types too
+    rec = thriftpy.load('parser-cases/recursive_union.thrift', use_slots=True)
+    rec_slots = rec.Dynamic.__slots__
+    assert rec_slots == ['boolean', 'integer', 'doubl', 'str', 'arr', 'object']