Fix backwards compatibility bug in Word2Vec (#3415)

* add missing model file

* update test

gensim/models/word2vec.py

@@ -1986,9 +1986,6 @@ def _load_specials(self, *args, **kwargs):
             for a in ('hashfxn', 'layer1_size', 'seed', 'syn1neg', 'syn1'):
                 if hasattr(self.trainables, a):
                     setattr(self, a, getattr(self.trainables, a))
-            if hasattr(self, 'syn1'):
-                self.syn1 = self.syn1
-                del self.syn1
             del self.trainables
         if not hasattr(self, 'shrink_windows'):
             self.shrink_windows = True

gensim/test/test_word2vec.py

@@ -275,6 +275,13 @@ def test_persistence(self):
         self.assertTrue(np.allclose(wv.vectors, loaded_wv.vectors))
         self.assertEqual(len(wv), len(loaded_wv))
 
+    def test_persistence_backwards_compatible(self):
+        """Can we still load a model created with an older gensim version?"""
+        path = datapath('model-from-gensim-3.8.0.w2v')
+        model = word2vec.Word2Vec.load(path)
+        x = model.score(['test'])
+        assert x is not None
+
     def test_persistence_from_file(self):
         """Test storing/loading the entire model trained with corpus_file argument."""
         with temporary_file(get_tmpfile('gensim_word2vec.tst')) as corpus_file: