typecheck: Adding check for NoneType before calling is_descendant

pyta-uoft · Aug 17, 2018 · a5d3075 · a5d3075
1 parent d56c646
commit a5d3075
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/python_ta/typecheck/base.py b/python_ta/typecheck/base.py
@@ -660,8 +660,8 @@ def unify(self, t1: type, t2: type,
             elif ct1 == Any or ct2 == Any:
                 return TypeInfo(ct1) if ct1 != Any else TypeInfo(ct2)
             # Handle inheritance
-            elif self.type_store and \
-                    self.type_store.is_descendant(ct1, ct2):
+            elif self.type_store and ct1 is not None and ct2 is not None \
+                    and self.type_store.is_descendant(ct1, ct2):
                 return TypeInfo(ct1)
             else:
                 for tn in [tnode1, tnode2]: