1 files changed, 33 insertions, 4 deletions
diff --git a/lib/sqlalchemy/sql/traversals.py b/lib/sqlalchemy/sql/traversals.py
index aceed99a5..94e635740 100644
--- a/lib/sqlalchemy/sql/traversals.py
+++ b/lib/sqlalchemy/sql/traversals.py
@@ -19,6 +19,7 @@ from typing import Callable
 from typing import Deque
 from typing import Dict
 from typing import Iterable
+from typing import Optional
 from typing import Set
 from typing import Tuple
 from typing import Type
@@ -39,7 +40,7 @@ COMPARE_FAILED = False
 COMPARE_SUCCEEDED = True
 
 
-def compare(obj1, obj2, **kw):
+def compare(obj1: Any, obj2: Any, **kw: Any) -> bool:
     strategy: TraversalComparatorStrategy
     if kw.get("use_proxies", False):
         strategy = ColIdentityComparatorStrategy()
@@ -49,7 +50,7 @@ def compare(obj1, obj2, **kw):
     return strategy.compare(obj1, obj2, **kw)
 
 
-def _preconfigure_traversals(target_hierarchy):
+def _preconfigure_traversals(target_hierarchy: Type[Any]) -> None:
     for cls in util.walk_subclasses(target_hierarchy):
         if hasattr(cls, "_generate_cache_attrs") and hasattr(
             cls, "_traverse_internals"
@@ -482,14 +483,22 @@ class TraversalComparatorStrategy(HasTraversalDispatch, util.MemoizedSlots):
 
     def __init__(self):
         self.stack: Deque[
-            Tuple[ExternallyTraversible, ExternallyTraversible]
+            Tuple[
+                Optional[ExternallyTraversible],
+                Optional[ExternallyTraversible],
+            ]
         ] = deque()
         self.cache = set()
 
     def _memoized_attr_anon_map(self):
         return (anon_map(), anon_map())
 
-    def compare(self, obj1, obj2, **kw):
+    def compare(
+        self,
+        obj1: ExternallyTraversible,
+        obj2: ExternallyTraversible,
+        **kw: Any,
+    ) -> bool:
         stack = self.stack
         cache = self.cache
 
@@ -551,6 +560,10 @@ class TraversalComparatorStrategy(HasTraversalDispatch, util.MemoizedSlots):
                 elif left_attrname in attributes_compared:
                     continue
 
+                assert left_visit_sym is not None
+                assert left_attrname is not None
+                assert right_attrname is not None
+
                 dispatch = self.dispatch(left_visit_sym)
                 assert dispatch, (
                     f"{self.__class__} has no dispatch for "
@@ -595,6 +608,14 @@ class TraversalComparatorStrategy(HasTraversalDispatch, util.MemoizedSlots):
         self, attrname, left_parent, left, right_parent, right, **kw
     ):
         for l, r in zip_longest(left, right, fillvalue=None):
+            if l is None:
+                if r is not None:
+                    return COMPARE_FAILED
+                else:
+                    continue
+            elif r is None:
+                return COMPARE_FAILED
+
             if l._gen_cache_key(self.anon_map[0], []) != r._gen_cache_key(
                 self.anon_map[1], []
             ):
@@ -604,6 +625,14 @@ class TraversalComparatorStrategy(HasTraversalDispatch, util.MemoizedSlots):
         self, attrname, left_parent, left, right_parent, right, **kw
     ):
         for l, r in zip_longest(left, right, fillvalue=None):
+            if l is None:
+                if r is not None:
+                    return COMPARE_FAILED
+                else:
+                    continue
+            elif r is None:
+                return COMPARE_FAILED
+
             if (
                 l._gen_cache_key(self.anon_map[0], [])
                 if l._is_has_cache_key