[dynamo] fix None routing bug during var_getattr on UDO (#111614)

jansel · pytorchmergebot · commit f5088d2e4578 · 2023-10-29T01:57:43.000Z
Pull Request resolved: #111614 Approved by: https://github.com/jansel
diff --git a/torch/_dynamo/symbolic_convert.py b/torch/_dynamo/symbolic_convert.py
@@ -341,8 +341,9 @@ def inner(self: "InstructionTranslatorBase", inst: Instruction):
         elif isinstance(value, UserDefinedObjectVariable):
             x = value.var_getattr(self, "__bool__")
             # if __bool__ is missing, trying __len__ to infer a truth value.
-            if x.is_python_constant() and x.as_python_constant() is None:
+            if isinstance(x, GetAttrVariable):
                 x = value.var_getattr(self, "__len__")
+
             # __bool__ or __len__ is function
             if isinstance(x, UserMethodVariable):
                 state = self.copy_graphstate()
diff --git a/torch/_dynamo/variables/user_defined.py b/torch/_dynamo/variables/user_defined.py
@@ -444,10 +444,13 @@ def var_getattr(self, tx, name):
         self._check_for_getattribute()
         getattr_fn = self._check_for_getattr()
 
+        class NO_SUCH_SUBOBJ:
+            pass
+
         try:
             subobj = self._getattr_static(name)
         except AttributeError:
-            subobj = None
+            subobj = NO_SUCH_SUBOBJ
             if isinstance(getattr_fn, types.FunctionType):
                 return variables.UserMethodVariable(
                     getattr_fn, self, source=source, **options
