redirect iter(range) to range.__iter__() (#161803)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/161803
Approved by: https://github.com/anijain2305
ghstack dependencies: #161801, #161802

test/dynamo/test_functions.py

@@ -3529,7 +3529,6 @@ class GraphModule(torch.nn.Module):
             return a + b
         return a - b
 
-    @unittest.expectedFailure
     @make_test
     def test_range_iterator_2(a, b):
         # should pass once we stop having three different paths on call_iter

torch/_dynamo/variables/builtin.py

@@ -1820,6 +1820,8 @@ class BuiltinVariable(VariableTracker):
     def call_iter(self, tx: "InstructionTranslator", obj, *args, **kwargs):
         if isinstance(obj, variables.IteratorVariable):
             ret = obj
+        elif isinstance(obj, variables.RangeVariable):
+            ret = obj.call_method(tx, "__iter__", [], {})
         else:
             # Handle the case where we are iterating over a tuple, list or iterator
             ret = self._call_iter_tuple_list(tx, obj, *args, **kwargs)