[HOP] Don't send HOPs to torch_dispatch (#131370)

I regretted the decision in
https://github.com/pytorch/pytorch/pull/130606. Most user
torch_dispatchs don't have enough to actually handle the HOP correctly,
so for now I'd prefer that users explicitly define the interaction
between the HOP and their torch_dispatch class.

An example is FlopCounterMode: if we allow HOPs to get passed to it, it
will ignore auto_functionalized(mm) by default but it will record flops
for mm, which is weird.

Test Plan:
- tests

Pull Request resolved: https://github.com/pytorch/pytorch/pull/131370
Approved by: https://github.com/ydwu4

test/dynamo/test_higher_order_ops.py

@@ -546,9 +546,8 @@ class GraphModule(torch.nn.Module):
         a = torch.tensor([1.0, 0.0, 1.0])
         b = torch.randn(3)
         t = TwoTensor(a, b)
-        res = cond_op(a.sum() > 0, torch.sin, torch.cos, (t,))
-        self.assertEqual(res.a, torch.sin(a))
-        self.assertEqual(res.b, torch.sin(b))
+        with self.assertRaisesRegex(NotImplementedError, "no rule registered"):
+            res = cond_op(a.sum() > 0, torch.sin, torch.cos, (t,))
 
         called = 0
 
@@ -580,10 +579,9 @@ class GraphModule(torch.nn.Module):
 
         a = torch.tensor([1.0, 0.1, 1.0])
         pred = a.sum() > 0
-        with MyMode():
-            res = cond_op(pred, torch.sin, torch.cos, (a,))
-        self.assertEqual(res, a.sin())
-        self.assertEqual(torch_dispatch_called, 1)
+        with self.assertRaisesRegex(NotImplementedError, "no rule registered"):
+            with MyMode():
+                res = cond_op(pred, torch.sin, torch.cos, (a,))
 
         py_impl_called = 0
 

torch/_ops.py

@@ -336,10 +336,10 @@ class HigherOrderOperator(OperatorBase):
                         # TODO(rzou): we should support torch_dispatch calling convention too.
                         result = handler(mode, *args, **kwargs)
                 else:
-                    with _pop_mode_temporarily() as mode:
-                        result = curr_mode.__torch_dispatch__(
-                            self_, overloaded_types, args, kwargs
-                        )
+                    raise NotImplementedError(
+                        "There was no rule registered for HOP {self._name} and mode {curr_mode}. "
+                        "We recommend filing an issue."
+                    )
                 if result is not NotImplemented:
                     return result
 
@@ -357,8 +357,9 @@ class HigherOrderOperator(OperatorBase):
                     # TODO(rzou): we should support torch_dispatch calling convention too.
                     result = handler(*args, **kwargs)
                 else:
-                    result = subclass_type.__torch_dispatch__(
-                        self_, overloaded_types, args, kwargs
+                    raise NotImplementedError(
+                        "There was no rule registered for HOP {self._name} and subclass {subclass_type}. "
+                        "We recommend filing an issue."
                     )
                 if result is not NotImplemented:
                     return result