dynamo: Handle objects in graph that do not support weakref (#163168)

We are seeing crashes of the form
```
Traceback (most recent call last):
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/symbolic_convert.py", line 1487, in run
    while self.step():
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/symbolic_convert.py", line 1348, in step
    self.dispatch_table[inst.opcode](self, inst)
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/symbolic_convert.py", line 2437, in LOAD_ATTR
    self._load_attr(inst)
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/symbolic_convert.py", line 2425, in _load_attr
    result = BuiltinVariable(getattr).call_function(
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/variables/builtin.py", line 1347, in call_function
    return handler(tx, args, kwargs)
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/variables/builtin.py", line 967, in <lambda>
    tx, [v.realize() for v in args], kwargs
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/variables/builtin.py", line 967, in <listcomp>
    tx, [v.realize() for v in args], kwargs
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/variables/lazy.py", line 72, in realize
    self._cache.realize()
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/variables/lazy.py", line 33, in realize
    self.vt = builder.VariableBuilder(tx, self.source)(self.value)
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/variables/builder.py", line 445, in __call__
    vt = self._wrap(value)
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/variables/builder.py", line 1043, in _wrap
    torch._dynamo.utils.store_user_object_weakref(value)
  File "/packages/aps_ads_vm/launcher_multiapp-inplace#link-tree/torch/_dynamo/utils.py", line 4694, in store_user_object_weakref
    user_obj_id_to_weakref[obj_id] = weakref.ref(obj)
torch._dynamo.exc.InternalTorchDynamoError: TypeError: cannot create weak reference to 'torch.Event' object
```

This pull request makes us gracefully graph break, vs explicitly crashing.

I've added a test which reproduces the issue. There is a side discussion re:
how did torch.Event support ever work here, since it appears you cannot take a
weakref to a torch.Event

Pull Request resolved: https://github.com/pytorch/pytorch/pull/163168
Approved by: https://github.com/Lucaskabela, https://github.com/jansel

test/dynamo/test_compile.py

@@ -234,6 +234,27 @@ class InPlaceCompilationTests(TestCase):
         with self.assertRaises(IndexError):
             fn(torch.randn(10), 99)
 
+    def test_list_bad_weakref(self):
+        import weakref
+
+        a = torch.Event()
+        with self.assertRaises(TypeError):
+            weakref.ref(a)
+
+        @torch.compile(backend="eager")
+        class Mod(torch.nn.Module):
+            def __init__(self, event):
+                super().__init__()
+                self.event = event
+
+            def forward(self, x):
+                return x * int(self.event.query())
+
+        e = torch.Event()
+        m = Mod(e)
+        a = torch.randn(10)
+        self.assertEqual(m(a), a)
+
 
 # The private variants of the below functions are extensively tested
 # So as long as the signatures match we're good

torch/_dynamo/graph_break_registry.json

@@ -2718,5 +2718,13 @@
       "Explanation": "Dyanmo does not support tracing mutations on a class when its __dict__ is materialized",
       "Hints": []
     }
+  ],
+  "GB0272": [
+    {
+      "Gb_type": "Failed to make weakref to User Object",
+      "Context": "user_objected: {obj}",
+      "Explanation": "Object does not allow us to make a weakref to it",
+      "Hints": []
+    }
   ]
 }

torch/_dynamo/utils.py

@@ -4696,7 +4696,18 @@ def get_user_object_from_id(obj_id: int) -> Any:
 
 def store_user_object_weakref(obj: object) -> None:
     obj_id = id(obj)
-    user_obj_id_to_weakref[obj_id] = weakref.ref(obj)
+    try:
+        user_obj_id_to_weakref[obj_id] = weakref.ref(obj)
+    except TypeError as e:
+        from .exc import unimplemented_v2
+
+        unimplemented_v2(
+            gb_type="Failed to make weakref to User Object",
+            context=f"user_objected: {obj}",
+            explanation="Object does not allow us to make a weakref to it",
+            hints=[],
+            from_exc=e,
+        )
 
 
 class CompileTimeInstructionCounter: