[Bug]: torchdynamo.export doesn't work with model attribute initialized outside of constructor

[tugsbayasgalan]

🐛 Describe the bug

class Foo(torch.nn.Module):
    a = 4

    def __init__(self):
        super().__init__()

    def forward(self, x):
        return x.cos() + self.a 

torchdynamo.config.dynamic_shapes = True
torchdynamo.export(Foo(), torch.randn(3, 4), aten_graph=True)

Error logs

  File "/mnt/xarfuse/uid-23137/7756fc57-seed-nspid4026533012_cgpid17879168-ns-4026533009/torchdynamo/symbolic_convert.py", line 308, in step
    getattr(self, inst.opname)(inst)
  File "/mnt/xarfuse/uid-23137/7756fc57-seed-nspid4026533012_cgpid17879168-ns-4026533009/torchdynamo/symbolic_convert.py", line 805, in LOAD_ATTR
    result = BuiltinVariable(getattr).call_function(
  File "/mnt/xarfuse/uid-23137/7756fc57-seed-nspid4026533012_cgpid17879168-ns-4026533009/torchdynamo/variables/builtin.py", line 337, in call_function
    result = handler(tx, *args, **kwargs)
  File "/mnt/xarfuse/uid-23137/7756fc57-seed-nspid4026533012_cgpid17879168-ns-4026533009/torchdynamo/variables/builtin.py", line 661, in call_getattr
    return obj.var_getattr(tx, name).add_options(options)
  File "/mnt/xarfuse/uid-23137/7756fc57-seed-nspid4026533012_cgpid17879168-ns-4026533009/torchdynamo/variables/nn_module.py", line 153, in var_getattr
    unimplemented(f"class property {typestr(base)} {typestr(subobj)}")
  File "/mnt/xarfuse/uid-23137/7756fc57-seed-nspid4026533012_cgpid17879168-ns-4026533009/torchdynamo/exc.py", line 71, in unimplemented
    raise Unsupported(msg)
torchdynamo.exc.Unsupported: class property Foo int

Did Dynamo succeed?

• Does dynamo.optimize("eager") succeed?

Did AOT succeed?

• Did dynamo.optimize("aot_eager") succeed?

Did Inductor succeed?

• Does dynamo.optimize("inductor") succeed?

Minified repro

Repro above

[anijain2305]

Fix at pytorch/pytorch#87531