🐛 Bug

I got an error when I tried to use jit to trace my autograd Function. In previous Pytorch versions(1.1.0), this works, but recently I updated to 1.4.0, and this stopped working. I'm not exactly sure which version exactly did this stopped working.

To Reproduce

Steps to reproduce the behavior:

1. Make sure you have Pytorch1.4.0
2. Make a custom autograd Function. In my case, I'm using this one

class raw(autograd.Function):
    @staticmethod
    def forward(ctx, inp):
        ctx.a = (inp * inp + 1).reciprocal()
        ctx.b = ctx.a.sqrt()
        return inp * ctx.b

    @staticmethod
    def backward(ctx, grad_output):
        return grad_output * ctx.a * ctx.b

3. Trace this Function.

from torch import jit
jit.trace(raw.apply, example_inputs=tc.randn(1))

4. The error should orginate from the line of tracing and look like this:

......................
    jit.trace(raw.apply, example_inputs=tc.randn(1))
  File "...\Python37\lib\site-packages\torch\jit\__init__.py", line 903, in trace
    name = _qualified_name(func)
  File "...\Python37\lib\site-packages\torch\_jit_internal.py", line 696, in _qualified_name
    "__module__ can't be None.".format(name))
RuntimeError: Could not get qualified name for class 'apply': __module__ can't be None.

Expected behavior

I expect the tracing to work like how the previous versions did.

Environment

Please copy and paste the output from our
environment collection script
(or fill out the checklist below manually).

You can get the script and run it with:

wget https://raw.githubusercontent.com/pytorch/pytorch/master/torch/utils/collect_env.py
# For security purposes, please check the contents of collect_env.py before running it.
python collect_env.py

PyTorch version: 1.4.0+cpu
Is debug build: No
CUDA used to build PyTorch: None

OS: Microsoft Windows 10 Home
GCC version: Could not collect
CMake version: Could not collect

Python version: 3.7
Is CUDA available: No
CUDA runtime version: No CUDA
GPU models and configuration: No CUDA
Nvidia driver version: No CUDA
cuDNN version: No CUDA

Versions of relevant libraries:
[pip3] numpy==1.16.3
[pip3] torch==1.4.0+cpu
[pip3] torchvision==0.5.0+cpu
[conda] Could not collect

Additional context

I'm bad at using Github so if I missed something please tell me :)

cc @suo