torch-nn-functional-mypy-bug-when-torchvision-installed

description

mypy crashes on a file that imports torch.nn.functional when torchvision is installed in conjunction with --follow-imports=skip flag.

traceback

$ mypy --show-traceback --follow-imports=skip harmless.py
Traceback (most recent call last):
  File "/home/eytan/miniconda3/envs/mypy/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/home/eytan/miniconda3/envs/mypy/lib/python3.10/site-packages/mypy/__main__.py", line 15, in console_entry
    main()
  File "mypy/main.py", line 103, in main
  File "mypy/main.py", line 187, in run_build
  File "mypy/build.py", line 193, in build
  File "mypy/build.py", line 268, in _build
  File "mypy/build.py", line 2950, in dispatch
  File "mypy/build.py", line 3348, in process_graph
  File "mypy/build.py", line 3475, in process_stale_scc
  File "mypy/build.py", line 2507, in write_cache
  File "mypy/build.py", line 1568, in write_cache
  File "mypy/nodes.py", line 390, in serialize
  File "mypy/nodes.py", line 4012, in serialize
  File "mypy/nodes.py", line 3949, in serialize
  File "mypy/nodes.py", line 3374, in serialize
  File "mypy/types.py", line 671, in serialize
  File "mypy/types.py", line 2428, in serialize
  File "mypy/types.py", line 1451, in serialize
  File "mypy/types.py", line 671, in serialize
  File "mypy/types.py", line 3093, in serialize
AssertionError: Internal error: unresolved placeholder type None

Minimal example repo with instructions

• repository here

environment

• OS: Ubuntu 22.04.4
• miniconda: 24.5.0
• mypy: 1.11.1

reproduced in:

• Python: 3.10, 3.11, 3.12

full pip freezes in example repo

Start with the linked minimal example repository and run the reported mypy command using --follow-imports=skip with torch and torchvision installed. Trace the cache-writing path named in mypy/build.py, mypy/nodes.py, and mypy/types.py, then verify that the command completes without the unresolved placeholder type assertion.