Crash involving tuple[Unpack[tuple]] annotation

[tjkuson]

Crash Report

Ran the mypy development branch on a codebase and it crashed. I managed to reduce the crash to a function parameter typed as a nested Unpack that was passed to an f-string.

The reason I was using the development branch of mypy was that it contained a bug fix not yet in the latest release. Downgrading to 1.6.1 causes the crash to stop happening unless you pass --enable-incomplete-feature=Unpack.

The closest issue I found was #16285 which seems to be closed as completed, but I am still able to produce this crash on the latest development branch which includes the commit that closed the issue.

Traceback

/tmp/hmm.py:5: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 1.6.1
Traceback (most recent call last):
  File "mypy/checkexpr.py", line 5366, in accept
  File "mypy/checkexpr.py", line 452, in visit_call_expr
  File "mypy/checkexpr.py", line 581, in visit_call_expr_inner
  File "mypy/checkexpr.py", line 1420, in check_call_expr_with_callee_type
  File "mypy/checkexpr.py", line 1514, in check_call
  File "mypy/checkexpr.py", line 1715, in check_callable_call
  File "mypy/checkexpr.py", line 2408, in check_argument_types
AssertionError:
/tmp/hmm.py:5: : note: use --pdb to drop into pdb

To Reproduce

from typing import Unpack


def foo(*keys: Unpack[tuple[Unpack[tuple]]]):
    return f"{keys}"

Your Environment

• Mypy version used: 1.6.1
• Mypy command-line flags: --enable-incomplete-feature=Unpack
• Python version used: 3.11.6
• Operating system and version: macOS 14.1

[ilevkivskyi]

A more minimal example:

from typing import Unpack

def test(*x: object): ...

keys: tuple[Unpack[tuple]]
test(keys, 1)

And this is actually a counter-example to the code I never fully understood. I will submit a fix either later today or tomorrow morning.

[tjkuson]

Thanks! I have changed the title to better reflect the crash. I wrongly thought the f-strings were involved, as changing the f-string to, e.g., a print call in the example made the crash stop.

[hauntsaninja]

Is the codebase you ran into this on open source?

[tjkuson]

Is the codebase you ran into this on open source?

No, sorry.