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PEP-646 tuple unpacking does not interpret tuple as a fixed set of arguments #19030

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terencehonles opened this issue May 5, 2025 · 1 comment
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PEP-646 tuple unpacking does not interpret tuple as a fixed set of arguments #19030

terencehonles opened this issue May 5, 2025 · 1 comment
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bug mypy got something wrong

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@terencehonles
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Bug Report

PEP-646 tuple unpacking does not interpret tuple as a fixed set of arguments.

To Reproduce

import sys
from _typeshed import ExcInfo

def hook(*exc_info: *ExcInfo) -> None:
    pass

reveal_type(hook)
sys.excepthook = hook

https://mypy-play.net/?mypy=master&python=3.12&gist=f9cacc6d3b30cfbb925d8c72bd8a4617

Expected Behavior

No error as hook takes one exception tuple.

Actual Behavior

main.py:7: note: Revealed type is "def (*exc_info: Unpack[tuple[type[builtins.BaseException], builtins.BaseException, types.TracebackType]])"
main.py:8: error: Incompatible types in assignment (expression has type "Callable[[VarArg(*tuple[type[BaseException], BaseException, TracebackType])], None]", variable has type "Callable[[type[BaseException], BaseException, TracebackType | None], Any]")  [assignment]
Found 1 error in 1 file (checked 1 source file)

Your Environment

  • Mypy version used: master
  • Mypy command-line flags: default
  • Mypy configuration options from mypy.ini (and other config files):
  • Python version used: 3.12
@terencehonles terencehonles added the bug mypy got something wrong label May 5, 2025
@terencehonles
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I didn't notice that the traceback type appears to be optional on typeshed

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@terencehonles