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Passing an unpacked tuple of types as type arguments to the type parameters [T, *Ts] gets error #2363
Description
Describe the Bug
*Memo:
- pyrefly check test.py
- pyrefly 0.46.1
- Python 3.14.0
Passing an unpacked tuple of types as type arguments to the type parameters [T, *Ts] gets the error as shown below:
*Memo:
- mypy and ty don't get error.
from typing import Unpack
class Cls[T, *Ts]: ...
v1: Cls[*tuple[int, str, int, str]] # Error
v2: Cls[Unpack[tuple[int, str, int, str]]] # ErrorERROR Unpacked argument cannot be used for type parameter T
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yangdanny97 commentedon Feb 8, 2026
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The relevant part of the typing conformance test is here:
To me this seems like we should allow unpacking a regular tuple type in this context but not another TypeVarTuple.
When using concrete or unpacked type forms we need to make sure there are enough types, so
TA9[*tuple[()]]would still error, as wouldTA9[*tuple[*Ts2]]asukaminato0721 commentedon Feb 9, 2026
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migeed-z commentedon Feb 23, 2026
Note: PR #2364 which is currently landing will not address the conformance issue. Do not close it yet.
fix Passing an unpacked tuple of types as type arguments to the type …