Implement basic *args support for variadic generics #13889
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This implements the most basic support for the *args feature but various edge cases are not handled in this PR because of the large volume of places that needed to be modified to support this. In particular, we need to special handle the ARG_STAR argument in several places for the case where the type is a UnpackType. Finally when we actually check a function we need to construct a TupleType instead of a builtins.tuple.
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According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉 |
JukkaL
approved these changes
Oct 17, 2022
ilevkivskyi
reviewed
Oct 21, 2022
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| # TODO: add less trivial tests with prefix/suffix etc. | ||
| # TODO: add tests that call with a type var tuple instead of just args. | ||
| def args_to_tuple(*args: Unpack[Ts]) -> Tuple[Unpack[Ts]]: |
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Will this PR work for a non-typevartuple use case? I have seen people use something like this def foo(*args: Unpack[tuple[int, str]]) (but it will be probably more useful with a type alias, to re-use in different functions, similar to how we allow TypedDicts to re-use types for **kwds).
Btw currently this use case may cause a crash, see first example in #13790 (comment)
If this PR helps with this direction, could you please add a test case? Otherwise consider this a sub-feature request.
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Another common use case with *args which crashes currently.
from typing import Callable
from typing_extensions import TypeVarTuple, Unpack
Ts = TypeVarTuple("Ts")
def a(var: int) -> None: ...
def func(f: Callable[[Unpack[Ts]], None], *args: Unpack[Ts]) -> None:
f(*args)
func(a, 42)
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This implements the most basic support for the *args feature but various edge cases are not handled in this PR because of the large volume of places that needed to be modified to support this.
In particular, we need to special handle the ARG_STAR argument in several places for the case where the type is a UnpackType. Finally when we actually check a function we need to construct a TupleType instead of a builtins.tuple.