Variadic tuple unpacking requires a star target -- why? about mypy

[sterliakov]

@TeamSpen210 well, it could, but such treatment should be consistent - either reject all or accept all.

from typing_extensions import Unpack

def foo() -> tuple[int, Unpack[tuple[str, ...]]]:
    return 1, "bar", "baz"

def bar() -> tuple[int|str, ...]:
    return 1, "bar", "baz"

a, b, c = foo()  # E: Variadic tuple unpacking requires a star target  [misc]
p, q, r = bar()

So "unpack tuple of int followed by 0 or more str" is bad, because "0 or more" may be not equal to 2. "Unpack tuple of 0 or more int | str" is considered safe, however. Hmm?

[TeamSpen210]

The error would be correct, since based on the types it could produce an incorrect result. Maybe Mypy should require you to ignore the error, but assume the length is going to match when unpacking the tuple. Alternatively, more verbose code with an assertion works:

tup = foo()
assert len(tup) == 3
a, b, c = tup