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Instances of type variables bounded by an iterable type support iteration but not unpacking #13402
Description
Bug Report
Instances of type variables bounded by an iterable type support iteration but not unpacking.
To Reproduce
from typing import TypeVar
class A:
pass
ATuple = TypeVar("ATuple", bound=tuple[A, ...])
def f(aa: ATuple) -> None:
for a in aa: # this is ok
print(a)
f((A(),))
def g(aa: ATuple) -> None:
(a,) = aa # "ATuple" object is not iterable
print(a)
g((A(),))Bounding the TypeVar by list[A] has the same behaviour as bounding it by tuple[A, ...].
Expected Behavior
No error -- an ATuple should support both iteration and unpacking.
Actual Behavior
f() checks clean.
In g(), unpacking fails with:
error: "ATuple" object is not iterable
error: Cannot determine type of "a"
Your Environment
This reproduces in all versions in the playground.
Activity
Allow unpacking from TypeVars by resolving bounds
Allow unpacking from TypeVars with iterable bounds (#13425)
Allow unpacking from TypeVars with iterable bounds (python#13425)
[0.980 backport] Allow unpacking from TypeVars with iterable bounds (#…