Variable-length tuple doesn't narrow in isinstance

[A5rocks]

Bug Report

This may be a duplicate but I couldn't find any.

See the title for a short description or the short reproduction attached.

To Reproduce

a: object
b: tuple[type[int], ...]

if isinstance(a, b):
    reveal_type(a)

Expected Behavior

main.py:5: note: Revealed type is "builtins.int"
Success: no issues found in 1 source file

Actual Behavior

main.py:5: note: Revealed type is "builtins.object"
Success: no issues found in 1 source file

This works, however:

a: object
b: tuple[type[int]]

if isinstance(a, b):
    reveal_type(a)

Your Environment

https://mypy-play.net/?mypy=latest&python=3.11&gist=050eb94523510217a3bf91e9977539d0

[sobolevn]

Yes, looks like a problem that can be easily fixed.

Here's a more real-life example that can illustrate the same problem:

class Base: ...

class Impl1(Base): ...
class Impl2(Base): ...

impls: tuple[type[Base], ...] = (Impl1, Impl2)
some: object

if isinstance(some, impls):
    reveal_type(some)  # must be `Base`

I have a fix ready :)