Description
Bug Report
Any attempt to call isinstance with a variable annotated as a TypeAlias seems to result in the error message error: Parameterized generics cannot be used with class or instance checks, even if the aliased type is non-generic. mypy_primer points at #18173 as the breaking commit, but that PR seems to have been intended to deal with type aliases of generic types; it seems that we're treating all TypeAlias-based aliases as generic types, which AFAICT is broader than intended.
To Reproduce
MyPy playground link, using current master
from typing import Any, TypeAlias
class Foo:
pass
Alias: TypeAlias = Foo
def is_foo(x: Any) -> bool:
return isinstance(x, Alias)Expected Behavior
MyPy finds no errors, matching the runtime behavior. Pyright and mypy 1.4 both find no errors in my minimal example.
Actual Behavior
Per the playground link:
main.py:9: error: Parameterized generics cannot be used with class or instance checks [misc]
Found 1 error in 1 file (checked 1 source file)
Your Environment
I found this when dogfooding mypy master commit c4e2eb7 against Dropbox's internal Python repo, but mypy_primer also reproduces the same thing, as does mypy playground.