(🎁) `isinstance`/`issubclass` only accept `typing.Union`s of `type`s, not other type forms

[KotlinIsland]

Until type forms are properly supported by the type system, I wonder if this could be special cased?

from typing import Any

isinstance(1, str | Any)  # no error, fails at runtime with TypeError: typing.Any cannot be used with issubclass()

FYI mypy is incorrectly inferring this as a types.UnionType but it is actually a typing.Union(#12369), I don't think you can have a UnionType with type forms in it.

PyCharm correctly warns here:

related: python/typeshed/issues/7505

[flying-sheep]

Of course | also flattens other UnionTypes, so this should also be fine:

Number = int | float

isinstance(1, Number | str)