`BASEDMYPY_TYPE_CHECKING` variable

[DetachHead]

it would be nice to have a variable like TYPE_CHECKING that's only true in basedmypy, so we can conditionally support based features while still supporting regular type checkers:

from basedtyping import BASEDMYPY_TYPE_CHECKING

if IS_BASEDMYPY:
    foo: Foo & Bar
else:
    foo: object

related: #37

[KotlinIsland]

Something like this?

BASEDMYPY: Literal[False] = False

If BASEDMYPY:
    A = B & C
else:
    A = object

> mypy --always-true BASEDMYPY

[DetachHead]

Yeah but it should be enabled by default

[KotlinIsland]

There is MYPY, can we close this issue?

[DetachHead]

nah, because not only does it not work at all, it also won't allow for conditionally defining stuff depending on whether you're using basedmypy or mypy, like in my example

[KotlinIsland]

What about we introduce BASEDMYPY, equivalent to MYPY?