mypy incorrectly infers the type of a variable from different branches

[igalic]

in the following code,

@click.argument("filters", nargs=-1)
def cli(ctx,
        release: bool=False) -> None:
…
    if release is True:
        resources_class = iocage.lib.Releases.ReleasesGenerator
    else:
        resources_class = iocage.lib.Jails.JailsGenerator

    resources = resources_class(
        filters=filters,
        host=host,
        logger=logger
    )
…

mypy will issue the error:

iocage/cli/destroy.py:69:8: error: Incompatible types in assignment (expression has type Type[JailsGenerator], variable has type Type[ReleasesGenerator])

Also note that both, JailsGenerator and ReleaseGenerator inherit from the same common class Resource.

[ilevkivskyi]

Different people have different opinions about what should be inferred for resource_class: should it be a union? a common base class? just an error? A good idea is to give an explicit annotation:

    resource_class: Type[Resource]
    if release is True:
        resources_class = iocage.lib.Releases.ReleasesGenerator
    else:
        resources_class = iocage.lib.Jails.JailsGenerator

[igalic]

This doesn't seem to work.
The error remains the same.

[JukkaL]

What about this:

    resource_class: Union[Type[iocage.lib.Releases.ReleasesGenerator],
                          Type[iocage.lib.Jails.JailsGenerator]]
    if release is True:
        resources_class = iocage.lib.Releases.ReleasesGenerator
    else:
        resources_class = iocage.lib.Jails.JailsGenerator

[ilevkivskyi]

@igalic

This doesn't seem to work.
The error remains the same.

Strange, I just tried this code on master and it works perfectly:

class A: ...
class B(A): ...
class C(A): ...

resource: Type[A]
if bool():
    resource = B
else:
    resource = C

[igalic]

okay! updated to mypy! to i can no longer say if this was the cause of my error, or the fact that i wrote resource_class instead of resources_class._.

thank you all for you help and patience 💜💜💜