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kotlinlang

What's the purpose of `widen` in Arrow? A lot of its implementations just return the receiver immediately because of how variance works already. Is there a reason to keep it?

Hmm, not 100%. I've stared at this function a lot to remove it :joy:, is it not deprecated?

Doing a quick google <https://github.com/typelevel/cats/issues/1080|search>, it seems that it was actually meant for `Functor` since `Functor` is not covariant. So that makes sense, so you use `widen` for what you'd normally rely on covariance.

We have covariance everywhere, so we get automatic widening from the type system. So if it's not yet deprecated I think it should be.

cc\\ <@U05N94LDU79>

<https://github.com/arrow-kt/arrow/pull/3369>