Why does coroutine continuation have the property ...

# coroutines

[Ricky Choi]

Why does coroutine continuation have the property of generic ~invariance~*contravariance*?

[ephemient]

that is contravariant, not invariant

[streetsofboston]

Contravariance opens up the possibility that a type is a subtype of Continuation<T> if its generic type parameter is a supertype of T, adding a bit of typing flexibility while still having type-safety. I think that if it were invariant, then that flexibility just wouldn't be there.