Hi Matthew
> I like the proposal. I also support the covariance.>> One question though.> The RFC mentions possible future use of "nothing" as a bottom type for> parameters in generics. This makes a lot of sense to me. Even without> generics, it could be used for parameters in abstract methods.>> So why not already introduce "nothing" as the universal bottom type, and> use it instead of "noreturn"?> Can "noreturn" do anything that "nothing" can't?
I'm also a little confused by this statement. The exact wording from the RFC is:
> Arguments for never: ... It's a full-fledged type, rather than a keyword used in a
> specific situation. A far-in-the-future generics proposal could use never as a placeholder inside
> contravariant generic types.
From what I understand, in Hack noreturn and never are both
full-fledged types. Nothing is a bottom type while noreturn is not.
Since in your proposal noreturn would also be a bottom type there's no
reason why it couldn't be used in covariant or contravariant generic
parameters.
Please correct me if I'm missing something.
Ilija