Re: Unlifted primop types

The problem is that this also accepts things that aren't pointers at all! We could fix that *for primops* by changing RuntimeRep to something like data RuntimeRep = PtrRep Liftedness | ... But that would only work for primops (at least for now) so it may not be worth the breakage. On Wed, Aug 22, 2018, 7:45 AM Ben Gamari wrote:

Simon Peyton Jones writes:

...

| Huh! It looks like what we currently do for some primops is just use a | totally bogus kind. For example, mkWeak# will happily accept an Int# as | its first argument.

Well, I see primop MkWeakOp "mkWeak#" GenPrimOp o -> b -> (State# RealWorld -> (# State# RealWorld, c #))

and I believe (from Ben's message) that the "o" means "open type variable", which is the old terminology for what we now call levity-polymorphic.

Right; currently (largely for historical reasons) we use `o` to accommodate cases that accept both lifted and unlifted pointers.

Cheers,

- Ben