cps attribute

[mtzguido]

We have a cps attribute in prims, which is used for the M effect to make it processable by DM4F.

assume val cps : attribute
(* .... *)
effect M (a:Type) = Tot a (attributes cps)

But, we special case it a lot, to the point that one can even delete the definition of the cps attribute, since the desugarer recognizes that when it sees cps, it means to add the CPS cflag, without trying to interpret/lookup cps in any way.

So what's the point of the attribute? And did we expect to have many cps effects? Perhaps for layering?

For layering, I would have assumed the syntax would be something like:

new_effect_transformer StateT = {
    repr = fun a -> s -> M (a * s); 
    (* ... plus the usual DM4F *)
}

new_effect StExn = StateT EXN (* or similar *)

without a need for another M.

Summoning @kyoDralliam @nikswamy @catalin-hritcu @msprotz in case you guys remember. Personally I vote for removing the attribute and corresponding CPS flag.

[mtzguido]

The cflag exists since the M effect gets unfolded (as it should) during typechecking, and we'd lose track of it otherwise. But the desugaring is crazy anyway.