#rust-lang

woboats: sooo https://twitter.com/withoutboats/status/9701510...

woboats: have you seen eternaleye rant about why he prefers records + implicits to typeclasses?

(in that model you wouldn't need to extend it to get "meta traits", since traits => struct type, impls => const values of the trait type, bounds => const generic implicits of those trait types)

eddyb: Not quite; bounds => const parameters of those trait types, _inference_ of bounds => marking those parameters as implicits

eternaleye: sorry, yeah, I was conflating the two

(as Rust does today)

Yeah, but deconflating them is a big part of the point :P

For example, having a function that works on a field be able to take an abelian group and a commutative monoid :P

(Which are... Add/Zero and Mul/One :P)

eternaleye: or rather, I was describing how current Rust conflates the two - if you had const generics *and* implicits you could use them separately

eddyb: One thing is that it _does_ require rank-2 types, or else you miss out on associated types

oh right

eternaleye: suddenly this seems harder than a generalization of traits to change the kind of Self

eddyb: I mean, traits are already doing this

The main thing is that this exposes the tools traits use, rather than exposing traits

Implicits expose "type-directed value selection", rank-2 types expose associated types, etc

I do feel this overall reduces the amount of magic in the system, in part because it breaks it up into small, orthogonal components

!rfc 2357

[PR 2357] <open> RFC: 👻👤 (Ghost Busting) <https://github.com/rust-lang/rfcs/pull/2357>;

^-- My newest RFC =P

centril: Commented on it.

isHavvy: #[non_exhaustive] acts as a form of privacy wrt. in-crate/outside of crate, yes?

Yes.

aight

isHavvy: but not in-crate privacy as in pub(super) etc. ?

Right.

Though theoretically #[non_exhaustive] could be extended to give finer control over in-crate privacy.

isHavvy: heh.. what is wrong with pub/pub(crate/pub(super)

that just sounds like inventing new syntax for visibility... =P

well, `#[non_exhaustive(crate)]` would be obvious

but one could also mention inventing new syntax for specifying PhantomData =P

scottmcm: not obvious to me 0P

=P

Also, I wouldn't be surprised if the syntax for non_exhaustive changed from a macro to `...` in the type, or something

but as usual, macro first, then syntax later if really needed

s/macro/attribute/

unimportant question: what's the emoji after the ghost? just looks like a torso+head to me...

(aka reason 487 to not try to communicate precisely by using emoji...)

scottmcm: bust

ghost + bust

see C-worm :P

There's too much stomach in the emoji for me to get "bust", since for that I expect something like https://en.wikipedia.org/wiki/Arles_bust

scottmcm: ^

nox: ah, that does look more like a bust than what I see