Const Generics

[BoxyUwU]

Duration: an hour maybe?

Description:

What's going on with const generics right now. Primarily intended for getting the rest of the types team up to date on the current const generics work especially as we move towards stabilizations

[lcnr]

This session was mostly to get people up-to date on const generics, I started taking some notes during the second half:

feature(adt_const_params)

requires ConstParamTy derive, only accepted for types satisfying our restrictions

no private fields :> concerning wrt to safety invariants

derive is definitely required once there are private fields :>

semver vs soundness
why not both :>

cool for generic const param types

hell yeah!

ConstParamTy could be auto trait...

again, private fields :> could just not auto impl if there are private fields

auto impl for easy cases, avoid adding it in cases that are definitely fine

fn foo<T: ConstParamTy, const N: T>() {}

taylor: could be implied bound

fn foo<const N: usize, T: ConstParamTy, const ARR: [T; N]>() {}

could do

fn foo<const N, T, const ARR: [T; N]>() {}

things which require opt in

#[non_exhaustive]

private fields: SCARY 💀

pub fields which are not publicly reachable

derive could be noop in the future :>