Crate const_generic_wrap[−][src]

Expand description

Simple wrapper for const generics.

Usage

Currently ‘the type of const parameters must not depend on other generic parameters’ (E0770).

struct A<N, const C : N>(N);

With this crate we can solve this by wrapping cosnt generic.

use const_generic_wrap::*;
struct A<N, C>(N, C) where C : ConstWrap<BaseType = N>;
// WrapU32 is ZST, so the size of A is as same as u32.
assert_eq!(mem::size_of::<WrapU32<12>>(), 0);
assert_eq!(mem::size_of::<A::<u32, WrapU32<12>>>(), mem::size_of::<u32>());

// you can selectively use const or non const
struct B<N, C>(N, C) where C : ConstOrValue<N>, N : Constable; // or it can be C : Into<N>
fn add_b<N, C>(v : B<N, C>) -> N where N : Add<Output = N> + Constable, C : ConstOrValue<N>{
    v.0 + v.1.into()
}
let b_non_const = B(31, 11);
let b_const = B(31, WrapI32::<11>);
assert_eq!(add_b(b_non_const), add_b(b_const));