Adds several compile time checks for const generics.
Idea was based off of this reddit post.
#![feature(generic_const_exprs)]
/// Only allows for arguments of `C` to be alphabetic
struct AlphabeticTest<const C: char>
where
checks::char::Alphabetic<C>: checks::Passed;
// All letters are alphabetic, check passes.
let pass = AlphabeticTest::<'a'>; // Compiles
let pass = AlphabeticTest::<'B'>; // Compiles
let pass = AlphabeticTest::<'c'>; // Compiles
// Letters are not alphabetic, check fails.
let fail = AlphabeticTest::<'1'>; // Compile error!
let fail = AlphabeticTest::<'&'>; // Compile error!
let fail = AlphabeticTest::<'3'>; // Compile error!Custom checks can be implemented as well:
const fn is_binary(num: u8) -> bool { num == 0 || num == 1 }
struct BinaryOnly<const N: u8>
where
Check<{ is_binary(N) }>: Passed;
let pass = BinaryOnly::<0>; // Compiles
let pass = BinaryOnly::<1>; // Compiles
let fail = BinaryOnly::<2>; // Compiler error!Checks can also be defined with the check! macro, which will
also generate documentation / tests for example input:
check! { u8 =>
/// Matches all binary numbers (0, 1)
Binary(
passes: 0, 1
fails: 2, 3, 4
): |N| (N == 0 || N == 1)
}
struct BinaryOnly<const N: u8>
where
Binary<N>: Passed;
let pass = BinaryOnly::<0>; // Compiles
let pass = BinaryOnly::<1>; // Compiles
let fail = BinaryOnly::<2>; // Compiler error!Full list of provided checks can be found on the docs.rs page.