Crate checks 

checks

Adds several compile time checks for const generics.

Idea was based off of this reddit post.

Note: This library requires use of the #![feature(generic_const_exprs)] flag.

Usage:

#![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.

Modules

bool

char

i8

i16

i32

i64

i128

isize

u8

u16

u32

u64

u128

usize

Macros

check

Defines a new check, and also generates docs/tests for example input of the check.

Enums

Check

The base check, which matches Passed when E is true, and Failed when E is false.

Traits

Conclusion

Used to match the result of a check.

Failed

Indicates that a check has failed.

Passed

Indicates that a check has passed.