Need to create a function that works only on types matching certain predicate? Fear no more!

#![allow(incomplete_features)]
#![feature(generic_const_exprs)]

fn something<T>(val: T)
where
    Assert<{ core::mem::size_of::<T>() < 768 }>: IsTrue,
    //       ^-----------------------------^ any const-expression will do
{
    //
}

fn main() {
    something([0u8; 0]); // ok
    something([0u8; 512]); // ok
    something([0u8; 1024]); // compilation error, yass
}

// ---

pub enum Assert<const CHECK: bool> {
    //
}

pub trait IsTrue {
    //
}

impl IsTrue for Assert<true> {
    //
}

Example use cases include trying to write an async executor for a platform that has tight RAM limits 😅