unreachable_checked!

A fork of Kixunil/dont_panic that uses unreachable! instead of panic!

Ensures that code can't panic at compile time.

Example

This code will compile and (not) run just fine:

let should_panic = false;
if should_panic {
    unreachable_checked!("This will never execute.");
}

However, this code will cause a linking error:

let should_panic = true;
if should_panic {
    unreachable_checked!("This will never execute.");
}

Caveats

• This works only when the appropriate opt_level is specified - it may require release build. You can use the panic cargo feature to panic instead
• The error message is a weird link error. You don't get line number, etc.
• There may be situations in which you know that the code is unreachable but the compiler can't prove it.

lib.rs:

This crate provides macros that look just like unreachable!() but instead of panicking, they cause a linking error if their calls are not optimized-out. This can be used to ensure the compiler optimizes away some code.

Example

#[macro_use]
extern crate unreachable_checked;

fn main() {
/*
    let x = 6 * 9;
    if x == 42 {
        unreachable_checked!("6 * 9 == 42");
    }
*/
let x = false;
if x {
    unreachable_checked!("42");
}
}

Compile with --release or --features=panic