id

Make unique identifiers.

[dependencies]
id = "0.1"

Usage

#[macro_use]
extern crate id;

...

let x = id!();

Each ID identifies a unique point in the source code, so you can't make more of them at runtime with a loop, nor with other such shenanigans.

Just take the code and do whatever you want with it, which I assume isn't much, because this library is pretty much useless.