Code has since been merged into the const-str crate.
This crate provides a procedural macro, expand, that expands a string literal to an array of its characters.
// Expands to: ['H', 'e', 'l', 'l', 'o']
let foo: [char; 5] = expand!("Hello")
This can be useful in a number of situations, such as when O(1) random access to characters is desired.