Crate inline_const

You don’t want to wait until inline consts are stable? This crate offers much of the functionality of inline consts in a pure macro-based implementation, at a slight const of convenience: you need to explicitly annotate the type of the constant.

use std::net::Ipv6Addr;
 
use inline_const::inline_const;
 
fn mock_ip(use_localhost: bool) -> &'static Ipv6Addr {
    if use_localhost {
        &Ipv6Addr::LOCALHOST
    } else {
        inline_const! { [&'static Ipv6Addr]
            &Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 0)
        }
    }
}

Unlike the current unstable implementation of inline-const, this crate even supports consts that depend on generic parameters, albeit at some further annotation cost: you need to repeat the generic parameters that the constant refers to, and their lifetime bounds.

use inline_const::inline_const;
 
fn make_static_vec<T: 'static>() -> &'static Vec<T>{
    inline_const! { <T: 'static> [&'static Vec<T>] &Vec::new() }
}

Macros

const_array	Macro to generate an array by repeating a constant N times.
inline_const	Macro to generate a constant as an inline expression.