lib.rs

#![feature(trace_macros)]

trace_macros!(true);

macro_rules! assert_ct_not_equal {
    ($a:tt, $b:tt) => {
        #[deny(const_err)]
        const _: () = {
            macro_rules! is_a {
                ($a) => { true };
                ($b) => { false };
            };
            [()][is_a!($b) as usize]
        };
    }
}

macro_rules! assert_ct_all_different {
    () => {};
    ($single:tt) => {};
    ($first:tt, $($rest:tt,)*) => {
        #[deny(const_err)]
        const _: () = {
            $(
                assert_ct_not_equal!($first, $rest);
            )*
        };
        assert_ct_all_different!($($rest,)*);
    }
}

macro_rules! assert_all_literals {
    ($($l:literal,)*) => {};
}

macro_rules! assert_ct_all_different_literals {
    ($($tok:tt),*) => {
        assert_ct_all_different_literals!($($tok,)*);
    };
    ($($tok:tt,)*) => {
        assert_all_literals!($($tok,)*);
        assert_ct_all_different!($($tok,)*);
    };
}

macro_rules! make_translation_macro {
    ($name:ident : $($original:literal => $translation:literal),*) => {
        make_translation_macro!($name : $($original => $translation,)*);
    };
    ($name:ident : $($original:literal => $translation:literal,)*) => {
        assert_ct_all_different_literals!($($original,)*);
        macro_rules! $name {
            $(($original) => { $translation };)*
        }
    }
}

make_translation_macro!(tr:
    "foo" => "фу",
    "bar" => "бар"
);

const _: &str = tr!("foo");