Macro string_enum

macro_rules! string_enum {
    ($name:ident, $repr:ident, [$($case:ident => $str:literal),+]) => { ... };
    ($name:ident,
     $repr:ident,
     [$($case:ident => $str:literal),+],
     [$($altcase:ident => $altstr:literal),*]) => { ... };
}