Shared via Rust Playground

playground.rs

// due to Enamex on #rust

macro_rules! overload {
    ( $trait_name:ident ($($args:ident : $typs:ty),+) => $( fn $fn_name:ident -> $ret:ty => $body:block );+ ) => {
        overload!(INTERNAL:DUPLICATE $trait_name ( ($($args),+) ($($args),+) : ($($typs),+) ($($typs),+) ) => $( fn $fn_name -> $ret => $body );+ );
    };
    
    (INTERNAL:DUPLICATE $trait_name:ident ( $all_args:tt ($($args:ident),+) : $all_typs:tt ($($typs:ty),+) ) => $( fn $fn_name:ident -> $ret:ty => $body:block );+ ) =>
    
    {
        trait $trait_name {
            $(
                fn $fn_name (self) -> $ret;
            );+
        }
        
        impl $trait_name for ($($typs),+) {
            $(
                fn $fn_name(self) -> $ret {
                    let overload!(INTERNAL:EVAL_TUPLE $all_args) = self;
                    
                    $body
                }
            )+
        }
    };
    
    (INTERNAL:EVAL_TUPLE ($($a:ident),+)) => { ($($a),+) }
}


overload! {
    Trial1 (s: i32, ss: char) =>
        fn try_me -> char => {
            if s < 6 { ss } else { '💩' }
        }
}


fn main() {
    println!("Hello, world!");
    
    println!("{}", (42, '☃').try_me());
    println!("{}", (-42, '☃').try_me());
}