macro_rules! overly_complicated { {$fnname:ident, $arg:ident, $ty:ty, $body:block, $val:expr, $pat:pat, $res:path} => { fn $fnname($arg: $ty) -> option<$ty> $body match $fnname($val) { some($pat) => { $res } _ => { fail; } } } } fn main() { assert overly_complicated!(f, x, option, { return some(x); }, some(8u), some(y), y) == 8u }