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 }