// run-pass macro_rules! higher_order { (subst $lhs:tt => $rhs:tt) => ({ macro_rules! anon { $lhs => $rhs } anon!(1_usize, 2_usize, "foo") }); } macro_rules! outer { ($x:expr; $fragment:ident) => { macro_rules! inner { ($y:$fragment) => { $x + $y } } } } fn main() { let val = higher_order!(subst ($x:expr, $y:expr, $foo:expr) => (($x + $y, $foo))); assert_eq!(val, (3, "foo")); outer!(2; expr); assert_eq!(inner!(3), 5); }