Macro route::seg

macro_rules! seg {
    ( $s:ident, $p:ident, $segment:tt ) => { ... };
    ( $s:ident, $p:ident, $end:ident, [_] ) => { ... };
    ( $s:ident, $p:ident, $end:ident, [ $n:ident ] ) => { ... };
    ( $s:ident, $p:ident, $end:ident, [ $n:ident : $t:ty ] ) => { ... };
    ( $s:ident, $p:ident, $end:ident, $e:expr ) => { ... };
}