test.rs

#![feature(macro_rules)]

use std::fmt;

trait Element {}

macro_rules! Elem(
	($name:ident { $($element:ident: $ty:ty),* }) => (
		struct $name {
			$(
				$element: $ty
			),*
		}
		impl $name {
			fn name() -> &'static str { stringify!($name) }
		}
		impl Element for $name {}
		impl fmt::Show for $name {
			fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
				write!(f, "<{0}/>", stringify!($name))
			}
		}
	);
	($name:ident $subname:ident[ $($child:ident),+ ] { $($element:ident: $ty:ty),* }) => (
		trait $subname: fmt::Show {}
		impl<'a> fmt::Show for Box<$subname + 'a> {
			fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
				write!(f, "{}", *self) //TODO: abc instead of [a,b,c]
			}
		}
		$(
			impl $subname for $child {}
		)+
		struct $name<'a> {
			children: Vec<Box<$subname + 'a>>,
			$(
				$element: $ty
			),*
		}
		impl<'a> $name<'a> {
			fn name() -> &'static str { stringify!($name) }
		}
		impl<'a> Element for $name<'a> {}
		impl<'a> fmt::Show for $name<'a> {
			fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
				write!(f, "<{0}>{1}</{0}>", stringify!($name), self.children)
			}
		}
	)
)

Elem!(Text { text: String })
Elem!(Header __SubHeader[Text] { })

fn main() {
	let mut h = Header { children: vec![] };
	h.children.push(box Text { text: "Hio".to_string() });
	println!("{}", h);
}