Macro Shenanigans

test.rs

macro_rules! expected_variants_join {
  ($x:ident) => (stringify!($x));
  ($x:ident, $($y:ident),*) => { concat!(stringify!($x), " ", expected_variants!($($y),*)) };
}

macro_rules! expected_variants {
  ($x:ident) => { concat!("Expected: ", stringify!($x)) };
  ($x:ident, $($y:ident),*) => { concat!("Expected one of: ", stringify!($x), " ", expected_variants_join!($($y),*)) };
}

macro_rules! check_variants {
  ($v:expr, $($variant:ident),*) => {{
    let v = &($v).data.borrow().value;
    let is_match = $(matches!(v, NodeValue::$variant { .. })) || +;
    if !is_match { return Err(WranglerError::UnexpectedNodeType(concat!(expected_variants!($($variant),*)), format!("{:?}", v))) }
  }};
}

fn document<'a>(node: &'a AstNode<'a>) -> Result<(), WranglerError>  {
  check_variants!(node, Document);
  let node = node.data.borrow();
  Ok(())
}