Macro span

macro_rules! span {
    ($guard_name:tt, $level:ident, $name:expr, $($fields:tt)*) => { ... };
    ($guard_name:tt, $level:ident, $name:expr) => { ... };
    ($guard_name:tt, $name:expr) => { ... };
    ($guard_name:tt, $no_tracy_name:expr, $tracy_name:expr) => { ... };
}