Function nf_show_item 

#[unsafe(no_mangle)]
pub(crate) unsafe extern "C" fn nf_show_item(
    sink: *mut Sink<'_>,
    list: u32,
) -> *mut Slot

Shows the region’s list list with a copy of the region’s frame, and returns that copy’s locals for compiled code to fill in, as a for does for each item. They stay valid until the expansion returns.

Safety

sink is the sink the runtime passed into the compiled code calling.