syntax_data: {"ast_node_type":"other","tokens":[{"end":23,"kind":"keyword","start":0,"text":"#[allow(dead_code)]"}]}
source_snippet:     #[allow(dead_code)]
context_before:     /// A `Tree` whose layout matches `std::num::NonZeroXxx`.
context_after:     pub(crate) fn nonzero(width_in_bytes: u64) -> Self {