syntax_data: {"ast_node_type":"other","tokens":[{"end":99,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 // so it makes sense to micro-optimize it to avoid `span.data()` and `Span::new()`.
context_before:                 // This format occurs 1-2 orders of magnitude more often than others (#126544),
context_after:                 // Copypaste from `Span::new`, the small len & ctxt conditions are known to hold.