syntax_data: {"ast_node_type":"other","tokens":[{"end":3,"kind":"keyword","start":0,"text":"///"}]}
source_snippet: ///
context_before: /// - `span.ctxt_or_parent_or_marker == span_data.ctxt` (must be `<= MAX_CTXT`)
context_after: /// Fully-interned format (all cases not covered above):