syntax_data: {"ast_node_type":"other","tokens":[{"end":54,"kind":"keyword","start":0,"text":"///"}]}
source_snippet: ///   is rather hackily encoded via a scalar type. See
context_before: /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
context_after: ///   `Ty::to_opt_closure_kind` for details.