{"ast_node_type":"other","tokens":[{"end":91,"kind":"keyword","start":0,"text":"///"}]}
/// subdiagnostic derive refers to typed identifiers that are `DiagMessage`s, so need to be
/// the subdiagnostic functions (e.g. `span_label`) take a `SubdiagMessage` and the
/// able to convert between these, as much as they'll be converted back into `DiagMessage`