syntax_data: {"ast_node_type":"other","tokens":[{"end":90,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 // Never allowed today, but we still encounter them in invalid const args.
context_before:             (_, ty::FnDef(def_id, args)) => {
context_after:                 self.print_value_path(def_id, args)?;