{"ast_node_type":"other","tokens":[{"end":68,"kind":"keyword","start":0,"text":"//"}]}
        // See the comment in `coroutine_datum()` for unknown types.
        let InternedCoroutine(parent, _) = self.db.lookup_intern_coroutine(id.into());
        let subst = TyBuilder::subst_for_coroutine(self.db, parent).fill_with_unknown().build();