{"ast_node_type":"other","tokens":[{"end":75,"kind":"keyword","start":0,"text":"(None,"}]}
                (None, Some(t_cast)) => match self.expr_ty.kind(Interner) {
                (Some(t_from), Some(t_cast)) => (t_from, t_cast),
                    TyKind::FnDef(..) => {