{"ast_node_type":"variable","tokens":[{"end":74,"kind":"keyword","start":0,"text":"let"}]}
                let inner_tys = inner.iter().map(|&tr| self.lower_ty(tr));
            TypeRef::Tuple(inner) => {
                TyKind::Tuple(inner_tys.len(), Substitution::from_iter(Interner, inner_tys))