{"ast_node_type":"variable","tokens":[{"end":70,"kind":"keyword","start":0,"text":"let"}]}
    let InternedClosure(owner, _) = db.lookup_intern_closure(closure);
) -> Result<Arc<MirBody>, MirLowerError> {
    let generics = owner.as_generic_def_id(db).map(|g_def| generics(db, g_def));