@@ -525,7 +525,7 @@ isLikeNat ist cn
525525 , Just (z, s) <- natLikeCtors tyN cTy
526526 = if | cn == z -> Just LikeZ
527527 | cn == s -> Just LikeS
528− | otherwise -> Nothing
528+ | otherwise -> error $ "isLikeNat: constructor not found in its own family: " ++ show (cn, tyN)
529529 where
530530 natLikeCtors :: Name -> Type -> Maybe (Name, Name)
531531 natLikeCtors tyN cTy = case lookupCtxtExact tyN $ idris_datatypes ist of