Deriving Eq1 via Generically1 doesn't work and never did

Summary

There's following instance for Generically1 (perhaps originally taken from the generic-data package)

(Generic1 f, Eq1 (Rep1 f)) => Eq1 (Generically1 f)

The constraint Eq1 (Rep1 f) is not satisfiable and never was because auxiliary Generics types like M1 (aka D1 in the error below) don't have Eq1 instance.

NB The same applies to Ord1. Also there's no Show1 instance for Generically1.

Steps to reproduce

Take following program

#!/usr/bin/env cabal
{- cabal:
build-depends:
  , base
default-language:
  Haskell2010
ghc-options:
  -main-is Test
-}

{-# LANGUAGE DeriveGeneric    #-}
{-# LANGUAGE DerivingVia      #-}
{-# LANGUAGE TypeApplications #-}

module Test (main) where

import Data.Functor.Classes
import GHC.Generics (Generic1, Generically1(..))

data I a = I [a] (Maybe a)
  deriving stock (Eq, Ord, Show, Generic1)
  deriving (Eq1) via (Generically1 I)

main :: IO ()
main = do
  let x = I @Int [1, 2] (Just 3)
      y = I @Int [] Nothing
  putStrLn $ show $ eq1 x y
  pure ()

And run it under GHC:

$ cabal run ./Test.hs 
Created semaphore called cabal_semaphore_f with 32 slots.

/tmp/Test.hs:22:13: error: [GHC-39999]
    • No instance for ‘Eq1
                         (GHC.Generics.D1
                            (GHC.Generics.MetaData
                               "I" "Test" "fake-package-0-inplace-script-Test.hs" False)
                            (GHC.Generics.C1
                               (GHC.Generics.MetaCons "I" GHC.Generics.PrefixI False)
                               (GHC.Generics.S1
                                  (GHC.Generics.MetaSel
                                     Nothing
                                     GHC.Generics.NoSourceUnpackedness
                                     GHC.Generics.NoSourceStrictness
                                     GHC.Generics.DecidedLazy)
                                  (GHC.Generics.Rec1 [])
                                GHC.Generics.:*: GHC.Generics.S1
                                                   (GHC.Generics.MetaSel
                                                      Nothing
                                                      GHC.Generics.NoSourceUnpackedness
                                                      GHC.Generics.NoSourceStrictness
                                                      GHC.Generics.DecidedLazy)
                                                   (GHC.Generics.Rec1 Maybe))))’
        arising from the 'deriving' clause of a data type declaration
      Possible fix:
        use a standalone 'deriving instance' declaration,
          so you can specify the instance context yourself
    • When deriving the instance for (Eq1 I)
   |
22 |   deriving (Eq1) via (Generically1 I)
   |             ^^^

Expected behavior

Print False, generally derive the Eq1 instance without errors.

Probably either the Eq1 instance for Generically1 should be removed since it doesn't work and never did or *1 instances for M1 and the rest should be added.

Environment

• GHC version used: 9.8, 9.6, 9.4, 9.2, 8.10

Optional:

• Operating System: Linux
• System Architecture: x86_64