-ddump-splices prints ParensT/HsArgPar poorly

If you compile this program:

{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
{-# OPTIONS_GHC -ddump-splices #-}
module Bug where

import Language.Haskell.TH

type family T a

$(pure [TySynInstD (TySynEqn Nothing (ParensT (ConT ''T) `AppT` ConT ''Int) (ConT ''Int))])

Then -ddump-splices will print this:

$ /opt/ghc/9.0.1/bin/ghc Bug.hs
[1 of 1] Compiling Bug              ( Bug.hs, Bug.o, Bug.dyn_o )
Bug.hs:10:2-91: Splicing declarations
    pure
      [TySynInstD
         (TySynEqn
            Nothing (ParensT (ConT ''T) `AppT` ConT ''Int) (ConT ''Int))]
  ======>
    type instance T HsArgPar Bug.hs:10:2-91 Int = Int

In particular, notice that the type family instance is printed as type instance T HsArgPar Bug.hs:10:2-91 Int = Int rather than type instance (T) Int = Int. This happens because pprHsFamInstLHS uses the Outputable instance for HsArg to pretty-print the types on the left-hand side:

nstance (Outputable tm, Outputable ty) => Outputable (HsArg tm ty) where
  ppr (HsValArg tm)    = ppr tm
  ppr (HsTypeArg _ ty) = char '@' <> ppr ty
  ppr (HsArgPar sp)    = text "HsArgPar"  <+> ppr sp

Most likely, we'll need to avoid using this Outputable instance when pretty-printing Haskell code, such as what -ddump-splices does.