Unable to newtype derive `Prim` via DerivingStrategies

The following compiles with both GHC 8.2.2 and 8.4.1:

newtype Drain = Drain { _drain :: Word8 }
  deriving stock    (Eq, Ord, Show, Generic)
  deriving newtype  (Storable)
  deriving anyclass (NFData)

However, adding Prim beside Storable in the newtype area yields the following with GHC 8.2.2:

/home/colin/code/haskell/mapalgebra/lib/Geography/MapAlgebra.hs:1148:21-24: error:
    • Illegal unboxed tuple type as function argument:
      (# ghc-prim-0.5.1.1:GHC.Prim.State# s1, Word8 #)
    • In the expression:
        ghc-prim-0.5.1.1:GHC.Prim.coerce
          @(forall (s :: TYPE ghc-prim-0.5.1.1:GHC.Types.LiftedRep).
            ghc-prim-0.5.1.1:GHC.Prim.MutableByteArray# s
            -> ghc-prim-0.5.1.1:GHC.Prim.Int#
               -> ghc-prim-0.5.1.1:GHC.Prim.State# s
                  -> (#,#) ghc-prim-0.5.1.1:GHC.Prim.State# s Word8)
          @(forall (s :: TYPE ghc-prim-0.5.1.1:GHC.Types.LiftedRep).
            ghc-prim-0.5.1.1:GHC.Prim.MutableByteArray# s
            -> ghc-prim-0.5.1.1:GHC.Prim.Int#
               -> ghc-prim-0.5.1.1:GHC.Prim.State# s
                  -> (#,#) ghc-prim-0.5.1.1:GHC.Prim.State# s Drain)
          primitive-0.6.3.0:Data.Primitive.Types.readByteArray#
      In an equation for ‘primitive-0.6.3.0:Data.Primitive.Types.readByteArray#’:
          primitive-0.6.3.0:Data.Primitive.Types.readByteArray#
            = ghc-prim-0.5.1.1:GHC.Prim.coerce
                @(forall (s :: TYPE ghc-prim-0.5.1.1:GHC.Types.LiftedRep).
                  ghc-prim-0.5.1.1:GHC.Prim.MutableByteArray# s
                  -> ghc-prim-0.5.1.1:GHC.Prim.Int#
                     -> ghc-prim-0.5.1.1:GHC.Prim.State# s
                        -> (#,#) ghc-prim-0.5.1.1:GHC.Prim.State# s Word8)
                @(forall (s :: TYPE ghc-prim-0.5.1.1:GHC.Types.LiftedRep).
                  ghc-prim-0.5.1.1:GHC.Prim.MutableByteArray# s
                  -> ghc-prim-0.5.1.1:GHC.Prim.Int#
                     -> ghc-prim-0.5.1.1:GHC.Prim.State# s
                        -> (#,#) ghc-prim-0.5.1.1:GHC.Prim.State# s Drain)

and this with GHC 8.4.1:

    Illegal kind: ((:) (ghc-prim-0.5.2.0:GHC.Types.TupleRep ([] :: [] ghc-prim-0.5.2.0:GHC.Types.RuntimeR
ep)) ((:) ghc-prim-0.5.2.0:GHC.Types.LiftedRep ([] :: [] ghc-prim-0.5.2.0:GHC.Types.RuntimeRep) :: [] 
ghc-prim-0.5.2.0:GHC.Types.RuntimeRep) :: [] ghc-prim-0.5.2.0:GHC.Types.RuntimeRep)
    Did you mean to enable TypeInType?
     |
1132 |   deriving newtype  (Storable, Prim)
     |                                

Turning on TypeInType as it suggests gives the same Illegal unboxed tuple... error.

I've hand-written Storable instances before so I'm confident in its derivation, but I otherwise know nothing about Prim. Is there something magical about it that prevents it from being newtype derived in the same way?

Thank you kindly,

Colin

Trac metadata

Trac field	Value
Version	8.2.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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