#15073: Unable to newtype derive `Prim` via DerivingStrategies -------------------------------------+------------------------------------- Reporter: fosskers | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: None/Unknown (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following compiles with both GHC 8.2.2 and 8.4.1: {{{#!hs 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 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15073 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler