Out of scope with `-dcore-lint` and derived instances in GHCi

At revision 9e2e84e0 (current HEAD), I observe this failure:

$ ./inplace/bin/ghc-stage2 --interactive 
GHCi, version 7.7.20130902: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> newtype Age = Age Int deriving Show
Prelude> newtype Bar = Bar Age deriving Show
Prelude> Bar (Age 1))

<interactive>:4:12: parse error on input `)'
Prelude> Bar (Age 1)
Bar (Age 1)
Prelude> 
Leaving GHCi.
[jojo@kirk:3] Mo, der 02.09.2013 um 16:47 Uhr Keep Smiling :-)
~/build/haskell/ghc $ ./inplace/bin/ghc-stage2 --interactive -dcore-lint
GHCi, version 7.7.20130902: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> newtype Age = Age Int deriving Show
Prelude> newtype Bar = Bar Age deriving Show
*** Core Lint errors : in result of Desugar (after optimization) ***
<no location info>: Warning:
    In the expression: GHC.Show.showsPrec
                         @ :Interactive.Age
                         :Interactive.$fShowAge
                         (GHC.Types.I# 11)
                         (ds_dq3
                          `cast` (:Interactive.NTCo:Bar[0]
                                  :: :Interactive.Bar ~# :Interactive.Age))
    :Interactive.$fShowAge :: GHC.Show.Show :Interactive.Age
    [LclIdX[DFunId], Str=DmdType] is out of scope
*** Offending Program ***
Rec {
$cshowsPrec_apH
  :: GHC.Types.Int -> :Interactive.Bar -> GHC.Show.ShowS
[LclId, Str=DmdType]
$cshowsPrec_apH =
  \ (a_apF :: GHC.Types.Int) (ds_dq3 :: :Interactive.Bar) ->
    GHC.Show.showParen
      (GHC.Classes.>=
         @ GHC.Types.Int GHC.Classes.$fOrdInt a_apF (GHC.Types.I# 11))
      (GHC.Base..
         @ GHC.Base.String
         @ GHC.Base.String
         @ GHC.Base.String
         (GHC.Show.showString (GHC.CString.unpackCString# "Bar "#))
         (GHC.Show.showsPrec
            @ :Interactive.Age
            :Interactive.$fShowAge
            (GHC.Types.I# 11)
            (ds_dq3
             `cast` (:Interactive.NTCo:Bar[0]
                     :: :Interactive.Bar ~# :Interactive.Age))))

:Interactive.$fShowBar [InlPrag=[ALWAYS] CONLIKE]
  :: GHC.Show.Show :Interactive.Bar
[LclIdX[DFunId],
 Str=DmdType,
 Unf=DFun: \ ->
       GHC.Show.D:Show TYPE :Interactive.Bar
                       $cshowsPrec_apH
                       $cshow_apS
                       $cshowList_apU]
:Interactive.$fShowBar =
  GHC.Show.D:Show
    @ :Interactive.Bar $cshowsPrec_apH $cshow_apS $cshowList_apU

$cshowList_apU [Occ=LoopBreaker]
  :: [:Interactive.Bar] -> GHC.Show.ShowS
[LclId, Str=DmdType]
$cshowList_apU =
  GHC.Show.showList__
    @ :Interactive.Bar
    (GHC.Show.showsPrec
       @ :Interactive.Bar :Interactive.$fShowBar (GHC.Types.I# 0))

$cshow_apS [Occ=LoopBreaker] :: :Interactive.Bar -> GHC.Base.String
[LclId, Str=DmdType]
$cshow_apS =
  GHC.Show.$dmshow @ :Interactive.Bar :Interactive.$fShowBar
end Rec }

*** End of Offense ***


<no location info>: 
Compilation had errors


*** Exception: ExitFailure 1

I do not observe this in GHC.

I’ll write a test case for this.

Trac metadata

Trac field	Value
Version	7.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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