[GHC] #7347: Existential data constructors should not be promoted

[GHC]

#7347: Existential data constructors should not be promoted
---------------------------------+------------------------------------------
    Reporter:  simonpj           |       Owner:                  
        Type:  bug               |      Status:  merge           
    Priority:  normal            |   Milestone:                  
   Component:  Compiler          |     Version:  7.6.1           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:  polykinds/T7347 
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by simonpj):

 Also needs this:
 {{{
 commit 1152f9491517ca22ed796bfacbbfb7413dde1bcf
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Fri Oct 19 20:29:06 2012 +0100

     An accidentally-omitted part of commit 8019bc2c, about promoting data
 constructors

 >---------------------------------------------------------------

  compiler/typecheck/TcHsType.lhs |   14 ++++++--------
  1 files changed, 6 insertions(+), 8 deletions(-)

 diff --git a/compiler/typecheck/TcHsType.lhs
 b/compiler/typecheck/TcHsType.lhs index bbfc673..60cf544 100644
 --- a/compiler/typecheck/TcHsType.lhs
 +++ b/compiler/typecheck/TcHsType.lhs
 @@ -427,8 +427,8 @@ tc_hs_type hs_ty@(HsExplicitListTy _k tys) exp_kind
         ; checkExpectedKind hs_ty (mkPromotedListTy kind) exp_kind
         ; return (foldr (mk_cons kind) (mk_nil kind) taus) }
    where
 -    mk_cons k a b = mkTyConApp (buildPromotedDataCon consDataCon) [k, a,
 b]
 -    mk_nil  k     = mkTyConApp (buildPromotedDataCon nilDataCon) [k]
 +    mk_cons k a b = mkTyConApp (promoteDataCon consDataCon) [k, a, b]
 +    mk_nil  k     = mkTyConApp (promoteDataCon nilDataCon) [k]

  tc_hs_type hs_ty@(HsExplicitTupleTy _ tys) exp_kind
    = do { tks <- mapM tc_infer_lhs_type tys
 @@ -607,12 +607,10 @@ tcTyVar name         -- Could be a tyvar, a tycon,
 or a datacon
             AGlobal (ATyCon tc) -> inst_tycon (mkTyConApp tc) (tyConKind
 tc)

             AGlobal (ADataCon dc)
 -             | isPromotableType ty -> inst_tycon (mkTyConApp tc)
 (tyConKind tc)
 +             | Just tc <- promoteDataCon_maybe dc
 +             -> inst_tycon (mkTyConApp tc) (tyConKind tc)
               | otherwise -> failWithTc (quotes (ppr dc) <+> ptext (sLit
 "of type")
 -                            <+> quotes (ppr ty) <+> ptext (sLit "is not
 promotable"))
 -             where
 -               ty = dataConUserType dc
 -               tc = buildPromotedDataCon dc
 +                            <+> quotes (ppr (dataConUserType dc)) <+>
 + ptext (sLit "is not promotable"))

             APromotionErr err -> promotionErr name err

 @@ -1465,7 +1463,7 @@ tc_kind_var_app name arg_kis
                    ; unless data_kinds $ addErr (dataKindsErr name)
                    ; case isPromotableTyCon tc of
                        Just n | n == length arg_kis ->
 -                        return (mkTyConApp (buildPromotedTyCon tc)
 arg_kis)
 +                        return (mkTyConApp (promoteTyCon tc) arg_kis)
                        Just _  -> tycon_err tc "is not fully applied"
                        Nothing -> tycon_err tc "is not promotable" }
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7347#comment:10>
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