Repository : ssh://darcs.haskell.org//srv/darcs/ghc On branch : ghc-7.6
http://hackage.haskell.org/trac/ghc/changeset/e3dc71de7307d30f6063a8447b93e54f1551a041 >--------------------------------------------------------------- commit e3dc71de7307d30f6063a8447b93e54f1551a041 Author: Simon Peyton Jones <simo...@microsoft.com> Date: Wed Dec 5 11:07:38 2012 +0000 Allow existential data constructors to be promoted This reverts the change in Trac #7347, which prevented promotion of existential data constructors. Ones with constraints in their types, or kind polymorphism, still can't be promoted. >--------------------------------------------------------------- compiler/basicTypes/DataCon.lhs | 8 +++++--- compiler/types/TyCon.lhs | 6 ++++-- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/compiler/basicTypes/DataCon.lhs b/compiler/basicTypes/DataCon.lhs index c82f018..edb3627 100644 --- a/compiler/basicTypes/DataCon.lhs +++ b/compiler/basicTypes/DataCon.lhs @@ -391,6 +391,7 @@ data DataCon -- The actual fixity is stored elsewhere dcPromoted :: Maybe TyCon -- The promoted TyCon if this DataCon is promotable + -- See Note [Promoted data constructors] in TyCon } deriving Data.Typeable.Typeable @@ -559,9 +560,10 @@ mkDataCon name declared_infix mkFunTys rep_arg_tys $ mkTyConApp rep_tycon (mkTyVarTys univ_tvs) - mb_promoted - | is_vanilla -- No existentials or context - , all (isLiftedTypeKind . tyVarKind) univ_tvs + mb_promoted -- See Note [Promoted data constructors] in TyCon + | all (isLiftedTypeKind . tyVarKind) (univ_tvs ++ ex_tvs) + -- No kind polymorphism, and all of kind * + , null full_theta -- No constraints , all isPromotableType orig_arg_tys = Just (mkPromotedDataCon con name (getUnique name) prom_kind arity) | otherwise diff --git a/compiler/types/TyCon.lhs b/compiler/types/TyCon.lhs index 5398adc..e90cdec 100644 --- a/compiler/types/TyCon.lhs +++ b/compiler/types/TyCon.lhs @@ -581,8 +581,10 @@ Note [Promoted data constructors] A data constructor can be promoted to become a type constructor, via the PromotedTyCon alternative in TyCon. -* Only "vanilla" data constructors are promoted; ones with no GADT - stuff, no existentials, etc. We might generalise this later. +* Only data constructors with + (a) no kind polymorphism + (b) no constraints in its type (eg GADTs) + are promoted. Existentials are ok; see Trac #7347. * The TyCon promoted from a DataCon has the *same* Name and Unique as the DataCon. Eg. If the data constructor Data.Maybe.Just(unique 78, _______________________________________________ Cvs-ghc mailing list Cvs-ghc@haskell.org http://www.haskell.org/mailman/listinfo/cvs-ghc
