diff options
| -rw-r--r-- | compiler/typecheck/TcTypeable.hs | 55 | ||||
| -rw-r--r-- | compiler/types/TyCon.hs | 5 | ||||
| -rw-r--r-- | libraries/ghc-prim/GHC/Types.hs | 2 |
3 files changed, 35 insertions, 27 deletions
diff --git a/compiler/typecheck/TcTypeable.hs b/compiler/typecheck/TcTypeable.hs index d30a722933..4c6076e7d4 100644 --- a/compiler/typecheck/TcTypeable.hs +++ b/compiler/typecheck/TcTypeable.hs @@ -72,7 +72,7 @@ The overall plan is this: Here 0# is the number of arguments expected by the tycon to fully determine its kind. kind_rep is a value of type GHC.Types.KindRep, which gives a recipe for computing the kind of an instantiation of the tycon (see - Note [Representing TyCon kinds] later in this file for details). + Note [Representing TyCon kinds: KindRep] later in this file for details). We define (in TyCon) @@ -640,54 +640,59 @@ word64 dflags n | otherwise = HsWordPrim NoSourceText (toInteger n) {- -Note [Representing TyCon kinds] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - +Note [Representing TyCon kinds: KindRep] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ One of the operations supported by Typeable is typeRepKind, typeRepKind :: TypeRep (a :: k) -> TypeRep k -Implementing this is a bit tricky. To see why let's consider the TypeRep -encoding of `Proxy Int` where +Implementing this is a bit tricky for poly-kinded types like data Proxy (a :: k) :: Type + -- Proxy :: forall k. k -> Type -which looks like, +The TypeRep encoding of `Proxy Type Int` looks like this: - $tcProxy :: TyCon + $tcProxy :: GHC.Types.TyCon $trInt :: TypeRep Int $trType :: TypeRep Type - $trProxyType :: TypeRep (Proxy :: Type -> Type) + $trProxyType :: TypeRep (Proxy Type :: Type -> Type) $trProxyType = TrTyCon $tcProxy [$trType] -- kind variable instantiation - $trProxy :: TypeRep (Proxy Int) + $trProxy :: TypeRep (Proxy Type Int) $trProxy = TrApp $trProxyType $trInt -Note how $trProxyType encodes only the kind variables of the TyCon -instantiation. To compute the kind (Proxy Int) we need to have a recipe to -compute the kind of a concrete instantiation of Proxy. We call this recipe a -KindRep and store it in the TyCon produced for Proxy, + $tkProxy :: GHC.Types.KindRep + $tkProxy = KindRepFun (KindRepVar 0) (KindRepTyConApp $trType []) - type KindBndr = Int -- de Bruijn index +Note how $trProxyType cannot use 'TrApp', because TypeRep cannot represent +polymorphic types. So instead - data KindRep = KindRepTyConApp TyCon [KindRep] - | KindRepVar !KindBndr - | KindRepApp KindRep KindRep - | KindRepFun KindRep KindRep + * $trProxyType uses 'TrTyCon' to apply Proxy to (the representations) + of all its kind arguments. We can't represent a tycon that is + applied to only some of its kind arguments. -The KindRep for Proxy would look like, + * In $tcProxy, the GHC.Types.TyCon structure for Proxy, we store a + GHC.Types.KindRep, which represents the polymorphic kind of Proxy + Proxy :: forall k. k->Type - $tkProxy :: KindRep - $tkProxy = KindRepFun (KindRepVar 0) (KindRepTyConApp $trType []) + * A KindRep is just a recipe that we can instantiate with the + argument kinds, using Data.Typeable.Internal.instantiateKindRep. + Data.Typeable.Internal.typeRepKind uses instantiateKindRep -data Maybe a = Nothing | Just a + * In a KindRep, the kind variables are represented by 0-indexed + de Bruijn numbers: -'Just :: a -> Maybe a + type KindBndr = Int -- de Bruijn index -F :: forall k. k -> forall k'. k' -> Type + data KindRep = KindRepTyConApp TyCon [KindRep] + | KindRepVar !KindBndr + | KindRepApp KindRep KindRep + | KindRepFun KindRep KindRep + ... -} mkList :: Type -> [LHsExpr Id] -> LHsExpr Id diff --git a/compiler/types/TyCon.hs b/compiler/types/TyCon.hs index 99a20af1f1..9f6486b182 100644 --- a/compiler/types/TyCon.hs +++ b/compiler/types/TyCon.hs @@ -403,6 +403,9 @@ tyConBinderArgFlag (TvBndr _ (NamedTCB vis)) = vis tyConBinderArgFlag (TvBndr _ AnonTCB) = Required isNamedTyConBinder :: TyConBinder -> Bool +-- Identifies kind variables +-- E.g. data T k (a:k) = blah +-- Here 'k' is a NamedTCB, a variable used in the kind of other binders isNamedTyConBinder (TvBndr _ (NamedTCB {})) = True isNamedTyConBinder _ = False @@ -427,7 +430,7 @@ mkTyConKind bndrs res_kind = foldr mk res_kind bndrs All TyCons have this group of fields tyConBinders :: [TyConBinder] tyConResKind :: Kind - tyConTyVars :: [TyVra] -- Cached = binderVars tyConBinders + tyConTyVars :: [TyVar] -- Cached = binderVars tyConBinders tyConKind :: Kind -- Cached = mkTyConKind tyConBinders tyConResKind tyConArity :: Arity -- Cached = length tyConBinders diff --git a/libraries/ghc-prim/GHC/Types.hs b/libraries/ghc-prim/GHC/Types.hs index a4b7a91b59..3756c58827 100644 --- a/libraries/ghc-prim/GHC/Types.hs +++ b/libraries/ghc-prim/GHC/Types.hs @@ -450,7 +450,7 @@ type KindBndr = Int #endif -- | The representation produced by GHC for conjuring up the kind of a --- 'TypeRep'. +-- 'TypeRep'. See Note [Representing TyCon kinds: KindRep] in TcTypeable. data KindRep = KindRepTyConApp TyCon [KindRep] | KindRepVar !KindBndr | KindRepApp KindRep KindRep |