X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypes%2FType.lhs;h=872feb06f55763bbc15254171cdb7ad53898243b;hb=28a464a75e14cece5db40f2765a29348273ff2d2;hp=5b4aa54d9cdc652feddcb83e61162cb769c1d4eb;hpb=72af48cb2073cd6015942bb6cb713039b58b1b4a;p=ghc-hetmet.git diff --git a/ghc/compiler/types/Type.lhs b/ghc/compiler/types/Type.lhs index 5b4aa54..872feb0 100644 --- a/ghc/compiler/types/Type.lhs +++ b/ghc/compiler/types/Type.lhs @@ -1,326 +1,168 @@ % % (c) The GRASP/AQUA Project, Glasgow University, 1998 % -\section[Type]{Type} +\section[Type]{Type - public interface} \begin{code} module Type ( - Type(..), TyNote(..), UsageAnn(..), -- Representation visible to friends - Kind, TyVarSubst, - - superKind, superBoxity, -- :: SuperKind - - boxedKind, -- :: Kind :: BX - anyBoxKind, -- :: Kind :: BX - typeCon, -- :: KindCon :: BX -> KX - anyBoxCon, -- :: KindCon :: BX - - boxedTypeKind, unboxedTypeKind, openTypeKind, -- Kind :: superKind + -- re-exports from TypeRep + TyThing(..), Type, PredType(..), ThetaType, + funTyCon, - mkArrowKind, mkArrowKinds, hasMoreBoxityInfo, + -- Re-exports from Kind + module Kind, - funTyCon, + -- Re-exports from TyCon + PrimRep(..), mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy, mkAppTy, mkAppTys, splitAppTy, splitAppTys, splitAppTy_maybe, - mkFunTy, mkFunTys, splitFunTy_maybe, splitFunTys, splitFunTysN, - funResultTy, funArgTy, - zipFunTys, + mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe, + splitFunTys, splitFunTysN, + funResultTy, funArgTy, zipFunTys, isFunTy, - mkTyConApp, mkTyConTy, splitTyConApp_maybe, - splitAlgTyConApp_maybe, splitAlgTyConApp, - mkDictTy, splitDictTy_maybe, isDictTy, + mkTyConApp, mkTyConTy, + tyConAppTyCon, tyConAppArgs, + splitTyConApp_maybe, splitTyConApp, - mkSynTy, isSynTy, deNoteType, repType, splitNewType_maybe, - - mkUsgTy, isUsgTy{- dont use -}, isNotUsgTy, splitUsgTy, unUsgTy, tyUsg, + repType, typePrimRep, coreView, tcView, mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys, - isForAllTy, applyTy, applyTys, mkPiType, + applyTy, applyTys, isForAllTy, dropForAlls, + + -- Source types + predTypeRep, mkPredTy, mkPredTys, - TauType, RhoType, SigmaType, ThetaType, - isTauTy, - mkRhoTy, splitRhoTy, - mkSigmaTy, splitSigmaTy, + -- Newtypes + splitRecNewType_maybe, -- Lifting and boxity - isUnLiftedType, isUnboxedType, isUnboxedTupleType, isAlgType, isDataType, isNewType, - typePrimRep, + isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType, + isStrictType, isStrictPred, -- Free variables - tyVarsOfType, tyVarsOfTypes, namesOfType, typeKind, - addFreeTyVars, + tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta, + typeKind, addFreeTyVars, -- Tidying up for printing - tidyType, tidyTypes, - tidyOpenType, tidyOpenTypes, - tidyTyVar, tidyTyVars, - tidyTopType, + tidyType, tidyTypes, + tidyOpenType, tidyOpenTypes, + tidyTyVarBndr, tidyFreeTyVars, + tidyOpenTyVar, tidyOpenTyVars, + tidyTopType, tidyPred, + tidyKind, - -- Seq - seqType, seqTypes + -- Comparison + coreEqType, tcEqType, tcEqTypes, tcCmpType, tcCmpTypes, + tcEqPred, tcCmpPred, tcEqTypeX, + -- Seq + seqType, seqTypes, + + -- Type substitutions + TvSubstEnv, emptyTvSubstEnv, -- Representation widely visible + TvSubst(..), emptyTvSubst, -- Representation visible to a few friends + mkTvSubst, mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst, + getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, + extendTvSubst, extendTvSubstList, isInScope, composeTvSubst, zipTyEnv, + + -- Performing substitution on types + substTy, substTys, substTyWith, substTheta, + substPred, substTyVar, substTyVarBndr, deShadowTy, lookupTyVar, + + -- Pretty-printing + pprType, pprParendType, pprTyThingCategory, + pprPred, pprTheta, pprThetaArrow, pprClassPred ) where #include "HsVersions.h" -import {-# SOURCE #-} DataCon( DataCon, dataConType ) -import {-# SOURCE #-} PprType( pprType ) -- Only called in debug messages -import {-# SOURCE #-} Subst ( mkTyVarSubst, substTy ) +-- We import the representation and primitive functions from TypeRep. +-- Many things are reexported, but not the representation! + +import TypeRep -- friends: -import Var ( Id, TyVar, IdOrTyVar, UVar, - tyVarKind, tyVarName, isId, idType, setTyVarName, setVarOcc - ) +import Kind +import Var ( Var, TyVar, tyVarKind, tyVarName, setTyVarName, mkTyVar ) import VarEnv import VarSet -import Name ( NamedThing(..), Provenance(..), ExportFlag(..), - mkWiredInTyConName, mkGlobalName, mkLocalName, mkKindOccFS, tcName, - tidyOccName, TidyOccEnv - ) -import NameSet -import Class ( classTyCon, Class ) -import TyCon ( TyCon, KindCon, - mkFunTyCon, mkKindCon, mkSuperKindCon, - matchesTyCon, isUnboxedTupleTyCon, isUnLiftedTyCon, - isFunTyCon, isDataTyCon, isNewTyCon, - isAlgTyCon, isSynTyCon, tyConArity, - tyConKind, tyConDataCons, getSynTyConDefn, - tyConPrimRep, tyConClass_maybe +import OccName ( tidyOccName ) +import Name ( NamedThing(..), mkInternalName, tidyNameOcc ) +import Class ( Class, classTyCon ) +import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon, + isUnboxedTupleTyCon, isUnLiftedTyCon, + isFunTyCon, isNewTyCon, newTyConRep, newTyConRhs, + isAlgTyCon, tyConArity, + tcExpandTyCon_maybe, coreExpandTyCon_maybe, + tyConKind, PrimRep(..), tyConPrimRep, ) -- others -import BasicTypes ( Unused ) -import SrcLoc ( mkBuiltinSrcLoc, noSrcLoc ) -import PrelMods ( pREL_GHC ) -import Maybes ( maybeToBool ) -import PrimRep ( PrimRep(..), isFollowableRep ) -import Unique -- quite a few *Keys -import Util ( thenCmp, mapAccumL, seqList, ($!) ) +import StaticFlags ( opt_DictsStrict ) +import SrcLoc ( noSrcLoc ) +import Util ( mapAccumL, seqList, lengthIs, snocView, thenCmp, isEqual, all2 ) import Outputable import UniqSet ( sizeUniqSet ) -- Should come via VarSet +import Maybe ( isJust ) \end{code} -%************************************************************************ -%* * -\subsection{Type Classifications} -%* * -%************************************************************************ - -A type is - - *unboxed* iff its representation is other than a pointer - Unboxed types cannot instantiate a type variable. - Unboxed types are always unlifted. - - *lifted* A type is lifted iff it has bottom as an element. - Closures always have lifted types: i.e. any - let-bound identifier in Core must have a lifted - type. Operationally, a lifted object is one that - can be entered. - (NOTE: previously "pointed"). - - *algebraic* A type with one or more constructors, whether declared - with "data" or "newtype". - An algebraic type is one that can be deconstructed - with a case expression. - *NOT* the same as lifted types, because we also - include unboxed tuples in this classification. - - *data* A type declared with "data". Also boxed tuples. - - *primitive* iff it is a built-in type that can't be expressed - in Haskell. - -Currently, all primitive types are unlifted, but that's not necessarily -the case. (E.g. Int could be primitive.) - -Some primitive types are unboxed, such as Int#, whereas some are boxed -but unlifted (such as ByteArray#). The only primitive types that we -classify as algebraic are the unboxed tuples. - -examples of type classifications: - -Type primitive boxed lifted algebraic ------------------------------------------------------------------------------ -Int#, Yes No No No -ByteArray# Yes Yes No No -(# a, b #) Yes No No Yes -( a, b ) No Yes Yes Yes -[a] No Yes Yes Yes %************************************************************************ %* * -\subsection{The data type} + Type representation %* * %************************************************************************ +In Core, we "look through" non-recursive newtypes and PredTypes. \begin{code} -type SuperKind = Type -type Kind = Type - -type TyVarSubst = TyVarEnv Type - -data Type - = TyVarTy TyVar - - | AppTy - Type -- Function is *not* a TyConApp - Type - - | TyConApp -- Application of a TyCon - TyCon -- *Invariant* saturated appliations of FunTyCon and - -- synonyms have their own constructors, below. - [Type] -- Might not be saturated. - - | FunTy -- Special case of TyConApp: TyConApp FunTyCon [t1,t2] - Type - Type - - | NoteTy -- Saturated application of a type synonym - TyNote - Type -- The expanded version - - | ForAllTy - TyVar - Type -- TypeKind - -data TyNote - = SynNote Type -- The unexpanded version of the type synonym; always a TyConApp - | FTVNote TyVarSet -- The free type variables of the noted expression - | UsgNote UsageAnn -- The usage annotation at this node - -data UsageAnn - = UsOnce -- Used at most once - | UsMany -- Used possibly many times (no info; this annotation can be omitted) - | UsVar UVar -- Annotation is variable (should only happen inside analysis) +{-# INLINE coreView #-} +coreView :: Type -> Maybe Type +-- Srips off the *top layer only* of a type to give +-- its underlying representation type. +-- Returns Nothing if there is nothing to look through. +-- +-- In the case of newtypes, it returns +-- *either* a vanilla TyConApp (recursive newtype, or non-saturated) +-- *or* the newtype representation (otherwise), meaning the +-- type written in the RHS of the newtype decl, +-- which may itself be a newtype +-- +-- Example: newtype R = MkR S +-- newtype S = MkS T +-- newtype T = MkT (T -> T) +-- expandNewTcApp on R gives Just S +-- on S gives Just T +-- on T gives Nothing (no expansion) + +-- By being non-recursive and inlined, this case analysis gets efficiently +-- joined onto the case analysis that the caller is already doing +coreView (NoteTy _ ty) = Just ty +coreView (PredTy p) = Just (predTypeRep p) +coreView (TyConApp tc tys) | Just (tenv, rhs, tys') <- coreExpandTyCon_maybe tc tys + = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys') + -- Its important to use mkAppTys, rather than (foldl AppTy), + -- because the function part might well return a + -- partially-applied type constructor; indeed, usually will! +coreView ty = Nothing + +----------------------------------------------- +{-# INLINE tcView #-} +tcView :: Type -> Maybe Type +-- Same, but for the type checker, which just looks through synonyms +tcView (NoteTy _ ty) = Just ty +tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- tcExpandTyCon_maybe tc tys + = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys') +tcView ty = Nothing \end{code} %************************************************************************ %* * -\subsection{Kinds} -%* * -%************************************************************************ - -Kinds -~~~~~ -k::K = Type bx - | k -> k - | kv - -kv :: KX is a kind variable - -Type :: BX -> KX - -bx::BX = Boxed - | Unboxed - | AnyBox -- Used *only* for special built-in things - -- like error :: forall (a::*?). String -> a - -- Here, the 'a' can be instantiated to a boxed or - -- unboxed type. - | bv - -bxv :: BX is a boxity variable - -sk = KX -- A kind - | BX -- A boxity - | sk -> sk -- In ptic (BX -> KX) - -\begin{code} -mk_kind_name key str = mkGlobalName key pREL_GHC (mkKindOccFS tcName str) - (LocalDef mkBuiltinSrcLoc NotExported) - -- mk_kind_name is a bit of a hack - -- The LocalDef means that we print the name without - -- a qualifier, which is what we want for these kinds. - -- It's used for both Kinds and Boxities -\end{code} - -Define KX, BX. - -\begin{code} -superKind :: SuperKind -- KX, the type of all kinds -superKindName = mk_kind_name kindConKey SLIT("KX") -superKind = TyConApp (mkSuperKindCon superKindName) [] - -superBoxity :: SuperKind -- BX, the type of all boxities -superBoxityName = mk_kind_name boxityConKey SLIT("BX") -superBoxity = TyConApp (mkSuperKindCon superBoxityName) [] -\end{code} - -Define Boxed, Unboxed, AnyBox - -\begin{code} -boxedKind, unboxedKind, anyBoxKind :: Kind -- Of superkind superBoxity - -boxedConName = mk_kind_name boxedConKey SLIT("*") -boxedKind = TyConApp (mkKindCon boxedConName superBoxity) [] - -unboxedConName = mk_kind_name unboxedConKey SLIT("#") -unboxedKind = TyConApp (mkKindCon unboxedConName superBoxity) [] - -anyBoxConName = mk_kind_name anyBoxConKey SLIT("?") -anyBoxCon = mkKindCon anyBoxConName superBoxity -- A kind of wild card -anyBoxKind = TyConApp anyBoxCon [] -\end{code} - -Define Type - -\begin{code} -typeCon :: KindCon -typeConName = mk_kind_name typeConKey SLIT("Type") -typeCon = mkKindCon typeConName (superBoxity `FunTy` superKind) -\end{code} - -Define (Type Boxed), (Type Unboxed), (Type AnyBox) - -\begin{code} -boxedTypeKind, unboxedTypeKind, openTypeKind :: Kind -boxedTypeKind = TyConApp typeCon [boxedKind] -unboxedTypeKind = TyConApp typeCon [unboxedKind] -openTypeKind = TyConApp typeCon [anyBoxKind] - -mkArrowKind :: Kind -> Kind -> Kind -mkArrowKind k1 k2 = k1 `FunTy` k2 - -mkArrowKinds :: [Kind] -> Kind -> Kind -mkArrowKinds arg_kinds result_kind = foldr mkArrowKind result_kind arg_kinds -\end{code} - -\begin{code} -hasMoreBoxityInfo :: Kind -> Kind -> Bool -hasMoreBoxityInfo k1 k2 - | k2 == openTypeKind = ASSERT( is_type_kind k1) True - | otherwise = k1 == k2 - where - -- Returns true for things of form (Type x) - is_type_kind k = case splitTyConApp_maybe k of - Just (tc,[_]) -> tc == typeCon - Nothing -> False -\end{code} - - -%************************************************************************ -%* * -\subsection{Wired-in type constructors -%* * -%************************************************************************ - -We define a few wired-in type constructors here to avoid module knots - -\begin{code} -funTyConName = mkWiredInTyConName funTyConKey pREL_GHC SLIT("(->)") funTyCon -funTyCon = mkFunTyCon funTyConName (mkArrowKinds [boxedTypeKind, boxedTypeKind] boxedTypeKind) -\end{code} - - - -%************************************************************************ -%* * \subsection{Constructor-specific functions} %* * %************************************************************************ @@ -337,19 +179,17 @@ mkTyVarTys :: [TyVar] -> [Type] mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy getTyVar :: String -> Type -> TyVar -getTyVar msg (TyVarTy tv) = tv -getTyVar msg (NoteTy _ t) = getTyVar msg t -getTyVar msg other = panic ("getTyVar: " ++ msg) - -getTyVar_maybe :: Type -> Maybe TyVar -getTyVar_maybe (TyVarTy tv) = Just tv -getTyVar_maybe (NoteTy _ t) = getTyVar_maybe t -getTyVar_maybe other = Nothing +getTyVar msg ty = case getTyVar_maybe ty of + Just tv -> tv + Nothing -> panic ("getTyVar: " ++ msg) isTyVarTy :: Type -> Bool -isTyVarTy (TyVarTy tv) = True -isTyVarTy (NoteTy _ ty) = isTyVarTy ty -isTyVarTy other = False +isTyVarTy ty = isJust (getTyVar_maybe ty) + +getTyVar_maybe :: Type -> Maybe TyVar +getTyVar_maybe ty | Just ty' <- coreView ty = getTyVar_maybe ty' +getTyVar_maybe (TyVarTy tv) = Just tv +getTyVar_maybe other = Nothing \end{code} @@ -361,39 +201,44 @@ invariant that a TyConApp is always visibly so. mkAppTy maintains the invariant: use it. \begin{code} -mkAppTy orig_ty1 orig_ty2 = ASSERT2( isNotUsgTy orig_ty1 && isNotUsgTy orig_ty2, pprType orig_ty1 <+> text "to" <+> pprType orig_ty2 ) - mk_app orig_ty1 +mkAppTy orig_ty1 orig_ty2 + = mk_app orig_ty1 where mk_app (NoteTy _ ty1) = mk_app ty1 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ [orig_ty2]) mk_app ty1 = AppTy orig_ty1 orig_ty2 + -- Note that the TyConApp could be an + -- under-saturated type synonym. GHC allows that; e.g. + -- type Foo k = k a -> k a + -- type Id x = x + -- foo :: Foo Id -> Foo Id + -- + -- Here Id is partially applied in the type sig for Foo, + -- but once the type synonyms are expanded all is well mkAppTys :: Type -> [Type] -> Type mkAppTys orig_ty1 [] = orig_ty1 -- This check for an empty list of type arguments - -- avoids the needless of a type synonym constructor. + -- avoids the needless loss of a type synonym constructor. -- For example: mkAppTys Rational [] -- returns to (Ratio Integer), which has needlessly lost -- the Rational part. -mkAppTys orig_ty1 orig_tys2 = ASSERT2( isNotUsgTy orig_ty1, pprType orig_ty1 ) - mk_app orig_ty1 +mkAppTys orig_ty1 orig_tys2 + = mk_app orig_ty1 where mk_app (NoteTy _ ty1) = mk_app ty1 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2) - mk_app ty1 = ASSERT2( all isNotUsgTy orig_tys2, pprType orig_ty1 <+> text "to" <+> hsep (map pprType orig_tys2) ) - foldl AppTy orig_ty1 orig_tys2 + -- mkTyConApp: see notes with mkAppTy + mk_app ty1 = foldl AppTy orig_ty1 orig_tys2 splitAppTy_maybe :: Type -> Maybe (Type, Type) +splitAppTy_maybe ty | Just ty' <- coreView ty = splitAppTy_maybe ty' splitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2) splitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2) -splitAppTy_maybe (NoteTy _ ty) = splitAppTy_maybe ty -splitAppTy_maybe (TyConApp tc []) = Nothing -splitAppTy_maybe (TyConApp tc tys) = split tys [] - where - split [ty2] acc = Just (TyConApp tc (reverse acc), ty2) - split (ty:tys) acc = split tys (ty:acc) - -splitAppTy_maybe other = Nothing +splitAppTy_maybe (TyConApp tc tys) = case snocView tys of + Nothing -> Nothing + Just (tys',ty') -> Just (TyConApp tc tys', ty') +splitAppTy_maybe other = Nothing splitAppTy :: Type -> (Type, Type) splitAppTy ty = case splitAppTy_maybe ty of @@ -403,11 +248,11 @@ splitAppTy ty = case splitAppTy_maybe ty of splitAppTys :: Type -> (Type, [Type]) splitAppTys ty = split ty ty [] where + split orig_ty ty args | Just ty' <- coreView ty = split orig_ty ty' args split orig_ty (AppTy ty arg) args = split ty ty (arg:args) - split orig_ty (NoteTy _ ty) args = split orig_ty ty args + split orig_ty (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args) split orig_ty (FunTy ty1 ty2) args = ASSERT( null args ) (TyConApp funTyCon [], [ty1,ty2]) - split orig_ty (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args) split orig_ty ty args = (orig_ty, args) \end{code} @@ -423,149 +268,99 @@ mkFunTy arg res = FunTy arg res mkFunTys :: [Type] -> Type -> Type mkFunTys tys ty = foldr FunTy ty tys +isFunTy :: Type -> Bool +isFunTy ty = isJust (splitFunTy_maybe ty) + +splitFunTy :: Type -> (Type, Type) +splitFunTy ty | Just ty' <- coreView ty = splitFunTy ty' +splitFunTy (FunTy arg res) = (arg, res) +splitFunTy other = pprPanic "splitFunTy" (ppr other) + splitFunTy_maybe :: Type -> Maybe (Type, Type) -splitFunTy_maybe (FunTy arg res) = Just (arg, res) -splitFunTy_maybe (NoteTy _ ty) = splitFunTy_maybe ty -splitFunTy_maybe other = Nothing +splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty' +splitFunTy_maybe (FunTy arg res) = Just (arg, res) +splitFunTy_maybe other = Nothing splitFunTys :: Type -> ([Type], Type) splitFunTys ty = split [] ty ty where - split args orig_ty (FunTy arg res) = split (arg:args) res res - split args orig_ty (NoteTy _ ty) = split args orig_ty ty - split args orig_ty ty = (reverse args, orig_ty) + split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty' + split args orig_ty (FunTy arg res) = split (arg:args) res res + split args orig_ty ty = (reverse args, orig_ty) -splitFunTysN :: String -> Int -> Type -> ([Type], Type) -splitFunTysN msg orig_n orig_ty = split orig_n [] orig_ty orig_ty - where - split 0 args syn_ty ty = (reverse args, syn_ty) - split n args syn_ty (FunTy arg res) = split (n-1) (arg:args) res res - split n args syn_ty (NoteTy _ ty) = split n args syn_ty ty - split n args syn_ty ty = pprPanic ("splitFunTysN: " ++ msg) (int orig_n <+> pprType orig_ty) +splitFunTysN :: Int -> Type -> ([Type], Type) +-- Split off exactly n arg tys +splitFunTysN 0 ty = ([], ty) +splitFunTysN n ty = case splitFunTy ty of { (arg, res) -> + case splitFunTysN (n-1) res of { (args, res) -> + (arg:args, res) }} zipFunTys :: Outputable a => [a] -> Type -> ([(a,Type)], Type) zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty where - split acc [] nty ty = (reverse acc, nty) - split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res - split acc xs nty (NoteTy _ ty) = split acc xs nty ty - split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> pprType orig_ty) + split acc [] nty ty = (reverse acc, nty) + split acc xs nty ty + | Just ty' <- coreView ty = split acc xs nty ty' + split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res + split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> ppr orig_ty) funResultTy :: Type -> Type -funResultTy (FunTy arg res) = res -funResultTy (NoteTy _ ty) = funResultTy ty -funResultTy ty = pprPanic "funResultTy" (pprType ty) +funResultTy ty | Just ty' <- coreView ty = funResultTy ty' +funResultTy (FunTy arg res) = res +funResultTy ty = pprPanic "funResultTy" (ppr ty) funArgTy :: Type -> Type -funArgTy (FunTy arg res) = arg -funArgTy (NoteTy _ ty) = funArgTy ty -funArgTy ty = pprPanic "funArgTy" (pprType ty) +funArgTy ty | Just ty' <- coreView ty = funArgTy ty' +funArgTy (FunTy arg res) = arg +funArgTy ty = pprPanic "funArgTy" (ppr ty) \end{code} --------------------------------------------------------------------- TyConApp ~~~~~~~~ +@mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy, +as apppropriate. \begin{code} mkTyConApp :: TyCon -> [Type] -> Type mkTyConApp tycon tys - | isFunTyCon tycon && length tys == 2 - = case tys of - (ty1:ty2:_) -> FunTy ty1 ty2 + | isFunTyCon tycon, [ty1,ty2] <- tys + = FunTy ty1 ty2 | otherwise - = ASSERT(not (isSynTyCon tycon)) - TyConApp tycon tys + = TyConApp tycon tys mkTyConTy :: TyCon -> Type -mkTyConTy tycon = ASSERT( not (isSynTyCon tycon) ) - TyConApp tycon [] +mkTyConTy tycon = mkTyConApp tycon [] -- splitTyConApp "looks through" synonyms, because they don't -- mean a distinct type, but all other type-constructor applications -- including functions are returned as Just .. +tyConAppTyCon :: Type -> TyCon +tyConAppTyCon ty = fst (splitTyConApp ty) + +tyConAppArgs :: Type -> [Type] +tyConAppArgs ty = snd (splitTyConApp ty) + +splitTyConApp :: Type -> (TyCon, [Type]) +splitTyConApp ty = case splitTyConApp_maybe ty of + Just stuff -> stuff + Nothing -> pprPanic "splitTyConApp" (ppr ty) + splitTyConApp_maybe :: Type -> Maybe (TyCon, [Type]) +splitTyConApp_maybe ty | Just ty' <- coreView ty = splitTyConApp_maybe ty' splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys) splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res]) -splitTyConApp_maybe (NoteTy _ ty) = splitTyConApp_maybe ty splitTyConApp_maybe other = Nothing - --- splitAlgTyConApp_maybe looks for --- *saturated* applications of *algebraic* data types --- "Algebraic" => newtype, data type, or dictionary (not function types) --- We return the constructors too. - -splitAlgTyConApp_maybe :: Type -> Maybe (TyCon, [Type], [DataCon]) -splitAlgTyConApp_maybe (TyConApp tc tys) - | isAlgTyCon tc && - tyConArity tc == length tys = Just (tc, tys, tyConDataCons tc) -splitAlgTyConApp_maybe (NoteTy _ ty) = splitAlgTyConApp_maybe ty -splitAlgTyConApp_maybe other = Nothing - -splitAlgTyConApp :: Type -> (TyCon, [Type], [DataCon]) - -- Here the "algebraic" property is an *assertion* -splitAlgTyConApp (TyConApp tc tys) = ASSERT( isAlgTyCon tc && tyConArity tc == length tys ) - (tc, tys, tyConDataCons tc) -splitAlgTyConApp (NoteTy _ ty) = splitAlgTyConApp ty \end{code} -"Dictionary" types are just ordinary data types, but you can -tell from the type constructor whether it's a dictionary or not. - -\begin{code} -mkDictTy :: Class -> [Type] -> Type -mkDictTy clas tys = TyConApp (classTyCon clas) tys - -splitDictTy_maybe :: Type -> Maybe (Class, [Type]) -splitDictTy_maybe (TyConApp tc tys) - | maybeToBool maybe_class - && tyConArity tc == length tys = Just (clas, tys) - where - maybe_class = tyConClass_maybe tc - Just clas = maybe_class - -splitDictTy_maybe (NoteTy _ ty) = splitDictTy_maybe ty -splitDictTy_maybe other = Nothing - -isDictTy :: Type -> Bool - -- This version is slightly more efficient than (maybeToBool . splitDictTy) -isDictTy (TyConApp tc tys) - | maybeToBool (tyConClass_maybe tc) - && tyConArity tc == length tys - = True -isDictTy (NoteTy _ ty) = isDictTy ty -isDictTy other = False -\end{code} --------------------------------------------------------------------- SynTy ~~~~~ -\begin{code} -mkSynTy syn_tycon tys - = ASSERT( isSynTyCon syn_tycon ) - ASSERT( isNotUsgTy body ) - ASSERT( length tyvars == length tys ) - NoteTy (SynNote (TyConApp syn_tycon tys)) - (substTy (mkTyVarSubst tyvars tys) body) - where - (tyvars, body) = getSynTyConDefn syn_tycon - -isSynTy (NoteTy (SynNote _) _) = True -isSynTy other = False - -deNoteType :: Type -> Type - -- Sorry for the cute name -deNoteType ty@(TyVarTy tyvar) = ty -deNoteType (TyConApp tycon tys) = TyConApp tycon (map deNoteType tys) -deNoteType (NoteTy _ ty) = deNoteType ty -deNoteType (AppTy fun arg) = AppTy (deNoteType fun) (deNoteType arg) -deNoteType (FunTy fun arg) = FunTy (deNoteType fun) (deNoteType arg) -deNoteType (ForAllTy tv ty) = ForAllTy tv (deNoteType ty) -\end{code} - Notes on type synonyms ~~~~~~~~~~~~~~~~~~~~~~ The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try @@ -581,259 +376,190 @@ The reason is that we then get better (shorter) type signatures in interfaces. Notably this plays a role in tcTySigs in TcBinds.lhs. - + Representation types + ~~~~~~~~~~~~~~~~~~~~ repType looks through (a) for-alls, and - (b) newtypes -in addition to synonyms. It's useful in the back end where we're not -interested in newtypes anymore. + (b) synonyms + (c) predicates + (d) usage annotations + (e) all newtypes, including recursive ones +It's useful in the back end. \begin{code} repType :: Type -> Type -repType (NoteTy _ ty) = repType ty -repType (ForAllTy _ ty) = repType ty -repType (TyConApp tc tys) | isNewTyCon tc = repType (new_type_rep tc tys) -repType other_ty = other_ty - -splitNewType_maybe :: Type -> Maybe Type --- Find the representation of a newtype, if it is one --- Looks through multiple levels of newtype -splitNewType_maybe (NoteTy _ ty) = splitNewType_maybe ty -splitNewType_maybe (TyConApp tc tys) | isNewTyCon tc = case splitNewType_maybe rep_ty of - Just rep_ty' -> Just rep_ty' - Nothing -> Just rep_ty - where - rep_ty = new_type_rep tc tys - -splitNewType_maybe other = Nothing - -new_type_rep :: TyCon -> [Type] -> Type --- The representation type for (T t1 .. tn), where T is a newtype --- Looks through one layer only -new_type_rep tc tys - = ASSERT( isNewTyCon tc ) - case splitFunTy_maybe (applyTys (dataConType (head (tyConDataCons tc))) tys) of - Just (rep_ty, _) -> rep_ty -\end{code} - - - ---------------------------------------------------------------------- - UsgNote - ~~~~~~~ - -NB: Invariant: if present, usage note is at the very top of the type. -This should be carefully preserved. - -In some parts of the compiler, comments use the _Once Upon a -Polymorphic Type_ (POPL'99) usage of "sigma = usage-annotated type; -tau = un-usage-annotated type"; unfortunately this conflicts with the -rho/tau/theta/sigma usage in the rest of the compiler. -(KSW 1999-04) - -\begin{code} -mkUsgTy :: UsageAnn -> Type -> Type -#ifndef USMANY -mkUsgTy UsMany ty = ASSERT2( isNotUsgTy ty, pprType ty ) - ty -#endif -mkUsgTy usg ty = ASSERT2( isNotUsgTy ty, pprType ty ) - NoteTy (UsgNote usg) ty - --- The isUsgTy function is utterly useless if UsManys are omitted. --- Be warned! KSW 1999-04. -isUsgTy :: Type -> Bool -#ifndef USMANY -isUsgTy _ = True -#else -isUsgTy (NoteTy (UsgNote _) _) = True -isUsgTy other = False -#endif - --- The isNotUsgTy function may return a false True if UsManys are omitted; --- in other words, A SSERT( isNotUsgTy ty ) may be useful but --- A SSERT( not (isNotUsg ty) ) is asking for trouble. KSW 1999-04. -isNotUsgTy :: Type -> Bool -isNotUsgTy (NoteTy (UsgNote _) _) = False -isNotUsgTy other = True - --- splitUsgTy_maybe is not exported, since it is meaningless if --- UsManys are omitted. It is used in several places in this module, --- however. KSW 1999-04. -splitUsgTy_maybe :: Type -> Maybe (UsageAnn,Type) -splitUsgTy_maybe (NoteTy (UsgNote usg) ty2) = ASSERT( isNotUsgTy ty2 ) - Just (usg,ty2) -splitUsgTy_maybe ty = Nothing - -splitUsgTy :: Type -> (UsageAnn,Type) -splitUsgTy ty = case splitUsgTy_maybe ty of - Just ans -> ans - Nothing -> -#ifndef USMANY - (UsMany,ty) -#else - pprPanic "splitUsgTy: no usage annot:" $ pprType ty -#endif - -tyUsg :: Type -> UsageAnn -tyUsg = fst . splitUsgTy +-- Only applied to types of kind *; hence tycons are saturated +repType ty | Just ty' <- coreView ty = repType ty' +repType (ForAllTy _ ty) = repType ty +repType (TyConApp tc tys) + | isNewTyCon tc = -- Recursive newtypes are opaque to coreView + -- but we must expand them here. Sure to + -- be saturated because repType is only applied + -- to types of kind * + ASSERT( isRecursiveTyCon tc && + tys `lengthIs` tyConArity tc ) + repType (new_type_rep tc tys) +repType ty = ty + +-- new_type_rep doesn't ask any questions: +-- it just expands newtype, whether recursive or not +new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon ) + case newTyConRep new_tycon of + (tvs, rep_ty) -> substTyWith tvs tys rep_ty + +-- ToDo: this could be moved to the code generator, using splitTyConApp instead +-- of inspecting the type directly. +typePrimRep :: Type -> PrimRep +typePrimRep ty = case repType ty of + TyConApp tc _ -> tyConPrimRep tc + FunTy _ _ -> PtrRep + AppTy _ _ -> PtrRep -- See note below + TyVarTy _ -> PtrRep + other -> pprPanic "typePrimRep" (ppr ty) + -- Types of the form 'f a' must be of kind *, not *#, so + -- we are guaranteed that they are represented by pointers. + -- The reason is that f must have kind *->*, not *->*#, because + -- (we claim) there is no way to constrain f's kind any other + -- way. -unUsgTy :: Type -> Type --- strip outer usage annotation if present -unUsgTy ty = case splitUsgTy_maybe ty of - Just (_,ty1) -> ASSERT2( isNotUsgTy ty1, pprType ty ) - ty1 - Nothing -> ty \end{code} - --------------------------------------------------------------------- ForAllTy ~~~~~~~~ -We need to be clever here with usage annotations; they need to be -lifted or lowered through the forall as appropriate. - \begin{code} mkForAllTy :: TyVar -> Type -> Type -mkForAllTy tyvar ty = case splitUsgTy_maybe ty of - Just (usg,ty') -> NoteTy (UsgNote usg) - (ForAllTy tyvar ty') - Nothing -> ForAllTy tyvar ty +mkForAllTy tyvar ty + = mkForAllTys [tyvar] ty mkForAllTys :: [TyVar] -> Type -> Type -mkForAllTys tyvars ty = case splitUsgTy_maybe ty of - Just (usg,ty') -> NoteTy (UsgNote usg) - (foldr ForAllTy ty' tyvars) - Nothing -> foldr ForAllTy ty tyvars +mkForAllTys tyvars ty = foldr ForAllTy ty tyvars + +isForAllTy :: Type -> Bool +isForAllTy (NoteTy _ ty) = isForAllTy ty +isForAllTy (ForAllTy _ _) = True +isForAllTy other_ty = False splitForAllTy_maybe :: Type -> Maybe (TyVar, Type) -splitForAllTy_maybe ty = case splitUsgTy_maybe ty of - Just (usg,ty') -> do (tyvar,ty'') <- splitFAT_m ty' - return (tyvar, NoteTy (UsgNote usg) ty'') - Nothing -> splitFAT_m ty +splitForAllTy_maybe ty = splitFAT_m ty where - splitFAT_m (NoteTy _ ty) = splitFAT_m ty - splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty) - splitFAT_m _ = Nothing - -isForAllTy :: Type -> Bool -isForAllTy (NoteTy _ ty) = isForAllTy ty -isForAllTy (ForAllTy tyvar ty) = True -isForAllTy _ = False + splitFAT_m ty | Just ty' <- coreView ty = splitFAT_m ty' + splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty) + splitFAT_m _ = Nothing splitForAllTys :: Type -> ([TyVar], Type) -splitForAllTys ty = case splitUsgTy_maybe ty of - Just (usg,ty') -> let (tvs,ty'') = split ty' ty' [] - in (tvs, NoteTy (UsgNote usg) ty'') - Nothing -> split ty ty [] +splitForAllTys ty = split ty ty [] where - split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs) - split orig_ty (NoteTy _ ty) tvs = split orig_ty ty tvs - split orig_ty t tvs = (reverse tvs, orig_ty) -\end{code} - -@mkPiType@ makes a (->) type or a forall type, depending on whether -it is given a type variable or a term variable. + split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs + split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs) + split orig_ty t tvs = (reverse tvs, orig_ty) -\begin{code} -mkPiType :: IdOrTyVar -> Type -> Type -- The more polymorphic version doesn't work... -mkPiType v ty | isId v = mkFunTy (idType v) ty - | otherwise = mkForAllTy v ty +dropForAlls :: Type -> Type +dropForAlls ty = snd (splitForAllTys ty) \end{code} -Applying a for-all to its arguments +-- (mkPiType now in CoreUtils) + +applyTy, applyTys +~~~~~~~~~~~~~~~~~ +Instantiate a for-all type with one or more type arguments. +Used when we have a polymorphic function applied to type args: + f t1 t2 +Then we use (applyTys type-of-f [t1,t2]) to compute the type of +the expression. \begin{code} applyTy :: Type -> Type -> Type -applyTy (NoteTy note@(UsgNote _) fun) arg = NoteTy note (applyTy fun arg) -applyTy (NoteTy _ fun) arg = applyTy fun arg -applyTy (ForAllTy tv ty) arg = ASSERT( isNotUsgTy arg ) - substTy (mkTyVarSubst [tv] [arg]) ty -applyTy other arg = panic "applyTy" +applyTy ty arg | Just ty' <- coreView ty = applyTy ty' arg +applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty +applyTy other arg = panic "applyTy" applyTys :: Type -> [Type] -> Type -applyTys fun_ty arg_tys - = substTy (mkTyVarSubst tvs arg_tys) ty - where - (tvs, ty) = split fun_ty arg_tys - - split fun_ty [] = ([], fun_ty) - split (NoteTy _ fun_ty) args = split fun_ty args - split (ForAllTy tv fun_ty) (arg:args) = ASSERT2( isNotUsgTy arg, vcat (map pprType arg_tys) $$ - text "in application of" <+> pprType fun_ty) - case split fun_ty args of - (tvs, ty) -> (tv:tvs, ty) - split other_ty args = panic "applyTys" - -{- OLD version with bogus usage stuff - - ************* CHECK WITH KEITH ************** - - go env ty [] = substTy (mkVarEnv env) ty - go env (NoteTy note@(UsgNote _) fun) - args = NoteTy note (go env fun args) - go env (NoteTy _ fun) args = go env fun args - go env (ForAllTy tv ty) (arg:args) = go ((tv,arg):env) ty args - go env other args = panic "applyTys" --} +-- This function is interesting because +-- a) the function may have more for-alls than there are args +-- b) less obviously, it may have fewer for-alls +-- For case (b) think of +-- applyTys (forall a.a) [forall b.b, Int] +-- This really can happen, via dressing up polymorphic types with newtype +-- clothing. Here's an example: +-- newtype R = R (forall a. a->a) +-- foo = case undefined :: R of +-- R f -> f () + +applyTys orig_fun_ty [] = orig_fun_ty +applyTys orig_fun_ty arg_tys + | n_tvs == n_args -- The vastly common case + = substTyWith tvs arg_tys rho_ty + | n_tvs > n_args -- Too many for-alls + = substTyWith (take n_args tvs) arg_tys + (mkForAllTys (drop n_args tvs) rho_ty) + | otherwise -- Too many type args + = ASSERT2( n_tvs > 0, ppr orig_fun_ty ) -- Zero case gives infnite loop! + applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty) + (drop n_tvs arg_tys) + where + (tvs, rho_ty) = splitForAllTys orig_fun_ty + n_tvs = length tvs + n_args = length arg_tys \end{code} -Note that we allow applications to be of usage-annotated- types, as an -extension: we handle them by lifting the annotation outside. The -argument, however, must still be unannotated. %************************************************************************ %* * -\subsection{Stuff to do with the source-language types} +\subsection{Source types} %* * %************************************************************************ -\begin{code} -type RhoType = Type -type TauType = Type -type ThetaType = [(Class, [Type])] -type SigmaType = Type -\end{code} +A "source type" is a type that is a separate type as far as the type checker is +concerned, but which has low-level representation as far as the back end is concerned. -@isTauTy@ tests for nested for-alls. +Source types are always lifted. -\begin{code} -isTauTy :: Type -> Bool -isTauTy (TyVarTy v) = True -isTauTy (TyConApp _ tys) = all isTauTy tys -isTauTy (AppTy a b) = isTauTy a && isTauTy b -isTauTy (FunTy a b) = isTauTy a && isTauTy b -isTauTy (NoteTy _ ty) = isTauTy ty -isTauTy other = False -\end{code} +The key function is predTypeRep which gives the representation of a source type: \begin{code} -mkRhoTy :: [(Class, [Type])] -> Type -> Type -mkRhoTy theta ty = foldr (\(c,t) r -> FunTy (mkDictTy c t) r) ty theta - -splitRhoTy :: Type -> ([(Class, [Type])], Type) -splitRhoTy ty = split ty ty [] - where - split orig_ty (FunTy arg res) ts = case splitDictTy_maybe arg of - Just pair -> split res res (pair:ts) - Nothing -> (reverse ts, orig_ty) - split orig_ty (NoteTy _ ty) ts = split orig_ty ty ts - split orig_ty ty ts = (reverse ts, orig_ty) +mkPredTy :: PredType -> Type +mkPredTy pred = PredTy pred + +mkPredTys :: ThetaType -> [Type] +mkPredTys preds = map PredTy preds + +predTypeRep :: PredType -> Type +-- Convert a PredType to its "representation type"; +-- the post-type-checking type used by all the Core passes of GHC. +-- Unwraps only the outermost level; for example, the result might +-- be a newtype application +predTypeRep (IParam _ ty) = ty +predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys + -- Result might be a newtype application, but the consumer will + -- look through that too if necessary \end{code} +%************************************************************************ +%* * + NewTypes +%* * +%************************************************************************ \begin{code} -mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkRhoTy theta tau) - -splitSigmaTy :: Type -> ([TyVar], [(Class, [Type])], Type) -splitSigmaTy ty = - (tyvars, theta, tau) - where - (tyvars,rho) = splitForAllTys ty - (theta,tau) = splitRhoTy rho +splitRecNewType_maybe :: Type -> Maybe Type +-- Sometimes we want to look through a recursive newtype, and that's what happens here +-- It only strips *one layer* off, so the caller will usually call itself recursively +-- Only applied to types of kind *, hence the newtype is always saturated +splitRecNewType_maybe ty | Just ty' <- coreView ty = splitRecNewType_maybe ty' +splitRecNewType_maybe (TyConApp tc tys) + | isNewTyCon tc + = ASSERT( tys `lengthIs` tyConArity tc ) -- splitRecNewType_maybe only be applied + -- to *types* (of kind *) + ASSERT( isRecursiveTyCon tc ) -- Guaranteed by coreView + case newTyConRhs tc of + (tvs, rep_ty) -> ASSERT( length tvs == length tys ) + Just (substTyWith tvs tys rep_ty) + +splitRecNewType_maybe other = Nothing \end{code} @@ -850,14 +576,12 @@ splitSigmaTy ty = typeKind :: Type -> Kind typeKind (TyVarTy tyvar) = tyVarKind tyvar -typeKind (TyConApp tycon tys) = foldr (\_ k -> funResultTy k) (tyConKind tycon) tys +typeKind (TyConApp tycon tys) = foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys typeKind (NoteTy _ ty) = typeKind ty -typeKind (AppTy fun arg) = funResultTy (typeKind fun) - -typeKind (FunTy arg res) = boxedTypeKind -- A function is boxed regardless of its result type - -- No functions at the type level, hence we don't need - -- to say (typeKind res). - +typeKind (PredTy _) = liftedTypeKind -- Predicates are always + -- represented by lifted types +typeKind (AppTy fun arg) = kindFunResult (typeKind fun) +typeKind (FunTy arg res) = liftedTypeKind typeKind (ForAllTy tv ty) = typeKind ty \end{code} @@ -867,38 +591,29 @@ typeKind (ForAllTy tv ty) = typeKind ty ~~~~~~~~~~~~~~~~~~~~~~~~ \begin{code} tyVarsOfType :: Type -> TyVarSet - +-- NB: for type synonyms tyVarsOfType does *not* expand the synonym tyVarsOfType (TyVarTy tv) = unitVarSet tv tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs -tyVarsOfType (NoteTy (SynNote ty1) ty2) = tyVarsOfType ty1 -tyVarsOfType (NoteTy (UsgNote _) ty) = tyVarsOfType ty +tyVarsOfType (PredTy sty) = tyVarsOfPred sty tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg -tyVarsOfType (ForAllTy tyvar ty) = tyVarsOfType ty `minusVarSet` unitVarSet tyvar +tyVarsOfType (ForAllTy tyvar ty) = delVarSet (tyVarsOfType ty) tyvar tyVarsOfTypes :: [Type] -> TyVarSet tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys +tyVarsOfPred :: PredType -> TyVarSet +tyVarsOfPred (IParam _ ty) = tyVarsOfType ty +tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys + +tyVarsOfTheta :: ThetaType -> TyVarSet +tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet + -- Add a Note with the free tyvars to the top of the type --- (but under a usage if there is one) addFreeTyVars :: Type -> Type -addFreeTyVars (NoteTy note@(UsgNote _) ty) = NoteTy note (addFreeTyVars ty) -addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty -addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty - --- Find the free names of a type, including the type constructors and classes it mentions -namesOfType :: Type -> NameSet -namesOfType (TyVarTy tv) = unitNameSet (getName tv) -namesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` - namesOfTypes tys -namesOfType (NoteTy (SynNote ty1) ty2) = namesOfType ty1 -namesOfType (NoteTy other_note ty2) = namesOfType ty2 -namesOfType (FunTy arg res) = namesOfType arg `unionNameSets` namesOfType res -namesOfType (AppTy fun arg) = namesOfType fun `unionNameSets` namesOfType arg -namesOfType (ForAllTy tyvar ty) = namesOfType ty `minusNameSet` unitNameSet (getName tyvar) - -namesOfTypes tys = foldr (unionNameSets . namesOfType) emptyNameSet tys +addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty +addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty \end{code} @@ -914,28 +629,31 @@ an interface file. It doesn't change the uniques at all, just the print names. \begin{code} -tidyTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar) -tidyTyVar env@(tidy_env, subst) tyvar - = case lookupVarEnv subst tyvar of - - Just tyvar' -> -- Already substituted - (env, tyvar') - - Nothing -> -- Make a new nice name for it - - case tidyOccName tidy_env (getOccName name) of - (tidy', occ') -> -- New occname reqd - ((tidy', subst'), tyvar') - where - subst' = extendVarEnv subst tyvar tyvar' - tyvar' = setTyVarName tyvar name' - name' = mkLocalName (getUnique name) occ' noSrcLoc - -- Note: make a *user* tyvar, so it printes nicely - -- Could extract src loc, but no need. +tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar) +tidyTyVarBndr (tidy_env, subst) tyvar + = case tidyOccName tidy_env (getOccName name) of + (tidy', occ') -> ((tidy', subst'), tyvar') + where + subst' = extendVarEnv subst tyvar tyvar' + tyvar' = setTyVarName tyvar name' + name' = tidyNameOcc name occ' where name = tyVarName tyvar -tidyTyVars env tyvars = mapAccumL tidyTyVar env tyvars +tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv +-- Add the free tyvars to the env in tidy form, +-- so that we can tidy the type they are free in +tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars)) + +tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar]) +tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars + +tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar) +-- Treat a new tyvar as a binder, and give it a fresh tidy name +tidyOpenTyVar env@(tidy_env, subst) tyvar + = case lookupVarEnv subst tyvar of + Just tyvar' -> (env, tyvar') -- Already substituted + Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder tidyType :: TidyEnv -> Type -> Type tidyType env@(tidy_env, subst) ty @@ -947,21 +665,24 @@ tidyType env@(tidy_env, subst) ty go (TyConApp tycon tys) = let args = map go tys in args `seqList` TyConApp tycon args go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty) + go (PredTy sty) = PredTy (tidyPred env sty) go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg) go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg) - go (ForAllTy tv ty) = ForAllTy tv' $! (tidyType env' ty) - where - (env', tv') = tidyTyVar env tv + go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty) + where + (envp, tvp) = tidyTyVarBndr env tv - go_note (SynNote ty) = SynNote $! (go ty) go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars - go_note note@(UsgNote _) = note -- Usage annotation is already tidy -tidyTypes env tys = map (tidyType env) tys +tidyTypes env tys = map (tidyType env) tys + +tidyPred :: TidyEnv -> PredType -> PredType +tidyPred env (IParam n ty) = IParam n (tidyType env ty) +tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys) \end{code} -@tidyOpenType@ grabs the free type varibles, tidies them +@tidyOpenType@ grabs the free type variables, tidies them and then uses @tidyType@ to work over the type itself \begin{code} @@ -969,8 +690,7 @@ tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type) tidyOpenType env ty = (env', tidyType env' ty) where - env' = foldl go env (varSetElems (tyVarsOfType ty)) - go env tyvar = fst (tidyTyVar env tyvar) + env' = tidyFreeTyVars env (tyVarsOfType ty) tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type]) tidyOpenTypes env tys = mapAccumL tidyOpenType env tys @@ -982,18 +702,60 @@ tidyTopType ty = tidyType emptyTidyEnv ty %************************************************************************ %* * -\subsection{Boxedness and liftedness} + Tidying Kinds %* * %************************************************************************ +We use a grevious hack for tidying KindVars. A TidyEnv contains +a (VarEnv Var) substitution, to express the renaming; but +KindVars are not Vars. The Right Thing ultimately is to make them +into Vars (and perhaps make Kinds into Types), but I just do a hack +here: I make up a TyVar just to remember the new OccName for the +renamed KindVar + \begin{code} -isUnboxedType :: Type -> Bool -isUnboxedType ty = not (isFollowableRep (typePrimRep ty)) +tidyKind :: TidyEnv -> Kind -> (TidyEnv, Kind) +tidyKind env@(tidy_env, subst) (KindVar kvar) + | Just tv <- lookupVarEnv_Directly subst uniq + = (env, KindVar (setKindVarOcc kvar (getOccName tv))) + | otherwise + = ((tidy', subst'), KindVar kvar') + where + uniq = kindVarUniq kvar + (tidy', occ') = tidyOccName tidy_env (kindVarOcc kvar) + kvar' = setKindVarOcc kvar occ' + fake_tv = mkTyVar tv_name (panic "tidyKind:fake tv kind") + tv_name = mkInternalName uniq occ' noSrcLoc + subst' = extendVarEnv subst fake_tv fake_tv + +tidyKind env (FunKind k1 k2) + = (env2, FunKind k1' k2') + where + (env1, k1') = tidyKind env k1 + (env2, k2') = tidyKind env1 k2 + +tidyKind env k = (env, k) -- Atomic kinds +\end{code} + +%************************************************************************ +%* * +\subsection{Liftedness} +%* * +%************************************************************************ + +\begin{code} isUnLiftedType :: Type -> Bool -isUnLiftedType ty = case splitTyConApp_maybe ty of - Just (tc, ty_args) -> isUnLiftedTyCon tc - other -> False + -- isUnLiftedType returns True for forall'd unlifted types: + -- x :: forall a. Int# + -- I found bindings like these were getting floated to the top level. + -- They are pretty bogus types, mind you. It would be better never to + -- construct them + +isUnLiftedType ty | Just ty' <- coreView ty = isUnLiftedType ty' +isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty +isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc +isUnLiftedType other = False isUnboxedTupleType :: Type -> Bool isUnboxedTupleType ty = case splitTyConApp_maybe ty of @@ -1003,110 +765,468 @@ isUnboxedTupleType ty = case splitTyConApp_maybe ty of -- Should only be applied to *types*; hence the assert isAlgType :: Type -> Bool isAlgType ty = case splitTyConApp_maybe ty of - Just (tc, ty_args) -> ASSERT( length ty_args == tyConArity tc ) + Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc ) isAlgTyCon tc other -> False +\end{code} --- Should only be applied to *types*; hence the assert -isDataType :: Type -> Bool -isDataType ty = case splitTyConApp_maybe ty of - Just (tc, ty_args) -> ASSERT( length ty_args == tyConArity tc ) - isDataTyCon tc - other -> False +@isStrictType@ computes whether an argument (or let RHS) should +be computed strictly or lazily, based only on its type. +Works just like isUnLiftedType, except that it has a special case +for dictionaries. Since it takes account of ClassP, you might think +this function should be in TcType, but isStrictType is used by DataCon, +which is below TcType in the hierarchy, so it's convenient to put it here. + +\begin{code} +isStrictType (PredTy pred) = isStrictPred pred +isStrictType ty | Just ty' <- coreView ty = isStrictType ty' +isStrictType (ForAllTy tv ty) = isStrictType ty +isStrictType (TyConApp tc _) = isUnLiftedTyCon tc +isStrictType other = False + +isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas)) +isStrictPred other = False + -- We may be strict in dictionary types, but only if it + -- has more than one component. + -- [Being strict in a single-component dictionary risks + -- poking the dictionary component, which is wrong.] +\end{code} -isNewType :: Type -> Bool -isNewType ty = case splitTyConApp_maybe ty of - Just (tc, ty_args) -> ASSERT( length ty_args == tyConArity tc ) - isNewTyCon tc +\begin{code} +isPrimitiveType :: Type -> Bool +-- Returns types that are opaque to Haskell. +-- Most of these are unlifted, but now that we interact with .NET, we +-- may have primtive (foreign-imported) types that are lifted +isPrimitiveType ty = case splitTyConApp_maybe ty of + Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc ) + isPrimTyCon tc other -> False +\end{code} -typePrimRep :: Type -> PrimRep -typePrimRep ty = case splitTyConApp_maybe ty of - Just (tc, ty_args) -> tyConPrimRep tc - other -> PtrRep + +%************************************************************************ +%* * +\subsection{Sequencing on types +%* * +%************************************************************************ + +\begin{code} +seqType :: Type -> () +seqType (TyVarTy tv) = tv `seq` () +seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2 +seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2 +seqType (NoteTy note t2) = seqNote note `seq` seqType t2 +seqType (PredTy p) = seqPred p +seqType (TyConApp tc tys) = tc `seq` seqTypes tys +seqType (ForAllTy tv ty) = tv `seq` seqType ty + +seqTypes :: [Type] -> () +seqTypes [] = () +seqTypes (ty:tys) = seqType ty `seq` seqTypes tys + +seqNote :: TyNote -> () +seqNote (FTVNote set) = sizeUniqSet set `seq` () + +seqPred :: PredType -> () +seqPred (ClassP c tys) = c `seq` seqTypes tys +seqPred (IParam n ty) = n `seq` seqType ty \end{code} + %************************************************************************ %* * -\subsection{Equality on types} + Equality for Core types + (We don't use instances so that we know where it happens) %* * %************************************************************************ -For the moment at least, type comparisons don't work if -there are embedded for-alls. +Note that eqType works right even for partial applications of newtypes. +See Note [Newtype eta] in TyCon.lhs \begin{code} -instance Eq Type where - ty1 == ty2 = case ty1 `cmpTy` ty2 of { EQ -> True; other -> False } +coreEqType :: Type -> Type -> Bool +coreEqType t1 t2 + = eq rn_env t1 t2 + where + rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2)) + + eq env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 == rnOccR env tv2 + eq env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = eq (rnBndr2 env tv1 tv2) t1 t2 + eq env (AppTy s1 t1) (AppTy s2 t2) = eq env s1 s2 && eq env t1 t2 + eq env (FunTy s1 t1) (FunTy s2 t2) = eq env s1 s2 && eq env t1 t2 + eq env (TyConApp tc1 tys1) (TyConApp tc2 tys2) + | tc1 == tc2, all2 (eq env) tys1 tys2 = True + -- The lengths should be equal because + -- the two types have the same kind + -- NB: if the type constructors differ that does not + -- necessarily mean that the types aren't equal + -- (synonyms, newtypes) + -- Even if the type constructors are the same, but the arguments + -- differ, the two types could be the same (e.g. if the arg is just + -- ignored in the RHS). In both these cases we fall through to an + -- attempt to expand one side or the other. + + -- Now deal with newtypes, synonyms, pred-tys + eq env t1 t2 | Just t1' <- coreView t1 = eq env t1' t2 + | Just t2' <- coreView t2 = eq env t1 t2' + + -- Fall through case; not equal! + eq env t1 t2 = False +\end{code} -instance Ord Type where - compare ty1 ty2 = cmpTy ty1 ty2 -cmpTy :: Type -> Type -> Ordering -cmpTy ty1 ty2 - = cmp emptyVarEnv ty1 ty2 +%************************************************************************ +%* * + Comparision for source types + (We don't use instances so that we know where it happens) +%* * +%************************************************************************ + +Note that + tcEqType, tcCmpType +do *not* look through newtypes, PredTypes + +\begin{code} +tcEqType :: Type -> Type -> Bool +tcEqType t1 t2 = isEqual $ cmpType t1 t2 + +tcEqTypes :: [Type] -> [Type] -> Bool +tcEqTypes tys1 tys2 = isEqual $ cmpTypes tys1 tys2 + +tcCmpType :: Type -> Type -> Ordering +tcCmpType t1 t2 = cmpType t1 t2 + +tcCmpTypes :: [Type] -> [Type] -> Ordering +tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2 + +tcEqPred :: PredType -> PredType -> Bool +tcEqPred p1 p2 = isEqual $ cmpPred p1 p2 + +tcCmpPred :: PredType -> PredType -> Ordering +tcCmpPred p1 p2 = cmpPred p1 p2 + +tcEqTypeX :: RnEnv2 -> Type -> Type -> Bool +tcEqTypeX env t1 t2 = isEqual $ cmpTypeX env t1 t2 +\end{code} + +Now here comes the real worker + +\begin{code} +cmpType :: Type -> Type -> Ordering +cmpType t1 t2 = cmpTypeX rn_env t1 t2 where - -- The "env" maps type variables in ty1 to type variables in ty2 - -- So when comparing for-alls.. (forall tv1 . t1) (forall tv2 . t2) - -- we in effect substitute tv2 for tv1 in t1 before continuing - lookup env tv1 = case lookupVarEnv env tv1 of - Just tv2 -> tv2 - Nothing -> tv1 - - -- Get rid of NoteTy - cmp env (NoteTy _ ty1) ty2 = cmp env ty1 ty2 - cmp env ty1 (NoteTy _ ty2) = cmp env ty1 ty2 - - -- Deal with equal constructors - cmp env (TyVarTy tv1) (TyVarTy tv2) = lookup env tv1 `compare` tv2 - cmp env (AppTy f1 a1) (AppTy f2 a2) = cmp env f1 f2 `thenCmp` cmp env a1 a2 - cmp env (FunTy f1 a1) (FunTy f2 a2) = cmp env f1 f2 `thenCmp` cmp env a1 a2 - cmp env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmps env tys1 tys2) - cmp env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmp (extendVarEnv env tv1 tv2) t1 t2 - - -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy - cmp env (AppTy _ _) (TyVarTy _) = GT - - cmp env (FunTy _ _) (TyVarTy _) = GT - cmp env (FunTy _ _) (AppTy _ _) = GT + rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2)) + +cmpTypes :: [Type] -> [Type] -> Ordering +cmpTypes ts1 ts2 = cmpTypesX rn_env ts1 ts2 + where + rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2)) + +cmpPred :: PredType -> PredType -> Ordering +cmpPred p1 p2 = cmpPredX rn_env p1 p2 + where + rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfPred p1 `unionVarSet` tyVarsOfPred p2)) + +cmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse +cmpTypeX env t1 t2 | Just t1' <- tcView t1 = cmpTypeX env t1' t2 + | Just t2' <- tcView t2 = cmpTypeX env t1 t2' + +cmpTypeX env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 `compare` rnOccR env tv2 +cmpTypeX env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTypeX (rnBndr2 env tv1 tv2) t1 t2 +cmpTypeX env (AppTy s1 t1) (AppTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2 +cmpTypeX env (FunTy s1 t1) (FunTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2 +cmpTypeX env (PredTy p1) (PredTy p2) = cmpPredX env p1 p2 +cmpTypeX env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` cmpTypesX env tys1 tys2 +cmpTypeX env t1 (NoteTy _ t2) = cmpTypeX env t1 t2 + + -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < PredTy +cmpTypeX env (AppTy _ _) (TyVarTy _) = GT - cmp env (TyConApp _ _) (TyVarTy _) = GT - cmp env (TyConApp _ _) (AppTy _ _) = GT - cmp env (TyConApp _ _) (FunTy _ _) = GT +cmpTypeX env (FunTy _ _) (TyVarTy _) = GT +cmpTypeX env (FunTy _ _) (AppTy _ _) = GT - cmp env (ForAllTy _ _) other = GT +cmpTypeX env (TyConApp _ _) (TyVarTy _) = GT +cmpTypeX env (TyConApp _ _) (AppTy _ _) = GT +cmpTypeX env (TyConApp _ _) (FunTy _ _) = GT - cmp env _ _ = LT +cmpTypeX env (ForAllTy _ _) (TyVarTy _) = GT +cmpTypeX env (ForAllTy _ _) (AppTy _ _) = GT +cmpTypeX env (ForAllTy _ _) (FunTy _ _) = GT +cmpTypeX env (ForAllTy _ _) (TyConApp _ _) = GT + +cmpTypeX env (PredTy _) t2 = GT + +cmpTypeX env _ _ = LT + +------------- +cmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering +cmpTypesX env [] [] = EQ +cmpTypesX env (t1:tys1) (t2:tys2) = cmpTypeX env t1 t2 `thenCmp` cmpTypesX env tys1 tys2 +cmpTypesX env [] tys = LT +cmpTypesX env ty [] = GT + +------------- +cmpPredX :: RnEnv2 -> PredType -> PredType -> Ordering +cmpPredX env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` cmpTypeX env ty1 ty2 + -- Compare types as well as names for implicit parameters + -- This comparison is used exclusively (I think) for the + -- finite map built in TcSimplify +cmpPredX env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` cmpTypesX env tys1 tys2 +cmpPredX env (IParam _ _) (ClassP _ _) = LT +cmpPredX env (ClassP _ _) (IParam _ _) = GT +\end{code} + +PredTypes are used as a FM key in TcSimplify, +so we take the easy path and make them an instance of Ord - cmps env [] [] = EQ - cmps env (t:ts) [] = GT - cmps env [] (t:ts) = LT - cmps env (t1:t1s) (t2:t2s) = cmp env t1 t2 `thenCmp` cmps env t1s t2s +\begin{code} +instance Eq PredType where { (==) = tcEqPred } +instance Ord PredType where { compare = tcCmpPred } \end{code} %************************************************************************ %* * -\subsection{Sequencing on types + Type substitutions %* * %************************************************************************ \begin{code} -seqType :: Type -> () -seqType (TyVarTy tv) = tv `seq` () -seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2 -seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2 -seqType (NoteTy note t2) = seqNote note `seq` seqType t2 -seqType (TyConApp tc tys) = tc `seq` seqTypes tys -seqType (ForAllTy tv ty) = tv `seq` seqType ty +data TvSubst + = TvSubst InScopeSet -- The in-scope type variables + TvSubstEnv -- The substitution itself + -- See Note [Apply Once] + +{- ---------------------------------------------------------- + Note [Apply Once] + +We use TvSubsts to instantiate things, and we might instantiate + forall a b. ty +\with the types + [a, b], or [b, a]. +So the substition might go [a->b, b->a]. A similar situation arises in Core +when we find a beta redex like + (/\ a /\ b -> e) b a +Then we also end up with a substition that permutes type variables. Other +variations happen to; for example [a -> (a, b)]. + + *************************************************** + *** So a TvSubst must be applied precisely once *** + *************************************************** + +A TvSubst is not idempotent, but, unlike the non-idempotent substitution +we use during unifications, it must not be repeatedly applied. +-------------------------------------------------------------- -} + + +type TvSubstEnv = TyVarEnv Type + -- A TvSubstEnv is used both inside a TvSubst (with the apply-once + -- invariant discussed in Note [Apply Once]), and also independently + -- in the middle of matching, and unification (see Types.Unify) + -- So you have to look at the context to know if it's idempotent or + -- apply-once or whatever +emptyTvSubstEnv :: TvSubstEnv +emptyTvSubstEnv = emptyVarEnv + +composeTvSubst :: InScopeSet -> TvSubstEnv -> TvSubstEnv -> TvSubstEnv +-- (compose env1 env2)(x) is env1(env2(x)); i.e. apply env2 then env1 +-- It assumes that both are idempotent +-- Typically, env1 is the refinement to a base substitution env2 +composeTvSubst in_scope env1 env2 + = env1 `plusVarEnv` mapVarEnv (substTy subst1) env2 + -- First apply env1 to the range of env2 + -- Then combine the two, making sure that env1 loses if + -- both bind the same variable; that's why env1 is the + -- *left* argument to plusVarEnv, because the right arg wins + where + subst1 = TvSubst in_scope env1 -seqTypes :: [Type] -> () -seqTypes [] = () -seqTypes (ty:tys) = seqType ty `seq` seqTypes tys +emptyTvSubst = TvSubst emptyInScopeSet emptyVarEnv -seqNote :: TyNote -> () -seqNote (SynNote ty) = seqType ty -seqNote (FTVNote set) = sizeUniqSet set `seq` () -seqNote (UsgNote usg) = usg `seq` () +isEmptyTvSubst :: TvSubst -> Bool +isEmptyTvSubst (TvSubst _ env) = isEmptyVarEnv env + +mkTvSubst :: InScopeSet -> TvSubstEnv -> TvSubst +mkTvSubst = TvSubst + +getTvSubstEnv :: TvSubst -> TvSubstEnv +getTvSubstEnv (TvSubst _ env) = env + +getTvInScope :: TvSubst -> InScopeSet +getTvInScope (TvSubst in_scope _) = in_scope + +isInScope :: Var -> TvSubst -> Bool +isInScope v (TvSubst in_scope _) = v `elemInScopeSet` in_scope + +notElemTvSubst :: TyVar -> TvSubst -> Bool +notElemTvSubst tv (TvSubst _ env) = not (tv `elemVarEnv` env) + +setTvSubstEnv :: TvSubst -> TvSubstEnv -> TvSubst +setTvSubstEnv (TvSubst in_scope _) env = TvSubst in_scope env + +extendTvInScope :: TvSubst -> [Var] -> TvSubst +extendTvInScope (TvSubst in_scope env) vars = TvSubst (extendInScopeSetList in_scope vars) env + +extendTvSubst :: TvSubst -> TyVar -> Type -> TvSubst +extendTvSubst (TvSubst in_scope env) tv ty = TvSubst in_scope (extendVarEnv env tv ty) + +extendTvSubstList :: TvSubst -> [TyVar] -> [Type] -> TvSubst +extendTvSubstList (TvSubst in_scope env) tvs tys + = TvSubst in_scope (extendVarEnvList env (tvs `zip` tys)) + +-- mkOpenTvSubst and zipOpenTvSubst generate the in-scope set from +-- the types given; but it's just a thunk so with a bit of luck +-- it'll never be evaluated + +mkOpenTvSubst :: TvSubstEnv -> TvSubst +mkOpenTvSubst env = TvSubst (mkInScopeSet (tyVarsOfTypes (varEnvElts env))) env + +zipOpenTvSubst :: [TyVar] -> [Type] -> TvSubst +zipOpenTvSubst tyvars tys +#ifdef DEBUG + | length tyvars /= length tys + = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst + | otherwise +#endif + = TvSubst (mkInScopeSet (tyVarsOfTypes tys)) (zipTyEnv tyvars tys) + +-- mkTopTvSubst is called when doing top-level substitutions. +-- Here we expect that the free vars of the range of the +-- substitution will be empty. +mkTopTvSubst :: [(TyVar, Type)] -> TvSubst +mkTopTvSubst prs = TvSubst emptyInScopeSet (mkVarEnv prs) + +zipTopTvSubst :: [TyVar] -> [Type] -> TvSubst +zipTopTvSubst tyvars tys +#ifdef DEBUG + | length tyvars /= length tys + = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst + | otherwise +#endif + = TvSubst emptyInScopeSet (zipTyEnv tyvars tys) + +zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv +zipTyEnv tyvars tys +#ifdef DEBUG + | length tyvars /= length tys + = pprTrace "mkTopTvSubst" (ppr tyvars $$ ppr tys) emptyVarEnv + | otherwise +#endif + = zip_ty_env tyvars tys emptyVarEnv + +-- Later substitutions in the list over-ride earlier ones, +-- but there should be no loops +zip_ty_env [] [] env = env +zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendVarEnv env tv ty) + -- There used to be a special case for when + -- ty == TyVarTy tv + -- (a not-uncommon case) in which case the substitution was dropped. + -- But the type-tidier changes the print-name of a type variable without + -- changing the unique, and that led to a bug. Why? Pre-tidying, we had + -- a type {Foo t}, where Foo is a one-method class. So Foo is really a newtype. + -- And it happened that t was the type variable of the class. Post-tiding, + -- it got turned into {Foo t2}. The ext-core printer expanded this using + -- sourceTypeRep, but that said "Oh, t == t2" because they have the same unique, + -- and so generated a rep type mentioning t not t2. + -- + -- Simplest fix is to nuke the "optimisation" +zip_ty_env tvs tys env = pprTrace "Var/Type length mismatch: " (ppr tvs $$ ppr tys) env +-- zip_ty_env _ _ env = env + +instance Outputable TvSubst where + ppr (TvSubst ins env) + = sep[ ptext SLIT(" ppr ins), + nest 2 (ptext SLIT("Env:") <+> ppr env) ] \end{code} +%************************************************************************ +%* * + Performing type substitutions +%* * +%************************************************************************ + +\begin{code} +substTyWith :: [TyVar] -> [Type] -> Type -> Type +substTyWith tvs tys = ASSERT( length tvs == length tys ) + substTy (zipOpenTvSubst tvs tys) + +substTy :: TvSubst -> Type -> Type +substTy subst ty | isEmptyTvSubst subst = ty + | otherwise = subst_ty subst ty + +substTys :: TvSubst -> [Type] -> [Type] +substTys subst tys | isEmptyTvSubst subst = tys + | otherwise = map (subst_ty subst) tys + +substTheta :: TvSubst -> ThetaType -> ThetaType +substTheta subst theta + | isEmptyTvSubst subst = theta + | otherwise = map (substPred subst) theta + +substPred :: TvSubst -> PredType -> PredType +substPred subst (IParam n ty) = IParam n (subst_ty subst ty) +substPred subst (ClassP clas tys) = ClassP clas (map (subst_ty subst) tys) + +deShadowTy :: TyVarSet -> Type -> Type -- Remove any nested binders mentioning tvs +deShadowTy tvs ty + = subst_ty (mkTvSubst in_scope emptyTvSubstEnv) ty + where + in_scope = mkInScopeSet tvs + +-- Note that the in_scope set is poked only if we hit a forall +-- so it may often never be fully computed +subst_ty subst ty + = go ty + where + go (TyVarTy tv) = substTyVar subst tv + go (TyConApp tc tys) = let args = map go tys + in args `seqList` TyConApp tc args + + go (PredTy p) = PredTy $! (substPred subst p) + + go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard the free tyvar note + + go (FunTy arg res) = (FunTy $! (go arg)) $! (go res) + go (AppTy fun arg) = mkAppTy (go fun) $! (go arg) + -- The mkAppTy smart constructor is important + -- we might be replacing (a Int), represented with App + -- by [Int], represented with TyConApp + go (ForAllTy tv ty) = case substTyVarBndr subst tv of + (subst', tv') -> ForAllTy tv' $! (subst_ty subst' ty) + +substTyVar :: TvSubst -> TyVar -> Type +substTyVar subst tv + = case lookupTyVar subst tv of + Nothing -> TyVarTy tv + Just ty' -> ty' -- See Note [Apply Once] + +lookupTyVar :: TvSubst -> TyVar -> Maybe Type +lookupTyVar (TvSubst in_scope env) tv = lookupVarEnv env tv + +substTyVarBndr :: TvSubst -> TyVar -> (TvSubst, TyVar) +substTyVarBndr subst@(TvSubst in_scope env) old_var + | old_var == new_var -- No need to clone + -- But we *must* zap any current substitution for the variable. + -- For example: + -- (\x.e) with id_subst = [x |-> e'] + -- Here we must simply zap the substitution for x + -- + -- The new_id isn't cloned, but it may have a different type + -- etc, so we must return it, not the old id + = (TvSubst (in_scope `extendInScopeSet` new_var) + (delVarEnv env old_var), + new_var) + + | otherwise -- The new binder is in scope so + -- we'd better rename it away from the in-scope variables + -- Extending the substitution to do this renaming also + -- has the (correct) effect of discarding any existing + -- substitution for that variable + = (TvSubst (in_scope `extendInScopeSet` new_var) + (extendVarEnv env old_var (TyVarTy new_var)), + new_var) + where + new_var = uniqAway in_scope old_var + -- The uniqAway part makes sure the new variable is not already in scope +\end{code}