% % (c) The University of Glasgow 2006 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcType]{Types used in the typechecker} This module provides the Type interface for front-end parts of the compiler. These parts * treat "source types" as opaque: newtypes, and predicates are meaningful. * look through usage types The "tc" prefix is for "TypeChecker", because the type checker is the principal client. \begin{code} module TcType ( -------------------------------- -- Types TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType, TcTyVar, TcTyVarSet, TcKind, BoxyTyVar, BoxySigmaType, BoxyRhoType, BoxyThetaType, BoxyType, -------------------------------- -- MetaDetails UserTypeCtxt(..), pprUserTypeCtxt, TcTyVarDetails(..), BoxInfo(..), pprTcTyVarDetails, MetaDetails(Flexi, Indirect), SkolemInfo(..), pprSkolTvBinding, pprSkolInfo, isImmutableTyVar, isSkolemTyVar, isMetaTyVar, isBoxyTyVar, isSigTyVar, isExistentialTyVar, isTyConableTyVar, metaTvRef, isFlexi, isIndirect, isRuntimeUnk, isUnk, -------------------------------- -- Builders mkPhiTy, mkSigmaTy, -------------------------------- -- Splitters -- These are important because they do not look through newtypes tcView, tcSplitForAllTys, tcSplitPhiTy, tcSplitPredFunTy_maybe, tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, tcSplitFunTysN, tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs, tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, repSplitAppTy_maybe, tcInstHeadTyNotSynonym, tcInstHeadTyAppAllTyVars, tcGetTyVar_maybe, tcGetTyVar, tcSplitSigmaTy, tcMultiSplitSigmaTy, --------------------------------- -- Predicates. -- Again, newtypes are opaque tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, tcEqTypeX, eqKind, isSigmaTy, isOverloadedTy, isRigidTy, isBoxyTy, isDoubleTy, isFloatTy, isIntTy, isWordTy, isStringTy, isIntegerTy, isBoolTy, isUnitTy, isCharTy, isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy, isOpenSynTyConApp, --------------------------------- -- Misc type manipulators deNoteType, tyClsNamesOfType, tyClsNamesOfDFunHead, getDFunTyKey, --------------------------------- -- Predicate types getClassPredTys_maybe, getClassPredTys, isClassPred, isTyVarClassPred, isEqPred, mkDictTy, tcSplitPredTy_maybe, isPredTy, isDictTy, isDictLikeTy, tcSplitDFunTy, tcSplitDFunHead, predTyUnique, mkClassPred, isInheritablePred, isIPPred, isRefineableTy, isRefineablePred, --------------------------------- -- Foreign import and export isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool isFFIImportResultTy, -- :: DynFlags -> Type -> Bool isFFIExportResultTy, -- :: Type -> Bool isFFIExternalTy, -- :: Type -> Bool isFFIDynArgumentTy, -- :: Type -> Bool isFFIDynResultTy, -- :: Type -> Bool isFFIPrimArgumentTy, -- :: DynFlags -> Type -> Bool isFFIPrimResultTy, -- :: DynFlags -> Type -> Bool isFFILabelTy, -- :: Type -> Bool isFFIDotnetTy, -- :: DynFlags -> Type -> Bool isFFIDotnetObjTy, -- :: Type -> Bool isFFITy, -- :: Type -> Bool isFunPtrTy, -- :: Type -> Bool tcSplitIOType_maybe, -- :: Type -> Maybe Type -------------------------------- -- Rexported from Type Kind, -- Stuff to do with kinds is insensitive to pre/post Tc unliftedTypeKind, liftedTypeKind, argTypeKind, openTypeKind, mkArrowKind, mkArrowKinds, isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind, isSubArgTypeKind, isSubKind, splitKindFunTys, defaultKind, kindVarRef, mkKindVar, Type, PredType(..), ThetaType, mkForAllTy, mkForAllTys, mkFunTy, mkFunTys, zipFunTys, mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys, mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys, -- Type substitutions TvSubst(..), -- Representation visible to a few friends TvSubstEnv, emptyTvSubst, substEqSpec, mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst, getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar, extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv, substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr, isUnLiftedType, -- Source types are always lifted isUnboxedTupleType, -- Ditto isPrimitiveType, tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes, tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, tidySkolemTyVar, typeKind, tidyKind, tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta, tcTyVarsOfType, tcTyVarsOfTypes, tcTyVarsOfPred, exactTyVarsOfType, exactTyVarsOfTypes, pprKind, pprParendKind, pprType, pprParendType, pprTypeApp, pprTyThingCategory, pprPred, pprTheta, pprThetaArrow, pprClassPred ) where #include "HsVersions.h" -- friends: import TypeRep import DataCon import Class import Var import ForeignCall import VarSet import Type import Coercion import TyCon -- others: import DynFlags import Name import NameSet import VarEnv import PrelNames import TysWiredIn import BasicTypes import Util import Maybes import ListSetOps import Outputable import FastString import Data.IORef \end{code} %************************************************************************ %* * \subsection{Types} %* * %************************************************************************ The type checker divides the generic Type world into the following more structured beasts: sigma ::= forall tyvars. phi -- A sigma type is a qualified type -- -- Note that even if 'tyvars' is empty, theta -- may not be: e.g. (?x::Int) => Int -- Note that 'sigma' is in prenex form: -- all the foralls are at the front. -- A 'phi' type has no foralls to the right of -- an arrow phi :: theta => rho rho ::= sigma -> rho | tau -- A 'tau' type has no quantification anywhere -- Note that the args of a type constructor must be taus tau ::= tyvar | tycon tau_1 .. tau_n | tau_1 tau_2 | tau_1 -> tau_2 -- In all cases, a (saturated) type synonym application is legal, -- provided it expands to the required form. \begin{code} type TcTyVar = TyVar -- Used only during type inference type TcType = Type -- A TcType can have mutable type variables -- Invariant on ForAllTy in TcTypes: -- forall a. T -- a cannot occur inside a MutTyVar in T; that is, -- T is "flattened" before quantifying over a -- These types do not have boxy type variables in them type TcPredType = PredType type TcThetaType = ThetaType type TcSigmaType = TcType type TcRhoType = TcType type TcTauType = TcType type TcKind = Kind type TcTyVarSet = TyVarSet -- These types may have boxy type variables in them type BoxyTyVar = TcTyVar type BoxyRhoType = TcType type BoxyThetaType = TcThetaType type BoxySigmaType = TcType type BoxyType = TcType \end{code} %************************************************************************ %* * \subsection{TyVarDetails} %* * %************************************************************************ TyVarDetails gives extra info about type variables, used during type checking. It's attached to mutable type variables only. It's knot-tied back to Var.lhs. There is no reason in principle why Var.lhs shouldn't actually have the definition, but it "belongs" here. Note [Signature skolems] ~~~~~~~~~~~~~~~~~~~~~~~~ Consider this x :: [a] y :: b (x,y,z) = ([y,z], z, head x) Here, x and y have type sigs, which go into the environment. We used to instantiate their types with skolem constants, and push those types into the RHS, so we'd typecheck the RHS with type ( [a*], b*, c ) where a*, b* are skolem constants, and c is an ordinary meta type varible. The trouble is that the occurrences of z in the RHS force a* and b* to be the *same*, so we can't make them into skolem constants that don't unify with each other. Alas. One solution would be insist that in the above defn the programmer uses the same type variable in both type signatures. But that takes explanation. The alternative (currently implemented) is to have a special kind of skolem constant, SigTv, which can unify with other SigTvs. These are *not* treated as righd for the purposes of GADTs. And they are used *only* for pattern bindings and mutually recursive function bindings. See the function TcBinds.tcInstSig, and its use_skols parameter. \begin{code} -- A TyVarDetails is inside a TyVar data TcTyVarDetails = SkolemTv SkolemInfo -- A skolem constant | MetaTv BoxInfo (IORef MetaDetails) data BoxInfo = BoxTv -- The contents is a (non-boxy) sigma-type -- That is, this MetaTv is a "box" | TauTv -- The contents is a (non-boxy) tau-type -- That is, this MetaTv is an ordinary unification variable | SigTv SkolemInfo -- A variant of TauTv, except that it should not be -- unified with a type, only with a type variable -- SigTvs are only distinguished to improve error messages -- see Note [Signature skolems] -- The MetaDetails, if filled in, will -- always be another SigTv or a SkolemTv -- INVARIANTS: -- A TauTv is always filled in with a tau-type, which -- never contains any BoxTvs, nor any ForAlls -- -- However, a BoxTv can contain a type that contains further BoxTvs -- Notably, when typechecking an explicit list, say [e1,e2], with -- expected type being a box b1, we fill in b1 with (List b2), where -- b2 is another (currently empty) box. data MetaDetails = Flexi -- Flexi type variables unify to become -- Indirects. | Indirect TcType -- INVARIANT: -- For a BoxTv, this type must be non-boxy -- For a TauTv, this type must be a tau-type -- Generally speaking, SkolemInfo should not contain location info -- that is contained in the Name of the tyvar with this SkolemInfo data SkolemInfo = SigSkol UserTypeCtxt -- A skolem that is created by instantiating -- a programmer-supplied type signature -- Location of the binding site is on the TyVar -- The rest are for non-scoped skolems | ClsSkol Class -- Bound at a class decl | InstSkol -- Bound at an instance decl | FamInstSkol -- Bound at a family instance decl | PatSkol DataCon -- An existential type variable bound by a pattern for -- a data constructor with an existential type. E.g. -- data T = forall a. Eq a => MkT a -- f (MkT x) = ... -- The pattern MkT x will allocate an existential type -- variable for 'a'. | ArrowSkol -- An arrow form (see TcArrows) | RuleSkol RuleName -- The LHS of a RULE | GenSkol [TcTyVar] -- Bound when doing a subsumption check for TcType -- (forall tvs. ty) | RuntimeUnkSkol -- a type variable used to represent an unknown -- runtime type (used in the GHCi debugger) | UnkSkol -- Unhelpful info (until I improve it) ------------------------------------- -- UserTypeCtxt describes the places where a -- programmer-written type signature can occur -- Like SkolemInfo, no location info data UserTypeCtxt = FunSigCtxt Name -- Function type signature -- Also used for types in SPECIALISE pragmas | ExprSigCtxt -- Expression type signature | ConArgCtxt Name -- Data constructor argument | TySynCtxt Name -- RHS of a type synonym decl | GenPatCtxt -- Pattern in generic decl -- f{| a+b |} (Inl x) = ... | LamPatSigCtxt -- Type sig in lambda pattern -- f (x::t) = ... | BindPatSigCtxt -- Type sig in pattern binding pattern -- (x::t, y) = e | ResSigCtxt -- Result type sig -- f x :: t = .... | ForSigCtxt Name -- Foreign inport or export signature | DefaultDeclCtxt -- Types in a default declaration | SpecInstCtxt -- SPECIALISE instance pragma | ThBrackCtxt -- Template Haskell type brackets [t| ... |] -- Notes re TySynCtxt -- We allow type synonyms that aren't types; e.g. type List = [] -- -- If the RHS mentions tyvars that aren't in scope, we'll -- quantify over them: -- e.g. type T = a->a -- will become type T = forall a. a->a -- -- With gla-exts that's right, but for H98 we should complain. --------------------------------- -- Kind variables: mkKindName :: Unique -> Name mkKindName unique = mkSystemName unique kind_var_occ kindVarRef :: KindVar -> IORef MetaDetails kindVarRef tc = ASSERT ( isTcTyVar tc ) case tcTyVarDetails tc of MetaTv TauTv ref -> ref _ -> pprPanic "kindVarRef" (ppr tc) mkKindVar :: Unique -> IORef MetaDetails -> KindVar mkKindVar u r = mkTcTyVar (mkKindName u) tySuperKind -- not sure this is right, -- do we need kind vars for -- coercions? (MetaTv TauTv r) kind_var_occ :: OccName -- Just one for all KindVars -- They may be jiggled by tidying kind_var_occ = mkOccName tvName "k" \end{code} %************************************************************************ %* * Pretty-printing %* * %************************************************************************ \begin{code} pprTcTyVarDetails :: TcTyVarDetails -> SDoc -- For debugging pprTcTyVarDetails (SkolemTv _) = ptext (sLit "sk") pprTcTyVarDetails (MetaTv BoxTv _) = ptext (sLit "box") pprTcTyVarDetails (MetaTv TauTv _) = ptext (sLit "tau") pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext (sLit "sig") pprUserTypeCtxt :: UserTypeCtxt -> SDoc pprUserTypeCtxt (FunSigCtxt n) = ptext (sLit "the type signature for") <+> quotes (ppr n) pprUserTypeCtxt ExprSigCtxt = ptext (sLit "an expression type signature") pprUserTypeCtxt (ConArgCtxt c) = ptext (sLit "the type of the constructor") <+> quotes (ppr c) pprUserTypeCtxt (TySynCtxt c) = ptext (sLit "the RHS of the type synonym") <+> quotes (ppr c) pprUserTypeCtxt GenPatCtxt = ptext (sLit "the type pattern of a generic definition") pprUserTypeCtxt ThBrackCtxt = ptext (sLit "a Template Haskell quotation [t|...|]") pprUserTypeCtxt LamPatSigCtxt = ptext (sLit "a pattern type signature") pprUserTypeCtxt BindPatSigCtxt = ptext (sLit "a pattern type signature") pprUserTypeCtxt ResSigCtxt = ptext (sLit "a result type signature") pprUserTypeCtxt (ForSigCtxt n) = ptext (sLit "the foreign declaration for") <+> quotes (ppr n) pprUserTypeCtxt DefaultDeclCtxt = ptext (sLit "a type in a `default' declaration") pprUserTypeCtxt SpecInstCtxt = ptext (sLit "a SPECIALISE instance pragma") -------------------------------- tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar) -- Tidy the type inside a GenSkol, preparatory to printing it tidySkolemTyVar env tv = ASSERT( isTcTyVar tv && (isSkolemTyVar tv || isSigTyVar tv ) ) (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1) where (env1, info1) = case tcTyVarDetails tv of SkolemTv info -> (env1, SkolemTv info') where (env1, info') = tidy_skol_info env info MetaTv (SigTv info) box -> (env1, MetaTv (SigTv info') box) where (env1, info') = tidy_skol_info env info info -> (env, info) tidy_skol_info env (GenSkol tvs ty) = (env2, GenSkol tvs1 ty1) where (env1, tvs1) = tidyOpenTyVars env tvs (env2, ty1) = tidyOpenType env1 ty tidy_skol_info env info = (env, info) pprSkolTvBinding :: TcTyVar -> SDoc -- Print info about the binding of a skolem tyvar, -- or nothing if we don't have anything useful to say pprSkolTvBinding tv = ASSERT ( isTcTyVar tv ) quotes (ppr tv) <+> ppr_details (tcTyVarDetails tv) where ppr_details (MetaTv TauTv _) = ptext (sLit "is a meta type variable") ppr_details (MetaTv BoxTv _) = ptext (sLit "is a boxy type variable") ppr_details (MetaTv (SigTv info) _) = ppr_skol info ppr_details (SkolemTv info) = ppr_skol info ppr_skol UnkSkol = ptext (sLit "is an unknown type variable") -- Unhelpful ppr_skol RuntimeUnkSkol = ptext (sLit "is an unknown runtime type") ppr_skol info = sep [ptext (sLit "is a rigid type variable bound by"), sep [pprSkolInfo info, nest 2 (ptext (sLit "at") <+> ppr (getSrcLoc tv))]] pprSkolInfo :: SkolemInfo -> SDoc pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt pprSkolInfo (ClsSkol cls) = ptext (sLit "the class declaration for") <+> quotes (ppr cls) pprSkolInfo InstSkol = ptext (sLit "the instance declaration") pprSkolInfo FamInstSkol = ptext (sLit "the family instance declaration") pprSkolInfo (RuleSkol name) = ptext (sLit "the RULE") <+> doubleQuotes (ftext name) pprSkolInfo ArrowSkol = ptext (sLit "the arrow form") pprSkolInfo (PatSkol dc) = sep [ptext (sLit "the constructor") <+> quotes (ppr dc)] pprSkolInfo (GenSkol tvs ty) = sep [ptext (sLit "the polymorphic type"), nest 2 (quotes (ppr (mkForAllTys tvs ty)))] -- UnkSkol -- For type variables the others are dealt with by pprSkolTvBinding. -- For Insts, these cases should not happen pprSkolInfo UnkSkol = panic "UnkSkol" pprSkolInfo RuntimeUnkSkol = panic "RuntimeUnkSkol" instance Outputable MetaDetails where ppr Flexi = ptext (sLit "Flexi") ppr (Indirect ty) = ptext (sLit "Indirect") <+> ppr ty \end{code} %************************************************************************ %* * Predicates %* * %************************************************************************ \begin{code} isImmutableTyVar :: TyVar -> Bool isImmutableTyVar tv | isTcTyVar tv = isSkolemTyVar tv | otherwise = True isTyConableTyVar, isSkolemTyVar, isExistentialTyVar, isBoxyTyVar, isMetaTyVar :: TcTyVar -> Bool isTyConableTyVar tv -- True of a meta-type variable that can be filled in -- with a type constructor application; in particular, -- not a SigTv = ASSERT( isTcTyVar tv) case tcTyVarDetails tv of MetaTv BoxTv _ -> True MetaTv TauTv _ -> True MetaTv (SigTv {}) _ -> False SkolemTv {} -> False isSkolemTyVar tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of SkolemTv _ -> True MetaTv _ _ -> False isExistentialTyVar tv -- Existential type variable, bound by a pattern = ASSERT( isTcTyVar tv ) case tcTyVarDetails tv of SkolemTv (PatSkol {}) -> True _ -> False isMetaTyVar tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv _ _ -> True _ -> False isBoxyTyVar tv = ASSERT( isTcTyVar tv ) case tcTyVarDetails tv of MetaTv BoxTv _ -> True _ -> False isSigTyVar :: Var -> Bool isSigTyVar tv = ASSERT( isTcTyVar tv ) case tcTyVarDetails tv of MetaTv (SigTv _) _ -> True _ -> False metaTvRef :: TyVar -> IORef MetaDetails metaTvRef tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv _ ref -> ref _ -> pprPanic "metaTvRef" (ppr tv) isFlexi, isIndirect :: MetaDetails -> Bool isFlexi Flexi = True isFlexi _ = False isIndirect (Indirect _) = True isIndirect _ = False isRuntimeUnk :: TyVar -> Bool isRuntimeUnk x | isTcTyVar x , SkolemTv RuntimeUnkSkol <- tcTyVarDetails x = True | otherwise = False isUnk :: TyVar -> Bool isUnk x | isTcTyVar x , SkolemTv UnkSkol <- tcTyVarDetails x = True | otherwise = False \end{code} %************************************************************************ %* * \subsection{Tau, sigma and rho} %* * %************************************************************************ \begin{code} mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau) mkPhiTy :: [PredType] -> Type -> Type mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta \end{code} @isTauTy@ tests for nested for-alls. It should not be called on a boxy type. \begin{code} isTauTy :: Type -> Bool isTauTy ty | Just ty' <- tcView ty = isTauTy ty' isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) ) True isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc isTauTy (AppTy a b) = isTauTy a && isTauTy b isTauTy (FunTy a b) = isTauTy a && isTauTy b isTauTy (PredTy _) = True -- Don't look through source types isTauTy _ = False isTauTyCon :: TyCon -> Bool -- Returns False for type synonyms whose expansion is a polytype isTauTyCon tc | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc)) | otherwise = True --------------- isBoxyTy :: TcType -> Bool isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty)) isRigidTy :: TcType -> Bool -- A type is rigid if it has no meta type variables in it isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty)) isRefineableTy :: TcType -> (Bool,Bool) -- A type should have type refinements applied to it if it has -- free type variables, and they are all rigid isRefineableTy ty = (null tc_tvs, all isImmutableTyVar tc_tvs) where tc_tvs = varSetElems (tcTyVarsOfType ty) isRefineablePred :: TcPredType -> Bool isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs where tc_tvs = varSetElems (tcTyVarsOfPred pred) --------------- getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to -- construct a dictionary function name getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty' getDFunTyKey (TyVarTy tv) = getOccName tv getDFunTyKey (TyConApp tc _) = getOccName tc getDFunTyKey (AppTy fun _) = getDFunTyKey fun getDFunTyKey (FunTy _ _) = getOccName funTyCon getDFunTyKey (ForAllTy _ t) = getDFunTyKey t getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty) -- PredTy shouldn't happen \end{code} %************************************************************************ %* * \subsection{Expanding and splitting} %* * %************************************************************************ These tcSplit functions are like their non-Tc analogues, but a) they do not look through newtypes b) they do not look through PredTys c) [future] they ignore usage-type annotations However, they are non-monadic and do not follow through mutable type variables. It's up to you to make sure this doesn't matter. \begin{code} tcSplitForAllTys :: Type -> ([TyVar], Type) tcSplitForAllTys ty = split ty ty [] where split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs split _ (ForAllTy tv ty) tvs | not (isCoVar tv) = split ty ty (tv:tvs) split orig_ty _ tvs = (reverse tvs, orig_ty) tcIsForAllTy :: Type -> Bool tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty' tcIsForAllTy (ForAllTy tv _) = not (isCoVar tv) tcIsForAllTy _ = False tcSplitPredFunTy_maybe :: Type -> Maybe (PredType, Type) -- Split off the first predicate argument from a type tcSplitPredFunTy_maybe ty | Just ty' <- tcView ty = tcSplitPredFunTy_maybe ty' tcSplitPredFunTy_maybe (ForAllTy tv ty) | isCoVar tv = Just (coVarPred tv, ty) tcSplitPredFunTy_maybe (FunTy arg res) | Just p <- tcSplitPredTy_maybe arg = Just (p, res) tcSplitPredFunTy_maybe _ = Nothing tcSplitPhiTy :: Type -> (ThetaType, Type) tcSplitPhiTy ty = split ty [] where split ty ts = case tcSplitPredFunTy_maybe ty of Just (pred, ty) -> split ty (pred:ts) Nothing -> (reverse ts, ty) tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type) tcSplitSigmaTy ty = case tcSplitForAllTys ty of (tvs, rho) -> case tcSplitPhiTy rho of (theta, tau) -> (tvs, theta, tau) ----------------------- tcMultiSplitSigmaTy :: TcSigmaType -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D TcSigmaType) -- The rest of the type -- We need a loop here because we are now prepared to entertain -- types like -- f:: forall a. Eq a => forall b. Baz b => tau -- We want to instantiate this to -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)} tcMultiSplitSigmaTy sigma = case (tcSplitSigmaTy sigma) of ([], [], _) -> ([], sigma) (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of (pairs, rest) -> ((tvs,theta):pairs, rest) ----------------------- tcTyConAppTyCon :: Type -> TyCon tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of Just (tc, _) -> tc Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty) tcTyConAppArgs :: Type -> [Type] tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of Just (_, args) -> args Nothing -> pprPanic "tcTyConAppArgs" (pprType ty) tcSplitTyConApp :: Type -> (TyCon, [Type]) tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of Just stuff -> stuff Nothing -> pprPanic "tcSplitTyConApp" (pprType ty) tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type]) tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty' tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys) tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res]) -- Newtypes are opaque, so they may be split -- However, predicates are not treated -- as tycon applications by the type checker tcSplitTyConApp_maybe _ = Nothing ----------------------- tcSplitFunTys :: Type -> ([Type], Type) tcSplitFunTys ty = case tcSplitFunTy_maybe ty of Nothing -> ([], ty) Just (arg,res) -> (arg:args, res') where (args,res') = tcSplitFunTys res tcSplitFunTy_maybe :: Type -> Maybe (Type, Type) tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty' tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res) tcSplitFunTy_maybe _ = Nothing -- Note the (not (isPredTy arg)) guard -- Consider (?x::Int) => Bool -- We don't want to treat this as a function type! -- A concrete example is test tc230: -- f :: () -> (?p :: ()) => () -> () -- -- g = f () () tcSplitFunTysN :: TcRhoType -> Arity -- N: Number of desired args -> ([TcSigmaType], -- Arg types (N or fewer) TcSigmaType) -- The rest of the type tcSplitFunTysN ty n_args | n_args == 0 = ([], ty) | Just (arg,res) <- tcSplitFunTy_maybe ty = case tcSplitFunTysN res (n_args - 1) of (args, res) -> (arg:args, res) | otherwise = ([], ty) tcSplitFunTy :: Type -> (Type, Type) tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty) tcFunArgTy :: Type -> Type tcFunArgTy ty = fst (tcSplitFunTy ty) tcFunResultTy :: Type -> Type tcFunResultTy ty = snd (tcSplitFunTy ty) ----------------------- tcSplitAppTy_maybe :: Type -> Maybe (Type, Type) tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty' tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty tcSplitAppTy :: Type -> (Type, Type) tcSplitAppTy ty = case tcSplitAppTy_maybe ty of Just stuff -> stuff Nothing -> pprPanic "tcSplitAppTy" (pprType ty) tcSplitAppTys :: Type -> (Type, [Type]) tcSplitAppTys ty = go ty [] where go ty args = case tcSplitAppTy_maybe ty of Just (ty', arg) -> go ty' (arg:args) Nothing -> (ty,args) ----------------------- tcGetTyVar_maybe :: Type -> Maybe TyVar tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty' tcGetTyVar_maybe (TyVarTy tv) = Just tv tcGetTyVar_maybe _ = Nothing tcGetTyVar :: String -> Type -> TyVar tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty) tcIsTyVarTy :: Type -> Bool tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty) ----------------------- tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type]) -- Split the type of a dictionary function tcSplitDFunTy ty = case tcSplitSigmaTy ty of { (tvs, theta, tau) -> case tcSplitDFunHead tau of { (clas, tys) -> (tvs, theta, clas, tys) }} tcSplitDFunHead :: Type -> (Class, [Type]) tcSplitDFunHead tau = case tcSplitPredTy_maybe tau of Just (ClassP clas tys) -> (clas, tys) _ -> panic "tcSplitDFunHead" tcInstHeadTyNotSynonym :: Type -> Bool -- Used in Haskell-98 mode, for the argument types of an instance head -- These must not be type synonyms, but everywhere else type synonyms -- are transparent, so we need a special function here tcInstHeadTyNotSynonym ty = case ty of TyConApp tc _ -> not (isSynTyCon tc) _ -> True tcInstHeadTyAppAllTyVars :: Type -> Bool -- Used in Haskell-98 mode, for the argument types of an instance head -- These must be a constructor applied to type variable arguments tcInstHeadTyAppAllTyVars ty = case ty of TyConApp _ tys -> ok tys FunTy arg res -> ok [arg, res] _ -> False where -- Check that all the types are type variables, -- and that each is distinct ok tys = equalLength tvs tys && hasNoDups tvs where tvs = mapCatMaybes get_tv tys get_tv (TyVarTy tv) = Just tv -- through synonyms get_tv _ = Nothing \end{code} %************************************************************************ %* * \subsection{Predicate types} %* * %************************************************************************ \begin{code} tcSplitPredTy_maybe :: Type -> Maybe PredType -- Returns Just for predicates only tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty' tcSplitPredTy_maybe (PredTy p) = Just p tcSplitPredTy_maybe _ = Nothing predTyUnique :: PredType -> Unique predTyUnique (IParam n _) = getUnique (ipNameName n) predTyUnique (ClassP clas _) = getUnique clas predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b)) \end{code} --------------------- Dictionary types --------------------------------- \begin{code} mkClassPred :: Class -> [Type] -> PredType mkClassPred clas tys = ClassP clas tys isClassPred :: PredType -> Bool isClassPred (ClassP _ _) = True isClassPred _ = False isTyVarClassPred :: PredType -> Bool isTyVarClassPred (ClassP _ tys) = all tcIsTyVarTy tys isTyVarClassPred _ = False getClassPredTys_maybe :: PredType -> Maybe (Class, [Type]) getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys) getClassPredTys_maybe _ = Nothing getClassPredTys :: PredType -> (Class, [Type]) getClassPredTys (ClassP clas tys) = (clas, tys) getClassPredTys _ = panic "getClassPredTys" mkDictTy :: Class -> [Type] -> Type mkDictTy clas tys = mkPredTy (ClassP clas tys) isDictTy :: Type -> Bool isDictTy ty | Just ty' <- tcView ty = isDictTy ty' isDictTy (PredTy p) = isClassPred p isDictTy _ = False isDictLikeTy :: Type -> Bool -- Note [Dictionary-like types] isDictLikeTy ty | Just ty' <- tcView ty = isDictTy ty' isDictLikeTy (PredTy p) = isClassPred p isDictLikeTy (TyConApp tc tys) | isTupleTyCon tc = all isDictLikeTy tys isDictLikeTy _ = False \end{code} Note [Dictionary-like types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Being "dictionary-like" means either a dictionary type or a tuple thereof. In GHC 6.10 we build implication constraints which construct such tuples, and if we land up with a binding t :: (C [a], Eq [a]) t = blah then we want to treat t as cheap under "-fdicts-cheap" for example. (Implication constraints are normally inlined, but sadly not if the occurrence is itself inside an INLINE function! Until we revise the handling of implication constraints, that is.) This turned out to be important in getting good arities in DPH code. Example: class C a class D a where { foo :: a -> a } instance C a => D (Maybe a) where { foo x = x } bar :: (C a, C b) => a -> b -> (Maybe a, Maybe b) {-# INLINE bar #-} bar x y = (foo (Just x), foo (Just y)) Then 'bar' should jolly well have arity 4 (two dicts, two args), but we ended up with something like bar = __inline_me__ (\d1,d2. let t :: (D (Maybe a), D (Maybe b)) = ... in \x,y. ) This is all a bit ad-hoc; eg it relies on knowing that implication constraints build tuples. --------------------- Implicit parameters --------------------------------- \begin{code} isIPPred :: PredType -> Bool isIPPred (IParam _ _) = True isIPPred _ = False isInheritablePred :: PredType -> Bool -- Can be inherited by a context. For example, consider -- f x = let g y = (?v, y+x) -- in (g 3 with ?v = 8, -- g 4 with ?v = 9) -- The point is that g's type must be quantifed over ?v: -- g :: (?v :: a) => a -> a -- but it doesn't need to be quantified over the Num a dictionary -- which can be free in g's rhs, and shared by both calls to g isInheritablePred (ClassP _ _) = True isInheritablePred (EqPred _ _) = True isInheritablePred _ = False \end{code} --------------------- Equality predicates --------------------------------- \begin{code} substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)] substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty) | (tv,ty) <- eq_spec] \end{code} %************************************************************************ %* * \subsection{Predicates} %* * %************************************************************************ isSigmaTy returns true of any qualified type. It doesn't *necessarily* have any foralls. E.g. f :: (?x::Int) => Int -> Int \begin{code} isSigmaTy :: Type -> Bool isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty' isSigmaTy (ForAllTy _ _) = True isSigmaTy (FunTy a _) = isPredTy a isSigmaTy _ = False isOverloadedTy :: Type -> Bool -- Yes for a type of a function that might require evidence-passing -- Used only by bindInstsOfLocalFuns/Pats -- NB: be sure to check for type with an equality predicate; hence isCoVar isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty' isOverloadedTy (ForAllTy tv ty) = isCoVar tv || isOverloadedTy ty isOverloadedTy (FunTy a _) = isPredTy a isOverloadedTy _ = False isPredTy :: Type -> Bool -- Belongs in TcType because it does -- not look through newtypes, or predtypes (of course) isPredTy ty | Just ty' <- tcView ty = isPredTy ty' isPredTy (PredTy _) = True isPredTy _ = False \end{code} \begin{code} isFloatTy, isDoubleTy, isIntegerTy, isIntTy, isWordTy, isBoolTy, isUnitTy, isCharTy :: Type -> Bool isFloatTy = is_tc floatTyConKey isDoubleTy = is_tc doubleTyConKey isIntegerTy = is_tc integerTyConKey isIntTy = is_tc intTyConKey isWordTy = is_tc wordTyConKey isBoolTy = is_tc boolTyConKey isUnitTy = is_tc unitTyConKey isCharTy = is_tc charTyConKey isStringTy :: Type -> Bool isStringTy ty = case tcSplitTyConApp_maybe ty of Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty _ -> False is_tc :: Unique -> Type -> Bool -- Newtypes are opaque to this is_tc uniq ty = case tcSplitTyConApp_maybe ty of Just (tc, _) -> uniq == getUnique tc Nothing -> False \end{code} \begin{code} -- NB: Currently used in places where we have already expanded type synonyms; -- hence no 'coreView'. This could, however, be changed without breaking -- any code. isOpenSynTyConApp :: TcTauType -> Bool isOpenSynTyConApp (TyConApp tc tys) = isOpenSynTyCon tc && length tys == tyConArity tc isOpenSynTyConApp _other = False \end{code} %************************************************************************ %* * \subsection{Misc} %* * %************************************************************************ \begin{code} deNoteType :: Type -> Type -- Remove all *outermost* type synonyms and other notes deNoteType ty | Just ty' <- tcView ty = deNoteType ty' deNoteType ty = ty \end{code} \begin{code} tcTyVarsOfType :: Type -> TcTyVarSet -- Just the *TcTyVars* free in the type -- (Types.tyVarsOfTypes finds all free TyVars) tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv else emptyVarSet tcTyVarsOfType (TyConApp _ tys) = tcTyVarsOfTypes tys tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar) `unionVarSet` tcTyVarsOfTyVar tyvar -- We do sometimes quantify over skolem TcTyVars tcTyVarsOfTyVar :: TcTyVar -> TyVarSet tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv) | otherwise = emptyVarSet tcTyVarsOfTypes :: [Type] -> TyVarSet tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys tcTyVarsOfPred :: PredType -> TyVarSet tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2 \end{code} Note [Silly type synonym] ~~~~~~~~~~~~~~~~~~~~~~~~~ Consider type T a = Int What are the free tyvars of (T x)? Empty, of course! Here's the example that Ralf Laemmel showed me: foo :: (forall a. C u a -> C u a) -> u mappend :: Monoid u => u -> u -> u bar :: Monoid u => u bar = foo (\t -> t `mappend` t) We have to generalise at the arg to f, and we don't want to capture the constraint (Monad (C u a)) because it appears to mention a. Pretty silly, but it was useful to him. exactTyVarsOfType is used by the type checker to figure out exactly which type variables are mentioned in a type. It's also used in the smart-app checking code --- see TcExpr.tcIdApp On the other hand, consider a *top-level* definition f = (\x -> x) :: T a -> T a If we don't abstract over 'a' it'll get fixed to GHC.Prim.Any, and then if we have an application like (f "x") we get a confusing error message involving Any. So the conclusion is this: when generalising - at top level use tyVarsOfType - in nested bindings use exactTyVarsOfType See Trac #1813 for example. \begin{code} exactTyVarsOfType :: TcType -> TyVarSet -- Find the free type variables (of any kind) -- but *expand* type synonyms. See Note [Silly type synonym] above. exactTyVarsOfType ty = go ty where go ty | Just ty' <- tcView ty = go ty' -- This is the key line go (TyVarTy tv) = unitVarSet tv go (TyConApp _ tys) = exactTyVarsOfTypes tys go (PredTy ty) = go_pred ty go (FunTy arg res) = go arg `unionVarSet` go res go (AppTy fun arg) = go fun `unionVarSet` go arg go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar `unionVarSet` go_tv tyvar go_pred (IParam _ ty) = go ty go_pred (ClassP _ tys) = exactTyVarsOfTypes tys go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar) | otherwise = emptyVarSet exactTyVarsOfTypes :: [TcType] -> TyVarSet exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys \end{code} Find the free tycons and classes of a type. This is used in the front end of the compiler. \begin{code} tyClsNamesOfType :: Type -> NameSet tyClsNamesOfType (TyVarTy _) = emptyNameSet tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys tyClsNamesOfType (PredTy (IParam _ ty)) = tyClsNamesOfType ty tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg tyClsNamesOfType (ForAllTy _ ty) = tyClsNamesOfType ty tyClsNamesOfTypes :: [Type] -> NameSet tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys tyClsNamesOfDFunHead :: Type -> NameSet -- Find the free type constructors and classes -- of the head of the dfun instance type -- The 'dfun_head_type' is because of -- instance Foo a => Baz T where ... -- The decl is an orphan if Baz and T are both not locally defined, -- even if Foo *is* locally defined tyClsNamesOfDFunHead dfun_ty = case tcSplitSigmaTy dfun_ty of (_, _, head_ty) -> tyClsNamesOfType head_ty \end{code} %************************************************************************ %* * \subsection[TysWiredIn-ext-type]{External types} %* * %************************************************************************ The compiler's foreign function interface supports the passing of a restricted set of types as arguments and results (the restricting factor being the ) \begin{code} tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI) -- (isIOType t) returns Just (IO,t',co) -- if co : t ~ IO t' -- returns Nothing otherwise tcSplitIOType_maybe ty = case tcSplitTyConApp_maybe ty of -- This split absolutely has to be a tcSplit, because we must -- see the IO type; and it's a newtype which is transparent to splitTyConApp. Just (io_tycon, [io_res_ty]) | io_tycon `hasKey` ioTyConKey -> Just (io_tycon, io_res_ty, IdCo) Just (tc, tys) | not (isRecursiveTyCon tc) , Just (ty, co1) <- instNewTyCon_maybe tc tys -- Newtypes that require a coercion are ok -> case tcSplitIOType_maybe ty of Nothing -> Nothing Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2) _ -> Nothing isFFITy :: Type -> Bool -- True for any TyCon that can possibly be an arg or result of an FFI call isFFITy ty = checkRepTyCon legalFFITyCon ty isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool -- Checks for valid argument type for a 'foreign import' isFFIArgumentTy dflags safety ty = checkRepTyCon (legalOutgoingTyCon dflags safety) ty isFFIExternalTy :: Type -> Bool -- Types that are allowed as arguments of a 'foreign export' isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty isFFIImportResultTy :: DynFlags -> Type -> Bool isFFIImportResultTy dflags ty = checkRepTyCon (legalFIResultTyCon dflags) ty isFFIExportResultTy :: Type -> Bool isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty isFFIDynArgumentTy :: Type -> Bool -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr, -- or a newtype of either. isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey] isFFIDynResultTy :: Type -> Bool -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr, -- or a newtype of either. isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey] isFFILabelTy :: Type -> Bool -- The type of a foreign label must be Ptr, FunPtr, Addr, -- or a newtype of either. isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey] isFFIPrimArgumentTy :: DynFlags -> Type -> Bool -- Checks for valid argument type for a 'foreign import prim' -- Currently they must all be simple unlifted types. isFFIPrimArgumentTy dflags ty = checkRepTyCon (legalFIPrimArgTyCon dflags) ty isFFIPrimResultTy :: DynFlags -> Type -> Bool -- Checks for valid result type for a 'foreign import prim' -- Currently it must be an unlifted type, including unboxed tuples. isFFIPrimResultTy dflags ty = checkRepTyCon (legalFIPrimResultTyCon dflags) ty isFFIDotnetTy :: DynFlags -> Type -> Bool isFFIDotnetTy dflags ty = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc || isFFIDotnetObjTy ty || isStringTy ty)) ty -- NB: isStringTy used to look through newtypes, but -- it no longer does so. May need to adjust isFFIDotNetTy -- if we do want to look through newtypes. isFFIDotnetObjTy :: Type -> Bool isFFIDotnetObjTy ty = checkRepTyCon check_tc t_ty where (_, t_ty) = tcSplitForAllTys ty check_tc tc = getName tc == objectTyConName isFunPtrTy :: Type -> Bool isFunPtrTy = checkRepTyConKey [funPtrTyConKey] checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool -- Look through newtypes, but *not* foralls -- Should work even for recursive newtypes -- eg Manuel had: newtype T = MkT (Ptr T) checkRepTyCon check_tc ty = go [] ty where go rec_nts ty | Just (tc,tys) <- splitTyConApp_maybe ty = case carefullySplitNewType_maybe rec_nts tc tys of Just (rec_nts', ty') -> go rec_nts' ty' Nothing -> check_tc tc | otherwise = False checkRepTyConKey :: [Unique] -> Type -> Bool -- Like checkRepTyCon, but just looks at the TyCon key checkRepTyConKey keys = checkRepTyCon (\tc -> tyConUnique tc `elem` keys) \end{code} ---------------------------------------------- These chaps do the work; they are not exported ---------------------------------------------- \begin{code} legalFEArgTyCon :: TyCon -> Bool legalFEArgTyCon tc -- It's illegal to make foreign exports that take unboxed -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000 = boxedMarshalableTyCon tc legalFIResultTyCon :: DynFlags -> TyCon -> Bool legalFIResultTyCon dflags tc | tc == unitTyCon = True | otherwise = marshalableTyCon dflags tc legalFEResultTyCon :: TyCon -> Bool legalFEResultTyCon tc | tc == unitTyCon = True | otherwise = boxedMarshalableTyCon tc legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool -- Checks validity of types going from Haskell -> external world legalOutgoingTyCon dflags _ tc = marshalableTyCon dflags tc legalFFITyCon :: TyCon -> Bool -- True for any TyCon that can possibly be an arg or result of an FFI call legalFFITyCon tc = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon marshalableTyCon :: DynFlags -> TyCon -> Bool marshalableTyCon dflags tc = (dopt Opt_UnliftedFFITypes dflags && isUnLiftedTyCon tc && not (isUnboxedTupleTyCon tc) && case tyConPrimRep tc of -- Note [Marshalling VoidRep] VoidRep -> False _ -> True) || boxedMarshalableTyCon tc boxedMarshalableTyCon :: TyCon -> Bool boxedMarshalableTyCon tc = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey , int32TyConKey, int64TyConKey , wordTyConKey, word8TyConKey, word16TyConKey , word32TyConKey, word64TyConKey , floatTyConKey, doubleTyConKey , ptrTyConKey, funPtrTyConKey , charTyConKey , stablePtrTyConKey , boolTyConKey ] legalFIPrimArgTyCon :: DynFlags -> TyCon -> Bool -- Check args of 'foreign import prim', only allow simple unlifted types. -- Strictly speaking it is unnecessary to ban unboxed tuples here since -- currently they're of the wrong kind to use in function args anyway. legalFIPrimArgTyCon dflags tc = dopt Opt_UnliftedFFITypes dflags && isUnLiftedTyCon tc && not (isUnboxedTupleTyCon tc) legalFIPrimResultTyCon :: DynFlags -> TyCon -> Bool -- Check result type of 'foreign import prim'. Allow simple unlifted -- types and also unboxed tuple result types '... -> (# , , #)' legalFIPrimResultTyCon dflags tc = dopt Opt_UnliftedFFITypes dflags && isUnLiftedTyCon tc && (isUnboxedTupleTyCon tc || case tyConPrimRep tc of -- Note [Marshalling VoidRep] VoidRep -> False _ -> True) \end{code} Note [Marshalling VoidRep] ~~~~~~~~~~~~~~~~~~~~~~~~~~ We don't treat State# (whose PrimRep is VoidRep) as marshalable. In turn that means you can't write foreign import foo :: Int -> State# RealWorld Reason: the back end falls over with panic "primRepHint:VoidRep"; and there is no compelling reason to permit it