% % (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} {-# LANGUAGE CPP #-} module TcType ( -------------------------------- -- Types TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType, TcTyVar, TcTyVarSet, TcKind, TcCoVar, -- Untouchables Untouchables(..), noUntouchables, pushUntouchables, strictlyDeeperThan, sameDepthAs, fskUntouchables, -------------------------------- -- MetaDetails UserTypeCtxt(..), pprUserTypeCtxt, pprSigCtxt, TcTyVarDetails(..), pprTcTyVarDetails, vanillaSkolemTv, superSkolemTv, MetaDetails(Flexi, Indirect), MetaInfo(..), isImmutableTyVar, isSkolemTyVar, isMetaTyVar, isMetaTyVarTy, isTyVarTy, isSigTyVar, isOverlappableTyVar, isTyConableTyVar, isFskTyVar, isFmvTyVar, isFlattenTyVar, isAmbiguousTyVar, metaTvRef, metaTyVarInfo, isFlexi, isIndirect, isRuntimeUnkSkol, isTypeVar, isKindVar, metaTyVarUntouchables, setMetaTyVarUntouchables, metaTyVarUntouchables_maybe, isTouchableMetaTyVar, isTouchableOrFmv, isFloatedTouchableMetaTyVar, canUnifyWithPolyType, -------------------------------- -- Builders mkPhiTy, mkSigmaTy, mkTcEqPred, -------------------------------- -- 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, tcDeepSplitSigmaTy_maybe, --------------------------------- -- Predicates. -- Again, newtypes are opaque eqType, eqTypes, eqPred, cmpType, cmpTypes, cmpPred, eqTypeX, pickyEqType, tcEqType, tcEqKind, isSigmaTy, isRhoTy, isOverloadedTy, isDoubleTy, isFloatTy, isIntTy, isWordTy, isStringTy, isIntegerTy, isBoolTy, isUnitTy, isCharTy, isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy, isPredTy, isTyVarClassPred, --------------------------------- -- Misc type manipulators deNoteType, occurCheckExpand, OccCheckResult(..), orphNamesOfType, orphNamesOfDFunHead, orphNamesOfCo, orphNamesOfTypes, orphNamesOfCoCon, getDFunTyKey, evVarPred_maybe, evVarPred, --------------------------------- -- Predicate types mkMinimalBySCs, transSuperClasses, immSuperClasses, -- * Finding type instances tcTyFamInsts, -- * Finding "exact" (non-dead) type variables exactTyVarsOfType, exactTyVarsOfTypes, --------------------------------- -- Foreign import and export isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool isFFIImportResultTy, -- :: DynFlags -> Type -> Bool isFFIExportResultTy, -- :: Type -> Bool isFFIExternalTy, -- :: Type -> Bool isFFIDynTy, -- :: Type -> Type -> Bool isFFIPrimArgumentTy, -- :: DynFlags -> Type -> Bool isFFIPrimResultTy, -- :: DynFlags -> Type -> Bool isFFILabelTy, -- :: Type -> Bool isFFITy, -- :: Type -> Bool isFunPtrTy, -- :: Type -> Bool tcSplitIOType_maybe, -- :: Type -> Maybe Type -------------------------------- -- Rexported from Kind Kind, typeKind, unliftedTypeKind, liftedTypeKind, openTypeKind, constraintKind, mkArrowKind, mkArrowKinds, isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind, tcIsSubKind, splitKindFunTys, defaultKind, -------------------------------- -- Rexported from Type Type, PredType, ThetaType, mkForAllTy, mkForAllTys, mkFunTy, mkFunTys, zipFunTys, mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys, mkTyVarTy, mkTyVarTys, mkTyConTy, isClassPred, isEqPred, isIPPred, mkClassPred, isDictLikeTy, tcSplitDFunTy, tcSplitDFunHead, mkEqPred, -- Type substitutions TvSubst(..), -- Representation visible to a few friends TvSubstEnv, emptyTvSubst, mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst, unionTvSubst, getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, Type.lookupTyVar, Type.extendTvSubst, Type.substTyVarBndr, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv, Type.substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, isUnLiftedType, -- Source types are always lifted isUnboxedTupleType, -- Ditto isPrimitiveType, tyVarsOfType, tyVarsOfTypes, closeOverKinds, tcTyVarsOfType, tcTyVarsOfTypes, pprKind, pprParendKind, pprSigmaType, pprType, pprParendType, pprTypeApp, pprTyThingCategory, pprTheta, pprThetaArrowTy, pprClassPred ) where #include "HsVersions.h" -- friends: import Kind import TypeRep import Class import Var import ForeignCall import VarSet import Coercion import Type import TyCon import CoAxiom -- others: import DynFlags import Name -- hiding (varName) -- We use this to make dictionaries for type literals. -- Perhaps there's a better way to do this? import NameSet import VarEnv import PrelNames import TysWiredIn import BasicTypes import Util import Maybes import ListSetOps import Outputable import FastString import ErrUtils( Validity(..), isValid ) import Data.IORef import Control.Monad (liftM, ap) #if __GLASGOW_HASKELL__ < 709 import Control.Applicative (Applicative(..)) #endif \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 TcCoVar = CoVar -- Used only during type inference; mutable 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 -- Note [TcRhoType] type TcTauType = TcType type TcKind = Kind type TcTyVarSet = TyVarSet \end{code} Note [TcRhoType] ~~~~~~~~~~~~~~~~ A TcRhoType has no foralls or contexts at the top, or to the right of an arrow YES (forall a. a->a) -> Int NO forall a. a -> Int NO Eq a => a -> a NO Int -> forall a. a -> Int %************************************************************************ %* * \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 f :: forall a. [a] -> Int f (x::b : xs) = 3 Here 'b' is a lexically scoped type variable, but it turns out to be the same as the skolem 'a'. So we have a special kind of skolem constant, SigTv, which can unify with other SigTvs. They are used *only* for pattern type signatures. Similarly consider data T (a:k1) = MkT (S a) data S (b:k2) = MkS (T b) When doing kind inference on {S,T} we don't want *skolems* for k1,k2, because they end up unifying; we want those SigTvs again. Note [ReturnTv] ~~~~~~~~~~~~~~~ We sometimes want to convert a checking algorithm into an inference algorithm. An easy way to do this is to "check" that a term has a metavariable as a type. But, we must be careful to allow that metavariable to unify with *anything*. (Well, anything that doesn't fail an occurs-check.) This is what ReturnTv means. For example, if we have (undefined :: (forall a. TF1 a ~ TF2 a => a)) x we'll call (tcInfer . tcExpr) on the function expression. tcInfer will create a ReturnTv to represent the expression's type. We really need this ReturnTv to become set to (forall a. TF1 a ~ TF2 a => a) despite the fact that this type mentions type families and is a polytype. However, we must also be careful to make sure that the ReturnTvs really always do get unified with something -- we don't want these floating around in the solver. So, we check after running the checker to make sure the ReturnTv is filled. If it's not, we set it to a TauTv. We can't ASSERT that no ReturnTvs hit the solver, because they can if there's, say, a kind error that stops checkTauTvUpdate from working. This happens in test case typecheck/should_fail/T5570, for example. See also the commentary on #9404. \begin{code} -- A TyVarDetails is inside a TyVar data TcTyVarDetails = SkolemTv -- A skolem Bool -- True <=> this skolem type variable can be overlapped -- when looking up instances -- See Note [Binding when looking up instances] in InstEnv | FlatSkol -- A flatten-skolem. It stands for the TcType, and zonking TcType -- will replace it by that type. -- See Note [The flattening story] in TcFlatten | RuntimeUnk -- Stands for an as-yet-unknown type in the GHCi -- interactive context | MetaTv { mtv_info :: MetaInfo , mtv_ref :: IORef MetaDetails , mtv_untch :: Untouchables } -- See Note [Untouchable type variables] vanillaSkolemTv, superSkolemTv :: TcTyVarDetails -- See Note [Binding when looking up instances] in InstEnv vanillaSkolemTv = SkolemTv False -- Might be instantiated superSkolemTv = SkolemTv True -- Treat this as a completely distinct type ----------------------------- data MetaDetails = Flexi -- Flexi type variables unify to become Indirects | Indirect TcType instance Outputable MetaDetails where ppr Flexi = ptext (sLit "Flexi") ppr (Indirect ty) = ptext (sLit "Indirect") <+> ppr ty data MetaInfo = TauTv -- This MetaTv is an ordinary unification variable -- A TauTv is always filled in with a tau-type, which -- never contains any ForAlls | ReturnTv -- Can unify with *anything*. Used to convert a -- type "checking" algorithm into a type inference algorithm. -- See Note [ReturnTv] | SigTv -- 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 | FlatMetaTv -- A flatten meta-tyvar -- It is a meta-tyvar, but it is always untouchable, with level 0 -- See Note [The flattening story] in TcFlatten ------------------------------------- -- UserTypeCtxt describes the origin of the polymorphic type -- in the places where we need to an expression has that type data UserTypeCtxt = FunSigCtxt Name -- Function type signature -- Also used for types in SPECIALISE pragmas | InfSigCtxt Name -- Inferred type for function | ExprSigCtxt -- Expression type signature | ConArgCtxt Name -- Data constructor argument | TySynCtxt Name -- RHS of a type synonym decl | PatSigCtxt -- Type sig in pattern -- eg f (x::t) = ... -- or (x::t, y) = e | RuleSigCtxt Name -- LHS of a RULE forall -- RULE "foo" forall (x :: a -> a). f (Just x) = ... | ResSigCtxt -- Result type sig -- f x :: t = .... | ForSigCtxt Name -- Foreign import or export signature | DefaultDeclCtxt -- Types in a default declaration | InstDeclCtxt -- An instance declaration | SpecInstCtxt -- SPECIALISE instance pragma | ThBrackCtxt -- Template Haskell type brackets [t| ... |] | GenSigCtxt -- Higher-rank or impredicative situations -- e.g. (f e) where f has a higher-rank type -- We might want to elaborate this | GhciCtxt -- GHCi command :kind | ClassSCCtxt Name -- Superclasses of a class | SigmaCtxt -- Theta part of a normal for-all type -- f :: => a -> a | DataTyCtxt Name -- Theta part of a data decl -- data => T a = MkT a \end{code} -- 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. %************************************************************************ %* * Untoucable type variables %* * %************************************************************************ Note [Untouchable type variables] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * Each unification variable (MetaTv) and each Implication has a level number (of type Untouchables) * INVARIANTS. In a tree of Implications, (ImplicInv) The level number of an Implication is STRICTLY GREATER THAN that of its parent (MetaTvInv) The level number of a unification variable is LESS THAN OR EQUAL TO that of its parent implication * A unification variable is *touchable* if its level number is EQUAL TO that of its immediate parent implication. * INVARIANT (GivenInv) The free variables of the ic_given of an implication are all untouchable; ie their level numbers are LESS THAN the ic_untch of the implication Note [Skolem escape prevention] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We only unify touchable unification variables. Because of (MetaTvInv), there can be no occurrences of he variable further out, so the unification can't cause the kolems to escape. Example: data T = forall a. MkT a (a->Int) f x (MkT v f) = length [v,x] We decide (x::alpha), and generate an implication like [1]forall a. (a ~ alpha[0]) But we must not unify alpha:=a, because the skolem would escape. For the cases where we DO want to unify, we rely on floating the equality. Example (with same T) g x (MkT v f) = x && True We decide (x::alpha), and generate an implication like [1]forall a. (Bool ~ alpha[0]) We do NOT unify directly, bur rather float out (if the constraint does not mention 'a') to get (Bool ~ alpha[0]) /\ [1]forall a.() and NOW we can unify alpha. The same idea of only unifying touchables solves another problem. Suppose we had (F Int ~ uf[0]) /\ [1](forall a. C a => F Int ~ beta[1]) In this example, beta is touchable inside the implication. The first solveFlatWanteds step leaves 'uf' un-unified. Then we move inside the implication where a new constraint uf ~ beta emerges. If we (wrongly) spontaneously solved it to get uf := beta, the whole implication disappears but when we pop out again we are left with (F Int ~ uf) which will be unified by our final zonking stage and uf will get unified *once more* to (F Int). \begin{code} newtype Untouchables = Untouchables Int deriving( Eq ) -- See Note [Untouchable type variables] for what this Int is fskUntouchables :: Untouchables fskUntouchables = Untouchables 0 -- 0 = Outside the outermost level: -- flatten skolems noUntouchables :: Untouchables noUntouchables = Untouchables 1 -- 1 = outermost level pushUntouchables :: Untouchables -> Untouchables pushUntouchables (Untouchables us) = Untouchables (us+1) strictlyDeeperThan :: Untouchables -> Untouchables -> Bool strictlyDeeperThan (Untouchables tv_untch) (Untouchables ctxt_untch) = tv_untch > ctxt_untch sameDepthAs :: Untouchables -> Untouchables -> Bool sameDepthAs (Untouchables ctxt_untch) (Untouchables tv_untch) = ctxt_untch == tv_untch -- NB: invariant ctxt_untch >= tv_untch -- So <= would be equivalent checkTouchableInvariant :: Untouchables -> Untouchables -> Bool -- Checks (MetaTvInv) from Note [Untouchable type variables] checkTouchableInvariant (Untouchables ctxt_untch) (Untouchables tv_untch) = ctxt_untch >= tv_untch instance Outputable Untouchables where ppr (Untouchables us) = ppr us \end{code} %************************************************************************ %* * Pretty-printing %* * %************************************************************************ \begin{code} pprTcTyVarDetails :: TcTyVarDetails -> SDoc -- For debugging pprTcTyVarDetails (SkolemTv True) = ptext (sLit "ssk") pprTcTyVarDetails (SkolemTv False) = ptext (sLit "sk") pprTcTyVarDetails (RuntimeUnk {}) = ptext (sLit "rt") pprTcTyVarDetails (FlatSkol {}) = ptext (sLit "fsk") pprTcTyVarDetails (MetaTv { mtv_info = info, mtv_untch = untch }) = pp_info <> colon <> ppr untch where pp_info = case info of ReturnTv -> ptext (sLit "ret") TauTv -> ptext (sLit "tau") SigTv -> ptext (sLit "sig") FlatMetaTv -> ptext (sLit "fuv") pprUserTypeCtxt :: UserTypeCtxt -> SDoc pprUserTypeCtxt (InfSigCtxt n) = ptext (sLit "the inferred type for") <+> quotes (ppr n) pprUserTypeCtxt (FunSigCtxt n) = ptext (sLit "the type signature for") <+> quotes (ppr n) pprUserTypeCtxt (RuleSigCtxt n) = ptext (sLit "a RULE 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 ThBrackCtxt = ptext (sLit "a Template Haskell quotation [t|...|]") pprUserTypeCtxt PatSigCtxt = 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 InstDeclCtxt = ptext (sLit "an instance declaration") pprUserTypeCtxt SpecInstCtxt = ptext (sLit "a SPECIALISE instance pragma") pprUserTypeCtxt GenSigCtxt = ptext (sLit "a type expected by the context") pprUserTypeCtxt GhciCtxt = ptext (sLit "a type in a GHCi command") pprUserTypeCtxt (ClassSCCtxt c) = ptext (sLit "the super-classes of class") <+> quotes (ppr c) pprUserTypeCtxt SigmaCtxt = ptext (sLit "the context of a polymorphic type") pprUserTypeCtxt (DataTyCtxt tc) = ptext (sLit "the context of the data type declaration for") <+> quotes (ppr tc) pprSigCtxt :: UserTypeCtxt -> SDoc -> SDoc -> SDoc -- (pprSigCtxt ctxt ) -- prints In the type signature for 'f': -- f :: -- The is either empty or "the ambiguity check for" pprSigCtxt ctxt extra pp_ty = sep [ ptext (sLit "In") <+> extra <+> pprUserTypeCtxt ctxt <> colon , nest 2 (pp_sig ctxt) ] where pp_sig (FunSigCtxt n) = pp_n_colon n pp_sig (ConArgCtxt n) = pp_n_colon n pp_sig (ForSigCtxt n) = pp_n_colon n pp_sig _ = pp_ty pp_n_colon n = pprPrefixOcc n <+> dcolon <+> pp_ty \end{code} %************************************************************************ %* * Finding type family instances %* * %************************************************************************ \begin{code} -- | Finds outermost type-family applications occuring in a type, -- after expanding synonyms. tcTyFamInsts :: Type -> [(TyCon, [Type])] tcTyFamInsts ty | Just exp_ty <- tcView ty = tcTyFamInsts exp_ty tcTyFamInsts (TyVarTy _) = [] tcTyFamInsts (TyConApp tc tys) | isTypeFamilyTyCon tc = [(tc, tys)] | otherwise = concat (map tcTyFamInsts tys) tcTyFamInsts (LitTy {}) = [] tcTyFamInsts (FunTy ty1 ty2) = tcTyFamInsts ty1 ++ tcTyFamInsts ty2 tcTyFamInsts (AppTy ty1 ty2) = tcTyFamInsts ty1 ++ tcTyFamInsts ty2 tcTyFamInsts (ForAllTy _ ty) = tcTyFamInsts ty \end{code} %************************************************************************ %* * The "exact" free variables of a type %* * %************************************************************************ 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 :: Type -> 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 (LitTy {}) = emptyVarSet 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 exactTyVarsOfTypes :: [Type] -> TyVarSet exactTyVarsOfTypes = mapUnionVarSet exactTyVarsOfType \end{code} %************************************************************************ %* * Predicates %* * %************************************************************************ \begin{code} isTouchableOrFmv :: Untouchables -> TcTyVar -> Bool isTouchableOrFmv ctxt_untch tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv { mtv_untch = tv_untch, mtv_info = info } -> ASSERT2( checkTouchableInvariant ctxt_untch tv_untch, ppr tv $$ ppr tv_untch $$ ppr ctxt_untch ) case info of FlatMetaTv -> True _ -> tv_untch `sameDepthAs` ctxt_untch _ -> False isTouchableMetaTyVar :: Untouchables -> TcTyVar -> Bool isTouchableMetaTyVar ctxt_untch tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv { mtv_untch = tv_untch } -> ASSERT2( checkTouchableInvariant ctxt_untch tv_untch, ppr tv $$ ppr tv_untch $$ ppr ctxt_untch ) tv_untch `sameDepthAs` ctxt_untch _ -> False isFloatedTouchableMetaTyVar :: Untouchables -> TcTyVar -> Bool isFloatedTouchableMetaTyVar ctxt_untch tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv { mtv_untch = tv_untch } -> tv_untch `strictlyDeeperThan` ctxt_untch _ -> False isImmutableTyVar :: TyVar -> Bool isImmutableTyVar tv | isTcTyVar tv = isSkolemTyVar tv | otherwise = True isTyConableTyVar, isSkolemTyVar, isOverlappableTyVar, isMetaTyVar, isAmbiguousTyVar, isFmvTyVar, isFskTyVar, isFlattenTyVar :: 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 { mtv_info = SigTv } -> False _ -> True isFmvTyVar tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv { mtv_info = FlatMetaTv } -> True _ -> False -- | True of both given and wanted flatten-skolems (fak and usk) isFlattenTyVar tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of FlatSkol {} -> True MetaTv { mtv_info = FlatMetaTv } -> True _ -> False -- | True of FlatSkol skolems only isFskTyVar tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of FlatSkol {} -> True _ -> False isSkolemTyVar tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv {} -> False _other -> True isOverlappableTyVar tv = ASSERT( isTcTyVar tv ) case tcTyVarDetails tv of SkolemTv overlappable -> overlappable _ -> False isMetaTyVar tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv {} -> True _ -> False -- isAmbiguousTyVar is used only when reporting type errors -- It picks out variables that are unbound, namely meta -- type variables and the RuntimUnk variables created by -- RtClosureInspect.zonkRTTIType. These are "ambiguous" in -- the sense that they stand for an as-yet-unknown type isAmbiguousTyVar tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv {} -> True RuntimeUnk {} -> True _ -> False isMetaTyVarTy :: TcType -> Bool isMetaTyVarTy (TyVarTy tv) = isMetaTyVar tv isMetaTyVarTy _ = False metaTyVarInfo :: TcTyVar -> MetaInfo metaTyVarInfo tv = ASSERT( isTcTyVar tv ) case tcTyVarDetails tv of MetaTv { mtv_info = info } -> info _ -> pprPanic "metaTyVarInfo" (ppr tv) metaTyVarUntouchables :: TcTyVar -> Untouchables metaTyVarUntouchables tv = ASSERT( isTcTyVar tv ) case tcTyVarDetails tv of MetaTv { mtv_untch = untch } -> untch _ -> pprPanic "metaTyVarUntouchables" (ppr tv) metaTyVarUntouchables_maybe :: TcTyVar -> Maybe Untouchables metaTyVarUntouchables_maybe tv = ASSERT( isTcTyVar tv ) case tcTyVarDetails tv of MetaTv { mtv_untch = untch } -> Just untch _ -> Nothing setMetaTyVarUntouchables :: TcTyVar -> Untouchables -> TcTyVar setMetaTyVarUntouchables tv untch = ASSERT( isTcTyVar tv ) case tcTyVarDetails tv of details@(MetaTv {}) -> setTcTyVarDetails tv (details { mtv_untch = untch }) _ -> pprPanic "metaTyVarUntouchables" (ppr tv) isSigTyVar :: Var -> Bool isSigTyVar tv = ASSERT( isTcTyVar tv ) case tcTyVarDetails tv of MetaTv { mtv_info = SigTv } -> True _ -> False metaTvRef :: TyVar -> IORef MetaDetails metaTvRef tv = ASSERT2( isTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv { mtv_ref = ref } -> ref _ -> pprPanic "metaTvRef" (ppr tv) isFlexi, isIndirect :: MetaDetails -> Bool isFlexi Flexi = True isFlexi _ = False isIndirect (Indirect _) = True isIndirect _ = False isRuntimeUnkSkol :: TyVar -> Bool -- Called only in TcErrors; see Note [Runtime skolems] there isRuntimeUnkSkol x | isTcTyVar x, RuntimeUnk <- 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 mkFunTy ty theta mkTcEqPred :: TcType -> TcType -> Type -- During type checking we build equalities between -- type variables with OpenKind or ArgKind. Ultimately -- they will all settle, but we want the equality predicate -- itself to have kind '*'. I think. -- -- But for now we call mkTyConApp, not mkEqPred, because the invariants -- of the latter might not be satisfied during type checking. -- Notably when we form an equalty (a : OpenKind) ~ (Int : *) -- -- But this is horribly delicate: what about type variables -- that turn out to be bound to Int#? mkTcEqPred ty1 ty2 = mkTyConApp eqTyCon [k, ty1, ty2] where k = typeKind ty1 \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 _) = True isTauTy (LitTy {}) = 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 (ForAllTy {}) = False isTauTyCon :: TyCon -> Bool -- Returns False for type synonyms whose expansion is a polytype isTauTyCon tc | Just (_, rhs) <- synTyConDefn_maybe tc = isTauTy rhs | otherwise = True --------------- 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 (LitTy x) = getDFunTyLitKey x getDFunTyKey (AppTy fun _) = getDFunTyKey fun getDFunTyKey (FunTy _ _) = getOccName funTyCon getDFunTyKey (ForAllTy _ t) = getDFunTyKey t getDFunTyLitKey :: TyLit -> OccName getDFunTyLitKey (NumTyLit n) = mkOccName Name.varName (show n) getDFunTyLitKey (StrTyLit n) = mkOccName Name.varName (show n) -- hm \end{code} %************************************************************************ %* * \subsection{Expanding and splitting} %* * %************************************************************************ These tcSplit functions are like their non-Tc analogues, but *) they do not look through newtypes 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 = 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 {}) = True 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 (FunTy arg res) | isPredTy arg = Just (arg, 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) ----------------------- tcDeepSplitSigmaTy_maybe :: TcSigmaType -> Maybe ([TcType], [TyVar], ThetaType, TcSigmaType) -- Looks for a *non-trivial* quantified type, under zero or more function arrows -- By "non-trivial" we mean either tyvars or constraints are non-empty tcDeepSplitSigmaTy_maybe ty | Just (arg_ty, res_ty) <- tcSplitFunTy_maybe ty , Just (arg_tys, tvs, theta, rho) <- tcDeepSplitSigmaTy_maybe res_ty = Just (arg_ty:arg_tys, tvs, theta, rho) | (tvs, theta, rho) <- tcSplitSigmaTy ty , not (null tvs && null theta) = Just ([], tvs, theta, rho) | otherwise = Nothing ----------------------- 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 typeKind 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 = isJust (tcGetTyVar_maybe ty) ----------------------- tcSplitDFunTy :: Type -> ([TyVar], [Type], Class, [Type]) -- Split the type of a dictionary function -- We don't use tcSplitSigmaTy, because a DFun may (with NDP) -- have non-Pred arguments, such as -- df :: forall m. (forall b. Eq b => Eq (m b)) -> C m -- -- Also NB splitFunTys, not tcSplitFunTys; -- the latter specifically stops at PredTy arguments, -- and we don't want to do that here tcSplitDFunTy ty = case tcSplitForAllTys ty of { (tvs, rho) -> case splitFunTys rho of { (theta, tau) -> case tcSplitDFunHead tau of { (clas, tys) -> (tvs, theta, clas, tys) }}} tcSplitDFunHead :: Type -> (Class, [Type]) tcSplitDFunHead = getClassPredTys 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 (isTypeSynonymTyCon 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. -- But we allow kind instantiations. tcInstHeadTyAppAllTyVars ty | Just ty' <- tcView ty -- Look through synonyms = tcInstHeadTyAppAllTyVars ty' | otherwise = case ty of TyConApp _ tys -> ok (filter (not . isKind) tys) -- avoid kinds 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 = mapMaybe get_tv tys get_tv (TyVarTy tv) = Just tv -- through synonyms get_tv _ = Nothing \end{code} \begin{code} tcEqKind :: TcKind -> TcKind -> Bool tcEqKind = tcEqType tcEqType :: TcType -> TcType -> Bool -- tcEqType is a proper, sensible type-equality function, that does -- just what you'd expect The function Type.eqType (currently) has a -- grotesque hack that makes OpenKind = *, and that is NOT what we -- want in the type checker! Otherwise, for example, TcCanonical.reOrient -- thinks the LHS and RHS have the same kinds, when they don't, and -- fails to re-orient. That in turn caused Trac #8553. tcEqType ty1 ty2 = go init_env ty1 ty2 where init_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType ty1 `unionVarSet` tyVarsOfType ty2)) go env t1 t2 | Just t1' <- tcView t1 = go env t1' t2 | Just t2' <- tcView t2 = go env t1 t2' go env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 == rnOccR env tv2 go _ (LitTy lit1) (LitTy lit2) = lit1 == lit2 go env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = go env (tyVarKind tv1) (tyVarKind tv2) && go (rnBndr2 env tv1 tv2) t1 t2 go env (AppTy s1 t1) (AppTy s2 t2) = go env s1 s2 && go env t1 t2 go env (FunTy s1 t1) (FunTy s2 t2) = go env s1 s2 && go env t1 t2 go env (TyConApp tc1 ts1) (TyConApp tc2 ts2) = (tc1 == tc2) && gos env ts1 ts2 go _ _ _ = False gos _ [] [] = True gos env (t1:ts1) (t2:ts2) = go env t1 t2 && gos env ts1 ts2 gos _ _ _ = False pickyEqType :: TcType -> TcType -> Bool -- Check when two types _look_ the same, _including_ synonyms. -- So (pickyEqType String [Char]) returns False pickyEqType ty1 ty2 = go init_env ty1 ty2 where init_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType ty1 `unionVarSet` tyVarsOfType ty2)) go env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 == rnOccR env tv2 go _ (LitTy lit1) (LitTy lit2) = lit1 == lit2 go env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = go env (tyVarKind tv1) (tyVarKind tv2) && go (rnBndr2 env tv1 tv2) t1 t2 go env (AppTy s1 t1) (AppTy s2 t2) = go env s1 s2 && go env t1 t2 go env (FunTy s1 t1) (FunTy s2 t2) = go env s1 s2 && go env t1 t2 go env (TyConApp tc1 ts1) (TyConApp tc2 ts2) = (tc1 == tc2) && gos env ts1 ts2 go _ _ _ = False gos _ [] [] = True gos env (t1:ts1) (t2:ts2) = go env t1 t2 && gos env ts1 ts2 gos _ _ _ = False \end{code} Note [Occurs check expansion] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (occurCheckExpand tv xi) expands synonyms in xi just enough to get rid of occurrences of tv outside type function arguments, if that is possible; otherwise, it returns Nothing. For example, suppose we have type F a b = [a] Then occurCheckExpand b (F Int b) = Just [Int] but occurCheckExpand a (F a Int) = Nothing We don't promise to do the absolute minimum amount of expanding necessary, but we try not to do expansions we don't need to. We prefer doing inner expansions first. For example, type F a b = (a, Int, a, [a]) type G b = Char We have occurCheckExpand b (F (G b)) = F Char even though we could also expand F to get rid of b. See also Note [occurCheckExpand] in TcCanonical \begin{code} data OccCheckResult a = OC_OK a | OC_Forall | OC_NonTyVar | OC_Occurs instance Functor OccCheckResult where fmap = liftM instance Applicative OccCheckResult where pure = return (<*>) = ap instance Monad OccCheckResult where return x = OC_OK x OC_OK x >>= k = k x OC_Forall >>= _ = OC_Forall OC_NonTyVar >>= _ = OC_NonTyVar OC_Occurs >>= _ = OC_Occurs occurCheckExpand :: DynFlags -> TcTyVar -> Type -> OccCheckResult Type -- See Note [Occurs check expansion] -- Check whether -- a) the given variable occurs in the given type. -- b) there is a forall in the type (unless we have -XImpredicativeTypes -- or it's a ReturnTv -- c) if it's a SigTv, ty should be a tyvar -- -- We may have needed to do some type synonym unfolding in order to -- get rid of the variable (or forall), so we also return the unfolded -- version of the type, which is guaranteed to be syntactically free -- of the given type variable. If the type is already syntactically -- free of the variable, then the same type is returned. occurCheckExpand dflags tv ty | MetaTv { mtv_info = SigTv } <- details = go_sig_tv ty | fast_check ty = return ty | otherwise = go ty where details = ASSERT2( isTcTyVar tv, ppr tv ) tcTyVarDetails tv impredicative = canUnifyWithPolyType dflags details (tyVarKind tv) -- Check 'ty' is a tyvar, or can be expanded into one go_sig_tv ty@(TyVarTy {}) = OC_OK ty go_sig_tv ty | Just ty' <- tcView ty = go_sig_tv ty' go_sig_tv _ = OC_NonTyVar -- True => fine fast_check (LitTy {}) = True fast_check (TyVarTy tv') = tv /= tv' fast_check (TyConApp _ tys) = all fast_check tys fast_check (FunTy arg res) = fast_check arg && fast_check res fast_check (AppTy fun arg) = fast_check fun && fast_check arg fast_check (ForAllTy tv' ty) = impredicative && fast_check (tyVarKind tv') && (tv == tv' || fast_check ty) go t@(TyVarTy tv') | tv == tv' = OC_Occurs | otherwise = return t go ty@(LitTy {}) = return ty go (AppTy ty1 ty2) = do { ty1' <- go ty1 ; ty2' <- go ty2 ; return (mkAppTy ty1' ty2') } go (FunTy ty1 ty2) = do { ty1' <- go ty1 ; ty2' <- go ty2 ; return (mkFunTy ty1' ty2') } go ty@(ForAllTy tv' body_ty) | not impredicative = OC_Forall | not (fast_check (tyVarKind tv')) = OC_Occurs -- Can't expand away the kinds unless we create -- fresh variables which we don't want to do at this point. -- In principle fast_check might fail because of a for-all -- but we don't yet have poly-kinded tyvars so I'm not -- going to worry about that now | tv == tv' = return ty | otherwise = do { body' <- go body_ty ; return (ForAllTy tv' body') } -- For a type constructor application, first try expanding away the -- offending variable from the arguments. If that doesn't work, next -- see if the type constructor is a type synonym, and if so, expand -- it and try again. go ty@(TyConApp tc tys) = case do { tys <- mapM go tys; return (mkTyConApp tc tys) } of OC_OK ty -> return ty -- First try to eliminate the tyvar from the args bad | Just ty' <- tcView ty -> go ty' | otherwise -> bad -- Failing that, try to expand a synonym canUnifyWithPolyType :: DynFlags -> TcTyVarDetails -> TcKind -> Bool canUnifyWithPolyType dflags details kind = case details of MetaTv { mtv_info = ReturnTv } -> True -- See Note [ReturnTv] MetaTv { mtv_info = SigTv } -> False MetaTv { mtv_info = TauTv } -> xopt Opt_ImpredicativeTypes dflags || isOpenTypeKind kind -- Note [OpenTypeKind accepts foralls] _other -> True -- We can have non-meta tyvars in given constraints \end{code} Note [OpenTypeKind accepts foralls] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is a common paradigm: foo :: (forall a. a -> a) -> Int foo = error "urk" To make this work we need to instantiate 'error' with a polytype. A similar case is bar :: Bool -> (forall a. a->a) -> Int bar True = \x. (x 3) bar False = error "urk" Here we need to instantiate 'error' with a polytype. But 'error' has an OpenTypeKind type variable, precisely so that we can instantiate it with Int#. So we also allow such type variables to be instantiate with foralls. It's a bit of a hack, but seems straightforward. %************************************************************************ %* * \subsection{Predicate types} %* * %************************************************************************ Deconstructors and tests on predicate types \begin{code} isTyVarClassPred :: PredType -> Bool isTyVarClassPred ty = case getClassPredTys_maybe ty of Just (_, tys) -> all isTyVarTy tys _ -> False evVarPred_maybe :: EvVar -> Maybe PredType evVarPred_maybe v = if isPredTy ty then Just ty else Nothing where ty = varType v evVarPred :: EvVar -> PredType evVarPred var | debugIsOn = case evVarPred_maybe var of Just pred -> pred Nothing -> pprPanic "tcEvVarPred" (ppr var <+> ppr (varType var)) | otherwise = varType var \end{code} Superclasses \begin{code} mkMinimalBySCs :: [PredType] -> [PredType] -- Remove predicates that can be deduced from others by superclasses mkMinimalBySCs ptys = [ ploc | ploc <- ptys , ploc `not_in_preds` rec_scs ] where rec_scs = concatMap trans_super_classes ptys not_in_preds p ps = not (any (eqPred p) ps) trans_super_classes pred -- Superclasses of pred, excluding pred itself = case classifyPredType pred of ClassPred cls tys -> transSuperClasses cls tys TuplePred ts -> concatMap trans_super_classes ts _ -> [] transSuperClasses :: Class -> [Type] -> [PredType] transSuperClasses cls tys -- Superclasses of (cls tys), -- excluding (cls tys) itself = concatMap trans_sc (immSuperClasses cls tys) where trans_sc :: PredType -> [PredType] -- (trans_sc p) returns (p : p's superclasses) trans_sc p = case classifyPredType p of ClassPred cls tys -> p : transSuperClasses cls tys TuplePred ps -> concatMap trans_sc ps _ -> [p] immSuperClasses :: Class -> [Type] -> [PredType] immSuperClasses cls tys = substTheta (zipTopTvSubst tyvars tys) sc_theta where (tyvars,sc_theta,_,_) = classBigSig cls \end{code} %************************************************************************ %* * \subsection{Predicates} %* * %************************************************************************ \begin{code} isSigmaTy :: TcType -> Bool -- isSigmaTy returns true of any qualified type. It doesn't -- *necessarily* have any foralls. E.g -- f :: (?x::Int) => Int -> Int isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty' isSigmaTy (ForAllTy _ _) = True isSigmaTy (FunTy a _) = isPredTy a isSigmaTy _ = False isRhoTy :: TcType -> Bool -- True of TcRhoTypes; see Note [TcRhoType] isRhoTy ty | Just ty' <- tcView ty = isRhoTy ty' isRhoTy (ForAllTy {}) = False isRhoTy (FunTy a r) = not (isPredTy a) && isRhoTy r isRhoTy _ = True isOverloadedTy :: Type -> Bool -- Yes for a type of a function that might require evidence-passing -- Used only by bindLocalMethods isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty' isOverloadedTy (ForAllTy _ ty) = isOverloadedTy ty isOverloadedTy (FunTy a _) = isPredTy a isOverloadedTy _ = False \end{code} \begin{code} isFloatTy, isDoubleTy, isIntegerTy, isIntTy, isWordTy, isBoolTy, isUnitTy, isCharTy, isAnyTy :: 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 isAnyTy = is_tc anyTyConKey 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} %************************************************************************ %* * \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 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 (LitTy {}) = emptyVarSet 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 -- We do sometimes quantify over skolem TcTyVars tcTyVarsOfTypes :: [Type] -> TyVarSet tcTyVarsOfTypes = mapUnionVarSet tcTyVarsOfType \end{code} Find the free tycons and classes of a type. This is used in the front end of the compiler. \begin{code} orphNamesOfTyCon :: TyCon -> NameSet orphNamesOfTyCon tycon = unitNameSet (getName tycon) `unionNameSets` case tyConClass_maybe tycon of Nothing -> emptyNameSet Just cls -> unitNameSet (getName cls) orphNamesOfType :: Type -> NameSet orphNamesOfType ty | Just ty' <- tcView ty = orphNamesOfType ty' -- Look through type synonyms (Trac #4912) orphNamesOfType (TyVarTy _) = emptyNameSet orphNamesOfType (LitTy {}) = emptyNameSet orphNamesOfType (TyConApp tycon tys) = orphNamesOfTyCon tycon `unionNameSets` orphNamesOfTypes tys orphNamesOfType (FunTy arg res) = orphNamesOfTyCon funTyCon -- NB! See Trac #8535 `unionNameSets` orphNamesOfType arg `unionNameSets` orphNamesOfType res orphNamesOfType (AppTy fun arg) = orphNamesOfType fun `unionNameSets` orphNamesOfType arg orphNamesOfType (ForAllTy _ ty) = orphNamesOfType ty orphNamesOfThings :: (a -> NameSet) -> [a] -> NameSet orphNamesOfThings f = foldr (unionNameSets . f) emptyNameSet orphNamesOfTypes :: [Type] -> NameSet orphNamesOfTypes = orphNamesOfThings orphNamesOfType orphNamesOfDFunHead :: 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 orphNamesOfDFunHead dfun_ty = case tcSplitSigmaTy dfun_ty of (_, _, head_ty) -> orphNamesOfType head_ty orphNamesOfCo :: Coercion -> NameSet orphNamesOfCo (Refl _ ty) = orphNamesOfType ty orphNamesOfCo (TyConAppCo _ tc cos) = unitNameSet (getName tc) `unionNameSets` orphNamesOfCos cos orphNamesOfCo (AppCo co1 co2) = orphNamesOfCo co1 `unionNameSets` orphNamesOfCo co2 orphNamesOfCo (ForAllCo _ co) = orphNamesOfCo co orphNamesOfCo (CoVarCo _) = emptyNameSet orphNamesOfCo (AxiomInstCo con _ cos) = orphNamesOfCoCon con `unionNameSets` orphNamesOfCos cos orphNamesOfCo (UnivCo _ ty1 ty2) = orphNamesOfType ty1 `unionNameSets` orphNamesOfType ty2 orphNamesOfCo (SymCo co) = orphNamesOfCo co orphNamesOfCo (TransCo co1 co2) = orphNamesOfCo co1 `unionNameSets` orphNamesOfCo co2 orphNamesOfCo (NthCo _ co) = orphNamesOfCo co orphNamesOfCo (LRCo _ co) = orphNamesOfCo co orphNamesOfCo (InstCo co ty) = orphNamesOfCo co `unionNameSets` orphNamesOfType ty orphNamesOfCo (SubCo co) = orphNamesOfCo co orphNamesOfCo (AxiomRuleCo _ ts cs) = orphNamesOfTypes ts `unionNameSets` orphNamesOfCos cs orphNamesOfCos :: [Coercion] -> NameSet orphNamesOfCos = orphNamesOfThings orphNamesOfCo orphNamesOfCoCon :: CoAxiom br -> NameSet orphNamesOfCoCon (CoAxiom { co_ax_tc = tc, co_ax_branches = branches }) = orphNamesOfTyCon tc `unionNameSets` orphNamesOfCoAxBranches branches orphNamesOfCoAxBranches :: BranchList CoAxBranch br -> NameSet orphNamesOfCoAxBranches = brListFoldr (unionNameSets . orphNamesOfCoAxBranch) emptyNameSet orphNamesOfCoAxBranch :: CoAxBranch -> NameSet orphNamesOfCoAxBranch (CoAxBranch { cab_lhs = lhs, cab_rhs = rhs }) = orphNamesOfTypes lhs `unionNameSets` orphNamesOfType rhs \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) -- (tcSplitIOType_maybe t) returns Just (IO,t',co) -- if co : t ~ IO t' -- returns Nothing otherwise tcSplitIOType_maybe ty = case tcSplitTyConApp_maybe ty of Just (io_tycon, [io_res_ty]) | io_tycon `hasKey` ioTyConKey -> Just (io_tycon, io_res_ty) _ -> Nothing isFFITy :: Type -> Bool -- True for any TyCon that can possibly be an arg or result of an FFI call isFFITy ty = isValid (checkRepTyCon legalFFITyCon ty empty) isFFIArgumentTy :: DynFlags -> Safety -> Type -> Validity -- Checks for valid argument type for a 'foreign import' isFFIArgumentTy dflags safety ty = checkRepTyCon (legalOutgoingTyCon dflags safety) ty empty isFFIExternalTy :: Type -> Validity -- Types that are allowed as arguments of a 'foreign export' isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty empty isFFIImportResultTy :: DynFlags -> Type -> Validity isFFIImportResultTy dflags ty = checkRepTyCon (legalFIResultTyCon dflags) ty empty isFFIExportResultTy :: Type -> Validity isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty empty isFFIDynTy :: Type -> Type -> Validity -- The type in a foreign import dynamic must be Ptr, FunPtr, or a newtype of -- either, and the wrapped function type must be equal to the given type. -- We assume that all types have been run through normaliseFfiType, so we don't -- need to worry about expanding newtypes here. isFFIDynTy expected ty -- Note [Foreign import dynamic] -- In the example below, expected would be 'CInt -> IO ()', while ty would -- be 'FunPtr (CDouble -> IO ())'. | Just (tc, [ty']) <- splitTyConApp_maybe ty , tyConUnique tc `elem` [ptrTyConKey, funPtrTyConKey] , eqType ty' expected = IsValid | otherwise = NotValid (vcat [ ptext (sLit "Expected: Ptr/FunPtr") <+> pprParendType expected <> comma , ptext (sLit " Actual:") <+> ppr ty ]) isFFILabelTy :: Type -> Validity -- The type of a foreign label must be Ptr, FunPtr, or a newtype of either. isFFILabelTy ty = checkRepTyCon ok ty extra where ok tc = tc `hasKey` funPtrTyConKey || tc `hasKey` ptrTyConKey extra = ptext (sLit "A foreign-imported address (via &foo) must have type (Ptr a) or (FunPtr a)") isFFIPrimArgumentTy :: DynFlags -> Type -> Validity -- Checks for valid argument type for a 'foreign import prim' -- Currently they must all be simple unlifted types, or the well-known type -- Any, which can be used to pass the address to a Haskell object on the heap to -- the foreign function. isFFIPrimArgumentTy dflags ty | isAnyTy ty = IsValid | otherwise = checkRepTyCon (legalFIPrimArgTyCon dflags) ty empty isFFIPrimResultTy :: DynFlags -> Type -> Validity -- 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 empty isFunPtrTy :: Type -> Bool isFunPtrTy ty = isValid (checkRepTyCon (`hasKey` funPtrTyConKey) ty empty) -- normaliseFfiType gets run before checkRepTyCon, so we don't -- need to worry about looking through newtypes or type functions -- here; that's already been taken care of. checkRepTyCon :: (TyCon -> Bool) -> Type -> SDoc -> Validity checkRepTyCon check_tc ty extra = case splitTyConApp_maybe ty of Just (tc, tys) | isNewTyCon tc -> NotValid (hang msg 2 (mk_nt_reason tc tys $$ nt_fix)) | check_tc tc -> IsValid | otherwise -> NotValid (msg $$ extra) Nothing -> NotValid (quotes (ppr ty) <+> ptext (sLit "is not a data type") $$ extra) where msg = quotes (ppr ty) <+> ptext (sLit "cannot be marshalled in a foreign call") mk_nt_reason tc tys | null tys = ptext (sLit "because its data construtor is not in scope") | otherwise = ptext (sLit "because the data construtor for") <+> quotes (ppr tc) <+> ptext (sLit "is not in scope") nt_fix = ptext (sLit "Possible fix: import the data constructor to bring it into scope") \end{code} Note [Foreign import dynamic] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A dynamic stub must be of the form 'FunPtr ft -> ft' where ft is any foreign type. Similarly, a wrapper stub must be of the form 'ft -> IO (FunPtr ft)'. We use isFFIDynTy to check whether a signature is well-formed. For example, given a (illegal) declaration like: foreign import ccall "dynamic" foo :: FunPtr (CDouble -> IO ()) -> CInt -> IO () isFFIDynTy will compare the 'FunPtr' type 'CDouble -> IO ()' with the curried result type 'CInt -> IO ()', and return False, as they are not equal. ---------------------------------------------- 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 = True | tc == unitTyCon = True | otherwise = boxedMarshalableTyCon tc marshalableTyCon :: DynFlags -> TyCon -> Bool marshalableTyCon dflags tc | (xopt Opt_UnliftedFFITypes dflags && isUnLiftedTyCon tc && not (isUnboxedTupleTyCon tc) && case tyConPrimRep tc of -- Note [Marshalling VoidRep] VoidRep -> False _ -> True) = True | otherwise = 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 ] = True | otherwise = False 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 | xopt Opt_UnliftedFFITypes dflags && isUnLiftedTyCon tc && not (isUnboxedTupleTyCon tc) = True | otherwise = False legalFIPrimResultTyCon :: DynFlags -> TyCon -> Bool -- Check result type of 'foreign import prim'. Allow simple unlifted -- types and also unboxed tuple result types '... -> (# , , #)' legalFIPrimResultTyCon dflags tc | xopt Opt_UnliftedFFITypes dflags && isUnLiftedTyCon tc && (isUnboxedTupleTyCon tc || case tyConPrimRep tc of -- Note [Marshalling VoidRep] VoidRep -> False _ -> True) = True | otherwise = False \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