-- (c) The University of Glasgow 2006 -- (c) The GRASP/AQUA Project, Glasgow University, 1998 -- -- Type - public interface {-# LANGUAGE CPP, FlexibleContexts #-} {-# OPTIONS_GHC -fno-warn-orphans #-} -- | Main functions for manipulating types and type-related things module Type ( -- Note some of this is just re-exports from TyCon.. -- * Main data types representing Types -- $type_classification -- $representation_types TyThing(..), Type, ArgFlag(..), KindOrType, PredType, ThetaType, Var, TyVar, isTyVar, TyCoVar, TyBinder, TyVarBinder, KnotTied, -- ** Constructing and deconstructing types mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, repGetTyVar_maybe, getCastedTyVar_maybe, tyVarKind, mkAppTy, mkAppTys, splitAppTy, splitAppTys, repSplitAppTys, splitAppTy_maybe, repSplitAppTy_maybe, tcRepSplitAppTy_maybe, mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe, splitFunTys, funResultTy, funArgTy, mkTyConApp, mkTyConTy, tyConAppTyCon_maybe, tyConAppTyConPicky_maybe, tyConAppArgs_maybe, tyConAppTyCon, tyConAppArgs, splitTyConApp_maybe, splitTyConApp, tyConAppArgN, nextRole, tcRepSplitTyConApp_maybe, tcSplitTyConApp_maybe, splitListTyConApp_maybe, repSplitTyConApp_maybe, mkForAllTy, mkForAllTys, mkInvForAllTys, mkSpecForAllTys, mkVisForAllTys, mkInvForAllTy, splitForAllTys, splitForAllTyVarBndrs, splitForAllTy_maybe, splitForAllTy, splitPiTy_maybe, splitPiTy, splitPiTys, mkPiTy, mkPiTys, mkTyConBindersPreferAnon, mkLamType, mkLamTypes, piResultTy, piResultTys, applyTysX, dropForAlls, mkNumLitTy, isNumLitTy, mkStrLitTy, isStrLitTy, getRuntimeRep_maybe, getRuntimeRepFromKind_maybe, mkCastTy, mkCoercionTy, splitCastTy_maybe, userTypeError_maybe, pprUserTypeErrorTy, coAxNthLHS, stripCoercionTy, splitCoercionType_maybe, splitPiTysInvisible, filterOutInvisibleTypes, partitionInvisibles, synTyConResKind, modifyJoinResTy, setJoinResTy, -- Analyzing types TyCoMapper(..), mapType, mapCoercion, -- (Newtypes) newTyConInstRhs, -- Pred types mkFamilyTyConApp, isDictLikeTy, mkPrimEqPred, mkReprPrimEqPred, mkPrimEqPredRole, equalityTyCon, mkHeteroPrimEqPred, mkHeteroReprPrimEqPred, mkClassPred, isClassPred, isEqPred, isNomEqPred, isIPPred, isIPPred_maybe, isIPTyCon, isIPClass, isCTupleClass, -- Deconstructing predicate types PredTree(..), EqRel(..), eqRelRole, classifyPredType, getClassPredTys, getClassPredTys_maybe, getEqPredTys, getEqPredTys_maybe, getEqPredRole, predTypeEqRel, -- ** Binders sameVis, mkTyVarBinder, mkTyVarBinders, mkAnonBinder, isAnonTyBinder, isNamedTyBinder, binderVar, binderVars, binderKind, binderArgFlag, tyBinderType, tyBinderVar_maybe, binderRelevantType_maybe, caseBinder, isVisibleArgFlag, isInvisibleArgFlag, isVisibleBinder, isInvisibleBinder, tyConBindersTyBinders, -- ** Common type constructors funTyCon, -- ** Predicates on types isTyVarTy, isFunTy, isDictTy, isPredTy, isCoercionTy, isCoercionTy_maybe, isCoercionType, isForAllTy, isPiTy, isTauTy, isFamFreeTy, isValidJoinPointType, -- (Lifting and boxity) isLiftedType_maybe, isUnliftedType, isUnboxedTupleType, isUnboxedSumType, isAlgType, isDataFamilyAppType, isPrimitiveType, isStrictType, isRuntimeRepTy, isRuntimeRepVar, isRuntimeRepKindedTy, dropRuntimeRepArgs, getRuntimeRep, getRuntimeRepFromKind, -- * Main data types representing Kinds Kind, -- ** Finding the kind of a type typeKind, isTypeLevPoly, resultIsLevPoly, tcIsLiftedTypeKind, tcIsConstraintKind, tcReturnsConstraintKind, -- ** Common Kind liftedTypeKind, -- * Type free variables tyCoFVsOfType, tyCoFVsBndr, tyCoVarsOfType, tyCoVarsOfTypes, tyCoVarsOfTypeDSet, coVarsOfType, coVarsOfTypes, closeOverKinds, closeOverKindsList, noFreeVarsOfType, splitVisVarsOfType, splitVisVarsOfTypes, expandTypeSynonyms, typeSize, occCheckExpand, -- * Well-scoped lists of variables dVarSetElemsWellScoped, toposortTyVars, tyCoVarsOfTypeWellScoped, tyCoVarsOfTypesWellScoped, -- * Type comparison eqType, eqTypeX, eqTypes, nonDetCmpType, nonDetCmpTypes, nonDetCmpTypeX, nonDetCmpTypesX, nonDetCmpTc, eqVarBndrs, -- * Forcing evaluation of types seqType, seqTypes, -- * Other views onto Types coreView, tcView, tyConsOfType, -- * Main type substitution data types TvSubstEnv, -- Representation widely visible TCvSubst(..), -- Representation visible to a few friends -- ** Manipulating type substitutions emptyTvSubstEnv, emptyTCvSubst, mkEmptyTCvSubst, mkTCvSubst, zipTvSubst, mkTvSubstPrs, notElemTCvSubst, getTvSubstEnv, setTvSubstEnv, zapTCvSubst, getTCvInScope, getTCvSubstRangeFVs, extendTCvInScope, extendTCvInScopeList, extendTCvInScopeSet, extendTCvSubst, extendCvSubst, extendTvSubst, extendTvSubstBinderAndInScope, extendTvSubstList, extendTvSubstAndInScope, extendTvSubstWithClone, isInScope, composeTCvSubstEnv, composeTCvSubst, zipTyEnv, zipCoEnv, isEmptyTCvSubst, unionTCvSubst, -- ** Performing substitution on types and kinds substTy, substTys, substTyWith, substTysWith, substTheta, substTyAddInScope, substTyUnchecked, substTysUnchecked, substThetaUnchecked, substTyWithUnchecked, substCoUnchecked, substCoWithUnchecked, substTyVarBndr, substTyVarBndrs, substTyVar, substTyVars, cloneTyVarBndr, cloneTyVarBndrs, lookupTyVar, -- * Pretty-printing pprType, pprParendType, pprPrecType, pprTypeApp, pprTyThingCategory, pprShortTyThing, pprTvBndr, pprTvBndrs, pprForAll, pprUserForAll, pprSigmaType, ppSuggestExplicitKinds, pprTheta, pprThetaArrowTy, pprClassPred, pprKind, pprParendKind, pprSourceTyCon, PprPrec(..), topPrec, sigPrec, opPrec, funPrec, appPrec, maybeParen, pprTyVar, pprTyVars, pprWithTYPE, -- * Tidying type related things up for printing tidyType, tidyTypes, tidyOpenType, tidyOpenTypes, tidyOpenKind, tidyTyCoVarBndr, tidyTyCoVarBndrs, tidyFreeTyCoVars, tidyOpenTyCoVar, tidyOpenTyCoVars, tidyTyVarOcc, tidyTopType, tidyKind, tidyTyVarBinder, tidyTyVarBinders ) where #include "HsVersions.h" import GhcPrelude import BasicTypes -- We import the representation and primitive functions from TyCoRep. -- Many things are reexported, but not the representation! import Kind import TyCoRep -- friends: import Var import VarEnv import VarSet import UniqSet import Class import TyCon import TysPrim import {-# SOURCE #-} TysWiredIn ( listTyCon, typeNatKind , typeSymbolKind, liftedTypeKind ) import PrelNames import CoAxiom import {-# SOURCE #-} Coercion( mkCoherenceCo, mkReflCo , mkTyConAppCo, mkAppCo, mkCoVarCo, mkAxiomRuleCo , mkForAllCo, mkFunCo, mkAxiomInstCo, mkUnivCo , mkSymCo, mkTransCo, mkNthCo, mkLRCo, mkInstCo , mkKindCo, mkSubCo, mkFunCo, mkAxiomInstCo , decomposePiCos, coercionKind, coercionType , isReflexiveCo, seqCo ) -- others import Util import Outputable import FastString import Pair import DynFlags ( gopt_set, GeneralFlag(Opt_PrintExplicitRuntimeReps) ) import ListSetOps import Digraph import Unique ( nonDetCmpUnique ) import Maybes ( orElse ) import Data.Maybe ( isJust, mapMaybe ) import Control.Monad ( guard ) import Control.Arrow ( first, second ) -- $type_classification -- #type_classification# -- -- Types are one of: -- -- [Unboxed] Iff its representation is other than a pointer -- Unboxed types are also unlifted. -- -- [Lifted] Iff it has bottom as an element. -- Closures always have lifted types: i.e. any -- let-bound identifier in Core must have a lifted -- type. Operationally, a lifted object is one that -- can be entered. -- Only lifted types may be unified with a type variable. -- -- [Algebraic] Iff it is a type with one or more constructors, whether -- declared with @data@ or @newtype@. -- An algebraic type is one that can be deconstructed -- with a case expression. This is /not/ the same as -- lifted types, because we also include unboxed -- tuples in this classification. -- -- [Data] Iff it is a type declared with @data@, or a boxed tuple. -- -- [Primitive] Iff it is a built-in type that can't be expressed in Haskell. -- -- Currently, all primitive types are unlifted, but that's not necessarily -- the case: for example, @Int@ could be primitive. -- -- Some primitive types are unboxed, such as @Int#@, whereas some are boxed -- but unlifted (such as @ByteArray#@). The only primitive types that we -- classify as algebraic are the unboxed tuples. -- -- Some examples of type classifications that may make this a bit clearer are: -- -- @ -- Type primitive boxed lifted algebraic -- ----------------------------------------------------------------------------- -- Int# Yes No No No -- ByteArray# Yes Yes No No -- (\# a, b \#) Yes No No Yes -- (\# a | b \#) Yes No No Yes -- ( a, b ) No Yes Yes Yes -- [a] No Yes Yes Yes -- @ -- $representation_types -- A /source type/ is a type that is a separate type as far as the type checker is -- concerned, but which has a more low-level representation as far as Core-to-Core -- passes and the rest of the back end is concerned. -- -- You don't normally have to worry about this, as the utility functions in -- this module will automatically convert a source into a representation type -- if they are spotted, to the best of it's abilities. If you don't want this -- to happen, use the equivalent functions from the "TcType" module. {- ************************************************************************ * * Type representation * * ************************************************************************ Note [coreView vs tcView] ~~~~~~~~~~~~~~~~~~~~~~~~~ So far as the typechecker is concerned, 'Constraint' and 'TYPE LiftedRep' are distinct kinds. But in Core these two are treated as identical. We implement this by making 'coreView' convert 'Constraint' to 'TYPE LiftedRep' on the fly. The function tcView (used in the type checker) does not do this. See also Trac #11715, which tracks removing this inconsistency. -} -- | Gives the typechecker view of a type. This unwraps synonyms but -- leaves 'Constraint' alone. c.f. coreView, which turns Constraint into -- TYPE LiftedRep. Returns Nothing if no unwrapping happens. -- See also Note [coreView vs tcView] {-# INLINE tcView #-} tcView :: Type -> Maybe Type tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- expandSynTyCon_maybe tc tys = Just (mkAppTys (substTy (mkTvSubstPrs tenv) rhs) tys') -- The free vars of 'rhs' should all be bound by 'tenv', so it's -- ok to use 'substTy' here. -- See also Note [The substitution invariant] in TyCoRep. -- Its important to use mkAppTys, rather than (foldl AppTy), -- because the function part might well return a -- partially-applied type constructor; indeed, usually will! tcView _ = Nothing {-# INLINE coreView #-} coreView :: Type -> Maybe Type -- ^ This function Strips off the /top layer only/ of a type synonym -- application (if any) its underlying representation type. -- Returns Nothing if there is nothing to look through. -- This function considers 'Constraint' to be a synonym of @TYPE LiftedRep@. -- -- By being non-recursive and inlined, this case analysis gets efficiently -- joined onto the case analysis that the caller is already doing coreView ty@(TyConApp tc tys) | Just (tenv, rhs, tys') <- expandSynTyCon_maybe tc tys = Just (mkAppTys (substTy (mkTvSubstPrs tenv) rhs) tys') -- This equation is exactly like tcView -- At the Core level, Constraint = Type -- See Note [coreView vs tcView] | isConstraintKindCon tc = ASSERT2( null tys, ppr ty ) Just liftedTypeKind coreView _ = Nothing ----------------------------------------------- expandTypeSynonyms :: Type -> Type -- ^ Expand out all type synonyms. Actually, it'd suffice to expand out -- just the ones that discard type variables (e.g. type Funny a = Int) -- But we don't know which those are currently, so we just expand all. -- -- 'expandTypeSynonyms' only expands out type synonyms mentioned in the type, -- not in the kinds of any TyCon or TyVar mentioned in the type. -- -- Keep this synchronized with 'synonymTyConsOfType' expandTypeSynonyms ty = go (mkEmptyTCvSubst in_scope) ty where in_scope = mkInScopeSet (tyCoVarsOfType ty) go subst (TyConApp tc tys) | Just (tenv, rhs, tys') <- expandSynTyCon_maybe tc expanded_tys = let subst' = mkTvSubst in_scope (mkVarEnv tenv) -- Make a fresh substitution; rhs has nothing to -- do with anything that has happened so far -- NB: if you make changes here, be sure to build an -- /idempotent/ substitution, even in the nested case -- type T a b = a -> b -- type S x y = T y x -- (Trac #11665) in mkAppTys (go subst' rhs) tys' | otherwise = TyConApp tc expanded_tys where expanded_tys = (map (go subst) tys) go _ (LitTy l) = LitTy l go subst (TyVarTy tv) = substTyVar subst tv go subst (AppTy t1 t2) = mkAppTy (go subst t1) (go subst t2) go subst (FunTy arg res) = mkFunTy (go subst arg) (go subst res) go subst (ForAllTy (TvBndr tv vis) t) = let (subst', tv') = substTyVarBndrUsing go subst tv in ForAllTy (TvBndr tv' vis) (go subst' t) go subst (CastTy ty co) = mkCastTy (go subst ty) (go_co subst co) go subst (CoercionTy co) = mkCoercionTy (go_co subst co) go_co subst (Refl r ty) = mkReflCo r (go subst ty) -- NB: coercions are always expanded upon creation go_co subst (TyConAppCo r tc args) = mkTyConAppCo r tc (map (go_co subst) args) go_co subst (AppCo co arg) = mkAppCo (go_co subst co) (go_co subst arg) go_co subst (ForAllCo tv kind_co co) = let (subst', tv', kind_co') = go_cobndr subst tv kind_co in mkForAllCo tv' kind_co' (go_co subst' co) go_co subst (FunCo r co1 co2) = mkFunCo r (go_co subst co1) (go_co subst co2) go_co subst (CoVarCo cv) = substCoVar subst cv go_co subst (AxiomInstCo ax ind args) = mkAxiomInstCo ax ind (map (go_co subst) args) go_co subst (UnivCo p r t1 t2) = mkUnivCo (go_prov subst p) r (go subst t1) (go subst t2) go_co subst (SymCo co) = mkSymCo (go_co subst co) go_co subst (TransCo co1 co2) = mkTransCo (go_co subst co1) (go_co subst co2) go_co subst (NthCo r n co) = mkNthCo r n (go_co subst co) go_co subst (LRCo lr co) = mkLRCo lr (go_co subst co) go_co subst (InstCo co arg) = mkInstCo (go_co subst co) (go_co subst arg) go_co subst (CoherenceCo co1 co2) = mkCoherenceCo (go_co subst co1) (go_co subst co2) go_co subst (KindCo co) = mkKindCo (go_co subst co) go_co subst (SubCo co) = mkSubCo (go_co subst co) go_co subst (AxiomRuleCo ax cs) = AxiomRuleCo ax (map (go_co subst) cs) go_co _ (HoleCo h) = pprPanic "expandTypeSynonyms hit a hole" (ppr h) go_prov _ UnsafeCoerceProv = UnsafeCoerceProv go_prov subst (PhantomProv co) = PhantomProv (go_co subst co) go_prov subst (ProofIrrelProv co) = ProofIrrelProv (go_co subst co) go_prov _ p@(PluginProv _) = p -- the "False" and "const" are to accommodate the type of -- substForAllCoBndrUsing, which is general enough to -- handle coercion optimization (which sometimes swaps the -- order of a coercion) go_cobndr subst = substForAllCoBndrUsing False (go_co subst) subst {- ************************************************************************ * * Analyzing types * * ************************************************************************ These functions do a map-like operation over types, performing some operation on all variables and binding sites. Primarily used for zonking. Note [Efficiency for mapCoercion ForAllCo case] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ As noted in Note [Forall coercions] in TyCoRep, a ForAllCo is a bit redundant. It stores a TyVar and a Coercion, where the kind of the TyVar always matches the left-hand kind of the coercion. This is convenient lots of the time, but not when mapping a function over a coercion. The problem is that tcm_tybinder will affect the TyVar's kind and mapCoercion will affect the Coercion, and we hope that the results will be the same. Even if they are the same (which should generally happen with correct algorithms), then there is an efficiency issue. In particular, this problem seems to make what should be a linear algorithm into a potentially exponential one. But it's only going to be bad in the case where there's lots of foralls in the kinds of other foralls. Like this: forall a : (forall b : (forall c : ...). ...). ... This construction seems unlikely. So we'll do the inefficient, easy way for now. Note [Specialising mappers] ~~~~~~~~~~~~~~~~~~~~~~~~~~~ These INLINABLE pragmas are indispensable. mapType/mapCoercion are used to implement zonking, and it's vital that they get specialised to the TcM monad. This specialisation happens automatically (that is, without a SPECIALISE pragma) as long as the definitions are INLINABLE. For example, this one change made a 20% allocation difference in perf/compiler/T5030. -} -- | This describes how a "map" operation over a type/coercion should behave data TyCoMapper env m = TyCoMapper { tcm_smart :: Bool -- ^ Should the new type be created with smart -- constructors? , tcm_tyvar :: env -> TyVar -> m Type , tcm_covar :: env -> CoVar -> m Coercion , tcm_hole :: env -> CoercionHole -> m Coercion -- ^ What to do with coercion holes. -- See Note [Coercion holes] in TyCoRep. , tcm_tybinder :: env -> TyVar -> ArgFlag -> m (env, TyVar) -- ^ The returned env is used in the extended scope , tcm_tycon :: TyCon -> m TyCon -- ^ This is used only to turn 'TcTyCon's into 'TyCon's. -- See Note [Type checking recursive type and class declarations] -- in TcTyClsDecls } {-# INLINABLE mapType #-} -- See Note [Specialising mappers] mapType :: Monad m => TyCoMapper env m -> env -> Type -> m Type mapType mapper@(TyCoMapper { tcm_smart = smart, tcm_tyvar = tyvar , tcm_tybinder = tybinder, tcm_tycon = tycon }) env ty = go ty where go (TyVarTy tv) = tyvar env tv go (AppTy t1 t2) = mkappty <$> go t1 <*> go t2 go t@(TyConApp tc []) | not (isTcTyCon tc) = return t -- avoid allocation in this exceedingly -- common case (mostly, for *) go (TyConApp tc tys) = do { tc' <- tycon tc ; mktyconapp tc' <$> mapM go tys } go (FunTy arg res) = FunTy <$> go arg <*> go res go (ForAllTy (TvBndr tv vis) inner) = do { (env', tv') <- tybinder env tv vis ; inner' <- mapType mapper env' inner ; return $ ForAllTy (TvBndr tv' vis) inner' } go ty@(LitTy {}) = return ty go (CastTy ty co) = mkcastty <$> go ty <*> mapCoercion mapper env co go (CoercionTy co) = CoercionTy <$> mapCoercion mapper env co (mktyconapp, mkappty, mkcastty) | smart = (mkTyConApp, mkAppTy, mkCastTy) | otherwise = (TyConApp, AppTy, CastTy) {-# INLINABLE mapCoercion #-} -- See Note [Specialising mappers] mapCoercion :: Monad m => TyCoMapper env m -> env -> Coercion -> m Coercion mapCoercion mapper@(TyCoMapper { tcm_smart = smart, tcm_covar = covar , tcm_hole = cohole, tcm_tybinder = tybinder , tcm_tycon = tycon }) env co = go co where go (Refl r ty) = Refl r <$> mapType mapper env ty go (TyConAppCo r tc args) = do { tc' <- tycon tc ; mktyconappco r tc' <$> mapM go args } go (AppCo c1 c2) = mkappco <$> go c1 <*> go c2 go (ForAllCo tv kind_co co) = do { kind_co' <- go kind_co ; (env', tv') <- tybinder env tv Inferred ; co' <- mapCoercion mapper env' co ; return $ mkforallco tv' kind_co' co' } -- See Note [Efficiency for mapCoercion ForAllCo case] go (FunCo r c1 c2) = mkFunCo r <$> go c1 <*> go c2 go (CoVarCo cv) = covar env cv go (AxiomInstCo ax i args) = mkaxiominstco ax i <$> mapM go args go (HoleCo hole) = cohole env hole go (UnivCo p r t1 t2) = mkunivco <$> go_prov p <*> pure r <*> mapType mapper env t1 <*> mapType mapper env t2 go (SymCo co) = mksymco <$> go co go (TransCo c1 c2) = mktransco <$> go c1 <*> go c2 go (AxiomRuleCo r cos) = AxiomRuleCo r <$> mapM go cos go (NthCo r i co) = mknthco r i <$> go co go (LRCo lr co) = mklrco lr <$> go co go (InstCo co arg) = mkinstco <$> go co <*> go arg go (CoherenceCo c1 c2) = mkcoherenceco <$> go c1 <*> go c2 go (KindCo co) = mkkindco <$> go co go (SubCo co) = mksubco <$> go co go_prov UnsafeCoerceProv = return UnsafeCoerceProv go_prov (PhantomProv co) = PhantomProv <$> go co go_prov (ProofIrrelProv co) = ProofIrrelProv <$> go co go_prov p@(PluginProv _) = return p ( mktyconappco, mkappco, mkaxiominstco, mkunivco , mksymco, mktransco, mknthco, mklrco, mkinstco, mkcoherenceco , mkkindco, mksubco, mkforallco) | smart = ( mkTyConAppCo, mkAppCo, mkAxiomInstCo, mkUnivCo , mkSymCo, mkTransCo, mkNthCo, mkLRCo, mkInstCo, mkCoherenceCo , mkKindCo, mkSubCo, mkForAllCo ) | otherwise = ( TyConAppCo, AppCo, AxiomInstCo, UnivCo , SymCo, TransCo, NthCo, LRCo, InstCo, CoherenceCo , KindCo, SubCo, ForAllCo ) {- ************************************************************************ * * \subsection{Constructor-specific functions} * * ************************************************************************ --------------------------------------------------------------------- TyVarTy ~~~~~~~ -} -- | Attempts to obtain the type variable underlying a 'Type', and panics with the -- given message if this is not a type variable type. See also 'getTyVar_maybe' getTyVar :: String -> Type -> TyVar getTyVar msg ty = case getTyVar_maybe ty of Just tv -> tv Nothing -> panic ("getTyVar: " ++ msg) isTyVarTy :: Type -> Bool isTyVarTy ty = isJust (getTyVar_maybe ty) -- | Attempts to obtain the type variable underlying a 'Type' getTyVar_maybe :: Type -> Maybe TyVar getTyVar_maybe ty | Just ty' <- coreView ty = getTyVar_maybe ty' | otherwise = repGetTyVar_maybe ty -- | If the type is a tyvar, possibly under a cast, returns it, along -- with the coercion. Thus, the co is :: kind tv ~N kind type getCastedTyVar_maybe :: Type -> Maybe (TyVar, CoercionN) getCastedTyVar_maybe ty | Just ty' <- coreView ty = getCastedTyVar_maybe ty' getCastedTyVar_maybe (CastTy (TyVarTy tv) co) = Just (tv, co) getCastedTyVar_maybe (TyVarTy tv) = Just (tv, mkReflCo Nominal (tyVarKind tv)) getCastedTyVar_maybe _ = Nothing -- | Attempts to obtain the type variable underlying a 'Type', without -- any expansion repGetTyVar_maybe :: Type -> Maybe TyVar repGetTyVar_maybe (TyVarTy tv) = Just tv repGetTyVar_maybe _ = Nothing {- --------------------------------------------------------------------- AppTy ~~~~~ We need to be pretty careful with AppTy to make sure we obey the invariant that a TyConApp is always visibly so. mkAppTy maintains the invariant: use it. Note [Decomposing fat arrow c=>t] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Can we unify (a b) with (Eq a => ty)? If we do so, we end up with a partial application like ((=>) Eq a) which doesn't make sense in source Haskell. In contrast, we *can* unify (a b) with (t1 -> t2). Here's an example (Trac #9858) of how you might do it: i :: (Typeable a, Typeable b) => Proxy (a b) -> TypeRep i p = typeRep p j = i (Proxy :: Proxy (Eq Int => Int)) The type (Proxy (Eq Int => Int)) is only accepted with -XImpredicativeTypes, but suppose we want that. But then in the call to 'i', we end up decomposing (Eq Int => Int), and we definitely don't want that. This really only applies to the type checker; in Core, '=>' and '->' are the same, as are 'Constraint' and '*'. But for now I've put the test in repSplitAppTy_maybe, which applies throughout, because the other calls to splitAppTy are in Unify, which is also used by the type checker (e.g. when matching type-function equations). -} -- | Applies a type to another, as in e.g. @k a@ mkAppTy :: Type -> Type -> Type -- See Note [Respecting definitional equality], invariant (EQ1). mkAppTy (CastTy fun_ty co) arg_ty | ([arg_co], res_co) <- decomposePiCos co (coercionKind co) [arg_ty] = (fun_ty `mkAppTy` (arg_ty `mkCastTy` arg_co)) `mkCastTy` res_co mkAppTy (TyConApp tc tys) ty2 = mkTyConApp tc (tys ++ [ty2]) mkAppTy ty1 ty2 = AppTy ty1 ty2 -- Note that the TyConApp could be an -- under-saturated type synonym. GHC allows that; e.g. -- type Foo k = k a -> k a -- type Id x = x -- foo :: Foo Id -> Foo Id -- -- Here Id is partially applied in the type sig for Foo, -- but once the type synonyms are expanded all is well mkAppTys :: Type -> [Type] -> Type mkAppTys ty1 [] = ty1 mkAppTys (CastTy fun_ty co) arg_tys -- much more efficient then nested mkAppTy -- Why do this? See (EQ1) of -- Note [Respecting definitional equality] -- in TyCoRep = foldl AppTy ((mkAppTys fun_ty casted_arg_tys) `mkCastTy` res_co) leftovers where (arg_cos, res_co) = decomposePiCos co (coercionKind co) arg_tys (args_to_cast, leftovers) = splitAtList arg_cos arg_tys casted_arg_tys = zipWith mkCastTy args_to_cast arg_cos mkAppTys (TyConApp tc tys1) tys2 = mkTyConApp tc (tys1 ++ tys2) mkAppTys ty1 tys2 = foldl AppTy ty1 tys2 ------------- splitAppTy_maybe :: Type -> Maybe (Type, Type) -- ^ Attempt to take a type application apart, whether it is a -- function, type constructor, or plain type application. Note -- that type family applications are NEVER unsaturated by this! splitAppTy_maybe ty | Just ty' <- coreView ty = splitAppTy_maybe ty' splitAppTy_maybe ty = repSplitAppTy_maybe ty ------------- repSplitAppTy_maybe :: HasDebugCallStack => Type -> Maybe (Type,Type) -- ^ Does the AppTy split as in 'splitAppTy_maybe', but assumes that -- any Core view stuff is already done repSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [rep1, rep2, ty1], ty2) where rep1 = getRuntimeRep ty1 rep2 = getRuntimeRep ty2 repSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2) repSplitAppTy_maybe (TyConApp tc tys) | mightBeUnsaturatedTyCon tc || tys `lengthExceeds` tyConArity tc , Just (tys', ty') <- snocView tys = Just (TyConApp tc tys', ty') -- Never create unsaturated type family apps! repSplitAppTy_maybe _other = Nothing -- This one doesn't break apart (c => t). -- See Note [Decomposing fat arrow c=>t] -- Defined here to avoid module loops between Unify and TcType. tcRepSplitAppTy_maybe :: Type -> Maybe (Type,Type) -- ^ Does the AppTy split as in 'tcSplitAppTy_maybe', but assumes that -- any coreView stuff is already done. Refuses to look through (c => t) tcRepSplitAppTy_maybe (FunTy ty1 ty2) | isPredTy ty1 = Nothing -- See Note [Decomposing fat arrow c=>t] | otherwise = Just (TyConApp funTyCon [rep1, rep2, ty1], ty2) where rep1 = getRuntimeRep ty1 rep2 = getRuntimeRep ty2 tcRepSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2) tcRepSplitAppTy_maybe (TyConApp tc tys) | mightBeUnsaturatedTyCon tc || tys `lengthExceeds` tyConArity tc , Just (tys', ty') <- snocView tys = Just (TyConApp tc tys', ty') -- Never create unsaturated type family apps! tcRepSplitAppTy_maybe _other = Nothing -- | Like 'tcSplitTyConApp_maybe' but doesn't look through type synonyms. tcRepSplitTyConApp_maybe :: HasCallStack => Type -> Maybe (TyCon, [Type]) -- Defined here to avoid module loops between Unify and TcType. tcRepSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys) tcRepSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg_rep, res_rep, arg, res]) where arg_rep = getRuntimeRep arg res_rep = getRuntimeRep res tcRepSplitTyConApp_maybe _ = Nothing ------------- splitAppTy :: Type -> (Type, Type) -- ^ Attempts to take a type application apart, as in 'splitAppTy_maybe', -- and panics if this is not possible splitAppTy ty = case splitAppTy_maybe ty of Just pr -> pr Nothing -> panic "splitAppTy" ------------- splitAppTys :: Type -> (Type, [Type]) -- ^ Recursively splits a type as far as is possible, leaving a residual -- type being applied to and the type arguments applied to it. Never fails, -- even if that means returning an empty list of type applications. splitAppTys ty = split ty ty [] where split orig_ty ty args | Just ty' <- coreView ty = split orig_ty ty' args split _ (AppTy ty arg) args = split ty ty (arg:args) split _ (TyConApp tc tc_args) args = let -- keep type families saturated n | mightBeUnsaturatedTyCon tc = 0 | otherwise = tyConArity tc (tc_args1, tc_args2) = splitAt n tc_args in (TyConApp tc tc_args1, tc_args2 ++ args) split _ (FunTy ty1 ty2) args = ASSERT( null args ) (TyConApp funTyCon [], [rep1, rep2, ty1, ty2]) where rep1 = getRuntimeRep ty1 rep2 = getRuntimeRep ty2 split orig_ty _ args = (orig_ty, args) -- | Like 'splitAppTys', but doesn't look through type synonyms repSplitAppTys :: HasDebugCallStack => Type -> (Type, [Type]) repSplitAppTys ty = split ty [] where split (AppTy ty arg) args = split ty (arg:args) split (TyConApp tc tc_args) args = let n | mightBeUnsaturatedTyCon tc = 0 | otherwise = tyConArity tc (tc_args1, tc_args2) = splitAt n tc_args in (TyConApp tc tc_args1, tc_args2 ++ args) split (FunTy ty1 ty2) args = ASSERT( null args ) (TyConApp funTyCon [], [rep1, rep2, ty1, ty2]) where rep1 = getRuntimeRep ty1 rep2 = getRuntimeRep ty2 split ty args = (ty, args) {- LitTy ~~~~~ -} mkNumLitTy :: Integer -> Type mkNumLitTy n = LitTy (NumTyLit n) -- | Is this a numeric literal. We also look through type synonyms. isNumLitTy :: Type -> Maybe Integer isNumLitTy ty | Just ty1 <- coreView ty = isNumLitTy ty1 isNumLitTy (LitTy (NumTyLit n)) = Just n isNumLitTy _ = Nothing mkStrLitTy :: FastString -> Type mkStrLitTy s = LitTy (StrTyLit s) -- | Is this a symbol literal. We also look through type synonyms. isStrLitTy :: Type -> Maybe FastString isStrLitTy ty | Just ty1 <- coreView ty = isStrLitTy ty1 isStrLitTy (LitTy (StrTyLit s)) = Just s isStrLitTy _ = Nothing -- | Is this type a custom user error? -- If so, give us the kind and the error message. userTypeError_maybe :: Type -> Maybe Type userTypeError_maybe t = do { (tc, _kind : msg : _) <- splitTyConApp_maybe t -- There may be more than 2 arguments, if the type error is -- used as a type constructor (e.g. at kind `Type -> Type`). ; guard (tyConName tc == errorMessageTypeErrorFamName) ; return msg } -- | Render a type corresponding to a user type error into a SDoc. pprUserTypeErrorTy :: Type -> SDoc pprUserTypeErrorTy ty = case splitTyConApp_maybe ty of -- Text "Something" Just (tc,[txt]) | tyConName tc == typeErrorTextDataConName , Just str <- isStrLitTy txt -> ftext str -- ShowType t Just (tc,[_k,t]) | tyConName tc == typeErrorShowTypeDataConName -> ppr t -- t1 :<>: t2 Just (tc,[t1,t2]) | tyConName tc == typeErrorAppendDataConName -> pprUserTypeErrorTy t1 <> pprUserTypeErrorTy t2 -- t1 :$$: t2 Just (tc,[t1,t2]) | tyConName tc == typeErrorVAppendDataConName -> pprUserTypeErrorTy t1 $$ pprUserTypeErrorTy t2 -- An unevaluated type function _ -> ppr ty {- --------------------------------------------------------------------- FunTy ~~~~~ Note [Representation of function types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Functions (e.g. Int -> Char) are can be thought of as being applications of funTyCon (known in Haskell surface syntax as (->)), (->) :: forall (r1 :: RuntimeRep) (r2 :: RuntimeRep) (a :: TYPE r1) (b :: TYPE r2). a -> b -> Type However, for efficiency's sake we represent saturated applications of (->) with FunTy. For instance, the type, (->) r1 r2 a b is equivalent to, FunTy (Anon a) b Note how the RuntimeReps are implied in the FunTy representation. For this reason we must be careful when recontructing the TyConApp representation (see, for instance, splitTyConApp_maybe). In the compiler we maintain the invariant that all saturated applications of (->) are represented with FunTy. See #11714. -} isFunTy :: Type -> Bool isFunTy ty = isJust (splitFunTy_maybe ty) splitFunTy :: Type -> (Type, Type) -- ^ Attempts to extract the argument and result types from a type, and -- panics if that is not possible. See also 'splitFunTy_maybe' splitFunTy ty | Just ty' <- coreView ty = splitFunTy ty' splitFunTy (FunTy arg res) = (arg, res) splitFunTy other = pprPanic "splitFunTy" (ppr other) splitFunTy_maybe :: Type -> Maybe (Type, Type) -- ^ Attempts to extract the argument and result types from a type splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty' splitFunTy_maybe (FunTy arg res) = Just (arg, res) splitFunTy_maybe _ = Nothing splitFunTys :: Type -> ([Type], Type) splitFunTys ty = split [] ty ty where split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty' split args _ (FunTy arg res) = split (arg:args) res res split args orig_ty _ = (reverse args, orig_ty) funResultTy :: Type -> Type -- ^ Extract the function result type and panic if that is not possible funResultTy ty | Just ty' <- coreView ty = funResultTy ty' funResultTy (FunTy _ res) = res funResultTy ty = pprPanic "funResultTy" (ppr ty) funArgTy :: Type -> Type -- ^ Extract the function argument type and panic if that is not possible funArgTy ty | Just ty' <- coreView ty = funArgTy ty' funArgTy (FunTy arg _res) = arg funArgTy ty = pprPanic "funArgTy" (ppr ty) piResultTy :: HasDebugCallStack => Type -> Type -> Type piResultTy ty arg = case piResultTy_maybe ty arg of Just res -> res Nothing -> pprPanic "piResultTy" (ppr ty $$ ppr arg) piResultTy_maybe :: Type -> Type -> Maybe Type -- ^ Just like 'piResultTys' but for a single argument -- Try not to iterate 'piResultTy', because it's inefficient to substitute -- one variable at a time; instead use 'piResultTys" piResultTy_maybe ty arg | Just ty' <- coreView ty = piResultTy_maybe ty' arg | FunTy _ res <- ty = Just res | ForAllTy (TvBndr tv _) res <- ty = let empty_subst = mkEmptyTCvSubst $ mkInScopeSet $ tyCoVarsOfTypes [arg,res] in Just (substTy (extendTvSubst empty_subst tv arg) res) | otherwise = Nothing -- | (piResultTys f_ty [ty1, .., tyn]) gives the type of (f ty1 .. tyn) -- where f :: f_ty -- 'piResultTys' is interesting because: -- 1. 'f_ty' may have more for-alls than there are args -- 2. Less obviously, it may have fewer for-alls -- For case 2. think of: -- piResultTys (forall a.a) [forall b.b, Int] -- This really can happen, but only (I think) in situations involving -- undefined. For example: -- undefined :: forall a. a -- Term: undefined @(forall b. b->b) @Int -- This term should have type (Int -> Int), but notice that -- there are more type args than foralls in 'undefined's type. -- If you edit this function, you may need to update the GHC formalism -- See Note [GHC Formalism] in coreSyn/CoreLint.hs -- This is a heavily used function (e.g. from typeKind), -- so we pay attention to efficiency, especially in the special case -- where there are no for-alls so we are just dropping arrows from -- a function type/kind. piResultTys :: HasDebugCallStack => Type -> [Type] -> Type piResultTys ty [] = ty piResultTys ty orig_args@(arg:args) | Just ty' <- coreView ty = piResultTys ty' orig_args | FunTy _ res <- ty = piResultTys res args | ForAllTy (TvBndr tv _) res <- ty = go (extendVarEnv emptyTvSubstEnv tv arg) res args | otherwise = pprPanic "piResultTys1" (ppr ty $$ ppr orig_args) where in_scope = mkInScopeSet (tyCoVarsOfTypes (ty:orig_args)) go :: TvSubstEnv -> Type -> [Type] -> Type go tv_env ty [] = substTy (mkTvSubst in_scope tv_env) ty go tv_env ty all_args@(arg:args) | Just ty' <- coreView ty = go tv_env ty' all_args | FunTy _ res <- ty = go tv_env res args | ForAllTy (TvBndr tv _) res <- ty = go (extendVarEnv tv_env tv arg) res args | not (isEmptyVarEnv tv_env) -- See Note [Care with kind instantiation] = go emptyTvSubstEnv (substTy (mkTvSubst in_scope tv_env) ty) all_args | otherwise = -- We have not run out of arguments, but the function doesn't -- have the right kind to apply to them; so panic. -- Without hte explicit isEmptyVarEnv test, an ill-kinded type -- would give an infniite loop, which is very unhelpful -- c.f. Trac #15473 pprPanic "piResultTys2" (ppr ty $$ ppr orig_args $$ ppr all_args) applyTysX :: [TyVar] -> Type -> [Type] -> Type -- applyTyxX beta-reduces (/\tvs. body_ty) arg_tys -- Assumes that (/\tvs. body_ty) is closed applyTysX tvs body_ty arg_tys = ASSERT2( arg_tys `lengthAtLeast` n_tvs, pp_stuff ) ASSERT2( tyCoVarsOfType body_ty `subVarSet` mkVarSet tvs, pp_stuff ) mkAppTys (substTyWith tvs (take n_tvs arg_tys) body_ty) (drop n_tvs arg_tys) where pp_stuff = vcat [ppr tvs, ppr body_ty, ppr arg_tys] n_tvs = length tvs {- Note [Care with kind instantiation] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Suppose we have T :: forall k. k and we are finding the kind of T (forall b. b -> b) * Int Then T (forall b. b->b) :: k[ k :-> forall b. b->b] :: forall b. b -> b So T (forall b. b->b) * :: (b -> b)[ b :-> *] :: * -> * In other words wwe must intantiate the forall! Similarly (Trac #154218) S :: forall k f. k -> f k and we are finding the kind of S * (* ->) Int Bool We have S * (* ->) :: (k -> f k)[ k :-> *, f :-> (* ->)] :: * -> * -> * So again we must instantiate. The same thing happens in ToIface.toIfaceAppArgsX. --------------------------------------------------------------------- TyConApp ~~~~~~~~ -} -- | A key function: builds a 'TyConApp' or 'FunTy' as appropriate to -- its arguments. Applies its arguments to the constructor from left to right. mkTyConApp :: TyCon -> [Type] -> Type mkTyConApp tycon tys | isFunTyCon tycon , [_rep1,_rep2,ty1,ty2] <- tys = FunTy ty1 ty2 | otherwise = TyConApp tycon tys -- splitTyConApp "looks through" synonyms, because they don't -- mean a distinct type, but all other type-constructor applications -- including functions are returned as Just .. -- | Retrieve the tycon heading this type, if there is one. Does /not/ -- look through synonyms. tyConAppTyConPicky_maybe :: Type -> Maybe TyCon tyConAppTyConPicky_maybe (TyConApp tc _) = Just tc tyConAppTyConPicky_maybe (FunTy {}) = Just funTyCon tyConAppTyConPicky_maybe _ = Nothing -- | The same as @fst . splitTyConApp@ tyConAppTyCon_maybe :: Type -> Maybe TyCon tyConAppTyCon_maybe ty | Just ty' <- coreView ty = tyConAppTyCon_maybe ty' tyConAppTyCon_maybe (TyConApp tc _) = Just tc tyConAppTyCon_maybe (FunTy {}) = Just funTyCon tyConAppTyCon_maybe _ = Nothing tyConAppTyCon :: Type -> TyCon tyConAppTyCon ty = tyConAppTyCon_maybe ty `orElse` pprPanic "tyConAppTyCon" (ppr ty) -- | The same as @snd . splitTyConApp@ tyConAppArgs_maybe :: Type -> Maybe [Type] tyConAppArgs_maybe ty | Just ty' <- coreView ty = tyConAppArgs_maybe ty' tyConAppArgs_maybe (TyConApp _ tys) = Just tys tyConAppArgs_maybe (FunTy arg res) | Just rep1 <- getRuntimeRep_maybe arg , Just rep2 <- getRuntimeRep_maybe res = Just [rep1, rep2, arg, res] tyConAppArgs_maybe _ = Nothing tyConAppArgs :: Type -> [Type] tyConAppArgs ty = tyConAppArgs_maybe ty `orElse` pprPanic "tyConAppArgs" (ppr ty) tyConAppArgN :: Int -> Type -> Type -- Executing Nth tyConAppArgN n ty = case tyConAppArgs_maybe ty of Just tys -> ASSERT2( tys `lengthExceeds` n, ppr n <+> ppr tys ) tys `getNth` n Nothing -> pprPanic "tyConAppArgN" (ppr n <+> ppr ty) -- | Attempts to tease a type apart into a type constructor and the application -- of a number of arguments to that constructor. Panics if that is not possible. -- See also 'splitTyConApp_maybe' splitTyConApp :: Type -> (TyCon, [Type]) splitTyConApp ty = case splitTyConApp_maybe ty of Just stuff -> stuff Nothing -> pprPanic "splitTyConApp" (ppr ty) -- | Attempts to tease a type apart into a type constructor and the application -- of a number of arguments to that constructor splitTyConApp_maybe :: HasDebugCallStack => Type -> Maybe (TyCon, [Type]) splitTyConApp_maybe ty | Just ty' <- coreView ty = splitTyConApp_maybe ty' splitTyConApp_maybe ty = repSplitTyConApp_maybe ty -- | Like 'splitTyConApp_maybe', but doesn't look through synonyms. This -- assumes the synonyms have already been dealt with. repSplitTyConApp_maybe :: HasDebugCallStack => Type -> Maybe (TyCon, [Type]) repSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys) repSplitTyConApp_maybe (FunTy arg res) | Just arg_rep <- getRuntimeRep_maybe arg , Just res_rep <- getRuntimeRep_maybe res = Just (funTyCon, [arg_rep, res_rep, arg, res]) repSplitTyConApp_maybe _ = Nothing -- | Attempts to tease a list type apart and gives the type of the elements if -- successful (looks through type synonyms) splitListTyConApp_maybe :: Type -> Maybe Type splitListTyConApp_maybe ty = case splitTyConApp_maybe ty of Just (tc,[e]) | tc == listTyCon -> Just e _other -> Nothing nextRole :: Type -> Role nextRole ty | Just (tc, tys) <- splitTyConApp_maybe ty , let num_tys = length tys , num_tys < tyConArity tc = tyConRoles tc `getNth` num_tys | otherwise = Nominal newTyConInstRhs :: TyCon -> [Type] -> Type -- ^ Unwrap one 'layer' of newtype on a type constructor and its -- arguments, using an eta-reduced version of the @newtype@ if possible. -- This requires tys to have at least @newTyConInstArity tycon@ elements. newTyConInstRhs tycon tys = ASSERT2( tvs `leLength` tys, ppr tycon $$ ppr tys $$ ppr tvs ) applyTysX tvs rhs tys where (tvs, rhs) = newTyConEtadRhs tycon {- --------------------------------------------------------------------- CastTy ~~~~~~ A casted type has its *kind* casted into something new. -} splitCastTy_maybe :: Type -> Maybe (Type, Coercion) splitCastTy_maybe ty | Just ty' <- coreView ty = splitCastTy_maybe ty' splitCastTy_maybe (CastTy ty co) = Just (ty, co) splitCastTy_maybe _ = Nothing -- | Make a 'CastTy'. The Coercion must be nominal. Checks the -- Coercion for reflexivity, dropping it if it's reflexive. -- See Note [Respecting definitional equality] in TyCoRep mkCastTy :: Type -> Coercion -> Type mkCastTy ty co | isReflexiveCo co = ty -- (EQ2) from the Note -- NB: Do the slow check here. This is important to keep the splitXXX -- functions working properly. Otherwise, we may end up with something -- like (((->) |> something_reflexive_but_not_obviously_so) biz baz) -- fails under splitFunTy_maybe. This happened with the cheaper check -- in test dependent/should_compile/dynamic-paper. mkCastTy (CastTy ty co1) co2 = mkCastTy ty (co1 `mkTransCo` co2) -- (EQ3) from the Note -- call mkCastTy again for the reflexivity check mkCastTy ty co = CastTy ty co tyConBindersTyBinders :: [TyConBinder] -> [TyBinder] -- Return the tyConBinders in TyBinder form tyConBindersTyBinders = map to_tyb where to_tyb (TvBndr tv (NamedTCB vis)) = Named (TvBndr tv vis) to_tyb (TvBndr tv AnonTCB) = Anon (tyVarKind tv) {- -------------------------------------------------------------------- CoercionTy ~~~~~~~~~~ CoercionTy allows us to inject coercions into types. A CoercionTy should appear only in the right-hand side of an application. -} mkCoercionTy :: Coercion -> Type mkCoercionTy = CoercionTy isCoercionTy :: Type -> Bool isCoercionTy (CoercionTy _) = True isCoercionTy _ = False isCoercionTy_maybe :: Type -> Maybe Coercion isCoercionTy_maybe (CoercionTy co) = Just co isCoercionTy_maybe _ = Nothing stripCoercionTy :: Type -> Coercion stripCoercionTy (CoercionTy co) = co stripCoercionTy ty = pprPanic "stripCoercionTy" (ppr ty) {- --------------------------------------------------------------------- SynTy ~~~~~ Notes on type synonyms ~~~~~~~~~~~~~~~~~~~~~~ The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try to return type synonyms wherever possible. Thus type Foo a = a -> a we want splitFunTys (a -> Foo a) = ([a], Foo a) not ([a], a -> a) The reason is that we then get better (shorter) type signatures in interfaces. Notably this plays a role in tcTySigs in TcBinds.hs. --------------------------------------------------------------------- ForAllTy ~~~~~~~~ -} -- | Make a dependent forall over an Inferred (as opposed to Specified) -- variable mkInvForAllTy :: TyVar -> Type -> Type mkInvForAllTy tv ty = ASSERT( isTyVar tv ) ForAllTy (TvBndr tv Inferred) ty -- | Like mkForAllTys, but assumes all variables are dependent and Inferred, -- a common case mkInvForAllTys :: [TyVar] -> Type -> Type mkInvForAllTys tvs ty = ASSERT( all isTyVar tvs ) foldr mkInvForAllTy ty tvs -- | Like mkForAllTys, but assumes all variables are dependent and specified, -- a common case mkSpecForAllTys :: [TyVar] -> Type -> Type mkSpecForAllTys tvs = ASSERT( all isTyVar tvs ) mkForAllTys [ TvBndr tv Specified | tv <- tvs ] -- | Like mkForAllTys, but assumes all variables are dependent and visible mkVisForAllTys :: [TyVar] -> Type -> Type mkVisForAllTys tvs = ASSERT( all isTyVar tvs ) mkForAllTys [ TvBndr tv Required | tv <- tvs ] mkLamType :: Var -> Type -> Type -- ^ Makes a @(->)@ type or an implicit forall type, depending -- on whether it is given a type variable or a term variable. -- This is used, for example, when producing the type of a lambda. -- Always uses Inferred binders. mkLamTypes :: [Var] -> Type -> Type -- ^ 'mkLamType' for multiple type or value arguments mkLamType v ty | isTyVar v = ForAllTy (TvBndr v Inferred) ty | otherwise = FunTy (varType v) ty mkLamTypes vs ty = foldr mkLamType ty vs -- | Given a list of type-level vars and a result kind, -- makes TyBinders, preferring anonymous binders -- if the variable is, in fact, not dependent. -- e.g. mkTyConBindersPreferAnon [(k:*),(b:k),(c:k)] (k->k) -- We want (k:*) Named, (a;k) Anon, (c:k) Anon -- -- All binders are /visible/. mkTyConBindersPreferAnon :: [TyVar] -> Type -> [TyConBinder] mkTyConBindersPreferAnon vars inner_ty = fst (go vars) where go :: [TyVar] -> ([TyConBinder], VarSet) -- also returns the free vars go [] = ([], tyCoVarsOfType inner_ty) go (v:vs) | v `elemVarSet` fvs = ( TvBndr v (NamedTCB Required) : binders , fvs `delVarSet` v `unionVarSet` kind_vars ) | otherwise = ( TvBndr v AnonTCB : binders , fvs `unionVarSet` kind_vars ) where (binders, fvs) = go vs kind_vars = tyCoVarsOfType $ tyVarKind v -- | Take a ForAllTy apart, returning the list of tyvars and the result type. -- This always succeeds, even if it returns only an empty list. Note that the -- result type returned may have free variables that were bound by a forall. splitForAllTys :: Type -> ([TyVar], Type) splitForAllTys ty = split ty ty [] where split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs split _ (ForAllTy (TvBndr tv _) ty) tvs = split ty ty (tv:tvs) split orig_ty _ tvs = (reverse tvs, orig_ty) -- | Like 'splitPiTys' but split off only /named/ binders. splitForAllTyVarBndrs :: Type -> ([TyVarBinder], Type) splitForAllTyVarBndrs ty = split ty ty [] where split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs split _ (ForAllTy b res) bs = split res res (b:bs) split orig_ty _ bs = (reverse bs, orig_ty) {-# INLINE splitForAllTyVarBndrs #-} -- | Checks whether this is a proper forall (with a named binder) isForAllTy :: Type -> Bool isForAllTy ty | Just ty' <- coreView ty = isForAllTy ty' isForAllTy (ForAllTy {}) = True isForAllTy _ = False -- | Is this a function or forall? isPiTy :: Type -> Bool isPiTy ty | Just ty' <- coreView ty = isForAllTy ty' isPiTy (ForAllTy {}) = True isPiTy (FunTy {}) = True isPiTy _ = False -- | Take a forall type apart, or panics if that is not possible. splitForAllTy :: Type -> (TyVar, Type) splitForAllTy ty | Just answer <- splitForAllTy_maybe ty = answer | otherwise = pprPanic "splitForAllTy" (ppr ty) -- | Drops all ForAllTys dropForAlls :: Type -> Type dropForAlls ty = go ty where go ty | Just ty' <- coreView ty = go ty' go (ForAllTy _ res) = go res go res = res -- | Attempts to take a forall type apart, but only if it's a proper forall, -- with a named binder splitForAllTy_maybe :: Type -> Maybe (TyVar, Type) splitForAllTy_maybe ty = go ty where go ty | Just ty' <- coreView ty = go ty' go (ForAllTy (TvBndr tv _) ty) = Just (tv, ty) go _ = Nothing -- | Attempts to take a forall type apart; works with proper foralls and -- functions splitPiTy_maybe :: Type -> Maybe (TyBinder, Type) splitPiTy_maybe ty = go ty where go ty | Just ty' <- coreView ty = go ty' go (ForAllTy bndr ty) = Just (Named bndr, ty) go (FunTy arg res) = Just (Anon arg, res) go _ = Nothing -- | Takes a forall type apart, or panics splitPiTy :: Type -> (TyBinder, Type) splitPiTy ty | Just answer <- splitPiTy_maybe ty = answer | otherwise = pprPanic "splitPiTy" (ppr ty) -- | Split off all TyBinders to a type, splitting both proper foralls -- and functions splitPiTys :: Type -> ([TyBinder], Type) splitPiTys ty = split ty ty where split orig_ty ty | Just ty' <- coreView ty = split orig_ty ty' split _ (ForAllTy b res) = let (bs, ty) = split res res in (Named b : bs, ty) split _ (FunTy arg res) = let (bs, ty) = split res res in (Anon arg : bs, ty) split orig_ty _ = ([], orig_ty) -- Like splitPiTys, but returns only *invisible* binders, including constraints -- Stops at the first visible binder splitPiTysInvisible :: Type -> ([TyBinder], Type) splitPiTysInvisible ty = split ty ty [] where split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs split _ (ForAllTy b@(TvBndr _ vis) res) bs | isInvisibleArgFlag vis = split res res (Named b : bs) split _ (FunTy arg res) bs | isPredTy arg = split res res (Anon arg : bs) split orig_ty _ bs = (reverse bs, orig_ty) -- | Given a tycon and its arguments, filters out any invisible arguments filterOutInvisibleTypes :: TyCon -> [Type] -> [Type] filterOutInvisibleTypes tc tys = snd $ partitionInvisibles tc id tys -- | Given a tycon and a list of things (which correspond to arguments), -- partitions the things into -- Inferred or Specified ones and -- Required ones -- The callback function is necessary for this scenario: -- -- > T :: forall k. k -> k -- > partitionInvisibles T [forall m. m -> m -> m, S, R, Q] -- -- After substituting, we get -- -- > T (forall m. m -> m -> m) :: (forall m. m -> m -> m) -> forall n. n -> n -> n -- -- Thus, the first argument is invisible, @S@ is visible, @R@ is invisible again, -- and @Q@ is visible. -- -- If you're absolutely sure that your tycon's kind doesn't end in a variable, -- it's OK if the callback function panics, as that's the only time it's -- consulted. partitionInvisibles :: TyCon -> (a -> Type) -> [a] -> ([a], [a]) partitionInvisibles tc get_ty = go emptyTCvSubst (tyConKind tc) where go _ _ [] = ([], []) go subst (ForAllTy (TvBndr tv vis) res_ki) (x:xs) | isVisibleArgFlag vis = second (x :) (go subst' res_ki xs) | otherwise = first (x :) (go subst' res_ki xs) where subst' = extendTvSubst subst tv (get_ty x) go subst (TyVarTy tv) xs | Just ki <- lookupTyVar subst tv = go subst ki xs go _ _ xs = ([], xs) -- something is ill-kinded. But this can happen -- when printing errors. Assume everything is visible. -- @isTauTy@ tests if a type has no foralls isTauTy :: Type -> Bool isTauTy ty | Just ty' <- coreView 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 isTauTy (CastTy ty _) = isTauTy ty isTauTy (CoercionTy _) = False -- Not sure about this {- %************************************************************************ %* * TyBinders %* * %************************************************************************ -} -- | Make an anonymous binder mkAnonBinder :: Type -> TyBinder mkAnonBinder = Anon -- | Does this binder bind a variable that is /not/ erased? Returns -- 'True' for anonymous binders. isAnonTyBinder :: TyBinder -> Bool isAnonTyBinder (Named {}) = False isAnonTyBinder (Anon {}) = True isNamedTyBinder :: TyBinder -> Bool isNamedTyBinder (Named {}) = True isNamedTyBinder (Anon {}) = False tyBinderVar_maybe :: TyBinder -> Maybe TyVar tyBinderVar_maybe (Named tv) = Just $ binderVar tv tyBinderVar_maybe _ = Nothing tyBinderType :: TyBinder -> Type -- Barely used tyBinderType (Named tvb) = binderKind tvb tyBinderType (Anon ty) = ty -- | Extract a relevant type, if there is one. binderRelevantType_maybe :: TyBinder -> Maybe Type binderRelevantType_maybe (Named {}) = Nothing binderRelevantType_maybe (Anon ty) = Just ty -- | Like 'maybe', but for binders. caseBinder :: TyBinder -- ^ binder to scrutinize -> (TyVarBinder -> a) -- ^ named case -> (Type -> a) -- ^ anonymous case -> a caseBinder (Named v) f _ = f v caseBinder (Anon t) _ d = d t {- %************************************************************************ %* * Pred * * ************************************************************************ Predicates on PredType Note [isPredTy complications] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You would think that we could define isPredTy ty = isConstraintKind (typeKind ty) But there are a number of complications: * isPredTy is used when printing types, which can happen in debug printing during type checking of not-fully-zonked types. So it's not cool to say isConstraintKind (typeKind ty) because, absent zonking, the type might be ill-kinded, and typeKind crashes. Hence the rather tiresome story here * isPredTy must return "True" to *unlifted* coercions, such as (t1 ~# t2) and (t1 ~R# t2), which are not of kind Constraint! Currently they are of kind #. * If we do form the type '(C a => C [a]) => blah', then we'd like to print it as such. But that means that isPredTy must return True for (C a => C [a]). Admittedly that type is illegal in Haskell, but we want to print it nicely in error messages. -} -- | Split a type constructor application into its type constructor and -- applied types. Note that this may fail in the case of a 'FunTy' with an -- argument of unknown kind 'FunTy' (e.g. @FunTy (a :: k) Int@. since the kind -- of @a@ isn't of the form @TYPE rep@). Consequently, you may need to zonk your -- type before using this function. -- -- If you only need the 'TyCon', consider using 'tcTyConAppTyCon_maybe'. tcSplitTyConApp_maybe :: HasCallStack => Type -> Maybe (TyCon, [Type]) -- Defined here to avoid module loops between Unify and TcType. tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty' tcSplitTyConApp_maybe ty = tcRepSplitTyConApp_maybe ty -- tcIsConstraintKind stuf only makes sense in the typechecker -- After that Constraint = Type -- See Note [coreView vs tcView] -- Defined here because it is used in isPredTy and tcRepSplitAppTy_maybe (sigh) tcIsConstraintKind :: Kind -> Bool tcIsConstraintKind ty | Just (tc, args) <- tcSplitTyConApp_maybe ty -- Note: tcSplit here , isConstraintKindCon tc = ASSERT2( null args, ppr ty ) True | otherwise = False -- | Is this kind equivalent to @*@? -- -- This considers 'Constraint' to be distinct from @*@. For a version that -- treats them as the same type, see 'isLiftedTypeKind'. tcIsLiftedTypeKind :: Kind -> Bool tcIsLiftedTypeKind ty | Just (type_tc, [arg]) <- tcSplitTyConApp_maybe ty , type_tc `hasKey` tYPETyConKey , Just (lifted_rep_tc, args) <- tcSplitTyConApp_maybe arg , lifted_rep_tc `hasKey` liftedRepDataConKey = ASSERT2( null args, ppr ty ) True | otherwise = False tcReturnsConstraintKind :: Kind -> Bool -- True <=> the Kind ultimately returns a Constraint -- E.g. * -> Constraint -- forall k. k -> Constraint tcReturnsConstraintKind kind | Just kind' <- tcView kind = tcReturnsConstraintKind kind' tcReturnsConstraintKind (ForAllTy _ ty) = tcReturnsConstraintKind ty tcReturnsConstraintKind (FunTy _ ty) = tcReturnsConstraintKind ty tcReturnsConstraintKind (TyConApp tc _) = isConstraintKindCon tc tcReturnsConstraintKind _ = False -- | Is the type suitable to classify a given/wanted in the typechecker? isPredTy :: Type -> Bool -- See Note [isPredTy complications] isPredTy ty = go ty [] where go :: Type -> [KindOrType] -> Bool go (AppTy ty1 ty2) args = go ty1 (ty2 : args) go (TyVarTy tv) args = go_k (tyVarKind tv) args go (TyConApp tc tys) args = ASSERT( null args ) -- TyConApp invariant go_tc tc tys go (FunTy arg res) [] | isPredTy arg = isPredTy res -- (Eq a => C a) | otherwise = False -- (Int -> Bool) go (ForAllTy _ ty) [] = go ty [] go (CastTy _ co) args = go_k (pSnd (coercionKind co)) args go _ _ = False go_tc :: TyCon -> [KindOrType] -> Bool go_tc tc args | tc `hasKey` eqPrimTyConKey || tc `hasKey` eqReprPrimTyConKey = args `lengthIs` 4 -- ~# and ~R# sadly have result kind # -- not Constraint; but we still want -- isPredTy to reply True. | otherwise = go_k (tyConKind tc) args go_k :: Kind -> [KindOrType] -> Bool -- True <=> ('k' applied to 'kts') = Constraint go_k k [] = tcIsConstraintKind k go_k k (arg:args) = case piResultTy_maybe k arg of Just k' -> go_k k' args Nothing -> WARN( True, text "isPredTy" <+> ppr ty ) False -- This last case shouldn't happen under most circumstances. It can -- occur if we call isPredTy during kind checking, especially if one -- of the following happens: -- -- 1. There is actually a kind error. Example in which this showed up: -- polykinds/T11399 -- -- 2. A type constructor application appears to be oversaturated. An -- example of this occurred in GHC Trac #13187: -- -- {-# LANGUAGE PolyKinds #-} -- type Const a b = b -- f :: Const Int (,) Bool Char -> Char -- -- We call isPredTy (Const k1 k2 Int (,) Bool Char -- where k1,k2 are unification variables that have been -- unified to *, and (*->*->*) resp, /but not zonked/. -- This shows that isPredTy can report a false negative -- if a constraint is similarly oversaturated, but -- it's hard to do better than isPredTy currently does without -- zonking, so we punt on such cases for now. This only happens -- during debug-printing, so it doesn't matter. isClassPred, isEqPred, isNomEqPred, isIPPred :: PredType -> Bool isClassPred ty = case tyConAppTyCon_maybe ty of Just tyCon | isClassTyCon tyCon -> True _ -> False isEqPred ty = case tyConAppTyCon_maybe ty of Just tyCon -> tyCon `hasKey` eqPrimTyConKey || tyCon `hasKey` eqReprPrimTyConKey _ -> False isNomEqPred ty = case tyConAppTyCon_maybe ty of Just tyCon -> tyCon `hasKey` eqPrimTyConKey _ -> False isIPPred ty = case tyConAppTyCon_maybe ty of Just tc -> isIPTyCon tc _ -> False isIPTyCon :: TyCon -> Bool isIPTyCon tc = tc `hasKey` ipClassKey -- Class and its corresponding TyCon have the same Unique isIPClass :: Class -> Bool isIPClass cls = cls `hasKey` ipClassKey isCTupleClass :: Class -> Bool isCTupleClass cls = isTupleTyCon (classTyCon cls) isIPPred_maybe :: Type -> Maybe (FastString, Type) isIPPred_maybe ty = do (tc,[t1,t2]) <- splitTyConApp_maybe ty guard (isIPTyCon tc) x <- isStrLitTy t1 return (x,t2) {- Make PredTypes --------------------- Equality types --------------------------------- -} -- | Makes a lifted equality predicate at the given role mkPrimEqPredRole :: Role -> Type -> Type -> PredType mkPrimEqPredRole Nominal = mkPrimEqPred mkPrimEqPredRole Representational = mkReprPrimEqPred mkPrimEqPredRole Phantom = panic "mkPrimEqPredRole phantom" -- | Creates a primitive type equality predicate. -- Invariant: the types are not Coercions mkPrimEqPred :: Type -> Type -> Type mkPrimEqPred ty1 ty2 = TyConApp eqPrimTyCon [k1, k2, ty1, ty2] where k1 = typeKind ty1 k2 = typeKind ty2 -- | Creates a primite type equality predicate with explicit kinds mkHeteroPrimEqPred :: Kind -> Kind -> Type -> Type -> Type mkHeteroPrimEqPred k1 k2 ty1 ty2 = TyConApp eqPrimTyCon [k1, k2, ty1, ty2] -- | Creates a primitive representational type equality predicate -- with explicit kinds mkHeteroReprPrimEqPred :: Kind -> Kind -> Type -> Type -> Type mkHeteroReprPrimEqPred k1 k2 ty1 ty2 = TyConApp eqReprPrimTyCon [k1, k2, ty1, ty2] -- | Try to split up a coercion type into the types that it coerces splitCoercionType_maybe :: Type -> Maybe (Type, Type) splitCoercionType_maybe ty = do { (tc, [_, _, ty1, ty2]) <- splitTyConApp_maybe ty ; guard $ tc `hasKey` eqPrimTyConKey || tc `hasKey` eqReprPrimTyConKey ; return (ty1, ty2) } mkReprPrimEqPred :: Type -> Type -> Type mkReprPrimEqPred ty1 ty2 = TyConApp eqReprPrimTyCon [k1, k2, ty1, ty2] where k1 = typeKind ty1 k2 = typeKind ty2 equalityTyCon :: Role -> TyCon equalityTyCon Nominal = eqPrimTyCon equalityTyCon Representational = eqReprPrimTyCon equalityTyCon Phantom = eqPhantPrimTyCon -- --------------------- Dictionary types --------------------------------- mkClassPred :: Class -> [Type] -> PredType mkClassPred clas tys = TyConApp (classTyCon clas) tys isDictTy :: Type -> Bool isDictTy = isClassPred isDictLikeTy :: Type -> Bool -- Note [Dictionary-like types] isDictLikeTy ty | Just ty' <- coreView ty = isDictLikeTy ty' isDictLikeTy ty = case splitTyConApp_maybe ty of Just (tc, tys) | isClassTyCon tc -> True | isTupleTyCon tc -> all isDictLikeTy tys _other -> False {- 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. Decomposing PredType -} -- | A choice of equality relation. This is separate from the type 'Role' -- because 'Phantom' does not define a (non-trivial) equality relation. data EqRel = NomEq | ReprEq deriving (Eq, Ord) instance Outputable EqRel where ppr NomEq = text "nominal equality" ppr ReprEq = text "representational equality" eqRelRole :: EqRel -> Role eqRelRole NomEq = Nominal eqRelRole ReprEq = Representational data PredTree = ClassPred Class [Type] | EqPred EqRel Type Type | IrredPred PredType | ForAllPred [TyVarBinder] [PredType] PredType -- ForAllPred: see Note [Quantified constraints] in TcCanonical -- NB: There is no TuplePred case -- Tuple predicates like (Eq a, Ord b) are just treated -- as ClassPred, as if we had a tuple class with two superclasses -- class (c1, c2) => (%,%) c1 c2 classifyPredType :: PredType -> PredTree classifyPredType ev_ty = case splitTyConApp_maybe ev_ty of Just (tc, [_, _, ty1, ty2]) | tc `hasKey` eqReprPrimTyConKey -> EqPred ReprEq ty1 ty2 | tc `hasKey` eqPrimTyConKey -> EqPred NomEq ty1 ty2 Just (tc, tys) | Just clas <- tyConClass_maybe tc -> ClassPred clas tys _ | (tvs, rho) <- splitForAllTyVarBndrs ev_ty , (theta, pred) <- splitFunTys rho , not (null tvs && null theta) -> ForAllPred tvs theta pred | otherwise -> IrredPred ev_ty getClassPredTys :: HasDebugCallStack => PredType -> (Class, [Type]) getClassPredTys ty = case getClassPredTys_maybe ty of Just (clas, tys) -> (clas, tys) Nothing -> pprPanic "getClassPredTys" (ppr ty) getClassPredTys_maybe :: PredType -> Maybe (Class, [Type]) getClassPredTys_maybe ty = case splitTyConApp_maybe ty of Just (tc, tys) | Just clas <- tyConClass_maybe tc -> Just (clas, tys) _ -> Nothing getEqPredTys :: PredType -> (Type, Type) getEqPredTys ty = case splitTyConApp_maybe ty of Just (tc, [_, _, ty1, ty2]) | tc `hasKey` eqPrimTyConKey || tc `hasKey` eqReprPrimTyConKey -> (ty1, ty2) _ -> pprPanic "getEqPredTys" (ppr ty) getEqPredTys_maybe :: PredType -> Maybe (Role, Type, Type) getEqPredTys_maybe ty = case splitTyConApp_maybe ty of Just (tc, [_, _, ty1, ty2]) | tc `hasKey` eqPrimTyConKey -> Just (Nominal, ty1, ty2) | tc `hasKey` eqReprPrimTyConKey -> Just (Representational, ty1, ty2) _ -> Nothing getEqPredRole :: PredType -> Role getEqPredRole ty = eqRelRole (predTypeEqRel ty) -- | Get the equality relation relevant for a pred type. predTypeEqRel :: PredType -> EqRel predTypeEqRel ty | Just (tc, _) <- splitTyConApp_maybe ty , tc `hasKey` eqReprPrimTyConKey = ReprEq | otherwise = NomEq {- %************************************************************************ %* * Well-scoped tyvars * * ************************************************************************ -} -- | Do a topological sort on a list of tyvars, -- so that binders occur before occurrences -- E.g. given [ a::k, k::*, b::k ] -- it'll return a well-scoped list [ k::*, a::k, b::k ] -- -- This is a deterministic sorting operation -- (that is, doesn't depend on Uniques). toposortTyVars :: [TyCoVar] -> [TyCoVar] toposortTyVars tvs = reverse $ [ node_payload node | node <- topologicalSortG $ graphFromEdgedVerticesOrd nodes ] where var_ids :: VarEnv Int var_ids = mkVarEnv (zip tvs [1..]) nodes :: [ Node Int TyVar ] nodes = [ DigraphNode tv (lookupVarEnv_NF var_ids tv) (mapMaybe (lookupVarEnv var_ids) (tyCoVarsOfTypeList (tyVarKind tv))) | tv <- tvs ] -- | Extract a well-scoped list of variables from a deterministic set of -- variables. The result is deterministic. -- NB: There used to exist varSetElemsWellScoped :: VarSet -> [Var] which -- took a non-deterministic set and produced a non-deterministic -- well-scoped list. If you care about the list being well-scoped you also -- most likely care about it being in deterministic order. dVarSetElemsWellScoped :: DVarSet -> [Var] dVarSetElemsWellScoped = toposortTyVars . dVarSetElems -- | Get the free vars of a type in scoped order tyCoVarsOfTypeWellScoped :: Type -> [TyVar] tyCoVarsOfTypeWellScoped = toposortTyVars . tyCoVarsOfTypeList -- | Get the free vars of types in scoped order tyCoVarsOfTypesWellScoped :: [Type] -> [TyVar] tyCoVarsOfTypesWellScoped = toposortTyVars . tyCoVarsOfTypesList {- ************************************************************************ * * \subsection{Type families} * * ************************************************************************ -} mkFamilyTyConApp :: TyCon -> [Type] -> Type -- ^ Given a family instance TyCon and its arg types, return the -- corresponding family type. E.g: -- -- > data family T a -- > data instance T (Maybe b) = MkT b -- -- Where the instance tycon is :RTL, so: -- -- > mkFamilyTyConApp :RTL Int = T (Maybe Int) mkFamilyTyConApp tc tys | Just (fam_tc, fam_tys) <- tyConFamInst_maybe tc , let tvs = tyConTyVars tc fam_subst = ASSERT2( tvs `equalLength` tys, ppr tc <+> ppr tys ) zipTvSubst tvs tys = mkTyConApp fam_tc (substTys fam_subst fam_tys) | otherwise = mkTyConApp tc tys -- | Get the type on the LHS of a coercion induced by a type/data -- family instance. coAxNthLHS :: CoAxiom br -> Int -> Type coAxNthLHS ax ind = mkTyConApp (coAxiomTyCon ax) (coAxBranchLHS (coAxiomNthBranch ax ind)) -- | Pretty prints a 'TyCon', using the family instance in case of a -- representation tycon. For example: -- -- > data T [a] = ... -- -- In that case we want to print @T [a]@, where @T@ is the family 'TyCon' pprSourceTyCon :: TyCon -> SDoc pprSourceTyCon tycon | Just (fam_tc, tys) <- tyConFamInst_maybe tycon = ppr $ fam_tc `TyConApp` tys -- can't be FunTyCon | otherwise = ppr tycon -- @isTauTy@ tests if a type has no foralls isFamFreeTy :: Type -> Bool isFamFreeTy ty | Just ty' <- coreView ty = isFamFreeTy ty' isFamFreeTy (TyVarTy _) = True isFamFreeTy (LitTy {}) = True isFamFreeTy (TyConApp tc tys) = all isFamFreeTy tys && isFamFreeTyCon tc isFamFreeTy (AppTy a b) = isFamFreeTy a && isFamFreeTy b isFamFreeTy (FunTy a b) = isFamFreeTy a && isFamFreeTy b isFamFreeTy (ForAllTy _ ty) = isFamFreeTy ty isFamFreeTy (CastTy ty _) = isFamFreeTy ty isFamFreeTy (CoercionTy _) = False -- Not sure about this {- ************************************************************************ * * \subsection{Liftedness} * * ************************************************************************ -} -- | Returns Just True if this type is surely lifted, Just False -- if it is surely unlifted, Nothing if we can't be sure (i.e., it is -- levity polymorphic), and panics if the kind does not have the shape -- TYPE r. isLiftedType_maybe :: HasDebugCallStack => Type -> Maybe Bool isLiftedType_maybe ty = go (getRuntimeRep ty) where go rr | Just rr' <- coreView rr = go rr' go (TyConApp lifted_rep []) | lifted_rep `hasKey` liftedRepDataConKey = Just True go (TyConApp {}) = Just False -- everything else is unlifted go _ = Nothing -- levity polymorphic -- | See "Type#type_classification" for what an unlifted type is. -- Panics on levity polymorphic types. isUnliftedType :: HasDebugCallStack => Type -> Bool -- isUnliftedType returns True for forall'd unlifted types: -- x :: forall a. Int# -- I found bindings like these were getting floated to the top level. -- They are pretty bogus types, mind you. It would be better never to -- construct them isUnliftedType ty = not (isLiftedType_maybe ty `orElse` pprPanic "isUnliftedType" (ppr ty <+> dcolon <+> ppr (typeKind ty))) -- | Is this a type of kind RuntimeRep? (e.g. LiftedRep) isRuntimeRepKindedTy :: Type -> Bool isRuntimeRepKindedTy = isRuntimeRepTy . typeKind -- | Drops prefix of RuntimeRep constructors in 'TyConApp's. Useful for e.g. -- dropping 'LiftedRep arguments of unboxed tuple TyCon applications: -- -- dropRuntimeRepArgs [ 'LiftedRep, 'IntRep -- , String, Int# ] == [String, Int#] -- dropRuntimeRepArgs :: [Type] -> [Type] dropRuntimeRepArgs = dropWhile isRuntimeRepKindedTy -- | Extract the RuntimeRep classifier of a type. For instance, -- @getRuntimeRep_maybe Int = LiftedRep@. Returns 'Nothing' if this is not -- possible. getRuntimeRep_maybe :: HasDebugCallStack => Type -> Maybe Type getRuntimeRep_maybe = getRuntimeRepFromKind_maybe . typeKind -- | Extract the RuntimeRep classifier of a type. For instance, -- @getRuntimeRep_maybe Int = LiftedRep@. Panics if this is not possible. getRuntimeRep :: HasDebugCallStack => Type -> Type getRuntimeRep ty = case getRuntimeRep_maybe ty of Just r -> r Nothing -> pprPanic "getRuntimeRep" (ppr ty <+> dcolon <+> ppr (typeKind ty)) -- | Extract the RuntimeRep classifier of a type from its kind. For example, -- @getRuntimeRepFromKind * = LiftedRep@; Panics if this is not possible. getRuntimeRepFromKind :: HasDebugCallStack => Type -> Type getRuntimeRepFromKind k = case getRuntimeRepFromKind_maybe k of Just r -> r Nothing -> pprPanic "getRuntimeRepFromKind" (ppr k <+> dcolon <+> ppr (typeKind k)) -- | Extract the RuntimeRep classifier of a type from its kind. For example, -- @getRuntimeRepFromKind * = LiftedRep@; Returns 'Nothing' if this is not -- possible. getRuntimeRepFromKind_maybe :: HasDebugCallStack => Type -> Maybe Type getRuntimeRepFromKind_maybe = go where go k | Just k' <- coreView k = go k' go k | Just (_tc, [arg]) <- splitTyConApp_maybe k = ASSERT2( _tc `hasKey` tYPETyConKey, ppr k ) Just arg go _ = Nothing isUnboxedTupleType :: Type -> Bool isUnboxedTupleType ty = tyConAppTyCon (getRuntimeRep ty) `hasKey` tupleRepDataConKey -- NB: Do not use typePrimRep, as that can't tell the difference between -- unboxed tuples and unboxed sums isUnboxedSumType :: Type -> Bool isUnboxedSumType ty = tyConAppTyCon (getRuntimeRep ty) `hasKey` sumRepDataConKey -- | See "Type#type_classification" for what an algebraic type is. -- Should only be applied to /types/, as opposed to e.g. partially -- saturated type constructors isAlgType :: Type -> Bool isAlgType ty = case splitTyConApp_maybe ty of Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc ) isAlgTyCon tc _other -> False -- | Check whether a type is a data family type isDataFamilyAppType :: Type -> Bool isDataFamilyAppType ty = case tyConAppTyCon_maybe ty of Just tc -> isDataFamilyTyCon tc _ -> False -- | Computes whether an argument (or let right hand side) should -- be computed strictly or lazily, based only on its type. -- Currently, it's just 'isUnliftedType'. Panics on levity-polymorphic types. isStrictType :: HasDebugCallStack => Type -> Bool isStrictType = isUnliftedType isPrimitiveType :: Type -> Bool -- ^ Returns true of types that are opaque to Haskell. isPrimitiveType ty = case splitTyConApp_maybe ty of Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc ) isPrimTyCon tc _ -> False {- ************************************************************************ * * \subsection{Join points} * * ************************************************************************ -} -- | Determine whether a type could be the type of a join point of given total -- arity, according to the polymorphism rule. A join point cannot be polymorphic -- in its return type, since given -- join j @a @b x y z = e1 in e2, -- the types of e1 and e2 must be the same, and a and b are not in scope for e2. -- (See Note [The polymorphism rule of join points] in CoreSyn.) Returns False -- also if the type simply doesn't have enough arguments. -- -- Note that we need to know how many arguments (type *and* value) the putative -- join point takes; for instance, if -- j :: forall a. a -> Int -- then j could be a binary join point returning an Int, but it could *not* be a -- unary join point returning a -> Int. -- -- TODO: See Note [Excess polymorphism and join points] isValidJoinPointType :: JoinArity -> Type -> Bool isValidJoinPointType arity ty = valid_under emptyVarSet arity ty where valid_under tvs arity ty | arity == 0 = isEmptyVarSet (tvs `intersectVarSet` tyCoVarsOfType ty) | Just (t, ty') <- splitForAllTy_maybe ty = valid_under (tvs `extendVarSet` t) (arity-1) ty' | Just (_, res_ty) <- splitFunTy_maybe ty = valid_under tvs (arity-1) res_ty | otherwise = False {- Note [Excess polymorphism and join points] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In principle, if a function would be a join point except that it fails the polymorphism rule (see Note [The polymorphism rule of join points] in CoreSyn), it can still be made a join point with some effort. This is because all tail calls must return the same type (they return to the same context!), and thus if the return type depends on an argument, that argument must always be the same. For instance, consider: let f :: forall a. a -> Char -> [a] f @a x c = ... f @a y 'a' ... in ... f @Int 1 'b' ... f @Int 2 'c' ... (where the calls are tail calls). `f` fails the polymorphism rule because its return type is [a], where [a] is bound. But since the type argument is always 'Int', we can rewrite it as: let f' :: Int -> Char -> [Int] f' x c = ... f' y 'a' ... in ... f' 1 'b' ... f 2 'c' ... and now we can make f' a join point: join f' :: Int -> Char -> [Int] f' x c = ... jump f' y 'a' ... in ... jump f' 1 'b' ... jump f' 2 'c' ... It's not clear that this comes up often, however. TODO: Measure how often and add this analysis if necessary. See Trac #14620. ************************************************************************ * * \subsection{Sequencing on types} * * ************************************************************************ -} seqType :: Type -> () seqType (LitTy n) = n `seq` () seqType (TyVarTy tv) = tv `seq` () seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2 seqType (TyConApp tc tys) = tc `seq` seqTypes tys seqType (ForAllTy (TvBndr tv _) ty) = seqType (tyVarKind tv) `seq` seqType ty seqType (CastTy ty co) = seqType ty `seq` seqCo co seqType (CoercionTy co) = seqCo co seqTypes :: [Type] -> () seqTypes [] = () seqTypes (ty:tys) = seqType ty `seq` seqTypes tys {- ************************************************************************ * * Comparison for types (We don't use instances so that we know where it happens) * * ************************************************************************ Note [Equality on AppTys] ~~~~~~~~~~~~~~~~~~~~~~~~~ In our cast-ignoring equality, we want to say that the following two are equal: (Maybe |> co) (Int |> co') ~? Maybe Int But the left is an AppTy while the right is a TyConApp. The solution is to use repSplitAppTy_maybe to break up the TyConApp into its pieces and then continue. Easy to do, but also easy to forget to do. -} eqType :: Type -> Type -> Bool -- ^ Type equality on source types. Does not look through @newtypes@ or -- 'PredType's, but it does look through type synonyms. -- This first checks that the kinds of the types are equal and then -- checks whether the types are equal, ignoring casts and coercions. -- (The kind check is a recursive call, but since all kinds have type -- @Type@, there is no need to check the types of kinds.) -- See also Note [Non-trivial definitional equality] in TyCoRep. eqType t1 t2 = isEqual $ nonDetCmpType t1 t2 -- It's OK to use nonDetCmpType here and eqType is deterministic, -- nonDetCmpType does equality deterministically -- | Compare types with respect to a (presumably) non-empty 'RnEnv2'. eqTypeX :: RnEnv2 -> Type -> Type -> Bool eqTypeX env t1 t2 = isEqual $ nonDetCmpTypeX env t1 t2 -- It's OK to use nonDetCmpType here and eqTypeX is deterministic, -- nonDetCmpTypeX does equality deterministically -- | Type equality on lists of types, looking through type synonyms -- but not newtypes. eqTypes :: [Type] -> [Type] -> Bool eqTypes tys1 tys2 = isEqual $ nonDetCmpTypes tys1 tys2 -- It's OK to use nonDetCmpType here and eqTypes is deterministic, -- nonDetCmpTypes does equality deterministically eqVarBndrs :: RnEnv2 -> [Var] -> [Var] -> Maybe RnEnv2 -- Check that the var lists are the same length -- and have matching kinds; if so, extend the RnEnv2 -- Returns Nothing if they don't match eqVarBndrs env [] [] = Just env eqVarBndrs env (tv1:tvs1) (tv2:tvs2) | eqTypeX env (tyVarKind tv1) (tyVarKind tv2) = eqVarBndrs (rnBndr2 env tv1 tv2) tvs1 tvs2 eqVarBndrs _ _ _= Nothing -- Now here comes the real worker {- Note [nonDetCmpType nondeterminism] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ nonDetCmpType is implemented in terms of nonDetCmpTypeX. nonDetCmpTypeX uses nonDetCmpTc which compares TyCons by their Unique value. Using Uniques for ordering leads to nondeterminism. We hit the same problem in the TyVarTy case, comparing type variables is nondeterministic, note the call to nonDetCmpVar in nonDetCmpTypeX. See Note [Unique Determinism] for more details. -} nonDetCmpType :: Type -> Type -> Ordering nonDetCmpType t1 t2 -- we know k1 and k2 have the same kind, because they both have kind *. = nonDetCmpTypeX rn_env t1 t2 where rn_env = mkRnEnv2 (mkInScopeSet (tyCoVarsOfTypes [t1, t2])) nonDetCmpTypes :: [Type] -> [Type] -> Ordering nonDetCmpTypes ts1 ts2 = nonDetCmpTypesX rn_env ts1 ts2 where rn_env = mkRnEnv2 (mkInScopeSet (tyCoVarsOfTypes (ts1 ++ ts2))) -- | An ordering relation between two 'Type's (known below as @t1 :: k1@ -- and @t2 :: k2@) data TypeOrdering = TLT -- ^ @t1 < t2@ | TEQ -- ^ @t1 ~ t2@ and there are no casts in either, -- therefore we can conclude @k1 ~ k2@ | TEQX -- ^ @t1 ~ t2@ yet one of the types contains a cast so -- they may differ in kind. | TGT -- ^ @t1 > t2@ deriving (Eq, Ord, Enum, Bounded) nonDetCmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse -- See Note [Non-trivial definitional equality] in TyCoRep nonDetCmpTypeX env orig_t1 orig_t2 = case go env orig_t1 orig_t2 of -- If there are casts then we also need to do a comparison of the kinds of -- the types being compared TEQX -> toOrdering $ go env k1 k2 ty_ordering -> toOrdering ty_ordering where k1 = typeKind orig_t1 k2 = typeKind orig_t2 toOrdering :: TypeOrdering -> Ordering toOrdering TLT = LT toOrdering TEQ = EQ toOrdering TEQX = EQ toOrdering TGT = GT liftOrdering :: Ordering -> TypeOrdering liftOrdering LT = TLT liftOrdering EQ = TEQ liftOrdering GT = TGT thenCmpTy :: TypeOrdering -> TypeOrdering -> TypeOrdering thenCmpTy TEQ rel = rel thenCmpTy TEQX rel = hasCast rel thenCmpTy rel _ = rel hasCast :: TypeOrdering -> TypeOrdering hasCast TEQ = TEQX hasCast rel = rel -- Returns both the resulting ordering relation between the two types -- and whether either contains a cast. go :: RnEnv2 -> Type -> Type -> TypeOrdering go env t1 t2 | Just t1' <- coreView t1 = go env t1' t2 | Just t2' <- coreView t2 = go env t1 t2' go env (TyVarTy tv1) (TyVarTy tv2) = liftOrdering $ rnOccL env tv1 `nonDetCmpVar` rnOccR env tv2 go env (ForAllTy (TvBndr tv1 _) t1) (ForAllTy (TvBndr tv2 _) t2) = go env (tyVarKind tv1) (tyVarKind tv2) `thenCmpTy` go (rnBndr2 env tv1 tv2) t1 t2 -- See Note [Equality on AppTys] go env (AppTy s1 t1) ty2 | Just (s2, t2) <- repSplitAppTy_maybe ty2 = go env s1 s2 `thenCmpTy` go env t1 t2 go env ty1 (AppTy s2 t2) | Just (s1, t1) <- repSplitAppTy_maybe ty1 = go env s1 s2 `thenCmpTy` go env t1 t2 go env (FunTy s1 t1) (FunTy s2 t2) = go env s1 s2 `thenCmpTy` go env t1 t2 go env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = liftOrdering (tc1 `nonDetCmpTc` tc2) `thenCmpTy` gos env tys1 tys2 go _ (LitTy l1) (LitTy l2) = liftOrdering (compare l1 l2) go env (CastTy t1 _) t2 = hasCast $ go env t1 t2 go env t1 (CastTy t2 _) = hasCast $ go env t1 t2 go _ (CoercionTy {}) (CoercionTy {}) = TEQ -- Deal with the rest: TyVarTy < CoercionTy < AppTy < LitTy < TyConApp < ForAllTy go _ ty1 ty2 = liftOrdering $ (get_rank ty1) `compare` (get_rank ty2) where get_rank :: Type -> Int get_rank (CastTy {}) = pprPanic "nonDetCmpTypeX.get_rank" (ppr [ty1,ty2]) get_rank (TyVarTy {}) = 0 get_rank (CoercionTy {}) = 1 get_rank (AppTy {}) = 3 get_rank (LitTy {}) = 4 get_rank (TyConApp {}) = 5 get_rank (FunTy {}) = 6 get_rank (ForAllTy {}) = 7 gos :: RnEnv2 -> [Type] -> [Type] -> TypeOrdering gos _ [] [] = TEQ gos _ [] _ = TLT gos _ _ [] = TGT gos env (ty1:tys1) (ty2:tys2) = go env ty1 ty2 `thenCmpTy` gos env tys1 tys2 ------------- nonDetCmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering nonDetCmpTypesX _ [] [] = EQ nonDetCmpTypesX env (t1:tys1) (t2:tys2) = nonDetCmpTypeX env t1 t2 `thenCmp` nonDetCmpTypesX env tys1 tys2 nonDetCmpTypesX _ [] _ = LT nonDetCmpTypesX _ _ [] = GT ------------- -- | Compare two 'TyCon's. NB: This should /never/ see 'Constraint' (as -- recognized by Kind.isConstraintKindCon) which is considered a synonym for -- 'Type' in Core. -- See Note [Kind Constraint and kind Type] in Kind. -- See Note [nonDetCmpType nondeterminism] nonDetCmpTc :: TyCon -> TyCon -> Ordering nonDetCmpTc tc1 tc2 = ASSERT( not (isConstraintKindCon tc1) && not (isConstraintKindCon tc2) ) u1 `nonDetCmpUnique` u2 where u1 = tyConUnique tc1 u2 = tyConUnique tc2 {- ************************************************************************ * * The kind of a type * * ************************************************************************ -} typeKind :: HasDebugCallStack => Type -> Kind typeKind (TyConApp tc tys) = piResultTys (tyConKind tc) tys typeKind (AppTy fun arg) = typeKind_apps fun [arg] typeKind (LitTy l) = typeLiteralKind l typeKind (FunTy {}) = liftedTypeKind typeKind (TyVarTy tyvar) = tyVarKind tyvar typeKind (CastTy _ty co) = pSnd $ coercionKind co typeKind (CoercionTy co) = coercionType co typeKind ty@(ForAllTy {}) = case occCheckExpand tvs k of Just k' -> k' Nothing -> pprPanic "typeKind" (ppr ty $$ ppr k $$ ppr tvs $$ ppr body) where (tvs, body) = splitForAllTys ty k = typeKind body typeKind_apps :: HasDebugCallStack => Type -> [Type] -> Kind -- The sole purpose of the function is to accumulate -- the type arugments, so we can call piResultTys, rather than -- a succession of calls to piResultTy (which is asymptotically -- less efficient as the number of arguments increases) typeKind_apps (AppTy fun arg) args = typeKind_apps fun (arg:args) typeKind_apps fun args = piResultTys (typeKind fun) args -------------------------- typeLiteralKind :: TyLit -> Kind typeLiteralKind l = case l of NumTyLit _ -> typeNatKind StrTyLit _ -> typeSymbolKind -- | Returns True if a type is levity polymorphic. Should be the same -- as (isKindLevPoly . typeKind) but much faster. -- Precondition: The type has kind (TYPE blah) isTypeLevPoly :: Type -> Bool isTypeLevPoly = go where go ty@(TyVarTy {}) = check_kind ty go ty@(AppTy {}) = check_kind ty go ty@(TyConApp tc _) | not (isTcLevPoly tc) = False | otherwise = check_kind ty go (ForAllTy _ ty) = go ty go (FunTy {}) = False go (LitTy {}) = False go ty@(CastTy {}) = check_kind ty go ty@(CoercionTy {}) = pprPanic "isTypeLevPoly co" (ppr ty) check_kind = isKindLevPoly . typeKind -- | Looking past all pi-types, is the end result potentially levity polymorphic? -- Example: True for (forall r (a :: TYPE r). String -> a) -- Example: False for (forall r1 r2 (a :: TYPE r1) (b :: TYPE r2). a -> b -> Type) resultIsLevPoly :: Type -> Bool resultIsLevPoly = isTypeLevPoly . snd . splitPiTys {- ********************************************************************** * * Occurs check expansion %* * %********************************************************************* -} {- 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 occCheckExpand b (F Int b) = Just [Int] but occCheckExpand 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 occCheckExpand b (F (G b)) = Just (F Char) even though we could also expand F to get rid of b. -} occCheckExpand :: [Var] -> Type -> Maybe Type -- See Note [Occurs check expansion] -- 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. occCheckExpand vs_to_avoid ty = go (mkVarSet vs_to_avoid, emptyVarEnv) ty where go :: (VarSet, VarEnv TyVar) -> Type -> Maybe Type -- The VarSet is the set of variables we are trying to avoid -- The VarEnv carries mappings necessary -- because of kind expansion go cxt@(as, env) (TyVarTy tv') | tv' `elemVarSet` as = Nothing | Just tv'' <- lookupVarEnv env tv' = return (mkTyVarTy tv'') | otherwise = do { tv'' <- go_var cxt tv' ; return (mkTyVarTy tv'') } go _ ty@(LitTy {}) = return ty go cxt (AppTy ty1 ty2) = do { ty1' <- go cxt ty1 ; ty2' <- go cxt ty2 ; return (mkAppTy ty1' ty2') } go cxt (FunTy ty1 ty2) = do { ty1' <- go cxt ty1 ; ty2' <- go cxt ty2 ; return (mkFunTy ty1' ty2') } go cxt@(as, env) (ForAllTy (TvBndr tv vis) body_ty) = do { ki' <- go cxt (tyVarKind tv) ; let tv' = setTyVarKind tv ki' env' = extendVarEnv env tv tv' as' = as `delVarSet` tv ; body' <- go (as', env') body_ty ; return (ForAllTy (TvBndr tv' vis) 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 cxt ty@(TyConApp tc tys) = case mapM (go cxt) tys of Just tys' -> return (mkTyConApp tc tys') Nothing | Just ty' <- tcView ty -> go cxt ty' | otherwise -> Nothing -- Failing that, try to expand a synonym go cxt (CastTy ty co) = do { ty' <- go cxt ty ; co' <- go_co cxt co ; return (mkCastTy ty' co') } go cxt (CoercionTy co) = do { co' <- go_co cxt co ; return (mkCoercionTy co') } ------------------ go_var cxt v = do { k' <- go cxt (varType v) ; return (setVarType v k') } -- Works for TyVar and CoVar -- See Note [Occurrence checking: look inside kinds] ------------------ go_co cxt (Refl r ty) = do { ty' <- go cxt ty ; return (mkReflCo r ty') } -- Note: Coercions do not contain type synonyms go_co cxt (TyConAppCo r tc args) = do { args' <- mapM (go_co cxt) args ; return (mkTyConAppCo r tc args') } go_co cxt (AppCo co arg) = do { co' <- go_co cxt co ; arg' <- go_co cxt arg ; return (mkAppCo co' arg') } go_co cxt@(as, env) (ForAllCo tv kind_co body_co) = do { kind_co' <- go_co cxt kind_co ; let tv' = setTyVarKind tv $ pFst (coercionKind kind_co') env' = extendVarEnv env tv tv' as' = as `delVarSet` tv ; body' <- go_co (as', env') body_co ; return (ForAllCo tv' kind_co' body') } go_co cxt (FunCo r co1 co2) = do { co1' <- go_co cxt co1 ; co2' <- go_co cxt co2 ; return (mkFunCo r co1' co2') } go_co cxt (CoVarCo c) = do { c' <- go_var cxt c ; return (mkCoVarCo c') } go_co cxt (HoleCo h) = do { c' <- go_var cxt (ch_co_var h) ; return (HoleCo (h { ch_co_var = c' })) } go_co cxt (AxiomInstCo ax ind args) = do { args' <- mapM (go_co cxt) args ; return (mkAxiomInstCo ax ind args') } go_co cxt (UnivCo p r ty1 ty2) = do { p' <- go_prov cxt p ; ty1' <- go cxt ty1 ; ty2' <- go cxt ty2 ; return (mkUnivCo p' r ty1' ty2') } go_co cxt (SymCo co) = do { co' <- go_co cxt co ; return (mkSymCo co') } go_co cxt (TransCo co1 co2) = do { co1' <- go_co cxt co1 ; co2' <- go_co cxt co2 ; return (mkTransCo co1' co2') } go_co cxt (NthCo r n co) = do { co' <- go_co cxt co ; return (mkNthCo r n co') } go_co cxt (LRCo lr co) = do { co' <- go_co cxt co ; return (mkLRCo lr co') } go_co cxt (InstCo co arg) = do { co' <- go_co cxt co ; arg' <- go_co cxt arg ; return (mkInstCo co' arg') } go_co cxt (CoherenceCo co1 co2) = do { co1' <- go_co cxt co1 ; co2' <- go_co cxt co2 ; return (mkCoherenceCo co1' co2') } go_co cxt (KindCo co) = do { co' <- go_co cxt co ; return (mkKindCo co') } go_co cxt (SubCo co) = do { co' <- go_co cxt co ; return (mkSubCo co') } go_co cxt (AxiomRuleCo ax cs) = do { cs' <- mapM (go_co cxt) cs ; return (mkAxiomRuleCo ax cs') } ------------------ go_prov _ UnsafeCoerceProv = return UnsafeCoerceProv go_prov cxt (PhantomProv co) = PhantomProv <$> go_co cxt co go_prov cxt (ProofIrrelProv co) = ProofIrrelProv <$> go_co cxt co go_prov _ p@(PluginProv _) = return p {- %************************************************************************ %* * Miscellaneous functions %* * %************************************************************************ -} -- | All type constructors occurring in the type; looking through type -- synonyms, but not newtypes. -- When it finds a Class, it returns the class TyCon. tyConsOfType :: Type -> UniqSet TyCon tyConsOfType ty = go ty where go :: Type -> UniqSet TyCon -- The UniqSet does duplicate elim go ty | Just ty' <- coreView ty = go ty' go (TyVarTy {}) = emptyUniqSet go (LitTy {}) = emptyUniqSet go (TyConApp tc tys) = go_tc tc `unionUniqSets` go_s tys go (AppTy a b) = go a `unionUniqSets` go b go (FunTy a b) = go a `unionUniqSets` go b `unionUniqSets` go_tc funTyCon go (ForAllTy (TvBndr tv _) ty) = go ty `unionUniqSets` go (tyVarKind tv) go (CastTy ty co) = go ty `unionUniqSets` go_co co go (CoercionTy co) = go_co co go_co (Refl _ ty) = go ty go_co (TyConAppCo _ tc args) = go_tc tc `unionUniqSets` go_cos args go_co (AppCo co arg) = go_co co `unionUniqSets` go_co arg go_co (ForAllCo _ kind_co co) = go_co kind_co `unionUniqSets` go_co co go_co (FunCo _ co1 co2) = go_co co1 `unionUniqSets` go_co co2 go_co (AxiomInstCo ax _ args) = go_ax ax `unionUniqSets` go_cos args go_co (UnivCo p _ t1 t2) = go_prov p `unionUniqSets` go t1 `unionUniqSets` go t2 go_co (CoVarCo {}) = emptyUniqSet go_co (HoleCo {}) = emptyUniqSet go_co (SymCo co) = go_co co go_co (TransCo co1 co2) = go_co co1 `unionUniqSets` go_co co2 go_co (NthCo _ _ co) = go_co co go_co (LRCo _ co) = go_co co go_co (InstCo co arg) = go_co co `unionUniqSets` go_co arg go_co (CoherenceCo co1 co2) = go_co co1 `unionUniqSets` go_co co2 go_co (KindCo co) = go_co co go_co (SubCo co) = go_co co go_co (AxiomRuleCo _ cs) = go_cos cs go_prov UnsafeCoerceProv = emptyUniqSet go_prov (PhantomProv co) = go_co co go_prov (ProofIrrelProv co) = go_co co go_prov (PluginProv _) = emptyUniqSet -- this last case can happen from the tyConsOfType used from -- checkTauTvUpdate go_s tys = foldr (unionUniqSets . go) emptyUniqSet tys go_cos cos = foldr (unionUniqSets . go_co) emptyUniqSet cos go_tc tc = unitUniqSet tc go_ax ax = go_tc $ coAxiomTyCon ax -- | Find the result 'Kind' of a type synonym, -- after applying it to its 'arity' number of type variables -- Actually this function works fine on data types too, -- but they'd always return '*', so we never need to ask synTyConResKind :: TyCon -> Kind synTyConResKind tycon = piResultTys (tyConKind tycon) (mkTyVarTys (tyConTyVars tycon)) -- | Retrieve the free variables in this type, splitting them based -- on whether they are used visibly or invisibly. Invisible ones come -- first. splitVisVarsOfType :: Type -> Pair TyCoVarSet splitVisVarsOfType orig_ty = Pair invis_vars vis_vars where Pair invis_vars1 vis_vars = go orig_ty invis_vars = invis_vars1 `minusVarSet` vis_vars go (TyVarTy tv) = Pair (tyCoVarsOfType $ tyVarKind tv) (unitVarSet tv) go (AppTy t1 t2) = go t1 `mappend` go t2 go (TyConApp tc tys) = go_tc tc tys go (FunTy t1 t2) = go t1 `mappend` go t2 go (ForAllTy (TvBndr tv _) ty) = ((`delVarSet` tv) <$> go ty) `mappend` (invisible (tyCoVarsOfType $ tyVarKind tv)) go (LitTy {}) = mempty go (CastTy ty co) = go ty `mappend` invisible (tyCoVarsOfCo co) go (CoercionTy co) = invisible $ tyCoVarsOfCo co invisible vs = Pair vs emptyVarSet go_tc tc tys = let (invis, vis) = partitionInvisibles tc id tys in invisible (tyCoVarsOfTypes invis) `mappend` foldMap go vis splitVisVarsOfTypes :: [Type] -> Pair TyCoVarSet splitVisVarsOfTypes = foldMap splitVisVarsOfType modifyJoinResTy :: Int -- Number of binders to skip -> (Type -> Type) -- Function to apply to result type -> Type -- Type of join point -> Type -- New type -- INVARIANT: If any of the first n binders are foralls, those tyvars cannot -- appear in the original result type. See isValidJoinPointType. modifyJoinResTy orig_ar f orig_ty = go orig_ar orig_ty where go 0 ty = f ty go n ty | Just (arg_bndr, res_ty) <- splitPiTy_maybe ty = mkPiTy arg_bndr (go (n-1) res_ty) | otherwise = pprPanic "modifyJoinResTy" (ppr orig_ar <+> ppr orig_ty) setJoinResTy :: Int -- Number of binders to skip -> Type -- New result type -> Type -- Type of join point -> Type -- New type -- INVARIANT: Same as for modifyJoinResTy setJoinResTy ar new_res_ty ty = modifyJoinResTy ar (const new_res_ty) ty {- %************************************************************************ %* * Pretty-printing %* * %************************************************************************ Most pretty-printing is either in TyCoRep or IfaceType. -} -- | This variant preserves any use of TYPE in a type, effectively -- locally setting -fprint-explicit-runtime-reps. pprWithTYPE :: Type -> SDoc pprWithTYPE ty = updSDocDynFlags (flip gopt_set Opt_PrintExplicitRuntimeReps) $ ppr ty