-- (c) The University of Glasgow 2006 -- (c) The GRASP/AQUA Project, Glasgow University, 1998 -- -- Type - public interface {-# LANGUAGE FlexibleContexts, PatternSynonyms, ViewPatterns, MultiWayIf #-} {-# OPTIONS_GHC -fno-warn-orphans #-} -- | Main functions for manipulating types and type-related things module GHC.Core.Type ( -- Note some of this is just re-exports from TyCon.. -- * Main data types representing Types -- $type_classification -- $representation_types Type, ForAllTyFlag(..), FunTyFlag(..), Specificity(..), KindOrType, PredType, ThetaType, FRRType, Var, TyVar, isTyVar, TyCoVar, PiTyBinder, ForAllTyBinder, TyVarBinder, Mult, Scaled, KnotTied, RuntimeRepType, -- ** Constructing and deconstructing types mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, repGetTyVar_maybe, getCastedTyVar_maybe, tyVarKind, varType, mkAppTy, mkAppTys, splitAppTy, splitAppTys, splitAppTysNoView, splitAppTy_maybe, splitAppTyNoView_maybe, tcSplitAppTyNoView_maybe, mkFunTy, mkVisFunTy, mkVisFunTyMany, mkVisFunTysMany, mkScaledFunTys, mkInvisFunTy, mkInvisFunTys, tcMkVisFunTy, tcMkScaledFunTys, tcMkInvisFunTy, splitFunTy, splitFunTy_maybe, splitFunTys, funResultTy, funArgTy, funTyConAppTy_maybe, funTyFlagTyCon, tyConAppFunTy_maybe, tyConAppFunCo_maybe, mkFunctionType, mkScaledFunctionTys, chooseFunTyFlag, mkTyConApp, mkTyConTy, tyConAppTyCon_maybe, tyConAppTyConPicky_maybe, tyConAppArgs_maybe, tyConAppTyCon, tyConAppArgs, splitTyConApp_maybe, splitTyConAppNoView_maybe, splitTyConApp, tcSplitTyConApp, tcSplitTyConApp_maybe, mkForAllTy, mkForAllTys, mkInvisForAllTys, mkTyCoInvForAllTys, mkSpecForAllTy, mkSpecForAllTys, mkVisForAllTys, mkTyCoInvForAllTy, mkInfForAllTy, mkInfForAllTys, splitForAllTyCoVars, splitForAllReqTyBinders, splitForAllInvisTyBinders, splitForAllForAllTyBinders, splitForAllTyCoVar_maybe, splitForAllTyCoVar, splitForAllTyVar_maybe, splitForAllCoVar_maybe, splitPiTy_maybe, splitPiTy, splitPiTys, getRuntimeArgTys, mkTyConBindersPreferAnon, mkPiTy, mkPiTys, piResultTy, piResultTys, applyTysX, dropForAlls, mkFamilyTyConApp, buildSynTyCon, mkNumLitTy, isNumLitTy, mkStrLitTy, isStrLitTy, mkCharLitTy, isCharLitTy, isLitTy, isPredTy, getRuntimeRep, splitRuntimeRep_maybe, kindRep_maybe, kindRep, getLevity, levityType_maybe, mkCastTy, mkCoercionTy, splitCastTy_maybe, userTypeError_maybe, pprUserTypeErrorTy, coAxNthLHS, stripCoercionTy, splitInvisPiTys, splitInvisPiTysN, invisibleTyBndrCount, filterOutInvisibleTypes, filterOutInferredTypes, partitionInvisibleTypes, partitionInvisibles, tyConForAllTyFlags, appTyForAllTyFlags, -- ** Analyzing types TyCoMapper(..), mapTyCo, mapTyCoX, TyCoFolder(..), foldTyCo, noView, -- (Newtypes) newTyConInstRhs, -- ** Binders mkForAllTyBinder, mkForAllTyBinders, mkTyVarBinder, mkTyVarBinders, tyVarSpecToBinders, isAnonPiTyBinder, binderVar, binderVars, binderType, binderFlag, binderFlags, piTyBinderType, namedPiTyBinder_maybe, anonPiTyBinderType_maybe, isVisibleForAllTyFlag, isInvisibleForAllTyFlag, isVisiblePiTyBinder, isInvisiblePiTyBinder, isNamedPiTyBinder, tyConBindersPiTyBinders, -- ** Predicates on types isTyVarTy, isFunTy, isCoercionTy, isCoercionTy_maybe, isForAllTy, isForAllTy_ty, isForAllTy_co, isPiTy, isTauTy, isFamFreeTy, isCoVarType, isAtomicTy, isValidJoinPointType, tyConAppNeedsKindSig, -- * Space-saving construction mkTYPEapp, mkTYPEapp_maybe, mkCONSTRAINTapp, mkCONSTRAINTapp_maybe, mkBoxedRepApp_maybe, mkTupleRepApp_maybe, typeOrConstraintKind, -- *** Levity and boxity sORTKind_maybe, typeTypeOrConstraint, typeLevity_maybe, isLiftedTypeKind, isUnliftedTypeKind, pickyIsLiftedTypeKind, isLiftedRuntimeRep, isUnliftedRuntimeRep, runtimeRepLevity_maybe, isBoxedRuntimeRep, isLiftedLevity, isUnliftedLevity, isUnliftedType, isBoxedType, isUnboxedTupleType, isUnboxedSumType, kindBoxedRepLevity_maybe, mightBeLiftedType, mightBeUnliftedType, isAlgType, isDataFamilyAppType, isPrimitiveType, isStrictType, isLevityTy, isLevityVar, isRuntimeRepTy, isRuntimeRepVar, isRuntimeRepKindedTy, dropRuntimeRepArgs, -- * Multiplicity isMultiplicityTy, isMultiplicityVar, unrestricted, linear, tymult, mkScaled, irrelevantMult, scaledSet, pattern OneTy, pattern ManyTy, isOneTy, isManyTy, isLinearType, -- * Main data types representing Kinds Kind, -- ** Finding the kind of a type typeKind, typeHasFixedRuntimeRep, argsHaveFixedRuntimeRep, tcIsLiftedTypeKind, isConstraintKind, isConstraintLikeKind, returnsConstraintKind, tcIsBoxedTypeKind, isTypeLikeKind, -- ** Common Kind liftedTypeKind, unliftedTypeKind, -- * Type free variables tyCoFVsOfType, tyCoFVsBndr, tyCoFVsVarBndr, tyCoFVsVarBndrs, tyCoVarsOfType, tyCoVarsOfTypes, tyCoVarsOfTypeDSet, coVarsOfType, coVarsOfTypes, anyFreeVarsOfType, anyFreeVarsOfTypes, noFreeVarsOfType, expandTypeSynonyms, typeSize, occCheckExpand, -- ** Closing over kinds closeOverKindsDSet, closeOverKindsList, closeOverKinds, -- * Well-scoped lists of variables scopedSort, tyCoVarsOfTypeWellScoped, tyCoVarsOfTypesWellScoped, -- * Forcing evaluation of types seqType, seqTypes, -- * Other views onto Types coreView, tyConsOfType, -- * Main type substitution data types TvSubstEnv, -- Representation widely visible IdSubstEnv, Subst(..), -- Representation visible to a few friends -- ** Manipulating type substitutions emptyTvSubstEnv, emptySubst, mkEmptySubst, mkSubst, zipTvSubst, mkTvSubstPrs, zipTCvSubst, notElemSubst, getTvSubstEnv, zapSubst, getSubstInScope, setInScope, getSubstRangeTyCoFVs, extendSubstInScope, extendSubstInScopeList, extendSubstInScopeSet, extendTCvSubst, extendCvSubst, extendTvSubst, extendTvSubstBinderAndInScope, extendTvSubstList, extendTvSubstAndInScope, extendTCvSubstList, extendTvSubstWithClone, extendTCvSubstWithClone, isInScope, composeTCvSubst, zipTyEnv, zipCoEnv, isEmptySubst, unionSubst, isEmptyTCvSubst, -- ** Performing substitution on types and kinds substTy, substTys, substScaledTy, substScaledTys, substTyWith, substTysWith, substTheta, substTyAddInScope, substTyUnchecked, substTysUnchecked, substScaledTyUnchecked, substScaledTysUnchecked, substThetaUnchecked, substTyWithUnchecked, substCo, substCoUnchecked, substCoWithUnchecked, substTyVarBndr, substTyVarBndrs, substTyVar, substTyVars, substVarBndr, substVarBndrs, substTyCoBndr, substTyVarToTyVar, cloneTyVarBndr, cloneTyVarBndrs, lookupTyVar, -- * Tidying type related things up for printing tidyType, tidyTypes, tidyOpenType, tidyOpenTypes, tidyVarBndr, tidyVarBndrs, tidyFreeTyCoVars, tidyOpenTyCoVar, tidyOpenTyCoVars, tidyTyCoVarOcc, tidyTopType, tidyForAllTyBinder, tidyForAllTyBinders, -- * Kinds isTYPEorCONSTRAINT, isConcrete, isFixedRuntimeRepKind, ) where import GHC.Prelude import GHC.Types.Basic -- We import the representation and primitive functions from GHC.Core.TyCo.Rep. -- Many things are reexported, but not the representation! import GHC.Core.TyCo.Rep import GHC.Core.TyCo.Subst import GHC.Core.TyCo.Tidy import GHC.Core.TyCo.FVs -- friends: import GHC.Types.Var import GHC.Types.Var.Env import GHC.Types.Var.Set import GHC.Types.Unique.Set import GHC.Core.TyCon import GHC.Builtin.Types.Prim import {-# SOURCE #-} GHC.Builtin.Types ( charTy, naturalTy , typeSymbolKind, liftedTypeKind, unliftedTypeKind , constraintKind, zeroBitTypeKind , manyDataConTy, oneDataConTy , liftedRepTy, unliftedRepTy, zeroBitRepTy ) import GHC.Types.Name( Name ) import GHC.Builtin.Names import GHC.Core.Coercion.Axiom import {-# SOURCE #-} GHC.Core.Coercion ( mkNomReflCo, mkGReflCo, mkReflCo , mkTyConAppCo, mkAppCo , mkForAllCo, mkFunCo2, mkAxiomInstCo, mkUnivCo , mkSymCo, mkTransCo, mkSelCo, mkLRCo, mkInstCo , mkKindCo, mkSubCo, mkFunCo1 , decomposePiCos, coercionKind , coercionRKind, coercionType , isReflexiveCo, seqCo , topNormaliseNewType_maybe ) import {-# SOURCE #-} GHC.Tc.Utils.TcType ( isConcreteTyVar ) -- others import GHC.Utils.Misc import GHC.Utils.FV import GHC.Utils.Outputable import GHC.Utils.Panic import GHC.Utils.Panic.Plain import GHC.Data.FastString import Control.Monad ( guard ) import GHC.Data.Maybe ( orElse, isJust ) -- $type_classification -- #type_classification# -- -- Types are any, but at least one, of: -- -- [Boxed] Iff its representation is a pointer to an object on the -- GC'd heap. Operationally, heap objects can be entered as -- a means of evaluation. -- -- [Lifted] Iff it has bottom as an element: An instance of a -- lifted type might diverge when evaluated. -- GHC Haskell's unboxed types are unlifted. -- An unboxed, but lifted type is not very useful. -- (Example: A byte-represented type, where evaluating 0xff -- computes the 12345678th collatz number modulo 0xff.) -- 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. There are algebraic types that -- are not lifted types, like unlifted data types or -- unboxed tuples. -- -- [Data] Iff it is a type declared with @data@, or a boxed tuple. -- There are also /unlifted/ data types. -- -- [Primitive] Iff it is a built-in type that can't be expressed in Haskell. -- -- [Unlifted] Anything that isn't lifted is considered unlifted. -- -- 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 its abilities. If you don't want this -- to happen, use the equivalent functions from the "TcType" module. {- ************************************************************************ * * Type representation * * ************************************************************************ -} 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 does not look through type family applications. -- -- By being non-recursive and inlined, this case analysis gets efficiently -- joined onto the case analysis that the caller is already doing coreView (TyConApp tc tys) = expandSynTyConApp_maybe tc tys coreView _ = Nothing -- See Note [Inlining coreView]. {-# INLINE coreView #-} coreFullView, core_full_view :: Type -> Type -- ^ Iterates 'coreView' until there is no more to synonym to expand. -- NB: coreFullView is non-recursive and can be inlined; -- core_full_view is the recursive one -- See Note [Inlining coreView]. coreFullView ty@(TyConApp tc _) | isTypeSynonymTyCon tc = core_full_view ty coreFullView ty = ty {-# INLINE coreFullView #-} core_full_view ty | Just ty' <- coreView ty = core_full_view ty' | otherwise = ty ----------------------------------------------- -- | @expandSynTyConApp_maybe tc tys@ expands the RHS of type synonym @tc@ -- instantiated at arguments @tys@, or returns 'Nothing' if @tc@ is not a -- synonym. expandSynTyConApp_maybe :: TyCon -> [Type] -> Maybe Type {-# INLINE expandSynTyConApp_maybe #-} -- This INLINE will inline the call to expandSynTyConApp_maybe in coreView, -- which will eliminate the allocation Just/Nothing in the result -- Don't be tempted to make `expand_syn` (which is NOINLINE) return the -- Just/Nothing, else you'll increase allocation expandSynTyConApp_maybe tc arg_tys | Just (tvs, rhs) <- synTyConDefn_maybe tc , arg_tys `saturates` tyConArity tc = Just (expand_syn tvs rhs arg_tys) | otherwise = Nothing saturates :: [Type] -> Arity -> Bool saturates _ 0 = True saturates [] _ = False saturates (_:tys) n = assert( n >= 0 ) $ saturates tys (n-1) -- Arities are always positive; the assertion just checks -- that, to avoid an ininite loop in the bad case -- | A helper for 'expandSynTyConApp_maybe' to avoid inlining this cold path -- into call-sites. -- -- Precondition: the call is saturated or over-saturated; -- i.e. length tvs <= length arg_tys expand_syn :: [TyVar] -- ^ the variables bound by the synonym -> Type -- ^ the RHS of the synonym -> [Type] -- ^ the type arguments the synonym is instantiated at. -> Type {-# NOINLINE expand_syn #-} -- We never want to inline this cold-path. expand_syn tvs rhs arg_tys -- No substitution necessary if either tvs or tys is empty -- This is both more efficient, and steers clear of an infinite -- loop; see Note [Care using synonyms to compress types] | null arg_tys = assert (null tvs) rhs | null tvs = mkAppTys rhs arg_tys | otherwise = go empty_subst tvs arg_tys where empty_subst = mkEmptySubst in_scope in_scope = mkInScopeSet $ shallowTyCoVarsOfTypes $ arg_tys -- The free vars of 'rhs' should all be bound by 'tenv', -- so we only need the free vars of tys -- See also Note [The substitution invariant] in GHC.Core.TyCo.Subst. go subst [] tys | null tys = rhs' -- Exactly Saturated | otherwise = mkAppTys rhs' tys -- Its important to use mkAppTys, rather than (foldl AppTy), -- because the function part might well return a -- partially-applied type constructor; indeed, usually will! where rhs' = substTy subst rhs go subst (tv:tvs) (ty:tys) = go (extendTvSubst subst tv ty) tvs tys go _ (_:_) [] = pprPanic "expand_syn" (ppr tvs $$ ppr rhs $$ ppr arg_tys) -- Under-saturated, precondition failed {- Note [Inlining coreView] ~~~~~~~~~~~~~~~~~~~~~~~~~~~ It is very common to have a function f :: Type -> ... f ty | Just ty' <- coreView ty = f ty' f (TyVarTy ...) = ... f ... = ... If f is not otherwise recursive, the initial call to coreView causes f to become recursive, which kills the possibility of inlining. Instead, for non-recursive functions, we prefer to use coreFullView, which guarantees to unwrap top-level type synonyms. It can be inlined and is efficient and non-allocating in its fast path. For this to really be fast, all calls made on its fast path must also be inlined, linked back to this Note. -} {- ********************************************************************* * * expandTypeSynonyms * * ********************************************************************* -} 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 (mkEmptySubst in_scope) ty where in_scope = mkInScopeSet (tyCoVarsOfType ty) go subst (TyConApp tc tys) | ExpandsSyn 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 -- (#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 ty@(FunTy _ mult arg res) = ty { ft_mult = go subst mult, ft_arg = go subst arg, ft_res = go subst res } go subst (ForAllTy (Bndr tv vis) t) = let (subst', tv') = substVarBndrUsing go subst tv in ForAllTy (Bndr 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_mco _ MRefl = MRefl go_mco subst (MCo co) = MCo (go_co subst co) go_co subst (Refl ty) = mkNomReflCo (go subst ty) go_co subst (GRefl r ty mco) = mkGReflCo r (go subst ty) (go_mco subst mco) -- 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 afl afr w co1 co2) = mkFunCo2 r afl afr (go_co subst w) (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 (SelCo n co) = mkSelCo 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 (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 subst (PhantomProv co) = PhantomProv (go_co subst co) go_prov subst (ProofIrrelProv co) = ProofIrrelProv (go_co subst co) go_prov _ p@(PluginProv _) = p go_prov _ p@(CorePrepProv _) = 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 {- 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 GHC.Tc.Gen.Bind. -} {- ********************************************************************* * * Random functions (todo: organise) * * ********************************************************************* -} -- | An INLINE helper for function such as 'kindRep_maybe' below. -- -- @isTyConKeyApp_maybe key ty@ returns @Just tys@ iff -- the type @ty = T tys@, where T's unique = key -- key must not be `fUNTyConKey`; to test for functions, use `splitFunTy_maybe`. -- Thanks to this fact, we don't have to pattern match on `FunTy` here. isTyConKeyApp_maybe :: Unique -> Type -> Maybe [Type] isTyConKeyApp_maybe key ty | TyConApp tc args <- coreFullView ty , tc `hasKey` key = Just args | otherwise = Nothing {-# INLINE isTyConKeyApp_maybe #-} -- | Extract the RuntimeRep classifier of a type from its kind. For example, -- @kindRep * = LiftedRep@; Panics if this is not possible. -- Treats * and Constraint as the same kindRep :: HasDebugCallStack => Kind -> RuntimeRepType kindRep k = case kindRep_maybe k of Just r -> r Nothing -> pprPanic "kindRep" (ppr k) -- | Given a kind (TYPE rr) or (CONSTRAINT rr), extract its RuntimeRep classifier rr. -- For example, @kindRep_maybe * = Just LiftedRep@ -- Returns 'Nothing' if the kind is not of form (TYPE rr) kindRep_maybe :: HasDebugCallStack => Kind -> Maybe RuntimeRepType kindRep_maybe kind | Just (_, rep) <- sORTKind_maybe kind = Just rep | otherwise = Nothing -- | Returns True if the argument is (lifted) Type or Constraint -- See Note [TYPE and CONSTRAINT] in GHC.Builtin.Types.Prim isLiftedTypeKind :: Kind -> Bool isLiftedTypeKind kind = case kindRep_maybe kind of Just rep -> isLiftedRuntimeRep rep Nothing -> False -- | Returns True if the kind classifies unlifted types (like 'Int#') and False -- otherwise. Note that this returns False for representation-polymorphic -- kinds, which may be specialized to a kind that classifies unlifted types. isUnliftedTypeKind :: Kind -> Bool isUnliftedTypeKind kind = case kindRep_maybe kind of Just rep -> isUnliftedRuntimeRep rep Nothing -> False pickyIsLiftedTypeKind :: Kind -> Bool -- Checks whether the kind is literally -- TYPE LiftedRep -- or TYPE ('BoxedRep 'Lifted) -- or Type -- without expanding type synonyms or anything -- Used only when deciding whether to suppress the ":: *" in -- (a :: *) when printing kinded type variables -- See Note [Suppressing * kinds] in GHC.Core.TyCo.Ppr pickyIsLiftedTypeKind kind | TyConApp tc [arg] <- kind , tc `hasKey` tYPETyConKey , TyConApp rr_tc rr_args <- arg = case rr_args of [] -> rr_tc `hasKey` liftedRepTyConKey [rr_arg] | rr_tc `hasKey` boxedRepDataConKey , TyConApp lev [] <- rr_arg , lev `hasKey` liftedDataConKey -> True _ -> False | TyConApp tc [] <- kind , tc `hasKey` liftedTypeKindTyConKey = True | otherwise = False -- | Check whether a kind is of the form `TYPE (BoxedRep Lifted)` -- or `TYPE (BoxedRep Unlifted)`. -- -- Returns: -- -- - `Just Lifted` for `TYPE (BoxedRep Lifted)` and `Type`, -- - `Just Unlifted` for `TYPE (BoxedRep Unlifted)` and `UnliftedType`, -- - `Nothing` for anything else, e.g. `TYPE IntRep`, `TYPE (BoxedRep l)`, etc. kindBoxedRepLevity_maybe :: Type -> Maybe Levity kindBoxedRepLevity_maybe ty | Just rep <- kindRep_maybe ty , isBoxedRuntimeRep rep = runtimeRepLevity_maybe rep | otherwise = Nothing -- | Check whether a type of kind 'RuntimeRep' is lifted. -- -- 'isLiftedRuntimeRep' is: -- -- * True of @LiftedRep :: RuntimeRep@ -- * False of type variables, type family applications, -- and of other reps such as @IntRep :: RuntimeRep@. isLiftedRuntimeRep :: RuntimeRepType -> Bool isLiftedRuntimeRep rep = runtimeRepLevity_maybe rep == Just Lifted -- | Check whether a type of kind 'RuntimeRep' is unlifted. -- -- * True of definitely unlifted 'RuntimeRep's such as -- 'UnliftedRep', 'IntRep', 'FloatRep', ... -- * False of 'LiftedRep', -- * False for type variables and type family applications. isUnliftedRuntimeRep :: RuntimeRepType -> Bool isUnliftedRuntimeRep rep = runtimeRepLevity_maybe rep == Just Unlifted -- | An INLINE helper for functions such as 'isLiftedLevity' and 'isUnliftedLevity'. -- -- Checks whether the type is a nullary 'TyCon' application, -- for a 'TyCon' with the given 'Unique'. isNullaryTyConKeyApp :: Unique -> Type -> Bool isNullaryTyConKeyApp key ty | Just args <- isTyConKeyApp_maybe key ty = assert (null args) True | otherwise = False {-# INLINE isNullaryTyConKeyApp #-} isLiftedLevity :: Type -> Bool isLiftedLevity = isNullaryTyConKeyApp liftedDataConKey isUnliftedLevity :: Type -> Bool isUnliftedLevity = isNullaryTyConKeyApp unliftedDataConKey -- | Is this the type 'Levity'? isLevityTy :: Type -> Bool isLevityTy = isNullaryTyConKeyApp levityTyConKey -- | Is this the type 'RuntimeRep'? isRuntimeRepTy :: Type -> Bool isRuntimeRepTy = isNullaryTyConKeyApp runtimeRepTyConKey -- | Is a tyvar of type 'RuntimeRep'? isRuntimeRepVar :: TyVar -> Bool isRuntimeRepVar = isRuntimeRepTy . tyVarKind -- | Is a tyvar of type 'Levity'? isLevityVar :: TyVar -> Bool isLevityVar = isLevityTy . tyVarKind -- | Is this the type 'Multiplicity'? isMultiplicityTy :: Type -> Bool isMultiplicityTy = isNullaryTyConKeyApp multiplicityTyConKey -- | Is a tyvar of type 'Multiplicity'? isMultiplicityVar :: TyVar -> Bool isMultiplicityVar = isMultiplicityTy . tyVarKind -------------------------------------------- -- Splitting RuntimeRep -------------------------------------------- -- | (splitRuntimeRep_maybe rr) takes a Type rr :: RuntimeRep, and -- returns the (TyCon,[Type]) for the RuntimeRep, if possible, where -- the TyCon is one of the promoted DataCons of RuntimeRep. -- Remember: the unique on TyCon that is a a promoted DataCon is the -- same as the unique on the DataCon -- See Note [Promoted data constructors] in GHC.Core.TyCon -- May not be possible if `rr` is a type variable or type -- family application splitRuntimeRep_maybe :: RuntimeRepType -> Maybe (TyCon, [Type]) splitRuntimeRep_maybe rep | TyConApp rr_tc args <- coreFullView rep , isPromotedDataCon rr_tc -- isPromotedDataCon: be careful of type families (F tys) :: RuntimeRep, = Just (rr_tc, args) | otherwise = Nothing -- | See 'isBoxedRuntimeRep_maybe'. isBoxedRuntimeRep :: RuntimeRepType -> Bool isBoxedRuntimeRep rep = isJust (isBoxedRuntimeRep_maybe rep) -- | `isBoxedRuntimeRep_maybe (rep :: RuntimeRep)` returns `Just lev` if `rep` -- expands to `Boxed lev` and returns `Nothing` otherwise. -- -- Types with this runtime rep are represented by pointers on the GC'd heap. isBoxedRuntimeRep_maybe :: RuntimeRepType -> Maybe Type isBoxedRuntimeRep_maybe rep | Just (rr_tc, args) <- splitRuntimeRep_maybe rep , rr_tc `hasKey` boxedRepDataConKey , [lev] <- args = Just lev | otherwise = Nothing -- | Check whether a type of kind 'RuntimeRep' is lifted, unlifted, or unknown. -- -- `isLiftedRuntimeRep rr` returns: -- -- * `Just Lifted` if `rr` is `LiftedRep :: RuntimeRep` -- * `Just Unlifted` if `rr` is definitely unlifted, e.g. `IntRep` -- * `Nothing` if not known (e.g. it's a type variable or a type family application). runtimeRepLevity_maybe :: RuntimeRepType -> Maybe Levity runtimeRepLevity_maybe rep | Just (rr_tc, args) <- splitRuntimeRep_maybe rep = -- NB: args might be non-empty e.g. TupleRep [r1, .., rn] if (rr_tc `hasKey` boxedRepDataConKey) then case args of [lev] -> levityType_maybe lev _ -> pprPanic "runtimeRepLevity_maybe" (ppr rep) else Just Unlifted -- Avoid searching all the unlifted RuntimeRep type cons -- In the RuntimeRep data type, only LiftedRep is lifted | otherwise = Nothing -------------------------------------------- -- Splitting Levity -------------------------------------------- -- | `levity_maybe` takes a Type of kind Levity, and returns its levity -- May not be possible for a type variable or type family application levityType_maybe :: LevityType -> Maybe Levity levityType_maybe lev | TyConApp lev_tc args <- coreFullView lev = if | lev_tc `hasKey` liftedDataConKey -> assert( null args) $ Just Lifted | lev_tc `hasKey` unliftedDataConKey -> assert( null args) $ Just Unlifted | otherwise -> Nothing | otherwise = Nothing {- ********************************************************************* * * mapType * * ************************************************************************ 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 ForAllCo case of mapTyCoX] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ As noted in Note [Forall coercions] in GHC.Core.TyCo.Rep, a ForAllCo is a bit redundant. It stores a TyCoVar and a Coercion, where the kind of the TyCoVar 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 TyCoVar'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 INLINE pragmas are indispensable. mapTyCo and mapTyCoX are used to implement zonking, and it's vital that they get specialised to the TcM monad and the particular mapper in use. Even specialising to the monad alone made a 20% allocation difference in perf/compiler/T5030. See Note [Specialising foldType] in "GHC.Core.TyCo.Rep" for more details of this idiom. -} -- | This describes how a "map" operation over a type/coercion should behave data TyCoMapper env m = TyCoMapper { 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 "GHC.Core.TyCo.Rep". , tcm_tycobinder :: env -> TyCoVar -> ForAllTyFlag -> m (env, TyCoVar) -- ^ The returned env is used in the extended scope , tcm_tycon :: TyCon -> m TyCon -- ^ This is used only for TcTyCons -- a) To zonk TcTyCons -- b) To turn TcTyCons into TyCons. -- See Note [Type checking recursive type and class declarations] -- in "GHC.Tc.TyCl" } {-# INLINE mapTyCo #-} -- See Note [Specialising mappers] mapTyCo :: Monad m => TyCoMapper () m -> ( Type -> m Type , [Type] -> m [Type] , Coercion -> m Coercion , [Coercion] -> m[Coercion]) mapTyCo mapper = case mapTyCoX mapper of (go_ty, go_tys, go_co, go_cos) -> (go_ty (), go_tys (), go_co (), go_cos ()) {-# INLINE mapTyCoX #-} -- See Note [Specialising mappers] mapTyCoX :: Monad m => TyCoMapper env m -> ( env -> Type -> m Type , env -> [Type] -> m [Type] , env -> Coercion -> m Coercion , env -> [Coercion] -> m[Coercion]) mapTyCoX (TyCoMapper { tcm_tyvar = tyvar , tcm_tycobinder = tycobinder , tcm_tycon = tycon , tcm_covar = covar , tcm_hole = cohole }) = (go_ty, go_tys, go_co, go_cos) where go_tys _ [] = return [] go_tys env (ty:tys) = (:) <$> go_ty env ty <*> go_tys env tys go_ty env (TyVarTy tv) = tyvar env tv go_ty env (AppTy t1 t2) = mkAppTy <$> go_ty env t1 <*> go_ty env t2 go_ty _ ty@(LitTy {}) = return ty go_ty env (CastTy ty co) = mkCastTy <$> go_ty env ty <*> go_co env co go_ty env (CoercionTy co) = CoercionTy <$> go_co env co go_ty env ty@(FunTy _ w arg res) = do { w' <- go_ty env w; arg' <- go_ty env arg; res' <- go_ty env res ; return (ty { ft_mult = w', ft_arg = arg', ft_res = res' }) } go_ty env ty@(TyConApp tc tys) | isTcTyCon tc = do { tc' <- tycon tc ; mkTyConApp tc' <$> go_tys env tys } -- Not a TcTyCon | null tys -- Avoid allocation in this very = return ty -- common case (E.g. Int, LiftedRep etc) | otherwise = mkTyConApp tc <$> go_tys env tys go_ty env (ForAllTy (Bndr tv vis) inner) = do { (env', tv') <- tycobinder env tv vis ; inner' <- go_ty env' inner ; return $ ForAllTy (Bndr tv' vis) inner' } go_cos _ [] = return [] go_cos env (co:cos) = (:) <$> go_co env co <*> go_cos env cos go_mco _ MRefl = return MRefl go_mco env (MCo co) = MCo <$> (go_co env co) go_co env (Refl ty) = Refl <$> go_ty env ty go_co env (GRefl r ty mco) = mkGReflCo r <$> go_ty env ty <*> go_mco env mco go_co env (AppCo c1 c2) = mkAppCo <$> go_co env c1 <*> go_co env c2 go_co env (FunCo r afl afr cw c1 c2) = mkFunCo2 r afl afr <$> go_co env cw <*> go_co env c1 <*> go_co env c2 go_co env (CoVarCo cv) = covar env cv go_co env (HoleCo hole) = cohole env hole go_co env (UnivCo p r t1 t2) = mkUnivCo <$> go_prov env p <*> pure r <*> go_ty env t1 <*> go_ty env t2 go_co env (SymCo co) = mkSymCo <$> go_co env co go_co env (TransCo c1 c2) = mkTransCo <$> go_co env c1 <*> go_co env c2 go_co env (AxiomRuleCo r cos) = AxiomRuleCo r <$> go_cos env cos go_co env (SelCo i co) = mkSelCo i <$> go_co env co go_co env (LRCo lr co) = mkLRCo lr <$> go_co env co go_co env (InstCo co arg) = mkInstCo <$> go_co env co <*> go_co env arg go_co env (KindCo co) = mkKindCo <$> go_co env co go_co env (SubCo co) = mkSubCo <$> go_co env co go_co env (AxiomInstCo ax i cos) = mkAxiomInstCo ax i <$> go_cos env cos go_co env co@(TyConAppCo r tc cos) | isTcTyCon tc = do { tc' <- tycon tc ; mkTyConAppCo r tc' <$> go_cos env cos } -- Not a TcTyCon | null cos -- Avoid allocation in this very = return co -- common case (E.g. Int, LiftedRep etc) | otherwise = mkTyConAppCo r tc <$> go_cos env cos go_co env (ForAllCo tv kind_co co) = do { kind_co' <- go_co env kind_co ; (env', tv') <- tycobinder env tv Inferred ; co' <- go_co env' co ; return $ mkForAllCo tv' kind_co' co' } -- See Note [Efficiency for ForAllCo case of mapTyCoX] go_prov env (PhantomProv co) = PhantomProv <$> go_co env co go_prov env (ProofIrrelProv co) = ProofIrrelProv <$> go_co env co go_prov _ p@(PluginProv _) = return p go_prov _ p@(CorePrepProv _) = return p {- ********************************************************************* * * 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 :: HasDebugCallStack => Type -> TyVar getTyVar ty = case getTyVar_maybe ty of Just tv -> tv Nothing -> pprPanic "getTyVar" (ppr ty) -- | Attempts to obtain the type variable underlying a 'Type' getTyVar_maybe :: Type -> Maybe TyVar getTyVar_maybe = repGetTyVar_maybe . coreFullView -- | 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 isTyVarTy :: Type -> Bool isTyVarTy ty = isJust (getTyVar_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 ty getCastedTyVar_maybe :: Type -> Maybe (TyVar, CoercionN) getCastedTyVar_maybe ty = case coreFullView ty of CastTy (TyVarTy tv) co -> Just (tv, co) TyVarTy tv -> Just (tv, mkReflCo Nominal (tyVarKind tv)) _ -> 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 (#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 splitAppTyNoView_maybe, which applies throughout, because the other calls to splitAppTy are in GHC.Core.Unify, which is also used by the type checker (e.g. when matching type-function equations). We are willing to split (t1 -=> t2) because the argument is still of kind Type, not Constraint. So the criterion is isVisibleFunArg. -} -- | 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 -- -- Moreover in GHC.Tc.Types.tcInferTyApps we build up a type -- (T t1 t2 t3) one argument at a type, thus forming -- (T t1), (T t1 t2), etc 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 GHC.Core.TyCo.Rep = 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 = splitAppTyNoView_maybe . coreFullView splitAppTy :: Type -> (Type, Type) -- ^ Attempts to take a type application apart, as in 'splitAppTy_maybe', -- and panics if this is not possible splitAppTy ty = splitAppTy_maybe ty `orElse` pprPanic "splitAppTy" (ppr ty) ------------- splitAppTyNoView_maybe :: HasDebugCallStack => Type -> Maybe (Type,Type) -- ^ Does the AppTy split as in 'splitAppTy_maybe', but assumes that -- any coreView stuff is already done splitAppTyNoView_maybe (AppTy ty1 ty2) = Just (ty1, ty2) splitAppTyNoView_maybe (FunTy af w ty1 ty2) | Just (tc, tys) <- funTyConAppTy_maybe af w ty1 ty2 , Just (tys', ty') <- snocView tys = Just (TyConApp tc tys', ty') splitAppTyNoView_maybe (TyConApp tc tys) | not (tyConMustBeSaturated tc) || tys `lengthExceeds` tyConArity tc , Just (tys', ty') <- snocView tys = Just (TyConApp tc tys', ty') -- Never create unsaturated type family apps! splitAppTyNoView_maybe _other = Nothing tcSplitAppTyNoView_maybe :: Type -> Maybe (Type,Type) -- ^ Just like splitAppTyNoView_maybe, but does not split (c => t) -- See Note [Decomposing fat arrow c=>t] tcSplitAppTyNoView_maybe ty | FunTy { ft_af = af } <- ty , not (isVisibleFunArg af) -- See Note [Decomposing fat arrow c=>t] = Nothing | otherwise = splitAppTyNoView_maybe ty ------------- 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 | tyConMustBeSaturated tc = tyConArity tc | otherwise = 0 (tc_args1, tc_args2) = splitAt n tc_args in (TyConApp tc tc_args1, tc_args2 ++ args) split _ (FunTy af w ty1 ty2) args | Just (tc,tys) <- funTyConAppTy_maybe af w ty1 ty2 = assert (null args ) (TyConApp tc [], tys) split orig_ty _ args = (orig_ty, args) -- | Like 'splitAppTys', but doesn't look through type synonyms splitAppTysNoView :: HasDebugCallStack => Type -> (Type, [Type]) splitAppTysNoView ty = split ty [] where split (AppTy ty arg) args = split ty (arg:args) split (TyConApp tc tc_args) args = let n | tyConMustBeSaturated tc = tyConArity tc | otherwise = 0 (tc_args1, tc_args2) = splitAt n tc_args in (TyConApp tc tc_args1, tc_args2 ++ args) split (FunTy af w ty1 ty2) args | Just (tc, tys) <- funTyConAppTy_maybe af w ty1 ty2 = assert (null args ) (TyConApp tc [], tys) 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 | LitTy (NumTyLit n) <- coreFullView ty = Just n | otherwise = 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 | LitTy (StrTyLit s) <- coreFullView ty = Just s | otherwise = Nothing mkCharLitTy :: Char -> Type mkCharLitTy c = LitTy (CharTyLit c) -- | Is this a char literal? We also look through type synonyms. isCharLitTy :: Type -> Maybe Char isCharLitTy ty | LitTy (CharTyLit s) <- coreFullView ty = Just s | otherwise = Nothing -- | Is this a type literal (symbol, numeric, or char)? isLitTy :: Type -> Maybe TyLit isLitTy ty | LitTy l <- coreFullView ty = Just l | otherwise = 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) can be thought of as being applications of funTyCon (known in Haskell surface syntax as (->)), (note that `RuntimeRep' quantifiers are left inferred) (->) :: 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 reconstructing 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. -} ----------------------------------------------- funTyConAppTy_maybe :: FunTyFlag -> Type -> Type -> Type -> Maybe (TyCon, [Type]) -- ^ Given the components of a FunTy -- figure out the corresponding TyConApp. funTyConAppTy_maybe af mult arg res | Just arg_rep <- getRuntimeRep_maybe arg , Just res_rep <- getRuntimeRep_maybe res , let args | isFUNArg af = [mult, arg_rep, res_rep, arg, res] | otherwise = [ arg_rep, res_rep, arg, res] = Just $ (funTyFlagTyCon af, args) | otherwise = Nothing tyConAppFunTy_maybe :: HasDebugCallStack => TyCon -> [Type] -> Maybe Type -- ^ Return Just if this TyConApp should be represented as a FunTy tyConAppFunTy_maybe tc tys | Just (af, mult, arg, res) <- ty_con_app_fun_maybe manyDataConTy tc tys = Just (FunTy { ft_af = af, ft_mult = mult, ft_arg = arg, ft_res = res }) | otherwise = Nothing tyConAppFunCo_maybe :: HasDebugCallStack => Role -> TyCon -> [Coercion] -> Maybe Coercion -- ^ Return Just if this TyConAppCo should be represented as a FunCo tyConAppFunCo_maybe r tc cos | Just (af, mult, arg, res) <- ty_con_app_fun_maybe (mkReflCo r manyDataConTy) tc cos = Just (mkFunCo1 r af mult arg res) | otherwise = Nothing ty_con_app_fun_maybe :: (HasDebugCallStack, Outputable a) => a -> TyCon -> [a] -> Maybe (FunTyFlag, a, a, a) {-# INLINE ty_con_app_fun_maybe #-} -- Specialise this function for its two call sites ty_con_app_fun_maybe many_ty_co tc args | tc_uniq == fUNTyConKey = fUN_case | tc_uniq == tcArrowTyConKey = non_FUN_case FTF_T_C | tc_uniq == ctArrowTyConKey = non_FUN_case FTF_C_T | tc_uniq == ccArrowTyConKey = non_FUN_case FTF_C_C | otherwise = Nothing where tc_uniq = tyConUnique tc fUN_case | (w:_r1:_r2:a1:a2:rest) <- args = assertPpr (null rest) (ppr tc <+> ppr args) $ Just (FTF_T_T, w, a1, a2) | otherwise = Nothing non_FUN_case ftf | (_r1:_r2:a1:a2:rest) <- args = assertPpr (null rest) (ppr tc <+> ppr args) $ Just (ftf, many_ty_co, a1, a2) | otherwise = Nothing mkFunctionType :: Mult -> Type -> Type -> Type -- ^ This one works out the FunTyFlag from the argument type -- See GHC.Types.Var Note [FunTyFlag] mkFunctionType mult arg_ty res_ty = FunTy { ft_af = af, ft_arg = arg_ty, ft_res = res_ty , ft_mult = assertPpr mult_ok (ppr [mult, arg_ty, res_ty]) $ mult } where af = chooseFunTyFlag arg_ty res_ty mult_ok = isVisibleFunArg af || isManyTy mult mkScaledFunctionTys :: [Scaled Type] -> Type -> Type -- ^ Like mkFunctionType, compute the FunTyFlag from the arguments mkScaledFunctionTys arg_tys res_ty = foldr mk res_ty arg_tys where mk (Scaled mult arg_ty) res_ty = mkFunTy (chooseFunTyFlag arg_ty res_ty) mult arg_ty res_ty chooseFunTyFlag :: HasDebugCallStack => Type -> Type -> FunTyFlag -- ^ See GHC.Types.Var Note [FunTyFlag] chooseFunTyFlag arg_ty res_ty = mkFunTyFlag (typeTypeOrConstraint arg_ty) (typeTypeOrConstraint res_ty) splitFunTy :: Type -> (Mult, Type, Type) -- ^ Attempts to extract the multiplicity, argument and result types from a type, -- and panics if that is not possible. See also 'splitFunTy_maybe' splitFunTy ty = case splitFunTy_maybe ty of Just (_af, mult, arg, res) -> (mult,arg,res) Nothing -> pprPanic "splitFunTy" (ppr ty) {-# INLINE splitFunTy_maybe #-} splitFunTy_maybe :: Type -> Maybe (FunTyFlag, Mult, Type, Type) -- ^ Attempts to extract the multiplicity, argument and result types from a type splitFunTy_maybe ty | FunTy af w arg res <- coreFullView ty = Just (af, w, arg, res) | otherwise = Nothing splitFunTys :: Type -> ([Scaled Type], Type) splitFunTys ty = split [] ty ty where -- common case first split args _ (FunTy _ w arg res) = split (Scaled w arg : args) res res split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty' split args orig_ty _ = (reverse args, orig_ty) funResultTy :: HasDebugCallStack => Type -> Type -- ^ Extract the function result type and panic if that is not possible funResultTy ty | FunTy { ft_res = res } <- coreFullView ty = res | otherwise = pprPanic "funResultTy" (ppr ty) funArgTy :: Type -> Type -- ^ Extract the function argument type and panic if that is not possible funArgTy ty | FunTy { ft_arg = arg } <- coreFullView ty = arg | otherwise = pprPanic "funArgTy" (ppr ty) -- ^ 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 :: HasDebugCallStack => Type -> Type -> Type piResultTy ty arg = case piResultTy_maybe ty arg of Just res -> res Nothing -> pprPanic "piResultTy" (ppr ty $$ ppr arg) piResultTy_maybe :: Type -> Type -> Maybe Type -- We don't need a 'tc' version, because -- this function behaves the same for Type and Constraint piResultTy_maybe ty arg = case coreFullView ty of FunTy { ft_res = res } -> Just res ForAllTy (Bndr tv _) res -> let empty_subst = mkEmptySubst $ mkInScopeSet $ tyCoVarsOfTypes [arg,res] in Just (substTy (extendTCvSubst empty_subst tv arg) res) _ -> Nothing -- | (piResultTys f_ty [ty1, .., tyn]) gives the type of (f ty1 .. tyn) -- where f :: f_ty -- 'piResultTys' is interesting because: -- 1. 'f_ty' may have more for-alls than there are args -- 2. Less obviously, it may have fewer for-alls -- For case 2. think of: -- piResultTys (forall a.a) [forall b.b, Int] -- This really can happen, but only (I think) in situations involving -- undefined. For example: -- undefined :: forall a. a -- Term: undefined @(forall b. b->b) @Int -- This term should have type (Int -> Int), but notice that -- there are more type args than foralls in 'undefined's type. -- If you edit this function, you may need to update the GHC formalism -- See Note [GHC Formalism] in GHC.Core.Lint -- This is a heavily used function (e.g. from typeKind), -- so we pay attention to efficiency, especially in the special case -- where there are no for-alls so we are just dropping arrows from -- a function type/kind. piResultTys :: HasDebugCallStack => Type -> [Type] -> Type piResultTys ty [] = ty piResultTys ty orig_args@(arg:args) | FunTy { ft_res = res } <- ty = piResultTys res args | ForAllTy (Bndr tv _) res <- ty = go (extendTCvSubst init_subst tv arg) res args | Just ty' <- coreView ty = piResultTys ty' orig_args | otherwise = pprPanic "piResultTys1" (ppr ty $$ ppr orig_args) where init_subst = mkEmptySubst $ mkInScopeSet (tyCoVarsOfTypes (ty:orig_args)) go :: Subst -> Type -> [Type] -> Type go subst ty [] = substTyUnchecked subst ty go subst ty all_args@(arg:args) | FunTy { ft_res = res } <- ty = go subst res args | ForAllTy (Bndr tv _) res <- ty = go (extendTCvSubst subst tv arg) res args | Just ty' <- coreView ty = go subst ty' all_args | not (isEmptyTCvSubst subst) -- See Note [Care with kind instantiation] = go init_subst (substTy subst 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 the explicit isEmptyVarEnv test, an ill-kinded type -- would give an infinite loop, which is very unhelpful -- c.f. #15473 pprPanic "piResultTys2" (ppr ty $$ ppr orig_args $$ ppr all_args) applyTysX :: [TyVar] -> Type -> [Type] -> Type -- applyTysX beta-reduces (/\tvs. body_ty) arg_tys -- Assumes that (/\tvs. body_ty) is closed applyTysX tvs body_ty arg_tys = assertPpr (tvs `leLength` arg_tys) pp_stuff $ assertPpr (tyCoVarsOfType body_ty `subVarSet` mkVarSet tvs) pp_stuff $ mkAppTys (substTyWith tvs arg_tys_prefix body_ty) arg_tys_rest where pp_stuff = vcat [ppr tvs, ppr body_ty, ppr arg_tys] (arg_tys_prefix, arg_tys_rest) = splitAtList tvs arg_tys {- 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 we must instantiate the forall! Similarly (#15428) 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 GHC.CoreToIface.toIfaceAppArgsX. -} {- ********************************************************************* * * TyConApp * * ********************************************************************* -} -- 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 { ft_af = af }) = Just (funTyFlagTyCon af) tyConAppTyConPicky_maybe _ = Nothing -- | The same as @fst . splitTyConApp@ -- We can short-cut the FunTy case {-# INLINE tyConAppTyCon_maybe #-} tyConAppTyCon_maybe :: Type -> Maybe TyCon tyConAppTyCon_maybe ty = case coreFullView ty of TyConApp tc _ -> Just tc FunTy { ft_af = af } -> Just (funTyFlagTyCon af) _ -> Nothing tyConAppTyCon :: HasDebugCallStack => 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 = case splitTyConApp_maybe ty of Just (_, tys) -> Just tys Nothing -> Nothing tyConAppArgs :: HasCallStack => Type -> [Type] tyConAppArgs ty = tyConAppArgs_maybe ty `orElse` pprPanic "tyConAppArgs" (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 = splitTyConApp_maybe ty `orElse` 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 = splitTyConAppNoView_maybe (coreFullView ty) splitTyConAppNoView_maybe :: Type -> Maybe (TyCon, [Type]) -- Same as splitTyConApp_maybe but without looking through synonyms splitTyConAppNoView_maybe ty = case ty of FunTy { ft_af = af, ft_mult = w, ft_arg = arg, ft_res = res} -> funTyConAppTy_maybe af w arg res TyConApp tc tys -> Just (tc, tys) _ -> Nothing -- | tcSplitTyConApp_maybe splits a type constructor application into -- its type constructor and applied types. -- -- Differs from splitTyConApp_maybe in that it does *not* split types -- headed with (=>), as that's not a TyCon in the type-checker. -- -- Note that this may fail (in funTyConAppTy_maybe) 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`. This isn't usually a problem but may -- be temporarily the cas during canonicalization: -- see Note [Decomposing FunTy] in GHC.Tc.Solver.Canonical -- and Note [The Purely Kinded Type Invariant (PKTI)] in GHC.Tc.Gen.HsType, -- Wrinkle around FunTy -- -- Consequently, you may need to zonk your type before -- using this function. tcSplitTyConApp_maybe :: HasCallStack => Type -> Maybe (TyCon, [Type]) -- Defined here to avoid module loops between Unify and TcType. tcSplitTyConApp_maybe ty = case coreFullView ty of FunTy { ft_af = af, ft_mult = w, ft_arg = arg, ft_res = res} | isVisibleFunArg af -- Visible args only -- See Note [Decomposing fat arrow c=>t] -> funTyConAppTy_maybe af w arg res TyConApp tc tys -> Just (tc, tys) _ -> Nothing tcSplitTyConApp :: Type -> (TyCon, [Type]) tcSplitTyConApp ty = tcSplitTyConApp_maybe ty `orElse` pprPanic "tcSplitTyConApp" (ppr ty) --------------------------- 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 = assertPpr (tvs `leLength` tys) (ppr tycon $$ ppr tys $$ ppr tvs) $ applyTysX tvs rhs tys where (tvs, rhs) = newTyConEtadRhs tycon {- ********************************************************************* * * CastTy * * ********************************************************************* -} splitCastTy_maybe :: Type -> Maybe (Type, Coercion) splitCastTy_maybe ty | CastTy ty' co <- coreFullView ty = Just (ty', co) | otherwise = 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 "GHC.Core.TyCo.Rep" mkCastTy :: Type -> Coercion -> Type mkCastTy orig_ty co | isReflexiveCo co = orig_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 orig_ty co = mk_cast_ty orig_ty co -- | Like 'mkCastTy', but avoids checking the coercion for reflexivity, -- as that can be expensive. mk_cast_ty :: Type -> Coercion -> Type mk_cast_ty orig_ty co = go orig_ty where go :: Type -> Type -- See Note [Using coreView in mk_cast_ty] go ty | Just ty' <- coreView ty = go ty' go (CastTy ty co1) -- (EQ3) from the Note = mkCastTy ty (co1 `mkTransCo` co) -- call mkCastTy again for the reflexivity check go (ForAllTy (Bndr tv vis) inner_ty) -- (EQ4) from the Note -- See Note [Weird typing rule for ForAllTy] in GHC.Core.TyCo.Rep. | isTyVar tv , let fvs = tyCoVarsOfCo co = -- have to make sure that pushing the co in doesn't capture the bound var! if tv `elemVarSet` fvs then let empty_subst = mkEmptySubst (mkInScopeSet fvs) (subst, tv') = substVarBndr empty_subst tv in ForAllTy (Bndr tv' vis) (substTy subst inner_ty `mk_cast_ty` co) else ForAllTy (Bndr tv vis) (inner_ty `mk_cast_ty` co) go _ = CastTy orig_ty co -- NB: orig_ty: preserve synonyms if possible {- Note [Using coreView in mk_cast_ty] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Invariants (EQ3) and (EQ4) of Note [Respecting definitional equality] in GHC.Core.TyCo.Rep must apply regardless of type synonyms. For instance, consider this example (#19742): type EqSameNat = () |> co useNatEq :: EqSameNat |> sym co (Those casts aren't visible in the user-source code, of course; see #19742 for what the user might write.) The type `EqSameNat |> sym co` looks as if it satisfies (EQ3), as it has no nested casts, but if we expand EqSameNat, we see that it doesn't. And then Bad Things happen. The solution is easy: just use `coreView` when establishing (EQ3) and (EQ4) in `mk_cast_ty`. -} {- ********************************************************************* * * 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) {- ********************************************************************* * * ForAllTy * * ********************************************************************* -} tyConBindersPiTyBinders :: [TyConBinder] -> [PiTyBinder] -- Return the tyConBinders in PiTyBinder form tyConBindersPiTyBinders = map to_tyb where to_tyb (Bndr tv (NamedTCB vis)) = Named (Bndr tv vis) to_tyb (Bndr tv (AnonTCB af)) = Anon (tymult (varType tv)) af -- | Make a dependent forall over an 'Inferred' variable mkTyCoInvForAllTy :: TyCoVar -> Type -> Type mkTyCoInvForAllTy tv ty | isCoVar tv , not (tv `elemVarSet` tyCoVarsOfType ty) = mkVisFunTyMany (varType tv) ty | otherwise = ForAllTy (Bndr tv Inferred) ty -- | Like 'mkTyCoInvForAllTy', but tv should be a tyvar mkInfForAllTy :: TyVar -> Type -> Type mkInfForAllTy tv ty = assert (isTyVar tv ) ForAllTy (Bndr tv Inferred) ty -- | Like 'mkForAllTys', but assumes all variables are dependent and -- 'Inferred', a common case mkTyCoInvForAllTys :: [TyCoVar] -> Type -> Type mkTyCoInvForAllTys tvs ty = foldr mkTyCoInvForAllTy ty tvs -- | Like 'mkTyCoInvForAllTys', but tvs should be a list of tyvar mkInfForAllTys :: [TyVar] -> Type -> Type mkInfForAllTys tvs ty = foldr mkInfForAllTy ty tvs -- | Like 'mkForAllTy', but assumes the variable is dependent and 'Specified', -- a common case mkSpecForAllTy :: TyVar -> Type -> Type mkSpecForAllTy tv ty = assert (isTyVar tv ) -- covar is always Inferred, so input should be tyvar ForAllTy (Bndr tv Specified) ty -- | Like 'mkForAllTys', but assumes all variables are dependent and -- 'Specified', a common case mkSpecForAllTys :: [TyVar] -> Type -> Type mkSpecForAllTys tvs ty = foldr mkSpecForAllTy ty tvs -- | Like mkForAllTys, but assumes all variables are dependent and visible mkVisForAllTys :: [TyVar] -> Type -> Type mkVisForAllTys tvs = assert (all isTyVar tvs ) -- covar is always Inferred, so all inputs should be tyvar mkForAllTys [ Bndr tv Required | tv <- tvs ] -- | Given a list of type-level vars and the free vars of a result kind, -- makes PiTyBinders, 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, (b:k) Anon, (c:k) Anon -- -- All non-coercion binders are /visible/. mkTyConBindersPreferAnon :: [TyVar] -- ^ binders -> TyCoVarSet -- ^ free variables of result -> [TyConBinder] mkTyConBindersPreferAnon vars inner_tkvs = assert (all isTyVar vars) fst (go vars) where go :: [TyVar] -> ([TyConBinder], VarSet) -- also returns the free vars go [] = ([], inner_tkvs) go (v:vs) | v `elemVarSet` fvs = ( Bndr v (NamedTCB Required) : binders , fvs `delVarSet` v `unionVarSet` kind_vars ) | otherwise = ( Bndr v (AnonTCB visArgTypeLike) : binders , fvs `unionVarSet` kind_vars ) where (binders, fvs) = go vs kind_vars = tyCoVarsOfType $ tyVarKind v -- | Take a ForAllTy apart, returning the binders and result type splitForAllForAllTyBinders :: Type -> ([ForAllTyBinder], Type) splitForAllForAllTyBinders ty = split ty ty [] where split _ (ForAllTy b res) bs = split res res (b:bs) split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs split orig_ty _ bs = (reverse bs, orig_ty) {-# INLINE splitForAllForAllTyBinders #-} -- | Take a ForAllTy apart, returning the list of tycovars 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. splitForAllTyCoVars :: Type -> ([TyCoVar], Type) splitForAllTyCoVars ty = split ty ty [] where split _ (ForAllTy (Bndr tv _) ty) tvs = split ty ty (tv:tvs) split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs split orig_ty _ tvs = (reverse tvs, orig_ty) -- | Like 'splitForAllTyCoVars', but split only for tyvars. -- 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. splitForAllTyVars :: Type -> ([TyVar], Type) splitForAllTyVars ty = split ty ty [] where split _ (ForAllTy (Bndr tv _) ty) tvs | isTyVar tv = split ty ty (tv:tvs) split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs split orig_ty _ tvs = (reverse tvs, orig_ty) -- | Like 'splitForAllTyCoVars', but only splits 'ForAllTy's with 'Required' type -- variable binders. Furthermore, each returned tyvar is annotated with '()'. splitForAllReqTyBinders :: Type -> ([ReqTyBinder], Type) splitForAllReqTyBinders ty = split ty ty [] where split _ (ForAllTy (Bndr tv Required) ty) tvs = split ty ty (Bndr tv ():tvs) split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs split orig_ty _ tvs = (reverse tvs, orig_ty) -- | Like 'splitForAllTyCoVars', but only splits 'ForAllTy's with 'Invisible' type -- variable binders. Furthermore, each returned tyvar is annotated with its -- 'Specificity'. splitForAllInvisTyBinders :: Type -> ([InvisTyBinder], Type) splitForAllInvisTyBinders ty = split ty ty [] where split _ (ForAllTy (Bndr tv (Invisible spec)) ty) tvs = split ty ty (Bndr tv spec:tvs) split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs split orig_ty _ tvs = (reverse tvs, orig_ty) -- | Checks whether this is a proper forall (with a named binder) isForAllTy :: Type -> Bool isForAllTy ty | ForAllTy {} <- coreFullView ty = True | otherwise = False -- | Like `isForAllTy`, but returns True only if it is a tyvar binder isForAllTy_ty :: Type -> Bool isForAllTy_ty ty | ForAllTy (Bndr tv _) _ <- coreFullView ty , isTyVar tv = True | otherwise = False -- | Like `isForAllTy`, but returns True only if it is a covar binder isForAllTy_co :: Type -> Bool isForAllTy_co ty | ForAllTy (Bndr tv _) _ <- coreFullView ty , isCoVar tv = True | otherwise = False -- | Is this a function or forall? isPiTy :: Type -> Bool isPiTy ty = case coreFullView ty of ForAllTy {} -> True FunTy {} -> True _ -> False -- | Is this a function? isFunTy :: Type -> Bool isFunTy ty | FunTy {} <- coreFullView ty = True | otherwise = False -- | Take a forall type apart, or panics if that is not possible. splitForAllTyCoVar :: Type -> (TyCoVar, Type) splitForAllTyCoVar ty | Just answer <- splitForAllTyCoVar_maybe ty = answer | otherwise = pprPanic "splitForAllTyCoVar" (ppr ty) -- | Drops all ForAllTys dropForAlls :: Type -> Type dropForAlls ty = go ty where go (ForAllTy _ res) = go res go ty | Just ty' <- coreView ty = go ty' go res = res -- | Attempts to take a forall type apart, but only if it's a proper forall, -- with a named binder splitForAllTyCoVar_maybe :: Type -> Maybe (TyCoVar, Type) splitForAllTyCoVar_maybe ty | ForAllTy (Bndr tv _) inner_ty <- coreFullView ty = Just (tv, inner_ty) | otherwise = Nothing -- | Like 'splitForAllTyCoVar_maybe', but only returns Just if it is a tyvar binder. splitForAllTyVar_maybe :: Type -> Maybe (TyVar, Type) splitForAllTyVar_maybe ty | ForAllTy (Bndr tv _) inner_ty <- coreFullView ty , isTyVar tv = Just (tv, inner_ty) | otherwise = Nothing -- | Like 'splitForAllTyCoVar_maybe', but only returns Just if it is a covar binder. splitForAllCoVar_maybe :: Type -> Maybe (CoVar, Type) splitForAllCoVar_maybe ty | ForAllTy (Bndr tv _) inner_ty <- coreFullView ty , isCoVar tv = Just (tv, inner_ty) | otherwise = Nothing -- | Attempts to take a forall type apart; works with proper foralls and -- functions {-# INLINE splitPiTy_maybe #-} -- callers will immediately deconstruct splitPiTy_maybe :: Type -> Maybe (PiTyBinder, Type) splitPiTy_maybe ty = case coreFullView ty of ForAllTy bndr ty -> Just (Named bndr, ty) FunTy { ft_af = af, ft_mult = w, ft_arg = arg, ft_res = res} -> Just (Anon (mkScaled w arg) af, res) _ -> Nothing -- | Takes a forall type apart, or panics splitPiTy :: Type -> (PiTyBinder, Type) splitPiTy ty | Just answer <- splitPiTy_maybe ty = answer | otherwise = pprPanic "splitPiTy" (ppr ty) -- | Split off all PiTyBinders to a type, splitting both proper foralls -- and functions splitPiTys :: Type -> ([PiTyBinder], Type) splitPiTys ty = split ty ty [] where split _ (ForAllTy b res) bs = split res res (Named b : bs) split _ (FunTy { ft_af = af, ft_mult = w, ft_arg = arg, ft_res = res }) bs = split res res (Anon (Scaled w arg) af : bs) split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs split orig_ty _ bs = (reverse bs, orig_ty) -- | Extracts a list of run-time arguments from a function type, -- looking through newtypes to the right of arrows. -- -- Examples: -- -- @ -- newtype Identity a = I a -- -- getRuntimeArgTys (Int -> Bool -> Double) == [(Int, FTF_T_T), (Bool, FTF_T_T)] -- getRuntimeArgTys (Identity Int -> Bool -> Double) == [(Identity Int, FTF_T_T), (Bool, FTF_T_T)] -- getRuntimeArgTys (Int -> Identity (Bool -> Identity Double)) == [(Int, FTF_T_T), (Bool, FTF_T_T)] -- getRuntimeArgTys (forall a. Show a => Identity a -> a -> Int -> Bool) -- == [(Show a, FTF_C_T), (Identity a, FTF_T_T),(a, FTF_T_T),(Int, FTF_T_T)] -- @ -- -- Note that, in the last case, the returned types might mention an out-of-scope -- type variable. This function is used only when we really care about the /kinds/ -- of the returned types, so this is OK. -- -- **Warning**: this function can return an infinite list. For example: -- -- @ -- newtype N a = MkN (a -> N a) -- getRuntimeArgTys (N a) == repeat (a, FTF_T_T) -- @ getRuntimeArgTys :: Type -> [(Scaled Type, FunTyFlag)] getRuntimeArgTys = go where go :: Type -> [(Scaled Type, FunTyFlag)] go (ForAllTy _ res) = go res go (FunTy { ft_mult = w, ft_arg = arg, ft_res = res, ft_af = af }) = (Scaled w arg, af) : go res go ty | Just ty' <- coreView ty = go ty' | Just (_,ty') <- topNormaliseNewType_maybe ty = go ty' | otherwise = [] invisibleTyBndrCount :: Type -> Int -- Returns the number of leading invisible forall'd binders in the type -- Includes invisible predicate arguments; e.g. for -- e.g. forall {k}. (k ~ *) => k -> k -- returns 2 not 1 invisibleTyBndrCount ty = length (fst (splitInvisPiTys ty)) -- | Like 'splitPiTys', but returns only *invisible* binders, including constraints. -- Stops at the first visible binder. splitInvisPiTys :: Type -> ([PiTyBinder], Type) splitInvisPiTys ty = split ty ty [] where split _ (ForAllTy b res) bs | Bndr _ vis <- b , isInvisibleForAllTyFlag vis = split res res (Named b : bs) split _ (FunTy { ft_af = af, ft_mult = mult, ft_arg = arg, ft_res = res }) bs | isInvisibleFunArg af = split res res (Anon (mkScaled mult arg) af : bs) split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs split orig_ty _ bs = (reverse bs, orig_ty) splitInvisPiTysN :: Int -> Type -> ([PiTyBinder], Type) -- ^ Same as 'splitInvisPiTys', but stop when -- - you have found @n@ 'PiTyBinder's, -- - or you run out of invisible binders splitInvisPiTysN n ty = split n ty ty [] where split n orig_ty ty bs | n == 0 = (reverse bs, orig_ty) | Just ty' <- coreView ty = split n orig_ty ty' bs | ForAllTy b res <- ty , Bndr _ vis <- b , isInvisibleForAllTyFlag vis = split (n-1) res res (Named b : bs) | FunTy { ft_af = af, ft_mult = mult, ft_arg = arg, ft_res = res } <- ty , isInvisibleFunArg af = split (n-1) res res (Anon (Scaled mult arg) af : bs) | otherwise = (reverse bs, orig_ty) -- | Given a 'TyCon' and a list of argument types, filter out any invisible -- (i.e., 'Inferred' or 'Specified') arguments. filterOutInvisibleTypes :: TyCon -> [Type] -> [Type] filterOutInvisibleTypes tc tys = snd $ partitionInvisibleTypes tc tys -- | Given a 'TyCon' and a list of argument types, filter out any 'Inferred' -- arguments. filterOutInferredTypes :: TyCon -> [Type] -> [Type] filterOutInferredTypes tc tys = filterByList (map (/= Inferred) $ tyConForAllTyFlags tc tys) tys -- | Given a 'TyCon' and a list of argument types, partition the arguments -- into: -- -- 1. 'Inferred' or 'Specified' (i.e., invisible) arguments and -- -- 2. 'Required' (i.e., visible) arguments partitionInvisibleTypes :: TyCon -> [Type] -> ([Type], [Type]) partitionInvisibleTypes tc tys = partitionByList (map isInvisibleForAllTyFlag $ tyConForAllTyFlags tc tys) tys -- | Given a list of things paired with their visibilities, partition the -- things into (invisible things, visible things). partitionInvisibles :: [(a, ForAllTyFlag)] -> ([a], [a]) partitionInvisibles = partitionWith pick_invis where pick_invis :: (a, ForAllTyFlag) -> Either a a pick_invis (thing, vis) | isInvisibleForAllTyFlag vis = Left thing | otherwise = Right thing -- | Given a 'TyCon' and a list of argument types to which the 'TyCon' is -- applied, determine each argument's visibility -- ('Inferred', 'Specified', or 'Required'). -- -- Wrinkle: consider the following scenario: -- -- > T :: forall k. k -> k -- > tyConForAllTyFlags 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. tyConForAllTyFlags :: TyCon -> [Type] -> [ForAllTyFlag] tyConForAllTyFlags tc = fun_kind_arg_flags (tyConKind tc) -- | Given a 'Type' and a list of argument types to which the 'Type' is -- applied, determine each argument's visibility -- ('Inferred', 'Specified', or 'Required'). -- -- Most of the time, the arguments will be 'Required', but not always. Consider -- @f :: forall a. a -> Type@. In @f Type Bool@, the first argument (@Type@) is -- 'Specified' and the second argument (@Bool@) is 'Required'. It is precisely -- this sort of higher-rank situation in which 'appTyForAllTyFlags' comes in handy, -- since @f Type Bool@ would be represented in Core using 'AppTy's. -- (See also #15792). appTyForAllTyFlags :: Type -> [Type] -> [ForAllTyFlag] appTyForAllTyFlags ty = fun_kind_arg_flags (typeKind ty) -- | Given a function kind and a list of argument types (where each argument's -- kind aligns with the corresponding position in the argument kind), determine -- each argument's visibility ('Inferred', 'Specified', or 'Required'). fun_kind_arg_flags :: Kind -> [Type] -> [ForAllTyFlag] fun_kind_arg_flags = go emptySubst where go subst ki arg_tys | Just ki' <- coreView ki = go subst ki' arg_tys go _ _ [] = [] go subst (ForAllTy (Bndr tv argf) res_ki) (arg_ty:arg_tys) = argf : go subst' res_ki arg_tys where subst' = extendTvSubst subst tv arg_ty go subst (TyVarTy tv) arg_tys | Just ki <- lookupTyVar subst tv = go subst ki arg_tys -- This FunTy case is important to handle kinds with nested foralls, such -- as this kind (inspired by #16518): -- -- forall {k1} k2. k1 -> k2 -> forall k3. k3 -> Type -- -- Here, we want to get the following ForAllTyFlags: -- -- [Inferred, Specified, Required, Required, Specified, Required] -- forall {k1}. forall k2. k1 -> k2 -> forall k3. k3 -> Type go subst (FunTy{ft_af = af, ft_res = res_ki}) (_:arg_tys) = argf : go subst res_ki arg_tys where argf | isVisibleFunArg af = Required | otherwise = Inferred go _ _ arg_tys = map (const Required) arg_tys -- something is ill-kinded. But this can happen -- when printing errors. Assume everything is Required. -- @isTauTy@ tests if a type has no foralls or (=>) 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 { ft_af = af, ft_mult = w, ft_arg = a, ft_res = b }) | isInvisibleFunArg af = False -- e.g., Eq a => b | otherwise = isTauTy w && isTauTy a && isTauTy b -- e.g., a -> b isTauTy (ForAllTy {}) = False isTauTy (CastTy ty _) = isTauTy ty isTauTy (CoercionTy _) = False -- Not sure about this isAtomicTy :: Type -> Bool -- True if the type is just a single token, and can be printed compactly -- Used when deciding how to lay out type error messages; see the -- call in GHC.Tc.Errors isAtomicTy (TyVarTy {}) = True isAtomicTy (LitTy {}) = True isAtomicTy (TyConApp _ []) = True isAtomicTy ty | isLiftedTypeKind ty = True -- 'Type' prints compactly as * -- See GHC.Iface.Type.ppr_kind_type isAtomicTy _ = False {- ************************************************************************ * * \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 = assertPpr (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)) 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 _ w a b) = isFamFreeTy w && isFamFreeTy a && isFamFreeTy b isFamFreeTy (ForAllTy _ ty) = isFamFreeTy ty isFamFreeTy (CastTy ty _) = isFamFreeTy ty isFamFreeTy (CoercionTy _) = False -- Not sure about this -- | Does this type classify a core (unlifted) Coercion? -- At either role nominal or representational -- (t1 ~# t2) or (t1 ~R# t2) -- See Note [Types for coercions, predicates, and evidence] in "GHC.Core.TyCo.Rep" isCoVarType :: Type -> Bool -- ToDo: should we check saturation? isCoVarType ty | Just tc <- tyConAppTyCon_maybe ty = tc `hasKey` eqPrimTyConKey || tc `hasKey` eqReprPrimTyConKey | otherwise = False buildSynTyCon :: Name -> [KnotTied TyConBinder] -> Kind -- ^ /result/ kind -> [Role] -> KnotTied Type -> TyCon -- This function is here because here is where we have -- isFamFree and isTauTy buildSynTyCon name binders res_kind roles rhs = mkSynonymTyCon name binders res_kind roles rhs is_tau is_fam_free is_forgetful where is_tau = isTauTy rhs is_fam_free = isFamFreeTy rhs is_forgetful = any (not . (`elemVarSet` tyCoVarsOfType rhs) . binderVar) binders || uniqSetAny isForgetfulSynTyCon (tyConsOfType rhs) -- NB: This is allowed to be conservative, returning True more often -- than it should. See comments on GHC.Core.TyCon.isForgetfulSynTyCon {- ************************************************************************ * * \subsection{Liftedness} * * ************************************************************************ -} -- | Tries to compute the 'Levity' of the given type. Returns either -- a definite 'Levity', or 'Nothing' if we aren't sure (e.g. the -- type is representation-polymorphic). -- -- Panics if the kind does not have the shape @TYPE r@. typeLevity_maybe :: HasDebugCallStack => Type -> Maybe Levity typeLevity_maybe ty = runtimeRepLevity_maybe (getRuntimeRep ty) -- | Is the given type definitely unlifted? -- See "Type#type_classification" for what an unlifted type is. -- -- Panics on representation-polymorphic types; See 'mightBeUnliftedType' for -- a more approximate predicate that behaves better in the presence of -- representation polymorphism. 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 = case typeLevity_maybe ty of Just Lifted -> False Just Unlifted -> True Nothing -> pprPanic "isUnliftedType" (ppr ty <+> dcolon <+> ppr (typeKind ty)) -- | Returns: -- -- * 'False' if the type is /guaranteed/ unlifted or -- * 'True' if it lifted, OR we aren't sure -- (e.g. in a representation-polymorphic case) mightBeLiftedType :: Type -> Bool mightBeLiftedType = mightBeLifted . typeLevity_maybe -- | Returns: -- -- * 'False' if the type is /guaranteed/ lifted or -- * 'True' if it is unlifted, OR we aren't sure -- (e.g. in a representation-polymorphic case) mightBeUnliftedType :: Type -> Bool mightBeUnliftedType = mightBeUnlifted . typeLevity_maybe -- | See "Type#type_classification" for what a boxed type is. -- Panics on representation-polymorphic types; See 'mightBeUnliftedType' for -- a more approximate predicate that behaves better in the presence of -- representation polymorphism. isBoxedType :: Type -> Bool isBoxedType ty = isBoxedRuntimeRep (getRuntimeRep 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 = Just LiftedRep@. Returns 'Nothing' if this is not -- possible. getRuntimeRep_maybe :: HasDebugCallStack => Type -> Maybe RuntimeRepType getRuntimeRep_maybe = kindRep_maybe . typeKind -- | Extract the RuntimeRep classifier of a type. For instance, -- @getRuntimeRep_maybe Int = LiftedRep@. Panics if this is not possible. getRuntimeRep :: HasDebugCallStack => Type -> RuntimeRepType getRuntimeRep ty = case getRuntimeRep_maybe ty of Just r -> r Nothing -> pprPanic "getRuntimeRep" (ppr ty <+> dcolon <+> ppr (typeKind ty)) -- | Extract the 'Levity' of a type. For example, @getLevity_maybe Int = Just Lifted@, -- @getLevity (Array# Int) = Just Unlifted@, @getLevity Float# = Nothing@. -- -- Returns 'Nothing' if this is not possible. Does not look through type family applications. getLevity_maybe :: HasDebugCallStack => Type -> Maybe Type getLevity_maybe ty | Just rep <- getRuntimeRep_maybe ty -- Directly matching on TyConApp after expanding type synonyms -- saves allocations compared to `splitTyConApp_maybe`. See #22254. -- Given that this is a pretty hot function we make use of the fact -- and use isTyConKeyApp_maybe instead. , Just [lev] <- isTyConKeyApp_maybe boxedRepDataConKey rep = Just lev | otherwise = Nothing -- | Extract the 'Levity' of a type. For example, @getLevity Int = Lifted@, -- or @getLevity (Array# Int) = Unlifted@. -- -- Panics if this is not possible. Does not look through type family applications. getLevity :: HasDebugCallStack => Type -> Type getLevity ty | Just lev <- getLevity_maybe ty = lev | otherwise = pprPanic "getLevity" (ppr ty <+> dcolon <+> ppr (typeKind ty)) 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 representation-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 "GHC.Core".) 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 = tvs `disjointVarSet` tyCoVarsOfType ty | Just (t, ty') <- splitForAllTyCoVar_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 GHC.Core), 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 #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 _ w t1 t2) = seqType w `seq` seqType t1 `seq` seqType t2 seqType (TyConApp tc tys) = tc `seq` seqTypes tys seqType (ForAllTy (Bndr tv _) ty) = seqType (varType 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 {- ************************************************************************ * * The kind of a type * * ************************************************************************ Note [Kinding rules for types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here are the key kinding rules for types torc1 is TYPE or CONSTRAINT torc2 is TYPE or CONSTRAINT t1 : torc1 rep1 t2 : torc2 rep2 (FUN) ---------------- t1 -> t2 : torc2 LiftedRep -- In fact the arrow varies with torc1/torc2 -- See Note [Function type constructors and FunTy] -- in GHC.Builtin.Types.Prim torc is TYPE or CONSTRAINT ty : body_torc rep bndr_torc is Type or Constraint ki : bndr_torc `a` is a type variable `a` is not free in rep (FORALL1) ----------------------- forall (a::ki). ty : torc rep torc is TYPE or CONSTRAINT ty : body_torc rep `c` is a coercion variable `c` is not free in rep `c` is free in ty -- Surprise 1! (FORALL2) ------------------------- forall (cv::k1 ~#{N,R} k2). ty : body_torc LiftedRep -- Surprise 2! Note that: * (FORALL1) rejects (forall (a::Maybe). blah) * (FORALL1) accepts (forall (a :: t1~t2) blah), where the type variable (not coercion variable!) 'a' has a kind (t1~t2) that in turn has kind Constraint. See Note [Constraints in kinds] in GHC.Core.TyCo.Rep. * (FORALL2) Surprise 1: See GHC.Core.TyCo.Rep Note [Unused coercion variable in ForAllTy] * (FORALL2) Surprise 2: coercion abstractions are not erased, so this must be LiftedRep, just like (FUN). (FORALL2) is just a dependent form of (FUN). Note [Phantom type variables in kinds] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider type K (r :: RuntimeRep) = Type -- Note 'r' is unused data T r :: K r -- T :: forall r -> K r foo :: forall r. T r The body of the forall in foo's type has kind (K r), and normally it would make no sense to have forall r. (ty :: K r) because the kind of the forall would escape the binding of 'r'. But in this case it's fine because (K r) expands to Type, so we explicitly /permit/ the type forall r. T r To accommodate such a type, in typeKind (forall a.ty) we use occCheckExpand to expand any type synonyms in the kind of 'ty' to eliminate 'a'. See kinding rule (FORALL) in Note [Kinding rules for types] See also * GHC.Core.Type.occCheckExpand * GHC.Core.Utils.coreAltsType * GHC.Tc.Validity.checkEscapingKind all of which grapple with the same problem. See #14939. -} ----------------------------- typeKind :: HasDebugCallStack => Type -> Kind -- No need to expand synonyms typeKind (TyConApp tc tys) = piResultTys (tyConKind tc) tys typeKind (LitTy l) = typeLiteralKind l typeKind (FunTy { ft_af = af }) = case funTyFlagResultTypeOrConstraint af of TypeLike -> liftedTypeKind ConstraintLike -> constraintKind typeKind (TyVarTy tyvar) = tyVarKind tyvar typeKind (CastTy _ty co) = coercionRKind co typeKind (CoercionTy co) = coercionType co typeKind (AppTy fun arg) = go fun [arg] where -- Accumulate the type arguments, so we can call piResultTys, -- rather than a succession of calls to piResultTy (which is -- asymptotically costly as the number of arguments increases) go (AppTy fun arg) args = go fun (arg:args) go fun args = piResultTys (typeKind fun) args typeKind ty@(ForAllTy {}) = case occCheckExpand tvs body_kind of -- We must make sure tv does not occur in kind -- As it is already out of scope! -- See Note [Phantom type variables in kinds] Nothing -> pprPanic "typeKind" (ppr ty $$ ppr tvs $$ ppr body <+> dcolon <+> ppr body_kind) Just k' | all isTyVar tvs -> k' -- Rule (FORALL1) | otherwise -> lifted_kind_from_body -- Rule (FORALL2) where (tvs, body) = splitForAllTyVars ty body_kind = typeKind body lifted_kind_from_body -- Implements (FORALL2) = case sORTKind_maybe body_kind of Just (ConstraintLike, _) -> constraintKind Just (TypeLike, _) -> liftedTypeKind Nothing -> pprPanic "typeKind" (ppr body_kind) --------------------------------------------- sORTKind_maybe :: Kind -> Maybe (TypeOrConstraint, Type) -- Sees if the argument is of form (TYPE rep) or (CONSTRAINT rep) -- and if so returns which, and the runtime rep -- -- This is a "hot" function. Do not call splitTyConApp_maybe here, -- to avoid the faff with FunTy sORTKind_maybe (TyConApp tc tys) -- First, short-cuts for Type and Constraint that do no allocation | tc_uniq == liftedTypeKindTyConKey = assert( null tys ) $ Just (TypeLike, liftedRepTy) | tc_uniq == constraintKindTyConKey = assert( null tys ) $ Just (ConstraintLike, liftedRepTy) | tc_uniq == tYPETyConKey = get_rep TypeLike | tc_uniq == cONSTRAINTTyConKey = get_rep ConstraintLike | Just ty' <- expandSynTyConApp_maybe tc tys = sORTKind_maybe ty' where !tc_uniq = tyConUnique tc -- This bang on tc_uniq is important. It means that sORTKind_maybe starts -- by evaluating tc_uniq, and then ends up with a single case with a 4-way branch get_rep torc = case tys of (rep:_reps) -> assert (null _reps) $ Just (torc, rep) [] -> Nothing sORTKind_maybe _ = Nothing typeTypeOrConstraint :: HasDebugCallStack => Type -> TypeOrConstraint -- Precondition: expects a type that classifies values. -- Returns whether it is TypeLike or ConstraintLike. -- Equivalent to calling sORTKind_maybe, but faster in the FunTy case typeTypeOrConstraint ty = case coreFullView ty of FunTy { ft_af = af } -> funTyFlagResultTypeOrConstraint af ty' | Just (torc, _) <- sORTKind_maybe (typeKind ty') -> torc | otherwise -> pprPanic "typeOrConstraint" (ppr ty <+> dcolon <+> ppr (typeKind ty)) isPredTy :: HasDebugCallStack => Type -> Bool -- Precondition: expects a type that classifies values -- See Note [Types for coercions, predicates, and evidence] in GHC.Core.TyCo.Rep -- Returns True for types of kind (CONSTRAINT _), False for ones of kind (TYPE _) isPredTy ty = case typeTypeOrConstraint ty of TypeLike -> False ConstraintLike -> True ----------------------------------------- -- | Does this classify a type allowed to have values? Responds True to things -- like *, TYPE Lifted, TYPE IntRep, TYPE v, Constraint. isTYPEorCONSTRAINT :: Kind -> Bool -- ^ True of a kind `TYPE _` or `CONSTRAINT _` isTYPEorCONSTRAINT k = isJust (sORTKind_maybe k) isConstraintLikeKind :: Kind -> Bool -- True of (CONSTRAINT _) isConstraintLikeKind kind = case sORTKind_maybe kind of Just (ConstraintLike, _) -> True _ -> False isConstraintKind :: Kind -> Bool -- True of (CONSTRAINT LiftedRep) isConstraintKind kind = case sORTKind_maybe kind of Just (ConstraintLike, rep) -> isLiftedRuntimeRep rep _ -> False tcIsLiftedTypeKind :: Kind -> Bool -- ^ Is this kind equivalent to 'Type' i.e. TYPE LiftedRep? tcIsLiftedTypeKind kind | Just (TypeLike, rep) <- sORTKind_maybe kind = isLiftedRuntimeRep rep | otherwise = False tcIsBoxedTypeKind :: Kind -> Bool -- ^ Is this kind equivalent to @TYPE (BoxedRep l)@ for some @l :: Levity@? tcIsBoxedTypeKind kind | Just (TypeLike, rep) <- sORTKind_maybe kind = isBoxedRuntimeRep rep | otherwise = False -- | Is this kind equivalent to @TYPE r@ (for some unknown r)? -- -- This considers 'Constraint' to be distinct from @*@. isTypeLikeKind :: Kind -> Bool isTypeLikeKind kind = case sORTKind_maybe kind of Just (TypeLike, _) -> True _ -> False returnsConstraintKind :: Kind -> Bool -- True <=> the Kind ultimately returns a Constraint -- E.g. * -> Constraint -- forall k. k -> Constraint returnsConstraintKind kind | Just kind' <- coreView kind = returnsConstraintKind kind' returnsConstraintKind (ForAllTy _ ty) = returnsConstraintKind ty returnsConstraintKind (FunTy { ft_res = ty }) = returnsConstraintKind ty returnsConstraintKind kind = isConstraintLikeKind kind -------------------------- typeLiteralKind :: TyLit -> Kind typeLiteralKind (NumTyLit {}) = naturalTy typeLiteralKind (StrTyLit {}) = typeSymbolKind typeLiteralKind (CharTyLit {}) = charTy -- | Returns True if a type has a syntactically fixed runtime rep, -- as per Note [Fixed RuntimeRep] in GHC.Tc.Utils.Concrete. -- -- This function is equivalent to `isFixedRuntimeRepKind . typeKind` -- but much faster. -- -- __Precondition:__ The type has kind @('TYPE' blah)@ typeHasFixedRuntimeRep :: HasDebugCallStack => Type -> Bool typeHasFixedRuntimeRep = go where go (TyConApp tc _) | tcHasFixedRuntimeRep tc = True go (FunTy {}) = True go (LitTy {}) = True go (ForAllTy _ ty) = go ty go ty = isFixedRuntimeRepKind (typeKind ty) argsHaveFixedRuntimeRep :: Type -> Bool -- ^ True if the argument types of this function type -- all have a fixed-runtime-rep argsHaveFixedRuntimeRep ty = all ok bndrs where ok :: PiTyBinder -> Bool ok (Anon ty _) = typeHasFixedRuntimeRep (scaledThing ty) ok _ = True bndrs :: [PiTyBinder] (bndrs, _) = splitPiTys ty -- | Checks that a kind of the form 'Type', 'Constraint' -- or @'TYPE r@ is concrete. See 'isConcrete'. -- -- __Precondition:__ The type has kind `TYPE blah` or `CONSTRAINT blah` isFixedRuntimeRepKind :: HasDebugCallStack => Kind -> Bool isFixedRuntimeRepKind k = assertPpr (isTYPEorCONSTRAINT k) (ppr k) $ -- the isLiftedTypeKind check is necessary b/c of Constraint isConcrete k -- | Tests whether the given type is concrete, i.e. it -- whether it consists only of concrete type constructors, -- concrete type variables, and applications. -- -- See Note [Concrete types] in GHC.Tc.Utils.Concrete. isConcrete :: Type -> Bool isConcrete = go where go ty | Just ty' <- coreView ty = go ty' go (TyVarTy tv) = isConcreteTyVar tv go (AppTy ty1 ty2) = go ty1 && go ty2 go (TyConApp tc tys) | isConcreteTyCon tc = all go tys | otherwise = False go ForAllTy{} = False go (FunTy _ w t1 t2) = go w && go (typeKind t1) && go t1 && go (typeKind t2) && go t2 go LitTy{} = True go CastTy{} = False go CoercionTy{} = False {- %************************************************************************ %* * Pretty-printing %* * %************************************************************************ Most pretty-printing is either in GHC.Core.TyCo.Rep or GHC.Iface.Type. -} -- | Does a 'TyCon' (that is applied to some number of arguments) need to be -- ascribed with an explicit kind signature to resolve ambiguity if rendered as -- a source-syntax type? -- (See @Note [When does a tycon application need an explicit kind signature?]@ -- for a full explanation of what this function checks for.) tyConAppNeedsKindSig :: Bool -- ^ Should specified binders count towards injective positions in -- the kind of the TyCon? (If you're using visible kind -- applications, then you want True here. -> TyCon -> Int -- ^ The number of args the 'TyCon' is applied to. -> Bool -- ^ Does @T t_1 ... t_n@ need a kind signature? (Where @n@ is the -- number of arguments) tyConAppNeedsKindSig spec_inj_pos tc n_args | LT <- listLengthCmp tc_binders n_args = False | otherwise = let (dropped_binders, remaining_binders) = splitAt n_args tc_binders result_kind = mkTyConKind remaining_binders tc_res_kind result_vars = tyCoVarsOfType result_kind dropped_vars = fvVarSet $ mapUnionFV injective_vars_of_binder dropped_binders in not (subVarSet result_vars dropped_vars) where tc_binders = tyConBinders tc tc_res_kind = tyConResKind tc -- Returns the variables that would be fixed by knowing a TyConBinder. See -- Note [When does a tycon application need an explicit kind signature?] -- for a more detailed explanation of what this function does. injective_vars_of_binder :: TyConBinder -> FV injective_vars_of_binder (Bndr tv vis) = case vis of AnonTCB af | isVisibleFunArg af -> injectiveVarsOfType False -- conservative choice (varType tv) NamedTCB argf | source_of_injectivity argf -> unitFV tv `unionFV` injectiveVarsOfType False (varType tv) _ -> emptyFV source_of_injectivity Required = True source_of_injectivity Specified = spec_inj_pos source_of_injectivity Inferred = False {- Note [When does a tycon application need an explicit kind signature?] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ There are a couple of places in GHC where we convert Core Types into forms that more closely resemble user-written syntax. These include: 1. Template Haskell Type reification (see, for instance, GHC.Tc.Gen.Splice.reify_tc_app) 2. Converting Types to LHsTypes (such as in Haddock.Convert in haddock) This conversion presents a challenge: how do we ensure that the resulting type has enough kind information so as not to be ambiguous? To better motivate this question, consider the following Core type: -- Foo :: Type -> Type type Foo = Proxy Type There is nothing ambiguous about the RHS of Foo in Core. But if we were to, say, reify it into a TH Type, then it's tempting to just drop the invisible Type argument and simply return `Proxy`. But now we've lost crucial kind information: we don't know if we're dealing with `Proxy Type` or `Proxy Bool` or `Proxy Int` or something else! We've inadvertently introduced ambiguity. Unlike in other situations in GHC, we can't just turn on -fprint-explicit-kinds, as we need to produce something which has the same structure as a source-syntax type. Moreover, we can't rely on visible kind application, since the first kind argument to Proxy is inferred, not specified. Our solution is to annotate certain tycons with their kinds whenever they appear in applied form in order to resolve the ambiguity. For instance, we would reify the RHS of Foo like so: type Foo = (Proxy :: Type -> Type) We need to devise an algorithm that determines precisely which tycons need these explicit kind signatures. We certainly don't want to annotate _every_ tycon with a kind signature, or else we might end up with horribly bloated types like the following: (Either :: Type -> Type -> Type) (Int :: Type) (Char :: Type) We only want to annotate tycons that absolutely require kind signatures in order to resolve some sort of ambiguity, and nothing more. Suppose we have a tycon application (T ty_1 ... ty_n). Why might this type require a kind signature? It might require it when we need to fill in any of T's omitted arguments. By "omitted argument", we mean one that is dropped when reifying ty_1 ... ty_n. Sometimes, the omitted arguments are inferred and specified arguments (e.g., TH reification in GHC.Tc.Gen.Splice), and sometimes the omitted arguments are only the inferred ones (e.g., in situations where specified arguments are reified through visible kind application). Regardless, the key idea is that _some_ arguments are going to be omitted after reification, and the only mechanism we have at our disposal for filling them in is through explicit kind signatures. What do we mean by "fill in"? Let's consider this small example: T :: forall {k}. Type -> (k -> Type) -> k Moreover, we have this application of T: T @{j} Int aty When we reify this type, we omit the inferred argument @{j}. Is it fixed by the other (non-inferred) arguments? Yes! If we know the kind of (aty :: blah), then we'll generate an equality constraint (kappa -> Type) and, assuming we can solve it, that will fix `kappa`. (Here, `kappa` is the unification variable that we instantiate `k` with.) Therefore, for any application of a tycon T to some arguments, the Question We Must Answer is: * Given the first n arguments of T, do the kinds of the non-omitted arguments fill in the omitted arguments? (This is still a bit hand-wavy, but we'll refine this question incrementally as we explain more of the machinery underlying this process.) Answering this question is precisely the role that the `injectiveVarsOfType` and `injective_vars_of_binder` functions exist to serve. If an omitted argument `a` appears in the set returned by `injectiveVarsOfType ty`, then knowing `ty` determines (i.e., fills in) `a`. (More on `injective_vars_of_binder` in a bit.) More formally, if `a` is in `injectiveVarsOfType ty` and S1(ty) ~ S2(ty), then S1(a) ~ S2(a), where S1 and S2 are arbitrary substitutions. For example, is `F` is a non-injective type family, then injectiveVarsOfType(Either c (Maybe (a, F b c))) = {a, c} Now that we know what this function does, here is a second attempt at the Question We Must Answer: * Given the first n arguments of T (ty_1 ... ty_n), consider the binders of T that are instantiated by non-omitted arguments. Do the injective variables of these binders fill in the remainder of T's kind? Alright, we're getting closer. Next, we need to clarify what the injective variables of a tycon binder are. This the role that the `injective_vars_of_binder` function serves. Here is what this function does for each form of tycon binder: * Anonymous binders are injective positions. For example, in the promoted data constructor '(:): '(:) :: forall a. a -> [a] -> [a] The second and third tyvar binders (of kinds `a` and `[a]`) are both anonymous, so if we had '(:) 'True '[], then the kinds of 'True and '[] would contribute to the kind of '(:) 'True '[]. Therefore, injective_vars_of_binder(_ :: a) = injectiveVarsOfType(a) = {a}. (Similarly, injective_vars_of_binder(_ :: [a]) = {a}.) * Named binders: - Inferred binders are never injective positions. For example, in this data type: data Proxy a Proxy :: forall {k}. k -> Type If we had Proxy 'True, then the kind of 'True would not contribute to the kind of Proxy 'True. Therefore, injective_vars_of_binder(forall {k}. ...) = {}. - Required binders are injective positions. For example, in this data type: data Wurble k (a :: k) :: k Wurble :: forall k -> k -> k The first tyvar binder (of kind `forall k`) has required visibility, so if we had Wurble (Maybe a) Nothing, then the kind of Maybe a would contribute to the kind of Wurble (Maybe a) Nothing. Hence, injective_vars_of_binder(forall a -> ...) = {a}. - Specified binders /might/ be injective positions, depending on how you approach things. Continuing the '(:) example: '(:) :: forall a. a -> [a] -> [a] Normally, the (forall a. ...) tyvar binder wouldn't contribute to the kind of '(:) 'True '[], since it's not explicitly instantiated by the user. But if visible kind application is enabled, then this is possible, since the user can write '(:) @Bool 'True '[]. (In that case, injective_vars_of_binder(forall a. ...) = {a}.) There are some situations where using visible kind application is appropriate and others where it is not (e.g., TH reification), so the `injective_vars_of_binder` function is parameterized by a Bool which decides if specified binders should be counted towards injective positions or not. Now that we've defined injective_vars_of_binder, we can refine the Question We Must Answer once more: * Given the first n arguments of T (ty_1 ... ty_n), consider the binders of T that are instantiated by non-omitted arguments. For each such binder b_i, take the union of all injective_vars_of_binder(b_i). Is this set a superset of the free variables of the remainder of T's kind? If the answer to this question is "no", then (T ty_1 ... ty_n) needs an explicit kind signature, since T's kind has kind variables leftover that aren't fixed by the non-omitted arguments. One last sticking point: what does "the remainder of T's kind" mean? You might be tempted to think that it corresponds to all of the arguments in the kind of T that would normally be instantiated by omitted arguments. But this isn't quite right, strictly speaking. Consider the following (silly) example: S :: forall {k}. Type -> Type And suppose we have this application of S: S Int Bool The Int argument would be omitted, and injective_vars_of_binder(_ :: Type) = {}. This is not a superset of {k}, which might suggest that (S Bool) needs an explicit kind signature. But (S Bool :: Type) doesn't actually fix `k`! This is because the kind signature only affects the /result/ of the application, not all of the individual arguments. So adding a kind signature here won't make a difference. Therefore, the fourth (and final) iteration of the Question We Must Answer is: * Given the first n arguments of T (ty_1 ... ty_n), consider the binders of T that are instantiated by non-omitted arguments. For each such binder b_i, take the union of all injective_vars_of_binder(b_i). Is this set a superset of the free variables of the kind of (T ty_1 ... ty_n)? Phew, that was a lot of work! How can be sure that this is correct? That is, how can we be sure that in the event that we leave off a kind annotation, that one could infer the kind of the tycon application from its arguments? It's essentially a proof by induction: if we can infer the kinds of every subtree of a type, then the whole tycon application will have an inferrable kind--unless, of course, the remainder of the tycon application's kind has uninstantiated kind variables. What happens if T is oversaturated? That is, if T's kind has fewer than n arguments, in the case that the concrete application instantiates a result kind variable with an arrow kind? If we run out of arguments, we do not attach a kind annotation. This should be a rare case, indeed. Here is an example: data T1 :: k1 -> k2 -> * data T2 :: k1 -> k2 -> * type family G (a :: k) :: k type instance G T1 = T2 type instance F Char = (G T1 Bool :: (* -> *) -> *) -- F from above Here G's kind is (forall k. k -> k), and the desugared RHS of that last instance of F is (G (* -> (* -> *) -> *) (T1 * (* -> *)) Bool). According to the algorithm above, there are 3 arguments to G so we should peel off 3 arguments in G's kind. But G's kind has only two arguments. This is the rare special case, and we choose not to annotate the application of G with a kind signature. After all, we needn't do this, since that instance would be reified as: type instance F Char = G (T1 :: * -> (* -> *) -> *) Bool So the kind of G isn't ambiguous anymore due to the explicit kind annotation on its argument. See #8953 and test th/T8953. -} {- ************************************************************************ * * Multiplicities * * ************************************************************************ These functions would prefer to be in GHC.Core.Multiplicity, but they some are used elsewhere in this module, and wanted to bring their friends here with them. -} unrestricted, linear, tymult :: a -> Scaled a -- | Scale a payload by Many unrestricted = Scaled ManyTy -- | Scale a payload by One linear = Scaled OneTy -- | Scale a payload by Many; used for type arguments in core tymult = Scaled ManyTy irrelevantMult :: Scaled a -> a irrelevantMult = scaledThing mkScaled :: Mult -> a -> Scaled a mkScaled = Scaled scaledSet :: Scaled a -> b -> Scaled b scaledSet (Scaled m _) b = Scaled m b pattern OneTy :: Mult pattern OneTy <- (isOneTy -> True) where OneTy = oneDataConTy pattern ManyTy :: Mult pattern ManyTy <- (isManyTy -> True) where ManyTy = manyDataConTy isManyTy :: Mult -> Bool isManyTy ty | Just tc <- tyConAppTyCon_maybe ty = tc `hasKey` manyDataConKey isManyTy _ = False isOneTy :: Mult -> Bool isOneTy ty | Just tc <- tyConAppTyCon_maybe ty = tc `hasKey` oneDataConKey isOneTy _ = False isLinearType :: Type -> Bool -- ^ @isLinear t@ returns @True@ of a if @t@ is a type of (curried) function -- where at least one argument is linear (or otherwise non-unrestricted). We use -- this function to check whether it is safe to eta reduce an Id in CorePrep. It -- is always safe to return 'True', because 'True' deactivates the optimisation. isLinearType ty = case ty of FunTy _ ManyTy _ res -> isLinearType res FunTy _ _ _ _ -> True ForAllTy _ res -> isLinearType res _ -> False {- ********************************************************************* * * Space-saving construction * * ********************************************************************* -} {- Note [Using synonyms to compress types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Was: [Prefer Type over TYPE (BoxedRep Lifted)] The Core of nearly any program will have numerous occurrences of the Types TyConApp BoxedRep [TyConApp Lifted []] -- Synonym LiftedRep TyConApp BoxedRep [TyConApp Unlifted []] -- Synonym UnliftedREp TyConApp TYPE [TyConApp LiftedRep []] -- Synonym Type TyConApp TYPE [TyConApp UnliftedRep []] -- Synonym UnliftedType While investigating #17292 we found that these constituted a majority of all TyConApp constructors on the heap: (From a sample of 100000 TyConApp closures) 0x45f3523 - 28732 - `Type` 0x420b840702 - 9629 - generic type constructors 0x42055b7e46 - 9596 0x420559b582 - 9511 0x420bb15a1e - 9509 0x420b86c6ba - 9501 0x42055bac1e - 9496 0x45e68fd - 538 - `TYPE ...` Consequently, we try hard to ensure that operations on such types are efficient. Specifically, we strive to a. Avoid heap allocation of such types; use a single static TyConApp b. Use a small (shallow in the tree-depth sense) representation for such types Goal (b) is particularly useful as it makes traversals (e.g. free variable traversal, substitution, and comparison) more efficient. Comparison in particular takes special advantage of nullary type synonym applications (e.g. things like @TyConApp typeTyCon []@), Note [Comparing nullary type synonyms] in "GHC.Core.Type". To accomplish these we use a number of tricks, implemented by mkTyConApp. 1. Instead of (TyConApp BoxedRep [TyConApp Lifted []]), we prefer a statically-allocated (TyConApp LiftedRep []) where `LiftedRep` is a type synonym: type LiftedRep = BoxedRep Lifted Similarly for UnliftedRep 2. Instead of (TyConApp TYPE [TyConApp LiftedRep []]) we prefer the statically-allocated (TyConApp Type []) where `Type` is a type synonym type Type = TYPE LiftedRep Similarly for UnliftedType These serve goal (b) since there are no applied type arguments to traverse, e.g., during comparison. 3. We have a single, statically allocated top-level binding to represent `TyConApp GHC.Types.Type []` (namely 'GHC.Builtin.Types.Prim.liftedTypeKind'), ensuring that we don't need to allocate such types (goal (a)). See functions mkTYPEapp and mkBoxedRepApp 4. We use the sharing mechanism described in Note [Sharing nullary TyConApps] in GHC.Core.TyCon to ensure that we never need to allocate such nullary applications (goal (a)). See #17958, #20541 -} -- | 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 [] = -- See Note [Sharing nullary TyConApps] in GHC.Core.TyCon mkTyConTy tycon mkTyConApp tycon tys@(ty1:rest) | Just fun_ty <- tyConAppFunTy_maybe tycon tys = fun_ty -- See Note [Using synonyms to compress types] | key == tYPETyConKey , Just ty <- mkTYPEapp_maybe ty1 = assert (null rest) ty | key == cONSTRAINTTyConKey , Just ty <- mkCONSTRAINTapp_maybe ty1 = assert (null rest) ty -- See Note [Using synonyms to compress types] | key == boxedRepDataConTyConKey , Just ty <- mkBoxedRepApp_maybe ty1 = assert (null rest) ty | key == tupleRepDataConTyConKey , Just ty <- mkTupleRepApp_maybe ty1 = assert (null rest) ty -- The catch-all case | otherwise = TyConApp tycon tys where key = tyConUnique tycon {- Note [Care using synonyms to compress types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Using a synonym to compress a types has a tricky wrinkle. Consider coreView applied to (TyConApp LiftedRep []) * coreView expands the LiftedRep synonym: type LiftedRep = BoxedRep Lifted * Danger: we might apply the empty substitution to the RHS of the synonym. And substTy calls mkTyConApp BoxedRep [Lifted]. And mkTyConApp compresses that back to LiftedRep. Loop! * Solution: in expandSynTyConApp_maybe, don't call substTy for nullary type synonyms. That's more efficient anyway. -} mkTYPEapp :: RuntimeRepType -> Type mkTYPEapp rr = case mkTYPEapp_maybe rr of Just ty -> ty Nothing -> TyConApp tYPETyCon [rr] mkTYPEapp_maybe :: RuntimeRepType -> Maybe Type -- ^ Given a @RuntimeRep@, applies @TYPE@ to it. -- On the fly it rewrites -- TYPE LiftedRep --> liftedTypeKind (a synonym) -- TYPE UnliftedRep --> unliftedTypeKind (ditto) -- TYPE ZeroBitRep --> zeroBitTypeKind (ditto) -- NB: no need to check for TYPE (BoxedRep Lifted), TYPE (BoxedRep Unlifted) -- because those inner types should already have been rewritten -- to LiftedRep and UnliftedRep respectively, by mkTyConApp -- -- see Note [TYPE and CONSTRAINT] in GHC.Builtin.Types.Prim. -- See Note [Using synonyms to compress types] in GHC.Core.Type {-# NOINLINE mkTYPEapp_maybe #-} mkTYPEapp_maybe (TyConApp tc args) | key == liftedRepTyConKey = assert (null args) $ Just liftedTypeKind -- TYPE LiftedRep | key == unliftedRepTyConKey = assert (null args) $ Just unliftedTypeKind -- TYPE UnliftedRep | key == zeroBitRepTyConKey = assert (null args) $ Just zeroBitTypeKind -- TYPE ZeroBitRep where key = tyConUnique tc mkTYPEapp_maybe _ = Nothing ------------------ mkCONSTRAINTapp :: RuntimeRepType -> Type -- ^ Just like mkTYPEapp mkCONSTRAINTapp rr = case mkCONSTRAINTapp_maybe rr of Just ty -> ty Nothing -> TyConApp cONSTRAINTTyCon [rr] mkCONSTRAINTapp_maybe :: RuntimeRepType -> Maybe Type -- ^ Just like mkTYPEapp_maybe {-# NOINLINE mkCONSTRAINTapp_maybe #-} mkCONSTRAINTapp_maybe (TyConApp tc args) | tc `hasKey` liftedRepTyConKey = assert (null args) $ Just constraintKind -- CONSTRAINT LiftedRep mkCONSTRAINTapp_maybe _ = Nothing ------------------ mkBoxedRepApp_maybe :: LevityType -> Maybe Type -- ^ Given a `Levity`, apply `BoxedRep` to it -- On the fly, rewrite -- BoxedRep Lifted --> liftedRepTy (a synonym) -- BoxedRep Unlifted --> unliftedRepTy (ditto) -- See Note [TYPE and CONSTRAINT] in GHC.Builtin.Types.Prim. -- See Note [Using synonyms to compress types] in GHC.Core.Type {-# NOINLINE mkBoxedRepApp_maybe #-} mkBoxedRepApp_maybe (TyConApp tc args) | key == liftedDataConKey = assert (null args) $ Just liftedRepTy -- BoxedRep Lifted | key == unliftedDataConKey = assert (null args) $ Just unliftedRepTy -- BoxedRep Unlifted where key = tyConUnique tc mkBoxedRepApp_maybe _ = Nothing mkTupleRepApp_maybe :: Type -> Maybe Type -- ^ Given a `[RuntimeRep]`, apply `TupleRep` to it -- On the fly, rewrite -- TupleRep [] -> zeroBitRepTy (a synonym) -- See Note [TYPE and CONSTRAINT] in GHC.Builtin.Types.Prim. -- See Note [Using synonyms to compress types] in GHC.Core.Type {-# NOINLINE mkTupleRepApp_maybe #-} mkTupleRepApp_maybe (TyConApp tc args) | key == nilDataConKey = assert (isSingleton args) $ Just zeroBitRepTy -- ZeroBitRep where key = tyConUnique tc mkTupleRepApp_maybe _ = Nothing typeOrConstraintKind :: TypeOrConstraint -> RuntimeRepType -> Kind typeOrConstraintKind TypeLike rep = mkTYPEapp rep typeOrConstraintKind ConstraintLike rep = mkCONSTRAINTapp rep