X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypes%2FType.lhs;h=f894cd304f1e0bac556c732613af689dbf0e647d;hp=c3013ab5b3a12e7403912adc44c710d1d221a3de;hb=b06d623b2e367a572de5daf06d6a0b12c2740471;hpb=a4c34367ce3e836f52f0ffb1e379ce81b8d65316 diff --git a/compiler/types/Type.lhs b/compiler/types/Type.lhs index c3013ab..f894cd3 100644 --- a/compiler/types/Type.lhs +++ b/compiler/types/Type.lhs @@ -1,72 +1,83 @@ % +% (c) The University of Glasgow 2006 % (c) The GRASP/AQUA Project, Glasgow University, 1998 % -\section[Type]{Type - public interface} +Type - public interface \begin{code} +{-# OPTIONS -fno-warn-incomplete-patterns #-} +-- The above warning supression flag is a temporary kludge. +-- While working on this module you are encouraged to remove it and fix +-- any warnings in the module. See +-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings +-- for details + +-- | Main functions for manipulating types and type-related things module Type ( - -- re-exports from TypeRep - TyThing(..), Type, PredType(..), ThetaType, - funTyCon, + -- Note some of this is just re-exports from TyCon.. - -- Kinds - Kind, SimpleKind, KindVar, - kindFunResult, splitKindFunTys, - - liftedTypeKindTyCon, openTypeKindTyCon, unliftedTypeKindTyCon, - argTypeKindTyCon, ubxTupleKindTyCon, - - liftedTypeKind, unliftedTypeKind, openTypeKind, - argTypeKind, ubxTupleKind, - - tySuperKind, coSuperKind, - - isLiftedTypeKind, isUnliftedTypeKind, isOpenTypeKind, - isUbxTupleKind, isArgTypeKind, isKind, isTySuperKind, - isCoSuperKind, isSuperKind, isCoercionKind, - mkArrowKind, mkArrowKinds, - - isSubArgTypeKind, isSubOpenTypeKind, isSubKind, defaultKind, eqKind, - isSubKindCon, - - -- Re-exports from TyCon - PrimRep(..), + -- * Main data types representing Types + -- $type_classification + + -- $representation_types + TyThing(..), Type, PredType(..), ThetaType, - mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy, + -- ** Constructing and deconstructing types + mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, mkAppTy, mkAppTys, splitAppTy, splitAppTys, splitAppTy_maybe, repSplitAppTy_maybe, mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe, splitFunTys, splitFunTysN, - funResultTy, funArgTy, zipFunTys, isFunTy, + funResultTy, funArgTy, zipFunTys, mkTyConApp, mkTyConTy, tyConAppTyCon, tyConAppArgs, splitTyConApp_maybe, splitTyConApp, - splitNewTyConApp_maybe, splitNewTyConApp, - repType, typePrimRep, coreView, tcView, kindView, + mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys, + applyTy, applyTys, applyTysD, isForAllTy, dropForAlls, + + -- (Newtypes) + newTyConInstRhs, carefullySplitNewType_maybe, + + -- (Type families) + tyFamInsts, predFamInsts, - mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys, - applyTy, applyTys, isForAllTy, dropForAlls, + -- (Source types) + mkPredTy, mkPredTys, mkFamilyTyConApp, isEqPred, - -- Source types - predTypeRep, mkPredTy, mkPredTys, + -- ** Common type constructors + funTyCon, - -- Newtypes - splitRecNewType_maybe, newTyConInstRhs, + -- ** Predicates on types + isTyVarTy, isFunTy, - -- Lifting and boxity - isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType, - isStrictType, isStrictPred, + -- (Lifting and boxity) + isUnLiftedType, isUnboxedTupleType, isAlgType, isClosedAlgType, + isPrimitiveType, isStrictType, isStrictPred, - -- Free variables + -- * Main data types representing Kinds + -- $kind_subtyping + Kind, SimpleKind, KindVar, + + -- ** Common Kinds and SuperKinds + liftedTypeKind, unliftedTypeKind, openTypeKind, + argTypeKind, ubxTupleKind, + + tySuperKind, coSuperKind, + + -- ** Common Kind type constructors + liftedTypeKindTyCon, openTypeKindTyCon, unliftedTypeKindTyCon, + argTypeKindTyCon, ubxTupleKindTyCon, + + -- * Type free variables tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta, - typeKind, addFreeTyVars, + expandTypeSynonyms, - -- Tidying up for printing + -- * Tidying type related things up for printing tidyType, tidyTypes, tidyOpenType, tidyOpenTypes, tidyTyVarBndr, tidyFreeTyVars, @@ -74,27 +85,46 @@ module Type ( tidyTopType, tidyPred, tidyKind, - -- Comparison - coreEqType, tcEqType, tcEqTypes, tcCmpType, tcCmpTypes, - tcEqPred, tcCmpPred, tcEqTypeX, + -- * Type comparison + coreEqType, coreEqType2, + tcEqType, tcEqTypes, tcCmpType, tcCmpTypes, + tcEqPred, tcEqPredX, tcCmpPred, tcEqTypeX, tcPartOfType, tcPartOfPred, - -- Seq + -- * Forcing evaluation of types seqType, seqTypes, - -- Type substitutions - TvSubstEnv, emptyTvSubstEnv, -- Representation widely visible - TvSubst(..), emptyTvSubst, -- Representation visible to a few friends + -- * Other views onto Types + coreView, tcView, kindView, + + repType, + + -- * Type representation for the code generator + PrimRep(..), + + typePrimRep, predTypeRep, + + -- * Main type substitution data types + TvSubstEnv, -- Representation widely visible + TvSubst(..), -- Representation visible to a few friends + + -- ** Manipulating type substitutions + emptyTvSubstEnv, emptyTvSubst, + mkTvSubst, mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst, - getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, + getTvSubstEnv, setTvSubstEnv, zapTvSubstEnv, getTvInScope, + extendTvInScope, extendTvInScopeList, extendTvSubst, extendTvSubstList, isInScope, composeTvSubst, zipTyEnv, + isEmptyTvSubst, - -- Performing substitution on types - substTy, substTys, substTyWith, substTheta, - substPred, substTyVar, substTyVarBndr, deShadowTy, lookupTyVar, + -- ** Performing substitution on types + substTy, substTys, substTyWith, substTysWith, substTheta, + substPred, substTyVar, substTyVars, substTyVarBndr, deShadowTy, lookupTyVar, - -- Pretty-printing - pprType, pprParendType, pprTyThingCategory, - pprPred, pprTheta, pprThetaArrow, pprClassPred, pprKind, pprParendKind + -- * Pretty-printing + pprType, pprParendType, pprTypeApp, pprTyThingCategory, pprTyThing, pprForAll, + pprPred, pprEqPred, pprTheta, pprThetaArrow, pprClassPred, pprKind, pprParendKind, + + pprSourceTyCon ) where #include "HsVersions.h" @@ -105,33 +135,81 @@ module Type ( import TypeRep -- friends: -import Var ( Var, TyVar, tyVarKind, tyVarName, - setTyVarName, setTyVarKind ) +import Var import VarEnv import VarSet -import OccName ( tidyOccName ) -import Name ( NamedThing(..), tidyNameOcc ) -import Class ( Class, classTyCon ) -import PrelNames( openTypeKindTyConKey, unliftedTypeKindTyConKey, - ubxTupleKindTyConKey, argTypeKindTyConKey ) -import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon, - isUnboxedTupleTyCon, isUnLiftedTyCon, - isFunTyCon, isNewTyCon, newTyConRep, newTyConRhs, - isAlgTyCon, tyConArity, isSuperKindTyCon, - tcExpandTyCon_maybe, coreExpandTyCon_maybe, - tyConKind, PrimRep(..), tyConPrimRep, tyConUnique, - isCoercionTyCon_maybe, isCoercionTyCon - ) +import Name +import Class +import TyCon -- others -import StaticFlags ( opt_DictsStrict ) -import Util ( mapAccumL, seqList, lengthIs, snocView, thenCmp, isEqual, all2 ) +import StaticFlags +import Util import Outputable -import UniqSet ( sizeUniqSet ) -- Should come via VarSet -import Maybe ( isJust ) +import FastString + +import Data.List +import Data.Maybe ( isJust ) \end{code} +\begin{code} +-- $type_classification +-- #type_classification# +-- +-- Types are one of: +-- +-- [Unboxed] Iff its representation is other than a pointer +-- Unboxed types are also unlifted. +-- +-- [Lifted] Iff it has bottom as an element. +-- Closures always have lifted types: i.e. any +-- let-bound identifier in Core must have a lifted +-- type. Operationally, a lifted object is one that +-- can be entered. +-- Only lifted types may be unified with a type variable. +-- +-- [Algebraic] Iff it is a type with one or more constructors, whether +-- declared with @data@ or @newtype@. +-- An algebraic type is one that can be deconstructed +-- with a case expression. This is /not/ the same as +-- lifted types, because we also include unboxed +-- tuples in this classification. +-- +-- [Data] Iff it is a type declared with @data@, or a boxed tuple. +-- +-- [Primitive] Iff it is a built-in type that can't be expressed in Haskell. +-- +-- Currently, all primitive types are unlifted, but that's not necessarily +-- the case: for example, @Int@ could be primitive. +-- +-- Some primitive types are unboxed, such as @Int#@, whereas some are boxed +-- but unlifted (such as @ByteArray#@). The only primitive types that we +-- classify as algebraic are the unboxed tuples. +-- +-- Some examples of type classifications that may make this a bit clearer are: +-- +-- @ +-- Type primitive boxed lifted algebraic +-- ----------------------------------------------------------------------------- +-- Int# Yes No No No +-- ByteArray# Yes Yes No No +-- (\# a, b \#) Yes No No Yes +-- ( a, b ) 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. Notably, 'PredTy's are removed +-- from the representation type while they do exist in the source types. +-- +-- You don't normally have to worry about this, as the utility functions in +-- this module will automatically convert a source into a representation type +-- if they are spotted, to the best of it's abilities. If you don't want this +-- to happen, use the equivalent functions from the "TcType" module. +\end{code} %************************************************************************ %* * @@ -139,57 +217,88 @@ import Maybe ( isJust ) %* * %************************************************************************ -In Core, we "look through" non-recursive newtypes and PredTypes. - \begin{code} {-# INLINE coreView #-} coreView :: Type -> Maybe Type --- Strips off the *top layer only* of a type to give +-- ^ In Core, we \"look through\" non-recursive newtypes and 'PredTypes': this +-- function tries to obtain a different view of the supplied type given this +-- +-- Strips off the /top layer only/ of a type to give -- its underlying representation type. -- Returns Nothing if there is nothing to look through. -- --- In the case of newtypes, it returns --- *either* a vanilla TyConApp (recursive newtype, or non-saturated) --- *or* the newtype representation (otherwise), meaning the --- type written in the RHS of the newtype decl, --- which may itself be a newtype +-- In the case of @newtype@s, it returns one of: +-- +-- 1) A vanilla 'TyConApp' (recursive newtype, or non-saturated) +-- +-- 2) The newtype representation (otherwise), meaning the +-- type written in the RHS of the newtype declaration, +-- which may itself be a newtype +-- +-- For example, with: +-- +-- > newtype R = MkR S +-- > newtype S = MkS T +-- > newtype T = MkT (T -> T) +-- +-- 'expandNewTcApp' on: -- --- Example: newtype R = MkR S --- newtype S = MkS T --- newtype T = MkT (T -> T) --- expandNewTcApp on R gives Just S --- on S gives Just T --- on T gives Nothing (no expansion) +-- * @R@ gives @Just S@ +-- * @S@ gives @Just T@ +-- * @T@ gives @Nothing@ (no expansion) -- By being non-recursive and inlined, this case analysis gets efficiently -- joined onto the case analysis that the caller is already doing -coreView (NoteTy _ ty) = Just ty -coreView (PredTy p) = Just (predTypeRep p) +coreView (PredTy p) + | isEqPred p = Nothing + | otherwise = Just (predTypeRep p) coreView (TyConApp tc tys) | Just (tenv, rhs, tys') <- coreExpandTyCon_maybe tc tys = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys') -- Its important to use mkAppTys, rather than (foldl AppTy), -- because the function part might well return a -- partially-applied type constructor; indeed, usually will! -coreView ty = Nothing +coreView _ = Nothing ----------------------------------------------- {-# INLINE tcView #-} tcView :: Type -> Maybe Type --- Same, but for the type checker, which just looks through synonyms -tcView (NoteTy _ ty) = Just ty +-- ^ Similar to 'coreView', but for the type checker, which just looks through synonyms tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- tcExpandTyCon_maybe tc tys = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys') -tcView ty = Nothing +tcView _ = Nothing + +----------------------------------------------- +expandTypeSynonyms :: Type -> Type +-- ^ Expand out all type synonyms. Actually, it'd suffice to expand out +-- just the ones that discard type variables (e.g. type Funny a = Int) +-- But we don't know which those are currently, so we just expand all. +expandTypeSynonyms ty + = go ty + where + go (TyConApp tc tys) + | Just (tenv, rhs, tys') <- tcExpandTyCon_maybe tc tys + = go (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys') + | otherwise + = TyConApp tc (map go tys) + go (TyVarTy tv) = TyVarTy tv + go (AppTy t1 t2) = AppTy (go t1) (go t2) + go (FunTy t1 t2) = FunTy (go t1) (go t2) + go (ForAllTy tv t) = ForAllTy tv (go t) + go (PredTy p) = PredTy (go_pred p) + + go_pred (ClassP c ts) = ClassP c (map go ts) + go_pred (IParam ip t) = IParam ip (go t) + go_pred (EqPred t1 t2) = EqPred (go t1) (go t2) ----------------------------------------------- {-# INLINE kindView #-} kindView :: Kind -> Maybe Kind --- C.f. coreView, tcView +-- ^ Similar to 'coreView' or 'tcView', but works on 'Kind's + -- For the moment, we don't even handle synonyms in kinds -kindView (NoteTy _ k) = Just k -kindView other = Nothing +kindView _ = Nothing \end{code} @@ -210,6 +319,8 @@ mkTyVarTy = TyVarTy mkTyVarTys :: [TyVar] -> [Type] mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy +-- | Attempts to obtain the type variable underlying a 'Type', and panics with the +-- given message if this is not a type variable type. See also 'getTyVar_maybe' getTyVar :: String -> Type -> TyVar getTyVar msg ty = case getTyVar_maybe ty of Just tv -> tv @@ -218,10 +329,11 @@ getTyVar msg ty = case getTyVar_maybe ty of isTyVarTy :: Type -> Bool isTyVarTy ty = isJust (getTyVar_maybe ty) +-- | Attempts to obtain the type variable underlying a 'Type' getTyVar_maybe :: Type -> Maybe TyVar getTyVar_maybe ty | Just ty' <- coreView ty = getTyVar_maybe ty' getTyVar_maybe (TyVarTy tv) = Just tv -getTyVar_maybe other = Nothing +getTyVar_maybe _ = Nothing \end{code} @@ -234,12 +346,13 @@ invariant that a TyConApp is always visibly so. mkAppTy maintains the invariant: use it. \begin{code} +-- | Applies a type to another, as in e.g. @k a@ +mkAppTy :: Type -> Type -> Type mkAppTy orig_ty1 orig_ty2 = mk_app orig_ty1 where - mk_app (NoteTy _ ty1) = mk_app ty1 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ [orig_ty2]) - mk_app ty1 = AppTy orig_ty1 orig_ty2 + mk_app _ = AppTy orig_ty1 orig_ty2 -- Note that the TyConApp could be an -- under-saturated type synonym. GHC allows that; e.g. -- type Foo k = k a -> k a @@ -259,42 +372,58 @@ mkAppTys orig_ty1 [] = orig_ty1 mkAppTys orig_ty1 orig_tys2 = mk_app orig_ty1 where - mk_app (NoteTy _ ty1) = mk_app ty1 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2) -- mkTyConApp: see notes with mkAppTy - mk_app ty1 = foldl AppTy orig_ty1 orig_tys2 + mk_app _ = foldl AppTy orig_ty1 orig_tys2 ------------- splitAppTy_maybe :: Type -> Maybe (Type, Type) +-- ^ Attempt to take a type application apart, whether it is a +-- function, type constructor, or plain type application. Note +-- that type family applications are NEVER unsaturated by this! splitAppTy_maybe ty | Just ty' <- coreView ty = splitAppTy_maybe ty' splitAppTy_maybe ty = repSplitAppTy_maybe ty ------------- repSplitAppTy_maybe :: Type -> Maybe (Type,Type) --- Does the AppTy split, but assumes that any view stuff is already done +-- ^ Does the AppTy split as in 'splitAppTy_maybe', but assumes that +-- any Core view stuff is already done repSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2) repSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2) -repSplitAppTy_maybe (TyConApp tc tys) = case snocView tys of - Just (tys', ty') -> Just (TyConApp tc tys', ty') - Nothing -> Nothing -repSplitAppTy_maybe other = Nothing +repSplitAppTy_maybe (TyConApp tc tys) + | isDecomposableTyCon tc || length tys > tyConArity tc + = case snocView tys of -- never create unsaturated type family apps + Just (tys', ty') -> Just (TyConApp tc tys', ty') + Nothing -> Nothing +repSplitAppTy_maybe _other = Nothing ------------- splitAppTy :: Type -> (Type, Type) +-- ^ Attempts to take a type application apart, as in 'splitAppTy_maybe', +-- and panics if this is not possible splitAppTy ty = case splitAppTy_maybe ty of Just pr -> pr Nothing -> panic "splitAppTy" ------------- splitAppTys :: Type -> (Type, [Type]) +-- ^ Recursively splits a type as far as is possible, leaving a residual +-- type being applied to and the type arguments applied to it. Never fails, +-- even if that means returning an empty list of type applications. splitAppTys ty = split ty ty [] where split orig_ty ty args | Just ty' <- coreView ty = split orig_ty ty' args - split orig_ty (AppTy ty arg) args = split ty ty (arg:args) - split orig_ty (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args) - split orig_ty (FunTy ty1 ty2) args = ASSERT( null args ) + split _ (AppTy ty arg) args = split ty ty (arg:args) + split _ (TyConApp tc tc_args) args + = let -- keep type families saturated + n | isDecomposableTyCon tc = 0 + | otherwise = tyConArity tc + (tc_args1, tc_args2) = splitAt n tc_args + in + (TyConApp tc tc_args1, tc_args2 ++ args) + split _ (FunTy ty1 ty2) args = ASSERT( null args ) (TyConApp funTyCon [], [ty1,ty2]) - split orig_ty ty args = (orig_ty, args) + split orig_ty _ args = (orig_ty, args) \end{code} @@ -305,66 +434,77 @@ splitAppTys ty = split ty ty [] \begin{code} mkFunTy :: Type -> Type -> Type -mkFunTy arg res = FunTy arg res +-- ^ Creates a function type from the given argument and result type +mkFunTy arg@(PredTy (EqPred {})) res = ForAllTy (mkWildCoVar arg) res +mkFunTy arg res = FunTy arg res mkFunTys :: [Type] -> Type -> Type -mkFunTys tys ty = foldr FunTy ty tys +mkFunTys tys ty = foldr mkFunTy ty tys isFunTy :: Type -> Bool isFunTy ty = isJust (splitFunTy_maybe ty) splitFunTy :: Type -> (Type, Type) +-- ^ Attempts to extract the argument and result types from a type, and +-- panics if that is not possible. See also 'splitFunTy_maybe' splitFunTy ty | Just ty' <- coreView ty = splitFunTy ty' splitFunTy (FunTy arg res) = (arg, res) splitFunTy other = pprPanic "splitFunTy" (ppr other) splitFunTy_maybe :: Type -> Maybe (Type, Type) +-- ^ Attempts to extract the argument and result types from a type splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty' splitFunTy_maybe (FunTy arg res) = Just (arg, res) -splitFunTy_maybe other = Nothing +splitFunTy_maybe _ = Nothing splitFunTys :: Type -> ([Type], Type) splitFunTys ty = split [] ty ty where split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty' - split args orig_ty (FunTy arg res) = split (arg:args) res res - split args orig_ty ty = (reverse args, orig_ty) + split args _ (FunTy arg res) = split (arg:args) res res + split args orig_ty _ = (reverse args, orig_ty) splitFunTysN :: Int -> Type -> ([Type], Type) --- Split off exactly n arg tys +-- ^ Split off exactly the given number argument types, and panics if that is not possible splitFunTysN 0 ty = ([], ty) splitFunTysN n ty = case splitFunTy ty of { (arg, res) -> case splitFunTysN (n-1) res of { (args, res) -> (arg:args, res) }} -zipFunTys :: Outputable a => [a] -> Type -> ([(a,Type)], Type) +-- | Splits off argument types from the given type and associating +-- them with the things in the input list from left to right. The +-- final result type is returned, along with the resulting pairs of +-- objects and types, albeit with the list of pairs in reverse order. +-- Panics if there are not enough argument types for the input list. +zipFunTys :: Outputable a => [a] -> Type -> ([(a, Type)], Type) zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty where - split acc [] nty ty = (reverse acc, nty) + split acc [] nty _ = (reverse acc, nty) split acc xs nty ty | Just ty' <- coreView ty = split acc xs nty ty' - split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res - split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> ppr orig_ty) + split acc (x:xs) _ (FunTy arg res) = split ((x,arg):acc) xs res res + split _ _ _ _ = pprPanic "zipFunTys" (ppr orig_xs <+> ppr orig_ty) funResultTy :: Type -> Type +-- ^ Extract the function result type and panic if that is not possible funResultTy ty | Just ty' <- coreView ty = funResultTy ty' -funResultTy (FunTy arg res) = res -funResultTy ty = pprPanic "funResultTy" (ppr ty) +funResultTy (FunTy _arg res) = res +funResultTy ty = pprPanic "funResultTy" (ppr ty) funArgTy :: Type -> Type +-- ^ Extract the function argument type and panic if that is not possible funArgTy ty | Just ty' <- coreView ty = funArgTy ty' -funArgTy (FunTy arg res) = arg -funArgTy ty = pprPanic "funArgTy" (ppr ty) +funArgTy (FunTy arg _res) = arg +funArgTy ty = pprPanic "funArgTy" (ppr ty) \end{code} - --------------------------------------------------------------------- TyConApp ~~~~~~~~ -@mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy, -as apppropriate. \begin{code} +-- | A key function: builds a 'TyConApp' or 'FunTy' as apppropriate to its arguments. +-- Applies its arguments to the constructor from left to right mkTyConApp :: TyCon -> [Type] -> Type mkTyConApp tycon tys | isFunTyCon tycon, [ty1,ty2] <- tys @@ -373,6 +513,7 @@ mkTyConApp tycon tys | otherwise = TyConApp tycon tys +-- | Create the plain type constructor type which has been applied to no type arguments at all. mkTyConTy :: TyCon -> Type mkTyConTy tycon = mkTyConApp tycon [] @@ -380,42 +521,39 @@ mkTyConTy tycon = mkTyConApp tycon [] -- mean a distinct type, but all other type-constructor applications -- including functions are returned as Just .. +-- | The same as @fst . splitTyConApp@ tyConAppTyCon :: Type -> TyCon tyConAppTyCon ty = fst (splitTyConApp ty) +-- | The same as @snd . splitTyConApp@ tyConAppArgs :: Type -> [Type] tyConAppArgs ty = snd (splitTyConApp ty) +-- | Attempts to tease a type apart into a type constructor and the application +-- of a number of arguments to that constructor. Panics if that is not possible. +-- See also 'splitTyConApp_maybe' splitTyConApp :: Type -> (TyCon, [Type]) splitTyConApp ty = case splitTyConApp_maybe ty of Just stuff -> stuff Nothing -> pprPanic "splitTyConApp" (ppr ty) +-- | Attempts to tease a type apart into a type constructor and the application +-- of a number of arguments to that constructor splitTyConApp_maybe :: Type -> Maybe (TyCon, [Type]) splitTyConApp_maybe ty | Just ty' <- coreView ty = splitTyConApp_maybe ty' splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys) splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res]) -splitTyConApp_maybe other = Nothing +splitTyConApp_maybe _ = Nothing --- Sometimes we do NOT want to look throught a newtype. When case matching --- on a newtype we want a convenient way to access the arguments of a newty --- constructor so as to properly form a coercion. -splitNewTyConApp :: Type -> (TyCon, [Type]) -splitNewTyConApp ty = case splitNewTyConApp_maybe ty of - Just stuff -> stuff - Nothing -> pprPanic "splitNewTyConApp" (ppr ty) -splitNewTyConApp_maybe :: Type -> Maybe (TyCon, [Type]) -splitNewTyConApp_maybe ty | Just ty' <- tcView ty = splitNewTyConApp_maybe ty' -splitNewTyConApp_maybe (TyConApp tc tys) = Just (tc, tys) -splitNewTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res]) -splitNewTyConApp_maybe other = Nothing - --- get instantiated newtype rhs, the arguments had better saturate --- the constructor newTyConInstRhs :: TyCon -> [Type] -> Type -newTyConInstRhs tycon tys = - let (tvs, ty) = newTyConRhs tycon in substTyWith tvs tys ty - +-- ^ Unwrap one 'layer' of newtype on a type constructor and its arguments, using an +-- eta-reduced version of the @newtype@ if possible +newTyConInstRhs tycon tys + = ASSERT2( equalLength tvs tys1, ppr tycon $$ ppr tys $$ ppr tvs ) + mkAppTys (substTyWith tvs tys1 ty) tys2 + where + (tvs, ty) = newTyConEtadRhs tycon + (tys1, tys2) = splitAtList tvs tys \end{code} @@ -438,51 +576,90 @@ The reason is that we then get better (shorter) type signatures in interfaces. Notably this plays a role in tcTySigs in TcBinds.lhs. +Note [Expanding newtypes] +~~~~~~~~~~~~~~~~~~~~~~~~~ +When expanding a type to expose a data-type constructor, we need to be +careful about newtypes, lest we fall into an infinite loop. Here are +the key examples: + + newtype Id x = MkId x + newtype Fix f = MkFix (f (Fix f)) + newtype T = MkT (T -> T) + + Type Expansion + -------------------------- + T T -> T + Fix Maybe Maybe (Fix Maybe) + Id (Id Int) Int + Fix Id NO NO NO + +Notice that we can expand T, even though it's recursive. +And we can expand Id (Id Int), even though the Id shows up +twice at the outer level. + +So, when expanding, we keep track of when we've seen a recursive +newtype at outermost level; and bale out if we see it again. + + Representation types ~~~~~~~~~~~~~~~~~~~~ -repType looks through - (a) for-alls, and - (b) synonyms - (c) predicates - (d) usage annotations - (e) all newtypes, including recursive ones -It's useful in the back end. \begin{code} +-- | Looks through: +-- +-- 1. For-alls +-- 2. Synonyms +-- 3. Predicates +-- 4. All newtypes, including recursive ones, but not newtype families +-- +-- It's useful in the back end of the compiler. repType :: Type -> Type -- Only applied to types of kind *; hence tycons are saturated -repType ty | Just ty' <- coreView ty = repType ty' -repType (ForAllTy _ ty) = repType ty -repType (TyConApp tc tys) - | isNewTyCon tc = -- Recursive newtypes are opaque to coreView - -- but we must expand them here. Sure to - -- be saturated because repType is only applied - -- to types of kind * - ASSERT( {- isRecursiveTyCon tc && -} tys `lengthIs` tyConArity tc ) - repType (new_type_rep tc tys) -repType ty = ty - --- new_type_rep doesn't ask any questions: --- it just expands newtype, whether recursive or not -new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon ) - case newTyConRep new_tycon of - (tvs, rep_ty) -> substTyWith tvs tys rep_ty +repType ty + = go [] ty + where + go :: [TyCon] -> Type -> Type + go rec_nts ty | Just ty' <- coreView ty -- Expand synonyms + = go rec_nts ty' + + go rec_nts (ForAllTy _ ty) -- Look through foralls + = go rec_nts ty + + go rec_nts (TyConApp tc tys) -- Expand newtypes + | Just (rec_nts', ty') <- carefullySplitNewType_maybe rec_nts tc tys + = go rec_nts' ty' + + go _ ty = ty + + +carefullySplitNewType_maybe :: [TyCon] -> TyCon -> [Type] -> Maybe ([TyCon],Type) +-- Return the representation of a newtype, unless +-- we've seen it already: see Note [Expanding newtypes] +carefullySplitNewType_maybe rec_nts tc tys + | isNewTyCon tc + , not (tc `elem` rec_nts) = Just (rec_nts', newTyConInstRhs tc tys) + | otherwise = Nothing + where + rec_nts' | isRecursiveTyCon tc = tc:rec_nts + | otherwise = rec_nts + -- ToDo: this could be moved to the code generator, using splitTyConApp instead -- of inspecting the type directly. + +-- | Discovers the primitive representation of a more abstract 'Type' typePrimRep :: Type -> PrimRep typePrimRep ty = case repType ty of TyConApp tc _ -> tyConPrimRep tc FunTy _ _ -> PtrRep AppTy _ _ -> PtrRep -- See note below TyVarTy _ -> PtrRep - other -> pprPanic "typePrimRep" (ppr ty) + _ -> pprPanic "typePrimRep" (ppr ty) -- Types of the form 'f a' must be of kind *, not *#, so -- we are guaranteed that they are represented by pointers. -- The reason is that f must have kind *->*, not *->*#, because -- (we claim) there is no way to constrain f's kind any other -- way. - \end{code} @@ -493,16 +670,18 @@ typePrimRep ty = case repType ty of \begin{code} mkForAllTy :: TyVar -> Type -> Type mkForAllTy tyvar ty - = mkForAllTys [tyvar] ty + = ForAllTy tyvar ty +-- | Wraps foralls over the type using the provided 'TyVar's from left to right mkForAllTys :: [TyVar] -> Type -> Type mkForAllTys tyvars ty = foldr ForAllTy ty tyvars isForAllTy :: Type -> Bool -isForAllTy (NoteTy _ ty) = isForAllTy ty isForAllTy (ForAllTy _ _) = True -isForAllTy other_ty = False +isForAllTy _ = False +-- | Attempts to take a forall type apart, returning the bound type variable +-- and the remainder of the type splitForAllTy_maybe :: Type -> Maybe (TyVar, Type) splitForAllTy_maybe ty = splitFAT_m ty where @@ -510,13 +689,17 @@ splitForAllTy_maybe ty = splitFAT_m ty splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty) splitFAT_m _ = Nothing +-- | Attempts to take a forall type apart, returning all the immediate such bound +-- type variables and the remainder of the type. Always suceeds, even if that means +-- returning an empty list of 'TyVar's splitForAllTys :: Type -> ([TyVar], Type) splitForAllTys ty = split ty ty [] where split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs - split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs) - split orig_ty t tvs = (reverse tvs, orig_ty) + split _ (ForAllTy tv ty) tvs = split ty ty (tv:tvs) + split orig_ty _ tvs = (reverse tvs, orig_ty) +-- | Equivalent to @snd . splitForAllTys@ dropForAlls :: Type -> Type dropForAlls ty = snd (splitForAllTys ty) \end{code} @@ -525,41 +708,52 @@ dropForAlls ty = snd (splitForAllTys ty) applyTy, applyTys ~~~~~~~~~~~~~~~~~ -Instantiate a for-all type with one or more type arguments. -Used when we have a polymorphic function applied to type args: - f t1 t2 -Then we use (applyTys type-of-f [t1,t2]) to compute the type of -the expression. \begin{code} +-- | Instantiate a forall type with one or more type arguments. +-- Used when we have a polymorphic function applied to type args: +-- +-- > f t1 t2 +-- +-- We use @applyTys type-of-f [t1,t2]@ to compute the type of the expression. +-- Panics if no application is possible. applyTy :: Type -> Type -> Type applyTy ty arg | Just ty' <- coreView ty = applyTy ty' arg applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty -applyTy other arg = panic "applyTy" +applyTy _ _ = panic "applyTy" applyTys :: Type -> [Type] -> Type --- This function is interesting because --- a) the function may have more for-alls than there are args --- b) less obviously, it may have fewer for-alls --- For case (b) think of --- applyTys (forall a.a) [forall b.b, Int] +-- ^ This function is interesting because: +-- +-- 1. The function may have more for-alls than there are args +-- +-- 2. Less obviously, it may have fewer for-alls +-- +-- For case 2. think of: +-- +-- > applyTys (forall a.a) [forall b.b, Int] +-- -- This really can happen, via dressing up polymorphic types with newtype -- clothing. Here's an example: --- newtype R = R (forall a. a->a) --- foo = case undefined :: R of --- R f -> f () +-- +-- > newtype R = R (forall a. a->a) +-- > foo = case undefined :: R of +-- > R f -> f () + +applyTys ty args = applyTysD empty ty args -applyTys orig_fun_ty [] = orig_fun_ty -applyTys orig_fun_ty arg_tys +applyTysD :: SDoc -> Type -> [Type] -> Type -- Debug version +applyTysD _ orig_fun_ty [] = orig_fun_ty +applyTysD doc orig_fun_ty arg_tys | n_tvs == n_args -- The vastly common case = substTyWith tvs arg_tys rho_ty | n_tvs > n_args -- Too many for-alls = substTyWith (take n_args tvs) arg_tys (mkForAllTys (drop n_args tvs) rho_ty) | otherwise -- Too many type args - = ASSERT2( n_tvs > 0, ppr orig_fun_ty ) -- Zero case gives infnite loop! - applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty) - (drop n_tvs arg_tys) + = ASSERT2( n_tvs > 0, doc $$ ppr orig_fun_ty ) -- Zero case gives infnite loop! + applyTysD doc (substTyWith tvs (take n_tvs arg_tys) rho_ty) + (drop n_tvs arg_tys) where (tvs, rho_ty) = splitForAllTys orig_fun_ty n_tvs = length tvs @@ -573,9 +767,6 @@ applyTys orig_fun_ty arg_tys %* * %************************************************************************ -A "source type" is a type that is a separate type as far as the type checker is -concerned, but which has low-level representation as far as the back end is concerned. - Source types are always lifted. The key function is predTypeRep which gives the representation of a source type: @@ -587,93 +778,62 @@ mkPredTy pred = PredTy pred mkPredTys :: ThetaType -> [Type] mkPredTys preds = map PredTy preds +isEqPred :: PredType -> Bool +isEqPred (EqPred _ _) = True +isEqPred _ = False + predTypeRep :: PredType -> Type --- Convert a PredType to its "representation type"; --- the post-type-checking type used by all the Core passes of GHC. --- Unwraps only the outermost level; for example, the result might --- be a newtype application +-- ^ Convert a 'PredType' to its representation type. However, it unwraps +-- only the outermost level; for example, the result might be a newtype application predTypeRep (IParam _ ty) = ty predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys -- Result might be a newtype application, but the consumer will -- look through that too if necessary -\end{code} - - -%************************************************************************ -%* * - NewTypes -%* * -%************************************************************************ - -\begin{code} -splitRecNewType_maybe :: Type -> Maybe Type --- Sometimes we want to look through a recursive newtype, and that's what happens here --- It only strips *one layer* off, so the caller will usually call itself recursively --- Only applied to types of kind *, hence the newtype is always saturated -splitRecNewType_maybe ty | Just ty' <- coreView ty = splitRecNewType_maybe ty' -splitRecNewType_maybe (TyConApp tc tys) - | isNewTyCon tc - = ASSERT( tys `lengthIs` tyConArity tc ) -- splitRecNewType_maybe only be applied - -- to *types* (of kind *) - ASSERT( isRecursiveTyCon tc ) -- Guaranteed by coreView - case newTyConRhs tc of - (tvs, rep_ty) -> ASSERT( length tvs == length tys ) - Just (substTyWith tvs tys rep_ty) - -splitRecNewType_maybe other = Nothing - +predTypeRep (EqPred ty1 ty2) = pprPanic "predTypeRep" (ppr (EqPred ty1 ty2)) +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 fam_subst = zipTopTvSubst (tyConTyVars tc) tys + = mkTyConApp fam_tc (substTys fam_subst fam_tys) + | otherwise + = mkTyConApp tc tys +-- | Pretty prints a 'TyCon', using the family instance in case of a +-- representation tycon. For example: +-- +-- > data T [a] = ... +-- +-- In that case we want to print @T [a]@, where @T@ is the family 'TyCon' +pprSourceTyCon :: TyCon -> SDoc +pprSourceTyCon tycon + | Just (fam_tc, tys) <- tyConFamInst_maybe tycon + = ppr $ fam_tc `TyConApp` tys -- can't be FunTyCon + | otherwise + = ppr tycon \end{code} %************************************************************************ %* * -\subsection{Kinds and free variables} + The free variables of a type %* * %************************************************************************ ---------------------------------------------------------------------- - Finding the kind of a type - ~~~~~~~~~~~~~~~~~~~~~~~~~~ -\begin{code} -typeKind :: Type -> Kind -typeKind (TyConApp tycon tys) = ASSERT( not (isCoercionTyCon tycon) ) - -- We should be looking for the coercion kind, - -- not the type kind - foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys -typeKind (NoteTy _ ty) = typeKind ty -typeKind (PredTy pred) = predKind pred -typeKind (AppTy fun arg) = kindFunResult (typeKind fun) -typeKind (ForAllTy tv ty) = typeKind ty -typeKind (TyVarTy tyvar) = tyVarKind tyvar -typeKind (FunTy arg res) - -- Hack alert. The kind of (Int -> Int#) is liftedTypeKind (*), - -- not unliftedTypKind (#) - -- The only things that can be after a function arrow are - -- (a) types (of kind openTypeKind or its sub-kinds) - -- (b) kinds (of super-kind TY) (e.g. * -> (* -> *)) - | isTySuperKind k = k - | otherwise = ASSERT( isSubOpenTypeKind k) liftedTypeKind - where - k = typeKind res - -predKind :: PredType -> Kind -predKind (EqPred {}) = coSuperKind -- A coercion kind! -predKind (ClassP {}) = liftedTypeKind -- Class and implicitPredicates are -predKind (IParam {}) = liftedTypeKind -- always represented by lifted types -\end{code} - - ---------------------------------------------------------------------- - Free variables of a type - ~~~~~~~~~~~~~~~~~~~~~~~~ \begin{code} tyVarsOfType :: Type -> TyVarSet --- NB: for type synonyms tyVarsOfType does *not* expand the synonym +-- ^ NB: for type synonyms tyVarsOfType does /not/ expand the synonym tyVarsOfType (TyVarTy tv) = unitVarSet tv -tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys -tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs +tyVarsOfType (TyConApp _ tys) = tyVarsOfTypes tys tyVarsOfType (PredTy sty) = tyVarsOfPred sty tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg @@ -689,39 +849,66 @@ tyVarsOfPred (EqPred ty1 ty2) = tyVarsOfType ty1 `unionVarSet` tyVarsOfType ty2 tyVarsOfTheta :: ThetaType -> TyVarSet tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet - --- Add a Note with the free tyvars to the top of the type -addFreeTyVars :: Type -> Type -addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty -addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty \end{code} %************************************************************************ %* * -\subsection{TidyType} +\subsection{Type families} %* * %************************************************************************ -tidyTy tidies up a type for printing in an error message, or in -an interface file. +\begin{code} +-- | Finds type family instances occuring in a type after expanding synonyms. +tyFamInsts :: Type -> [(TyCon, [Type])] +tyFamInsts ty + | Just exp_ty <- tcView ty = tyFamInsts exp_ty +tyFamInsts (TyVarTy _) = [] +tyFamInsts (TyConApp tc tys) + | isOpenSynTyCon tc = [(tc, tys)] + | otherwise = concat (map tyFamInsts tys) +tyFamInsts (FunTy ty1 ty2) = tyFamInsts ty1 ++ tyFamInsts ty2 +tyFamInsts (AppTy ty1 ty2) = tyFamInsts ty1 ++ tyFamInsts ty2 +tyFamInsts (ForAllTy _ ty) = tyFamInsts ty +tyFamInsts (PredTy pty) = predFamInsts pty + +-- | Finds type family instances occuring in a predicate type after expanding +-- synonyms. +predFamInsts :: PredType -> [(TyCon, [Type])] +predFamInsts (ClassP _cla tys) = concat (map tyFamInsts tys) +predFamInsts (IParam _ ty) = tyFamInsts ty +predFamInsts (EqPred ty1 ty2) = tyFamInsts ty1 ++ tyFamInsts ty2 +\end{code} -It doesn't change the uniques at all, just the print names. + +%************************************************************************ +%* * +\subsection{TidyType} +%* * +%************************************************************************ \begin{code} +-- | This tidies up a type for printing in an error message, or in +-- an interface file. +-- +-- It doesn't change the uniques at all, just the print names. tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar) -tidyTyVarBndr (tidy_env, subst) tyvar +tidyTyVarBndr env@(tidy_env, subst) tyvar = case tidyOccName tidy_env (getOccName name) of - (tidy', occ') -> ((tidy', subst'), tyvar') - where - subst' = extendVarEnv subst tyvar tyvar' - tyvar' = setTyVarName tyvar name' - name' = tidyNameOcc name occ' + (tidy', occ') -> ((tidy', subst'), tyvar'') + where + subst' = extendVarEnv subst tyvar tyvar'' + tyvar' = setTyVarName tyvar name' + name' = tidyNameOcc name occ' + -- Don't forget to tidy the kind for coercions! + tyvar'' | isCoVar tyvar = setTyVarKind tyvar' kind' + | otherwise = tyvar' + kind' = tidyType env (tyVarKind tyvar) where name = tyVarName tyvar tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv --- Add the free tyvars to the env in tidy form, +-- ^ Add the free 'TyVar's to the env in tidy form, -- so that we can tidy the type they are free in tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars)) @@ -729,14 +916,16 @@ tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar]) tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar) --- Treat a new tyvar as a binder, and give it a fresh tidy name -tidyOpenTyVar env@(tidy_env, subst) tyvar +-- ^ Treat a new 'TyVar' as a binder, and give it a fresh tidy name +-- using the environment if one has not already been allocated. See +-- also 'tidyTyVarBndr' +tidyOpenTyVar env@(_, subst) tyvar = case lookupVarEnv subst tyvar of Just tyvar' -> (env, tyvar') -- Already substituted Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder tidyType :: TidyEnv -> Type -> Type -tidyType env@(tidy_env, subst) ty +tidyType env@(_, subst) ty = go ty where go (TyVarTy tv) = case lookupVarEnv subst tv of @@ -744,7 +933,6 @@ tidyType env@(tidy_env, subst) ty Just tv' -> TyVarTy tv' go (TyConApp tycon tys) = let args = map go tys in args `seqList` TyConApp tycon args - go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty) go (PredTy sty) = PredTy (tidyPred env sty) go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg) go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg) @@ -752,8 +940,7 @@ tidyType env@(tidy_env, subst) ty where (envp, tvp) = tidyTyVarBndr env tv - go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars - +tidyTypes :: TidyEnv -> [Type] -> [Type] tidyTypes env tys = map (tidyType env) tys tidyPred :: TidyEnv -> PredType -> PredType @@ -763,10 +950,9 @@ tidyPred env (EqPred ty1 ty2) = EqPred (tidyType env ty1) (tidyType env ty2) \end{code} -@tidyOpenType@ grabs the free type variables, tidies them -and then uses @tidyType@ to work over the type itself - \begin{code} +-- | Grabs the free type variables, tidies them +-- and then uses 'tidyType' to work over the type itself tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type) tidyOpenType env ty = (env', tidyType env' ty) @@ -776,6 +962,7 @@ tidyOpenType env ty tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type]) tidyOpenTypes env tys = mapAccumL tidyOpenType env tys +-- | Calls 'tidyType' on a top-level type (i.e. with an empty tidying environment) tidyTopType :: Type -> Type tidyTopType ty = tidyType emptyTidyEnv ty \end{code} @@ -795,6 +982,7 @@ tidyKind env k = tidyOpenType env k %************************************************************************ \begin{code} +-- | See "Type#type_classification" for what an unlifted type is isUnLiftedType :: Type -> Bool -- isUnLiftedType returns True for forall'd unlifted types: -- x :: forall a. Int# @@ -803,60 +991,78 @@ isUnLiftedType :: Type -> Bool -- construct them isUnLiftedType ty | Just ty' <- coreView ty = isUnLiftedType ty' -isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty +isUnLiftedType (ForAllTy _ ty) = isUnLiftedType ty isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc -isUnLiftedType other = False +isUnLiftedType _ = False isUnboxedTupleType :: Type -> Bool isUnboxedTupleType ty = case splitTyConApp_maybe ty of - Just (tc, ty_args) -> isUnboxedTupleTyCon tc - other -> False + Just (tc, _ty_args) -> isUnboxedTupleTyCon tc + _ -> False --- Should only be applied to *types*; hence the assert +-- | 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 +isAlgType ty + = case splitTyConApp_maybe ty of + Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc ) + isAlgTyCon tc + _other -> False + +-- | 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. Closed type constructors are those +-- with a fixed right hand side, as opposed to e.g. associated types +isClosedAlgType :: Type -> Bool +isClosedAlgType ty + = case splitTyConApp_maybe ty of + Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc ) + isAlgTyCon tc && not (isOpenTyCon tc) + _other -> False \end{code} -@isStrictType@ computes whether an argument (or let RHS) should -be computed strictly or lazily, based only on its type. -Works just like isUnLiftedType, except that it has a special case -for dictionaries. Since it takes account of ClassP, you might think -this function should be in TcType, but isStrictType is used by DataCon, -which is below TcType in the hierarchy, so it's convenient to put it here. - \begin{code} +-- | Computes whether an argument (or let right hand side) should +-- be computed strictly or lazily, based only on its type. +-- Works just like 'isUnLiftedType', except that it has a special case +-- for dictionaries (i.e. does not work purely on representation types) + +-- Since it takes account of class 'PredType's, you might think +-- this function should be in 'TcType', but 'isStrictType' is used by 'DataCon', +-- which is below 'TcType' in the hierarchy, so it's convenient to put it here. +isStrictType :: Type -> Bool isStrictType (PredTy pred) = isStrictPred pred isStrictType ty | Just ty' <- coreView ty = isStrictType ty' -isStrictType (ForAllTy tv ty) = isStrictType ty +isStrictType (ForAllTy _ ty) = isStrictType ty isStrictType (TyConApp tc _) = isUnLiftedTyCon tc -isStrictType other = False +isStrictType _ = False +-- | We may be strict in dictionary types, but only if it +-- has more than one component. +-- +-- (Being strict in a single-component dictionary risks +-- poking the dictionary component, which is wrong.) +isStrictPred :: PredType -> Bool isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas)) -isStrictPred other = False - -- We may be strict in dictionary types, but only if it - -- has more than one component. - -- [Being strict in a single-component dictionary risks - -- poking the dictionary component, which is wrong.] +isStrictPred _ = False \end{code} \begin{code} isPrimitiveType :: Type -> Bool --- Returns types that are opaque to Haskell. +-- ^ Returns true of types that are opaque to Haskell. -- Most of these are unlifted, but now that we interact with .NET, we -- may have primtive (foreign-imported) types that are lifted isPrimitiveType ty = case splitTyConApp_maybe ty of Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc ) isPrimTyCon tc - other -> False + _ -> False \end{code} %************************************************************************ %* * -\subsection{Sequencing on types +\subsection{Sequencing on types} %* * %************************************************************************ @@ -865,7 +1071,6 @@ seqType :: Type -> () seqType (TyVarTy tv) = tv `seq` () seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2 -seqType (NoteTy note t2) = seqNote note `seq` seqType t2 seqType (PredTy p) = seqPred p seqType (TyConApp tc tys) = tc `seq` seqTypes tys seqType (ForAllTy tv ty) = tv `seq` seqType ty @@ -874,9 +1079,6 @@ seqTypes :: [Type] -> () seqTypes [] = () seqTypes (ty:tys) = seqType ty `seq` seqTypes tys -seqNote :: TyNote -> () -seqNote (FTVNote set) = sizeUniqSet set `seq` () - seqPred :: PredType -> () seqPred (ClassP c tys) = c `seq` seqTypes tys seqPred (IParam n ty) = n `seq` seqType ty @@ -895,12 +1097,16 @@ Note that eqType works right even for partial applications of newtypes. See Note [Newtype eta] in TyCon.lhs \begin{code} +-- | Type equality test for Core types (i.e. ignores predicate-types, synonyms etc.) coreEqType :: Type -> Type -> Bool -coreEqType t1 t2 - = eq rn_env t1 t2 +coreEqType t1 t2 = coreEqType2 rn_env t1 t2 where rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2)) +coreEqType2 :: RnEnv2 -> Type -> Type -> Bool +coreEqType2 rn_env t1 t2 + = eq rn_env t1 t2 + where eq env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 == rnOccR env tv2 eq env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = eq (rnBndr2 env tv1 tv2) t1 t2 eq env (AppTy s1 t1) (AppTy s2 t2) = eq env s1 s2 && eq env t1 t2 @@ -922,7 +1128,7 @@ coreEqType t1 t2 | Just t2' <- coreView t2 = eq env t1 t2' -- Fall through case; not equal! - eq env t1 t2 = False + eq _ _ _ = False \end{code} @@ -933,18 +1139,18 @@ coreEqType t1 t2 %* * %************************************************************************ -Note that - tcEqType, tcCmpType -do *not* look through newtypes, PredTypes - \begin{code} tcEqType :: Type -> Type -> Bool +-- ^ Type equality on source types. Does not look through @newtypes@ or +-- 'PredType's, but it does look through type synonyms. tcEqType t1 t2 = isEqual $ cmpType t1 t2 tcEqTypes :: [Type] -> [Type] -> Bool tcEqTypes tys1 tys2 = isEqual $ cmpTypes tys1 tys2 tcCmpType :: Type -> Type -> Ordering +-- ^ Type ordering on source types. Does not look through @newtypes@ or +-- 'PredType's, but it does look through type synonyms. tcCmpType t1 t2 = cmpType t1 t2 tcCmpTypes :: [Type] -> [Type] -> Ordering @@ -953,6 +1159,9 @@ tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2 tcEqPred :: PredType -> PredType -> Bool tcEqPred p1 p2 = isEqual $ cmpPred p1 p2 +tcEqPredX :: RnEnv2 -> PredType -> PredType -> Bool +tcEqPredX env p1 p2 = isEqual $ cmpPredX env p1 p2 + tcCmpPred :: PredType -> PredType -> Ordering tcCmpPred p1 p2 = cmpPred p1 p2 @@ -960,6 +1169,27 @@ tcEqTypeX :: RnEnv2 -> Type -> Type -> Bool tcEqTypeX env t1 t2 = isEqual $ cmpTypeX env t1 t2 \end{code} +\begin{code} +-- | Checks whether the second argument is a subterm of the first. (We don't care +-- about binders, as we are only interested in syntactic subterms.) +tcPartOfType :: Type -> Type -> Bool +tcPartOfType t1 t2 + | tcEqType t1 t2 = True +tcPartOfType t1 t2 + | Just t2' <- tcView t2 = tcPartOfType t1 t2' +tcPartOfType _ (TyVarTy _) = False +tcPartOfType t1 (ForAllTy _ t2) = tcPartOfType t1 t2 +tcPartOfType t1 (AppTy s2 t2) = tcPartOfType t1 s2 || tcPartOfType t1 t2 +tcPartOfType t1 (FunTy s2 t2) = tcPartOfType t1 s2 || tcPartOfType t1 t2 +tcPartOfType t1 (PredTy p2) = tcPartOfPred t1 p2 +tcPartOfType t1 (TyConApp _ ts) = any (tcPartOfType t1) ts + +tcPartOfPred :: Type -> PredType -> Bool +tcPartOfPred t1 (IParam _ t2) = tcPartOfType t1 t2 +tcPartOfPred t1 (ClassP _ ts) = any (tcPartOfType t1) ts +tcPartOfPred t1 (EqPred s2 t2) = tcPartOfType t1 s2 || tcPartOfType t1 t2 +\end{code} + Now here comes the real worker \begin{code} @@ -988,43 +1218,49 @@ cmpTypeX env (AppTy s1 t1) (AppTy s2 t2) = cmpTypeX env s1 s2 `thenC cmpTypeX env (FunTy s1 t1) (FunTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2 cmpTypeX env (PredTy p1) (PredTy p2) = cmpPredX env p1 p2 cmpTypeX env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` cmpTypesX env tys1 tys2 -cmpTypeX env t1 (NoteTy _ t2) = cmpTypeX env t1 t2 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < PredTy -cmpTypeX env (AppTy _ _) (TyVarTy _) = GT - -cmpTypeX env (FunTy _ _) (TyVarTy _) = GT -cmpTypeX env (FunTy _ _) (AppTy _ _) = GT - -cmpTypeX env (TyConApp _ _) (TyVarTy _) = GT -cmpTypeX env (TyConApp _ _) (AppTy _ _) = GT -cmpTypeX env (TyConApp _ _) (FunTy _ _) = GT - -cmpTypeX env (ForAllTy _ _) (TyVarTy _) = GT -cmpTypeX env (ForAllTy _ _) (AppTy _ _) = GT -cmpTypeX env (ForAllTy _ _) (FunTy _ _) = GT -cmpTypeX env (ForAllTy _ _) (TyConApp _ _) = GT +cmpTypeX _ (AppTy _ _) (TyVarTy _) = GT + +cmpTypeX _ (FunTy _ _) (TyVarTy _) = GT +cmpTypeX _ (FunTy _ _) (AppTy _ _) = GT + +cmpTypeX _ (TyConApp _ _) (TyVarTy _) = GT +cmpTypeX _ (TyConApp _ _) (AppTy _ _) = GT +cmpTypeX _ (TyConApp _ _) (FunTy _ _) = GT -cmpTypeX env (PredTy _) t2 = GT +cmpTypeX _ (ForAllTy _ _) (TyVarTy _) = GT +cmpTypeX _ (ForAllTy _ _) (AppTy _ _) = GT +cmpTypeX _ (ForAllTy _ _) (FunTy _ _) = GT +cmpTypeX _ (ForAllTy _ _) (TyConApp _ _) = GT -cmpTypeX env _ _ = LT +cmpTypeX _ (PredTy _) _ = GT + +cmpTypeX _ _ _ = LT ------------- cmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering -cmpTypesX env [] [] = EQ +cmpTypesX _ [] [] = EQ cmpTypesX env (t1:tys1) (t2:tys2) = cmpTypeX env t1 t2 `thenCmp` cmpTypesX env tys1 tys2 -cmpTypesX env [] tys = LT -cmpTypesX env ty [] = GT +cmpTypesX _ [] _ = LT +cmpTypesX _ _ [] = GT ------------- cmpPredX :: RnEnv2 -> PredType -> PredType -> Ordering cmpPredX env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` cmpTypeX env ty1 ty2 - -- Compare types as well as names for implicit parameters - -- This comparison is used exclusively (I think) for the - -- finite map built in TcSimplify -cmpPredX env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` cmpTypesX env tys1 tys2 -cmpPredX env (IParam _ _) (ClassP _ _) = LT -cmpPredX env (ClassP _ _) (IParam _ _) = GT + -- Compare names only for implicit parameters + -- This comparison is used exclusively (I believe) + -- for the Avails finite map built in TcSimplify + -- If the types differ we keep them distinct so that we see + -- a distinct pair to run improvement on +cmpPredX env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTypesX env tys1 tys2) +cmpPredX env (EqPred ty1 ty2) (EqPred ty1' ty2') = (cmpTypeX env ty1 ty1') `thenCmp` (cmpTypeX env ty2 ty2') + +-- Constructor order: IParam < ClassP < EqPred +cmpPredX _ (IParam {}) _ = LT +cmpPredX _ (ClassP {}) (IParam {}) = GT +cmpPredX _ (ClassP {}) (EqPred {}) = LT +cmpPredX _ (EqPred {}) _ = GT \end{code} PredTypes are used as a FM key in TcSimplify, @@ -1043,14 +1279,29 @@ instance Ord PredType where { compare = tcCmpPred } %************************************************************************ \begin{code} +-- | Type substitution +-- +-- #tvsubst_invariant# +-- The following invariants must hold of a 'TvSubst': +-- +-- 1. The in-scope set is needed /only/ to +-- guide the generation of fresh uniques +-- +-- 2. In particular, the /kind/ of the type variables in +-- the in-scope set is not relevant +-- +-- 3. The substition is only applied ONCE! This is because +-- in general such application will not reached a fixed point. data TvSubst = TvSubst InScopeSet -- The in-scope type variables TvSubstEnv -- The substitution itself - -- See Note [Apply Once] + -- See Note [Apply Once] + -- and Note [Extending the TvSubstEnv] {- ---------------------------------------------------------- - Note [Apply Once] +Note [Apply Once] +~~~~~~~~~~~~~~~~~ We use TvSubsts to instantiate things, and we might instantiate forall a b. ty \with the types @@ -1067,22 +1318,49 @@ variations happen to; for example [a -> (a, b)]. A TvSubst is not idempotent, but, unlike the non-idempotent substitution we use during unifications, it must not be repeatedly applied. --------------------------------------------------------------- -} +Note [Extending the TvSubst] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +See #tvsubst_invariant# for the invariants that must hold. + +This invariant allows a short-cut when the TvSubstEnv is empty: +if the TvSubstEnv is empty --- i.e. (isEmptyTvSubt subst) holds --- +then (substTy subst ty) does nothing. + +For example, consider: + (/\a. /\b:(a~Int). ...b..) Int +We substitute Int for 'a'. The Unique of 'b' does not change, but +nevertheless we add 'b' to the TvSubstEnv, because b's type does change + +This invariant has several crucial consequences: + +* In substTyVarBndr, we need extend the TvSubstEnv + - if the unique has changed + - or if the kind has changed + +* In substTyVar, we do not need to consult the in-scope set; + the TvSubstEnv is enough + +* In substTy, substTheta, we can short-circuit when the TvSubstEnv is empty + +-------------------------------------------------------------- -} + +-- | A substitition of 'Type's for 'TyVar's type TvSubstEnv = TyVarEnv Type -- A TvSubstEnv is used both inside a TvSubst (with the apply-once -- invariant discussed in Note [Apply Once]), and also independently -- in the middle of matching, and unification (see Types.Unify) -- So you have to look at the context to know if it's idempotent or -- apply-once or whatever + emptyTvSubstEnv :: TvSubstEnv emptyTvSubstEnv = emptyVarEnv composeTvSubst :: InScopeSet -> TvSubstEnv -> TvSubstEnv -> TvSubstEnv --- (compose env1 env2)(x) is env1(env2(x)); i.e. apply env2 then env1 --- It assumes that both are idempotent --- Typically, env1 is the refinement to a base substitution env2 +-- ^ @(compose env1 env2)(x)@ is @env1(env2(x))@; i.e. apply @env2@ then @env1@. +-- It assumes that both are idempotent. +-- Typically, @env1@ is the refinement to a base substitution @env2@ composeTvSubst in_scope env1 env2 = env1 `plusVarEnv` mapVarEnv (substTy subst1) env2 -- First apply env1 to the range of env2 @@ -1092,9 +1370,11 @@ composeTvSubst in_scope env1 env2 where subst1 = TvSubst in_scope env1 +emptyTvSubst :: TvSubst emptyTvSubst = TvSubst emptyInScopeSet emptyVarEnv isEmptyTvSubst :: TvSubst -> Bool + -- See Note [Extending the TvSubstEnv] isEmptyTvSubst (TvSubst _ env) = isEmptyVarEnv env mkTvSubst :: InScopeSet -> TvSubstEnv -> TvSubst @@ -1115,8 +1395,14 @@ notElemTvSubst tv (TvSubst _ env) = not (tv `elemVarEnv` env) setTvSubstEnv :: TvSubst -> TvSubstEnv -> TvSubst setTvSubstEnv (TvSubst in_scope _) env = TvSubst in_scope env -extendTvInScope :: TvSubst -> [Var] -> TvSubst -extendTvInScope (TvSubst in_scope env) vars = TvSubst (extendInScopeSetList in_scope vars) env +zapTvSubstEnv :: TvSubst -> TvSubst +zapTvSubstEnv (TvSubst in_scope _) = TvSubst in_scope emptyVarEnv + +extendTvInScope :: TvSubst -> Var -> TvSubst +extendTvInScope (TvSubst in_scope env) var = TvSubst (extendInScopeSet in_scope var) env + +extendTvInScopeList :: TvSubst -> [Var] -> TvSubst +extendTvInScopeList (TvSubst in_scope env) vars = TvSubst (extendInScopeSetList in_scope vars) env extendTvSubst :: TvSubst -> TyVar -> Type -> TvSubst extendTvSubst (TvSubst in_scope env) tv ty = TvSubst in_scope (extendVarEnv env tv ty) @@ -1129,44 +1415,55 @@ extendTvSubstList (TvSubst in_scope env) tvs tys -- the types given; but it's just a thunk so with a bit of luck -- it'll never be evaluated +-- Note [Generating the in-scope set for a substitution] +-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +-- If we want to substitute [a -> ty1, b -> ty2] I used to +-- think it was enough to generate an in-scope set that includes +-- fv(ty1,ty2). But that's not enough; we really should also take the +-- free vars of the type we are substituting into! Example: +-- (forall b. (a,b,x)) [a -> List b] +-- Then if we use the in-scope set {b}, there is a danger we will rename +-- the forall'd variable to 'x' by mistake, getting this: +-- (forall x. (List b, x, x) +-- Urk! This means looking at all the calls to mkOpenTvSubst.... + + +-- | Generates the in-scope set for the 'TvSubst' from the types in the incoming +-- environment, hence "open" mkOpenTvSubst :: TvSubstEnv -> TvSubst mkOpenTvSubst env = TvSubst (mkInScopeSet (tyVarsOfTypes (varEnvElts env))) env +-- | Generates the in-scope set for the 'TvSubst' from the types in the incoming +-- environment, hence "open" zipOpenTvSubst :: [TyVar] -> [Type] -> TvSubst zipOpenTvSubst tyvars tys -#ifdef DEBUG - | length tyvars /= length tys + | debugIsOn && (length tyvars /= length tys) = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst | otherwise -#endif = TvSubst (mkInScopeSet (tyVarsOfTypes tys)) (zipTyEnv tyvars tys) --- mkTopTvSubst is called when doing top-level substitutions. --- Here we expect that the free vars of the range of the --- substitution will be empty. +-- | Called when doing top-level substitutions. Here we expect that the +-- free vars of the range of the substitution will be empty. mkTopTvSubst :: [(TyVar, Type)] -> TvSubst mkTopTvSubst prs = TvSubst emptyInScopeSet (mkVarEnv prs) zipTopTvSubst :: [TyVar] -> [Type] -> TvSubst zipTopTvSubst tyvars tys -#ifdef DEBUG - | length tyvars /= length tys - = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst + | debugIsOn && (length tyvars /= length tys) + = pprTrace "zipTopTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst | otherwise -#endif = TvSubst emptyInScopeSet (zipTyEnv tyvars tys) zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv zipTyEnv tyvars tys -#ifdef DEBUG - | length tyvars /= length tys + | debugIsOn && (length tyvars /= length tys) = pprTrace "mkTopTvSubst" (ppr tyvars $$ ppr tys) emptyVarEnv | otherwise -#endif = zip_ty_env tyvars tys emptyVarEnv -- Later substitutions in the list over-ride earlier ones, -- but there should be no loops +zip_ty_env :: [TyVar] -> [Type] -> TvSubstEnv -> TvSubstEnv zip_ty_env [] [] env = env zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendVarEnv env tv ty) -- There used to be a special case for when @@ -1186,9 +1483,9 @@ zip_ty_env tvs tys env = pprTrace "Var/Type length mismatch: " (ppr instance Outputable TvSubst where ppr (TvSubst ins env) - = brackets $ sep[ ptext SLIT("TvSubst"), - nest 2 (ptext SLIT("In scope:") <+> ppr ins), - nest 2 (ptext SLIT("Env:") <+> ppr env) ] + = brackets $ sep[ ptext (sLit "TvSubst"), + nest 2 (ptext (sLit "In scope:") <+> ppr ins), + nest 2 (ptext (sLit "Env:") <+> ppr env) ] \end{code} %************************************************************************ @@ -1198,29 +1495,42 @@ instance Outputable TvSubst where %************************************************************************ \begin{code} +-- | Type substitution making use of an 'TvSubst' that +-- is assumed to be open, see 'zipOpenTvSubst' substTyWith :: [TyVar] -> [Type] -> Type -> Type substTyWith tvs tys = ASSERT( length tvs == length tys ) substTy (zipOpenTvSubst tvs tys) +-- | Type substitution making use of an 'TvSubst' that +-- is assumed to be open, see 'zipOpenTvSubst' +substTysWith :: [TyVar] -> [Type] -> [Type] -> [Type] +substTysWith tvs tys = ASSERT( length tvs == length tys ) + substTys (zipOpenTvSubst tvs tys) + +-- | Substitute within a 'Type' substTy :: TvSubst -> Type -> Type substTy subst ty | isEmptyTvSubst subst = ty | otherwise = subst_ty subst ty +-- | Substitute within several 'Type's substTys :: TvSubst -> [Type] -> [Type] substTys subst tys | isEmptyTvSubst subst = tys | otherwise = map (subst_ty subst) tys +-- | Substitute within a 'ThetaType' substTheta :: TvSubst -> ThetaType -> ThetaType substTheta subst theta | isEmptyTvSubst subst = theta | otherwise = map (substPred subst) theta +-- | Substitute within a 'PredType' substPred :: TvSubst -> PredType -> PredType substPred subst (IParam n ty) = IParam n (subst_ty subst ty) substPred subst (ClassP clas tys) = ClassP clas (map (subst_ty subst) tys) substPred subst (EqPred ty1 ty2) = EqPred (subst_ty subst ty1) (subst_ty subst ty2) -deShadowTy :: TyVarSet -> Type -> Type -- Remove any nested binders mentioning tvs +-- | Remove any nested binders mentioning the 'TyVar's in the 'TyVarSet' +deShadowTy :: TyVarSet -> Type -> Type deShadowTy tvs ty = subst_ty (mkTvSubst in_scope emptyTvSubstEnv) ty where @@ -1234,36 +1544,40 @@ subst_ty :: TvSubst -> Type -> Type subst_ty subst ty = go ty where - go (TyVarTy tv) = substTyVar subst tv - go (TyConApp tc tys) = let args = map go tys - in args `seqList` TyConApp tc args + go (TyVarTy tv) = substTyVar subst tv + go (TyConApp tc tys) = let args = map go tys + in args `seqList` TyConApp tc args - go (PredTy p) = PredTy $! (substPred subst p) + go (PredTy p) = PredTy $! (substPred subst p) - go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard the free tyvar note - - go (FunTy arg res) = (FunTy $! (go arg)) $! (go res) - go (AppTy fun arg) = mkAppTy (go fun) $! (go arg) - -- The mkAppTy smart constructor is important - -- we might be replacing (a Int), represented with App - -- by [Int], represented with TyConApp - go (ForAllTy tv ty) = case substTyVarBndr subst tv of - (subst', tv') -> ForAllTy tv' $! (subst_ty subst' ty) + go (FunTy arg res) = (FunTy $! (go arg)) $! (go res) + go (AppTy fun arg) = mkAppTy (go fun) $! (go arg) + -- The mkAppTy smart constructor is important + -- we might be replacing (a Int), represented with App + -- by [Int], represented with TyConApp + go (ForAllTy tv ty) = case substTyVarBndr subst tv of + (subst', tv') -> + ForAllTy tv' $! (subst_ty subst' ty) substTyVar :: TvSubst -> TyVar -> Type -substTyVar subst@(TvSubst in_scope env) tv +substTyVar subst@(TvSubst _ _) tv = case lookupTyVar subst tv of { - Nothing -> TyVarTy tv; + Nothing -> TyVarTy tv; Just ty -> ty -- See Note [Apply Once] } +substTyVars :: TvSubst -> [TyVar] -> [Type] +substTyVars subst tvs = map (substTyVar subst) tvs + lookupTyVar :: TvSubst -> TyVar -> Maybe Type -lookupTyVar (TvSubst in_scope env) tv = lookupVarEnv env tv + -- See Note [Extending the TvSubst] +lookupTyVar (TvSubst _ env) tv = lookupVarEnv env tv substTyVarBndr :: TvSubst -> TyVar -> (TvSubst, TyVar) substTyVarBndr subst@(TvSubst in_scope env) old_var = (TvSubst (in_scope `extendInScopeSet` new_var) new_env, new_var) where + is_co_var = isCoVar old_var new_env | no_change = delVarEnv env old_var | otherwise = extendVarEnv env old_var (TyVarTy new_var) @@ -1271,6 +1585,7 @@ substTyVarBndr subst@(TvSubst in_scope env) old_var no_change = new_var == old_var && not is_co_var -- no_change means that the new_var is identical in -- all respects to the old_var (same unique, same kind) + -- See Note [Extending the TvSubst] -- -- In that case we don't need to extend the substitution -- to map old to new. But instead we must zap any @@ -1282,12 +1597,10 @@ substTyVarBndr subst@(TvSubst in_scope env) old_var -- The uniqAway part makes sure the new variable is not already in scope subst_old_var -- subst_old_var is old_var with the substitution applied to its kind - -- It's only worth doing the substitution for coercions, - -- becuase only they can have free type variables - | is_co_var = setTyVarKind old_var (substTy subst kind) + -- It's only worth doing the substitution for coercions, + -- becuase only they can have free type variables + | is_co_var = setTyVarKind old_var (substTy subst (tyVarKind old_var)) | otherwise = old_var - kind = tyVarKind old_var - is_co_var = isCoercionKind kind \end{code} ---------------------------------------------------- @@ -1295,28 +1608,35 @@ substTyVarBndr subst@(TvSubst in_scope env) old_var Kinds ~~~~~ -There's a little subtyping at the kind level: - - ? - / \ - / \ - ?? (#) - / \ - * # - -where * [LiftedTypeKind] means boxed type - # [UnliftedTypeKind] means unboxed type - (#) [UbxTupleKind] means unboxed tuple - ?? [ArgTypeKind] is the lub of *,# - ? [OpenTypeKind] means any type at all - -In particular: - - error :: forall a:?. String -> a - (->) :: ?? -> ? -> * - (\(x::t) -> ...) Here t::?? (i.e. not unboxed tuple) \begin{code} +-- $kind_subtyping +-- #kind_subtyping# +-- There's a little subtyping at the kind level: +-- +-- @ +-- ? +-- \/ \ +-- \/ \ +-- ?? (\#) +-- \/ \ +-- \* \# +-- . +-- Where: \* [LiftedTypeKind] means boxed type +-- \# [UnliftedTypeKind] means unboxed type +-- (\#) [UbxTupleKind] means unboxed tuple +-- ?? [ArgTypeKind] is the lub of {\*, \#} +-- ? [OpenTypeKind] means any type at all +-- @ +-- +-- In particular: +-- +-- > error :: forall a:?. String -> a +-- > (->) :: ?? -> ? -> \* +-- > (\\(x::t) -> ...) +-- +-- Where in the last example @t :: ??@ (i.e. is not an unboxed tuple) + type KindVar = TyVar -- invariant: KindVar will always be a -- TcTyVar with details MetaTv TauTv ... -- kind var constructors and functions are in TcType @@ -1347,122 +1667,3 @@ When unifying two internal type variables, we collect their kind constraints by finding the GLB of the two. Since the partial order is a tree, they only have a glb if one is a sub-kind of the other. In that case, we bind the less-informative one to the more informative one. Neat, eh? - - -\begin{code} - -\end{code} - -%************************************************************************ -%* * - Functions over Kinds -%* * -%************************************************************************ - -\begin{code} -kindFunResult :: Kind -> Kind -kindFunResult k = funResultTy k - -splitKindFunTys :: Kind -> ([Kind],Kind) -splitKindFunTys k = splitFunTys k - -isUbxTupleKind, isOpenTypeKind, isArgTypeKind, isUnliftedTypeKind :: Kind -> Bool - -isOpenTypeKindCon tc = tyConUnique tc == openTypeKindTyConKey - -isOpenTypeKind (TyConApp tc _) = isOpenTypeKindCon tc -isOpenTypeKind other = False - -isUbxTupleKindCon tc = tyConUnique tc == ubxTupleKindTyConKey - -isUbxTupleKind (TyConApp tc _) = isUbxTupleKindCon tc -isUbxTupleKind other = False - -isArgTypeKindCon tc = tyConUnique tc == argTypeKindTyConKey - -isArgTypeKind (TyConApp tc _) = isArgTypeKindCon tc -isArgTypeKind other = False - -isUnliftedTypeKindCon tc = tyConUnique tc == unliftedTypeKindTyConKey - -isUnliftedTypeKind (TyConApp tc _) = isUnliftedTypeKindCon tc -isUnliftedTypeKind other = False - -isSubOpenTypeKind :: Kind -> Bool --- True of any sub-kind of OpenTypeKind (i.e. anything except arrow) -isSubOpenTypeKind (FunTy k1 k2) = ASSERT2 ( isKind k1, text "isSubOpenTypeKind" <+> ppr k1 <+> text "::" <+> ppr (typeKind k1) ) - ASSERT2 ( isKind k2, text "isSubOpenTypeKind" <+> ppr k2 <+> text "::" <+> ppr (typeKind k2) ) - False -isSubOpenTypeKind (TyConApp kc []) = ASSERT( isKind (TyConApp kc []) ) True -isSubOpenTypeKind other = ASSERT( isKind other ) False - -- This is a conservative answer - -- It matters in the call to isSubKind in - -- checkExpectedKind. - -isSubArgTypeKindCon kc - | isUnliftedTypeKindCon kc = True - | isLiftedTypeKindCon kc = True - | isArgTypeKindCon kc = True - | otherwise = False - -isSubArgTypeKind :: Kind -> Bool --- True of any sub-kind of ArgTypeKind -isSubArgTypeKind (TyConApp kc []) = isSubArgTypeKindCon kc -isSubArgTypeKind other = False - -isSuperKind :: Type -> Bool -isSuperKind (TyConApp (skc) []) = isSuperKindTyCon skc -isSuperKind other = False - -isKind :: Kind -> Bool -isKind k = isSuperKind (typeKind k) - - - -isSubKind :: Kind -> Kind -> Bool --- (k1 `isSubKind` k2) checks that k1 <: k2 -isSubKind (TyConApp kc1 []) (TyConApp kc2 []) = kc1 `isSubKindCon` kc1 -isSubKind (FunTy a1 r1) (FunTy a2 r2) = (a2 `isSubKind` a1) && (r1 `isSubKind` r2) -isSubKind k1 k2 = False - -eqKind :: Kind -> Kind -> Bool -eqKind = tcEqType - -isSubKindCon :: TyCon -> TyCon -> Bool --- (kc1 `isSubKindCon` kc2) checks that kc1 <: kc2 -isSubKindCon kc1 kc2 - | isLiftedTypeKindCon kc1 && isLiftedTypeKindCon kc2 = True - | isUnliftedTypeKindCon kc1 && isUnliftedTypeKindCon kc2 = True - | isUbxTupleKindCon kc1 && isUbxTupleKindCon kc2 = True - | isOpenTypeKindCon kc2 = True - -- we already know kc1 is not a fun, its a TyCon - | isArgTypeKindCon kc2 && isSubArgTypeKindCon kc1 = True - | otherwise = False - -defaultKind :: Kind -> Kind --- Used when generalising: default kind '?' and '??' to '*' --- --- When we generalise, we make generic type variables whose kind is --- simple (* or *->* etc). So generic type variables (other than --- built-in constants like 'error') always have simple kinds. This is important; --- consider --- f x = True --- We want f to get type --- f :: forall (a::*). a -> Bool --- Not --- f :: forall (a::??). a -> Bool --- because that would allow a call like (f 3#) as well as (f True), ---and the calling conventions differ. This defaulting is done in TcMType.zonkTcTyVarBndr. -defaultKind k - | isSubOpenTypeKind k = liftedTypeKind - | isSubArgTypeKind k = liftedTypeKind - | otherwise = k - -isCoercionKind :: Kind -> Bool --- All coercions are of form (ty1 :=: ty2) --- This function is here rather than in Coercion, --- because it's used by substTy -isCoercionKind k | Just k' <- kindView k = isCoercionKind k' -isCoercionKind (PredTy (EqPred {})) = True -isCoercionKind other = False -\end{code}