+%
+% (c) The GRASP/AQUA Project, Glasgow University, 1998
+%
+\section[Type]{Type - public interface}
+
\begin{code}
module Type (
- GenType(..), Type,
+ -- re-exports from TypeRep
+ TyThing(..), Type, PredType(..), ThetaType,
+ funTyCon,
+
+ -- Re-exports from Kind
+ module Kind,
+
+ -- Re-exports from TyCon
+ PrimRep(..),
mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy,
- mkAppTy, mkAppTys, splitAppTy, splitAppTys,
+ mkAppTy, mkAppTys, splitAppTy, splitAppTys, splitAppTy_maybe,
+
+ mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe,
+ splitFunTys, splitFunTysN,
+ funResultTy, funArgTy, zipFunTys, isFunTy,
+
+ mkTyConApp, mkTyConTy,
+ tyConAppTyCon, tyConAppArgs,
+ splitTyConApp_maybe, splitTyConApp,
- mkFunTy, mkFunTys, splitFunTy_maybe, splitFunTys,
+ repType, typePrimRep, coreView, tcView,
- mkTyConApp, mkTyConTy, splitTyConApp_maybe,
- splitAlgTyConApp_maybe, splitAlgTyConApp,
- mkDictTy, splitDictTy_maybe, isDictTy,
+ mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys,
+ applyTy, applyTys, isForAllTy, dropForAlls,
- mkSynTy, isSynTy,
+ -- Source types
+ predTypeRep, mkPredTy, mkPredTys,
- mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys, applyTy,
+ -- Newtypes
+ splitRecNewType_maybe,
- TauType, RhoType, SigmaType, ThetaType,
- isTauTy,
- mkRhoTy, splitRhoTy,
- mkSigmaTy, splitSigmaTy,
+ -- Lifting and boxity
+ isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType,
+ isStrictType, isStrictPred,
- isUnpointedType, isUnboxedType, typePrimRep,
+ -- Free variables
+ tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
+ typeKind, addFreeTyVars,
- matchTy, matchTys,
+ -- Tidying up for printing
+ tidyType, tidyTypes,
+ tidyOpenType, tidyOpenTypes,
+ tidyTyVarBndr, tidyFreeTyVars,
+ tidyOpenTyVar, tidyOpenTyVars,
+ tidyTopType, tidyPred,
+ tidyKind,
- tyVarsOfType, tyVarsOfTypes, namesOfType, typeKind,
+ -- Comparison
+ coreEqType, tcEqType, tcEqTypes, tcCmpType, tcCmpTypes,
+ tcEqPred, tcCmpPred, tcEqTypeX,
- instantiateTy, instantiateTauTy, instantiateThetaTy,
+ -- Seq
+ seqType, seqTypes,
- showTypeCategory
+ -- Type substitutions
+ TvSubstEnv, emptyTvSubstEnv, -- Representation widely visible
+ TvSubst(..), emptyTvSubst, -- Representation visible to a few friends
+ mkTvSubst, mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
+ getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope,
+ extendTvSubst, extendTvSubstList, isInScope, composeTvSubst, zipTyEnv,
+
+ -- Performing substitution on types
+ substTy, substTys, substTyWith, substTheta,
+ substPred, substTyVar, substTyVarBndr, deShadowTy, lookupTyVar,
+
+ -- Pretty-printing
+ pprType, pprParendType, pprTyThingCategory,
+ pprPred, pprTheta, pprThetaArrow, pprClassPred
) where
#include "HsVersions.h"
-import {-# SOURCE #-} Id ( Id )
+-- We import the representation and primitive functions from TypeRep.
+-- Many things are reexported, but not the representation!
+
+import TypeRep
-- friends:
-import Class ( classTyCon, Class )
-import Kind ( mkBoxedTypeKind, resultKind, Kind )
-import TyCon ( mkFunTyCon, isFunTyCon, isEnumerationTyCon, isTupleTyCon, maybeTyConSingleCon,
- isPrimTyCon, isAlgTyCon, isSynTyCon, tyConArity,
- tyConKind, tyConDataCons, getSynTyConDefn,
- tyConPrimRep, tyConClass_maybe, TyCon )
-import TyVar ( GenTyVarSet, TyVarEnv, GenTyVar, TyVar,
- tyVarKind, emptyTyVarSet, unionTyVarSets, minusTyVarSet,
- unitTyVarSet, lookupTyVarEnv, delFromTyVarEnv, zipTyVarEnv, mkTyVarEnv,
- emptyTyVarEnv, isEmptyTyVarEnv, addToTyVarEnv )
-import Name ( NamedThing(..),
- NameSet(..), unionNameSets, emptyNameSet, unitNameSet, minusNameSet
+import Kind
+import Var ( Var, TyVar, tyVarKind, tyVarName, setTyVarName, mkTyVar )
+import VarEnv
+import VarSet
+
+import OccName ( tidyOccName )
+import Name ( NamedThing(..), mkInternalName, tidyNameOcc )
+import Class ( Class, classTyCon )
+import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon,
+ isUnboxedTupleTyCon, isUnLiftedTyCon,
+ isFunTyCon, isNewTyCon, newTyConRep, newTyConRhs,
+ isAlgTyCon, tyConArity,
+ tcExpandTyCon_maybe, coreExpandTyCon_maybe,
+ tyConKind, PrimRep(..), tyConPrimRep,
)
-- others
-import BasicTypes ( Unused )
-import Maybes ( maybeToBool, assocMaybe )
-import PrimRep ( PrimRep(..) )
-import Unique -- quite a few *Keys
-import Util ( thenCmp, zipEqual, zipWithEqual, assoc )
+import StaticFlags ( opt_DictsStrict )
+import SrcLoc ( noSrcLoc )
+import Util ( mapAccumL, seqList, lengthIs, snocView, thenCmp, isEqual, all2 )
import Outputable
+import UniqSet ( sizeUniqSet ) -- Should come via VarSet
+import Maybe ( isJust )
\end{code}
-
%************************************************************************
%* *
-\subsection{The data type}
+ Type representation
%* *
%************************************************************************
+In Core, we "look through" non-recursive newtypes and PredTypes.
\begin{code}
-type Type = GenType Unused -- Used after typechecker
-
-data GenType flexi -- Parameterised over the "flexi" part of a type variable
- = TyVarTy (GenTyVar flexi)
-
- | AppTy
- (GenType flexi) -- Function is *not* a TyConApp
- (GenType flexi)
-
- | TyConApp -- Application of a TyCon
- TyCon -- *Invariant* saturated appliations of FunTyCon and
- -- synonyms have their own constructors, below.
- [GenType flexi] -- Might not be saturated.
-
- | FunTy -- Special case of TyConApp: TyConApp FunTyCon [t1,t2]
- (GenType flexi)
- (GenType flexi)
-
- | SynTy -- Saturated application of a type synonym
- (GenType flexi) -- The unexpanded version; always a TyConTy
- (GenType flexi) -- The expanded version
-
- | ForAllTy
- (GenTyVar flexi)
- (GenType flexi) -- TypeKind
+{-# INLINE coreView #-}
+coreView :: Type -> Maybe Type
+-- Srips 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
+--
+-- 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)
+
+-- 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 (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
+
+-----------------------------------------------
+{-# INLINE tcView #-}
+tcView :: Type -> Maybe Type
+-- Same, but for the type checker, which just looks through synonyms
+tcView (NoteTy _ ty) = Just ty
+tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- tcExpandTyCon_maybe tc tys
+ = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys')
+tcView ty = Nothing
\end{code}
TyVarTy
~~~~~~~
\begin{code}
-mkTyVarTy :: GenTyVar flexi -> GenType flexi
+mkTyVarTy :: TyVar -> Type
mkTyVarTy = TyVarTy
-mkTyVarTys :: [GenTyVar flexi] -> [GenType flexi]
+mkTyVarTys :: [TyVar] -> [Type]
mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy
-getTyVar :: String -> GenType flexi -> GenTyVar flexi
-getTyVar msg (TyVarTy tv) = tv
-getTyVar msg (SynTy _ t) = getTyVar msg t
-getTyVar msg other = panic ("getTyVar: " ++ msg)
+getTyVar :: String -> Type -> TyVar
+getTyVar msg ty = case getTyVar_maybe ty of
+ Just tv -> tv
+ Nothing -> panic ("getTyVar: " ++ msg)
-getTyVar_maybe :: GenType flexi -> Maybe (GenTyVar flexi)
-getTyVar_maybe (TyVarTy tv) = Just tv
-getTyVar_maybe (SynTy _ t) = getTyVar_maybe t
-getTyVar_maybe other = Nothing
+isTyVarTy :: Type -> Bool
+isTyVarTy ty = isJust (getTyVar_maybe ty)
-isTyVarTy :: GenType flexi -> Bool
-isTyVarTy (TyVarTy tv) = True
-isTyVarTy (SynTy _ ty) = isTyVarTy ty
-isTyVarTy other = False
+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
\end{code}
invariant: use it.
\begin{code}
-mkAppTy orig_ty1 orig_ty2 = mk_app orig_ty1
+mkAppTy orig_ty1 orig_ty2
+ = mk_app orig_ty1
where
- mk_app (SynTy _ ty1) = mk_app ty1
+ 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
-
-mkAppTys :: GenType flexi -> [GenType flexi] -> GenType flexi
+ -- Note that the TyConApp could be an
+ -- under-saturated type synonym. GHC allows that; e.g.
+ -- type Foo k = k a -> k a
+ -- type Id x = x
+ -- foo :: Foo Id -> Foo Id
+ --
+ -- Here Id is partially applied in the type sig for Foo,
+ -- but once the type synonyms are expanded all is well
+
+mkAppTys :: Type -> [Type] -> Type
mkAppTys orig_ty1 [] = orig_ty1
-- This check for an empty list of type arguments
- -- avoids the needless of a type synonym constructor.
+ -- avoids the needless loss of a type synonym constructor.
-- For example: mkAppTys Rational []
-- returns to (Ratio Integer), which has needlessly lost
-- the Rational part.
-mkAppTys orig_ty1 orig_tys2 = mk_app orig_ty1
+mkAppTys orig_ty1 orig_tys2
+ = mk_app orig_ty1
where
- mk_app (SynTy _ ty1) = mk_app ty1
+ 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
-splitAppTy :: GenType flexi -> (GenType flexi, GenType flexi)
-splitAppTy (FunTy ty1 ty2) = (TyConApp mkFunTyCon [ty1], ty2)
-splitAppTy (AppTy ty1 ty2) = (ty1, ty2)
-splitAppTy (SynTy _ ty) = splitAppTy ty
-splitAppTy (TyConApp tc tys) = split tys []
- where
- split [ty2] acc = (TyConApp tc (reverse acc), ty2)
- split (ty:tys) acc = split tys (ty:acc)
-splitAppTy other = panic "splitAppTy"
-
-splitAppTys :: GenType flexi -> (GenType flexi, [GenType flexi])
+splitAppTy_maybe :: Type -> Maybe (Type, Type)
+splitAppTy_maybe ty | Just ty' <- coreView ty = splitAppTy_maybe ty'
+splitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
+splitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
+splitAppTy_maybe (TyConApp tc tys) = case snocView tys of
+ Nothing -> Nothing
+ Just (tys',ty') -> Just (TyConApp tc tys', ty')
+splitAppTy_maybe other = Nothing
+
+splitAppTy :: Type -> (Type, Type)
+splitAppTy ty = case splitAppTy_maybe ty of
+ Just pr -> pr
+ Nothing -> panic "splitAppTy"
+
+splitAppTys :: Type -> (Type, [Type])
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 (SynTy _ ty) args = split orig_ty ty args
- split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
- (TyConApp mkFunTyCon [], [ty1,ty2])
split orig_ty (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args)
+ split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
+ (TyConApp funTyCon [], [ty1,ty2])
split orig_ty ty args = (orig_ty, args)
\end{code}
~~~~~
\begin{code}
-mkFunTy :: GenType flexi -> GenType flexi -> GenType flexi
+mkFunTy :: Type -> Type -> Type
mkFunTy arg res = FunTy arg res
-mkFunTys :: [GenType flexi] -> GenType flexi -> GenType flexi
+mkFunTys :: [Type] -> Type -> Type
mkFunTys tys ty = foldr FunTy ty tys
-splitFunTy_maybe :: GenType flexi -> Maybe (GenType flexi, GenType flexi)
-splitFunTy_maybe (FunTy arg res) = Just (arg, res)
-splitFunTy_maybe (SynTy _ ty) = splitFunTy_maybe ty
-splitFunTy_maybe other = Nothing
+isFunTy :: Type -> Bool
+isFunTy ty = isJust (splitFunTy_maybe ty)
+
+splitFunTy :: Type -> (Type, Type)
+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)
+splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty'
+splitFunTy_maybe (FunTy arg res) = Just (arg, res)
+splitFunTy_maybe other = Nothing
-splitFunTys :: GenType flexi -> ([GenType flexi], GenType flexi)
+splitFunTys :: Type -> ([Type], Type)
splitFunTys ty = split [] ty ty
where
- split args orig_ty (FunTy arg res) = split (arg:args) res res
- split args orig_ty (SynTy _ ty) = split args orig_ty ty
- split args orig_ty ty = (reverse args, orig_ty)
+ 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)
+
+splitFunTysN :: Int -> Type -> ([Type], Type)
+-- Split off exactly n arg tys
+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)
+zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty
+ where
+ split acc [] nty ty = (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)
+
+funResultTy :: Type -> Type
+funResultTy ty | Just ty' <- coreView ty = funResultTy ty'
+funResultTy (FunTy arg res) = res
+funResultTy ty = pprPanic "funResultTy" (ppr ty)
+
+funArgTy :: Type -> Type
+funArgTy ty | Just ty' <- coreView ty = funArgTy 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}
-mkTyConApp :: TyCon -> [GenType flexi] -> GenType flexi
+mkTyConApp :: TyCon -> [Type] -> Type
mkTyConApp tycon tys
- | isFunTyCon tycon && length tys == 2
- = case tys of
- (ty1:ty2:_) -> FunTy ty1 ty2
+ | isFunTyCon tycon, [ty1,ty2] <- tys
+ = FunTy ty1 ty2
| otherwise
- = ASSERT(not (isSynTyCon tycon))
- TyConApp tycon tys
+ = TyConApp tycon tys
-mkTyConTy :: TyCon -> GenType flexi
-mkTyConTy tycon = ASSERT( not (isSynTyCon tycon) )
- TyConApp tycon []
+mkTyConTy :: TyCon -> Type
+mkTyConTy tycon = mkTyConApp tycon []
-- splitTyConApp "looks through" synonyms, because they don't
-- mean a distinct type, but all other type-constructor applications
-- including functions are returned as Just ..
-splitTyConApp_maybe :: GenType flexi -> Maybe (TyCon, [GenType flexi])
-splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
-splitTyConApp_maybe (FunTy arg res) = Just (mkFunTyCon, [arg,res])
-splitTyConApp_maybe (SynTy _ ty) = splitTyConApp_maybe ty
-splitTyConApp_maybe other = Nothing
-
--- splitAlgTyConApp_maybe looks for
--- *saturated* applications of *algebraic* data types
--- "Algebraic" => newtype, data type, or dictionary (not function types)
--- We return the constructors too.
-
-splitAlgTyConApp_maybe :: GenType flexi -> Maybe (TyCon, [GenType flexi], [Id])
-splitAlgTyConApp_maybe (TyConApp tc tys)
- | isAlgTyCon tc &&
- tyConArity tc == length tys = Just (tc, tys, tyConDataCons tc)
-splitAlgTyConApp_maybe (SynTy _ ty) = splitAlgTyConApp_maybe ty
-splitAlgTyConApp_maybe other = Nothing
-
-splitAlgTyConApp :: GenType flexi -> (TyCon, [GenType flexi], [Id])
- -- Here the "algebraic" property is an *assertion*
-splitAlgTyConApp (TyConApp tc tys) = ASSERT( isAlgTyCon tc && tyConArity tc == length tys )
- (tc, tys, tyConDataCons tc)
-splitAlgTyConApp (SynTy _ ty) = splitAlgTyConApp ty
-\end{code}
+tyConAppTyCon :: Type -> TyCon
+tyConAppTyCon ty = fst (splitTyConApp ty)
-y"Dictionary" types are just ordinary data types, but you can
-tell from the type constructor whether it's a dictionary or not.
+tyConAppArgs :: Type -> [Type]
+tyConAppArgs ty = snd (splitTyConApp ty)
-\begin{code}
-mkDictTy :: Class -> [GenType flexi] -> GenType flexi
-mkDictTy clas tys = TyConApp (classTyCon clas) tys
+splitTyConApp :: Type -> (TyCon, [Type])
+splitTyConApp ty = case splitTyConApp_maybe ty of
+ Just stuff -> stuff
+ Nothing -> pprPanic "splitTyConApp" (ppr ty)
-splitDictTy_maybe :: GenType flexi -> Maybe (Class, [GenType flexi])
-splitDictTy_maybe (TyConApp tc tys)
- | maybeToBool maybe_class
- && tyConArity tc == length tys = Just (clas, tys)
- where
- maybe_class = tyConClass_maybe tc
- Just clas = maybe_class
-
-splitDictTy_maybe (SynTy _ ty) = splitDictTy_maybe ty
-splitDictTy_maybe other = Nothing
-
-isDictTy :: GenType flexi -> Bool
- -- This version is slightly more efficient than (maybeToBool . splitDictTy)
-isDictTy (TyConApp tc tys)
- | maybeToBool (tyConClass_maybe tc)
- && tyConArity tc == length tys
- = True
-isDictTy (SynTy _ ty) = isDictTy ty
-isDictTy other = False
+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
\end{code}
SynTy
~~~~~
-\begin{code}
-mkSynTy syn_tycon tys
- = ASSERT(isSynTyCon syn_tycon)
- SynTy (TyConApp syn_tycon tys)
- (instantiateTauTy (zipTyVarEnv tyvars tys) body)
- where
- (tyvars, body) = getSynTyConDefn syn_tycon
-
-isSynTy (SynTy _ _) = True
-isSynTy other = False
-\end{code}
-
Notes on type synonyms
~~~~~~~~~~~~~~~~~~~~~~
The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
interfaces. Notably this plays a role in tcTySigs in TcBinds.lhs.
+ 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}
+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
+
+-- ToDo: this could be moved to the code generator, using splitTyConApp instead
+-- of inspecting the type directly.
+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)
+ -- 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}
---------------------------------------------------------------------
~~~~~~~~
\begin{code}
-mkForAllTy = ForAllTy
+mkForAllTy :: TyVar -> Type -> Type
+mkForAllTy tyvar ty
+ = mkForAllTys [tyvar] ty
-mkForAllTys :: [GenTyVar flexi] -> GenType flexi -> GenType flexi
+mkForAllTys :: [TyVar] -> Type -> Type
mkForAllTys tyvars ty = foldr ForAllTy ty tyvars
-splitForAllTy_maybe :: GenType flexi -> Maybe (GenTyVar flexi, GenType flexi)
-splitForAllTy_maybe (SynTy _ ty) = splitForAllTy_maybe ty
-splitForAllTy_maybe (ForAllTy tyvar ty) = Just(tyvar, ty)
-splitForAllTy_maybe _ = Nothing
+isForAllTy :: Type -> Bool
+isForAllTy (NoteTy _ ty) = isForAllTy ty
+isForAllTy (ForAllTy _ _) = True
+isForAllTy other_ty = False
-splitForAllTys :: GenType flexi -> ([GenTyVar flexi], GenType flexi)
+splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
+splitForAllTy_maybe ty = splitFAT_m ty
+ where
+ splitFAT_m ty | Just ty' <- coreView ty = splitFAT_m ty'
+ splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
+ splitFAT_m _ = Nothing
+
+splitForAllTys :: Type -> ([TyVar], Type)
splitForAllTys ty = split ty ty []
where
- split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
- split orig_ty (SynTy _ ty) tvs = split orig_ty ty tvs
- split orig_ty t tvs = (reverse tvs, orig_ty)
+ 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)
+
+dropForAlls :: Type -> Type
+dropForAlls ty = snd (splitForAllTys ty)
\end{code}
+-- (mkPiType now in CoreUtils)
+
+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}
-applyTy :: GenType flexi -> GenType flexi -> GenType flexi
-applyTy (SynTy _ fun) arg = applyTy fun arg
-applyTy (ForAllTy tv ty) arg = instantiateTy (mkTyVarEnv [(tv,arg)]) ty
+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"
+
+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 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 ()
+
+applyTys orig_fun_ty [] = orig_fun_ty
+applyTys 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)
+ where
+ (tvs, rho_ty) = splitForAllTys orig_fun_ty
+ n_tvs = length tvs
+ n_args = length arg_tys
\end{code}
%************************************************************************
%* *
-\subsection{Stuff to do with the source-language types}
+\subsection{Source types}
%* *
%************************************************************************
-\begin{code}
-type RhoType = Type
-type TauType = Type
-type ThetaType = [(Class, [Type])]
-type SigmaType = Type
-\end{code}
+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.
-@isTauTy@ tests for nested for-alls.
+Source types are always lifted.
-\begin{code}
-isTauTy :: GenType flexi -> Bool
-isTauTy (TyVarTy v) = True
-isTauTy (TyConApp _ tys) = all isTauTy tys
-isTauTy (AppTy a b) = isTauTy a && isTauTy b
-isTauTy (FunTy a b) = isTauTy a && isTauTy b
-isTauTy (SynTy _ ty) = isTauTy ty
-isTauTy other = False
-\end{code}
+The key function is predTypeRep which gives the representation of a source type:
\begin{code}
-mkRhoTy :: [(Class, [GenType flexi])] -> GenType flexi -> GenType flexi
-mkRhoTy theta ty = foldr (\(c,t) r -> FunTy (mkDictTy c t) r) ty theta
-
-splitRhoTy :: GenType flexi -> ([(Class, [GenType flexi])], GenType flexi)
-splitRhoTy ty = split ty ty []
- where
- split orig_ty (FunTy arg res) ts = case splitDictTy_maybe arg of
- Just pair -> split res res (pair:ts)
- Nothing -> (reverse ts, orig_ty)
- split orig_ty (SynTy _ ty) ts = split orig_ty ty ts
- split orig_ty ty ts = (reverse ts, orig_ty)
+mkPredTy :: PredType -> Type
+mkPredTy pred = PredTy pred
+
+mkPredTys :: ThetaType -> [Type]
+mkPredTys preds = map PredTy preds
+
+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
+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}
-mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkRhoTy theta tau)
-
-splitSigmaTy :: GenType flexi -> ([GenTyVar flexi], [(Class, [GenType flexi])], GenType flexi)
-splitSigmaTy ty =
- (tyvars, theta, tau)
- where
- (tyvars,rho) = splitForAllTys ty
- (theta,tau) = splitRhoTy rho
+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
\end{code}
Finding the kind of a type
~~~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
-typeKind :: GenType flexi -> Kind
-
-typeKind (TyVarTy tyvar) = tyVarKind tyvar
-typeKind (TyConApp tycon tys) = foldr (\_ k -> resultKind k) (tyConKind tycon) tys
-typeKind (SynTy _ ty) = typeKind ty
-typeKind (FunTy fun arg) = mkBoxedTypeKind
-typeKind (AppTy fun arg) = resultKind (typeKind fun)
-typeKind (ForAllTy _ _) = mkBoxedTypeKind
+typeKind :: Type -> Kind
+
+typeKind (TyVarTy tyvar) = tyVarKind tyvar
+typeKind (TyConApp tycon tys) = foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
+typeKind (NoteTy _ ty) = typeKind ty
+typeKind (PredTy _) = liftedTypeKind -- Predicates are always
+ -- represented by lifted types
+typeKind (AppTy fun arg) = kindFunResult (typeKind fun)
+typeKind (FunTy arg res) = liftedTypeKind
+typeKind (ForAllTy tv ty) = typeKind ty
\end{code}
Free variables of a type
~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
-tyVarsOfType :: GenType flexi -> GenTyVarSet flexi
-
-tyVarsOfType (TyVarTy tv) = unitTyVarSet tv
+tyVarsOfType :: Type -> TyVarSet
+-- NB: for type synonyms tyVarsOfType does *not* expand the synonym
+tyVarsOfType (TyVarTy tv) = unitVarSet tv
tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
-tyVarsOfType (SynTy ty1 ty2) = tyVarsOfType ty1
-tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionTyVarSets` tyVarsOfType res
-tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionTyVarSets` tyVarsOfType arg
-tyVarsOfType (ForAllTy tyvar ty) = tyVarsOfType ty `minusTyVarSet` unitTyVarSet tyvar
-
-tyVarsOfTypes :: [GenType flexi] -> GenTyVarSet flexi
-tyVarsOfTypes tys = foldr (unionTyVarSets.tyVarsOfType) emptyTyVarSet tys
-
--- Find the free names of a type, including the type constructors and classes it mentions
-namesOfType :: GenType flexi -> NameSet
-namesOfType (TyVarTy tv) = unitNameSet (getName tv)
-namesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets`
- namesOfTypes tys
-namesOfType (SynTy ty1 ty2) = namesOfType ty1
-namesOfType (FunTy arg res) = namesOfType arg `unionNameSets` namesOfType res
-namesOfType (AppTy fun arg) = namesOfType fun `unionNameSets` namesOfType arg
-namesOfType (ForAllTy tyvar ty) = namesOfType ty `minusNameSet` unitNameSet (getName tyvar)
-
-namesOfTypes tys = foldr (unionNameSets . namesOfType) emptyNameSet tys
+tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
+tyVarsOfType (PredTy sty) = tyVarsOfPred sty
+tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
+tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
+tyVarsOfType (ForAllTy tyvar ty) = delVarSet (tyVarsOfType ty) tyvar
+
+tyVarsOfTypes :: [Type] -> TyVarSet
+tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
+
+tyVarsOfPred :: PredType -> TyVarSet
+tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
+tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
+
+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{Instantiating a type}
+\subsection{TidyType}
%* *
%************************************************************************
+tidyTy 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.
+
\begin{code}
-instantiateTy :: TyVarEnv (GenType flexi) -> GenType flexi -> GenType flexi
-instantiateTauTy :: TyVarEnv (GenType flexi2) -> GenType flexi1 -> GenType flexi2
+tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
+tidyTyVarBndr (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'
+ where
+ name = tyVarName tyvar
+
+tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
+-- Add the free tyvars 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))
+
+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
+ = 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
+ = go ty
+ where
+ go (TyVarTy tv) = case lookupVarEnv subst tv of
+ Nothing -> TyVarTy tv
+ 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)
+ go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
+ where
+ (envp, tvp) = tidyTyVarBndr env tv
+ go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
--- instantiateTy applies a type environment to a type.
--- It can handle shadowing; for example:
--- f = /\ t1 t2 -> \ d ->
--- letrec f' = /\ t1 -> \x -> ...(f' t1 x')...
--- in f' t1
--- Here, when we clone t1 to t1', say, we'll come across shadowing
--- when applying the clone environment to the type of f'.
---
--- As a sanity check, we should also check that name capture
--- doesn't occur, but that means keeping track of the free variables of the
--- range of the TyVarEnv, which I don't do just yet.
+tidyTypes env tys = map (tidyType env) tys
+
+tidyPred :: TidyEnv -> PredType -> PredType
+tidyPred env (IParam n ty) = IParam n (tidyType env ty)
+tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
+\end{code}
-instantiateTy tenv ty
- | isEmptyTyVarEnv tenv
- = ty
- | otherwise
- = go tenv ty
+@tidyOpenType@ grabs the free type variables, tidies them
+and then uses @tidyType@ to work over the type itself
+
+\begin{code}
+tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
+tidyOpenType env ty
+ = (env', tidyType env' ty)
where
- go tenv ty@(TyVarTy tv) = case (lookupTyVarEnv tenv tv) of
- Nothing -> ty
- Just ty -> ty
- go tenv (TyConApp tc tys) = TyConApp tc (map (go tenv) tys)
- go tenv (SynTy ty1 ty2) = SynTy (go tenv ty1) (go tenv ty2)
- go tenv (FunTy arg res) = FunTy (go tenv arg) (go tenv res)
- go tenv (AppTy fun arg) = mkAppTy (go tenv fun) (go tenv arg)
- go tenv (ForAllTy tv ty) = ForAllTy tv (go tenv' ty)
- where
- tenv' = case lookupTyVarEnv tenv tv of
- Nothing -> tenv
- Just _ -> delFromTyVarEnv tenv tv
+ env' = tidyFreeTyVars env (tyVarsOfType ty)
--- instantiateTauTy works only (a) on types with no ForAlls,
--- and when (b) all the type variables are being instantiated
--- In return it is more polymorphic than instantiateTy
+tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
+tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
-instantiateTauTy tenv ty = go ty
- where
- go ty@(TyVarTy tv) = case (lookupTyVarEnv tenv tv) of
- Just ty -> ty -- Must succeed
- go (TyConApp tc tys) = TyConApp tc (map go tys)
- go (SynTy ty1 ty2) = SynTy (go ty1) (go ty2)
- go (FunTy arg res) = FunTy (go arg) (go res)
- go (AppTy fun arg) = mkAppTy (go fun) (go arg)
- go (ForAllTy tv ty) = panic "instantiateTauTy"
-
-
-instantiateThetaTy :: TyVarEnv Type -> ThetaType -> ThetaType
-instantiateThetaTy tenv theta
- = [(clas, map (instantiateTauTy tenv) tys) | (clas, tys) <- theta]
+tidyTopType :: Type -> Type
+tidyTopType ty = tidyType emptyTidyEnv ty
\end{code}
%************************************************************************
%* *
-\subsection{Boxedness and pointedness}
+ Tidying Kinds
%* *
%************************************************************************
-A type is
- *unboxed* iff its representation is other than a pointer
- Unboxed types cannot instantiate a type variable
- Unboxed types are always unpointed.
+We use a grevious hack for tidying KindVars. A TidyEnv contains
+a (VarEnv Var) substitution, to express the renaming; but
+KindVars are not Vars. The Right Thing ultimately is to make them
+into Vars (and perhaps make Kinds into Types), but I just do a hack
+here: I make up a TyVar just to remember the new OccName for the
+renamed KindVar
- *unpointed* iff it can't be a thunk, and cannot have value bottom
- An unpointed type may or may not be unboxed.
- (E.g. Array# is unpointed, but boxed.)
- An unpointed type *can* instantiate a type variable,
- provided it is boxed.
+\begin{code}
+tidyKind :: TidyEnv -> Kind -> (TidyEnv, Kind)
+tidyKind env@(tidy_env, subst) (KindVar kvar)
+ | Just tv <- lookupVarEnv_Directly subst uniq
+ = (env, KindVar (setKindVarOcc kvar (getOccName tv)))
+ | otherwise
+ = ((tidy', subst'), KindVar kvar')
+ where
+ uniq = kindVarUniq kvar
+ (tidy', occ') = tidyOccName tidy_env (kindVarOcc kvar)
+ kvar' = setKindVarOcc kvar occ'
+ fake_tv = mkTyVar tv_name (panic "tidyKind:fake tv kind")
+ tv_name = mkInternalName uniq occ' noSrcLoc
+ subst' = extendVarEnv subst fake_tv fake_tv
+
+tidyKind env (FunKind k1 k2)
+ = (env2, FunKind k1' k2')
+ where
+ (env1, k1') = tidyKind env k1
+ (env2, k2') = tidyKind env1 k2
- *primitive* iff it is a built-in type that can't be expressed
- in Haskell
+tidyKind env k = (env, k) -- Atomic kinds
+\end{code}
-Currently, all primitive types are unpointed, but that's not necessarily
-the case. (E.g. Int could be primitive.)
+
+%************************************************************************
+%* *
+\subsection{Liftedness}
+%* *
+%************************************************************************
\begin{code}
-isUnboxedType :: Type -> Bool
-isUnboxedType ty = case typePrimRep ty of
- PtrRep -> False
- other -> True
-
--- Danger! Currently the unpointed types are precisely
--- the primitive ones, but that might not always be the case
-isUnpointedType :: Type -> Bool
-isUnpointedType ty = case splitTyConApp_maybe ty of
- Just (tc, ty_args) -> isPrimTyCon tc
+isUnLiftedType :: 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 | Just ty' <- coreView ty = isUnLiftedType ty'
+isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
+isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
+isUnLiftedType other = False
+
+isUnboxedTupleType :: Type -> Bool
+isUnboxedTupleType ty = case splitTyConApp_maybe ty of
+ Just (tc, ty_args) -> isUnboxedTupleTyCon tc
other -> False
-typePrimRep :: Type -> PrimRep
-typePrimRep ty = case splitTyConApp_maybe ty of
- Just (tc, ty_args) -> tyConPrimRep tc
- other -> PtrRep
+-- Should only be applied to *types*; hence the assert
+isAlgType :: Type -> Bool
+isAlgType ty = case splitTyConApp_maybe ty of
+ Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
+ isAlgTyCon 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}
+isStrictType (PredTy pred) = isStrictPred pred
+isStrictType ty | Just ty' <- coreView ty = isStrictType ty'
+isStrictType (ForAllTy tv ty) = isStrictType ty
+isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
+isStrictType other = False
+
+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.]
+\end{code}
+
+\begin{code}
+isPrimitiveType :: Type -> Bool
+-- Returns 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
\end{code}
%************************************************************************
%* *
-\subsection{Matching on types}
+\subsection{Sequencing on types
%* *
%************************************************************************
-Matching is a {\em unidirectional} process, matching a type against a
-template (which is just a type with type variables in it). The
-matcher assumes that there are no repeated type variables in the
-template, so that it simply returns a mapping of type variables to
-types. It also fails on nested foralls.
-
-@matchTys@ matches corresponding elements of a list of templates and
-types.
-
\begin{code}
-matchTy :: GenType flexi1 -- Template
- -> GenType flexi2 -- Proposed instance of template
- -> Maybe (TyVarEnv (GenType flexi2)) -- Matching substitution
-
-
-matchTys :: [GenType flexi1] -- Templates
- -> [GenType flexi2] -- Proposed instance of template
- -> Maybe (TyVarEnv (GenType flexi2), -- Matching substitution
- [GenType flexi2]) -- Left over instance types
-
-matchTy ty1 ty2 = match ty1 ty2 (\s -> Just s) emptyTyVarEnv
-matchTys tys1 tys2 = match_list tys1 tys2 (\pr -> Just pr) emptyTyVarEnv
+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
+
+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
\end{code}
-@match@ is the main function.
+
+%************************************************************************
+%* *
+ Equality for Core types
+ (We don't use instances so that we know where it happens)
+%* *
+%************************************************************************
+
+Note that eqType works right even for partial applications of newtypes.
+See Note [Newtype eta] in TyCon.lhs
\begin{code}
-match :: GenType flexi1 -> GenType flexi2 -- Current match pair
- -> (TyVarEnv (GenType flexi2) -> Maybe result) -- Continuation
- -> TyVarEnv (GenType flexi2) -- Current substitution
- -> Maybe result
-
--- When matching against a type variable, see if the variable
--- has already been bound. If so, check that what it's bound to
--- is the same as ty; if not, bind it and carry on.
-
-match (TyVarTy v) ty k = \s -> case lookupTyVarEnv s v of
- Nothing -> k (addToTyVarEnv s v ty)
- Just ty' | ty' == ty -> k s -- Succeeds
- | otherwise -> Nothing -- Fails
-
-match (FunTy arg1 res1) (FunTy arg2 res2) k = match arg1 arg2 (match res1 res2 k)
-match (AppTy fun1 arg1) (AppTy fun2 arg2) k = match fun1 fun2 (match arg1 arg2 k)
-match (TyConApp tc1 tys1) (TyConApp tc2 tys2) k | tc1 == tc2
- = match_list tys1 tys2 ( \(s,tys2') ->
- if null tys2' then
- k s -- Succeed
- else
- Nothing -- Fail
- )
-
- -- With type synonyms, we have to be careful for the exact
- -- same reasons as in the unifier. Please see the
- -- considerable commentary there before changing anything
- -- here! (WDP 95/05)
-match (SynTy _ ty1) ty2 k = match ty1 ty2 k
-match ty1 (SynTy _ ty2) k = match ty1 ty2 k
-
--- Catch-all fails
-match _ _ _ = \s -> Nothing
-
-match_list [] tys2 k = \s -> k (s, tys2)
-match_list (ty1:tys1) [] k = panic "match_list"
-match_list (ty1:tys1) (ty2:tys2) k = match ty1 ty2 (match_list tys1 tys2 k)
+coreEqType :: Type -> Type -> Bool
+coreEqType t1 t2
+ = eq rn_env t1 t2
+ where
+ rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
+
+ 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
+ eq env (FunTy s1 t1) (FunTy s2 t2) = eq env s1 s2 && eq env t1 t2
+ eq env (TyConApp tc1 tys1) (TyConApp tc2 tys2)
+ | tc1 == tc2, all2 (eq env) tys1 tys2 = True
+ -- The lengths should be equal because
+ -- the two types have the same kind
+ -- NB: if the type constructors differ that does not
+ -- necessarily mean that the types aren't equal
+ -- (synonyms, newtypes)
+ -- Even if the type constructors are the same, but the arguments
+ -- differ, the two types could be the same (e.g. if the arg is just
+ -- ignored in the RHS). In both these cases we fall through to an
+ -- attempt to expand one side or the other.
+
+ -- Now deal with newtypes, synonyms, pred-tys
+ eq env t1 t2 | Just t1' <- coreView t1 = eq env t1' t2
+ | Just t2' <- coreView t2 = eq env t1 t2'
+
+ -- Fall through case; not equal!
+ eq env t1 t2 = False
\end{code}
+
%************************************************************************
%* *
-\subsection{Equality on types}
+ Comparision for source types
+ (We don't use instances so that we know where it happens)
%* *
%************************************************************************
-For the moment at least, type comparisons don't work if
-there are embedded for-alls.
+Note that
+ tcEqType, tcCmpType
+do *not* look through newtypes, PredTypes
\begin{code}
-instance Eq (GenType flexi) where
- ty1 == ty2 = case ty1 `cmpTy` ty2 of { EQ -> True; other -> False }
+tcEqType :: Type -> Type -> Bool
+tcEqType t1 t2 = isEqual $ cmpType t1 t2
+
+tcEqTypes :: [Type] -> [Type] -> Bool
+tcEqTypes tys1 tys2 = isEqual $ cmpTypes tys1 tys2
+
+tcCmpType :: Type -> Type -> Ordering
+tcCmpType t1 t2 = cmpType t1 t2
-instance Ord (GenType flexi) where
- compare ty1 ty2 = cmpTy ty1 ty2
+tcCmpTypes :: [Type] -> [Type] -> Ordering
+tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2
-cmpTy :: GenType flexi -> GenType flexi -> Ordering
-cmpTy ty1 ty2
- = cmp emptyTyVarEnv ty1 ty2
+tcEqPred :: PredType -> PredType -> Bool
+tcEqPred p1 p2 = isEqual $ cmpPred p1 p2
+
+tcCmpPred :: PredType -> PredType -> Ordering
+tcCmpPred p1 p2 = cmpPred p1 p2
+
+tcEqTypeX :: RnEnv2 -> Type -> Type -> Bool
+tcEqTypeX env t1 t2 = isEqual $ cmpTypeX env t1 t2
+\end{code}
+
+Now here comes the real worker
+
+\begin{code}
+cmpType :: Type -> Type -> Ordering
+cmpType t1 t2 = cmpTypeX rn_env t1 t2
where
- -- The "env" maps type variables in ty1 to type variables in ty2
- -- So when comparing for-alls.. (forall tv1 . t1) (forall tv2 . t2)
- -- we in effect substitute tv2 for tv1 in t1 before continuing
- lookup env tv1 = case lookupTyVarEnv env tv1 of
- Just tv2 -> tv2
- Nothing -> tv1
-
- -- Get rid of SynTy
- cmp env (SynTy _ ty1) ty2 = cmp env ty1 ty2
- cmp env ty1 (SynTy _ ty2) = cmp env ty1 ty2
-
- -- Deal with equal constructors
- cmp env (TyVarTy tv1) (TyVarTy tv2) = lookup env tv1 `compare` tv2
- cmp env (AppTy f1 a1) (AppTy f2 a2) = cmp env f1 f2 `thenCmp` cmp env a1 a2
- cmp env (FunTy f1 a1) (FunTy f2 a2) = cmp env f1 f2 `thenCmp` cmp env a1 a2
- cmp env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmps env tys1 tys2)
- cmp env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmp (addToTyVarEnv env tv1 tv2) t1 t2
-
- -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy
- cmp env (AppTy _ _) (TyVarTy _) = GT
-
- cmp env (FunTy _ _) (TyVarTy _) = GT
- cmp env (FunTy _ _) (AppTy _ _) = GT
+ rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
+
+cmpTypes :: [Type] -> [Type] -> Ordering
+cmpTypes ts1 ts2 = cmpTypesX rn_env ts1 ts2
+ where
+ rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2))
+
+cmpPred :: PredType -> PredType -> Ordering
+cmpPred p1 p2 = cmpPredX rn_env p1 p2
+ where
+ rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfPred p1 `unionVarSet` tyVarsOfPred p2))
+
+cmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse
+cmpTypeX env t1 t2 | Just t1' <- tcView t1 = cmpTypeX env t1' t2
+ | Just t2' <- tcView t2 = cmpTypeX env t1 t2'
+
+cmpTypeX env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 `compare` rnOccR env tv2
+cmpTypeX env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTypeX (rnBndr2 env tv1 tv2) t1 t2
+cmpTypeX env (AppTy s1 t1) (AppTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
+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
- cmp env (TyConApp _ _) (TyVarTy _) = GT
- cmp env (TyConApp _ _) (AppTy _ _) = GT
- cmp env (TyConApp _ _) (FunTy _ _) = GT
+cmpTypeX env (FunTy _ _) (TyVarTy _) = GT
+cmpTypeX env (FunTy _ _) (AppTy _ _) = GT
- cmp env (ForAllTy _ _) other = GT
+cmpTypeX env (TyConApp _ _) (TyVarTy _) = GT
+cmpTypeX env (TyConApp _ _) (AppTy _ _) = GT
+cmpTypeX env (TyConApp _ _) (FunTy _ _) = GT
- cmp env _ _ = LT
-
- cmps env [] [] = EQ
- cmps env (t:ts) [] = GT
- cmps env [] (t:ts) = LT
- cmps env (t1:t1s) (t2:t2s) = cmp env t1 t2 `thenCmp` cmps env t1s t2s
+cmpTypeX env (ForAllTy _ _) (TyVarTy _) = GT
+cmpTypeX env (ForAllTy _ _) (AppTy _ _) = GT
+cmpTypeX env (ForAllTy _ _) (FunTy _ _) = GT
+cmpTypeX env (ForAllTy _ _) (TyConApp _ _) = GT
+
+cmpTypeX env (PredTy _) t2 = GT
+
+cmpTypeX env _ _ = LT
+
+-------------
+cmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering
+cmpTypesX env [] [] = EQ
+cmpTypesX env (t1:tys1) (t2:tys2) = cmpTypeX env t1 t2 `thenCmp` cmpTypesX env tys1 tys2
+cmpTypesX env [] tys = LT
+cmpTypesX env ty [] = 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
\end{code}
+PredTypes are used as a FM key in TcSimplify,
+so we take the easy path and make them an instance of Ord
+
+\begin{code}
+instance Eq PredType where { (==) = tcEqPred }
+instance Ord PredType where { compare = tcCmpPred }
+\end{code}
%************************************************************************
%* *
-\subsection{Grime}
+ Type substitutions
%* *
%************************************************************************
+\begin{code}
+data TvSubst
+ = TvSubst InScopeSet -- The in-scope type variables
+ TvSubstEnv -- The substitution itself
+ -- See Note [Apply Once]
+
+{- ----------------------------------------------------------
+ Note [Apply Once]
+
+We use TvSubsts to instantiate things, and we might instantiate
+ forall a b. ty
+\with the types
+ [a, b], or [b, a].
+So the substition might go [a->b, b->a]. A similar situation arises in Core
+when we find a beta redex like
+ (/\ a /\ b -> e) b a
+Then we also end up with a substition that permutes type variables. Other
+variations happen to; for example [a -> (a, b)].
+
+ ***************************************************
+ *** So a TvSubst must be applied precisely once ***
+ ***************************************************
+
+A TvSubst is not idempotent, but, unlike the non-idempotent substitution
+we use during unifications, it must not be repeatedly applied.
+-------------------------------------------------------------- -}
+
+
+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
+composeTvSubst in_scope env1 env2
+ = env1 `plusVarEnv` mapVarEnv (substTy subst1) env2
+ -- First apply env1 to the range of env2
+ -- Then combine the two, making sure that env1 loses if
+ -- both bind the same variable; that's why env1 is the
+ -- *left* argument to plusVarEnv, because the right arg wins
+ where
+ subst1 = TvSubst in_scope env1
+
+emptyTvSubst = TvSubst emptyInScopeSet emptyVarEnv
+
+isEmptyTvSubst :: TvSubst -> Bool
+isEmptyTvSubst (TvSubst _ env) = isEmptyVarEnv env
+
+mkTvSubst :: InScopeSet -> TvSubstEnv -> TvSubst
+mkTvSubst = TvSubst
+
+getTvSubstEnv :: TvSubst -> TvSubstEnv
+getTvSubstEnv (TvSubst _ env) = env
+
+getTvInScope :: TvSubst -> InScopeSet
+getTvInScope (TvSubst in_scope _) = in_scope
+
+isInScope :: Var -> TvSubst -> Bool
+isInScope v (TvSubst in_scope _) = v `elemInScopeSet` in_scope
+
+notElemTvSubst :: TyVar -> TvSubst -> Bool
+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
+
+extendTvSubst :: TvSubst -> TyVar -> Type -> TvSubst
+extendTvSubst (TvSubst in_scope env) tv ty = TvSubst in_scope (extendVarEnv env tv ty)
+
+extendTvSubstList :: TvSubst -> [TyVar] -> [Type] -> TvSubst
+extendTvSubstList (TvSubst in_scope env) tvs tys
+ = TvSubst in_scope (extendVarEnvList env (tvs `zip` tys))
+
+-- mkOpenTvSubst and zipOpenTvSubst generate the in-scope set from
+-- the types given; but it's just a thunk so with a bit of luck
+-- it'll never be evaluated
+
+mkOpenTvSubst :: TvSubstEnv -> TvSubst
+mkOpenTvSubst env = TvSubst (mkInScopeSet (tyVarsOfTypes (varEnvElts env))) env
+
+zipOpenTvSubst :: [TyVar] -> [Type] -> TvSubst
+zipOpenTvSubst tyvars tys
+#ifdef DEBUG
+ | length tyvars /= length tys
+ = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
+ | otherwise
+#endif
+ = TvSubst (mkInScopeSet (tyVarsOfTypes tys)) (zipTyEnv tyvars tys)
+
+-- mkTopTvSubst is called when doing top-level substitutions.
+-- Here we expect that the free vars of the range of the
+-- substitution will be empty.
+mkTopTvSubst :: [(TyVar, Type)] -> TvSubst
+mkTopTvSubst prs = TvSubst emptyInScopeSet (mkVarEnv prs)
+
+zipTopTvSubst :: [TyVar] -> [Type] -> TvSubst
+zipTopTvSubst tyvars tys
+#ifdef DEBUG
+ | length tyvars /= length tys
+ = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
+ | otherwise
+#endif
+ = TvSubst emptyInScopeSet (zipTyEnv tyvars tys)
+
+zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv
+zipTyEnv tyvars tys
+#ifdef DEBUG
+ | length tyvars /= length tys
+ = pprTrace "mkTopTvSubst" (ppr tyvars $$ ppr tys) emptyVarEnv
+ | otherwise
+#endif
+ = zip_ty_env tyvars tys emptyVarEnv
+
+-- Later substitutions in the list over-ride earlier ones,
+-- but there should be no loops
+zip_ty_env [] [] env = env
+zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendVarEnv env tv ty)
+ -- There used to be a special case for when
+ -- ty == TyVarTy tv
+ -- (a not-uncommon case) in which case the substitution was dropped.
+ -- But the type-tidier changes the print-name of a type variable without
+ -- changing the unique, and that led to a bug. Why? Pre-tidying, we had
+ -- a type {Foo t}, where Foo is a one-method class. So Foo is really a newtype.
+ -- And it happened that t was the type variable of the class. Post-tiding,
+ -- it got turned into {Foo t2}. The ext-core printer expanded this using
+ -- sourceTypeRep, but that said "Oh, t == t2" because they have the same unique,
+ -- and so generated a rep type mentioning t not t2.
+ --
+ -- Simplest fix is to nuke the "optimisation"
+zip_ty_env tvs tys env = pprTrace "Var/Type length mismatch: " (ppr tvs $$ ppr tys) env
+-- zip_ty_env _ _ env = env
+
+instance Outputable TvSubst where
+ ppr (TvSubst ins env)
+ = sep[ ptext SLIT("<TvSubst"),
+ nest 2 (ptext SLIT("In scope:") <+> ppr ins),
+ nest 2 (ptext SLIT("Env:") <+> ppr env) ]
+\end{code}
+
+%************************************************************************
+%* *
+ Performing type substitutions
+%* *
+%************************************************************************
\begin{code}
-showTypeCategory :: Type -> Char
- {-
- {C,I,F,D} char, int, float, double
- T tuple
- S other single-constructor type
- {c,i,f,d} unboxed ditto
- t *unpacked* tuple
- s *unpacked" single-cons...
-
- v void#
- a primitive array
-
- E enumeration type
- + dictionary, unless it's a ...
- L List
- > function
- M other (multi-constructor) data-con type
- . other type
- - reserved for others to mark as "uninteresting"
- -}
-showTypeCategory ty
- = if isDictTy ty
- then '+'
- else
- case splitTyConApp_maybe ty of
- Nothing -> if maybeToBool (splitFunTy_maybe ty)
- then '>'
- else '.'
-
- Just (tycon, _) ->
- let utc = uniqueOf tycon in
- if utc == charDataConKey then 'C'
- else if utc == intDataConKey then 'I'
- else if utc == floatDataConKey then 'F'
- else if utc == doubleDataConKey then 'D'
- else if utc == integerDataConKey then 'J'
- else if utc == charPrimTyConKey then 'c'
- else if (utc == intPrimTyConKey || utc == wordPrimTyConKey
- || utc == addrPrimTyConKey) then 'i'
- else if utc == floatPrimTyConKey then 'f'
- else if utc == doublePrimTyConKey then 'd'
- else if isPrimTyCon tycon {- array, we hope -} then 'A'
- else if isEnumerationTyCon tycon then 'E'
- else if isTupleTyCon tycon then 'T'
- else if maybeToBool (maybeTyConSingleCon tycon) then 'S'
- else if utc == listTyConKey then 'L'
- else 'M' -- oh, well...
+substTyWith :: [TyVar] -> [Type] -> Type -> Type
+substTyWith tvs tys = ASSERT( length tvs == length tys )
+ substTy (zipOpenTvSubst tvs tys)
+
+substTy :: TvSubst -> Type -> Type
+substTy subst ty | isEmptyTvSubst subst = ty
+ | otherwise = subst_ty subst ty
+
+substTys :: TvSubst -> [Type] -> [Type]
+substTys subst tys | isEmptyTvSubst subst = tys
+ | otherwise = map (subst_ty subst) tys
+
+substTheta :: TvSubst -> ThetaType -> ThetaType
+substTheta subst theta
+ | isEmptyTvSubst subst = theta
+ | otherwise = map (substPred subst) theta
+
+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)
+
+deShadowTy :: TyVarSet -> Type -> Type -- Remove any nested binders mentioning tvs
+deShadowTy tvs ty
+ = subst_ty (mkTvSubst in_scope emptyTvSubstEnv) ty
+ where
+ in_scope = mkInScopeSet tvs
+
+-- Note that the in_scope set is poked only if we hit a forall
+-- so it may often never be fully computed
+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 (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)
+
+substTyVar :: TvSubst -> TyVar -> Type
+substTyVar subst tv
+ = case lookupTyVar subst tv of
+ Nothing -> TyVarTy tv
+ Just ty' -> ty' -- See Note [Apply Once]
+
+lookupTyVar :: TvSubst -> TyVar -> Maybe Type
+lookupTyVar (TvSubst in_scope env) tv = lookupVarEnv env tv
+
+substTyVarBndr :: TvSubst -> TyVar -> (TvSubst, TyVar)
+substTyVarBndr subst@(TvSubst in_scope env) old_var
+ | old_var == new_var -- No need to clone
+ -- But we *must* zap any current substitution for the variable.
+ -- For example:
+ -- (\x.e) with id_subst = [x |-> e']
+ -- Here we must simply zap the substitution for x
+ --
+ -- The new_id isn't cloned, but it may have a different type
+ -- etc, so we must return it, not the old id
+ = (TvSubst (in_scope `extendInScopeSet` new_var)
+ (delVarEnv env old_var),
+ new_var)
+
+ | otherwise -- The new binder is in scope so
+ -- we'd better rename it away from the in-scope variables
+ -- Extending the substitution to do this renaming also
+ -- has the (correct) effect of discarding any existing
+ -- substitution for that variable
+ = (TvSubst (in_scope `extendInScopeSet` new_var)
+ (extendVarEnv env old_var (TyVarTy new_var)),
+ new_var)
+ where
+ new_var = uniqAway in_scope old_var
+ -- The uniqAway part makes sure the new variable is not already in scope
\end{code}
projects / ghc-hetmet.git / blobdiff