\begin{code}
module Type (
- -- re-exports from TypeRep:
- Type, PredType, ThetaType,
- Kind, TyVarSubst,
-
- superKind, superBoxity, -- KX and BX respectively
- liftedBoxity, unliftedBoxity, -- :: BX
- openKindCon, -- :: KX
- typeCon, -- :: BX -> KX
- liftedTypeKind, unliftedTypeKind, openTypeKind, -- :: KX
- mkArrowKind, mkArrowKinds, -- :: KX -> KX -> KX
- isTypeKind, isAnyTypeKind,
+ -- re-exports from TypeRep
+ TyThing(..), Type, PredType(..), ThetaType,
funTyCon,
- -- exports from this module:
- hasMoreBoxityInfo, defaultKind,
+ -- Re-exports from Kind
+ module Kind,
+
+ -- Re-exports from TyCon
+ PrimRep(..),
mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy,
mkAppTy, mkAppTys, splitAppTy, splitAppTys, splitAppTy_maybe,
- mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe, splitFunTys,
+ mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe,
+ splitFunTys, splitFunTysN,
funResultTy, funArgTy, zipFunTys, isFunTy,
- mkGenTyConApp, mkTyConApp, mkTyConTy,
+ mkTyConApp, mkTyConTy,
tyConAppTyCon, tyConAppArgs,
splitTyConApp_maybe, splitTyConApp,
- mkSynTy,
-
- repType, typePrimRep,
+ repType, typePrimRep, coreView, tcView,
mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys,
applyTy, applyTys, isForAllTy, dropForAlls,
-- Source types
- SourceType(..), sourceTypeRep, mkPredTy, mkPredTys,
+ predTypeRep, mkPredTy, mkPredTys,
-- Newtypes
- splitNewType_maybe,
+ splitRecNewType_maybe,
-- Lifting and boxity
- isUnLiftedType, isUnboxedTupleType, isAlgType, isStrictType, isPrimitiveType,
+ isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType,
+ isStrictType, isStrictPred,
-- Free variables
tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
tidyTyVarBndr, tidyFreeTyVars,
tidyOpenTyVar, tidyOpenTyVars,
tidyTopType, tidyPred,
+ tidyKind,
-- Comparison
- eqType, eqKind,
+ coreEqType, tcEqType, tcEqTypes, tcCmpType, tcCmpTypes,
+ tcEqPred, tcCmpPred, tcEqTypeX,
-- Seq
- seqType, seqTypes
-
+ seqType, seqTypes,
+
+ -- 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 TypeRep
--- Other imports:
-
-import {-# SOURCE #-} PprType( pprType ) -- Only called in debug messages
-import {-# SOURCE #-} Subst ( substTyWith )
-
-- friends:
-import Var ( Id, TyVar, tyVarKind, tyVarName, setTyVarName )
+import Kind
+import Var ( Var, TyVar, tyVarKind, tyVarName, setTyVarName, mkTyVar )
import VarEnv
import VarSet
-import Name ( NamedThing(..), mkInternalName, tidyOccName )
+import OccName ( tidyOccName )
+import Name ( NamedThing(..), mkInternalName, tidyNameOcc )
import Class ( Class, classTyCon )
import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon,
isUnboxedTupleTyCon, isUnLiftedTyCon,
- isFunTyCon, isNewTyCon, newTyConRep,
- isAlgTyCon, isSynTyCon, tyConArity,
- tyConKind, getSynTyConDefn,
- tyConPrimRep,
+ isFunTyCon, isNewTyCon, newTyConRep, newTyConRhs,
+ isAlgTyCon, tyConArity,
+ tcExpandTyCon_maybe, coreExpandTyCon_maybe,
+ tyConKind, PrimRep(..), tyConPrimRep,
)
-- others
-import CmdLineOpts ( opt_DictsStrict )
+import StaticFlags ( opt_DictsStrict )
import SrcLoc ( noSrcLoc )
-import PrimRep ( PrimRep(..) )
-import Unique ( Uniquable(..) )
-import Util ( mapAccumL, seqList, lengthIs, snocView )
+import Util ( mapAccumL, seqList, lengthIs, snocView, thenCmp, isEqual, all2 )
import Outputable
import UniqSet ( sizeUniqSet ) -- Should come via VarSet
import Maybe ( isJust )
%************************************************************************
%* *
-\subsection{Stuff to do with kinds.}
+ Type representation
%* *
%************************************************************************
+In Core, we "look through" non-recursive newtypes and PredTypes.
+
\begin{code}
-hasMoreBoxityInfo :: Kind -> Kind -> Bool
--- (k1 `hasMoreBoxityInfo` k2) checks that k1 <: k2
-hasMoreBoxityInfo k1 k2
- | k2 `eqKind` openTypeKind = isAnyTypeKind k1
- | otherwise = k1 `eqKind` k2
-
-isAnyTypeKind :: Kind -> Bool
--- True of kind * and *# and ?
-isAnyTypeKind (TyConApp tc _) = tc == typeCon || tc == openKindCon
-isAnyTypeKind (NoteTy _ k) = isAnyTypeKind k
-isAnyTypeKind other = False
-
-isTypeKind :: Kind -> Bool
--- True of kind * and *#
-isTypeKind (TyConApp tc _) = tc == typeCon
-isTypeKind (NoteTy _ k) = isTypeKind k
-isTypeKind other = False
-
-defaultKind :: Kind -> Kind
--- Used when generalising: default kind '?' to '*'
-defaultKind kind | kind `eqKind` openTypeKind = liftedTypeKind
- | otherwise = kind
+{-# 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}
mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy
getTyVar :: String -> Type -> TyVar
-getTyVar msg (TyVarTy tv) = tv
-getTyVar msg (SourceTy p) = getTyVar msg (sourceTypeRep p)
-getTyVar msg (NoteTy _ t) = getTyVar msg t
-getTyVar msg other = panic ("getTyVar: " ++ msg)
-
-getTyVar_maybe :: Type -> Maybe TyVar
-getTyVar_maybe (TyVarTy tv) = Just tv
-getTyVar_maybe (NoteTy _ t) = getTyVar_maybe t
-getTyVar_maybe (SourceTy p) = getTyVar_maybe (sourceTypeRep p)
-getTyVar_maybe other = Nothing
+getTyVar msg ty = case getTyVar_maybe ty of
+ Just tv -> tv
+ Nothing -> panic ("getTyVar: " ++ msg)
isTyVarTy :: Type -> Bool
-isTyVarTy (TyVarTy tv) = True
-isTyVarTy (NoteTy _ ty) = isTyVarTy ty
-isTyVarTy (SourceTy p) = isTyVarTy (sourceTypeRep p)
-isTyVarTy other = False
+isTyVarTy ty = isJust (getTyVar_maybe ty)
+
+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}
\begin{code}
mkAppTy orig_ty1 orig_ty2
- = ASSERT( not (isSourceTy orig_ty1) ) -- Source types are of kind *
- mk_app orig_ty1
+ = mk_app orig_ty1
where
mk_app (NoteTy _ ty1) = mk_app ty1
- mk_app (TyConApp tc tys) = mkGenTyConApp tc (tys ++ [orig_ty2])
+ mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ [orig_ty2])
mk_app ty1 = AppTy orig_ty1 orig_ty2
- -- We call mkGenTyConApp because the TyConApp could be an
+ -- 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
-- returns to (Ratio Integer), which has needlessly lost
-- the Rational part.
mkAppTys orig_ty1 orig_tys2
- = ASSERT( not (isSourceTy orig_ty1) ) -- Source types are of kind *
- mk_app orig_ty1
+ = 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
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 (NoteTy _ ty) = splitAppTy_maybe ty
-splitAppTy_maybe (SourceTy p) = splitAppTy_maybe (sourceTypeRep p)
splitAppTy_maybe (TyConApp tc tys) = case snocView tys of
- Nothing -> Nothing
+ Nothing -> Nothing
Just (tys',ty') -> Just (TyConApp tc tys', ty')
splitAppTy_maybe other = Nothing
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 (NoteTy _ ty) args = split orig_ty ty args
- split orig_ty (SourceTy p) args = split orig_ty (sourceTypeRep p) args
+ 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 (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args)
split orig_ty ty args = (orig_ty, args)
\end{code}
isFunTy ty = isJust (splitFunTy_maybe ty)
splitFunTy :: Type -> (Type, Type)
-splitFunTy (FunTy arg res) = (arg, res)
-splitFunTy (NoteTy _ ty) = splitFunTy ty
-splitFunTy (SourceTy p) = splitFunTy (sourceTypeRep p)
+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 (FunTy arg res) = Just (arg, res)
-splitFunTy_maybe (NoteTy _ ty) = splitFunTy_maybe ty
-splitFunTy_maybe (SourceTy p) = splitFunTy_maybe (sourceTypeRep p)
-splitFunTy_maybe other = Nothing
+splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty'
+splitFunTy_maybe (FunTy arg res) = Just (arg, res)
+splitFunTy_maybe other = Nothing
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 (NoteTy _ ty) = split args orig_ty ty
- split args orig_ty (SourceTy p) = split args orig_ty (sourceTypeRep p)
- 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 (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res
- split acc xs nty (NoteTy _ ty) = split acc xs nty ty
- split acc xs nty (SourceTy p) = split acc xs nty (sourceTypeRep p)
- split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> pprType orig_ty)
+ 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 (FunTy arg res) = res
-funResultTy (NoteTy _ ty) = funResultTy ty
-funResultTy (SourceTy p) = funResultTy (sourceTypeRep p)
-funResultTy ty = pprPanic "funResultTy" (pprType ty)
+funResultTy ty | Just ty' <- coreView ty = funResultTy ty'
+funResultTy (FunTy arg res) = res
+funResultTy ty = pprPanic "funResultTy" (ppr ty)
funArgTy :: Type -> Type
-funArgTy (FunTy arg res) = arg
-funArgTy (NoteTy _ ty) = funArgTy ty
-funArgTy (SourceTy p) = funArgTy (sourceTypeRep p)
-funArgTy ty = pprPanic "funArgTy" (pprType ty)
+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 SourceTy,
+@mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy,
as apppropriate.
\begin{code}
-mkGenTyConApp :: TyCon -> [Type] -> Type
-mkGenTyConApp tc tys
- | isSynTyCon tc = mkSynTy tc tys
- | otherwise = mkTyConApp tc tys
-
mkTyConApp :: TyCon -> [Type] -> Type
--- Assumes TyCon is not a SynTyCon; use mkSynTy instead for those
mkTyConApp tycon tys
| isFunTyCon tycon, [ty1,ty2] <- tys
= FunTy ty1 ty2
- | isNewTyCon tycon, -- A saturated newtype application;
- not (isRecursiveTyCon tycon), -- Not recursive (we don't use SourceTypes for them)
- tys `lengthIs` tyConArity tycon -- use the SourceType form
- = SourceTy (NType tycon tys)
-
| otherwise
- = ASSERT(not (isSynTyCon tycon))
- TyConApp tycon tys
+ = TyConApp tycon tys
mkTyConTy :: TyCon -> Type
-mkTyConTy tycon = ASSERT( not (isSynTyCon tycon) )
- TyConApp tycon []
+mkTyConTy tycon = mkTyConApp tycon []
-- splitTyConApp "looks through" synonyms, because they don't
-- mean a distinct type, but all other type-constructor applications
splitTyConApp :: Type -> (TyCon, [Type])
splitTyConApp ty = case splitTyConApp_maybe ty of
Just stuff -> stuff
- Nothing -> pprPanic "splitTyConApp" (pprType ty)
+ Nothing -> pprPanic "splitTyConApp" (ppr ty)
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 (NoteTy _ ty) = splitTyConApp_maybe ty
-splitTyConApp_maybe (SourceTy p) = splitTyConApp_maybe (sourceTypeRep p)
splitTyConApp_maybe other = Nothing
\end{code}
SynTy
~~~~~
-\begin{code}
-mkSynTy tycon tys
- | n_args == arity -- Exactly saturated
- = mk_syn tys
- | n_args > arity -- Over-saturated
- = case splitAt arity tys of { (as,bs) -> mkAppTys (mk_syn as) bs }
- -- Its important to use mkAppTys, rather than (foldl AppTy),
- -- because (mk_syn as) might well return a partially-applied
- -- type constructor; indeed, usually will!
- | otherwise -- Un-saturated
- = TyConApp tycon tys
- -- For the un-saturated case we build TyConApp directly
- -- (mkTyConApp ASSERTs that the tc isn't a SynTyCon).
- -- Here we are relying on checkValidType to find
- -- the error. What we can't do is use mkSynTy with
- -- too few arg tys, because that is utterly bogus.
-
- where
- mk_syn tys = NoteTy (SynNote (TyConApp tycon tys))
- (substTyWith tyvars tys body)
-
- (tyvars, body) = ASSERT( isSynTyCon tycon ) getSynTyConDefn tycon
- arity = tyConArity tycon
- n_args = length tys
-\end{code}
-
Notes on type synonyms
~~~~~~~~~~~~~~~~~~~~~~
The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
(b) synonyms
(c) predicates
(d) usage annotations
- (e) [recursive] newtypes
+ (e) all newtypes, including recursive ones
It's useful in the back end.
-Remember, non-recursive newtypes get expanded as part of the SourceTy case,
-but recursive ones are represented by TyConApps and have to be expanded
-by steam.
-
\begin{code}
repType :: Type -> Type
-repType (ForAllTy _ ty) = repType ty
-repType (NoteTy _ ty) = repType ty
-repType (SourceTy p) = repType (sourceTypeRep p)
-repType (TyConApp tc tys) | isNewTyCon tc && tys `lengthIs` tyConArity tc
- = repType (newTypeRep tc tys)
-repType ty = ty
-
-
+-- 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 -- ??
+ AppTy _ _ -> PtrRep -- See note below
TyVarTy _ -> PtrRep
-\end{code}
+ 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}
---------------------------------------------------------------------
splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
splitForAllTy_maybe ty = splitFAT_m ty
where
- splitFAT_m (NoteTy _ ty) = splitFAT_m ty
- splitFAT_m (SourceTy p) = splitFAT_m (sourceTypeRep p)
- splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
- splitFAT_m _ = Nothing
+ 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 (NoteTy _ ty) tvs = split orig_ty ty tvs
- split orig_ty (SourceTy p) tvs = split orig_ty (sourceTypeRep p) 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)
\begin{code}
applyTy :: Type -> Type -> Type
-applyTy (SourceTy p) arg = applyTy (sourceTypeRep p) arg
-applyTy (NoteTy _ fun) arg = applyTy fun arg
+applyTy ty arg | Just ty' <- coreView ty = applyTy ty' arg
applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty
applyTy other arg = panic "applyTy"
= substTyWith (take n_args tvs) arg_tys
(mkForAllTys (drop n_args tvs) rho_ty)
| otherwise -- Too many type args
- = ASSERT2( n_tvs > 0, pprType orig_fun_ty ) -- Zero case gives infnite loop!
+ = 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
Source types are always lifted.
-The key function is sourceTypeRep which gives the representation of a source type:
+The key function is predTypeRep which gives the representation of a source type:
\begin{code}
mkPredTy :: PredType -> Type
-mkPredTy pred = SourceTy pred
+mkPredTy pred = PredTy pred
mkPredTys :: ThetaType -> [Type]
-mkPredTys preds = map SourceTy preds
-
-sourceTypeRep :: SourceType -> Type
--- Convert a predicate to its "representation type";
--- the type of evidence for that predicate, which is actually passed at runtime
-sourceTypeRep (IParam _ ty) = ty
-sourceTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
- -- Note the mkTyConApp; the classTyCon might be a newtype!
-sourceTypeRep (NType tc tys) = newTypeRep tc tys
- -- ToDo: Consider caching this substitution in a NType
-
-isSourceTy :: Type -> Bool
-isSourceTy (NoteTy _ ty) = isSourceTy ty
-isSourceTy (SourceTy sty) = True
-isSourceTy _ = False
-
-
-splitNewType_maybe :: Type -> Maybe Type
--- Newtypes that are recursive are reprsented by TyConApp, just
--- as they always were. Occasionally we want to find their representation type.
--- NB: remember that in this module, non-recursive newtypes are transparent
-
-splitNewType_maybe ty
- = case splitTyConApp_maybe ty of
- Just (tc,tys) | isNewTyCon tc -> ASSERT( tys `lengthIs` tyConArity tc )
- -- The assert should hold because repType should
- -- only be applied to *types* (of kind *)
- Just (newTypeRep tc tys)
- other -> Nothing
-
--- A local helper function (not exported)
-newTypeRep new_tycon tys = case newTyConRep new_tycon of
- (tvs, rep_ty) -> substTyWith tvs tys rep_ty
+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}
+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}
typeKind :: Type -> Kind
typeKind (TyVarTy tyvar) = tyVarKind tyvar
-typeKind (TyConApp tycon tys) = foldr (\_ k -> funResultTy k) (tyConKind tycon) tys
+typeKind (TyConApp tycon tys) = foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
typeKind (NoteTy _ ty) = typeKind ty
-typeKind (SourceTy _) = liftedTypeKind -- Predicates are always
+typeKind (PredTy _) = liftedTypeKind -- Predicates are always
-- represented by lifted types
-typeKind (AppTy fun arg) = funResultTy (typeKind fun)
-
-typeKind (FunTy arg res) = fix_up (typeKind res)
- where
- fix_up (TyConApp tycon _) | tycon == typeCon
- || tycon == openKindCon = liftedTypeKind
- fix_up (NoteTy _ kind) = fix_up kind
- fix_up kind = kind
- -- The basic story is
- -- typeKind (FunTy arg res) = typeKind res
- -- But a function is lifted regardless of its result type
- -- Hence the strange fix-up.
- -- Note that 'res', being the result of a FunTy, can't have
- -- a strange kind like (*->*).
-
+typeKind (AppTy fun arg) = kindFunResult (typeKind fun)
+typeKind (FunTy arg res) = liftedTypeKind
typeKind (ForAllTy tv ty) = typeKind ty
\end{code}
~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
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 (NoteTy (FTVNote tvs) ty2) = tvs
-tyVarsOfType (NoteTy (SynNote ty1) ty2) = tyVarsOfType ty2 -- See note [Syn] below
-tyVarsOfType (SourceTy sty) = tyVarsOfSourceType sty
+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) = tyVarsOfType ty `minusVarSet` unitVarSet tyvar
-
--- Note [Syn]
--- Consider
--- type T a = Int
--- What are the free tyvars of (T x)? Empty, of course!
--- Here's the example that Ralf Laemmel showed me:
--- foo :: (forall a. C u a -> C u a) -> u
--- mappend :: Monoid u => u -> u -> u
---
--- bar :: Monoid u => u
--- bar = foo (\t -> t `mappend` t)
--- We have to generalise at the arg to f, and we don't
--- want to capture the constraint (Monad (C u a)) because
--- it appears to mention a. Pretty silly, but it was useful to him.
-
+tyVarsOfType (ForAllTy tyvar ty) = delVarSet (tyVarsOfType ty) tyvar
tyVarsOfTypes :: [Type] -> TyVarSet
tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
tyVarsOfPred :: PredType -> TyVarSet
-tyVarsOfPred = tyVarsOfSourceType -- Just a subtype
-
-tyVarsOfSourceType :: SourceType -> TyVarSet
-tyVarsOfSourceType (IParam _ ty) = tyVarsOfType ty
-tyVarsOfSourceType (ClassP _ tys) = tyVarsOfTypes tys
-tyVarsOfSourceType (NType _ tys) = tyVarsOfTypes tys
+tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
+tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
tyVarsOfTheta :: ThetaType -> TyVarSet
-tyVarsOfTheta = foldr (unionVarSet . tyVarsOfSourceType) emptyVarSet
+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 (tyVarsOfType ty)) ty
\end{code}
+
%************************************************************************
%* *
\subsection{TidyType}
tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
tidyTyVarBndr (tidy_env, subst) tyvar
= case tidyOccName tidy_env (getOccName name) of
- (tidy', occ') -> -- New occname reqd
- ((tidy', subst'), tyvar')
+ (tidy', occ') -> ((tidy', subst'), tyvar')
where
subst' = extendVarEnv subst tyvar tyvar'
tyvar' = setTyVarName tyvar name'
- name' = mkInternalName (getUnique name) occ' noSrcLoc
- -- Note: make a *user* tyvar, so it printes nicely
- -- Could extract src loc, but no need.
+ name' = tidyNameOcc name occ'
where
name = tyVarName tyvar
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 (SourceTy sty) = SourceTy (tidySourceType env sty)
+ 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 (SynNote ty) = SynNote $! (go ty)
go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
tidyTypes env tys = map (tidyType env) tys
-tidyPred :: TidyEnv -> SourceType -> SourceType
-tidyPred = tidySourceType
-
-tidySourceType :: TidyEnv -> SourceType -> SourceType
-tidySourceType env (IParam n ty) = IParam n (tidyType env ty)
-tidySourceType env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
-tidySourceType env (NType tc tys) = NType tc (tidyTypes 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}
\end{code}
+%************************************************************************
+%* *
+ Tidying Kinds
+%* *
+%************************************************************************
+
+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
+
+\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
+
+tidyKind env k = (env, k) -- Atomic kinds
+\end{code}
+
%************************************************************************
%* *
-- They are pretty bogus types, mind you. It would be better never to
-- construct them
-isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
-isUnLiftedType (NoteTy _ ty) = isUnLiftedType ty
-isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
-isUnLiftedType (SourceTy _) = False -- All source types are lifted
-isUnLiftedType other = False
+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
which is below TcType in the hierarchy, so it's convenient to put it here.
\begin{code}
-isStrictType (ForAllTy tv ty) = isStrictType ty
-isStrictType (NoteTy _ ty) = isStrictType ty
-isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
-isStrictType (SourceTy (ClassP clas _)) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
+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.]
-isStrictType other = False
\end{code}
\begin{code}
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 (SourceTy p) = seqPred p
+seqType (PredTy p) = seqPred p
seqType (TyConApp tc tys) = tc `seq` seqTypes tys
seqType (ForAllTy tv ty) = tv `seq` seqType ty
seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
seqNote :: TyNote -> ()
-seqNote (SynNote ty) = seqType ty
seqNote (FTVNote set) = sizeUniqSet set `seq` ()
-seqPred :: SourceType -> ()
+seqPred :: PredType -> ()
seqPred (ClassP c tys) = c `seq` seqTypes tys
-seqPred (NType tc tys) = tc `seq` seqTypes tys
seqPred (IParam n ty) = n `seq` seqType ty
\end{code}
%************************************************************************
%* *
-\subsection{Equality on types}
+ Equality for Core types
+ (We don't use instances so that we know where it happens)
%* *
%************************************************************************
-Comparison; don't use instances so that we know where it happens.
-Look through newtypes but not usage types.
+Note that eqType works right even for partial applications of newtypes.
+See Note [Newtype eta] in TyCon.lhs
-Note that eqType can respond 'False' for partial applications of newtypes.
-Consider
- newtype Parser m a = MkParser (Foogle m a)
+\begin{code}
+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}
-Does
- Monad (Parser m) `eqType` Monad (Foogle m)
-Well, yes, but eqType won't see that they are the same.
-I don't think this is harmful, but it's soemthing to watch out for.
+%************************************************************************
+%* *
+ Comparision for source types
+ (We don't use instances so that we know where it happens)
+%* *
+%************************************************************************
+
+Note that
+ tcEqType, tcCmpType
+do *not* look through newtypes, PredTypes
+
+\begin{code}
+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
+
+tcCmpTypes :: [Type] -> [Type] -> Ordering
+tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2
+
+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
+ 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
+
+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 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}
-eqType t1 t2 = eq_ty emptyVarEnv t1 t2
-eqKind = eqType -- No worries about looking
-
--- Look through Notes
-eq_ty env (NoteTy _ t1) t2 = eq_ty env t1 t2
-eq_ty env t1 (NoteTy _ t2) = eq_ty env t1 t2
-
--- Look through SourceTy. This is where the looping danger comes from
-eq_ty env (SourceTy sty1) t2 = eq_ty env (sourceTypeRep sty1) t2
-eq_ty env t1 (SourceTy sty2) = eq_ty env t1 (sourceTypeRep sty2)
-
--- The rest is plain sailing
-eq_ty env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
- Just tv1a -> tv1a == tv2
- Nothing -> tv1 == tv2
-eq_ty env (ForAllTy tv1 t1) (ForAllTy tv2 t2)
- | tv1 == tv2 = eq_ty (delVarEnv env tv1) t1 t2
- | otherwise = eq_ty (extendVarEnv env tv1 tv2) t1 t2
-eq_ty env (AppTy s1 t1) (AppTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
-eq_ty env (FunTy s1 t1) (FunTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
-eq_ty env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 == tc2) && (eq_tys env tys1 tys2)
-eq_ty env t1 t2 = False
-
-eq_tys env [] [] = True
-eq_tys env (t1:tys1) (t2:tys2) = (eq_ty env t1 t2) && (eq_tys env tys1 tys2)
-eq_tys env tys1 tys2 = False
+instance Eq PredType where { (==) = tcEqPred }
+instance Ord PredType where { compare = tcCmpPred }
\end{code}
+
+%************************************************************************
+%* *
+ 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}
+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