\begin{code}
module Type (
- -- re-exports from TypeRep:
- Type, PredType, TauType, 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,
+ -- re-exports from TypeRep
+ TyThing(..), Type, PredType(..), ThetaType, TyVarSubst,
funTyCon,
- usageKindCon, -- :: KX
- usageTypeKind, -- :: KX
- usOnceTyCon, usManyTyCon, -- :: $
- usOnce, usMany, -- :: $
+ -- Re-exports from Kind
+ module Kind,
- -- exports from this module:
- hasMoreBoxityInfo, defaultKind,
mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy,
mkAppTy, mkAppTys, splitAppTy, splitAppTys, splitAppTy_maybe,
mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe, splitFunTys,
- funResultTy, funArgTy, zipFunTys,
+ funResultTy, funArgTy, zipFunTys, isFunTy,
- mkTyConApp, mkTyConTy,
+ mkGenTyConApp, mkTyConApp, mkTyConTy,
tyConAppTyCon, tyConAppArgs,
splitTyConApp_maybe, splitTyConApp,
- mkUTy, splitUTy, splitUTy_maybe,
- isUTy, uaUTy, unUTy, liftUTy, mkUTyM,
- isUsageKind, isUsage, isUTyVar,
-
mkSynTy,
- repType, splitRepFunTys, typePrimRep,
+ repType, typePrimRep,
mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys,
- applyTy, applyTys, isForAllTy,
+ 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,
- usageAnnOfType, typeKind, addFreeTyVars,
+ typeKind, addFreeTyVars,
-- Tidying up for printing
tidyType, tidyTypes,
tidyTopType, tidyPred,
-- Comparison
- eqType, eqKind, eqUsage,
+ eqType,
-- Seq
- seqType, seqTypes
+ seqType, seqTypes,
+ -- Pretty-printing
+ pprType, pprParendType,
+ pprPred, pprTheta, pprThetaArrow, pprClassPred
) where
#include "HsVersions.h"
-- Other imports:
-import {-# SOURCE #-} PprType( pprType ) -- Only called in debug messages
import {-# SOURCE #-} Subst ( substTyWith )
-- friends:
-import Var ( Var, TyVar, tyVarKind, tyVarName, setTyVarName )
+import Kind
+import Var ( TyVar, tyVarKind, tyVarName, setTyVarName )
import VarEnv
import VarSet
-import Name ( NamedThing(..), mkLocalName, tidyOccName )
-import Class ( classTyCon )
+import Name ( NamedThing(..), mkInternalName, tidyOccName )
+import Class ( Class, classTyCon )
import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon,
isUnboxedTupleTyCon, isUnLiftedTyCon,
isFunTyCon, isNewTyCon, newTyConRep,
-- others
import CmdLineOpts ( opt_DictsStrict )
-import Maybes ( maybeToBool )
import SrcLoc ( noSrcLoc )
import PrimRep ( PrimRep(..) )
import Unique ( Uniquable(..) )
-import Util ( mapAccumL, seqList, lengthIs )
+import Util ( mapAccumL, seqList, lengthIs, snocView )
import Outputable
import UniqSet ( sizeUniqSet ) -- Should come via VarSet
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection{Stuff to do with kinds.}
-%* *
-%************************************************************************
-
-\begin{code}
-hasMoreBoxityInfo :: Kind -> Kind -> Bool
-hasMoreBoxityInfo k1 k2
- | k2 `eqKind` openTypeKind = True
- | otherwise = k1 `eqType` k2
-
-defaultKind :: Kind -> Kind
--- Used when generalising: default kind '?' to '*'
-defaultKind kind | kind `eqKind` openTypeKind = liftedTypeKind
- | otherwise = kind
-
-isTypeKind :: Kind -> Bool
--- True of kind * and *#
-isTypeKind k = case splitTyConApp_maybe k of
- Just (tc,[k]) -> tc == typeCon
- other -> False
+import Maybe ( isJust )
\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 ty@(UsageTy _ _) = pprPanic "getTyVar: UTy:" (text msg $$ pprType ty)
-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 ty@(UsageTy _ _) = pprPanic "getTyVar_maybe: UTy:" (pprType ty)
-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 ty@(UsageTy _ _) = pprPanic "isTyVarTy: UTy:" (pprType ty)
-isTyVarTy other = False
+isTyVarTy ty = isJust (getTyVar_maybe ty)
+
+getTyVar_maybe :: Type -> Maybe TyVar
+getTyVar_maybe (TyVarTy tv) = Just tv
+getTyVar_maybe (NoteTy _ t) = getTyVar_maybe t
+getTyVar_maybe (PredTy p) = getTyVar_maybe (predTypeRep p)
+getTyVar_maybe (NewTcApp tc tys) = getTyVar_maybe (newTypeRep tc tys)
+getTyVar_maybe other = Nothing
\end{code}
\begin{code}
mkAppTy orig_ty1 orig_ty2
- = ASSERT( not (isSourceTy orig_ty1) ) -- Source types are of kind *
- UASSERT2( not (isUTy orig_ty2), pprType orig_ty1 <+> pprType orig_ty2 )
- -- argument must be unannotated
- 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_ty2])
- mk_app ty@(UsageTy _ _) = pprPanic "mkAppTy: UTy:" (pprType ty)
+ mk_app (NewTcApp tc tys) = NewTcApp tc (tys ++ [orig_ty2])
+ mk_app (TyConApp tc tys) = mkGenTyConApp tc (tys ++ [orig_ty2])
mk_app ty1 = AppTy orig_ty1 orig_ty2
+ -- We call mkGenTyConApp because 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
-- 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 *
- UASSERT2( not (any isUTy orig_tys2), pprType orig_ty1 <+> fsep (map pprType orig_tys2) )
- -- arguments must be unannotated
- mk_app orig_ty1
+ = mk_app orig_ty1
where
mk_app (NoteTy _ ty1) = mk_app ty1
+ mk_app (NewTcApp tc tys) = NewTcApp tc (tys ++ orig_tys2)
mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2)
- mk_app ty@(UsageTy _ _) = pprPanic "mkAppTys: UTy:" (pprType ty)
+ -- Use mkTyConApp in case tc is (->)
mk_app ty1 = foldl AppTy orig_ty1 orig_tys2
splitAppTy_maybe :: Type -> Maybe (Type, Type)
-splitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [unUTy ty1], unUTy ty2)
+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 []) = Nothing
-splitAppTy_maybe (TyConApp tc tys) = split tys []
- where
- split [ty2] acc = Just (TyConApp tc (reverse acc), ty2)
- split (ty:tys) acc = split tys (ty:acc)
+splitAppTy_maybe (PredTy p) = splitAppTy_maybe (predTypeRep p)
+splitAppTy_maybe (NewTcApp tc tys) = splitAppTy_maybe (newTypeRep tc tys)
+splitAppTy_maybe (TyConApp tc tys) = case snocView tys of
+ Nothing -> Nothing
+ Just (tys',ty') -> Just (mkGenTyConApp tc tys', ty')
+ -- mkGenTyConApp just in case the tc is a newtype
-splitAppTy_maybe ty@(UsageTy _ _) = pprPanic "splitAppTy_maybe: UTy:" (pprType ty)
-splitAppTy_maybe other = Nothing
+splitAppTy_maybe other = Nothing
splitAppTy :: Type -> (Type, Type)
splitAppTy ty = case splitAppTy_maybe ty of
where
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 (PredTy p) args = split orig_ty (predTypeRep p) args
+ split orig_ty (NewTcApp tc tc_args) args = split orig_ty (newTypeRep tc tc_args) args
+ split orig_ty (TyConApp tc tc_args) args = (mkGenTyConApp tc [], tc_args ++ args)
+ -- mkGenTyConApp just in case the tc is a newtype
split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
- (TyConApp funTyCon [], [unUTy ty1,unUTy ty2])
- split orig_ty (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args)
- split orig_ty (UsageTy _ _) args = pprPanic "splitAppTys: UTy:" (pprType orig_ty)
+ (TyConApp funTyCon [], [ty1,ty2])
split orig_ty ty args = (orig_ty, args)
\end{code}
\begin{code}
mkFunTy :: Type -> Type -> Type
-mkFunTy arg res = UASSERT2( isUTy arg && isUTy res, pprType arg <+> pprType res )
- FunTy arg res
+mkFunTy arg res = FunTy arg res
mkFunTys :: [Type] -> Type -> Type
-mkFunTys tys ty = UASSERT2( all isUTy (ty:tys), fsep (map pprType (tys++[ty])) )
- foldr FunTy ty tys
+mkFunTys tys ty = foldr FunTy ty tys
+
+isFunTy :: Type -> Bool
+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@(UsageTy _ _) = pprPanic "splitFunTy: UTy:" (pprType ty)
+splitFunTy (FunTy arg res) = (arg, res)
+splitFunTy (NoteTy _ ty) = splitFunTy ty
+splitFunTy (PredTy p) = splitFunTy (predTypeRep p)
+splitFunTy (NewTcApp tc tys) = splitFunTy (newTypeRep tc tys)
+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 ty@(UsageTy _ _) = pprPanic "splitFunTy_maybe: UTy:" (pprType ty)
-splitFunTy_maybe other = Nothing
+splitFunTy_maybe (FunTy arg res) = Just (arg, res)
+splitFunTy_maybe (NoteTy _ ty) = splitFunTy_maybe ty
+splitFunTy_maybe (PredTy p) = splitFunTy_maybe (predTypeRep p)
+splitFunTy_maybe (NewTcApp tc tys) = splitFunTy_maybe (newTypeRep tc tys)
+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 (UsageTy _ _) = pprPanic "splitFunTys: UTy:" (pprType orig_ty)
- split args orig_ty ty = (reverse args, orig_ty)
+ 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 (PredTy p) = split args orig_ty (predTypeRep p)
+ split args orig_ty (NewTcApp tc tys) = split args orig_ty (newTypeRep tc tys)
+ split args orig_ty ty = (reverse args, orig_ty)
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 xs nty (UsageTy _ _) = pprPanic "zipFunTys: UTy:" (ppr orig_xs <+> pprType orig_ty)
- split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> pprType orig_ty)
+ 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 (PredTy p) = split acc xs nty (predTypeRep p)
+ split acc xs nty (NewTcApp tc tys) = split acc xs nty (newTypeRep tc tys)
+ 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 (UsageTy _ ty) = funResultTy ty
-funResultTy ty = pprPanic "funResultTy" (pprType ty)
+funResultTy (FunTy arg res) = res
+funResultTy (NoteTy _ ty) = funResultTy ty
+funResultTy (PredTy p) = funResultTy (predTypeRep p)
+funResultTy (NewTcApp tc tys) = funResultTy (newTypeRep tc tys)
+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 (UsageTy _ ty) = funArgTy ty
-funArgTy ty = pprPanic "funArgTy" (pprType ty)
+funArgTy (FunTy arg res) = arg
+funArgTy (NoteTy _ ty) = funArgTy ty
+funArgTy (PredTy p) = funArgTy (predTypeRep p)
+funArgTy (NewTcApp tc tys) = funArgTy (newTypeRep tc tys)
+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 (mkUTyM ty1) (mkUTyM ty2)
+ = 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)
+ | isNewTyCon tycon
+ = NewTcApp tycon tys
| otherwise
= ASSERT(not (isSynTyCon tycon))
- UASSERT2( not (any isUTy tys), ppr tycon <+> fsep (map pprType 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 (TyConApp tc tys) = Just (tc, tys)
-splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [unUTy arg,unUTy res])
+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 (UsageTy _ ty) = splitTyConApp_maybe ty
+splitTyConApp_maybe (PredTy p) = splitTyConApp_maybe (predTypeRep p)
+splitTyConApp_maybe (NewTcApp tc tys) = splitTyConApp_maybe (newTypeRep tc tys)
splitTyConApp_maybe other = Nothing
\end{code}
| n_args == arity -- Exactly saturated
= mk_syn tys
| n_args > arity -- Over-saturated
- = case splitAt arity tys of { (as,bs) -> foldl AppTy (mk_syn as) bs }
+ = 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
Representation types
~~~~~~~~~~~~~~~~~~~~
-
repType looks through
(a) for-alls, and
(b) synonyms
(e) [recursive] newtypes
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
+-- Only applied to types of kind *; hence tycons are saturated
repType (ForAllTy _ ty) = repType ty
repType (NoteTy _ ty) = repType ty
-repType (SourceTy p) = repType (sourceTypeRep p)
-repType (UsageTy _ ty) = repType ty
-repType (TyConApp tc tys) | isNewTyCon tc && tys `lengthIs` tyConArity tc
- = repType (newTypeRep tc tys)
+repType (PredTy p) = repType (predTypeRep p)
+repType (NewTcApp tc tys) = ASSERT( tys `lengthIs` tyConArity tc )
+ repType (new_type_rep tc tys)
repType ty = ty
-splitRepFunTys :: Type -> ([Type], Type)
--- Like splitFunTys, but looks through newtypes and for-alls
-splitRepFunTys ty = split [] (repType ty)
- where
- split args (FunTy arg res) = split (arg:args) (repType res)
- split args ty = (reverse args, ty)
typePrimRep :: Type -> PrimRep
typePrimRep ty = case repType ty of
FunTy _ _ -> PtrRep
AppTy _ _ -> PtrRep -- ??
TyVarTy _ -> PtrRep
+ other -> pprPanic "typePrimRep" (ppr ty)
\end{code}
= mkForAllTys [tyvar] ty
mkForAllTys :: [TyVar] -> Type -> Type
-mkForAllTys tyvars ty
- = case splitUTy_maybe ty of
- Just (u,ty1) -> UASSERT2( not (mkVarSet tyvars `intersectsVarSet` tyVarsOfType u),
- ptext SLIT("mkForAllTys: usage scope")
- <+> ppr tyvars <+> pprType ty )
- mkUTy u (foldr ForAllTy ty1 tyvars) -- we lift usage annotations over foralls
- Nothing -> foldr ForAllTy ty tyvars
+mkForAllTys tyvars ty = foldr ForAllTy ty tyvars
isForAllTy :: Type -> Bool
isForAllTy (NoteTy _ ty) = isForAllTy ty
isForAllTy (ForAllTy _ _) = True
-isForAllTy (UsageTy _ ty) = isForAllTy ty
isForAllTy other_ty = False
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 (PredTy p) = splitFAT_m (predTypeRep p)
+ splitFAT_m (NewTcApp tc tys) = splitFAT_m (newTypeRep tc tys)
splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
- splitFAT_m (UsageTy _ ty) = splitFAT_m 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 (UsageTy _ ty) tvs = split orig_ty ty tvs
- split orig_ty t tvs = (reverse tvs, orig_ty)
+ 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 (PredTy p) tvs = split orig_ty (predTypeRep p) tvs
+ split orig_ty (NewTcApp tc tys) tvs = split orig_ty (newTypeRep tc tys) tvs
+ split orig_ty t tvs = (reverse tvs, orig_ty)
+
+dropForAlls :: Type -> Type
+dropForAlls ty = snd (splitForAllTys ty)
\end{code}
-- (mkPiType now in CoreUtils)
-Applying a for-all to its arguments. Lift usage annotation as required.
+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 :: Type -> Type -> Type
-applyTy (SourceTy p) arg = applyTy (sourceTypeRep p) arg
-applyTy (NoteTy _ fun) arg = applyTy fun arg
-applyTy (ForAllTy tv ty) arg = UASSERT2( not (isUTy arg),
- ptext SLIT("applyTy")
- <+> pprType ty <+> pprType arg )
- substTyWith [tv] [arg] ty
-applyTy (UsageTy u ty) arg = UsageTy u (applyTy ty arg)
-applyTy other arg = panic "applyTy"
+applyTy (PredTy p) arg = applyTy (predTypeRep p) arg
+applyTy (NewTcApp tc tys) arg = applyTy (newTypeRep tc tys) arg
+applyTy (NoteTy _ fun) arg = applyTy fun arg
+applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty
+applyTy other arg = panic "applyTy"
applyTys :: Type -> [Type] -> Type
-applyTys fun_ty arg_tys
- = UASSERT2( not (any isUTy arg_tys), ptext SLIT("applyTys") <+> pprType fun_ty )
- (case mu of
- Just u -> UsageTy u
- Nothing -> id) $
- substTyWith tvs arg_tys ty
- where
- (mu, tvs, ty) = split fun_ty arg_tys
-
- split fun_ty [] = (Nothing, [], fun_ty)
- split (NoteTy _ fun_ty) args = split fun_ty args
- split (SourceTy p) args = split (sourceTypeRep p) args
- split (ForAllTy tv fun_ty) (arg:args) = case split fun_ty args of
- (mu, tvs, ty) -> (mu, tv:tvs, ty)
- split (UsageTy u ty) args = case split ty args of
- (Nothing, tvs, ty) -> (Just u, tvs, ty)
- (Just _ , _ , _ ) -> pprPanic "applyTys:"
- (pprType fun_ty)
- split other_ty args = panic "applyTys"
-\end{code}
-
-
----------------------------------------------------------------------
- UsageTy
- ~~~~~~~
-
-Constructing and taking apart usage types.
-
-\begin{code}
-mkUTy :: Type -> Type -> Type
-mkUTy u ty
- = ASSERT2( typeKind u `eqKind` usageTypeKind,
- ptext SLIT("mkUTy:") <+> pprType u <+> pprType ty )
- UASSERT2( not (isUTy ty), ptext SLIT("mkUTy:") <+> pprType u <+> pprType ty )
- -- if u == usMany then ty else : ToDo? KSW 2000-10
-#ifdef DO_USAGES
- UsageTy u ty
-#else
- ty
-#endif
-
-splitUTy :: Type -> (Type {- :: $ -}, Type)
-splitUTy orig_ty
- = case splitUTy_maybe orig_ty of
- Just (u,ty) -> (u,ty)
-#ifdef DO_USAGES
- Nothing -> pprPanic "splitUTy:" (pprType orig_ty)
-#else
- Nothing -> (usMany,orig_ty) -- default annotation ToDo KSW 2000-10
-#endif
-
-splitUTy_maybe :: Type -> Maybe (Type {- :: $ -}, Type)
-splitUTy_maybe (UsageTy u ty) = Just (u,ty)
-splitUTy_maybe (NoteTy _ ty) = splitUTy_maybe ty
-splitUTy_maybe other_ty = Nothing
-
-isUTy :: Type -> Bool
- -- has usage annotation
-isUTy = maybeToBool . splitUTy_maybe
-
-uaUTy :: Type -> Type
- -- extract annotation
-uaUTy = fst . splitUTy
-
-unUTy :: Type -> Type
- -- extract unannotated type
-unUTy = snd . splitUTy
-\end{code}
-
-\begin{code}
-liftUTy :: (Type -> Type) -> Type -> Type
- -- lift outer usage annot over operation on unannotated types
-liftUTy f ty
- = let
- (u,ty') = splitUTy ty
- in
- mkUTy u (f ty')
-\end{code}
-
-\begin{code}
-mkUTyM :: Type -> Type
- -- put TOP (no info) annotation on unannotated type
-mkUTyM ty = mkUTy usMany ty
-\end{code}
-
-\begin{code}
-isUsageKind :: Kind -> Bool
-isUsageKind k
- = ASSERT( typeKind k `eqKind` superKind )
- k `eqKind` usageTypeKind
-
-isUsage :: Type -> Bool
-isUsage ty
- = isUsageKind (typeKind ty)
-
-isUTyVar :: Var -> Bool
-isUTyVar v
- = isUsageKind (tyVarKind v)
+-- 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}
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 n 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
+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.
+predTypeRep (IParam _ ty) = ty
+predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
+ -- Result might be a NewTcApp, but the consumer will
+ -- look through that too if necessary
+\end{code}
+
-isSourceTy :: Type -> Bool
-isSourceTy (NoteTy _ ty) = isSourceTy ty
-isSourceTy (UsageTy _ 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
+%************************************************************************
+%* *
+ NewTypes
+%* *
+%************************************************************************
+
+\begin{code}
+splitRecNewType_maybe :: Type -> Maybe Type
+-- Newtypes are always represented by a NewTcApp
+-- Sometimes we want to look through a recursive newtype, and that's what happens here
+-- Only applied to types of kind *, hence the newtype is always saturated
+splitRecNewType_maybe (NoteTy _ ty) = splitRecNewType_maybe ty
+splitRecNewType_maybe (PredTy p) = splitRecNewType_maybe (predTypeRep p)
+splitRecNewType_maybe (NewTcApp tc tys)
+ | isRecursiveTyCon tc
+ = ASSERT( tys `lengthIs` tyConArity tc && isNewTyCon tc )
+ -- The assert should hold because repType should
+ -- only be applied to *types* (of kind *)
+ Just (new_type_rep tc tys)
+splitRecNewType_maybe other = Nothing
+-----------------------------
+newTypeRep :: TyCon -> [Type] -> Type
-- A local helper function (not exported)
-newTypeRep new_tycon tys = case newTyConRep new_tycon of
- (tvs, rep_ty) -> substTyWith tvs tys rep_ty
+-- Expands a newtype application to
+-- *either* a vanilla TyConApp (recursive newtype, or non-saturated)
+-- *or* the newtype representation (otherwise)
+-- Either way, the result is not a NewTcApp
+--
+-- NB: the returned TyConApp is always deconstructed immediately by the
+-- caller... a TyConApp with a newtype type constructor never lives
+-- in an ordinary type
+newTypeRep tc tys
+ | not (isRecursiveTyCon tc), -- Not recursive and saturated
+ tys `lengthIs` tyConArity tc -- treat as equivalent to expansion
+ = new_type_rep tc tys
+ | otherwise
+ = TyConApp tc tys
+ -- ToDo: Consider caching this substitution in a NType
+
+----------------------------
+-- 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
\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 (NewTcApp 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
-typeKind (UsageTy _ ty) = typeKind ty -- we don't have separate kinds for ann/unann
\end{code}
tyVarsOfType :: Type -> TyVarSet
tyVarsOfType (TyVarTy tv) = unitVarSet tv
tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
+tyVarsOfType (NewTcApp tycon tys) = tyVarsOfTypes tys
tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
-tyVarsOfType (NoteTy (SynNote ty1) ty2) = tyVarsOfType ty1
-tyVarsOfType (SourceTy sty) = tyVarsOfSourceType sty
+tyVarsOfType (NoteTy (SynNote ty1) ty2) = tyVarsOfType ty2 -- See note [Syn] below
+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
-tyVarsOfType (UsageTy u ty) = tyVarsOfType u `unionVarSet` tyVarsOfType ty
+
+-- 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.
+
tyVarsOfTypes :: [Type] -> TyVarSet
tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
tyVarsOfPred :: PredType -> TyVarSet
-tyVarsOfPred = tyVarsOfSourceType -- Just a subtype
-
-tyVarsOfSourceType :: SourceType -> TyVarSet
-tyVarsOfSourceType (IParam n ty) = tyVarsOfType ty
-tyVarsOfSourceType (ClassP clas tys) = tyVarsOfTypes tys
-tyVarsOfSourceType (NType tc 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}
-Usage annotations of a type
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Get a list of usage annotations of a type, *in left-to-right pre-order*.
-
-\begin{code}
-usageAnnOfType :: Type -> [Type]
-usageAnnOfType ty
- = goS ty
- where
- goT (TyVarTy _) = []
- goT (AppTy ty1 ty2) = goT ty1 ++ goT ty2
- goT (TyConApp tc tys) = concatMap goT tys
- goT (FunTy sty1 sty2) = goS sty1 ++ goS sty2
- goT (ForAllTy mv ty) = goT ty
- goT (SourceTy p) = goT (sourceTypeRep p)
- goT ty@(UsageTy _ _) = pprPanic "usageAnnOfType: unexpected usage:" (pprType ty)
- goT (NoteTy note ty) = goT ty
-
- goS sty = case splitUTy sty of
- (u,tty) -> u : goT tty
-\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' = mkLocalName (getUnique name) occ' noSrcLoc
+ name' = mkInternalName (getUnique name) occ' noSrcLoc
-- Note: make a *user* tyvar, so it printes nicely
-- Could extract src loc, but no need.
where
Just tv' -> TyVarTy tv'
go (TyConApp tycon tys) = let args = map go tys
in args `seqList` TyConApp tycon args
+ go (NewTcApp tycon tys) = let args = map go tys
+ in args `seqList` NewTcApp 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 (UsageTy u ty) = (UsageTy $! (go u)) $! (go ty)
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}
-- 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 (UsageTy _ ty) = isUnLiftedType ty
-isUnLiftedType (SourceTy _) = False -- All source types are lifted
-isUnLiftedType other = False
+isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
+isUnLiftedType (NoteTy _ ty) = isUnLiftedType ty
+isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
+isUnLiftedType (PredTy _) = False -- All source types are lifted
+isUnLiftedType (NewTcApp tc tys) = isUnLiftedType (newTypeRep tc tys)
+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 (UsageTy _ ty) = isStrictType ty
-isStrictType (SourceTy (ClassP clas _)) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
+isStrictType (ForAllTy tv ty) = isStrictType ty
+isStrictType (NoteTy _ ty) = isStrictType ty
+isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
+isStrictType (NewTcApp tc tys) = isStrictType (newTypeRep tc tys)
+isStrictType (PredTy pred) = isStrictPred pred
+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 (NewTcApp tc tys) = tc `seq` seqTypes tys
seqType (ForAllTy tv ty) = tv `seq` seqType ty
-seqType (UsageTy u ty) = seqType u `seq` seqType ty
seqTypes :: [Type] -> ()
seqTypes [] = ()
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}
Comparison; don't use instances so that we know where it happens.
Look through newtypes but not usage types.
+Note that eqType can respond 'False' for partial applications of newtypes.
+Consider
+ newtype Parser m a = MkParser (Foogle m a)
+
+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.
+
\begin{code}
eqType t1 t2 = eq_ty emptyVarEnv t1 t2
-eqKind = eqType -- No worries about looking
-eqUsage = eqType -- through source types for these two
-- 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)
+-- Look through PredTy and NewTcApp. This is where the looping danger comes from.
+-- We don't bother to check for the PredType/PredType case, no good reason
+-- Hmm: maybe there is a good reason: see the notes below about newtypes
+eq_ty env (PredTy sty1) t2 = eq_ty env (predTypeRep sty1) t2
+eq_ty env t1 (PredTy sty2) = eq_ty env t1 (predTypeRep sty2)
+
+-- NB: we *cannot* short-cut the newtype comparison thus:
+-- eq_ty env (NewTcApp tc1 tys1) (NewTcApp tc2 tys2)
+-- | (tc1 == tc2) = (eq_tys env tys1 tys2)
+--
+-- Consider:
+-- newtype T a = MkT [a]
+-- newtype Foo m = MkFoo (forall a. m a -> Int)
+-- w1 :: Foo []
+-- w1 = ...
+--
+-- w2 :: Foo T
+-- w2 = MkFoo (\(MkT x) -> case w1 of MkFoo f -> f x)
+--
+-- We end up with w2 = w1; so we need that Foo T = Foo []
+-- but we can only expand saturated newtypes, so just comparing
+-- T with [] won't do.
+
+eq_ty env (NewTcApp tc1 tys1) t2 = eq_ty env (newTypeRep tc1 tys1) t2
+eq_ty env t1 (NewTcApp tc2 tys2) = eq_ty env t1 (newTypeRep tc2 tys2)
-- The rest is plain sailing
eq_ty env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
| 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 (UsageTy _ t1) (UsageTy _ t2) = 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