X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcType.lhs;h=6b326b0e32f7cf85c8f909d08d0b65b290f35cf8;hb=5479f1a02fae9141c02a7873c57af80323b0fc0d;hp=fe5ea396924950e3914ff2bc65beffc619e42ebd;hpb=654d07dd0fb679d014ac363e13c004b0086d0d6e;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcType.lhs b/compiler/typecheck/TcType.lhs index fe5ea39..6b326b0 100644 --- a/compiler/typecheck/TcType.lhs +++ b/compiler/typecheck/TcType.lhs @@ -71,7 +71,8 @@ module TcType ( getClassPredTys_maybe, getClassPredTys, isClassPred, isTyVarClassPred, isEqPred, mkDictTy, tcSplitPredTy_maybe, - isPredTy, isDictTy, tcSplitDFunTy, tcSplitDFunHead, predTyUnique, + isPredTy, isDictTy, isDictLikeTy, + tcSplitDFunTy, tcSplitDFunHead, predTyUnique, mkClassPred, isInheritablePred, isIPPred, dataConsStupidTheta, isRefineableTy, isRefineablePred, @@ -97,7 +98,7 @@ module TcType ( unliftedTypeKind, liftedTypeKind, argTypeKind, openTypeKind, mkArrowKind, mkArrowKinds, isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind, - isSubArgTypeKind, isSubKind, defaultKind, + isSubArgTypeKind, isSubKind, splitKindFunTys, defaultKind, kindVarRef, mkKindVar, Type, PredType(..), ThetaType, @@ -894,8 +895,45 @@ isDictTy :: Type -> Bool isDictTy ty | Just ty' <- tcView ty = isDictTy ty' isDictTy (PredTy p) = isClassPred p isDictTy _ = False + +isDictLikeTy :: Type -> Bool +-- Note [Dictionary-like types] +isDictLikeTy ty | Just ty' <- tcView ty = isDictTy ty' +isDictLikeTy (PredTy p) = isClassPred p +isDictLikeTy (TyConApp tc tys) + | isTupleTyCon tc = all isDictLikeTy tys +isDictLikeTy _ = False \end{code} +Note [Dictionary-like types] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Being "dictionary-like" means either a dictionary type or a tuple thereof. +In GHC 6.10 we build implication constraints which construct such tuples, +and if we land up with a binding + t :: (C [a], Eq [a]) + t = blah +then we want to treat t as cheap under "-fdicts-cheap" for example. +(Implication constraints are normally inlined, but sadly not if the +occurrence is itself inside an INLINE function! Until we revise the +handling of implication constraints, that is.) This turned out to +be important in getting good arities in DPH code. Example: + + class C a + class D a where { foo :: a -> a } + instance C a => D (Maybe a) where { foo x = x } + + bar :: (C a, C b) => a -> b -> (Maybe a, Maybe b) + {-# INLINE bar #-} + bar x y = (foo (Just x), foo (Just y)) + +Then 'bar' should jolly well have arity 4 (two dicts, two args), but +we ended up with something like + bar = __inline_me__ (\d1,d2. let t :: (D (Maybe a), D (Maybe b)) = ... + in \x,y. ) + +This is all a bit ad-hoc; eg it relies on knowing that implication +constraints build tuples. + --------------------- Implicit parameters --------------------------------- \begin{code} @@ -965,10 +1003,13 @@ isSigmaTy (FunTy a _) = isPredTy a isSigmaTy _ = False isOverloadedTy :: Type -> Bool +-- Yes for a type of a function that might require evidence-passing +-- Used only by bindInstsOfLocalFuns/Pats +-- NB: be sure to check for type with an equality predicate; hence isCoVar isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty' -isOverloadedTy (ForAllTy _ ty) = isOverloadedTy ty -isOverloadedTy (FunTy a _) = isPredTy a -isOverloadedTy _ = False +isOverloadedTy (ForAllTy tv ty) = isCoVar tv || isOverloadedTy ty +isOverloadedTy (FunTy a _) = isPredTy a +isOverloadedTy _ = False isPredTy :: Type -> Bool -- Belongs in TcType because it does -- not look through newtypes, or predtypes (of course) @@ -1259,14 +1300,19 @@ toDNType ty ] checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool - -- Look through newtypes - -- Non-recursive ones are transparent to splitTyConApp, - -- but recursive ones aren't. Manuel had: - -- newtype T = MkT (Ptr T) - -- and wanted it to work... -checkRepTyCon check_tc ty - | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc - | otherwise = False +-- Look through newtypes, but *not* foralls +-- Should work even for recursive newtypes +-- eg Manuel had: newtype T = MkT (Ptr T) +checkRepTyCon check_tc ty + = go [] ty + where + go rec_nts ty + | Just (tc,tys) <- splitTyConApp_maybe ty + = case carefullySplitNewType_maybe rec_nts tc tys of + Just (rec_nts', ty') -> go rec_nts' ty' + Nothing -> check_tc tc + | otherwise + = False checkRepTyConKey :: [Unique] -> Type -> Bool -- Like checkRepTyCon, but just looks at the TyCon key