| otherwise
= do { dfun_name <- new_dfun_name cls tycon
; loc <- getSrcSpanM
- ; let ordinary_constraints_simple
+ ; let ordinary_constraints
= [ mkClassPred cls [arg_ty]
| data_con <- tyConDataCons rep_tc,
arg_ty <- ASSERT( isVanillaDataCon data_con )
- dataConInstOrigArgTys data_con rep_tc_args,
+ get_constrained_tys $
+ substTys subst $
+ dataConInstOrigArgTys data_con all_rep_tc_args,
not (isUnLiftedType arg_ty) ]
-- No constraints for unlifted types
-- Where they are legal we generate specilised function calls
- -- constraints on all subtypes for classes like Functor
- ordinary_constraints_deep
- = [ mkClassPred cls [deept_ty]
- | data_con <- tyConDataCons rep_tc,
- arg_ty <- ASSERT( isVanillaDataCon data_con )
- dataConInstOrigArgTys data_con (rep_tc_args++[mkTyVarTy dummy_ty]),
- deept_ty <- deepSubtypesContaining dummy_ty arg_ty,
- not (isUnLiftedType deept_ty) ]
- where dummy_ty = last (tyConTyVars tycon) -- don't substitute the last var, this might not be a good idea
-
- ordinary_constraints
- | getUnique cls == functorClassKey = ordinary_constraints_deep
- | getUnique cls == foldableClassKey = ordinary_constraints_deep
- | getUnique cls == traversableClassKey = ordinary_constraints_deep
- | otherwise = ordinary_constraints_simple
+ -- For functor-like classes, two things are different
+ -- (a) We recurse over argument types to generate constraints
+ -- See Functor examples in TcGenDeriv
+ -- (b) The rep_tc_args will be one short
+ is_functor_like = getUnique cls `elem` functorLikeClassKeys
+
+ get_constrained_tys :: [Type] -> [Type]
+ get_constrained_tys tys
+ | is_functor_like = concatMap (deepSubtypesContaining last_tv) tys
+ | otherwise = tys
+
+ rep_tc_tvs = tyConTyVars rep_tc
+ last_tv = last rep_tc_tvs
+ all_rep_tc_args | is_functor_like = rep_tc_args ++ [mkTyVarTy last_tv]
+ | otherwise = rep_tc_args
+
-- See Note [Superclasses of derived instance]
sc_constraints = substTheta (zipOpenTvSubst (classTyVars cls) inst_tys)
(classSCTheta cls)
inst_tys = [mkTyConApp tycon tc_args]
-
- nonfree_tycon_vars = dropTail (classArity cls) (tyConTyVars rep_tc)
- stupid_subst = zipTopTvSubst nonfree_tycon_vars rep_tc_args
- stupid_constraints = substTheta stupid_subst (tyConStupidTheta rep_tc)
+ subst = zipTopTvSubst rep_tc_tvs all_rep_tc_args
+ stupid_constraints = substTheta subst (tyConStupidTheta rep_tc)
all_constraints = stupid_constraints ++ sc_constraints ++ ordinary_constraints
, ds_theta = mtheta `orElse` all_constraints
, ds_newtype = False }
- ; return (if isJust mtheta then Right spec -- Specified context
+ ; ASSERT2( equalLength rep_tc_tvs all_rep_tc_args, ppr cls <+> ppr tycon )
+ return (if isJust mtheta then Right spec -- Specified context
else Left spec) } -- Infer context
mk_typeable_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta
sideConditions :: Class -> Maybe Condition
sideConditions cls
- | cls_key == eqClassKey = Just cond_std
- | cls_key == ordClassKey = Just cond_std
- | cls_key == showClassKey = Just cond_std
- | cls_key == readClassKey = Just (cond_std `andCond` cond_noUnliftedArgs)
- | cls_key == enumClassKey = Just (cond_std `andCond` cond_isEnumeration)
- | cls_key == ixClassKey = Just (cond_std `andCond` cond_enumOrProduct)
- | cls_key == boundedClassKey = Just (cond_std `andCond` cond_enumOrProduct)
- | cls_key == dataClassKey = Just (cond_mayDeriveDataTypeable `andCond` cond_std `andCond` cond_noUnliftedArgs)
- | cls_key == functorClassKey = Just (cond_mayDeriveFunctor `andCond` cond_std `andCond` cond_functorOK True)
- | cls_key == foldableClassKey = Just (cond_mayDeriveFunctor `andCond` cond_std `andCond` cond_functorOK False)
- | cls_key == traversableClassKey = Just (cond_mayDeriveFunctor `andCond` cond_std `andCond` cond_functorOK False)
+ | cls_key == eqClassKey = Just cond_std
+ | cls_key == ordClassKey = Just cond_std
+ | cls_key == showClassKey = Just cond_std
+ | cls_key == readClassKey = Just (cond_std `andCond` cond_noUnliftedArgs)
+ | cls_key == enumClassKey = Just (cond_std `andCond` cond_isEnumeration)
+ | cls_key == ixClassKey = Just (cond_std `andCond` cond_enumOrProduct)
+ | cls_key == boundedClassKey = Just (cond_std `andCond` cond_enumOrProduct)
+ | cls_key == dataClassKey = Just (cond_mayDeriveDataTypeable `andCond` cond_std `andCond` cond_noUnliftedArgs)
+ | cls_key == functorClassKey = Just (cond_std `andCond` cond_functorOK True)
+ | cls_key == foldableClassKey = Just (cond_std `andCond` cond_functorOK False)
+ | cls_key == traversableClassKey = Just (cond_std `andCond` cond_functorOK False)
| getName cls `elem` typeableClassNames = Just (cond_mayDeriveDataTypeable `andCond` cond_typeableOK)
| otherwise = Nothing
where
fam_inst = quotes (pprSourceTyCon rep_tc) <+>
ptext (sLit "is a type family")
+
+functorLikeClassKeys :: [Unique]
+functorLikeClassKeys = [functorClassKey, foldableClassKey, traversableClassKey]
+
cond_functorOK :: Bool -> Condition
-- OK for Functor class
-- Currently: (a) at least one argument
-- (b) don't use argument contravariantly
-- (c) don't use argument in the wrong place, e.g. data T a = T (X a a)
-- (d) optionally: don't use function types
-cond_functorOK allowFunctions (_, rep_tc) = msum (map check con_types)
+cond_functorOK allowFunctions (dflags, rep_tc)
+ | not (dopt Opt_DeriveFunctor dflags)
+ = Just (ptext (sLit "You need -XDeriveFunctor to derive an instance for this class"))
+ | otherwise
+ = msum (map check con_types)
where
data_cons = tyConDataCons rep_tc
con_types = concatMap dataConOrigArgTys data_cons
where
why = ptext (sLit "You need -XDeriveDataTypeable to derive an instance for this class")
-cond_mayDeriveFunctor :: Condition
-cond_mayDeriveFunctor (dflags, _)
- | dopt Opt_DeriveFunctor dflags = Nothing
- | otherwise = Just why
- where
- why = ptext (sLit "You need -XDeriveFunctor to derive an instance for this class")
-
std_class_via_iso :: Class -> Bool
std_class_via_iso clas -- These standard classes can be derived for a newtype
-- using the isomorphism trick *even if no -fglasgow-exts*
- = classKey clas `elem` [eqClassKey, ordClassKey, ixClassKey, boundedClassKey]
+ = classKey clas `elem` [eqClassKey, ordClassKey, ixClassKey, boundedClassKey]
-- Not Read/Show because they respect the type
-- Not Enum, because newtypes are never in Enum
What about types with more than one type parameter? In general, we only
derive Functor for the last position:
- data S a b = S1 [b] | S2 a
+ data S a b = S1 [b] | S2 (a, T a b)
instance Functor (S a) where
- fmap f (S1 bs) = S1 (fmap f bs)
- fmap f (S2 a) = S2 a
+ fmap f (S1 bs) = S1 (fmap f bs)
+ fmap f (S2 (p,q)) = S2 (a, fmap f q)
However, we have special cases for
- tuples
-> a -- ^ Case: the variable itself, contravariantly
-> (a -> a -> a) -- ^ Case: function type
-> (Boxity -> [a] -> a) -- ^ Case: tuple type
- -> (Type -> a -> a) -- ^ Case: other tycon, variable only in last argument
- -> a -- ^ Case: other tycon, variable only in last argument
+ -> (Type -> a -> a) -- ^ Case: type app, variable only in last argument
+ -> a -- ^ Case: type app, variable other than in last argument
-> (TcTyVar -> a -> a) -- ^ Case: forall type
-> TcTyVar -- ^ Variable to look for
-> Type -- ^ Type to process
go co (FunTy x y) | xc || yc = (caseFun xr yr,True)
where (xr,xc) = go (not co) x
(yr,yc) = go co y
- go co (AppTy x y) | xc = (caseWrongArg,True)
- | yc = (caseTyApp x yr,True)
+ go co (AppTy x y) | xc = (caseWrongArg, True)
+ | yc = (caseTyApp x yr, True)
where (_, xc) = go co x
(yr,yc) = go co y
go co ty@(TyConApp con args)
- | isTupleTyCon con = (caseTuple (tupleTyConBoxity con) xrs,True)
- | null args = (caseTrivial,False)
- | or (init xcs) = (caseWrongArg,True)
- | (last xcs) = (caseTyApp (fst (splitAppTy ty)) (last xrs),True)
+ | isTupleTyCon con = (caseTuple (tupleTyConBoxity con) xrs,True)
+ | null args = (caseTrivial,False) -- T
+ | or (init xcs) = (caseWrongArg,True) -- T (..var..) ty
+ | last xcs = -- T (..no var..) ty
+ (caseTyApp (fst (splitAppTy ty)) (last xrs),True)
where (xrs,xcs) = unzip (map (go co) args)
go co (ForAllTy v x) | v /= var && xc = (caseForAll v xr,True)
where (xr,xc) = go co x
- go _ _ = (caseTrivial,False)
+ go _ _ = (caseTrivial,False)
--- return all subtypes of ty that contain var somewhere
--- these are the things that should appear in instance constraints
+-- Return all syntactic subterms of ty that contain var somewhere
+-- These are the things that should appear in instance constraints
deepSubtypesContaining :: TcTyVar -> TcType -> [TcType]
deepSubtypesContaining = functorLikeTraverse
[]
projects / ghc-hetmet.git / commitdiff