import Outputable
import FastString
import Bag
+
+import Control.Monad
\end{code}
%************************************************************************
className cls `elem` typeableClassNames)
(derivingHiddenErr tycon)
- ; mayDeriveDataTypeable <- doptM Opt_DeriveDataTypeable
- ; newtype_deriving <- doptM Opt_GeneralizedNewtypeDeriving
-
+ ; dflags <- getDOpts
; if isDataTyCon rep_tc then
- mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys
+ mkDataTypeEqn orig dflags tvs cls cls_tys
tycon tc_args rep_tc rep_tc_args mtheta
else
- mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving
- tvs cls cls_tys
+ mkNewTypeEqn orig dflags tvs cls cls_tys
tycon tc_args rep_tc rep_tc_args mtheta }
| otherwise
= failWithTc (derivingThingErr cls cls_tys tc_app
%************************************************************************
\begin{code}
-mkDataTypeEqn :: InstOrigin -> Bool -> [Var] -> Class -> [Type]
- -> TyCon -> [Type] -> TyCon -> [Type] -> Maybe ThetaType
- -> TcRn EarlyDerivSpec -- Return 'Nothing' if error
-
-mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys
+mkDataTypeEqn :: InstOrigin
+ -> DynFlags
+ -> [Var] -- Universally quantified type variables in the instance
+ -> Class -- Class for which we need to derive an instance
+ -> [Type] -- Other parameters to the class except the last
+ -> TyCon -- Type constructor for which the instance is requested (last parameter to the type class)
+ -> [Type] -- Parameters to the type constructor
+ -> TyCon -- rep of the above (for type families)
+ -> [Type] -- rep of the above
+ -> Maybe ThetaType -- Context of the instance, for standalone deriving
+ -> TcRn EarlyDerivSpec -- Return 'Nothing' if error
+
+mkDataTypeEqn orig dflags tvs cls cls_tys
tycon tc_args rep_tc rep_tc_args mtheta
- = case checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc of
+ = case checkSideConditions dflags cls cls_tys rep_tc of
-- NB: pass the *representation* tycon to checkSideConditions
CanDerive -> mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta
NonDerivableClass -> bale_out (nonStdErr cls)
| otherwise
= do { dfun_name <- new_dfun_name cls tycon
; loc <- getSrcSpanM
- ; let ordinary_constraints
+ ; let ordinary_constraints_simple
= [ mkClassPred cls [arg_ty]
| data_con <- tyConDataCons rep_tc,
arg_ty <- ASSERT( isVanillaDataCon data_con )
-- 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
+
-- See Note [Superclasses of derived instance]
sc_constraints = substTheta (zipOpenTvSubst (classTyVars cls) inst_tys)
(classSCTheta cls)
inst_tys = [mkTyConApp tycon tc_args]
- stupid_subst = zipTopTvSubst (tyConTyVars rep_tc) rep_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)
+
all_constraints = stupid_constraints ++ sc_constraints ++ ordinary_constraints
spec = DS { ds_loc = loc, ds_orig = orig
, ds_tc = rep_tc, ds_tc_args = rep_tc_args
, ds_theta = mtheta `orElse` [], ds_newtype = False }) }
+
------------------------------------------------------------------
-- Check side conditions that dis-allow derivability for particular classes
-- This is *apart* from the newtype-deriving mechanism
| DerivableClassError SDoc -- Standard class, but can't do it
| NonDerivableClass -- Non-standard class
-checkSideConditions :: Bool -> Class -> [TcType] -> TyCon -> DerivStatus
-checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc
+checkSideConditions :: DynFlags -> Class -> [TcType] -> TyCon -> DerivStatus
+checkSideConditions dflags cls cls_tys rep_tc
| Just cond <- sideConditions cls
- = case (cond (mayDeriveDataTypeable, rep_tc)) of
+ = case (cond (dflags, rep_tc)) of
Just err -> DerivableClassError err -- Class-specific error
Nothing | null cls_tys -> CanDerive
| otherwise -> DerivableClassError ty_args_why -- e.g. deriving( Eq s )
| 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)
| getName cls `elem` typeableClassNames = Just (cond_mayDeriveDataTypeable `andCond` cond_typeableOK)
| otherwise = Nothing
where
cls_key = getUnique cls
-type Condition = (Bool, TyCon) -> Maybe SDoc
- -- Bool is whether or not we are allowed to derive Data and Typeable
+type Condition = (DynFlags, TyCon) -> Maybe SDoc
+ -- first Bool is whether or not we are allowed to derive Data and Typeable
+ -- second Bool is whether or not we are allowed to derive Functor
-- TyCon is the *representation* tycon if the
-- data type is an indexed one
-- Nothing => OK
fam_inst = quotes (pprSourceTyCon rep_tc) <+>
ptext (sLit "is a type family")
+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)
+ where
+ data_cons = tyConDataCons rep_tc
+ con_types = concatMap dataConOrigArgTys data_cons
+ check = functorLikeTraverse
+ Nothing
+ Nothing
+ (Just covariant)
+ (\x y -> if allowFunctions then x `mplus` y else Just functions)
+ (\_ xs -> msum xs)
+ (\_ x -> x)
+ (Just wrong_arg)
+ (\_ x -> x)
+ (last (tyConTyVars rep_tc))
+ covariant = quotes (pprSourceTyCon rep_tc) <+>
+ ptext (sLit "uses the type variable in a function argument")
+ functions = quotes (pprSourceTyCon rep_tc) <+>
+ ptext (sLit "contains function types")
+ wrong_arg = quotes (pprSourceTyCon rep_tc) <+>
+ ptext (sLit "uses the type variable in an argument other than the last")
+
cond_mayDeriveDataTypeable :: Condition
-cond_mayDeriveDataTypeable (mayDeriveDataTypeable, _)
- | mayDeriveDataTypeable = Nothing
+cond_mayDeriveDataTypeable (dflags, _)
+ | dopt Opt_DeriveDataTypeable dflags = Nothing
| otherwise = Just why
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*
%************************************************************************
\begin{code}
-mkNewTypeEqn :: InstOrigin -> Bool -> Bool -> [Var] -> Class
+mkNewTypeEqn :: InstOrigin -> DynFlags -> [Var] -> Class
-> [Type] -> TyCon -> [Type] -> TyCon -> [Type]
-> Maybe ThetaType
-> TcRn EarlyDerivSpec
-mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs
+mkNewTypeEqn orig dflags tvs
cls cls_tys tycon tc_args rep_tycon rep_tc_args mtheta
-- Want: instance (...) => cls (cls_tys ++ [tycon tc_args]) where ...
| can_derive_via_isomorphism && (newtype_deriving || std_class_via_iso cls)
| newtype_deriving -> bale_out cant_derive_err -- Too hard, even with newtype deriving
| otherwise -> bale_out non_std_err -- Try newtype deriving!
where
- check_conditions = checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tycon
+ newtype_deriving = dopt Opt_GeneralizedNewtypeDeriving dflags
+ check_conditions = checkSideConditions dflags cls cls_tys rep_tycon
bale_out msg = failWithTc (derivingThingErr cls cls_tys inst_ty msg)
non_std_err = nonStdErr cls $$
,(showClassKey, gen_Show_binds fix_env)
,(readClassKey, gen_Read_binds fix_env)
,(dataClassKey, gen_Data_binds)
+ ,(functorClassKey, gen_Functor_binds)
+ ,(foldableClassKey, gen_Foldable_binds)
+ ,(traversableClassKey, gen_Traversable_binds)
]
\end{code}
projects / ghc-hetmet.git / blobdiff