#include "HsVersions.h"
-import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..),
- collectMonoBinders )
+import HsSyn ( HsBinds(..), TyClDecl(..), MonoBinds(..),
+ andMonoBindList, collectMonoBinders )
import RdrHsSyn ( RdrNameMonoBinds )
-import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPred )
+import RnHsSyn ( RenamedHsBinds, RenamedTyClDecl, RenamedHsPred )
import CmdLineOpts ( DynFlag(..) )
import TcRnMonad
import MkId ( mkDictFunId )
import DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon )
import Maybes ( maybeToBool, catMaybes )
-import Name ( Name, getSrcLoc, nameUnique )
+import Name ( Name, getSrcLoc )
+import Unique ( Unique, getUnique )
import NameSet
import RdrName ( RdrName )
import TyCon ( tyConTyVars, tyConDataCons, tyConArity,
- tyConTheta, maybeTyConSingleCon, isDataTyCon,
+ tyConTheta, isProductTyCon, isDataTyCon,
isEnumerationTyCon, isRecursiveTyCon, TyCon
)
-import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe,
+import TcType ( TcType, ThetaType, mkTyVarTy, mkTyVarTys, mkTyConApp,
+ getClassPredTys_maybe,
isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys, isTypeKind,
tcEqTypes, tcSplitAppTys, mkAppTys, tcSplitDFunTy )
import Var ( TyVar, tyVarKind, idType, varName )
let
extra_mbind_list = map gen_tag_n_con_monobind nm_alist_etc
- extra_mbinds = foldr AndMonoBinds EmptyMonoBinds extra_mbind_list
+ extra_mbinds = andMonoBindList extra_mbind_list
mbinders = collectMonoBinders extra_mbinds
in
mappM gen_bind new_dfuns `thenM` \ rdr_name_inst_infos ->
-- over the method bindings for the instances.
bindLocalsFV (ptext (SLIT("deriving"))) mbinders $ \ _ ->
rnTopMonoBinds extra_mbinds [] `thenM` \ (rn_extra_binds, dus) ->
- mapAndUnzipM rn_inst_info rdr_name_inst_infos `thenM` \ (rn_inst_infos, fvs_s) ->
- returnM ((rn_inst_infos, rn_extra_binds),
- duUses dus `plusFV` plusFVs fvs_s)
+
+ mapAndUnzipM rn_inst_info rdr_name_inst_infos `thenM` \ (pairs, fvs_s) ->
+
+ let
+ (rn_inst_infos, aux_binds_s) = unzip pairs
+ all_binds = rn_extra_binds `ThenBinds` foldr ThenBinds EmptyBinds aux_binds_s
+ in
+ returnM ((rn_inst_infos, all_binds),
+ duUses dus `plusFV` plusFVs fvs_s)
) `thenM` \ ((rn_inst_infos, rn_extra_binds), fvs) ->
returnM (rn_inst_infos, rn_extra_binds, fvs)
where
- rn_inst_info (dfun, binds)
- = extendTyVarEnvFVRn (map varName tyvars) $
+ rn_inst_info (dfun, (meth_binds, aux_binds))
+ = -- Rename the auxiliary bindings
+ bindLocalsFV (ptext (SLIT("deriving"))) mbinders $ \ _ ->
+ rnTopMonoBinds aux_binds [] `thenM` \ (rn_aux_binds, dus) ->
+
-- Bring the right type variables into scope
- rnMethodBinds (className cls) [] binds `thenM` \ (rn_binds, fvs) ->
- return (InstInfo { iDFunId = dfun, iBinds = VanillaInst rn_binds [] }, fvs)
+ extendTyVarEnvFVRn (map varName tyvars) $
+ rnMethodBinds (className cls) [] meth_binds `thenM` \ (rn_meth_binds, fvs) ->
+
+ return ((InstInfo { iDFunId = dfun, iBinds = VanillaInst rn_meth_binds [] },
+ rn_aux_binds),
+ duUses dus `plusFV` fvs)
where
+ mbinders = collectMonoBinders aux_binds
(tyvars, _, cls, _) = tcSplitDFunTy (idType dfun)
\end{code}
------------------------------------------------------------------
mk_eqn_help gla_exts DataType tycon clas tys
- | Just err <- chk_out gla_exts clas tycon tys
+ | Just err <- checkSideConditions gla_exts clas tycon tys
= bale_out (derivingThingErr clas tys tycon tyvars err)
| otherwise
= new_dfun_name clas tycon `thenM` \ dfun_name ->
where
tyvars = tyConTyVars tycon
data_cons = tyConDataCons tycon
- constraints = extra_constraints ++
- [ mkClassPred clas [arg_ty]
- | data_con <- tyConDataCons tycon,
- arg_ty <- dataConOrigArgTys data_con,
- -- Use the same type variables
- -- as the type constructor,
- -- hence no need to instantiate
- not (isUnLiftedType arg_ty) -- No constraints for unlifted types?
- ]
-
- -- "extra_constraints": see note [Data decl contexts] above
+ constraints = extra_constraints ++ ordinary_constraints
+ -- "extra_constraints": see note [Data decl contexts] above
extra_constraints = tyConTheta tycon
+ ordinary_constraints
+ | clas `hasKey` typeableClassKey -- For the Typeable class, the constraints
+ -- don't involve the constructor ags, only
+ -- the tycon tyvars
+ -- e.g. data T a b = ...
+ -- we want
+ -- instance (Typeable a, Typable b)
+ -- => Typeable (T a b) where
+ = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars]
+ | otherwise
+ = [ mkClassPred clas [arg_ty]
+ | data_con <- tyConDataCons tycon,
+ arg_ty <- dataConOrigArgTys data_con,
+ -- Use the same type variables
+ -- as the type constructor,
+ -- hence no need to instantiate
+ not (isUnLiftedType arg_ty) -- No constraints for unlifted types?
+ ]
+
mk_eqn_help gla_exts NewType tycon clas tys
| can_derive_via_isomorphism && (gla_exts || standard_class gla_exts clas)
= -- Go ahead and use the isomorphism
right_arity = length tys + 1 == classArity clas
+ -- Never derive Read,Show,Typeable,Data this way
+ non_iso_classes = [readClassKey, showClassKey, typeableClassKey, dataClassKey]
can_derive_via_isomorphism
- = not (clas `hasKey` readClassKey) -- Never derive Read,Show,Typeable this way
- && not (clas `hasKey` showClassKey)
- && not (clas `hasKey` typeableClassKey)
+ = not (getUnique clas `elem` non_iso_classes)
&& right_arity -- Well kinded;
-- eg not: newtype T ... deriving( ST )
-- because ST needs *2* type params
-- Don't want
-- instance Eq [A] => Eq A !!
+ -- Here's a recursive newtype that's actually OK
+ -- newtype S1 = S1 [T1 ()]
+ -- newtype T1 a = T1 (StateT S1 IO a ) deriving( Monad )
+ -- It's currently rejected. Oh well.
+
-- Check that eta reduction is OK
-- (a) the dropped-off args are identical
-- (b) the remaining type args mention
ptext SLIT("Try -fglasgow-exts for GHC's newtype-deriving extension")])
bale_out err = addErrTc err `thenM_` returnM (Nothing, Nothing)
-
standard_class gla_exts clas = key `elem` derivableClassKeys
- || (gla_exts && (key == typeableClassKey || key == traverseClassKey))
+ || (gla_exts && (key == typeableClassKey || key == dataClassKey))
where
key = classKey clas
- ------------------------------------------------------------------
- chk_out :: Bool -> Class -> TyCon -> [TcType] -> Maybe SDoc
- chk_out gla_exts clas tycon tys
- | notNull tys = Just ty_args_why
- | not (standard_class gla_exts clas) = Just (non_std_why clas)
- | clas `hasKey` enumClassKey && not is_enumeration = Just nullary_why
- | clas `hasKey` boundedClassKey && not is_enumeration_or_single = Just single_nullary_why
- | clas `hasKey` ixClassKey && not is_enumeration_or_single = Just single_nullary_why
- | clas `hasKey` typeableClassKey && not all_type_kind = Just not_type_kind_why
- | null data_cons = Just no_cons_why
- | any isExistentialDataCon data_cons = Just existential_why
- | otherwise = Nothing
- where
- data_cons = tyConDataCons tycon
- is_enumeration = isEnumerationTyCon tycon
- is_single_con = maybeToBool (maybeTyConSingleCon tycon)
- is_enumeration_or_single = is_enumeration || is_single_con
- all_type_kind = all (isTypeKind . tyVarKind) (tyConTyVars tycon)
- single_nullary_why = ptext SLIT("one constructor data type or type with all nullary constructors expected")
- nullary_why = quotes (ppr tycon) <+> ptext SLIT("has non-nullary constructors")
- no_cons_why = quotes (ppr tycon) <+> ptext SLIT("has no data constructors")
- ty_args_why = quotes (ppr pred) <+> ptext SLIT("is not a class")
- existential_why = quotes (ppr tycon) <+> ptext SLIT("has existentially-quantified constructor(s)")
- not_type_kind_why = quotes (ppr tycon) <+> ptext SLIT("is parameterised over arguments of kind other than `*'")
- pred = mkClassPred clas tys
-non_std_why clas = quotes (ppr clas) <+> ptext SLIT("is not a derivable class")
new_dfun_name clas tycon -- Just a simple wrapper
= newDFunName clas [mkTyConApp tycon []] (getSrcLoc tycon)
-- The type passed to newDFunName is only used to generate
-- a suitable string; hence the empty type arg list
+
+
+------------------------------------------------------------------
+-- Check side conditions that dis-allow derivability for particular classes
+-- This is *apart* from the newtype-deriving mechanism
+
+checkSideConditions :: Bool -> Class -> TyCon -> [TcType] -> Maybe SDoc
+checkSideConditions gla_exts clas tycon tys
+ | notNull tys
+ = Just ty_args_why -- e.g. deriving( Foo s )
+ | otherwise
+ = case [cond | (key,cond) <- sideConditions, key == getUnique clas] of
+ [] -> Just (non_std_why clas)
+ [cond] -> cond (gla_exts, tycon)
+ other -> pprPanic "checkSideConditions" (ppr clas)
+ where
+ ty_args_why = quotes (ppr (mkClassPred clas tys)) <+> ptext SLIT("is not a class")
+
+non_std_why clas = quotes (ppr clas) <+> ptext SLIT("is not a derivable class")
+
+sideConditions :: [(Unique, Condition)]
+sideConditions
+ = [ (eqClassKey, cond_std),
+ (ordClassKey, cond_std),
+ (readClassKey, cond_std),
+ (showClassKey, cond_std),
+ (enumClassKey, cond_std `andCond` cond_isEnumeration),
+ (ixClassKey, cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)),
+ (boundedClassKey, cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)),
+ (typeableClassKey, cond_glaExts `andCond` cond_allTypeKind),
+ (dataClassKey, cond_glaExts `andCond` cond_std)
+ ]
+
+type Condition = (Bool, TyCon) -> Maybe SDoc -- Nothing => OK
+
+orCond :: Condition -> Condition -> Condition
+orCond c1 c2 tc
+ = case c1 tc of
+ Nothing -> Nothing -- c1 succeeds
+ Just x -> case c2 tc of -- c1 fails
+ Nothing -> Nothing
+ Just y -> Just (x $$ ptext SLIT(" and") $$ y)
+ -- Both fail
+
+andCond c1 c2 tc = case c1 tc of
+ Nothing -> c2 tc -- c1 succeeds
+ Just x -> Just x -- c1 fails
+
+cond_std :: Condition
+cond_std (gla_exts, tycon)
+ | any isExistentialDataCon data_cons = Just existential_why
+ | null data_cons = Just no_cons_why
+ | otherwise = Nothing
+ where
+ data_cons = tyConDataCons tycon
+ no_cons_why = quotes (ppr tycon) <+> ptext SLIT("has no data constructors")
+ existential_why = quotes (ppr tycon) <+> ptext SLIT("has existentially-quantified constructor(s)")
+
+cond_isEnumeration :: Condition
+cond_isEnumeration (gla_exts, tycon)
+ | isEnumerationTyCon tycon = Nothing
+ | otherwise = Just why
+ where
+ why = quotes (ppr tycon) <+> ptext SLIT("has non-nullary constructors")
+
+cond_isProduct :: Condition
+cond_isProduct (gla_exts, tycon)
+ | isProductTyCon tycon = Nothing
+ | otherwise = Just why
+ where
+ why = quotes (ppr tycon) <+> ptext SLIT("has more than one constructor")
+
+cond_allTypeKind :: Condition
+cond_allTypeKind (gla_exts, tycon)
+ | all (isTypeKind . tyVarKind) (tyConTyVars tycon) = Nothing
+ | otherwise = Just why
+ where
+ why = quotes (ppr tycon) <+> ptext SLIT("is parameterised over arguments of kind other than `*'")
+
+cond_glaExts :: Condition
+cond_glaExts (gla_exts, tycon) | gla_exts = Nothing
+ | otherwise = Just why
+ where
+ why = ptext SLIT("You need -fglasgow-exts to derive an instance for this class")
\end{code}
%************************************************************************
-- Generate the method bindings for the required instance
-- (paired with DFunId, as we need that when renaming
-- the method binds)
-gen_bind :: DFunId -> TcM (DFunId, RdrNameMonoBinds)
+gen_bind :: DFunId -> TcM (DFunId, (RdrNameMonoBinds, RdrNameMonoBinds))
gen_bind dfun
= getFixityEnv `thenM` \ fix_env ->
let
gen_binds_fn = assoc "gen_bind:bad derived class"
gen_list (getUnique clas)
- gen_list = [(eqClassKey, gen_Eq_binds)
- ,(ordClassKey, gen_Ord_binds)
- ,(enumClassKey, gen_Enum_binds)
- ,(boundedClassKey, gen_Bounded_binds)
- ,(ixClassKey, gen_Ix_binds)
- ,(showClassKey, gen_Show_binds fix_env)
- ,(readClassKey, gen_Read_binds fix_env)
- ,(typeableClassKey,gen_Typeable_binds)
+ gen_list = [(eqClassKey, no_aux_binds gen_Eq_binds)
+ ,(ordClassKey, no_aux_binds gen_Ord_binds)
+ ,(enumClassKey, no_aux_binds gen_Enum_binds)
+ ,(boundedClassKey, no_aux_binds gen_Bounded_binds)
+ ,(ixClassKey, no_aux_binds gen_Ix_binds)
+ ,(showClassKey, no_aux_binds (gen_Show_binds fix_env))
+ ,(readClassKey, no_aux_binds (gen_Read_binds fix_env))
+ ,(typeableClassKey,no_aux_binds gen_Typeable_binds)
+ ,(dataClassKey, gen_Data_binds fix_env)
]
+
+ -- Used for generators that don't need to produce
+ -- any auxiliary bindings
+ no_aux_binds f tc = (f tc, EmptyMonoBinds)
in
returnM (dfun, gen_binds_fn tycon)
\end{code}
((we_are_deriving eqClassKey tycon
&& any isNullaryDataCon (tyConDataCons tycon))
|| (we_are_deriving ordClassKey tycon
- && not (maybeToBool (maybeTyConSingleCon tycon)))
+ && not (isProductTyCon tycon))
|| (we_are_deriving enumClassKey tycon)
|| (we_are_deriving ixClassKey tycon))
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