#include "HsVersions.h"
-import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..),
- collectMonoBinders )
+import HsSyn ( HsBinds(..), TyClDecl(..), MonoBinds(..),
+ andMonoBindList )
import RdrHsSyn ( RdrNameMonoBinds )
-import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPred )
+import RnHsSyn ( RenamedHsBinds, RenamedTyClDecl, RenamedHsPred )
import CmdLineOpts ( DynFlag(..) )
+import Generics ( mkTyConGenericBinds )
import TcRnMonad
-import TcEnv ( tcGetInstEnv, tcSetInstEnv, newDFunName, InstInfo(..), pprInstInfo,
+import TcEnv ( newDFunName,
+ InstInfo(..), InstBindings(..),
pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv
)
import TcGenDeriv -- Deriv stuff
-import InstEnv ( InstEnv, simpleDFunClassTyCon, extendInstEnv )
-import TcMonoType ( tcHsPred )
+import InstEnv ( simpleDFunClassTyCon, extendInstEnv )
+import TcHsType ( tcHsPred )
import TcSimplify ( tcSimplifyDeriv )
import RnBinds ( rnMethodBinds, rnTopMonoBinds )
-import RnEnv ( bindLocalsFVRn )
-import TcRnMonad ( thenM, returnM, mapAndUnzipM )
-import HscTypes ( DFunId )
+import RnEnv ( bindLocalNames )
+import TcRnMonad ( thenM, returnM, mapAndUnzipM )
+import HscTypes ( DFunId, FixityEnv, typeEnvTyCons )
import BasicTypes ( NewOrData(..) )
-import Class ( className, classKey, classTyVars, Class )
+import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class )
+import Subst ( mkTyVarSubst, substTheta )
import ErrUtils ( dumpIfSet_dyn )
import MkId ( mkDictFunId )
-import DataCon ( dataConRepArgTys, isNullaryDataCon, isExistentialDataCon )
-import Maybes ( maybeToBool, catMaybes )
-import Name ( Name, getSrcLoc, nameUnique )
-import NameSet
-import RdrName ( RdrName )
-
-import TyCon ( tyConTyVars, tyConDataCons, tyConArity, newTyConRep,
- tyConTheta, maybeTyConSingleCon, isDataTyCon,
+import DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon )
+import Maybes ( catMaybes )
+import Name ( Name, getSrcLoc )
+import NameSet ( NameSet, emptyNameSet, duDefs )
+import Unique ( Unique, getUnique )
+
+import TyCon ( tyConTyVars, tyConDataCons, tyConArity, tyConHasGenerics,
+ tyConTheta, isProductTyCon, isDataTyCon,
isEnumerationTyCon, isRecursiveTyCon, TyCon
)
-import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe,
- isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys,
- tcSplitTyConApp_maybe, tcEqTypes )
-import Var ( TyVar, tyVarKind )
+import TcType ( TcType, ThetaType, mkTyVarTy, mkTyVarTys, mkTyConApp,
+ getClassPredTys_maybe, tcTyConAppTyCon,
+ isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys, isTypeKind,
+ tcEqTypes, tcSplitAppTys, mkAppTys, tcSplitDFunTy )
+import Var ( TyVar, tyVarKind, idType, varName )
import VarSet ( mkVarSet, subVarSet )
import PrelNames
import Util ( zipWithEqual, sortLt, notNull )
import ListSetOps ( removeDups, assoc )
import Outputable
-import Maybe ( isJust )
\end{code}
%************************************************************************
\end{code}
-A note about contexts on data decls
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+[Data decl contexts] A note about contexts on data decls
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
data (RealFloat a) => Complex a = !a :+ !a deriving( Read )
\begin{code}
tcDeriving :: [RenamedTyClDecl] -- All type constructors
- -> TcM ([InstInfo], -- The generated "instance decls".
- RenamedHsBinds, -- Extra generated bindings
- FreeVars) -- These are free in the generated bindings
+ -> TcM ([InstInfo], -- The generated "instance decls"
+ RenamedHsBinds, -- Extra generated top-level bindings
+ NameSet) -- Binders to keep alive
tcDeriving tycl_decls
- = recoverM (returnM ([], EmptyBinds, emptyFVs)) $
- getDOpts `thenM` \ dflags ->
- tcGetInstEnv `thenM` \ inst_env ->
-
- -- Fish the "deriving"-related information out of the TcEnv
- -- and make the necessary "equations".
- makeDerivEqns tycl_decls `thenM` \ (ordinary_eqns, newtype_inst_info) ->
- let
- -- Add the newtype-derived instances to the inst env
- -- before tacking the "ordinary" ones
- inst_env1 = extend_inst_env dflags inst_env
- (map iDFunId newtype_inst_info)
- in
- deriveOrdinaryStuff inst_env1 ordinary_eqns `thenM` \ (ordinary_inst_info, binds, fvs) ->
- let
- inst_info = newtype_inst_info ++ ordinary_inst_info
- in
-
- ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances"
- (ddump_deriving inst_info binds)) `thenM_`
-
- returnM (inst_info, binds, fvs)
-
+ = recoverM (returnM ([], EmptyBinds, emptyNameSet)) $
+ do { -- Fish the "deriving"-related information out of the TcEnv
+ -- and make the necessary "equations".
+ ; (ordinary_eqns, newtype_inst_info) <- makeDerivEqns tycl_decls
+
+ ; (ordinary_inst_info, deriv_binds)
+ <- extendLocalInstEnv (map iDFunId newtype_inst_info) $
+ deriveOrdinaryStuff ordinary_eqns
+ -- Add the newtype-derived instances to the inst env
+ -- before tacking the "ordinary" ones
+
+ -- Generate the generic to/from functions from each type declaration
+ ; gen_binds <- mkGenericBinds tycl_decls
+ ; let inst_info = newtype_inst_info ++ ordinary_inst_info
+
+ -- Rename these extra bindings, discarding warnings about unused bindings etc
+ -- Set -fglasgow exts so that we can have type signatures in patterns,
+ -- which is used in the generic binds
+ ; (rn_binds, gen_bndrs)
+ <- discardWarnings $ setOptM Opt_GlasgowExts $ do
+ { (rn_deriv, _dus1) <- rnTopMonoBinds deriv_binds []
+ ; (rn_gen, dus_gen) <- rnTopMonoBinds gen_binds []
+ ; return (rn_deriv `ThenBinds` rn_gen, duDefs dus_gen) }
+
+
+ ; dflags <- getDOpts
+ ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances"
+ (ddump_deriving inst_info rn_binds))
+
+ ; returnM (inst_info, rn_binds, gen_bndrs)
+ }
where
ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc
ddump_deriving inst_infos extra_binds
- = vcat (map ppr_info inst_infos) $$ ppr extra_binds
-
- ppr_info inst_info = pprInstInfo inst_info $$
- nest 4 (pprInstInfoDetails inst_info)
- -- pprInstInfo doesn't print much: only the type
+ = vcat (map pprInstInfoDetails inst_infos) $$ ppr extra_binds
-----------------------------------------
-deriveOrdinaryStuff inst_env_in [] -- Short cut
- = returnM ([], EmptyBinds, emptyFVs)
-
-deriveOrdinaryStuff inst_env_in eqns
- = -- Take the equation list and solve it, to deliver a list of
- -- solutions, a.k.a. the contexts for the instance decls
- -- required for the corresponding equations.
- solveDerivEqns inst_env_in eqns `thenM` \ new_dfuns ->
-
- -- Now augment the InstInfos, adding in the rather boring
- -- actual-code-to-do-the-methods binds. We may also need to
- -- generate extra not-one-inst-decl-specific binds, notably
- -- "con2tag" and/or "tag2con" functions. We do these
- -- separately.
- gen_taggery_Names new_dfuns `thenM` \ nm_alist_etc ->
+deriveOrdinaryStuff [] -- Short cut
+ = returnM ([], EmptyMonoBinds)
- let
- extra_mbind_list = map gen_tag_n_con_monobind nm_alist_etc
- extra_mbinds = foldr AndMonoBinds EmptyMonoBinds extra_mbind_list
- mbinders = collectMonoBinders extra_mbinds
- in
- mappM gen_bind new_dfuns `thenM` \ method_binds_s ->
-
- traceTc (text "tcDeriv" <+> ppr method_binds_s) `thenM_`
- getModule `thenM` \ this_mod ->
- initRn (InterfaceMode this_mod) (
- -- Rename to get RenamedBinds.
- -- The only tricky bit is that the extra_binds must scope
- -- over the method bindings for the instances.
- bindLocalsFVRn (ptext (SLIT("deriving"))) mbinders $ \ _ ->
- rnTopMonoBinds extra_mbinds [] `thenM` \ (rn_extra_binds, fvs) ->
- mapAndUnzipM rn_meths method_binds_s `thenM` \ (rn_method_binds_s, fvs_s) ->
- returnM ((rn_method_binds_s, rn_extra_binds),
- fvs `plusFV` plusFVs fvs_s)
- ) `thenM` \ ((rn_method_binds_s, rn_extra_binds), fvs) ->
- let
- new_inst_infos = zipWith gen_inst_info new_dfuns rn_method_binds_s
- in
- returnM (new_inst_infos, rn_extra_binds, fvs)
+deriveOrdinaryStuff eqns
+ = do { -- Take the equation list and solve it, to deliver a list of
+ -- solutions, a.k.a. the contexts for the instance decls
+ -- required for the corresponding equations.
+ ; new_dfuns <- solveDerivEqns eqns
- where
- -- Make a Real dfun instead of the dummy one we have so far
- gen_inst_info :: DFunId -> RenamedMonoBinds -> InstInfo
- gen_inst_info dfun binds
- = InstInfo { iDFunId = dfun, iBinds = binds, iPrags = [] }
+ -- Generate the InstInfo for each dfun,
+ -- plus any auxiliary bindings it needs
+ ; (inst_infos, aux_binds_s) <- mapAndUnzipM genInst new_dfuns
+
+ -- Generate any extra not-one-inst-decl-specific binds,
+ -- notably "con2tag" and/or "tag2con" functions.
+ ; extra_binds <- genTaggeryBinds new_dfuns
- rn_meths (cls, meths) = rnMethodBinds cls [] meths
+ -- Done
+ ; returnM (inst_infos, andMonoBindList (extra_binds : aux_binds_s)) }
+
+-----------------------------------------
+mkGenericBinds tycl_decls
+ = do { tcs <- mapM tcLookupTyCon [tc_name | TyData { tcdName = tc_name } <- tycl_decls]
+ -- We are only interested in the data type declarations
+ ; return (andMonoBindList [mkTyConGenericBinds tc | tc <- tcs, tyConHasGenerics tc]) }
+ -- And then only in the ones whose 'has-generics' flag is on
\end{code}
tcHsPred pred `thenM` \ pred' ->
case getClassPredTys_maybe pred' of
Nothing -> bale_out (malformedPredErr tycon pred)
- Just (clas, tys) -> mk_eqn_help new_or_data tycon clas tys
+ Just (clas, tys) -> doptM Opt_GlasgowExts `thenM` \ gla_exts ->
+ mk_eqn_help gla_exts new_or_data tycon clas tys
------------------------------------------------------------------
- mk_eqn_help DataType tycon clas tys
- | Just err <- chk_out clas tycon tys
+ mk_eqn_help gla_exts DataType tycon clas 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 ->
returnM (Just (dfun_name, clas, tycon, tyvars, constraints), Nothing)
where
- tyvars = tyConTyVars tycon
- data_cons = tyConDataCons tycon
- constraints = extra_constraints ++
- [ mkClassPred clas [arg_ty]
- | data_con <- tyConDataCons tycon,
- arg_ty <- dataConRepArgTys 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 notes above about contexts on data decls
+ tyvars = tyConTyVars tycon
+ constraints = extra_constraints ++ ordinary_constraints
+ -- "extra_constraints": see note [Data decl contexts] above
extra_constraints = tyConTheta tycon
- -- | offensive_class = tyConTheta tycon
- -- | otherwise = []
- -- offensive_class = classKey clas `elem` PrelInfo.needsDataDeclCtxtClassKeys
-
-
- mk_eqn_help NewType tycon clas tys
- = doptM Opt_GlasgowExts `thenM` \ gla_exts ->
- if can_derive_via_isomorphism && (gla_exts || standard_instance) then
- -- Go ahead and use the isomorphism
+ 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
+ traceTc (text "newtype deriving:" <+> ppr tycon <+> ppr rep_tys) `thenM_`
new_dfun_name clas tycon `thenM` \ dfun_name ->
- returnM (Nothing, Just (NewTypeDerived (mk_dfun dfun_name)))
- else
- if standard_instance then
- mk_eqn_help DataType tycon clas [] -- Go via bale-out route
- else
- bale_out cant_derive_err
+ returnM (Nothing, Just (InstInfo { iDFunId = mk_dfun dfun_name,
+ iBinds = NewTypeDerived rep_tys }))
+ | standard_class gla_exts clas
+ = mk_eqn_help gla_exts DataType tycon clas tys -- Go via bale-out route
+
+ | otherwise -- Non-standard instance
+ = bale_out (if gla_exts then
+ cant_derive_err -- Too hard
+ else
+ non_std_err) -- Just complain about being a non-std instance
where
-- Here is the plan for newtype derivings. We see
- -- newtype T a1...an = T (t ak...an) deriving (C1...Cm)
- -- where aj...an do not occur free in t, and the Ci are *partial applications* of
- -- classes with the last parameter missing
+ -- newtype T a1...an = T (t ak...an) deriving (.., C s1 .. sm, ...)
+ -- where aj...an do not occur free in t, and the (C s1 ... sm) is a
+ -- *partial applications* of class C with the last parameter missing
--
-- We generate the instances
- -- instance Ci (t ak...aj) => Ci (T a1...aj)
+ -- instance C s1 .. sm (t ak...aj) => C s1 .. sm (T a1...aj)
-- where T a1...aj is the partial application of the LHS of the correct kind
--
-- Running example: newtype T s a = MkT (ST s a) deriving( Monad )
+ -- instance Monad (ST s) => Monad (T s) where
+ -- fail = coerce ... (fail @ ST s)
- kind = tyVarKind (last (classTyVars clas))
+ clas_tyvars = classTyVars clas
+ kind = tyVarKind (last clas_tyvars)
-- Kind of the thing we want to instance
-- e.g. argument kind of Monad, *->*
-- Want to drop 1 arg from (T s a) and (ST s a)
-- to get instance Monad (ST s) => Monad (T s)
- (tyvars, rep_ty) = newTyConRep tycon
- maybe_rep_app = tcSplitTyConApp_maybe rep_ty
- Just (rep_tc, rep_ty_args) = maybe_rep_app
+ -- Note [newtype representation]
+ -- We must not use newTyConRep to get the representation
+ -- type, because that looks through all intermediate newtypes
+ -- To get the RHS of *this* newtype, just look at the data
+ -- constructor. For example
+ -- newtype B = MkB Int
+ -- newtype A = MkA B deriving( Num )
+ -- We want the Num instance of B, *not* the Num instance of Int,
+ -- when making the Num instance of A!
+ tyvars = tyConTyVars tycon
+ rep_ty = head (dataConOrigArgTys (head (tyConDataCons tycon)))
+ (rep_fn, rep_ty_args) = tcSplitAppTys rep_ty
n_tyvars_to_keep = tyConArity tycon - n_args_to_drop
tyvars_to_drop = drop n_tyvars_to_keep tyvars
tyvars_to_keep = take n_tyvars_to_keep tyvars
- n_args_to_keep = tyConArity rep_tc - n_args_to_drop
+ n_args_to_keep = length rep_ty_args - n_args_to_drop
args_to_drop = drop n_args_to_keep rep_ty_args
args_to_keep = take n_args_to_keep rep_ty_args
- ctxt_pred = mkClassPred clas (tys ++ [mkTyConApp rep_tc args_to_keep])
-
- mk_dfun dfun_name = mkDictFunId dfun_name clas tyvars
- (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars_to_keep)] )
- [ctxt_pred]
-
- -- We can only do this newtype deriving thing if:
- standard_instance = null tys && classKey clas `elem` derivableClassKeys
-
+ rep_tys = tys ++ [mkAppTys rep_fn args_to_keep]
+ rep_pred = mkClassPred clas rep_tys
+ -- rep_pred is the representation dictionary, from where
+ -- we are gong to get all the methods for the newtype dictionary
+
+ inst_tys = (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars_to_keep)])
+ -- The 'tys' here come from the partial application
+ -- in the deriving clause. The last arg is the new
+ -- instance type.
+
+ -- We must pass the superclasses; the newtype might be an instance
+ -- of them in a different way than the representation type
+ -- E.g. newtype Foo a = Foo a deriving( Show, Num, Eq )
+ -- Then the Show instance is not done via isomprphism; it shows
+ -- Foo 3 as "Foo 3"
+ -- The Num instance is derived via isomorphism, but the Show superclass
+ -- dictionary must the Show instance for Foo, *not* the Show dictionary
+ -- gotten from the Num dictionary. So we must build a whole new dictionary
+ -- not just use the Num one. The instance we want is something like:
+ -- instance (Num a, Show (Foo a), Eq (Foo a)) => Num (Foo a) where
+ -- (+) = ((+)@a)
+ -- ...etc...
+ -- There's no 'corece' needed because after the type checker newtypes
+ -- are transparent.
+
+ sc_theta = substTheta (mkTyVarSubst clas_tyvars inst_tys)
+ (classSCTheta clas)
+
+ -- If there are no tyvars, there's no need
+ -- to abstract over the dictionaries we need
+ dict_args | null tyvars = []
+ | otherwise = rep_pred : sc_theta
+
+ -- Finally! Here's where we build the dictionary Id
+ mk_dfun dfun_name = mkDictFunId dfun_name tyvars dict_args clas inst_tys
+
+ -------------------------------------------------------------------
+ -- Figuring out whether we can only do this newtype-deriving thing
+
+ 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 this way
- && not (clas `hasKey` showClassKey)
- && n_tyvars_to_keep >= 0 -- Well kinded;
+ = not (getUnique clas `elem` non_iso_classes)
+ && right_arity -- Well kinded;
+ -- eg not: newtype T ... deriving( ST )
+ -- because ST needs *2* type params
+ && n_tyvars_to_keep >= 0 -- Type constructor has right kind:
-- eg not: newtype T = T Int deriving( Monad )
- && isJust maybe_rep_app -- The rep type is a type constructor app
- && n_args_to_keep >= 0 -- Well kinded:
+ && n_args_to_keep >= 0 -- Rep type has right kind:
-- eg not: newtype T a = T Int deriving( Monad )
&& eta_ok -- Eta reduction works
&& not (isRecursiveTyCon tycon) -- Does not work for recursive tycons:
-- 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
&& (tyVarsOfTypes args_to_keep `subVarSet` mkVarSet tyvars_to_keep)
cant_derive_err = derivingThingErr clas tys tycon tyvars_to_keep
- (ptext SLIT("too hard for cunning newtype deriving"))
+ (vcat [ptext SLIT("even with cunning newtype deriving:"),
+ if isRecursiveTyCon tycon then
+ ptext SLIT("the newtype is recursive")
+ else empty,
+ if not right_arity then
+ quotes (ppr (mkClassPred clas tys)) <+> ptext SLIT("does not have arity 1")
+ else empty,
+ if not (n_tyvars_to_keep >= 0) then
+ ptext SLIT("the type constructor has wrong kind")
+ else if not (n_args_to_keep >= 0) then
+ ptext SLIT("the representation type has wrong kind")
+ else if not eta_ok then
+ ptext SLIT("the eta-reduction property does not hold")
+ else empty
+ ])
+
+ non_std_err = derivingThingErr clas tys tycon tyvars_to_keep
+ (vcat [non_std_why clas,
+ ptext SLIT("Try -fglasgow-exts for GHC's newtype-deriving extension")])
bale_out err = addErrTc err `thenM_` returnM (Nothing, Nothing)
-
- ------------------------------------------------------------------
- chk_out :: Class -> TyCon -> [TcType] -> Maybe SDoc
- chk_out clas tycon tys
- | notNull tys = Just non_std_why
- | not (getUnique clas `elem` derivableClassKeys) = Just non_std_why
- | 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
- | null data_cons = Just no_cons_why
- | any isExistentialDataCon data_cons = Just existential_why
- | otherwise = Nothing
+ standard_class gla_exts clas = key `elem` derivableClassKeys
+ || (gla_exts && (key == typeableClassKey || key == dataClassKey))
where
- data_cons = tyConDataCons tycon
- is_enumeration = isEnumerationTyCon tycon
- is_single_con = maybeToBool (maybeTyConSingleCon tycon)
- is_enumeration_or_single = is_enumeration || is_single_con
+ key = classKey clas
+
+
- single_nullary_why = ptext SLIT("one constructor data type or type with all nullary constructors expected")
- nullary_why = ptext SLIT("data type with all nullary constructors expected")
- no_cons_why = ptext SLIT("type has no data constructors")
- non_std_why = ptext SLIT("not a derivable class")
- existential_why = ptext SLIT("it has existentially-quantified constructor(s)")
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") $$ y)
+ -- Both fail
+
+andCond c1 c2 tc = case c1 tc of
+ Nothing -> c2 tc -- c1 succeeds
+ Just x -> Just x -- c1 fails
+
+cond_std :: Condition
+cond_std (gla_exts, tycon)
+ | any isExistentialDataCon data_cons = Just existential_why
+ | null data_cons = Just no_cons_why
+ | otherwise = Nothing
+ where
+ data_cons = tyConDataCons tycon
+ no_cons_why = quotes (ppr tycon) <+> ptext SLIT("has no data constructors")
+ existential_why = quotes (ppr tycon) <+> ptext SLIT("has existentially-quantified constructor(s)")
+
+cond_isEnumeration :: Condition
+cond_isEnumeration (gla_exts, tycon)
+ | isEnumerationTyCon tycon = Nothing
+ | otherwise = Just why
+ where
+ why = quotes (ppr tycon) <+> ptext SLIT("has non-nullary constructors")
+
+cond_isProduct :: Condition
+cond_isProduct (gla_exts, tycon)
+ | isProductTyCon tycon = Nothing
+ | otherwise = Just why
+ where
+ why = quotes (ppr tycon) <+> ptext SLIT("has more than one constructor")
+
+cond_allTypeKind :: Condition
+cond_allTypeKind (gla_exts, tycon)
+ | all (isTypeKind . tyVarKind) (tyConTyVars tycon) = Nothing
+ | otherwise = Just why
+ where
+ why = quotes (ppr tycon) <+> ptext SLIT("is parameterised over arguments of kind other than `*'")
+
+cond_glaExts :: Condition
+cond_glaExts (gla_exts, tycon) | gla_exts = Nothing
+ | otherwise = Just why
+ where
+ why = ptext SLIT("You need -fglasgow-exts to derive an instance for this class")
\end{code}
%************************************************************************
\end{itemize}
\begin{code}
-solveDerivEqns :: InstEnv
- -> [DerivEqn]
+solveDerivEqns :: [DerivEqn]
-> TcM [DFunId] -- Solns in same order as eqns.
-- This bunch is Absolutely minimal...
-solveDerivEqns inst_env_in orig_eqns
+solveDerivEqns orig_eqns
= iterateDeriv 1 initial_solutions
where
-- The initial solutions for the equations claim that each
= pprPanic "solveDerivEqns: probable loop"
(vcat (map pprDerivEqn orig_eqns) $$ ppr current_solns)
| otherwise
- = getDOpts `thenM` \ dflags ->
- let
- dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns
- inst_env = extend_inst_env dflags inst_env_in dfuns
+ = let
+ dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns
in
checkNoErrs (
-- Extend the inst info from the explicit instance decls
-- with the current set of solutions, and simplify each RHS
- tcSetInstEnv inst_env $
+ extendLocalInstEnv dfuns $
mappM gen_soln orig_eqns
) `thenM` \ new_solns ->
if (current_solns == new_solns) then
addErrCtxt (derivCtxt (Just clas) tc) $
tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta ->
returnM (sortLt (<) theta) -- Canonicalise before returning the soluction
-\end{code}
-
-\begin{code}
-extend_inst_env dflags inst_env new_dfuns
- = new_inst_env
- where
- (new_inst_env, _errs) = extendInstEnv dflags inst_env new_dfuns
- -- Ignore the errors about duplicate instances.
- -- We don't want repeated error messages
- -- They'll appear later, when we do the top-level extendInstEnvs
mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta
- = mkDictFunId dfun_name clas tyvars
- [mkTyConApp tycon (mkTyVarTys tyvars)]
- theta
+ = mkDictFunId dfun_name tyvars theta
+ clas [mkTyConApp tycon (mkTyVarTys tyvars)]
+
+extendLocalInstEnv :: [DFunId] -> TcM a -> TcM a
+-- Add new locall-defined instances; don't bother to check
+-- for functional dependency errors -- that'll happen in TcInstDcls
+extendLocalInstEnv dfuns thing_inside
+ = do { env <- getGblEnv
+ ; let inst_env' = foldl extendInstEnv (tcg_inst_env env) dfuns
+ env' = env { tcg_inst_env = inst_env' }
+ ; setGblEnv env' thing_inside }
\end{code}
%************************************************************************
\end{itemize}
\begin{code}
--- Generate the method bindings for the required instance
--- (paired with class name, as we need that when renaming
--- the method binds)
-gen_bind :: DFunId -> TcM (Name, RdrNameMonoBinds)
-gen_bind dfun
+-- Generate the InstInfo for the required instance,
+-- plus any auxiliary bindings required
+genInst :: DFunId -> TcM (InstInfo, RdrNameMonoBinds)
+genInst dfun
= getFixityEnv `thenM` \ fix_env ->
- returnM (cls_nm, gen_binds_fn fix_env cls_nm tycon)
- where
- cls_nm = className clas
- (clas, tycon) = simpleDFunClassTyCon dfun
-
-gen_binds_fn fix_env cls_nm
- = assoc "gen_bind:bad derived class"
- gen_list (nameUnique cls_nm)
- where
- 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)
- ]
+ let
+ (tyvars,_,clas,[ty]) = tcSplitDFunTy (idType dfun)
+ clas_nm = className clas
+ tycon = tcTyConAppTyCon ty
+ (meth_binds, aux_binds) = assoc "gen_bind:bad derived class"
+ gen_list (getUnique clas) fix_env tycon
+ in
+ -- Bring the right type variables into
+ -- scope, and rename the method binds
+ bindLocalNames (map varName tyvars) $
+ rnMethodBinds clas_nm [] meth_binds `thenM` \ (rn_meth_binds, _fvs) ->
+
+ -- Build the InstInfo
+ returnM (InstInfo { iDFunId = dfun, iBinds = VanillaInst rn_meth_binds [] },
+ aux_binds)
+
+gen_list :: [(Unique, FixityEnv -> TyCon -> (RdrNameMonoBinds, RdrNameMonoBinds))]
+gen_list = [(eqClassKey, no_aux_binds (ignore_fix_env gen_Eq_binds))
+ ,(ordClassKey, no_aux_binds (ignore_fix_env gen_Ord_binds))
+ ,(enumClassKey, no_aux_binds (ignore_fix_env gen_Enum_binds))
+ ,(boundedClassKey, no_aux_binds (ignore_fix_env gen_Bounded_binds))
+ ,(ixClassKey, no_aux_binds (ignore_fix_env gen_Ix_binds))
+ ,(typeableClassKey,no_aux_binds (ignore_fix_env gen_Typeable_binds))
+ ,(showClassKey, no_aux_binds gen_Show_binds)
+ ,(readClassKey, no_aux_binds gen_Read_binds)
+ ,(dataClassKey, gen_Data_binds)
+ ]
+
+ -- no_aux_binds is used for generators that don't
+ -- need to produce any auxiliary bindings
+no_aux_binds f fix_env tc = (f fix_env tc, EmptyMonoBinds)
+ignore_fix_env f fix_env tc = f tc
\end{code}
If we have a @tag2con@ function, we also generate a @maxtag@ constant.
\begin{code}
-gen_taggery_Names :: [DFunId]
- -> TcM [(RdrName, -- for an assoc list
- TyCon, -- related tycon
- TagThingWanted)]
-
-gen_taggery_Names dfuns
- = foldlM do_con2tag [] tycons_of_interest `thenM` \ names_so_far ->
- foldlM do_tag2con names_so_far tycons_of_interest
+genTaggeryBinds :: [DFunId] -> TcM RdrNameMonoBinds
+genTaggeryBinds dfuns
+ = do { names_so_far <- foldlM do_con2tag [] tycons_of_interest
+ ; nm_alist_etc <- foldlM do_tag2con names_so_far tycons_of_interest
+ ; return (andMonoBindList (map gen_tag_n_con_monobind nm_alist_etc)) }
where
all_CTs = map simpleDFunClassTyCon dfuns
all_tycons = map snd all_CTs
((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))