#include "HsVersions.h"
-import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..),
- collectLocatedMonoBinders )
+import HsSyn ( HsBinds(..), TyClDecl(..), MonoBinds(..),
+ andMonoBindList, collectMonoBinders )
import RdrHsSyn ( RdrNameMonoBinds )
-import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPred )
-import CmdLineOpts ( DynFlag(..), DynFlags )
+import RnHsSyn ( RenamedHsBinds, RenamedTyClDecl, RenamedHsPred )
+import CmdLineOpts ( DynFlag(..) )
-import TcMonad
-import TcEnv ( tcSetInstEnv, newDFunName, InstInfo(..), pprInstInfo,
- tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv
+import TcRnMonad
+import TcEnv ( tcExtendTempInstEnv, newDFunName,
+ InstInfo(..), pprInstInfo, InstBindings(..),
+ pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv
)
import TcGenDeriv -- Deriv stuff
-import InstEnv ( InstEnv, simpleDFunClassTyCon, extendInstEnv )
+import InstEnv ( simpleDFunClassTyCon )
import TcMonoType ( tcHsPred )
import TcSimplify ( tcSimplifyDeriv )
import RnBinds ( rnMethodBinds, rnTopMonoBinds )
-import RnEnv ( bindLocatedLocalsRn )
-import RnMonad ( renameDerivedCode, thenRn, mapRn, returnRn )
-import HscTypes ( DFunId, PersistentRenamerState )
-
-import BasicTypes ( Fixity, NewOrData(..) )
-import Class ( className, classKey, classTyVars, Class )
-import ErrUtils ( dumpIfSet_dyn, Message )
+import RnEnv ( bindLocalsFV, extendTyVarEnvFVRn )
+import TcRnMonad ( thenM, returnM, mapAndUnzipM )
+import HscTypes ( DFunId )
+
+import BasicTypes ( NewOrData(..) )
+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 PrelInfo ( needsDataDeclCtxtClassKeys )
+import DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon )
import Maybes ( maybeToBool, catMaybes )
-import Module ( Module )
-import Name ( Name, getSrcLoc, nameUnique )
+import Name ( Name, getSrcLoc )
+import Unique ( Unique, getUnique )
+import NameSet
import RdrName ( RdrName )
-import TyCon ( tyConTyVars, tyConDataCons, tyConArity, newTyConRep,
- tyConTheta, maybeTyConSingleCon, isDataTyCon,
- isEnumerationTyCon, TyCon
+import TyCon ( tyConTyVars, tyConDataCons, tyConArity,
+ tyConTheta, isProductTyCon, isDataTyCon,
+ isEnumerationTyCon, isRecursiveTyCon, TyCon
)
-import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe,
- isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys,
- tcSplitTyConApp_maybe, tcEqTypes, tyVarsOfTheta )
-import Var ( TyVar, tyVarKind )
+import TcType ( TcType, ThetaType, mkTyVarTy, mkTyVarTys, mkTyConApp,
+ getClassPredTys_maybe,
+ 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, eqListBy )
+import Util ( zipWithEqual, sortLt, notNull )
import ListSetOps ( removeDups, assoc )
import Outputable
-import Maybe ( isJust )
-import List ( nub )
-import FastString ( FastString )
\end{code}
%************************************************************************
-- The Name is the name for the DFun we'll build
-- The tyvars bind all the variables in the RHS
+pprDerivEqn (n,c,tc,tvs,rhs)
+ = parens (hsep [ppr n, ppr c, ppr tc, ppr tvs] <+> equals <+> ppr rhs)
+
type DerivRhs = ThetaType
type DerivSoln = DerivRhs
\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 )
Read, Enum?
+FURTHER NOTE ADDED March 2002. In fact, Haskell98 now requires that
+pattern matching against a constructor from a data type with a context
+gives rise to the constraints for that context -- or at least the thinned
+version. So now all classes are "offending".
+
+
%************************************************************************
%* *
%************************************************************************
\begin{code}
-tcDeriving :: PersistentRenamerState
- -> Module -- name of module under scrutiny
- -> InstEnv -- What we already know about instances
- -> (Name -> Maybe Fixity) -- used in deriving Show and Read
- -> [RenamedTyClDecl] -- All type constructors
+tcDeriving :: [RenamedTyClDecl] -- All type constructors
-> TcM ([InstInfo], -- The generated "instance decls".
- RenamedHsBinds) -- Extra generated bindings
+ RenamedHsBinds, -- Extra generated bindings
+ FreeVars) -- These are free in the generated bindings
-tcDeriving prs mod inst_env get_fixity tycl_decls
- = recoverTc (returnTc ([], EmptyBinds)) $
- getDOptsTc `thenNF_Tc` \ dflags ->
+tcDeriving tycl_decls
+ = recoverM (returnM ([], EmptyBinds, emptyFVs)) $
+ getDOpts `thenM` \ dflags ->
-- Fish the "deriving"-related information out of the TcEnv
-- and make the necessary "equations".
- makeDerivEqns tycl_decls `thenTc` \ (ordinary_eqns, newtype_inst_info) ->
- let
+ makeDerivEqns tycl_decls `thenM` \ (ordinary_eqns, newtype_inst_info) ->
+ tcExtendTempInstEnv (map iDFunId newtype_inst_info) $
-- 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 mod prs inst_env1 get_fixity
- ordinary_eqns `thenTc` \ (ordinary_inst_info, binds) ->
+
+ deriveOrdinaryStuff ordinary_eqns `thenM` \ (ordinary_inst_info, binds, fvs) ->
let
inst_info = newtype_inst_info ++ ordinary_inst_info
in
- ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances"
- (ddump_deriving inst_info binds)) `thenTc_`
+ ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances"
+ (ddump_deriving inst_info binds)) `thenM_`
- returnTc (inst_info, binds)
+ returnM (inst_info, binds, fvs)
where
ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc
ddump_deriving inst_infos extra_binds
- = vcat (map pprInstInfo inst_infos) $$ ppr extra_binds
+ = vcat (map ppr_info inst_infos) $$ ppr extra_binds
+ ppr_info inst_info = pprInstInfo inst_info $$
+ nest 4 (pprInstInfoDetails inst_info)
+ -- pprInstInfo doesn't print much: only the type
-----------------------------------------
-deriveOrdinaryStuff mod prs inst_env_in get_fixity [] -- Short cut
- = returnTc ([], EmptyBinds)
+deriveOrdinaryStuff [] -- Short cut
+ = returnM ([], EmptyBinds, emptyFVs)
-deriveOrdinaryStuff mod prs inst_env_in get_fixity eqns
+deriveOrdinaryStuff 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 `thenTc` \ new_dfuns ->
+ solveDerivEqns 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 `thenTc` \ nm_alist_etc ->
+ gen_taggery_Names new_dfuns `thenM` \ nm_alist_etc ->
- tcGetEnv `thenNF_Tc` \ env ->
- getDOptsTc `thenNF_Tc` \ dflags ->
let
extra_mbind_list = map gen_tag_n_con_monobind nm_alist_etc
- extra_mbinds = foldr AndMonoBinds EmptyMonoBinds extra_mbind_list
- method_binds_s = map (gen_bind get_fixity) new_dfuns
- mbinders = collectLocatedMonoBinders extra_mbinds
+ extra_mbinds = andMonoBindList extra_mbind_list
+ mbinders = collectMonoBinders extra_mbinds
+ in
+ mappM gen_bind new_dfuns `thenM` \ rdr_name_inst_infos ->
+ traceTc (text "tcDeriv" <+> vcat (map ppr rdr_name_inst_infos)) `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.
- (rn_method_binds_s, rn_extra_binds)
- = renameDerivedCode dflags mod prs (
- bindLocatedLocalsRn (ptext (SLIT("deriving"))) mbinders $ \ _ ->
- rnTopMonoBinds extra_mbinds [] `thenRn` \ (rn_extra_binds, _) ->
- mapRn rn_meths method_binds_s `thenRn` \ rn_method_binds_s ->
- returnRn (rn_method_binds_s, rn_extra_binds)
- )
- new_inst_infos = zipWith gen_inst_info new_dfuns rn_method_binds_s
- in
- returnTc (new_inst_infos, rn_extra_binds)
+ -- The only tricky bit is that the extra_binds must scope
+ -- 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` \ (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
- -- 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 = [] }
-
- rn_meths (cls, meths) = rnMethodBinds cls [] meths `thenRn` \ (meths', _) ->
- returnRn meths' -- Ignore the free vars returned
+ 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
+ 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}
[InstInfo]) -- Special newtype derivings
makeDerivEqns tycl_decls
- = mapAndUnzipTc mk_eqn derive_these `thenTc` \ (maybe_ordinaries, maybe_newtypes) ->
- returnTc (catMaybes maybe_ordinaries, catMaybes maybe_newtypes)
+ = mapAndUnzipM mk_eqn derive_these `thenM` \ (maybe_ordinaries, maybe_newtypes) ->
+ returnM (catMaybes maybe_ordinaries, catMaybes maybe_newtypes)
where
------------------------------------------------------------------
derive_these :: [(NewOrData, Name, RenamedHsPred)]
pred <- preds ]
------------------------------------------------------------------
- mk_eqn :: (NewOrData, Name, RenamedHsPred) -> NF_TcM (Maybe DerivEqn, Maybe InstInfo)
+ mk_eqn :: (NewOrData, Name, RenamedHsPred) -> TcM (Maybe DerivEqn, Maybe InstInfo)
-- We swizzle the tyvars and datacons out of the tycon
-- to make the rest of the equation
mk_eqn (new_or_data, tycon_name, pred)
- = tcLookupTyCon tycon_name `thenNF_Tc` \ tycon ->
- tcAddSrcLoc (getSrcLoc tycon) $
- tcAddErrCtxt (derivCtxt Nothing tycon) $
+ = tcLookupTyCon tycon_name `thenM` \ tycon ->
+ addSrcLoc (getSrcLoc tycon) $
+ addErrCtxt (derivCtxt Nothing tycon) $
tcExtendTyVarEnv (tyConTyVars tycon) $ -- Deriving preds may (now) mention
-- the type variables for the type constructor
- tcHsPred pred `thenTc` \ pred' ->
+ 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 `thenNF_Tc` \ dfun_name ->
- returnNF_Tc (Just (dfun_name, clas, tycon, tyvars, constraints), Nothing)
+ = 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
- extra_constraints | offensive_class = tyConTheta tycon
- | otherwise = []
-
- offensive_class = classKey clas `elem` needsDataDeclCtxtClassKeys
-
-
- mk_eqn_help NewType tycon clas tys
- = doptsTc Opt_GlasgowExts `thenTc` \ gla_exts ->
- if can_derive_via_isomorphism && (gla_exts || standard_instance) then
- -- Go ahead and use the isomorphism
- new_dfun_name clas tycon `thenNF_Tc` \ dfun_name ->
- returnTc (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
+ 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
+ traceTc (text "newtype deriving:" <+> ppr tycon <+> ppr rep_tys) `thenM_`
+ new_dfun_name clas tycon `thenM` \ dfun_name ->
+ 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:
+ -- newtype A = MkA [A]
+ -- Don't want
+ -- instance Eq [A] => Eq A !!
-- Check that eta reduction is OK
-- (a) the dropped-off args are identical
&& (tyVarsOfTypes args_to_keep `subVarSet` mkVarSet tyvars_to_keep)
cant_derive_err = derivingThingErr clas tys tycon tyvars_to_keep
- 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)
+ standard_class gla_exts clas = key `elem` derivableClassKeys
+ || (gla_exts && (key == typeableClassKey || key == dataClassKey))
+ where
+ key = classKey clas
- bale_out err = addErrTc err `thenNF_Tc_` returnNF_Tc (Nothing, Nothing)
- ------------------------------------------------------------------
- chk_out :: Class -> TyCon -> [TcType] -> Maybe FastString
- chk_out clas tycon tys
- | not (null 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
- where
- data_cons = tyConDataCons tycon
- is_enumeration = isEnumerationTyCon tycon
- is_single_con = maybeToBool (maybeTyConSingleCon tycon)
- is_enumeration_or_single = is_enumeration || is_single_con
- single_nullary_why = SLIT("one constructor data type or type with all nullary constructors expected")
- nullary_why = SLIT("data type with all nullary constructors expected")
- no_cons_why = SLIT("type has no data constructors")
- non_std_why = SLIT("not a derivable class")
- existential_why = 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
- = iterateDeriv initial_solutions
+solveDerivEqns orig_eqns
+ = iterateDeriv 1 initial_solutions
where
-- The initial solutions for the equations claim that each
-- instance has an empty context; this solution is certainly
-- compares it with the current one; finishes if they are the
-- same, otherwise recurses with the new solutions.
-- It fails if any iteration fails
- iterateDeriv :: [DerivSoln] ->TcM [DFunId]
- iterateDeriv current_solns
- = getDOptsTc `thenNF_Tc` \ dflags ->
- let
- dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns
- inst_env = extend_inst_env dflags inst_env_in dfuns
+ iterateDeriv :: Int -> [DerivSoln] ->TcM [DFunId]
+ iterateDeriv n current_solns
+ | n > 20 -- Looks as if we are in an infinite loop
+ -- This can happen if we have -fallow-undecidable-instances
+ -- (See TcSimplify.tcSimplifyDeriv.)
+ = pprPanic "solveDerivEqns: probable loop"
+ (vcat (map pprDerivEqn orig_eqns) $$ ppr current_solns)
+ | otherwise
+ = let
+ dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns
in
- checkNoErrsTc (
+ checkNoErrs (
-- Extend the inst info from the explicit instance decls
-- with the current set of solutions, and simplify each RHS
- tcSetInstEnv inst_env $
- mapTc gen_soln orig_eqns
- ) `thenTc` \ new_solns ->
+ tcExtendTempInstEnv dfuns $
+ mappM gen_soln orig_eqns
+ ) `thenM` \ new_solns ->
if (current_solns == new_solns) then
- returnTc dfuns
+ returnM dfuns
else
- iterateDeriv new_solns
+ iterateDeriv (n+1) new_solns
------------------------------------------------------------------
gen_soln (_, clas, tc,tyvars,deriv_rhs)
- = tcAddSrcLoc (getSrcLoc tc) $
- tcAddErrCtxt (derivCtxt (Just clas) tc) $
- tcSimplifyDeriv tyvars deriv_rhs `thenTc` \ theta ->
- returnTc (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
+ = addSrcLoc (getSrcLoc tc) $
+ addErrCtxt (derivCtxt (Just clas) tc) $
+ tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta ->
+ returnM (sortLt (<) theta) -- Canonicalise before returning the soluction
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)]
\end{code}
%************************************************************************
\begin{code}
-- Generate the method bindings for the required instance
--- (paired with class name, as we need that when renaming
+-- (paired with DFunId, as we need that when renaming
-- the method binds)
-gen_bind :: (Name -> Maybe Fixity) -> DFunId -> (Name, RdrNameMonoBinds)
-gen_bind get_fixity dfun
- = (cls_nm, binds)
- where
- cls_nm = className clas
- (clas, tycon) = simpleDFunClassTyCon dfun
-
- binds = assoc "gen_bind:bad derived class" gen_list
- (nameUnique cls_nm) tycon
-
- 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 get_fixity)
- ,(readClassKey, gen_Read_binds get_fixity)
- ]
+gen_bind :: DFunId -> TcM (DFunId, (RdrNameMonoBinds, RdrNameMonoBinds))
+gen_bind dfun
+ = getFixityEnv `thenM` \ fix_env ->
+ let
+ (clas, tycon) = simpleDFunClassTyCon dfun
+ gen_binds_fn = assoc "gen_bind:bad derived class"
+ gen_list (getUnique clas)
+
+ 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}
TagThingWanted)]
gen_taggery_Names dfuns
- = foldlTc do_con2tag [] tycons_of_interest `thenTc` \ names_so_far ->
- foldlTc do_tag2con names_so_far tycons_of_interest
+ = foldlM do_con2tag [] tycons_of_interest `thenM` \ names_so_far ->
+ foldlM do_tag2con names_so_far tycons_of_interest
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))
- = returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag)
+ = returnM ((con2tag_RDR tycon, tycon, GenCon2Tag)
: acc_Names)
| otherwise
- = returnTc acc_Names
+ = returnM acc_Names
do_tag2con acc_Names tycon
| isDataTyCon tycon &&
(we_are_deriving enumClassKey tycon ||
we_are_deriving ixClassKey tycon
&& isEnumerationTyCon tycon)
- = returnTc ( (tag2con_RDR tycon, tycon, GenTag2Con)
+ = returnM ( (tag2con_RDR tycon, tycon, GenTag2Con)
: (maxtag_RDR tycon, tycon, GenMaxTag)
: acc_Names)
| otherwise
- = returnTc acc_Names
+ = returnM acc_Names
we_are_deriving clas_key tycon
= is_in_eqns clas_key tycon all_CTs
\begin{code}
derivingThingErr clas tys tycon tyvars why
= sep [hsep [ptext SLIT("Can't make a derived instance of"), quotes (ppr pred)],
- parens (ptext why)]
+ parens why]
where
pred = mkClassPred clas (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars)])
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