#include "HsVersions.h"
-import HsSyn ( HsBinds(..), MonoBinds(..), collectMonoBinders )
+import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..),
+ collectMonoBinders )
import RdrHsSyn ( RdrNameMonoBinds )
-import RnHsSyn ( RenamedHsBinds )
-import CmdLineOpts ( opt_D_dump_deriv )
+import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPred )
+import CmdLineOpts ( DynFlag(..) )
-import TcMonad
-import TcEnv ( InstEnv, getEnvTyCons, tcSetInstEnv, newDFunName )
+import TcRnMonad
+import TcEnv ( tcExtendTempInstEnv, newDFunName,
+ InstInfo(..), pprInstInfo, InstBindings(..),
+ pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv
+ )
import TcGenDeriv -- Deriv stuff
-import TcInstUtil ( InstInfo(..), buildInstanceEnv )
-import TcSimplify ( tcSimplifyThetas )
+import InstEnv ( simpleDFunClassTyCon )
+import TcMonoType ( tcHsPred )
+import TcSimplify ( tcSimplifyDeriv )
import RnBinds ( rnMethodBinds, rnTopMonoBinds )
-import RnEnv ( bindLocatedLocalsRn )
-import RnMonad ( RnNameSupply,
- renameSourceCode, thenRn, mapRn, returnRn )
-
-import Bag ( Bag, emptyBag, unionBags, listToBag )
-import Class ( classKey, Class )
-import ErrUtils ( dumpIfSet, Message )
+import RnEnv ( bindLocalsFV )
+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 Id ( mkVanillaId )
-import DataCon ( dataConArgTys, isNullaryDataCon, isExistentialDataCon )
-import PrelInfo ( needsDataDeclCtxtClassKeys )
+import DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon )
import Maybes ( maybeToBool, catMaybes )
-import Module ( Module )
-import Name ( isLocallyDefined, getSrcLoc, NamedThing(..) )
+import Name ( Name, getSrcLoc, nameUnique )
+import NameSet
import RdrName ( RdrName )
-import RnMonad ( FixityEnv )
-import TyCon ( tyConTyVars, tyConDataCons, tyConDerivings,
+import TyCon ( tyConTyVars, tyConDataCons, tyConArity,
tyConTheta, maybeTyConSingleCon, isDataTyCon,
- isEnumerationTyCon, isAlgTyCon, TyCon
+ isEnumerationTyCon, isRecursiveTyCon, TyCon
)
-import Type ( TauType, mkTyVarTys, mkTyConApp,
- mkSigmaTy, mkDictTy, isUnboxedType,
- splitAlgTyConApp, classesToPreds
- )
-import TysWiredIn ( voidTy )
-import Var ( TyVar )
-import Unique -- Keys stuff
-import Bag ( bagToList )
-import Util ( zipWithEqual, sortLt, removeDups, assoc, thenCmp )
+import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe,
+ isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys,
+ tcEqTypes, tcSplitAppTys, mkAppTys )
+import Var ( TyVar, tyVarKind )
+import VarSet ( mkVarSet, subVarSet )
+import PrelNames
+import Util ( zipWithEqual, sortLt, notNull )
+import ListSetOps ( removeDups, assoc )
import Outputable
\end{code}
So, here are the synonyms for the ``equation'' structures:
\begin{code}
-type DerivEqn = (Class, TyCon, [TyVar], DerivRhs)
- -- The tyvars bind all the variables in the RHS
- -- NEW: it's convenient to re-use InstInfo
- -- We'll "panic" out some fields...
+type DerivEqn = (Name, Class, TyCon, [TyVar], DerivRhs)
+ -- The Name is the name for the DFun we'll build
+ -- The tyvars bind all the variables in the RHS
-type DerivRhs = [(Class, [TauType])] -- Same as a ThetaType!
+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 :: Module -- name of module under scrutiny
- -> FixityEnv -- for the deriving code (Show/Read.)
- -> RnNameSupply -- for "renaming" bits of generated code
- -> Bag InstInfo -- What we already know about instances
- -> TcM s (Bag InstInfo, -- The generated "instance decls".
- RenamedHsBinds) -- Extra generated bindings
+tcDeriving :: [RenamedTyClDecl] -- All type constructors
+ -> TcM ([InstInfo], -- The generated "instance decls".
+ RenamedHsBinds, -- Extra generated bindings
+ FreeVars) -- These are free in the generated bindings
-tcDeriving mod fixs rn_name_supply inst_decl_infos_in
- = recoverTc (returnTc (emptyBag, EmptyBinds)) $
+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 `thenTc` \ eqns ->
- if null eqns then
- returnTc (emptyBag, EmptyBinds)
- else
+ 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
+
+ deriveOrdinaryStuff 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)
+
+ 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
- -- Take the equation list and solve it, to deliver a list of
+-----------------------------------------
+deriveOrdinaryStuff [] -- Short cut
+ = returnM ([], EmptyBinds, emptyFVs)
+
+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_decl_infos_in eqns `thenTc` \ new_inst_infos ->
+ 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_inst_infos `thenTc` \ nm_alist_etc ->
-
+ gen_taggery_Names new_dfuns `thenM` \ nm_alist_etc ->
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 fixs) new_inst_infos
- mbinders = bagToList (collectMonoBinders extra_mbinds)
+ 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.
- (rn_method_binds_s, rn_extra_binds)
- = renameSourceCode mod rn_name_supply (
- 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)
- )
+ -- 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_meths method_binds_s `thenM` \ (rn_method_binds_s, fvs_s) ->
+ returnM ((rn_method_binds_s, rn_extra_binds),
+ duUses dus `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
- mapNF_Tc gen_inst_info (new_inst_infos `zip` rn_method_binds_s) `thenNF_Tc` \ really_new_inst_infos ->
-
- ioToTc (dumpIfSet opt_D_dump_deriv "Derived instances"
- (ddump_deriving really_new_inst_infos rn_extra_binds)) `thenTc_`
+ returnM (new_inst_infos, rn_extra_binds, fvs)
- returnTc (listToBag really_new_inst_infos, rn_extra_binds)
where
- ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc
- ddump_deriving inst_infos extra_binds
- = vcat (map pp_info inst_infos) $$ ppr extra_binds
- where
- pp_info (InstInfo clas tvs [ty] inst_decl_theta _ mbinds _ _)
- = ppr (mkSigmaTy tvs inst_decl_theta' (mkDictTy clas [ty]))
- $$
- ppr mbinds
- where inst_decl_theta' = classesToPreds inst_decl_theta
-
- -- Paste the dfun id and method binds into the InstInfo
- gen_inst_info (InstInfo clas tyvars tys@(ty:_) inst_decl_theta _ _ locn _, meth_binds)
- = newDFunName mod clas tys locn `thenNF_Tc` \ dfun_name ->
- let
- dfun_id = mkDictFunId dfun_name clas tyvars tys inst_decl_theta
- in
- returnNF_Tc (InstInfo clas tyvars tys inst_decl_theta
- dfun_id meth_binds locn [])
-
- rn_meths meths = rnMethodBinds meths `thenRn` \ (meths', _) -> returnRn meths'
- -- Ignore the free vars returned
+ -- 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 = VanillaInst binds [] }
+
+ rn_meths (cls, meths) = rnMethodBinds cls [] meths
\end{code}
all those.
\begin{code}
-makeDerivEqns :: TcM s [DerivEqn]
-
-makeDerivEqns
- = tcGetEnv `thenNF_Tc` \ env ->
- let
- local_data_tycons = filter (\tc -> isLocallyDefined tc && isAlgTyCon tc)
- (getEnvTyCons env)
+makeDerivEqns :: [RenamedTyClDecl]
+ -> TcM ([DerivEqn], -- Ordinary derivings
+ [InstInfo]) -- Special newtype derivings
- think_about_deriving = need_deriving local_data_tycons
- (derive_these, _) = removeDups cmp_deriv think_about_deriving
- in
- if null local_data_tycons then
- returnTc [] -- Bale out now
- else
- mapTc mk_eqn derive_these `thenTc` \ maybe_eqns ->
- returnTc (catMaybes maybe_eqns)
+makeDerivEqns tycl_decls
+ = mapAndUnzipM mk_eqn derive_these `thenM` \ (maybe_ordinaries, maybe_newtypes) ->
+ returnM (catMaybes maybe_ordinaries, catMaybes maybe_newtypes)
where
------------------------------------------------------------------
- need_deriving :: [TyCon] -> [(Class, TyCon)]
- -- find the tycons that have `deriving' clauses;
-
- need_deriving tycons_to_consider
- = foldr (\ tycon acc -> [(clas,tycon) | clas <- tyConDerivings tycon] ++ acc)
- []
- tycons_to_consider
+ derive_these :: [(NewOrData, Name, RenamedHsPred)]
+ -- Find the (nd, TyCon, Pred) pairs that must be `derived'
+ -- NB: only source-language decls have deriving, no imported ones do
+ derive_these = [ (nd, tycon, pred)
+ | TyData {tcdND = nd, tcdName = tycon, tcdDerivs = Just preds} <- tycl_decls,
+ pred <- preds ]
------------------------------------------------------------------
- cmp_deriv :: (Class, TyCon) -> (Class, TyCon) -> Ordering
- cmp_deriv (c1, t1) (c2, t2)
- = (c1 `compare` c2) `thenCmp` (t1 `compare` t2)
-
- ------------------------------------------------------------------
- mk_eqn :: (Class, TyCon) -> NF_TcM s (Maybe DerivEqn)
- -- we swizzle the tyvars and datacons out of the tycon
+ 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 (clas, tycon)
- = case chk_out clas tycon of
- Just err -> addErrTc err `thenNF_Tc_`
- returnNF_Tc Nothing
- Nothing -> returnNF_Tc (Just (clas, tycon, tyvars, constraints))
+ mk_eqn (new_or_data, tycon_name, pred)
+ = 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 `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
+
+ ------------------------------------------------------------------
+ mk_eqn_help DataType tycon clas tys
+ | Just err <- chk_out 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
- clas_key = classKey clas
- tyvars = tyConTyVars tycon -- ToDo: Do we need new tyvars ???
- tyvar_tys = mkTyVarTys tyvars
+ tyvars = tyConTyVars tycon
data_cons = tyConDataCons tycon
-
- constraints = extra_constraints ++ concat (map mk_constraints data_cons)
-
- -- "extra_constraints": see notes above about contexts on data decls
- extra_constraints
- | offensive_class = tyConTheta tycon
- | otherwise = []
- where
- offensive_class = clas_key `elem` needsDataDeclCtxtClassKeys
-
- mk_constraints data_con
- = [ (clas, [arg_ty])
- | arg_ty <- instd_arg_tys,
- not (isUnboxedType arg_ty) -- No constraints for unboxed types?
- ]
- where
- instd_arg_tys = dataConArgTys data_con tyvar_tys
+ 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
+ extra_constraints = tyConTheta tycon
+
+ 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
+ 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 }))
+ else
+ if standard_instance then
+ mk_eqn_help DataType tycon clas [] -- Go via bale-out route
+ else
+ -- Non-standard instance
+ if gla_exts then
+ -- Too hard
+ bale_out cant_derive_err
+ else
+ -- Just complain about being a non-std instance
+ bale_out non_std_err
+ where
+ -- Here is the plan for newtype derivings. We see
+ -- 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 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)
+
+ clas_tyvars = classTyVars clas
+ kind = tyVarKind (last clas_tyvars)
+ -- Kind of the thing we want to instance
+ -- e.g. argument kind of Monad, *->*
+
+ (arg_kinds, _) = tcSplitFunTys kind
+ n_args_to_drop = length arg_kinds
+ -- Want to drop 1 arg from (T s a) and (ST s a)
+ -- to get instance Monad (ST s) => Monad (T s)
+
+ -- 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 = 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
+
+ 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
+
+ standard_instance = null tys && classKey clas `elem` derivableClassKeys
+ right_arity = length tys + 1 == classArity clas
+
+ can_derive_via_isomorphism
+ = not (clas `hasKey` readClassKey) -- Never derive Read,Show this way
+ && not (clas `hasKey` showClassKey)
+ && right_arity -- Well kinded;
+ -- eg not: newtype T ... deriving( ST )
+ -- because ST needs *2* type params
+ && n_tyvars_to_keep >= 0 -- Well kinded;
+ -- eg not: newtype T = T Int deriving( Monad )
+ && n_args_to_keep >= 0 -- Well kinded:
+ -- 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
+ -- (b) the remaining type args mention
+ -- only the remaining type variables
+ eta_ok = (args_to_drop `tcEqTypes` mkTyVarTys tyvars_to_drop)
+ && (tyVarsOfTypes args_to_keep `subVarSet` mkVarSet tyvars_to_keep)
+
+ cant_derive_err = derivingThingErr clas tys tycon tyvars_to_keep
+ (vcat [ptext SLIT("even with cunning newtype deriving:"),
+ if right_arity then empty else
+ quotes (ppr (mkClassPred clas tys)) <+> ptext SLIT("does not have arity 1"),
+ if n_tyvars_to_keep >= 0 && n_args_to_keep >= 0 then empty else
+ ptext SLIT("the type constructor has wrong kind"),
+ if n_args_to_keep >= 0 then empty else
+ ptext SLIT("representation type has wrong kind"),
+ if eta_ok then empty else
+ ptext SLIT("the eta-reduction property does not hold"),
+ if not (isRecursiveTyCon tycon) then empty else
+ ptext SLIT("the newtype is recursive")
+ ])
+
+ 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 -> Maybe Message
- chk_out clas tycon
- | clas `hasKey` enumClassKey && not is_enumeration = bog_out nullary_why
- | clas `hasKey` boundedClassKey && not is_enumeration_or_single = bog_out single_nullary_why
- | clas `hasKey` ixClassKey && not is_enumeration_or_single = bog_out single_nullary_why
- | any isExistentialDataCon (tyConDataCons tycon) = Just (existentialErr clas tycon)
- | otherwise = Nothing
+ chk_out :: Class -> TyCon -> [TcType] -> Maybe SDoc
+ chk_out clas tycon tys
+ | notNull tys = Just ty_args_why
+ | not (getUnique clas `elem` derivableClassKeys) = 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
+ | 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")
+ 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)")
+
+ pred = mkClassPred clas tys
+
+non_std_why clas = quotes (ppr clas) <+> ptext SLIT("is not a derivable class")
- bog_out why = Just (derivingThingErr clas tycon why)
+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
\end{code}
%************************************************************************
\end{itemize}
\begin{code}
-solveDerivEqns :: Bag InstInfo
- -> [DerivEqn]
- -> TcM s [InstInfo] -- Solns in same order as eqns.
- -- This bunch is Absolutely minimal...
+solveDerivEqns :: [DerivEqn]
+ -> TcM [DFunId] -- Solns in same order as eqns.
+ -- This bunch is Absolutely minimal...
-solveDerivEqns inst_decl_infos_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 s [InstInfo]
- iterateDeriv current_solns
- = checkNoErrsTc (iterateOnce current_solns) `thenTc` \ (new_inst_infos, new_solns) ->
+ 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
+ checkNoErrs (
+ -- Extend the inst info from the explicit instance decls
+ -- with the current set of solutions, and simplify each RHS
+ tcExtendTempInstEnv dfuns $
+ mappM gen_soln orig_eqns
+ ) `thenM` \ new_solns ->
if (current_solns == new_solns) then
- returnTc new_inst_infos
+ returnM dfuns
else
- iterateDeriv new_solns
+ iterateDeriv (n+1) new_solns
------------------------------------------------------------------
- iterateOnce current_solns
- = -- Extend the inst info from the explicit instance decls
- -- with the current set of solutions, giving a
-
- add_solns inst_decl_infos_in orig_eqns current_solns
- `thenNF_Tc` \ (new_inst_infos, inst_env) ->
-
- -- Simplify each RHS
-
- tcSetInstEnv inst_env (
- listTc [ tcAddErrCtxt (derivCtxt tc) $
- tcSimplifyThetas deriv_rhs
- | (_,tc,_,deriv_rhs) <- orig_eqns ]
- ) `thenTc` \ next_solns ->
-
- -- Canonicalise the solutions, so they compare nicely
- let canonicalised_next_solns
- = [ sortLt (<) next_soln | next_soln <- next_solns ]
- in
- returnTc (new_inst_infos, canonicalised_next_solns)
-\end{code}
-\begin{code}
-add_solns :: Bag InstInfo -- The global, non-derived ones
- -> [DerivEqn] -> [DerivSoln]
- -> NF_TcM s ([InstInfo], -- The new, derived ones
- InstEnv)
- -- the eqns and solns move "in lockstep"; we have the eqns
- -- because we need the LHS info for addClassInstance.
+ gen_soln (_, clas, tc,tyvars,deriv_rhs)
+ = addSrcLoc (getSrcLoc tc) $
+ addErrCtxt (derivCtxt (Just clas) tc) $
+ tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta ->
+ returnM (sortLt (<) theta) -- Canonicalise before returning the soluction
-add_solns inst_infos_in eqns solns
-
- = discardErrsTc (buildInstanceEnv all_inst_infos) `thenNF_Tc` \ inst_env ->
- -- We do the discard-errs so that we don't get repeated error messages
- -- about duplicate instances.
- -- They'll appear later, when we do the top-level buildInstanceEnv.
-
- returnNF_Tc (new_inst_infos, inst_env)
- where
- new_inst_infos = zipWithEqual "add_solns" mk_deriv_inst_info eqns solns
-
- all_inst_infos = inst_infos_in `unionBags` listToBag new_inst_infos
-
- mk_deriv_inst_info (clas, tycon, tyvars, _) theta
- = InstInfo clas tyvars [mkTyConApp tycon (mkTyVarTys tyvars)]
- theta
- dummy_dfun_id
- (my_panic "binds") (getSrcLoc tycon)
- (my_panic "upragmas")
- where
- dummy_dfun_id
- = mkVanillaId (getName tycon) dummy_dfun_ty
- -- The name is getSrcLoc'd in an error message
-
- theta' = classesToPreds theta
- dummy_dfun_ty = mkSigmaTy tyvars theta' voidTy
- -- All we need from the dfun is its "theta" part, used during
- -- equation simplification (tcSimplifyThetas). The final
- -- dfun_id will have the superclass dictionaries as arguments too,
- -- but that'll be added after the equations are solved. For now,
- -- it's enough just to make a dummy dfun with the simple theta part.
- --
- -- The part after the theta is dummied here as voidTy; actually it's
- -- (C (T a b)), but it doesn't seem worth constructing it.
- -- We can't leave it as a panic because to get the theta part we
- -- have to run down the type!
-
- my_panic str = panic "add_soln" -- pprPanic ("add_soln:"++str) (hsep [char ':', ppr clas, ppr tycon])
+mk_deriv_dfun (dfun_name, clas, tycon, 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 generating dict
--- names.)
-gen_bind :: FixityEnv -> InstInfo -> RdrNameMonoBinds
-gen_bind fixities (InstInfo clas _ [ty] _ _ _ _ _)
- | not from_here = EmptyMonoBinds
- | clas `hasKey` showClassKey = gen_Show_binds fixities tycon
- | clas `hasKey` readClassKey = gen_Read_binds fixities tycon
- | otherwise
+-- (paired with class name, as we need that when renaming
+-- the method binds)
+gen_bind :: DFunId -> TcM (Name, RdrNameMonoBinds)
+gen_bind 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"
- [(eqClassKey, gen_Eq_binds)
- ,(ordClassKey, gen_Ord_binds)
- ,(enumClassKey, gen_Enum_binds)
- ,(boundedClassKey, gen_Bounded_binds)
- ,(ixClassKey, gen_Ix_binds)
- ]
- (classKey clas)
- tycon
+ gen_list (nameUnique cls_nm)
where
- from_here = isLocallyDefined tycon
- (tycon,_,_) = splitAlgTyConApp ty
+ 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)
+ ]
\end{code}
con2tag_Foo :: Foo ... -> Int#
tag2con_Foo :: Int -> Foo ... -- easier if Int, not Int#
-maxtag_Foo :: Int -- ditto (NB: not unboxed)
+maxtag_Foo :: Int -- ditto (NB: not unlifted)
We have a @con2tag@ function for a tycon if:
If we have a @tag2con@ function, we also generate a @maxtag@ constant.
\begin{code}
-gen_taggery_Names :: [InstInfo]
- -> TcM s [(RdrName, -- for an assoc list
- TyCon, -- related tycon
- TagThingWanted)]
-
-gen_taggery_Names inst_infos
- = --pprTrace "gen_taggery:\n" (vcat [hsep [ppr c, ppr t] | (c,t) <- all_CTs]) $
- foldlTc do_con2tag [] tycons_of_interest `thenTc` \ names_so_far ->
- foldlTc do_tag2con names_so_far tycons_of_interest
+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
where
- all_CTs = [ (c, get_tycon ty) | (InstInfo c _ [ty] _ _ _ _ _) <- inst_infos ]
-
- get_tycon ty = case splitAlgTyConApp ty of { (tc, _, _) -> tc }
-
- all_tycons = map snd all_CTs
+ all_CTs = map simpleDFunClassTyCon dfuns
+ all_tycons = map snd all_CTs
(tycons_of_interest, _) = removeDups compare all_tycons
do_con2tag acc_Names 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
is_in_eqns clas_key tycon ((c,t):cts)
= (clas_key == classKey c && tycon == t)
|| is_in_eqns clas_key tycon cts
-
\end{code}
\begin{code}
-derivingThingErr :: Class -> TyCon -> FAST_STRING -> Message
-
-derivingThingErr clas tycon why
- = sep [hsep [ptext SLIT("Can't make a derived instance of"), quotes (ppr clas)],
- hsep [ptext SLIT("for the type"), quotes (ppr tycon)],
- parens (ptext why)]
+derivingThingErr clas tys tycon tyvars why
+ = sep [hsep [ptext SLIT("Can't make a derived instance of"), quotes (ppr pred)],
+ parens why]
+ where
+ pred = mkClassPred clas (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars)])
-existentialErr clas tycon
- = sep [ptext SLIT("Can't derive any instances for type") <+> quotes (ppr tycon),
- ptext SLIT("because it has existentially-quantified constructor(s)")]
+malformedPredErr tycon pred = ptext SLIT("Illegal deriving item") <+> ppr pred
-derivCtxt tycon
- = ptext SLIT("When deriving classes for") <+> quotes (ppr tycon)
+derivCtxt :: Maybe Class -> TyCon -> SDoc
+derivCtxt maybe_cls tycon
+ = ptext SLIT("When deriving") <+> cls <+> ptext SLIT("for type") <+> quotes (ppr tycon)
+ where
+ cls = case maybe_cls of
+ Nothing -> ptext SLIT("instances")
+ Just c -> ptext SLIT("the") <+> quotes (ppr c) <+> ptext SLIT("instance")
\end{code}
+
projects / ghc-hetmet.git / blobdiff