%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcDeriv]{Deriving}
#include "HsVersions.h"
-import HsSyn ( HsBinds(..), MonoBinds(..), collectMonoBinders )
-import RdrHsSyn ( RdrName, RdrNameMonoBinds )
-import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds )
+import HsSyn ( HsBinds(..), MonoBinds(..), collectLocatedMonoBinders )
+import RdrHsSyn ( RdrNameMonoBinds )
+import RnHsSyn ( RenamedHsBinds )
+import CmdLineOpts ( opt_D_dump_deriv )
import TcMonad
-import Inst ( InstanceMapper )
-import TcEnv ( getEnv_TyCons, tcLookupClassByKey )
-import TcKind ( TcKind )
+import TcEnv ( InstEnv, getEnvTyCons, tcSetInstEnv, newDFunName )
import TcGenDeriv -- Deriv stuff
-import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs )
+import TcInstUtil ( InstInfo(..), pprInstInfo, simpleDFunClassTyCon, extendInstEnv )
import TcSimplify ( tcSimplifyThetas )
import RnBinds ( rnMethodBinds, rnTopMonoBinds )
-import RnEnv ( newDfunName, bindLocatedLocalsRn )
-import RnMonad ( RnM, RnDown, SDown, RnNameSupply(..),
+import RnEnv ( bindLocatedLocalsRn )
+import RnMonad ( RnNameSupply,
renameSourceCode, thenRn, mapRn, returnRn )
import Bag ( Bag, emptyBag, unionBags, listToBag )
import Class ( classKey, Class )
-import ErrUtils ( ErrMsg )
+import ErrUtils ( dumpIfSet, Message )
import MkId ( mkDictFunId )
-import Id ( dataConArgTys, isNullaryDataCon )
+import Id ( mkVanillaId )
+import DataCon ( dataConArgTys, isNullaryDataCon, isExistentialDataCon )
import PrelInfo ( needsDataDeclCtxtClassKeys )
-import Maybes ( maybeToBool )
-import Name ( isLocallyDefined, getSrcLoc, Provenance,
- Name{--O only-}, Module, NamedThing(..),
- OccName, nameOccName
- )
-import SrcLoc ( mkGeneratedSrcLoc, SrcLoc )
+import Maybes ( maybeToBool, catMaybes )
+import Module ( Module )
+import Name ( isLocallyDefined, getSrcLoc, NamedThing(..) )
+import RdrName ( RdrName )
+import RnMonad ( FixityEnv )
+
import TyCon ( tyConTyVars, tyConDataCons, tyConDerivings,
tyConTheta, maybeTyConSingleCon, isDataTyCon,
isEnumerationTyCon, isAlgTyCon, TyCon
)
-import Type ( GenType(..), TauType, mkTyVarTys, mkTyConApp,
+import Type ( TauType, mkTyVarTys, mkTyConApp,
mkSigmaTy, mkDictTy, isUnboxedType,
- splitAlgTyConApp
+ splitAlgTyConApp, classesToPreds
)
-import TysPrim ( voidTy )
-import TyVar ( GenTyVar, TyVar )
-import Unique -- Keys stuff
+import TysWiredIn ( voidTy )
+import Var ( TyVar )
+import PrelNames
import Bag ( bagToList )
-import Util ( zipWithEqual, sortLt, removeDups, assoc, thenCmp )
+import Util ( zipWithEqual, sortLt, thenCmp )
+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!
%************************************************************************
\begin{code}
-tcDeriving :: Module -- name of module under scrutiny
- -> 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
- SDoc) -- Printable derived instance decls;
- -- for debugging via -ddump-derivings.
+tcDeriving :: PersistentRenamerState
+ -> Module -- name of module under scrutiny
+ -> InstEnv -- What we already know about instances
+ -> TcM ([InstInfo], -- The generated "instance decls".
+ RenamedHsBinds) -- Extra generated bindings
-tcDeriving modname rn_name_supply inst_decl_infos_in
- = recoverTc (returnTc (emptyBag, EmptyBinds, empty)) $
+tcDeriving prs mod inst_env_in local_tycons
+ = recoverTc (returnTc ([], EmptyBinds)) $
-- Fish the "deriving"-related information out of the TcEnv
-- and make the necessary "equations".
- makeDerivEqns `thenTc` \ eqns ->
+ makeDerivEqns local_tycons `thenTc` \ eqns ->
if null eqns then
- returnTc (emptyBag, EmptyBinds, text "No derivings")
+ returnTc ([], EmptyBinds)
else
-- 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 inst_env_in eqns `thenTc` \ new_dfuns ->
-- Now augment the InstInfos, adding in the rather boring
-- actual-code-to-do-the-methods binds. We may also need to
-- "con2tag" and/or "tag2con" functions. We do these
-- separately.
- gen_taggery_Names new_inst_infos `thenTc` \ nm_alist_etc ->
-
+ gen_taggery_Names new_dfuns `thenTc` \ nm_alist_etc ->
+ tcGetEnv `thenNF_Tc` \ env ->
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 new_inst_infos
- mbinders = bagToList (collectMonoBinders extra_mbinds)
+ method_binds_s = map (gen_bind (tcGST env)) new_dfuns
+ mbinders = collectLocatedMonoBinders extra_mbinds
-- Rename to get RenamedBinds.
-- The only tricky bit is that the extra_binds must scope over the
-- method bindings for the instances.
- (dfun_names_w_method_binds, rn_extra_binds)
- = renameSourceCode modname rn_name_supply (
+ (rn_method_binds_s, rn_extra_binds)
+ = renameSourceCode mod prs (
bindLocatedLocalsRn (ptext (SLIT("deriving"))) mbinders $ \ _ ->
- rnTopMonoBinds extra_mbinds [] `thenRn` \ rn_extra_binds ->
- mapRn rn_one method_binds_s `thenRn` \ dfun_names_w_method_binds ->
- returnRn (dfun_names_w_method_binds, rn_extra_binds)
+ 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)
)
- rn_one (cl_nm, tycon_nm, meth_binds)
- = newDfunName cl_nm tycon_nm
- Nothing mkGeneratedSrcLoc `thenRn` \ dfun_name ->
- rnMethodBinds meth_binds `thenRn` \ rn_meth_binds ->
- returnRn (dfun_name, rn_meth_binds)
-
- really_new_inst_infos = map (gen_inst_info modname)
- (new_inst_infos `zip` dfun_names_w_method_binds)
-
- ddump_deriv = ddump_deriving really_new_inst_infos rn_extra_binds
in
- --pprTrace "derived:\n" (ddump_deriv) $
+ mapNF_Tc gen_inst_info (new_dfuns `zip` rn_method_binds_s) `thenNF_Tc` \ new_inst_infos ->
+
+ ioToTc (dumpIfSet opt_D_dump_deriv "Derived instances"
+ (ddump_deriving new_inst_infos rn_extra_binds)) `thenTc_`
- returnTc (listToBag really_new_inst_infos,
- rn_extra_binds,
- ddump_deriv)
+ returnTc (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])
+ = vcat (map pprInstInfo 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)
+
+ -- Make a Real dfun instead of the dummy one we have so far
+ gen_inst_info (dfun, binds)
+ = InstInfo { iLocal = True,
+ iClass = clas, iTyVars = tyvars,
+ iTys = tys, iTheta = theta,
+ iDFunId = dfun, iBinds = binds,
+ iLoc = getSrcLoc dfun, iPrags = [] }
+ where
+ (tyvars, theta, tau) = splitSigmaTy dfun
+ (clas, tys) = splitDictTy tau
+
+ rn_meths meths = rnMethodBinds [] meths `thenRn` \ (meths', _) -> returnRn meths'
+ -- Ignore the free vars returned
\end{code}
all those.
\begin{code}
-makeDerivEqns :: TcM s [DerivEqn]
+makeDerivEqns :: Module -> [TyCon] -> TcM [DerivEqn]
-makeDerivEqns
- = tcGetEnv `thenNF_Tc` \ env ->
- let
- local_data_tycons = filter (\tc -> isLocallyDefined tc && isAlgTyCon tc)
- (getEnv_TyCons env)
+makeDerivEqns this_mod local_tycons
+ = let
+ think_about_deriving = need_deriving local_tycons
+ (derive_these, _) = removeDups cmp_deriv think_about_deriving
in
if null local_data_tycons then
- -- Bale out now; evalClass may not be loaded if there aren't any
- returnTc []
+ returnTc [] -- Bale out now
else
- tcLookupClassByKey evalClassKey `thenNF_Tc` \ eval_clas ->
- let
- think_about_deriving = need_deriving eval_clas local_data_tycons
- (derive_these, _) = removeDups cmp_deriv think_about_deriving
- eqns = map mk_eqn derive_these
- in
- mapTc chk_out think_about_deriving `thenTc_`
- returnTc eqns
+ mapTc mk_eqn derive_these `thenTc` \ maybe_eqns ->
+ returnTc (catMaybes maybe_eqns)
where
------------------------------------------------------------------
- need_deriving :: Class -> [TyCon] -> [(Class, TyCon)]
+ need_deriving :: [TyCon] -> [(Class, TyCon)]
-- find the tycons that have `deriving' clauses;
- -- we handle the "every datatype in Eval" by
- -- doing a dummy "deriving" for it.
-
- need_deriving eval_clas tycons_to_consider
- = foldr ( \ tycon acc ->
- let
- acc_plus = if isLocallyDefined tycon
- then (eval_clas, tycon) : acc
- else acc
- in
- case (tyConDerivings tycon) of
- [] -> acc_plus
- cs -> [ (clas,tycon) | clas <- cs ] ++ acc_plus
- )
+
+ need_deriving tycons_to_consider
+ = foldr (\ tycon acc -> [(clas,tycon) | clas <- tyConDerivings tycon] ++ acc)
[]
tycons_to_consider
------------------------------------------------------------------
- chk_out :: (Class, TyCon) -> TcM s ()
- chk_out this_one@(clas, tycon)
- = let
- clas_key = classKey clas
-
- is_enumeration = isEnumerationTyCon tycon
- is_single_con = maybeToBool (maybeTyConSingleCon tycon)
-
- 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")
-
- chk_clas clas_uniq clas_str clas_why cond
- = if (clas_uniq == clas_key)
- then checkTc cond (derivingThingErr clas_str clas_why tycon)
- else returnTc ()
- in
- -- Are things OK for deriving Enum (if appropriate)?
- chk_clas enumClassKey (SLIT("Enum")) nullary_why is_enumeration `thenTc_`
-
- -- Are things OK for deriving Bounded (if appropriate)?
- chk_clas boundedClassKey (SLIT("Bounded")) single_nullary_why
- (is_enumeration || is_single_con) `thenTc_`
-
- -- Are things OK for deriving Ix (if appropriate)?
- chk_clas ixClassKey (SLIT("Ix.Ix")) single_nullary_why
- (is_enumeration || is_single_con)
-
- ------------------------------------------------------------------
cmp_deriv :: (Class, TyCon) -> (Class, TyCon) -> Ordering
cmp_deriv (c1, t1) (c2, t2)
= (c1 `compare` c2) `thenCmp` (t1 `compare` t2)
------------------------------------------------------------------
- mk_eqn :: (Class, TyCon) -> DerivEqn
+ mk_eqn :: (Class, TyCon) -> NF_TcM (Maybe DerivEqn)
-- we swizzle the tyvars and datacons out of the tycon
-- to make the rest of the equation
mk_eqn (clas, tycon)
- = (clas, tycon, tyvars, if_not_Eval constraints)
+ = case chk_out clas tycon of
+ Just err -> addErrTc err `thenNF_Tc_`
+ returnNF_Tc Nothing
+ Nothing -> newDFunName this_mod clas tys locn `thenNF_Tc` \ dfun_name ->
+ returnNF_Tc (Just (dfun_name, clas, tycon, tyvars, constraints))
where
clas_key = classKey clas
tyvars = tyConTyVars tycon -- ToDo: Do we need new tyvars ???
tyvar_tys = mkTyVarTys tyvars
data_cons = tyConDataCons tycon
- if_not_Eval cs = if clas_key == evalClassKey then [] else cs
-
constraints = extra_constraints ++ concat (map mk_constraints data_cons)
-- "extra_constraints": see notes above about contexts on data decls
]
where
instd_arg_tys = dataConArgTys data_con tyvar_tys
+
+ ------------------------------------------------------------------
+ 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
+ where
+ 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")
+
+ bog_out why = Just (derivingThingErr clas tycon why)
\end{code}
%************************************************************************
\end{itemize}
\begin{code}
-solveDerivEqns :: Bag InstInfo
+solveDerivEqns :: InstEnv
-> [DerivEqn]
- -> TcM s [InstInfo] -- Solns in same order as eqns.
- -- This bunch is Absolutely minimal...
+ -> TcM [DFunId] -- Solns in same order as eqns.
+ -- This bunch is Absolutely minimal...
-solveDerivEqns inst_decl_infos_in orig_eqns
+solveDerivEqns inst_env_in orig_eqns
= iterateDeriv initial_solutions
where
-- The initial solutions for the equations claim that each
-- 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 :: [DerivSoln] ->TcM [DFunId]
iterateDeriv current_solns
- = checkNoErrsTc (iterateOnce current_solns) `thenTc` \ (new_inst_infos, new_solns) ->
+ = checkNoErrsTc (iterateOnce current_solns) `thenTc` \ (new_dfuns, new_solns) ->
if (current_solns == new_solns) then
- returnTc new_inst_infos
+ returnTc new_dfuns
else
iterateDeriv new_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_mapper) ->
- let
- class_to_inst_env cls = inst_mapper cls
- in
- -- Simplify each RHS
+ add_solns inst_env_in orig_eqns current_solns `thenNF_Tc` \ (new_dfuns, inst_env) ->
- listTc [ tcAddErrCtxt (derivCtxt tc) $
- tcSimplifyThetas class_to_inst_env deriv_rhs
- | (_,tc,_,deriv_rhs) <- orig_eqns ] `thenTc` \ next_solns ->
+ -- 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 ]
+ let canonicalised_next_solns = [ sortLt (<) next_soln | next_soln <- next_solns ]
in
- returnTc (new_inst_infos, canonicalised_next_solns)
+ returnTc (new_dfuns, canonicalised_next_solns)
\end{code}
\begin{code}
-add_solns :: Bag InstInfo -- The global, non-derived ones
+add_solns :: InstEnv -- The global, non-derived ones
-> [DerivEqn] -> [DerivSoln]
- -> NF_TcM s ([InstInfo], -- The new, derived ones
- InstanceMapper)
+ -> ([DFunId], InstEnv)
-- the eqns and solns move "in lockstep"; we have the eqns
-- because we need the LHS info for addClassInstance.
-add_solns inst_infos_in eqns solns
-
- = discardErrsTc (buildInstanceEnvs all_inst_infos) `thenNF_Tc` \ inst_mapper ->
- -- 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 buildInstanceEnvs.
-
- returnNF_Tc (new_inst_infos, inst_mapper)
+add_solns inst_env_in eqns solns
+ = (new_dfuns, 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
- (my_panic "dfun_theta")
-
- dummy_dfun_id
-
- (my_panic "binds") (getSrcLoc tycon)
- (my_panic "upragmas")
- where
- dummy_dfun_id
- = mkDictFunId (getName tycon) dummy_dfun_ty bottom bottom
- -- The name is getSrcLoc'd in an error message
- where
- bottom = panic "dummy_dfun_id"
-
- 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])
+ new_dfuns = zipWithEqual "add_solns" mk_deriv_dfun eqns solns
+ (inst_env, _) = extendInstEnv inst_env_in
+ -- 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
\end{code}
%************************************************************************
-- Generate the method bindings for the required instance
-- (paired with class name, as we need that when generating dict
-- names.)
-gen_bind :: InstInfo -> ({-class-}OccName, {-tyCon-}OccName, RdrNameMonoBinds)
-gen_bind (InstInfo clas _ [ty] _ _ _ _ _ _)
- | not from_here
- = (clas_nm, tycon_nm, EmptyMonoBinds)
+gen_bind :: GlobalSymbolTable -> DFunId -> RdrNameMonoBinds
+gen_bind fixities inst
+ | not (isLocallyDefined tycon) = EmptyMonoBinds
+ | clas `hasKey` showClassKey = gen_Show_binds fixities tycon
+ | clas `hasKey` readClassKey = gen_Read_binds fixities tycon
| otherwise
- = (clas_nm, tycon_nm,
- assoc "gen_bind:bad derived class"
+ = assoc "gen_bind:bad derived class"
[(eqClassKey, gen_Eq_binds)
,(ordClassKey, gen_Ord_binds)
,(enumClassKey, gen_Enum_binds)
- ,(evalClassKey, gen_Eval_binds)
,(boundedClassKey, gen_Bounded_binds)
- ,(showClassKey, gen_Show_binds)
- ,(readClassKey, gen_Read_binds)
,(ixClassKey, gen_Ix_binds)
]
- (classKey clas)
- tycon)
+ (classKey clas)
+ tycon
where
- clas_nm = nameOccName (getName clas)
- tycon_nm = nameOccName (getName tycon)
- from_here = isLocallyDefined tycon
- (tycon,_,_) = splitAlgTyConApp ty
-
-
-gen_inst_info :: Module -- Module name
- -> (InstInfo, (Name, RenamedMonoBinds)) -- the main stuff to work on
- -> InstInfo -- the gen'd (filled-in) "instance decl"
-
-gen_inst_info modname
- (InstInfo clas tyvars tys@(ty:_) inst_decl_theta _ _ _ locn _, (dfun_name, meth_binds))
- =
- -- Generate the various instance-related Ids
- InstInfo clas tyvars tys inst_decl_theta
- dfun_theta dfun_id
- meth_binds
- locn []
- where
- (dfun_id, dfun_theta) = mkInstanceRelatedIds
- dfun_name
- clas tyvars tys
- inst_decl_theta
-
- from_here = isLocallyDefined tycon
- (tycon,_,_) = splitAlgTyConApp ty
+ (clas, tycon) = simpleDFunClassTyCon dfun
\end{code}
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 ->
+gen_taggery_Names :: [DFunId]
+ -> TcM [(RdrName, -- for an assoc list
+ TyCon, -- related tycon
+ TagThingWanted)]
+
+gen_taggery_Names dfuns
+ = foldlTc do_con2tag [] tycons_of_interest `thenTc` \ names_so_far ->
foldlTc 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 simplDFunClassTyCon dfuns
+ all_tycons = map snd all_CTs
(tycons_of_interest, _) = removeDups compare all_tycons
do_con2tag acc_Names tycon
| isDataTyCon tycon &&
- (we_are_deriving eqClassKey tycon
+ ((we_are_deriving eqClassKey tycon
&& any isNullaryDataCon (tyConDataCons tycon))
|| (we_are_deriving ordClassKey tycon
&& not (maybeToBool (maybeTyConSingleCon tycon)))
|| (we_are_deriving enumClassKey tycon)
- || (we_are_deriving ixClassKey tycon)
+ || (we_are_deriving ixClassKey tycon))
= returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag)
: acc_Names)
= returnTc acc_Names
do_tag2con acc_Names tycon
- = if (we_are_deriving enumClassKey tycon)
- || (we_are_deriving ixClassKey tycon)
- then
- returnTc ( (tag2con_RDR tycon, tycon, GenTag2Con)
- : (maxtag_RDR tycon, tycon, GenMaxTag)
- : acc_Names)
- else
- returnTc acc_Names
+ | isDataTyCon tycon &&
+ (we_are_deriving enumClassKey tycon ||
+ we_are_deriving ixClassKey tycon
+ && isEnumerationTyCon tycon)
+ = returnTc ( (tag2con_RDR tycon, tycon, GenTag2Con)
+ : (maxtag_RDR tycon, tycon, GenMaxTag)
+ : acc_Names)
+ | otherwise
+ = returnTc acc_Names
we_are_deriving clas_key tycon
= is_in_eqns clas_key tycon all_CTs
\end{code}
\begin{code}
-derivingThingErr :: FAST_STRING -> FAST_STRING -> TyCon -> ErrMsg
+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 thing why tycon
- = hang (hsep [ptext SLIT("Can't make a derived instance of"), ptext thing])
- 0 (hang (hsep [ptext SLIT("for the type"), quotes (ppr tycon)])
- 0 (parens (ptext why)))
+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)")]
derivCtxt tycon
= ptext SLIT("When deriving classes for") <+> quotes (ppr tycon)