%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1994
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcDeriv]{Deriving}
Handles @deriving@ clauses on @data@ declarations.
-********** Don't forget
-
-Multi-instance checking in renamer should include deriving.
-
\begin{code}
+module TcDeriv ( tcDeriving ) where
+
#include "HsVersions.h"
-module TcDeriv (
- tcDeriving,
- con2tag_PN, tag2con_PN, maxtag_PN,
- TagThingWanted(..), DerivEqn(..)
- ) where
+import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..),
+ collectLocatedMonoBinders )
+import RdrHsSyn ( RdrNameMonoBinds )
+import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPred )
+import CmdLineOpts ( DynFlag(..), DynFlags )
-IMPORT_Trace -- ToDo:rm debugging
-import Outputable
-import Pretty
-
-import TcMonad -- typechecking monad machinery
-import TcMonadFns ( copyTyVars )
-import AbsSyn -- the stuff being typechecked
-import TcGenDeriv -- support code that generates all the grimy bindings
- -- for derived instance decls.
-
-import AbsPrel ( mkFunTy )
-import AbsUniType
-import UniType ( UniType(..) ) -- *********** CHEATING!!! ****************
-import Bag
-import CE ( CE(..) )
-import CmdLineOpts ( GlobalSwitch(..) )
-import E ( E )
-import Errors
-import HsCore -- ****** NEED TO SEE CONSTRUCTORS ******
-import HsPragmas -- InstancePragmas(..)
-import Id ( getDataConSig, isNullaryDataCon, DataCon(..) )
-import IdInfo
-import Inst ( InstOrigin(..) )
-import InstEnv
-import Maybes ( assocMaybe, maybeToBool, Maybe(..) )
-import NameTypes ( mkFullName, mkPreludeCoreName,
- Provenance(..), FullName, ShortName
+import TcMonad
+import TcEnv ( tcSetInstEnv, newDFunName, InstInfo(..), pprInstInfo,
+ tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv
)
-import ProtoName ( eqProtoName, ProtoName(..), Name )
-import RenameAuxFuns -- why not? take all of it...
-import RenameBinds4 ( rnMethodBinds4, rnTopBinds4 )
-import RenameMonad4 -- initRn4, etc.
-import SrcLoc ( mkGeneratedSrcLoc, mkUnknownSrcLoc, SrcLoc )
-import TCE -- ( rngTCE, TCE(..), UniqFM )
-import TcInstDcls ( InstInfo(..), buildInstanceEnvs, mkInstanceRelatedIds )
+import TcGenDeriv -- Deriv stuff
+import InstEnv ( InstEnv, simpleDFunClassTyCon, extendInstEnv )
+import TcMonoType ( tcHsPred )
import TcSimplify ( tcSimplifyThetas )
-import Unique -- *Key stuff
-import Util
+
+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 MkId ( mkDictFunId )
+import DataCon ( dataConRepArgTys, isNullaryDataCon, isExistentialDataCon )
+import PrelInfo ( needsDataDeclCtxtClassKeys )
+import Maybes ( maybeToBool, catMaybes )
+import Module ( Module )
+import Name ( Name, getSrcLoc, nameUnique )
+import RdrName ( RdrName )
+
+import TyCon ( tyConTyVars, tyConDataCons, tyConArity, newTyConRep,
+ tyConTheta, maybeTyConSingleCon, isDataTyCon,
+ isEnumerationTyCon, TyCon
+ )
+import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe,
+ isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys,
+ tcSplitTyConApp_maybe, tcEqTypes )
+import Var ( TyVar, tyVarKind )
+import VarSet ( mkVarSet, subVarSet )
+import PrelNames
+import Util ( zipWithEqual, sortLt )
+import ListSetOps ( removeDups, assoc )
+import Outputable
+import Maybe ( isJust )
+import List ( nub )
+import FastString ( FastString )
\end{code}
%************************************************************************
Consider
- data T a b = C1 (Foo a) (Bar b)
- | C2 Int (T b a)
+ data T a b = C1 (Foo a) (Bar b)
+ | C2 Int (T b a)
| C3 (T a a)
deriving (Eq)
+[NOTE: See end of these comments for what to do with
+ data (C a, D b) => T a b = ...
+]
+
We want to come up with an instance declaration of the form
instance (Ping a, Pong b, ...) => Eq (T a b) where
u Eq (T a a) -- From C3
After simplification:
- = Eq a u Ping b
+ = Eq a u Ping b
u (Eq b u Ping a)
u (Eq a u Ping a)
-
+
= Eq a u Ping b u Eq b u Ping a
The next iteration gives the same result, so this is the fixpoint. We
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 DerivRhs = [(Class, TauType)] -- Same as a ThetaType!
+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 = ThetaType
type DerivSoln = DerivRhs
\end{code}
+
+A note about contexts on data decls
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+
+ data (RealFloat a) => Complex a = !a :+ !a deriving( Read )
+
+We will need an instance decl like:
+
+ instance (Read a, RealFloat a) => Read (Complex a) where
+ ...
+
+The RealFloat in the context is because the read method for Complex is bound
+to construct a Complex, and doing that requires that the argument type is
+in RealFloat.
+
+But this ain't true for Show, Eq, Ord, etc, since they don't construct
+a Complex; they only take them apart.
+
+Our approach: identify the offending classes, and add the data type
+context to the instance decl. The "offending classes" are
+
+ Read, Enum?
+
+
%************************************************************************
%* *
\subsection[TcDeriv-driver]{Top-level function for \tr{derivings}}
%************************************************************************
\begin{code}
-tcDeriving :: FAST_STRING -- name of module under scrutiny
- -> GlobalNameFuns -- for "renaming" bits of generated code
- -> Bag InstInfo -- What we already know about instances
- -> TCE -- All known TyCon info
- -> [RenamedFixityDecl] -- Fixity info; may be used for Text
- -> TcM (Bag InstInfo, -- The generated "instance decls".
- RenamedBinds, -- Extra generated bindings
- PprStyle -> Pretty) -- Printable derived instance decls;
- -- for debugging via -ddump-derivings.
-
-tcDeriving modname renamer_name_funs inst_decl_infos_in tce fixities
- = -- Fish the "deriving"-related information out of the TCE,
- -- from which we make the necessary "equations".
- makeDerivEqns tce `thenTc` \ eqns ->
-
- -- Take the equation list and solve it, to deliver a list of
+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
+ -> TcM ([InstInfo], -- The generated "instance decls".
+ RenamedHsBinds) -- Extra generated bindings
+
+tcDeriving prs mod inst_env get_fixity tycl_decls
+ = recoverTc (returnTc ([], EmptyBinds)) $
+ getDOptsTc `thenNF_Tc` \ 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
+ -- 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) ->
+ 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_`
+
+ returnTc (inst_info, binds)
+
+ where
+ ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc
+ ddump_deriving inst_infos extra_binds
+ = vcat (map pprInstInfo inst_infos) $$ ppr extra_binds
+
+
+-----------------------------------------
+deriveOrdinaryStuff mod prs inst_env_in get_fixity [] -- Short cut
+ = returnTc ([], EmptyBinds)
+
+deriveOrdinaryStuff mod prs inst_env_in get_fixity 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 modname 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
-- 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 eqns `thenTc` \ nm_alist_etc ->
+ tcGetEnv `thenNF_Tc` \ env ->
+ getDOptsTc `thenNF_Tc` \ dflags ->
let
- nm_alist = [ (pn, n) | (pn,n,_,_) <- nm_alist_etc ]
-
- -- We have the renamer's final "name funs" in our hands
- -- (they were passed in). So we can handle ProtoNames
- -- that refer to anything "out there". But our generated
- -- code may also mention "con2tag" (etc.). So we need
- -- to augment to "name funs" to include those.
- (rn_val_gnf, rn_tc_gnf) = renamer_name_funs
-
- deriv_val_gnf pname = case (assoc_maybe nm_alist pname) of
- Just xx -> Just xx
- Nothing -> rn_val_gnf pname
-
- deriver_name_funs = (deriv_val_gnf, rn_tc_gnf)
-
- assoc_maybe [] _ = Nothing
- assoc_maybe ((v,xxx) : vs) key
- = if v `eqProtoName` key then Just xxx else assoc_maybe vs key
+ 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
+
+ -- 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
- gen_tag_n_con_binds deriver_name_funs nm_alist_etc `thenTc` \ extra_binds ->
+ returnTc (new_inst_infos, rn_extra_binds)
- mapTc (gen_inst_info modname fixities deriver_name_funs) new_inst_infos
- `thenTc` \ really_new_inst_infos ->
-
- returnTc (listToBag really_new_inst_infos,
- extra_binds,
- ddump_deriving really_new_inst_infos extra_binds)
where
- ddump_deriving :: [InstInfo] -> RenamedBinds -> (PprStyle -> Pretty)
+ -- 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 = [] }
- ddump_deriving inst_infos extra_binds sty
- = ppAboves ((map (pp_1 sty) inst_infos) ++ [ppr sty extra_binds])
- where
- pp_1 sty (InstInfo clas tv_tmpls ty inst_decl_theta _ _ _ mbinds _ _ _ _)
- = ppAbove (ppr sty (mkSigmaTy tv_tmpls inst_decl_theta
- (UniDict clas ty)))
- (ppr sty mbinds)
+ rn_meths (cls, meths) = rnMethodBinds cls [] meths `thenRn` \ (meths', _) ->
+ returnRn meths' -- Ignore the free vars returned
\end{code}
all those.
\begin{code}
-makeDerivEqns :: TCE -> TcM [DerivEqn]
-
-makeDerivEqns tce
- = let
- think_about_deriving = need_deriving (rngTCE tce)
- in
- mapTc (chk_out think_about_deriving) think_about_deriving `thenTc_`
-
- let
- (derive_these, _) = removeDups cmp think_about_deriving
- in
-
- listNF_Tc (map mk_eqn derive_these) `thenNF_Tc` \ eqns ->
+makeDerivEqns :: [RenamedTyClDecl]
+ -> TcM ([DerivEqn], -- Ordinary derivings
+ [InstInfo]) -- Special newtype derivings
- returnTc eqns
+makeDerivEqns tycl_decls
+ = mapAndUnzipTc mk_eqn derive_these `thenTc` \ (maybe_ordinaries, maybe_newtypes) ->
+ returnTc (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 ->
- case (getTyConDerivings tycon) of
- [] -> acc
- cs -> [ (clas,tycon) | clas <- cs ] ++ acc
- )
- [] -- init accumulator
- 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 ]
------------------------------------------------------------------
- chk_out :: [(Class, TyCon)] -> (Class, TyCon) -> TcM ()
-
- chk_out whole_deriving_list this_one@(clas, tycon)
- = -- Are the relevant superclasses catered for?
- -- E.g., for "... deriving Ord", is there an
- -- instance of "Eq"?
- let
- (_, super_classes, _) = getClassSig clas
- clas_key = getClassKey clas
- in
-
- -- Are things OK for deriving Enum (if appropriate)?
- checkTc (clas_key == enumClassKey && not (isEnumerationTyCon tycon))
- (derivingEnumErr tycon) `thenTc_`
-
- -- Are things OK for deriving Ix (if appropriate)?
- checkTc (clas_key == ixClassKey
- && not (isEnumerationTyCon tycon
- || maybeToBool (maybeSingleConstructorTyCon tycon)))
- (derivingIxErr tycon)
-
- ------------------------------------------------------------------
- cmp :: (Class, TyCon) -> (Class, TyCon) -> TAG_
-
- cmp (c1, t1) (c2, t2)
- = case cmpClass c1 c2 of
- EQ_ -> cmpTyCon t1 t2
- other -> other
-
- ------------------------------------------------------------------
- mk_eqn :: (Class, TyCon) -> NF_TcM DerivEqn
- -- we swizzle the tyvars, data cons, etc., out of the tycon,
+ mk_eqn :: (NewOrData, Name, RenamedHsPred) -> NF_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)
- = let
- tyvar_tmpls = getTyConTyVarTemplates tycon
- data_cons = getTyConDataCons tycon
- in
- copyTyVars tyvar_tmpls `thenNF_Tc` \ (_, tyvars, tyvar_tys) ->
+ mk_eqn (new_or_data, tycon_name, pred)
+ = tcLookupTyCon tycon_name `thenNF_Tc` \ tycon ->
+ tcAddSrcLoc (getSrcLoc tycon) $
+ tcAddErrCtxt (derivCtxt tycon) $
+ tcExtendTyVarEnv (tyConTyVars tycon) $ -- Deriving preds may (now) mention
+ -- the type variables for the type constructor
+ tcHsPred pred `thenTc` \ pred' ->
+ case getClassPredTys_maybe pred' of
+ Nothing -> bale_out (malformedPredErr tycon pred)
+ Just (clas, tys) -> mk_eqn_help new_or_data tycon clas tys
- let
- constraints = concat [mk_constraints tyvar_tys con | con <- data_cons]
- in
- returnNF_Tc (clas, tycon, tyvars, constraints)
+ ------------------------------------------------------------------
+ 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 `thenNF_Tc` \ dfun_name ->
+ returnNF_Tc (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
where
- mk_constraints tyvar_tys data_con
- = [ (clas, instantiateTy inst_env arg_ty)
- | arg_ty <- arg_tys,
- not (isPrimType arg_ty) -- No constraints for primitive types
- ]
- where
- (con_tyvar_tmpls, _, arg_tys, _) = getDataConSig data_con
- inst_env = con_tyvar_tmpls `zipEqual` tyvar_tys
- -- Type vars in data contructor should be same in number
- -- as in the type contsructor!
+ -- 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
+ --
+ -- We generate the instances
+ -- instance Ci (t ak...aj) => Ci (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 )
+
+ kind = tyVarKind (last (classTyVars clas))
+ -- 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)
+
+ (tyvars, rep_ty) = newTyConRep tycon
+ maybe_rep_app = tcSplitTyConApp_maybe rep_ty
+ Just (rep_tc, rep_ty_args) = maybe_rep_app
+
+ 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
+ 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
+
+ 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;
+ -- 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:
+ -- eg not: newtype T a = T Int deriving( Monad )
+ && eta_ok -- Eta reduction works
+
+ -- 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
+ SLIT("too hard for cunning newtype deriving")
+
+
+ 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
\end{code}
%************************************************************************
%* *
%************************************************************************
-A ``solution'' (to one of the equations) is a list of (k,UniTyVar tv)
+A ``solution'' (to one of the equations) is a list of (k,TyVarTy tv)
terms, which is the final correct RHS for the corresponding original
equation.
\begin{itemize}
\item
-Each (k,UniTyVarTemplate tv) in a solution constrains only a type
+Each (k,TyVarTy tv) in a solution constrains only a type
variable, tv.
\item
-The (k,UniTyVarTemplate tv) pairs in a solution are canonically
+The (k,TyVarTy tv) pairs in a solution are canonically
ordered by sorting on type varible, tv, (major key) and then class, k,
(minor key)
\end{itemize}
\begin{code}
-solveDerivEqns :: FAST_STRING
- -> Bag InstInfo
- -> [DerivEqn]
- -> TcM [InstInfo] -- Solns in same order as eqns.
- -- This bunch is Absolutely minimal...
+solveDerivEqns :: InstEnv
+ -> [DerivEqn]
+ -> TcM [DFunId] -- Solns in same order as eqns.
+ -- This bunch is Absolutely minimal...
-solveDerivEqns modname 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
initial_solutions :: [DerivSoln]
initial_solutions = [ [] | _ <- orig_eqns ]
+ ------------------------------------------------------------------
-- iterateDeriv calculates the next batch of solutions,
-- compares it with the current one; finishes if they are the
-- same, otherwise recurses with the new solutions.
-
- iterateDeriv :: [DerivSoln] ->TcM [InstInfo]
-
+ -- It fails if any iteration fails
+ iterateDeriv :: [DerivSoln] ->TcM [DFunId]
iterateDeriv current_solns
- = -- Extend the inst info from the explicit instance decls
- -- with the current set of solutions, giving a
+ = checkNoErrsTc (iterateOnce current_solns)
+ `thenTc` \ (new_dfuns, new_solns) ->
+ if (current_solns == new_solns) then
+ returnTc new_dfuns
+ else
+ iterateDeriv new_solns
- add_solns modname inst_decl_infos_in orig_eqns current_solns
- `thenTc` \ (new_inst_infos, inst_mapper) ->
-
- -- Simplify each RHS, using a DerivingOrigin containing an
- -- inst_mapper reflecting the previous solution
- let
- mk_deriv_origin clas ty
- = DerivingOrigin inst_mapper clas is_fun_type tycon locn
- where
- is_fun_type = isFunType ty
- (tycon,_,_) = getUniDataTyCon ty
- locn = if is_fun_type then mkUnknownSrcLoc{-sigh-} else getSrcLoc tycon
- in
- listTc [ tcSimplifyThetas mk_deriv_origin rhs
- | (_, _, _, rhs) <- orig_eqns
- ] `thenTc` \ next_solns ->
+ ------------------------------------------------------------------
+ iterateOnce current_solns
+ = -- Extend the inst info from the explicit instance decls
+ -- with the current set of solutions, giving a
+ getDOptsTc `thenNF_Tc` \ dflags ->
+ let
+ new_dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns
+ inst_env = extend_inst_env dflags inst_env_in new_dfuns
+ -- the eqns and solns move "in lockstep"; we have the eqns
+ -- because we need the LHS info for addClassInstance.
+ in
+ -- Simplify each RHS
+ tcSetInstEnv inst_env (
+ listTc [ tcAddSrcLoc (getSrcLoc tc) $
+ 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 less_than next_soln | next_soln <- next_solns ] in
-
- if current_solns == canonicalised_next_solns then
- returnTc new_inst_infos
- else
- iterateDeriv canonicalised_next_solns
-
- where
- ------------------------------------------------------------------
- less_than :: (Class, TauType) -> (Class, TauType) -> Bool
-
- less_than (clas1, UniTyVar tv1) (clas2, UniTyVar tv2)
- = tv1 < tv2 || (tv1 == tv2 && clas1 < clas2)
-#ifdef DEBUG
- less_than other_1 other_2
- = pprPanic "tcDeriv:less_than:" (ppCat [ppr PprDebug other_1, ppr PprDebug other_2])
-#endif
+ let canonicalised_next_solns = [ sortLt (<) next_soln | next_soln <- next_solns ]
+ in
+ returnTc (new_dfuns, canonicalised_next_solns)
\end{code}
\begin{code}
-add_solns :: FAST_STRING
- -> Bag InstInfo -- The global, non-derived ones
- -> [DerivEqn] -> [DerivSoln]
- -> TcM ([InstInfo], -- The new, derived ones
- InstanceMapper)
- -- the eqns and solns move "in lockstep"; we have the eqns
- -- because we need the LHS info for addClassInstance.
-
-add_solns modname inst_infos_in eqns solns
- = listTc (zipWith mk_deriv_inst_info eqns solns) `thenTc` \ new_inst_infos ->
-
- buildInstanceEnvs (inst_infos_in `unionBags`
- listToBag new_inst_infos) `thenTc` \ inst_mapper ->
-
- returnTc (new_inst_infos, inst_mapper)
+extend_inst_env dflags inst_env new_dfuns
+ = new_inst_env
where
- mk_deriv_inst_info (clas, tycon, tyvars, _) theta
- -- The complication here is rather boring: InstInfos need TyVarTemplates,
- -- and we have only TyVars in our hand.
- = let
- tyvar_tmpls = mkTemplateTyVars tyvars
- tv_tmpl_tys = map mkTyVarTemplateTy tyvar_tmpls
-
- env = tyvars `zipEqual` tv_tmpl_tys
-
- tycon_tmpl_ty = applyTyCon tycon tv_tmpl_tys
- theta_tmpl = [(clas, mapOverTyVars to_tmpl ty) | (clas,ty) <- theta]
-
- to_tmpl = assoc "mk_deriv_inst_info" env
-
- (class_tyvar, super_classes, _, class_ops, _, _) = getClassBigSig clas
- in
- returnTc (
- InstInfo clas tyvar_tmpls tycon_tmpl_ty
- theta_tmpl
- theta_tmpl -- Blarg. This is the dfun_theta slot,
- -- which is needed by buildInstanceEnv;
- -- This works ok for solving the eqns, and
- -- gen_eqns sets it to its final value
- -- (incl super class dicts) before we
- -- finally return it.
-#ifndef DEBUG
- (panic "add_soln:dfun_id") (panic "add_soln:const_meth_ids")
- (panic "add_soln:binds") (panic "add_soln:from_here")
- (panic "add_soln:modname") mkGeneratedSrcLoc
- (panic "add_soln:upragmas")
- )
-#else
- bottom bottom bottom bottom bottom mkGeneratedSrcLoc bottom
- )
- where
- bottom = panic "add_soln"
-#endif
+ (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
\end{code}
%************************************************************************
``you-couldn't-do-better-by-hand'' efficient.
\item
-Deriving @Text@---also pretty common, usually just for
-@show@---should also be reasonable good code.
+Deriving @Show@---also pretty common--- should also be reasonable good code.
\item
Deriving for the other classes isn't that common or that big a deal.
\begin{itemize}
\item
-Deriving @Ord@ is done mostly with our non-standard @tagCmp@ method.
+Deriving @Ord@ is done mostly with the 1.3 @compare@ method.
\item
-Deriving @Eq@ also uses @tagCmp@, if we're deriving @Ord@, too.
+Deriving @Eq@ also uses @compare@, if we're deriving @Ord@, too.
\item
-We {\em normally} generated code only for the non-defaulted methods;
+We {\em normally} generate code only for the non-defaulted methods;
there are some exceptions for @Eq@ and (especially) @Ord@...
\item
@gen_tag_n_con_binds@, and the heuristic for deciding if one of
these is around is given by @hasCon2TagFun@.
-
The examples under the different sections below will make this
clearer.
@_tag2con_<tycon>@ function. See the examples.
\item
-We use Pass~4 of the renamer!!! Reason: we're supposed to be
+We use the renamer!!! Reason: we're supposed to be
producing @RenamedMonoBinds@ for the methods, but that means
producing correctly-uniquified code on the fly. This is entirely
possible (the @TcM@ monad has a @UniqueSupply@), but it is painful.
-So, instead, we produce @ProtoNameMonoBinds@ then heave 'em through
+So, instead, we produce @RdrNameMonoBinds@ then heave 'em through
the renamer. What a great hack!
\end{itemize}
\begin{code}
-gen_inst_info :: FAST_STRING -- Module name
- -> [RenamedFixityDecl] -- all known fixities;
- -- may be needed for Text
- -> GlobalNameFuns -- lookup stuff for names we may use
- -> InstInfo -- the main stuff to work on
- -> TcM InstInfo -- the gen'd (filled-in) "instance decl"
-
-gen_inst_info modname fixities deriver_name_funs
- info@(InstInfo clas tyvar_tmpls ty inst_decl_theta _ _ _ _ _ _ locn _)
- =
- -- Generate the various instance-related Ids
- mkInstanceRelatedIds
- (panic "add_solns:E")
- -- These two are only needed if there are pragmas to typecheck;
- -- but there ain't since we are generating the code right here.
- True {-yes, from_here-}
- NoInstancePragmas
- mkGeneratedSrcLoc
- clas
- tyvar_tmpls ty
- inst_decl_theta
- [{-no user pragmas-}]
- `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) ->
-
- -- Generate the bindings for the new instance declaration,
- -- rename it, and check for errors
- getSwitchCheckerTc `thenNF_Tc` \ sw_chkr ->
- let
- (tycon,_,_) = getUniDataTyCon ty
-
- omit_readsPrec = sw_chkr OmitDerivedRead
-
- proto_mbinds
- = if clas_key == textClassKey then gen_Text_binds fixities omit_readsPrec tycon
- else if clas_key == eqClassKey then gen_Eq_binds tycon
- else if clas_key == ordClassKey then gen_Ord_binds tycon
- else if clas_key == enumClassKey then gen_Enum_binds tycon
- else if clas_key == ixClassKey then gen_Ix_binds tycon
- else if clas_key == binaryClassKey then gen_Binary_binds tycon
- else panic "gen_inst_info:bad derived class"
- in
- rn4MtoTcM deriver_name_funs (
- rnMethodBinds4 clas_Name proto_mbinds
- ) `thenNF_Tc` \ (mbinds, errs) ->
-
- if not (isEmptyBag errs) then
- pprPanic "gen_inst_info:renamer errs!\n" (ppAbove (pprBagOfErrors PprDebug errs) (ppr PprDebug proto_mbinds))
- else
--- pprTrace "derived binds:" (ppr PprDebug proto_mbinds) $
-
- -- All done
- let
- from_here = isLocallyDefined tycon -- If so, then from here
- in
- returnTc (InstInfo clas tyvar_tmpls ty
- inst_decl_theta dfun_theta dfun_id const_meth_ids
- -- and here comes the main point...
- (if from_here then mbinds else EmptyMonoBinds)
- from_here modname locn [])
+-- Generate the method bindings for the required instance
+-- (paired with class name, 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
- clas_key = getClassKey clas
- clas_Name
- = let (mod, nm) = getOrigName clas in
- PreludeClass clas_key (mkPreludeCoreName mod nm)
+ 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)
+ ]
\end{code}
+
%************************************************************************
%* *
-\subsection[TcGenDeriv-con2tag-tag2con]{Generating extra binds (@con2tag@ and @tag2con@)}
+\subsection[TcDeriv-taggery-Names]{What con2tag/tag2con functions are available?}
%* *
%************************************************************************
+
data Foo ... = ...
con2tag_Foo :: Foo ... -> Int#
tag2con_Foo :: Int -> Foo ... -- easier if Int, not Int#
-maxtag_Foo :: Int -- ditto (NB: not unboxed)
-
-\begin{code}
-gen_tag_n_con_binds :: GlobalNameFuns
- -> [(ProtoName, Name, TyCon, TagThingWanted)]
- -> TcM RenamedBinds
-
-gen_tag_n_con_binds deriver_name_funs nm_alist_etc
- = let
- proto_mbind_list = map gen_tag_n_con_monobind nm_alist_etc
- proto_mbinds = foldr AndMonoBinds EmptyMonoBinds proto_mbind_list
- in
+maxtag_Foo :: Int -- ditto (NB: not unlifted)
- rn4MtoTcM deriver_name_funs (
- rnTopBinds4 (SingleBind (RecBind proto_mbinds))
- ) `thenNF_Tc` \ (binds, errs) ->
-
- if not (isEmptyBag errs) then
- panic "gen_inst_info:renamer errs (2)!"
- else
- returnTc binds
-\end{code}
-
-%************************************************************************
-%* *
-\subsection[TcDeriv-taggery-Names]{What con2tag/tag2con functions are available?}
-%* *
-%************************************************************************
We have a @con2tag@ function for a tycon if:
\begin{itemize}
If we have a @tag2con@ function, we also generate a @maxtag@ constant.
\begin{code}
-data TagThingWanted
- = GenCon2Tag | GenTag2Con | GenMaxTag
-
-gen_taggery_Names :: [DerivEqn]
- -> TcM [(ProtoName, Name, -- for an assoc list
- TyCon, -- related tycon
+gen_taggery_Names :: [DFunId]
+ -> TcM [(RdrName, -- for an assoc list
+ TyCon, -- related tycon
TagThingWanted)]
-gen_taggery_Names eqns
- = let all_tycons = [ tc | (_, tc, _, _) <- eqns ]
- (tycons_of_interest, _) = removeDups cmpTyCon all_tycons
- in
- foldlTc do_con2tag [] tycons_of_interest `thenTc` \ names_so_far ->
- foldlTc do_tag2con names_so_far tycons_of_interest
+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 = map simpleDFunClassTyCon dfuns
+ all_tycons = map snd all_CTs
+ (tycons_of_interest, _) = removeDups compare all_tycons
+
do_con2tag acc_Names tycon
- = if (we_are_deriving eqClassKey tycon
- && any isNullaryDataCon (getTyConDataCons tycon))
- || (we_are_deriving ordClassKey tycon
- && not (maybeToBool (maybeSingleConstructorTyCon tycon)))
- || (we_are_deriving enumClassKey tycon)
- || (we_are_deriving ixClassKey tycon)
- then
- getUniqueTc `thenNF_Tc` ( \ u ->
- returnTc ((con2tag_PN tycon, OtherTopId u (con2tag_FN tycon), tycon, GenCon2Tag)
- : acc_Names) )
- else
- returnTc acc_Names
+ | isDataTyCon 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))
+
+ = returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag)
+ : acc_Names)
+ | otherwise
+ = returnTc acc_Names
do_tag2con acc_Names tycon
- = if (we_are_deriving enumClassKey tycon)
- || (we_are_deriving ixClassKey tycon)
- then
- getUniqueTc `thenNF_Tc` \ u1 ->
- getUniqueTc `thenNF_Tc` \ u2 ->
- returnTc ( (tag2con_PN tycon, OtherTopId u1 (tag2con_FN tycon), tycon, GenTag2Con)
- : (maxtag_PN tycon, OtherTopId u2 (maxtag_FN 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 eqns
+ = is_in_eqns clas_key tycon all_CTs
where
is_in_eqns clas_key tycon [] = False
- is_in_eqns clas_key tycon ((c,t,_,_):eqns) -- ToDo: InstInfo
- = (clas_key == getClassKey c && tycon == t)
- || is_in_eqns clas_key tycon eqns
-
-con2tag_PN, tag2con_PN, maxtag_PN :: TyCon -> ProtoName
-con2tag_FN, tag2con_FN, maxtag_FN :: TyCon -> FullName
-
-con2tag_PN tycon
- = let (mod, nm) = getOrigName tycon
- con2tag = SLIT("con2tag_") _APPEND_ nm _APPEND_ SLIT("#")
- in
- Imp mod con2tag [mod] con2tag
-
-con2tag_FN tycon
- = let (mod, nm) = getOrigName tycon
- con2tag = SLIT("con2tag_") _APPEND_ nm _APPEND_ SLIT("#")
- in
- mkFullName mod con2tag InventedInThisModule NotExported mkGeneratedSrcLoc
-
-tag2con_PN tycon
- = let (mod, nm) = getOrigName tycon
- tag2con = SLIT("tag2con_") _APPEND_ nm _APPEND_ SLIT("#")
- in
- Imp mod tag2con [mod] tag2con
+ is_in_eqns clas_key tycon ((c,t):cts)
+ = (clas_key == classKey c && tycon == t)
+ || is_in_eqns clas_key tycon cts
+\end{code}
-tag2con_FN tycon
- = let (mod, nm) = getOrigName tycon
- tag2con = SLIT("tag2con_") _APPEND_ nm _APPEND_ SLIT("#")
- in
- mkFullName mod tag2con InventedInThisModule NotExported mkGeneratedSrcLoc
+\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)]
+ where
+ pred = mkClassPred clas (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars)])
-maxtag_PN tycon
- = let (mod, nm) = getOrigName tycon
- maxtag = SLIT("maxtag_") _APPEND_ nm _APPEND_ SLIT("#")
- in
- Imp mod maxtag [mod] maxtag
+malformedPredErr tycon pred = ptext SLIT("Illegal deriving item") <+> ppr pred
-maxtag_FN tycon
- = let (mod, nm) = getOrigName tycon
- maxtag = SLIT("maxtag_") _APPEND_ nm _APPEND_ SLIT("#")
- in
- mkFullName mod maxtag InventedInThisModule NotExported mkGeneratedSrcLoc
+derivCtxt tycon
+ = ptext SLIT("When deriving classes for") <+> quotes (ppr tycon)
\end{code}
+
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