%
-% (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.
\begin{code}
+module TcDeriv ( tcDeriving ) where
+
#include "HsVersions.h"
-module TcDeriv (
- tcDeriving
- ) where
-
-import Ubiq
-
-import HsSyn ( FixityDecl, Sig, HsBinds(..), Bind(..), MonoBinds(..),
- GRHSsAndBinds, Match, HsExpr, HsLit, InPat,
- ArithSeqInfo, Fake, MonoType )
-import HsPragmas ( InstancePragmas(..) )
-import RnHsSyn ( RenamedHsBinds(..), RenamedFixityDecl(..) )
-import TcHsSyn ( TcIdOcc )
-
-import TcMonad
-import Inst ( InstOrigin(..), InstanceMapper(..) )
-import TcEnv ( getEnv_TyCons )
-import TcKind ( TcKind )
---import TcGenDeriv -- Deriv stuff
-import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs )
-import TcSimplify ( tcSimplifyThetas )
-
---import RnMonad4
-import RnUtils ( GlobalNameMappers(..), GlobalNameMapper(..) )
---import RnBinds4 ( rnMethodBinds, rnTopBinds )
-
-import Bag ( emptyBag{-ToDo:rm-}, Bag, isEmptyBag, unionBags, listToBag )
-import Class ( GenClass, getClassKey )
-import CmdLineOpts ( opt_CompilingPrelude )
-import ErrUtils ( pprBagOfErrors, addErrLoc, Error(..) )
-import Id ( dataConSig, dataConArity )
-import Maybes ( assocMaybe, maybeToBool, Maybe(..) )
+import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..),
+ collectMonoBinders )
+import RdrHsSyn ( RdrNameMonoBinds )
+import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl, RenamedHsPred )
+import CmdLineOpts ( DynFlag(..) )
+
+import TcRnMonad
+import TcEnv ( tcExtendTempInstEnv, newDFunName,
+ InstInfo(..), pprInstInfo, InstBindings(..),
+ pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv
+ )
+import TcGenDeriv -- Deriv stuff
+import InstEnv ( simpleDFunClassTyCon )
+import TcMonoType ( tcHsPred )
+import TcSimplify ( tcSimplifyDeriv )
+
+import RnBinds ( rnMethodBinds, rnTopMonoBinds )
+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 DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon )
+import Maybes ( maybeToBool, catMaybes )
+import Name ( Name, getSrcLoc, nameUnique )
+import NameSet
+import RdrName ( RdrName )
+
+import TyCon ( tyConTyVars, tyConDataCons, tyConArity,
+ tyConTheta, maybeTyConSingleCon, isDataTyCon,
+ isEnumerationTyCon, isRecursiveTyCon, TyCon
+ )
+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
-import PprType ( GenType, GenTyVar, GenClass, TyCon )
-import PprStyle
-import Pretty
-import SrcLoc ( mkGeneratedSrcLoc, mkUnknownSrcLoc, SrcLoc )
-import TyCon ( tyConTyVars, tyConDataCons, tyConDerivings,
- maybeTyConSingleCon, isEnumerationTyCon, TyCon )
-import Type ( GenType(..), TauType(..), mkTyVarTys, applyTyCon,
- mkSigmaTy, mkDictTy, isPrimType, instantiateTy,
- getAppTyCon, getAppDataTyCon )
-import TyVar ( GenTyVar )
-import UniqFM ( eltsUFM )
-import Unique -- Keys stuff
-import Util ( zipWithEqual, zipEqual, sortLt, removeDups,
- thenCmp, cmpList, panic, pprPanic, pprPanic# )
\end{code}
%************************************************************************
| 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
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}
+
+[Data decl contexts] 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?
+
+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".
+
+
+
%************************************************************************
%* *
\subsection[TcDeriv-driver]{Top-level function for \tr{derivings}}
%************************************************************************
\begin{code}
-tcDeriving :: Module -- name of module under scrutiny
- -> GlobalNameMappers -- for "renaming" bits of generated code
- -> Bag InstInfo -- What we already know about instances
- -> [RenamedFixityDecl] -- Fixity info; used by Read and Show
- -> TcM s (Bag InstInfo, -- The generated "instance decls".
- RenamedHsBinds, -- Extra generated bindings
- PprStyle -> Pretty) -- Printable derived instance decls;
- -- for debugging via -ddump-derivings.
-
-tcDeriving modname renamer_name_funs inst_decl_infos_in fixities
- = returnTc (trace "tcDeriving:ToDo" (emptyBag, EmptyBinds, \ x -> ppNil))
-{- LATER:
-
-tcDeriving modname renamer_name_funs inst_decl_infos_in fixities
- = -- Fish the "deriving"-related information out of the TcEnv
+tcDeriving :: [RenamedTyClDecl] -- All type constructors
+ -> TcM ([InstInfo], -- The generated "instance decls".
+ RenamedHsBinds, -- Extra generated bindings
+ FreeVars) -- These are free in the generated bindings
+
+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 ->
+ 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
- -- Take the equation list and solve it, to deliver a list of
+ 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
+
+-----------------------------------------
+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_dfuns `thenM` \ nm_alist_etc ->
- gen_taggery_Names eqns `thenTc` \ nm_alist_etc ->
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 ((k,v) : vs) key
- = if k `eqProtoName` key then Just v 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
+ mbinders = collectMonoBinders extra_mbinds
in
- gen_tag_n_con_binds deriver_name_funs nm_alist_etc `thenTc` \ extra_binds ->
-
- mapTc (gen_inst_info maybe_mod fixities deriver_name_funs) new_inst_infos
- `thenTc` \ really_new_inst_infos ->
+ 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.
+ 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
+ returnM (new_inst_infos, rn_extra_binds, fvs)
- returnTc (listToBag really_new_inst_infos,
- extra_binds,
- ddump_deriving really_new_inst_infos extra_binds)
where
- maybe_mod = if opt_CompilingPrelude then Nothing else Just mod_name
-
- ddump_deriving :: [InstInfo] -> RenamedHsBinds -> (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 = VanillaInst binds [] }
- ddump_deriving inst_infos extra_binds sty
- = ppAboves ((map pp_info inst_infos) ++ [ppr sty extra_binds])
- where
- pp_info (InstInfo clas tvs ty inst_decl_theta _ _ _ mbinds _ _ _ _)
- = ppAbove (ppr sty (mkSigmaTy tvs inst_decl_theta (mkDictTy clas ty)))
- (ppr sty mbinds)
+ rn_meths (cls, meths) = rnMethodBinds cls [] meths
\end{code}
all those.
\begin{code}
-makeDerivEqns :: TcM s [DerivEqn]
+makeDerivEqns :: [RenamedTyClDecl]
+ -> TcM ([DerivEqn], -- Ordinary derivings
+ [InstInfo]) -- Special newtype derivings
-makeDerivEqns
- = tcGetEnv `thenNF_Tc` \ env ->
- let
- tycons = getEnv_TyCons env
- think_about_deriving = need_deriving tycons
- in
- mapTc (chk_out think_about_deriving) think_about_deriving `thenTc_`
- let
- (derive_these, _) = removeDups cmp_deriv think_about_deriving
- eqns = map mk_eqn derive_these
- in
- returnTc 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 ->
- case (tyConDerivings tycon) of
- [] -> acc
- cs -> [ (clas,tycon) | clas <- cs ] ++ 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 ]
------------------------------------------------------------------
- chk_out :: [(Class, TyCon)] -> (Class, TyCon) -> TcM s ()
- chk_out whole_deriving_list this_one@(clas, tycon)
- = let
- 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 (maybeTyConSingleCon tycon)))
- (derivingIxErr 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
- ------------------------------------------------------------------
- cmp_deriv :: (Class, TyCon) -> (Class, TyCon) -> TAG_
- cmp_deriv (c1, t1) (c2, t2)
- = (c1 `cmp` c2) `thenCmp` (t1 `cmp` t2)
+ 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 :: (Class, TyCon) -> 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, 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 `thenM` \ dfun_name ->
+ returnM (Just (dfun_name, clas, tycon, tyvars, constraints), Nothing)
where
- tyvars = tyConTyVars tycon -- ToDo: Do we need new tyvars ???
- tyvar_tys = mkTyVarTys tyvars
+ tyvars = tyConTyVars tycon
data_cons = tyConDataCons tycon
- constraints = concat (map mk_constraints data_cons)
-
- mk_constraints data_con
- = [ (clas, instantiateTy inst_env arg_ty)
- | arg_ty <- arg_tys,
- not (isPrimType arg_ty) -- No constraints for primitive types
- ]
- where
- (con_tyvars, _, arg_tys, _) = dataConSig data_con
- inst_env = con_tyvars `zipEqual` tyvar_tys
- -- same number of tyvars in data constr and type constr!
+ 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 -> [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 = 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")
+
+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}
%************************************************************************
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 :: 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
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 s [InstInfo]
-
- iterateDeriv 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
- `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 tycon
- where
- (tycon,_) = getAppTyCon ty
- in
- listTc [ tcSimplifyThetas mk_deriv_origin rhs
- | (_, _, _, rhs) <- orig_eqns
- ] `thenTc` \ next_solns ->
-
- -- Canonicalise the solutions, so they compare nicely
- let canonicalised_next_solns
- = [ sortLt lt_rhs next_soln | next_soln <- next_solns ] in
-
- if current_solns `eq_solns` canonicalised_next_solns then
- returnTc new_inst_infos
+ -- It fails if any iteration fails
+ 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
+ returnM dfuns
else
- iterateDeriv canonicalised_next_solns
+ iterateDeriv (n+1) new_solns
- where
- ------------------------------------------------------------------
- lt_rhs r1 r2 = case cmp_rhs r1 r2 of { LT_ -> True; _ -> False }
- eq_solns s1 s2 = case cmp_solns s1 s2 of { EQ_ -> True; _ -> False }
- cmp_solns s1 s2 = cmpList (cmpList cmp_rhs) s1 s2
- cmp_rhs (c1, TyVarTy tv1) (c2, TyVarTy tv2)
- = (tv1 `cmp` tv2) `thenCmp` (c1 `cmp` c2)
-#ifdef DEBUG
- cmp_rhs other_1 other_2
- = pprPanic# "tcDeriv:cmp_rhs:" (ppCat [ppr PprDebug other_1, ppr PprDebug other_2])
-#endif
+ ------------------------------------------------------------------
-\end{code}
+ 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
-\begin{code}
-add_solns :: FAST_STRING
- -> Bag InstInfo -- The global, non-derived ones
- -> [DerivEqn] -> [DerivSoln]
- -> TcM s ([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 inst_infos_in eqns solns
- = buildInstanceEnvs all_inst_infos `thenTc` \ inst_mapper ->
- returnTc (new_inst_infos, inst_mapper)
- where
- new_inst_infos = zipWithEqual 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 (applyTyCon tycon (mkTyVarTys tyvars))
- theta
- theta -- 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.
-#ifdef 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
+mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta
+ = mkDictFunId dfun_name tyvars theta
+ clas [mkTyConApp tycon (mkTyVarTys tyvars)]
\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 :: Maybe Module -- Module name; Nothing => Prelude
- -> [RenamedFixityDecl] -- all known fixities;
- -- may be needed for Text
- -> GlobalNameMappers -- lookup stuff for names we may use
- -> InstInfo -- the main stuff to work on
- -> TcM s InstInfo -- the gen'd (filled-in) "instance decl"
-
-gen_inst_info modname fixities deriver_name_funs
- info@(InstInfo clas tyvars ty inst_decl_theta _ _ _ _ _ _ locn _)
- =
- -- Generate the various instance-related Ids
- mkInstanceRelatedIds
- True {-from_here-} modname
- NoInstancePragmas
- clas tyvars 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
- let
- (tycon,_,_) = getAppDataTyCon ty
-
- proto_mbinds
- | clas_key == eqClassKey = gen_Eq_binds tycon
- | clas_key == showClassKey = gen_Show_binds fixities tycon
- | clas_key == ordClassKey = gen_Ord_binds tycon
- | clas_key == enumClassKey = gen_Enum_binds tycon
- | clas_key == ixClassKey = gen_Ix_binds tycon
- | clas_key == readClassKey = gen_Read_binds fixities tycon
- | clas_key == binaryClassKey = gen_Binary_binds tycon
- | otherwise = panic "gen_inst_info:bad derived class"
- in
- rn4MtoTcM deriver_name_funs (
- rnMethodBinds 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) $
+-- Generate the method bindings for the required instance
+-- (paired with class name, as we need that when renaming
+-- the method binds)
+gen_bind :: DFunId -> TcM (Name, RdrNameMonoBinds)
+gen_bind dfun
+ = getFixityEnv `thenM` \ fix_env ->
+ returnM (cls_nm, gen_binds_fn fix_env cls_nm tycon)
+ where
+ cls_nm = className clas
+ (clas, tycon) = simpleDFunClassTyCon dfun
- -- All done
- let
- from_here = isLocallyDefined tycon -- If so, then from here
- in
- returnTc (InstInfo clas tyvars ty inst_decl_theta
- dfun_theta dfun_id const_meth_ids
- (if from_here then mbinds else EmptyMonoBinds)
- from_here modname locn [])
+gen_binds_fn fix_env cls_nm
+ = assoc "gen_bind:bad derived class"
+ gen_list (nameUnique cls_nm)
where
- clas_key = getClassKey clas
- clas_Name
- = let (mod, nm) = moduleNamePair clas in
- ClassName clas_key (mkPreludeCoreName mod nm) []
+ 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}
+
%************************************************************************
%* *
-\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)
+maxtag_Foo :: Int -- ditto (NB: not unlifted)
-\begin{code}
-gen_tag_n_con_binds :: GlobalNameMappers
- -> [(RdrName, RnName, TyCon, TagThingWanted)]
- -> TcM s RenamedHsBinds
-
-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
-
- rn4MtoTcM deriver_name_funs (
- rnTopBinds (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}
-gen_taggery_Names :: [DerivEqn]
- -> TcM s [(RdrName, RnName, -- for an assoc list
- TyCon, -- related tycon
- TagThingWanted)]
-
-gen_taggery_Names eqns
- = let
- all_tycons = [ tc | (_, tc, _, _) <- eqns ]
- (tycons_of_interest, _) = removeDups cmp 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 :: [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 = 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 ( (== 0).dataConArity ) (tyConDataCons tycon))
- || (we_are_deriving ordClassKey tycon
+ | 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)
- then
- tcGetUnique `thenNF_Tc` ( \ u ->
- returnTc ((con2tag_PN tycon, ValName u (con2tag_FN tycon), tycon, GenCon2Tag)
- : acc_Names) )
- else
- returnTc acc_Names
+ || (we_are_deriving enumClassKey tycon)
+ || (we_are_deriving ixClassKey tycon))
+
+ = returnM ((con2tag_RDR tycon, tycon, GenCon2Tag)
+ : acc_Names)
+ | otherwise
+ = returnM acc_Names
do_tag2con acc_Names tycon
- = if (we_are_deriving enumClassKey tycon)
- || (we_are_deriving ixClassKey tycon)
- then
- tcGetUnique `thenNF_Tc` \ u1 ->
- tcGetUnique `thenNF_Tc` \ u2 ->
- returnTc ( (tag2con_PN tycon, ValName u1 (tag2con_FN tycon), tycon, GenTag2Con)
- : (maxtag_PN tycon, ValName 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)
+ = returnM ( (tag2con_RDR tycon, tycon, GenTag2Con)
+ : (maxtag_RDR tycon, tycon, GenMaxTag)
+ : acc_Names)
+ | otherwise
+ = returnM 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)
- = (clas_key == getClassKey c && tycon == t)
- || is_in_eqns clas_key tycon eqns
-
+ 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}
-derivingEnumErr :: TyCon -> Error
-derivingEnumErr tycon
- = addErrLoc (getSrcLoc tycon) "Can't derive an instance of `Enum'" ( \ sty ->
- ppBesides [ppStr "type `", ppr sty tycon, ppStr "'"] )
-
-derivingIxErr :: TyCon -> Error
-derivingIxErr tycon
- = addErrLoc (getSrcLoc tycon) "Can't derive an instance of `Ix'" ( \ sty ->
- ppBesides [ppStr "type `", ppr sty tycon, ppStr "'"] )
--}
+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)])
+
+malformedPredErr tycon pred = ptext SLIT("Illegal deriving item") <+> ppr pred
+
+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