%
-% (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
+import CmdLineOpts ( DynFlag(..) )
-import TcMonad
-import Inst ( InstanceMapper )
-import TcEnv ( getEnv_TyCons, tcLookupClassByKey )
-import TcKind ( TcKind )
+import Generics ( mkTyConGenericBinds )
+import TcRnMonad
+import TcEnv ( newDFunName,
+ InstInfo(..), InstBindings(..),
+ pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv
+ )
import TcGenDeriv -- Deriv stuff
-import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs )
-import TcSimplify ( tcSimplifyThetas )
-
-import RnBinds ( rnMethodBinds, rnTopMonoBinds )
-import RnEnv ( newDfunName, bindLocatedLocalsRn )
-import RnMonad ( RnM, RnDown, SDown, RnNameSupply,
- renameSourceCode, thenRn, mapRn, returnRn )
-
-import Bag ( Bag, emptyBag, unionBags, listToBag )
-import Class ( classKey, Class )
-import ErrUtils ( ErrMsg )
+import InstEnv ( simpleDFunClassTyCon, extendInstEnv )
+import TcHsType ( tcHsPred )
+import TcSimplify ( tcSimplifyDeriv )
+
+import RnBinds ( rnMethodBinds, rnTopBinds )
+import RnEnv ( bindLocalNames )
+import TcRnMonad ( thenM, returnM, mapAndUnzipM )
+import HscTypes ( DFunId, FixityEnv )
+
+import BasicTypes ( NewOrData(..) )
+import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class )
+import Subst ( mkTyVarSubst, substTheta )
+import ErrUtils ( dumpIfSet_dyn )
import MkId ( mkDictFunId )
-import Id ( dataConArgTys, isNullaryDataCon )
-import PrelInfo ( needsDataDeclCtxtClassKeys )
-import Maybes ( maybeToBool )
-import Name ( isLocallyDefined, getSrcLoc, Provenance,
- Name{--O only-}, Module, NamedThing(..),
- OccName, nameOccName
- )
-import SrcLoc ( mkGeneratedSrcLoc, SrcLoc )
-import TyCon ( tyConTyVars, tyConDataCons, tyConDerivings,
- tyConTheta, maybeTyConSingleCon, isDataTyCon,
- isEnumerationTyCon, isAlgTyCon, TyCon
- )
-import Type ( GenType(..), TauType, mkTyVarTys, mkTyConApp,
- mkSigmaTy, mkDictTy, isUnboxedType,
- splitAlgTyConApp
+import DataCon ( dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon )
+import Maybes ( catMaybes )
+import RdrName ( RdrName )
+import Name ( Name, getSrcLoc )
+import NameSet ( NameSet, emptyNameSet, duDefs )
+import Unique ( Unique, getUnique )
+import Kind ( splitKindFunTys )
+import TyCon ( tyConTyVars, tyConDataCons, tyConArity, tyConHasGenerics,
+ tyConTheta, isProductTyCon, isDataTyCon,
+ isEnumerationTyCon, isRecursiveTyCon, TyCon
)
-import TysPrim ( voidTy )
-import TyVar ( GenTyVar, TyVar )
-import Unique -- Keys stuff
-import Bag ( bagToList )
-import Util ( zipWithEqual, sortLt, removeDups, assoc, thenCmp )
+import TcType ( TcType, ThetaType, mkTyVarTy, mkTyVarTys, mkTyConApp,
+ getClassPredTys_maybe, tcTyConAppTyCon,
+ isUnLiftedType, mkClassPred, tyVarsOfTypes, isArgTypeKind,
+ tcEqTypes, tcSplitAppTys, mkAppTys, tcSplitDFunTy )
+import Var ( TyVar, tyVarKind, idType, varName )
+import VarSet ( mkVarSet, subVarSet )
+import PrelNames
+import SrcLoc ( srcLocSpan, Located(..) )
+import Util ( zipWithEqual, sortLt, notNull )
+import ListSetOps ( removeDups, assoc )
import Outputable
+import Bag
\end{code}
%************************************************************************
So, here are the synonyms for the ``equation'' structures:
\begin{code}
-type DerivEqn = (Class, TyCon, [TyVar], DerivRhs)
- -- The tyvars bind all the variables in the RHS
- -- NEW: it's convenient to re-use InstInfo
- -- We'll "panic" out some fields...
+type DerivEqn = (Name, Class, TyCon, [TyVar], DerivRhs)
+ -- The Name is the name for the DFun we'll build
+ -- The tyvars bind all the variables in the RHS
-type DerivRhs = [(Class, [TauType])] -- Same as a ThetaType!
+pprDerivEqn (n,c,tc,tvs,rhs)
+ = parens (hsep [ppr n, ppr c, ppr tc, ppr tvs] <+> equals <+> ppr rhs)
+type DerivRhs = ThetaType
type DerivSoln = DerivRhs
\end{code}
-A note about contexts on data decls
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+[Data decl contexts] A note about contexts on data decls
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
data (RealFloat a) => Complex a = !a :+ !a deriving( Read )
Read, Enum?
+FURTHER NOTE ADDED March 2002. In fact, Haskell98 now requires that
+pattern matching against a constructor from a data type with a context
+gives rise to the constraints for that context -- or at least the thinned
+version. So now all classes are "offending".
+
+
%************************************************************************
%* *
%************************************************************************
\begin{code}
-tcDeriving :: Module -- name of module under scrutiny
- -> 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 modname rn_name_supply inst_decl_infos_in
- = recoverTc (returnTc (emptyBag, EmptyBinds, empty)) $
-
- -- Fish the "deriving"-related information out of the TcEnv
- -- and make the necessary "equations".
- makeDerivEqns `thenTc` \ eqns ->
- if null eqns then
- returnTc (emptyBag, EmptyBinds, text "No derivings")
- 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 ->
-
- -- Now augment the InstInfos, adding in the rather boring
- -- actual-code-to-do-the-methods binds. We may also need to
- -- generate extra not-one-inst-decl-specific binds, notably
- -- "con2tag" and/or "tag2con" functions. We do these
- -- separately.
-
- gen_taggery_Names new_inst_infos `thenTc` \ nm_alist_etc ->
-
-
- 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)
-
- -- 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 (
- 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)
- )
- 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) $
-
- returnTc (listToBag really_new_inst_infos,
- rn_extra_binds,
- ddump_deriv)
+tcDeriving :: [LTyClDecl Name] -- All type constructors
+ -> TcM ([InstInfo], -- The generated "instance decls"
+ [HsBindGroup Name], -- Extra generated top-level bindings
+ NameSet) -- Binders to keep alive
+
+tcDeriving tycl_decls
+ = recoverM (returnM ([], [], emptyNameSet)) $
+ do { -- Fish the "deriving"-related information out of the TcEnv
+ -- and make the necessary "equations".
+ ; (ordinary_eqns, newtype_inst_info) <- makeDerivEqns tycl_decls
+
+ ; (ordinary_inst_info, deriv_binds)
+ <- extendLocalInstEnv (map iDFunId newtype_inst_info) $
+ deriveOrdinaryStuff ordinary_eqns
+ -- Add the newtype-derived instances to the inst env
+ -- before tacking the "ordinary" ones
+
+ -- Generate the generic to/from functions from each type declaration
+ ; gen_binds <- mkGenericBinds tycl_decls
+ ; let inst_info = newtype_inst_info ++ ordinary_inst_info
+
+ -- Rename these extra bindings, discarding warnings about unused bindings etc
+ -- Set -fglasgow exts so that we can have type signatures in patterns,
+ -- which is used in the generic binds
+ ; (rn_binds, gen_bndrs)
+ <- discardWarnings $ setOptM Opt_GlasgowExts $ do
+ { (rn_deriv, _dus1) <- rnTopBinds deriv_binds []
+ ; (rn_gen, dus_gen) <- rnTopBinds gen_binds []
+ ; return (rn_deriv ++ rn_gen, duDefs dus_gen) }
+
+
+ ; dflags <- getDOpts
+ ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances"
+ (ddump_deriving inst_info rn_binds))
+
+ ; returnM (inst_info, rn_binds, gen_bndrs)
+ }
where
- ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc
-
+ ddump_deriving :: [InstInfo] -> [HsBindGroup Name] -> SDoc
ddump_deriving inst_infos extra_binds
- = vcat ((map pp_info inst_infos) ++ [ppr extra_binds])
- where
- pp_info (InstInfo clas tvs [ty] inst_decl_theta _ _ mbinds _ _)
- = ($$) (ppr (mkSigmaTy tvs inst_decl_theta (mkDictTy clas [ty])))
- (ppr mbinds)
+ = vcat (map pprInstInfoDetails inst_infos) $$ vcat (map ppr extra_binds)
+
+-----------------------------------------
+deriveOrdinaryStuff [] -- Short cut
+ = returnM ([], emptyBag)
+
+deriveOrdinaryStuff eqns
+ = do { -- 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.
+ ; new_dfuns <- solveDerivEqns eqns
+
+ -- Generate the InstInfo for each dfun,
+ -- plus any auxiliary bindings it needs
+ ; (inst_infos, aux_binds_s) <- mapAndUnzipM genInst new_dfuns
+
+ -- Generate any extra not-one-inst-decl-specific binds,
+ -- notably "con2tag" and/or "tag2con" functions.
+ ; extra_binds <- genTaggeryBinds new_dfuns
+
+ -- Done
+ ; returnM (inst_infos, unionManyBags (extra_binds : aux_binds_s))
+ }
+
+-----------------------------------------
+mkGenericBinds tycl_decls
+ = do { tcs <- mapM tcLookupTyCon
+ [ tc_name |
+ L _ (TyData { tcdLName = L _ tc_name }) <- tycl_decls]
+ -- We are only interested in the data type declarations
+ ; return (unionManyBags [ mkTyConGenericBinds tc |
+ tc <- tcs, tyConHasGenerics tc ]) }
+ -- And then only in the ones whose 'has-generics' flag is on
\end{code}
all those.
\begin{code}
-makeDerivEqns :: TcM s [DerivEqn]
+makeDerivEqns :: [LTyClDecl Name]
+ -> TcM ([DerivEqn], -- Ordinary derivings
+ [InstInfo]) -- Special newtype derivings
-makeDerivEqns
- = tcGetEnv `thenNF_Tc` \ env ->
- let
- local_data_tycons = filter (\tc -> isLocallyDefined tc && isAlgTyCon tc)
- (getEnv_TyCons env)
- in
- if null local_data_tycons then
- -- Bale out now; evalClass may not be loaded if there aren't any
- returnTc []
- 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
+makeDerivEqns tycl_decls
+ = mapAndUnzipM mk_eqn derive_these `thenM` \ (maybe_ordinaries, maybe_newtypes) ->
+ returnM (catMaybes maybe_ordinaries, catMaybes maybe_newtypes)
where
------------------------------------------------------------------
- need_deriving :: Class -> [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
- )
- []
- tycons_to_consider
+ derive_these :: [(NewOrData, Name, LHsPred Name)]
+ -- 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)
+ | L _ (TyData { tcdND = nd, tcdLName = L _ tycon,
+ tcdDerivs = Just (L _ preds) }) <- tycl_decls,
+ pred <- preds ]
------------------------------------------------------------------
- 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_`
+ mk_eqn :: (NewOrData, Name, LHsPred Name) -> TcM (Maybe DerivEqn, Maybe InstInfo)
+ -- We swizzle the tyvars and datacons out of the tycon
+ -- to make the rest of the equation
- -- Are things OK for deriving Ix (if appropriate)?
- chk_clas ixClassKey (SLIT("Ix.Ix")) single_nullary_why
- (is_enumeration || is_single_con)
+ mk_eqn (new_or_data, tycon_name, pred)
+ = tcLookupTyCon tycon_name `thenM` \ tycon ->
+ addSrcSpan (srcLocSpan (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) -> doptM Opt_GlasgowExts `thenM` \ gla_exts ->
+ mk_eqn_help gla_exts new_or_data tycon clas tys
------------------------------------------------------------------
- cmp_deriv :: (Class, TyCon) -> (Class, TyCon) -> Ordering
- cmp_deriv (c1, t1) (c2, t2)
- = (c1 `compare` c2) `thenCmp` (t1 `compare` t2)
+ mk_eqn_help gla_exts DataType tycon clas tys
+ | Just err <- checkSideConditions gla_exts clas tycon tys
+ = bale_out (derivingThingErr clas tys tycon tyvars err)
+ | otherwise
+ = new_dfun_name clas tycon `thenM` \ dfun_name ->
+ returnM (Just (dfun_name, clas, tycon, tyvars, constraints), Nothing)
+ where
+ tyvars = tyConTyVars tycon
+ constraints = extra_constraints ++ ordinary_constraints
+ -- "extra_constraints": see note [Data decl contexts] above
+ extra_constraints = tyConTheta tycon
+
+ ordinary_constraints
+ | clas `hasKey` typeableClassKey -- For the Typeable class, the constraints
+ -- don't involve the constructor ags, only
+ -- the tycon tyvars
+ -- e.g. data T a b = ...
+ -- we want
+ -- instance (Typeable a, Typable b)
+ -- => Typeable (T a b) where
+ = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars]
+ | otherwise
+ = [ mkClassPred clas [arg_ty]
+ | data_con <- tyConDataCons tycon,
+ arg_ty <- dataConOrigArgTys data_con,
+ -- Use the same type variables
+ -- as the type constructor,
+ -- hence no need to instantiate
+ not (isUnLiftedType arg_ty) -- No constraints for unlifted types?
+ ]
+
+ mk_eqn_help gla_exts NewType tycon clas tys
+ | can_derive_via_isomorphism && (gla_exts || std_class_via_iso clas)
+ = -- Go ahead and use the isomorphism
+ traceTc (text "newtype deriving:" <+> ppr tycon <+> ppr rep_tys) `thenM_`
+ new_dfun_name clas tycon `thenM` \ dfun_name ->
+ returnM (Nothing, Just (InstInfo { iDFunId = mk_dfun dfun_name,
+ iBinds = NewTypeDerived rep_tys }))
+ | std_class gla_exts clas
+ = mk_eqn_help gla_exts DataType tycon clas tys -- Go via bale-out route
+
+ | otherwise -- Non-standard instance
+ = bale_out (if gla_exts then
+ cant_derive_err -- Too hard
+ else
+ non_std_err) -- Just complain about being a non-std instance
+ where
+ -- Here is the plan for newtype derivings. We see
+ -- newtype T a1...an = T (t ak...an) deriving (.., 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, _) = splitKindFunTys 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
+
+ right_arity = length tys + 1 == classArity clas
+
+ -- Never derive Read,Show,Typeable,Data this way
+ non_iso_classes = [readClassKey, showClassKey, typeableClassKey, dataClassKey]
+ can_derive_via_isomorphism
+ = not (getUnique clas `elem` non_iso_classes)
+ && right_arity -- Well kinded;
+ -- eg not: newtype T ... deriving( ST )
+ -- because ST needs *2* type params
+ && n_tyvars_to_keep >= 0 -- Type constructor has right kind:
+ -- eg not: newtype T = T Int deriving( Monad )
+ && n_args_to_keep >= 0 -- Rep type has right kind:
+ -- eg not: newtype T a = T Int deriving( Monad )
+ && eta_ok -- Eta reduction works
+ && not (isRecursiveTyCon tycon) -- Does not work for recursive tycons:
+ -- newtype A = MkA [A]
+ -- Don't want
+ -- instance Eq [A] => Eq A !!
+
+ -- Here's a recursive newtype that's actually OK
+ -- newtype S1 = S1 [T1 ()]
+ -- newtype T1 a = T1 (StateT S1 IO a ) deriving( Monad )
+ -- It's currently rejected. Oh well.
+
+ -- 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 isRecursiveTyCon tycon then
+ ptext SLIT("the newtype is recursive")
+ else empty,
+ if not right_arity then
+ quotes (ppr (mkClassPred clas tys)) <+> ptext SLIT("does not have arity 1")
+ else empty,
+ if not (n_tyvars_to_keep >= 0) then
+ ptext SLIT("the type constructor has wrong kind")
+ else if not (n_args_to_keep >= 0) then
+ ptext SLIT("the representation type has wrong kind")
+ else if not eta_ok then
+ ptext SLIT("the eta-reduction property does not hold")
+ else empty
+ ])
+
+ non_std_err = derivingThingErr clas tys tycon tyvars_to_keep
+ (vcat [non_std_why clas,
+ ptext SLIT("Try -fglasgow-exts for GHC's newtype-deriving extension")])
+
+ bale_out err = addErrTc err `thenM_` returnM (Nothing, Nothing)
+
+std_class gla_exts clas
+ = key `elem` derivableClassKeys
+ || (gla_exts && (key == typeableClassKey || key == dataClassKey))
+ where
+ key = classKey clas
+
+std_class_via_iso clas -- These standard classes can be derived for a newtype
+ -- using the isomorphism trick *even if no -fglasgow-exts*
+ = classKey clas `elem` [eqClassKey, ordClassKey, ixClassKey, boundedClassKey]
+ -- Not Read/Show because they respect the type
+ -- Not Enum, becuase newtypes are never in Enum
+
+
+new_dfun_name clas tycon -- Just a simple wrapper
+ = newDFunName clas [mkTyConApp tycon []] (getSrcLoc tycon)
+ -- The type passed to newDFunName is only used to generate
+ -- a suitable string; hence the empty type arg list
+
+------------------------------------------------------------------
+-- Check side conditions that dis-allow derivability for particular classes
+-- This is *apart* from the newtype-deriving mechanism
+
+checkSideConditions :: Bool -> Class -> TyCon -> [TcType] -> Maybe SDoc
+checkSideConditions gla_exts clas tycon tys
+ | notNull tys
+ = Just ty_args_why -- e.g. deriving( Foo s )
+ | otherwise
+ = case [cond | (key,cond) <- sideConditions, key == getUnique clas] of
+ [] -> Just (non_std_why clas)
+ [cond] -> cond (gla_exts, tycon)
+ other -> pprPanic "checkSideConditions" (ppr clas)
+ where
+ ty_args_why = quotes (ppr (mkClassPred clas tys)) <+> ptext SLIT("is not a class")
+
+non_std_why clas = quotes (ppr clas) <+> ptext SLIT("is not a derivable class")
+
+sideConditions :: [(Unique, Condition)]
+sideConditions
+ = [ (eqClassKey, cond_std),
+ (ordClassKey, cond_std),
+ (readClassKey, cond_std),
+ (showClassKey, cond_std),
+ (enumClassKey, cond_std `andCond` cond_isEnumeration),
+ (ixClassKey, cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)),
+ (boundedClassKey, cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)),
+ (typeableClassKey, cond_glaExts `andCond` cond_allTypeKind),
+ (dataClassKey, cond_glaExts `andCond` cond_std)
+ ]
+
+type Condition = (Bool, TyCon) -> Maybe SDoc -- Nothing => OK
+
+orCond :: Condition -> Condition -> Condition
+orCond c1 c2 tc
+ = case c1 tc of
+ Nothing -> Nothing -- c1 succeeds
+ Just x -> case c2 tc of -- c1 fails
+ Nothing -> Nothing
+ Just y -> Just (x $$ ptext SLIT(" and") $$ y)
+ -- Both fail
+
+andCond c1 c2 tc = case c1 tc of
+ Nothing -> c2 tc -- c1 succeeds
+ Just x -> Just x -- c1 fails
+
+cond_std :: Condition
+cond_std (gla_exts, tycon)
+ | any isExistentialDataCon data_cons = Just existential_why
+ | null data_cons = Just no_cons_why
+ | otherwise = Nothing
+ where
+ data_cons = tyConDataCons tycon
+ no_cons_why = quotes (ppr tycon) <+> ptext SLIT("has no data constructors")
+ existential_why = quotes (ppr tycon) <+> ptext SLIT("has existentially-quantified constructor(s)")
+
+cond_isEnumeration :: Condition
+cond_isEnumeration (gla_exts, tycon)
+ | isEnumerationTyCon tycon = Nothing
+ | otherwise = Just why
+ where
+ why = quotes (ppr tycon) <+> ptext SLIT("has non-nullary constructors")
- ------------------------------------------------------------------
- mk_eqn :: (Class, TyCon) -> DerivEqn
- -- we swizzle the tyvars and datacons out of the tycon
- -- to make the rest of the equation
+cond_isProduct :: Condition
+cond_isProduct (gla_exts, tycon)
+ | isProductTyCon tycon = Nothing
+ | otherwise = Just why
+ where
+ why = quotes (ppr tycon) <+> ptext SLIT("has more than one constructor")
- mk_eqn (clas, tycon)
- = (clas, tycon, tyvars, if_not_Eval 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
- extra_constraints
- | offensive_class = tyConTheta tycon
- | otherwise = []
- where
- offensive_class = clas_key `elem` needsDataDeclCtxtClassKeys
-
- mk_constraints data_con
- = [ (clas, [arg_ty])
- | arg_ty <- instd_arg_tys,
- not (isUnboxedType arg_ty) -- No constraints for unboxed types?
- ]
- where
- instd_arg_tys = dataConArgTys data_con tyvar_tys
+cond_allTypeKind :: Condition
+cond_allTypeKind (gla_exts, tycon)
+ | all (isArgTypeKind . tyVarKind) (tyConTyVars tycon) = Nothing
+ | otherwise = Just why
+ where
+ why = quotes (ppr tycon) <+> ptext SLIT("is parameterised over arguments of kind other than `*'")
+
+cond_glaExts :: Condition
+cond_glaExts (gla_exts, tycon) | gla_exts = Nothing
+ | otherwise = Just why
+ where
+ why = ptext SLIT("You need -fglasgow-exts to derive an instance for this class")
\end{code}
%************************************************************************
\end{itemize}
\begin{code}
-solveDerivEqns :: Bag InstInfo
- -> [DerivEqn]
- -> TcM s [InstInfo] -- Solns in same order as eqns.
- -- This bunch is Absolutely minimal...
+solveDerivEqns :: [DerivEqn]
+ -> TcM [DFunId] -- Solns in same order as eqns.
+ -- This bunch is Absolutely minimal...
-solveDerivEqns inst_decl_infos_in orig_eqns
- = iterateDeriv initial_solutions
+solveDerivEqns orig_eqns
+ = iterateDeriv 1 initial_solutions
where
-- The initial solutions for the equations claim that each
-- instance has an empty context; this solution is certainly
-- compares it with the current one; finishes if they are the
-- same, otherwise recurses with the new solutions.
-- It fails if any iteration fails
- iterateDeriv :: [DerivSoln] ->TcM s [InstInfo]
- iterateDeriv current_solns
- = checkNoErrsTc (iterateOnce current_solns) `thenTc` \ (new_inst_infos, new_solns) ->
+ iterateDeriv :: Int -> [DerivSoln] ->TcM [DFunId]
+ iterateDeriv n current_solns
+ | n > 20 -- Looks as if we are in an infinite loop
+ -- This can happen if we have -fallow-undecidable-instances
+ -- (See TcSimplify.tcSimplifyDeriv.)
+ = pprPanic "solveDerivEqns: probable loop"
+ (vcat (map pprDerivEqn orig_eqns) $$ ppr current_solns)
+ | otherwise
+ = let
+ dfuns = zipWithEqual "add_solns" mk_deriv_dfun orig_eqns current_solns
+ in
+ checkNoErrs (
+ -- Extend the inst info from the explicit instance decls
+ -- with the current set of solutions, and simplify each RHS
+ extendLocalInstEnv dfuns $
+ mappM gen_soln orig_eqns
+ ) `thenM` \ new_solns ->
if (current_solns == new_solns) then
- returnTc new_inst_infos
+ returnM dfuns
else
- iterateDeriv new_solns
+ iterateDeriv (n+1) new_solns
------------------------------------------------------------------
- iterateOnce current_solns
- = -- Extend the inst info from the explicit instance decls
- -- with the current set of solutions, giving a
-
- add_solns inst_decl_infos_in orig_eqns current_solns
- `thenNF_Tc` \ (new_inst_infos, inst_mapper) ->
- let
- class_to_inst_env cls = inst_mapper cls
- in
- -- Simplify each RHS
-
- listTc [ tcAddErrCtxt (derivCtxt tc) $
- tcSimplifyThetas class_to_inst_env deriv_rhs
- | (_,tc,_,deriv_rhs) <- orig_eqns ] `thenTc` \ next_solns ->
-
- -- Canonicalise the solutions, so they compare nicely
- let canonicalised_next_solns
- = [ sortLt (<) next_soln | next_soln <- next_solns ]
- in
- returnTc (new_inst_infos, canonicalised_next_solns)
-\end{code}
-
-\begin{code}
-add_solns :: Bag InstInfo -- The global, non-derived ones
- -> [DerivEqn] -> [DerivSoln]
- -> NF_TcM s ([InstInfo], -- The new, derived ones
- 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
-
- = 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)
- 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])
+ gen_soln (_, clas, tc,tyvars,deriv_rhs)
+ = addSrcSpan (srcLocSpan (getSrcLoc tc)) $
+ addErrCtxt (derivCtxt (Just clas) tc) $
+ tcSimplifyDeriv tyvars deriv_rhs `thenM` \ theta ->
+ returnM (sortLt (<) theta) -- Canonicalise before returning the soluction
+
+mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta
+ = mkDictFunId dfun_name tyvars theta
+ clas [mkTyConApp tycon (mkTyVarTys tyvars)]
+
+extendLocalInstEnv :: [DFunId] -> TcM a -> TcM a
+-- Add new locall-defined instances; don't bother to check
+-- for functional dependency errors -- that'll happen in TcInstDcls
+extendLocalInstEnv dfuns thing_inside
+ = do { env <- getGblEnv
+ ; let inst_env' = foldl extendInstEnv (tcg_inst_env env) dfuns
+ env' = env { tcg_inst_env = inst_env' }
+ ; setGblEnv env' thing_inside }
\end{code}
%************************************************************************
\item
We use the renamer!!! Reason: we're supposed to be
-producing @RenamedMonoBinds@ for the methods, but that means
+producing @LHsBinds Name@ 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 @RdrNameMonoBinds@ then heave 'em through
+So, instead, we produce @MonoBinds RdrName@ then heave 'em through
the renamer. What a great hack!
\end{itemize}
\begin{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)
- | otherwise
- = (clas_nm, tycon_nm,
- 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)
- 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
+-- Generate the InstInfo for the required instance,
+-- plus any auxiliary bindings required
+genInst :: DFunId -> TcM (InstInfo, LHsBinds RdrName)
+genInst dfun
+ = getFixityEnv `thenM` \ fix_env ->
+ let
+ (tyvars,_,clas,[ty]) = tcSplitDFunTy (idType dfun)
+ clas_nm = className clas
+ tycon = tcTyConAppTyCon ty
+ (meth_binds, aux_binds) = assoc "gen_bind:bad derived class"
+ gen_list (getUnique clas) fix_env tycon
+ in
+ -- Bring the right type variables into
+ -- scope, and rename the method binds
+ bindLocalNames (map varName tyvars) $
+ rnMethodBinds clas_nm [] meth_binds `thenM` \ (rn_meth_binds, _fvs) ->
+
+ -- Build the InstInfo
+ returnM (InstInfo { iDFunId = dfun, iBinds = VanillaInst rn_meth_binds [] },
+ aux_binds)
+
+gen_list :: [(Unique, FixityEnv -> TyCon -> (LHsBinds RdrName, LHsBinds RdrName))]
+gen_list = [(eqClassKey, no_aux_binds (ignore_fix_env gen_Eq_binds))
+ ,(ordClassKey, no_aux_binds (ignore_fix_env gen_Ord_binds))
+ ,(enumClassKey, no_aux_binds (ignore_fix_env gen_Enum_binds))
+ ,(boundedClassKey, no_aux_binds (ignore_fix_env gen_Bounded_binds))
+ ,(ixClassKey, no_aux_binds (ignore_fix_env gen_Ix_binds))
+ ,(typeableClassKey,no_aux_binds (ignore_fix_env gen_Typeable_binds))
+ ,(showClassKey, no_aux_binds gen_Show_binds)
+ ,(readClassKey, no_aux_binds gen_Read_binds)
+ ,(dataClassKey, gen_Data_binds)
+ ]
+
+ -- no_aux_binds is used for generators that don't
+ -- need to produce any auxiliary bindings
+no_aux_binds f fix_env tc = (f fix_env tc, emptyBag)
+ignore_fix_env f fix_env tc = f tc
\end{code}
con2tag_Foo :: Foo ... -> Int#
tag2con_Foo :: Int -> Foo ... -- easier if Int, not Int#
-maxtag_Foo :: Int -- ditto (NB: not unboxed)
+maxtag_Foo :: Int -- ditto (NB: not unlifted)
We have a @con2tag@ function for a tycon if:
If we have a @tag2con@ function, we also generate a @maxtag@ constant.
\begin{code}
-gen_taggery_Names :: [InstInfo]
- -> TcM s [(RdrName, -- for an assoc list
- TyCon, -- related tycon
- TagThingWanted)]
-
-gen_taggery_Names inst_infos
- = --pprTrace "gen_taggery:\n" (vcat [hsep [ppr c, ppr t] | (c,t) <- all_CTs]) $
- foldlTc do_con2tag [] tycons_of_interest `thenTc` \ names_so_far ->
- foldlTc do_tag2con names_so_far tycons_of_interest
+genTaggeryBinds :: [DFunId] -> TcM (LHsBinds RdrName)
+genTaggeryBinds dfuns
+ = do { names_so_far <- foldlM do_con2tag [] tycons_of_interest
+ ; nm_alist_etc <- foldlM do_tag2con names_so_far tycons_of_interest
+ ; return (listToBag (map gen_tag_n_con_monobind nm_alist_etc)) }
where
- all_CTs = [ (c, get_tycon ty) | (InstInfo c _ [ty] _ _ _ _ _ _) <- inst_infos ]
-
- get_tycon ty = case splitAlgTyConApp ty of { (tc, _, _) -> tc }
-
- all_tycons = map snd all_CTs
+ all_CTs = map simpleDFunClassTyCon dfuns
+ all_tycons = map snd all_CTs
(tycons_of_interest, _) = removeDups compare all_tycons
do_con2tag acc_Names tycon
| 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)))
+ && not (isProductTyCon tycon))
|| (we_are_deriving enumClassKey tycon)
- || (we_are_deriving ixClassKey tycon)
+ || (we_are_deriving ixClassKey tycon))
- = returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag)
+ = returnM ((con2tag_RDR tycon, tycon, GenCon2Tag)
: acc_Names)
| otherwise
- = returnTc acc_Names
+ = returnM acc_Names
do_tag2con acc_Names tycon
- = 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)
+ = 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 all_CTs
is_in_eqns clas_key tycon ((c,t):cts)
= (clas_key == classKey c && tycon == t)
|| is_in_eqns clas_key tycon cts
-
\end{code}
\begin{code}
-derivingThingErr :: FAST_STRING -> FAST_STRING -> TyCon -> ErrMsg
+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)])
-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)))
+malformedPredErr tycon pred = ptext SLIT("Illegal deriving item") <+> ppr pred
-derivCtxt tycon
- = ptext SLIT("When deriving classes for") <+> quotes (ppr tycon)
+derivCtxt :: Maybe Class -> TyCon -> SDoc
+derivCtxt maybe_cls tycon
+ = ptext SLIT("When deriving") <+> cls <+> ptext SLIT("for type") <+> quotes (ppr tycon)
+ where
+ cls = case maybe_cls of
+ Nothing -> ptext SLIT("instances")
+ Just c -> ptext SLIT("the") <+> quotes (ppr c) <+> ptext SLIT("instance")
\end{code}
+
projects / ghc-hetmet.git / blobdiff