#include "HsVersions.h"
-import HsSyn ( HsBinds(..), MonoBinds(..), TyClDecl(..),
- collectLocatedMonoBinders )
-import RdrHsSyn ( RdrNameMonoBinds )
-import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds, RenamedTyClDecl )
-import CmdLineOpts ( DynFlag(..), DynFlags )
-
-import TcMonad
-import TcEnv ( tcSetInstEnv, newDFunName, InstInfo(..), pprInstInfo,
- tcLookupClass, tcLookupTyCon
+import HsSyn
+import DynFlags ( DynFlag(..) )
+
+import Generics ( mkTyConGenericBinds )
+import TcRnMonad
+import TcEnv ( newDFunName, pprInstInfoDetails,
+ InstInfo(..), InstBindings(..), simpleInstInfoClsTy,
+ tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv
)
import TcGenDeriv -- Deriv stuff
-import InstEnv ( InstEnv, simpleDFunClassTyCon, extendInstEnv )
-import TcSimplify ( tcSimplifyThetas )
-
-import RnBinds ( rnMethodBinds, rnTopMonoBinds )
-import RnEnv ( bindLocatedLocalsRn )
-import RnMonad ( renameDerivedCode, thenRn, mapRn, returnRn )
-import HscTypes ( DFunId, PersistentRenamerState )
-
-import BasicTypes ( Fixity )
-import Class ( classKey, Class )
-import ErrUtils ( dumpIfSet_dyn, Message )
+import InstEnv ( Instance, OverlapFlag, mkLocalInstance, instanceHead, extendInstEnvList )
+import Inst ( getOverlapFlag )
+import TcHsType ( tcHsDeriv )
+import TcSimplify ( tcSimplifyDeriv )
+
+import RnBinds ( rnMethodBinds, rnTopBinds )
+import RnEnv ( bindLocalNames )
+import HscTypes ( FixityEnv )
+
+import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class )
+import Type ( zipOpenTvSubst, substTheta )
+import ErrUtils ( dumpIfSet_dyn )
import MkId ( mkDictFunId )
-import DataCon ( dataConArgTys, isNullaryDataCon, isExistentialDataCon )
-import PrelInfo ( needsDataDeclCtxtClassKeys )
-import Maybes ( maybeToBool, catMaybes )
-import Module ( Module )
-import Name ( Name, getSrcLoc )
+import DataCon ( isNullarySrcDataCon, isVanillaDataCon, dataConOrigArgTys )
+import Maybes ( catMaybes )
import RdrName ( RdrName )
-
-import TyCon ( tyConTyVars, tyConDataCons,
- tyConTheta, maybeTyConSingleCon, isDataTyCon,
- isEnumerationTyCon, TyCon
+import Name ( Name, getSrcLoc )
+import NameSet ( duDefs )
+import Kind ( splitKindFunTys )
+import TyCon ( tyConTyVars, tyConDataCons, tyConArity, tyConHasGenerics,
+ tyConStupidTheta, isProductTyCon, isDataTyCon, newTyConRhs,
+ isEnumerationTyCon, isRecursiveTyCon, TyCon
)
-import Type ( TauType, ThetaType, PredType, mkTyVarTys, mkTyConApp,
- isUnLiftedType, mkClassPred )
-import Var ( TyVar )
+import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, tcTyConAppTyCon,
+ isUnLiftedType, mkClassPred, tyVarsOfTypes, isArgTypeKind,
+ tcEqTypes, tcSplitAppTys, mkAppTys )
+import Var ( TyVar, tyVarKind, varName )
+import VarSet ( mkVarSet, subVarSet )
import PrelNames
-import Util ( zipWithEqual, sortLt )
-import ListSetOps ( removeDups, assoc )
+import SrcLoc ( srcLocSpan, Located(..) )
+import Util ( zipWithEqual, sortLe, notNull )
+import ListSetOps ( removeDups, assocMaybe )
import Outputable
-import List ( nub )
+import Bag
\end{code}
%************************************************************************
-- The Name is the name for the DFun we'll build
-- The tyvars bind all the variables in the RHS
+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".
+
+[Newtype deriving]
+~~~~~~~~~~~~~~~~~~
+Consider this:
+ class C a b
+ instance C [a] Char
+ newtype T = T Char deriving( C [a] )
+
+Notice the free 'a' in the deriving. We have to fill this out to
+ newtype T = T Char deriving( forall a. C [a] )
+
+And then translate it to:
+ instance C [a] Char => C [a] T where ...
+
+
+
%************************************************************************
%* *
%************************************************************************
\begin{code}
-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_in get_fixity tycl_decls
- = recoverTc (returnTc ([], EmptyBinds)) $
-
- -- Fish the "deriving"-related information out of the TcEnv
- -- and make the necessary "equations".
- makeDerivEqns tycl_decls `thenTc` \ eqns ->
- if null eqns then
- returnTc ([], EmptyBinds)
- else
-
- -- Take the equation list and solve it, to deliver a list of
- -- solutions, a.k.a. the contexts for the instance decls
- -- required for the corresponding equations.
- solveDerivEqns inst_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 ->
-
- tcGetEnv `thenNF_Tc` \ env ->
- getDOptsTc `thenTc` \ dflags ->
- 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 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
-
- ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances"
- (ddump_deriving new_inst_infos rn_extra_binds)) `thenTc_`
-
- returnTc (new_inst_infos, rn_extra_binds)
+tcDeriving :: [LTyClDecl Name] -- All type constructors
+ -> TcM ([InstInfo], -- The generated "instance decls"
+ HsValBinds Name) -- Extra generated top-level bindings
+
+tcDeriving tycl_decls
+ = recoverM (returnM ([], emptyValBindsOut)) $
+ do { -- Fish the "deriving"-related information out of the TcEnv
+ -- and make the necessary "equations".
+ overlap_flag <- getOverlapFlag
+ ; (ordinary_eqns, newtype_inst_info) <- makeDerivEqns overlap_flag tycl_decls
+
+ ; (ordinary_inst_info, deriv_binds)
+ <- extendLocalInstEnv (map iSpec newtype_inst_info) $
+ deriveOrdinaryStuff overlap_flag ordinary_eqns
+ -- Add the newtype-derived instances to the inst env
+ -- before tacking the "ordinary" ones
+
+ ; let inst_info = newtype_inst_info ++ ordinary_inst_info
+
+ -- If we are compiling a hs-boot file,
+ -- don't generate any derived bindings
+ ; is_boot <- tcIsHsBoot
+ ; if is_boot then
+ return (inst_info, emptyValBindsOut)
+ else do
+ {
+
+ -- Generate the generic to/from functions from each type declaration
+ ; gen_binds <- mkGenericBinds tycl_decls
+
+ -- 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
+ <- discardWarnings $ setOptM Opt_GlasgowExts $ do
+ { (rn_deriv, _dus1) <- rnTopBinds (ValBindsIn deriv_binds [])
+ ; (rn_gen, dus_gen) <- rnTopBinds (ValBindsIn gen_binds [])
+ ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to
+ -- be kept alive
+ ; return (rn_deriv `plusHsValBinds` rn_gen) }
+
+
+ ; dflags <- getDOpts
+ ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances"
+ (ddump_deriving inst_info rn_binds))
+
+ ; returnM (inst_info, rn_binds)
+ }}
where
- ddump_deriving :: [InstInfo] -> RenamedHsBinds -> SDoc
+ ddump_deriving :: [InstInfo] -> HsValBinds Name -> SDoc
ddump_deriving inst_infos extra_binds
- = vcat (map pprInstInfo inst_infos) $$ ppr extra_binds
- where
-
- -- Make a Real dfun instead of the dummy one we have so far
- gen_inst_info :: DFunId -> RenamedMonoBinds -> InstInfo
- gen_inst_info dfun binds
- = InstInfo { iDFunId = dfun,
- iBinds = binds, iPrags = [] }
-
- rn_meths meths = rnMethodBinds [] meths `thenRn` \ (meths', _) -> returnRn meths'
- -- Ignore the free vars returned
+ = vcat (map pprInstInfoDetails inst_infos) $$ ppr extra_binds
+
+-----------------------------------------
+deriveOrdinaryStuff overlap_flag [] -- Short cut
+ = returnM ([], emptyLHsBinds)
+
+deriveOrdinaryStuff overlap_flag 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.
+ inst_specs <- solveDerivEqns overlap_flag eqns
+
+ -- Generate the InstInfo for each dfun,
+ -- plus any auxiliary bindings it needs
+ ; (inst_infos, aux_binds_s) <- mapAndUnzipM genInst inst_specs
+
+ -- Generate any extra not-one-inst-decl-specific binds,
+ -- notably "con2tag" and/or "tag2con" functions.
+ ; extra_binds <- genTaggeryBinds inst_infos
+
+ -- 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 :: [RenamedTyClDecl] -> TcM [DerivEqn]
-
-makeDerivEqns tycl_decls
- = mapTc mk_eqn derive_these `thenTc` \ maybe_eqns ->
- returnTc (catMaybes maybe_eqns)
+makeDerivEqns :: OverlapFlag
+ -> [LTyClDecl Name]
+ -> TcM ([DerivEqn], -- Ordinary derivings
+ [InstInfo]) -- Special newtype derivings
+
+makeDerivEqns overlap_flag tycl_decls
+ = mapAndUnzipM mk_eqn derive_these `thenM` \ (maybe_ordinaries, maybe_newtypes) ->
+ returnM (catMaybes maybe_ordinaries, catMaybes maybe_newtypes)
where
------------------------------------------------------------------
- derive_these :: [(Name, Name)]
- -- Find the (Class,TyCon) pairs that must be `derived'
- -- NB: only source-language decls have deriving, no imported ones do
- derive_these = [ (clas,tycon)
- | TyData {tcdName = tycon, tcdDerivs = Just classes} <- tycl_decls,
- clas <- nub classes ]
+ derive_these :: [(NewOrData, Name, LHsType Name)]
+ -- Find the (nd, TyCon, Pred) pairs that must be `derived'
+ derive_these = [ (nd, tycon, pred)
+ | L _ (TyData { tcdND = nd, tcdLName = L _ tycon,
+ tcdDerivs = Just preds }) <- tycl_decls,
+ pred <- preds ]
------------------------------------------------------------------
- mk_eqn :: (Name, Name) -> NF_TcM (Maybe DerivEqn)
- -- we swizzle the tyvars and datacons out of the tycon
+ mk_eqn :: (NewOrData, Name, LHsType Name) -> TcM (Maybe DerivEqn, Maybe InstInfo)
+ -- We swizzle the tyvars and datacons out of the tycon
-- to make the rest of the equation
+ --
+ -- The "deriv_ty" is a LHsType to take account of the fact that for newtype derivign
+ -- we allow deriving (forall a. C [a]).
+
+ mk_eqn (new_or_data, tycon_name, hs_deriv_ty)
+ = tcLookupTyCon tycon_name `thenM` \ tycon ->
+ setSrcSpan (srcLocSpan (getSrcLoc tycon)) $
+ addErrCtxt (derivCtxt Nothing tycon) $
+ tcExtendTyVarEnv (tyConTyVars tycon) $ -- Deriving preds may (now) mention
+ -- the type variables for the type constructor
+ tcHsDeriv hs_deriv_ty `thenM` \ (deriv_tvs, clas, tys) ->
+ doptM Opt_GlasgowExts `thenM` \ gla_exts ->
+ mk_eqn_help gla_exts new_or_data tycon deriv_tvs clas tys
- mk_eqn (clas_name, tycon_name)
- = tcLookupClass clas_name `thenNF_Tc` \ clas ->
- tcLookupTyCon tycon_name `thenNF_Tc` \ tycon ->
- let
- clas_key = classKey clas
- tyvars = tyConTyVars tycon
- tyvar_tys = mkTyVarTys tyvars
- ty = mkTyConApp tycon tyvar_tys
- data_cons = tyConDataCons tycon
- locn = getSrcLoc tycon
- constraints = extra_constraints ++ concat (map mk_constraints data_cons)
-
- -- "extra_constraints": see notes above about contexts on data decls
- extra_constraints
- | offensive_class = tyConTheta tycon
- | otherwise = []
-
- offensive_class = clas_key `elem` needsDataDeclCtxtClassKeys
+ ------------------------------------------------------------------
+ mk_eqn_help gla_exts DataType tycon deriv_tvs clas tys
+ | Just err <- checkSideConditions gla_exts tycon deriv_tvs clas tys
+ = bale_out (derivingThingErr clas tys tycon (tyConTyVars tycon) err)
+ | otherwise
+ = do { eqn <- mkDataTypeEqn tycon clas
+ ; returnM (Just eqn, Nothing) }
+
+ mk_eqn_help gla_exts NewType tycon deriv_tvs 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 { iSpec = mk_inst_spec dfun_name,
+ iBinds = NewTypeDerived rep_tys }))
+ | std_class gla_exts clas
+ = mk_eqn_help gla_exts DataType tycon deriv_tvs 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 t is a type,
+ -- ak...an is a suffix of a1..an
+ -- ak...an do not occur free in t,
+ -- (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...ap) => C s1 .. sm (T a1...ap)
+ -- where T a1...ap is the partial application of the LHS of the correct kind
+ -- and p >= k
+ --
+ -- 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)
+ -- (Actually we don't need the coerce, because non-rec newtypes are transparent
+
+ 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]
+ -- Need newTyConRhs *not* newTyConRep to get the representation
+ -- type, because the latter looks through all intermediate newtypes
+ -- 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!
+ (tc_tvs, rep_ty) = newTyConRhs 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 tc_tvs
+ tyvars_to_keep = take n_tyvars_to_keep tc_tvs
+
+ 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 (zipOpenTvSubst clas_tyvars inst_tys)
+ (classSCTheta clas)
+
+ -- If there are no tyvars, there's no need
+ -- to abstract over the dictionaries we need
+ dict_tvs = deriv_tvs ++ tc_tvs
+ dict_args | null dict_tvs = []
+ | otherwise = rep_pred : sc_theta
+
+ -- Finally! Here's where we build the dictionary Id
+ mk_inst_spec dfun_name
+ = mkLocalInstance dfun overlap_flag
+ where
+ dfun = mkDictFunId dfun_name dict_tvs 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.
+ -- In fact we generate an instance decl that has method of form
+ -- meth @ instTy = meth @ repTy
+ -- (no coerce's). We'd need a coerce if we wanted to handle
+ -- recursive newtypes too
+
+ -- 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
- mk_constraints data_con
- = [ mkClassPred clas [arg_ty]
- | arg_ty <- dataConArgTys data_con tyvar_tys,
- not (isUnLiftedType arg_ty) -- No constraints for unlifted types?
- ]
- in
- case chk_out clas tycon of
- Just err -> addErrTc err `thenNF_Tc_`
- returnNF_Tc Nothing
- Nothing -> newDFunName clas [ty] locn `thenNF_Tc` \ dfun_name ->
- returnNF_Tc (Just (dfun_name, clas, tycon, tyvars, constraints))
-
+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
+
+------------------------------------------------------------------
+mkDataTypeEqn :: TyCon -> Class -> TcM DerivEqn
+mkDataTypeEqn tycon clas
+ | clas `hasKey` typeableClassKey
+ = -- The Typeable class is special in several ways
+ -- data T a b = ... deriving( Typeable )
+ -- gives
+ -- instance Typeable2 T where ...
+ -- Notice that:
+ -- 1. There are no constraints in the instance
+ -- 2. There are no type variables either
+ -- 3. The actual class we want to generate isn't necessarily
+ -- Typeable; it depends on the arity of the type
+ do { real_clas <- tcLookupClass (typeableClassNames !! tyConArity tycon)
+ ; dfun_name <- new_dfun_name real_clas tycon
+ ; return (dfun_name, real_clas, tycon, [], []) }
+ | otherwise
+ = do { dfun_name <- new_dfun_name clas tycon
+ ; return (dfun_name, clas, tycon, tyvars, constraints) }
+ where
+ tyvars = tyConTyVars tycon
+ constraints = extra_constraints ++ ordinary_constraints
+ extra_constraints = tyConStupidTheta tycon
+ -- "extra_constraints": see note [Data decl contexts] above
+
+ ordinary_constraints
+ = [ mkClassPred clas [arg_ty]
+ | data_con <- tyConDataCons tycon,
+ arg_ty <- dataConOrigArgTys data_con,
+ not (isUnLiftedType arg_ty) -- No constraints for unlifted types?
+ ]
+
+
+------------------------------------------------------------------
+-- Check side conditions that dis-allow derivability for particular classes
+-- This is *apart* from the newtype-deriving mechanism
+
+checkSideConditions :: Bool -> TyCon -> [TyVar] -> Class -> [TcType] -> Maybe SDoc
+checkSideConditions gla_exts tycon deriv_tvs clas tys
+ | notNull deriv_tvs || 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_typeableOK),
+ (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 (not . isVanillaDataCon) 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 non-Haskell-98 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")
- ------------------------------------------------------------------
- chk_out :: Class -> TyCon -> Maybe Message
- chk_out clas tycon
- | clas `hasKey` enumClassKey && not is_enumeration = bog_out nullary_why
- | clas `hasKey` boundedClassKey && not is_enumeration_or_single = bog_out single_nullary_why
- | clas `hasKey` ixClassKey && not is_enumeration_or_single = bog_out single_nullary_why
- | any isExistentialDataCon (tyConDataCons tycon) = Just (existentialErr clas tycon)
- | otherwise = Nothing
- where
- is_enumeration = isEnumerationTyCon tycon
- is_single_con = maybeToBool (maybeTyConSingleCon tycon)
- is_enumeration_or_single = is_enumeration || is_single_con
-
- single_nullary_why = SLIT("one constructor data type or type with all nullary constructors expected")
- nullary_why = SLIT("data type with all nullary constructors expected")
+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")
+
+cond_typeableOK :: Condition
+-- OK for Typeable class
+-- Currently: (a) args all of kind *
+-- (b) 7 or fewer args
+cond_typeableOK (gla_exts, tycon)
+ | tyConArity tycon > 7 = Just too_many
+ | not (all (isArgTypeKind . tyVarKind) (tyConTyVars tycon)) = Just bad_kind
+ | otherwise = Nothing
+ where
+ too_many = quotes (ppr tycon) <+> ptext SLIT("has too many arguments")
+ bad_kind = quotes (ppr tycon) <+> ptext SLIT("has arguments of kind other than `*'")
- bog_out why = Just (derivingThingErr clas tycon why)
+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 :: InstEnv
+solveDerivEqns :: OverlapFlag
-> [DerivEqn]
- -> TcM [DFunId] -- Solns in same order as eqns.
+ -> TcM [Instance]-- Solns in same order as eqns.
-- This bunch is Absolutely minimal...
-solveDerivEqns inst_env_in orig_eqns
- = iterateDeriv initial_solutions
+solveDerivEqns overlap_flag 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 [DFunId]
- iterateDeriv current_solns
- = checkNoErrsTc (iterateOnce current_solns)
- `thenTc` \ (new_dfuns, new_solns) ->
+ iterateDeriv :: Int -> [DerivSoln] -> TcM [Instance]
+ 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
+ inst_specs = zipWithEqual "add_solns" mk_inst_spec
+ 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 inst_specs $
+ mappM gen_soln orig_eqns
+ ) `thenM` \ new_solns ->
if (current_solns == new_solns) then
- returnTc new_dfuns
+ returnM inst_specs
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
- getDOptsTc `thenTc` \ dflags ->
- let (new_dfuns, inst_env) =
- add_solns dflags inst_env_in orig_eqns current_solns
- 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 (<) next_soln | next_soln <- next_solns ]
- in
- returnTc (new_dfuns, canonicalised_next_solns)
-\end{code}
+ gen_soln (_, clas, tc,tyvars,deriv_rhs)
+ = setSrcSpan (srcLocSpan (getSrcLoc tc)) $
+ addErrCtxt (derivCtxt (Just clas) tc) $
+ tcSimplifyDeriv tc tyvars deriv_rhs `thenM` \ theta ->
+ returnM (sortLe (<=) theta) -- Canonicalise before returning the soluction
-\begin{code}
-add_solns :: DynFlags
- -> InstEnv -- The global, non-derived ones
- -> [DerivEqn] -> [DerivSoln]
- -> ([DFunId], InstEnv)
- -- the eqns and solns move "in lockstep"; we have the eqns
- -- because we need the LHS info for addClassInstance.
-
-add_solns dflags inst_env_in eqns solns
- = (new_dfuns, inst_env)
- where
- new_dfuns = zipWithEqual "add_solns" mk_deriv_dfun eqns solns
- (inst_env, _) = extendInstEnv dflags inst_env_in 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
+ ------------------------------------------------------------------
+ mk_inst_spec (dfun_name, clas, tycon, tyvars, _) theta
+ = mkLocalInstance dfun overlap_flag
+ where
+ dfun = mkDictFunId dfun_name tyvars theta clas
+ [mkTyConApp tycon (mkTyVarTys tyvars)]
+
+extendLocalInstEnv :: [Instance] -> TcM a -> TcM a
+-- Add new locally-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' = extendInstEnvList (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 :: (Name -> Maybe Fixity) -> DFunId -> RdrNameMonoBinds
-gen_bind get_fixity dfun
- | clas `hasKey` showClassKey = gen_Show_binds get_fixity tycon
- | clas `hasKey` readClassKey = gen_Read_binds get_fixity tycon
+-- Generate the InstInfo for the required instance,
+-- plus any auxiliary bindings required
+genInst :: Instance -> TcM (InstInfo, LHsBinds RdrName)
+genInst spec
+ = do { fix_env <- getFixityEnv
+ ; let
+ (tyvars,_,clas,[ty]) = instanceHead spec
+ clas_nm = className clas
+ tycon = tcTyConAppTyCon ty
+ (meth_binds, aux_binds) = genDerivBinds clas fix_env tycon
+
+ -- Bring the right type variables into
+ -- scope, and rename the method binds
+ -- It's a bit yukky that we return *renamed* InstInfo, but
+ -- *non-renamed* auxiliary bindings
+ ; (rn_meth_binds, _fvs) <- discardWarnings $
+ bindLocalNames (map varName tyvars) $
+ rnMethodBinds clas_nm [] meth_binds
+
+ -- Build the InstInfo
+ ; return (InstInfo { iSpec = spec,
+ iBinds = VanillaInst rn_meth_binds [] },
+ aux_binds)
+ }
+
+genDerivBinds clas fix_env tycon
+ | className clas `elem` typeableClassNames
+ = (gen_Typeable_binds tycon, emptyLHsBinds)
+
| otherwise
- = assoc "gen_bind:bad derived class"
- [(eqClassKey, gen_Eq_binds)
- ,(ordClassKey, gen_Ord_binds)
- ,(enumClassKey, gen_Enum_binds)
- ,(boundedClassKey, gen_Bounded_binds)
- ,(ixClassKey, gen_Ix_binds)
- ]
- (classKey clas)
- tycon
+ = case assocMaybe gen_list (getUnique clas) of
+ Just gen_fn -> gen_fn fix_env tycon
+ Nothing -> pprPanic "genDerivBinds: bad derived class" (ppr clas)
where
- (clas, tycon) = simpleDFunClassTyCon dfun
+ 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, emptyLHsBinds)
+ ignore_fix_env f fix_env tc = f tc
\end{code}
If we have a @tag2con@ function, we also generate a @maxtag@ constant.
\begin{code}
-gen_taggery_Names :: [DFunId]
- -> TcM [(RdrName, -- for an assoc list
- TyCon, -- related tycon
- TagThingWanted)]
-
-gen_taggery_Names dfuns
- = foldlTc do_con2tag [] tycons_of_interest `thenTc` \ names_so_far ->
- foldlTc do_tag2con names_so_far tycons_of_interest
+genTaggeryBinds :: [InstInfo] -> TcM (LHsBinds RdrName)
+genTaggeryBinds infos
+ = 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 = map simpleDFunClassTyCon dfuns
+ all_CTs = [ (cls, tcTyConAppTyCon ty)
+ | info <- infos,
+ let (cls,ty) = simpleInstInfoClsTy info ]
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
- && any isNullaryDataCon (tyConDataCons tycon))
+ && any isNullarySrcDataCon (tyConDataCons tycon))
|| (we_are_deriving ordClassKey tycon
- && not (maybeToBool (maybeTyConSingleCon tycon)))
+ && not (isProductTyCon tycon))
|| (we_are_deriving enumClassKey tycon)
|| (we_are_deriving ixClassKey tycon))
- = returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag)
+ = returnM ((con2tag_RDR tycon, tycon, GenCon2Tag)
: acc_Names)
| otherwise
- = returnTc acc_Names
+ = returnM acc_Names
do_tag2con acc_Names tycon
| isDataTyCon tycon &&
(we_are_deriving enumClassKey tycon ||
we_are_deriving ixClassKey tycon
&& isEnumerationTyCon tycon)
- = returnTc ( (tag2con_RDR tycon, tycon, GenTag2Con)
+ = returnM ( (tag2con_RDR tycon, tycon, GenTag2Con)
: (maxtag_RDR tycon, tycon, GenMaxTag)
: acc_Names)
| otherwise
- = returnTc acc_Names
+ = returnM acc_Names
we_are_deriving clas_key tycon
= is_in_eqns clas_key tycon all_CTs
\end{code}
\begin{code}
-derivingThingErr :: Class -> TyCon -> FAST_STRING -> Message
-
-derivingThingErr clas tycon why
- = sep [hsep [ptext SLIT("Can't make a derived instance of"), quotes (ppr clas)],
- hsep [ptext SLIT("for the type"), quotes (ppr tycon)],
- parens (ptext why)]
-
-existentialErr clas tycon
- = sep [ptext SLIT("Can't derive any instances for type") <+> quotes (ppr tycon),
- ptext SLIT("because it has existentially-quantified constructor(s)")]
+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)])
-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}
+
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