\begin{code}
module TcClassDcl ( tcClassSigs, tcClassDecl2,
getGenericInstances,
- MethodSpec, tcMethodBind, mkMethodBind,
+ MethodSpec, tcMethodBind, mkMethId,
tcAddDeclCtxt, badMethodErr, badATErr, omittedATWarn
) where
import TcType
import TcRnMonad
import Generics
-import PrelInfo
import Class
import TyCon
import Type
import MkId
import Id
import Name
+import Var
import NameEnv
import NameSet
import OccName
import BasicTypes
import Bag
import FastString
+
+import Control.Monad
\end{code}
-- between tcClassSigs and buildClass
tcClassSigs clas sigs def_methods
= do { dm_env <- checkDefaultBinds clas op_names def_methods
- ; mappM (tcClassSig dm_env) op_sigs }
+ ; mapM (tcClassSig dm_env) op_sigs }
where
op_sigs = [sig | sig@(L _ (TypeSig _ _)) <- sigs]
- op_names = [n | sig@(L _ (TypeSig (L _ n) _)) <- op_sigs]
+ op_names = [n | (L _ (TypeSig (L _ n) _)) <- op_sigs]
checkDefaultBinds :: Name -> [Name] -> LHsBinds Name -> TcM (NameEnv Bool)
= do dm_infos <- mapM (addLocM (checkDefaultBind clas ops)) (bagToList binds)
return (mkNameEnv dm_infos)
+checkDefaultBind :: Name -> [Name] -> HsBindLR Name Name -> TcM (Name, Bool)
checkDefaultBind clas ops (FunBind {fun_id = L _ op, fun_matches = MatchGroup matches _ })
= do { -- Check that the op is from this class
checkTc (op `elem` ops) (badMethodErr clas op)
-- Check that all the defns ar generic, or none are
; checkTc (all_generic || none_generic) (mixedGenericErr op)
- ; returnM (op, all_generic)
+ ; return (op, all_generic)
}
where
n_generic = count (isJust . maybeGenericMatch) matches
none_generic = n_generic == 0
all_generic = matches `lengthIs` n_generic
+checkDefaultBind _ _ b = pprPanic "checkDefaultBind" (ppr b)
tcClassSig :: NameEnv Bool -- Info about default methods;
Nothing -> NoDefMeth
Just False -> DefMeth
Just True -> GenDefMeth
- ; returnM (op_name, dm, op_ty) }
+ ; return (op_name, dm, op_ty) }
+tcClassSig _ s = pprPanic "tcClassSig" (ppr s)
\end{code}
%************************************************************************
%* *
-\subsection[Default methods]{Default methods}
+ Class Declarations
%* *
%************************************************************************
-The default methods for a class are each passed a dictionary for the
-class, so that they get access to the other methods at the same type.
-So, given the class decl
-\begin{verbatim}
-class Foo a where
- op1 :: a -> Bool
- op2 :: Ord b => a -> b -> b -> b
-
- op1 x = True
- op2 x y z = if (op1 x) && (y < z) then y else z
-\end{verbatim}
-we get the default methods:
-\begin{verbatim}
-defm.Foo.op1 :: forall a. Foo a => a -> Bool
-defm.Foo.op1 = /\a -> \dfoo -> \x -> True
-
-defm.Foo.op2 :: forall a. Foo a => forall b. Ord b => a -> b -> b -> b
-defm.Foo.op2 = /\ a -> \ dfoo -> /\ b -> \ dord -> \x y z ->
- if (op1 a dfoo x) && (< b dord y z) then y else z
-\end{verbatim}
-
-When we come across an instance decl, we may need to use the default
-methods:
-\begin{verbatim}
-instance Foo Int where {}
-\end{verbatim}
-gives
-\begin{verbatim}
-const.Foo.Int.op1 :: Int -> Bool
-const.Foo.Int.op1 = defm.Foo.op1 Int dfun.Foo.Int
-
-const.Foo.Int.op2 :: forall b. Ord b => Int -> b -> b -> b
-const.Foo.Int.op2 = defm.Foo.op2 Int dfun.Foo.Int
-
-dfun.Foo.Int :: Foo Int
-dfun.Foo.Int = (const.Foo.Int.op1, const.Foo.Int.op2)
-\end{verbatim}
-Notice that, as with method selectors above, we assume that dictionary
-application is curried, so there's no need to mention the Ord dictionary
-in const.Foo.Int.op2 (or the type variable).
-
-\begin{verbatim}
-instance Foo a => Foo [a] where {}
-
-dfun.Foo.List :: forall a. Foo a -> Foo [a]
-dfun.Foo.List
- = /\ a -> \ dfoo_a ->
- let rec
- op1 = defm.Foo.op1 [a] dfoo_list
- op2 = defm.Foo.op2 [a] dfoo_list
- dfoo_list = (op1, op2)
- in
- dfoo_list
-\end{verbatim}
-
-@tcClassDecls2@ generates bindings for polymorphic default methods
-(generic default methods have by now turned into instance declarations)
-
\begin{code}
tcClassDecl2 :: LTyClDecl Name -- The class declaration
-> TcM (LHsBinds Id, [Id])
tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs,
tcdMeths = default_binds}))
- = recoverM (returnM (emptyLHsBinds, [])) $
- setSrcSpan loc $
- tcLookupLocatedClass class_name `thenM` \ clas ->
+ = recoverM (return (emptyLHsBinds, [])) $
+ setSrcSpan loc $ do
+ clas <- tcLookupLocatedClass class_name
-- We make a separate binding for each default method.
-- At one time I used a single AbsBinds for all of them, thus
-- default method for every class op, regardless of whether or not
-- the programmer supplied an explicit default decl for the class.
-- (If necessary we can fix that, but we don't have a convenient Id to hand.)
- in
- mapAndUnzipM tc_dm dm_sel_ids `thenM` \ (defm_binds, dm_ids_s) ->
- returnM (listToBag defm_binds, concat dm_ids_s)
+
+ (defm_binds, dm_ids_s) <- mapAndUnzipM tc_dm dm_sel_ids
+ return (listToBag defm_binds, concat dm_ids_s)
+tcClassDecl2 d = pprPanic "tcClassDecl2" (ppr d)
+tcDefMeth :: InstOrigin -> Class -> [TyVar] -> LHsBinds Name
+ -> TcSigFun -> TcPragFun -> Id
+ -> TcM (LHsBindLR Id Var, [Id])
tcDefMeth origin clas tyvars binds_in sig_fn prag_fn sel_id
= do { dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_id)
; let inst_tys = mkTyVarTys tyvars
cls_pred = mkClassPred clas inst_tys
local_dm_id = mkDefaultMethodId dm_name dm_ty
- ; (_, meth_info) <- mkMethodBind origin clas inst_tys binds_in (sel_id, DefMeth)
; loc <- getInstLoc origin
; this_dict <- newDictBndr loc cls_pred
- ; (defm_bind, insts_needed) <- getLIE (tcMethodBind tyvars [cls_pred] [this_dict]
- sig_fn prag_fn meth_info)
+ ; (_, meth_id) <- mkMethId origin clas sel_id inst_tys
+ ; (defm_bind, insts_needed) <- getLIE $
+ tcMethodBind origin tyvars [cls_pred] this_dict []
+ sig_fn prag_fn binds_in
+ (sel_id, DefMeth) meth_id
; addErrCtxt (defltMethCtxt clas) $ do
-- We'll have an inline pragma on the local binding, made by tcMethodBind
-- but that's not enough; we want one on the global default method too
-- Specialisations, on the other hand, belong on the thing inside only, I think
- ; let (_,dm_inst_id,_) = meth_info
- sel_name = idName sel_id
+ ; let sel_name = idName sel_id
inline_prags = filter isInlineLSig (prag_fn sel_name)
- ; prags <- tcPrags dm_inst_id inline_prags
+ ; prags <- tcPrags meth_id inline_prags
; let full_bind = AbsBinds tyvars
[instToId this_dict]
- [(tyvars, local_dm_id, dm_inst_id, prags)]
+ [(tyvars, local_dm_id, meth_id, prags)]
(dict_binds `unionBags` defm_bind)
- ; returnM (noLoc full_bind, [local_dm_id]) }}
+ ; return (noLoc full_bind, [local_dm_id]) }}
mkDefMethRdrName :: Id -> RdrName
mkDefMethRdrName sel_id = mkDerivedRdrName (idName sel_id) mkDefaultMethodOcc
LHsBind Name) -- Binding for the method
tcMethodBind
- :: [TcTyVar] -- Skolemised type variables for the
+ :: InstOrigin
+ -> [TcTyVar] -- Skolemised type variables for the
-- enclosing class/instance decl.
-- They'll be signature tyvars, and we
-- want to check that they don't get bound
-- Also they are scoped, so we bring them into scope
-- Always equal the range of the type envt
-> TcThetaType -- Available theta; it's just used for the error message
- -> [Inst] -- Available from context, used to simplify constraints
- -- from the method body
+ -> Inst -- Current dictionary (this_dict)
+ -> [Inst] -- Other stuff available from context, used to simplify
+ -- constraints from the method body (exclude this_dict)
-> TcSigFun -- For scoped tyvars, indexed by sel_name
-> TcPragFun -- Pragmas (e.g. inline pragmas), indexed by sel_name
- -> MethodSpec -- Details of this method
+ -> LHsBinds Name -- Method binding (pick the right one from in here)
+ -> ClassOpItem
+ -> TcId -- The method Id
-> TcM (LHsBinds Id)
-tcMethodBind inst_tyvars inst_theta avail_insts sig_fn prag_fn
- (sel_id, meth_id, meth_bind)
- = recoverM (returnM emptyLHsBinds) $
+tcMethodBind origin inst_tyvars inst_theta
+ this_dict extra_insts
+ sig_fn prag_fn meth_binds
+ (sel_id, dm_info) meth_id
+ | Just user_bind <- find_bind sel_name meth_name meth_binds
+ = -- If there is a user-supplied method binding, typecheck it
+ tc_method_bind inst_tyvars inst_theta (this_dict:extra_insts)
+ sig_fn prag_fn
+ sel_id meth_id user_bind
+
+ | otherwise -- The user didn't supply a method binding, so we have to make
+ -- up a default binding, in a way depending on the default-method info
+ = case dm_info of
+ NoDefMeth -> do { warn <- doptM Opt_WarnMissingMethods
+ ; warnTc (isInstDecl origin
+ && warn -- Warn only if -fwarn-missing-methods
+ && reportIfUnused (getOccName sel_id))
+ -- Don't warn about _foo methods
+ (omittedMethodWarn sel_id)
+ ; return (unitBag $ L loc (VarBind meth_id error_rhs)) }
+
+ DefMeth -> do { -- An polymorphic default method
+ -- Might not be imported, but will be an OrigName
+ dm_name <- lookupImportedName (mkDefMethRdrName sel_id)
+ ; dm_id <- tcLookupId dm_name
+ -- Note [Default methods in instances]
+ ; return (unitBag $ L loc (VarBind meth_id (mk_dm_app dm_id))) }
+
+ GenDefMeth -> ASSERT( isInstDecl origin ) -- We never get here from a class decl
+ do { meth_bind <- mkGenericDefMethBind clas inst_tys sel_id meth_name
+ ; tc_method_bind inst_tyvars inst_theta (this_dict:extra_insts)
+ sig_fn prag_fn
+ sel_id meth_id meth_bind }
+
+ where
+ meth_name = idName meth_id
+ sel_name = idName sel_id
+ loc = getSrcSpan meth_id
+ (clas, inst_tys) = getDictClassTys this_dict
+
+ this_dict_id = instToId this_dict
+ error_id = L loc (HsVar nO_METHOD_BINDING_ERROR_ID)
+ error_id_app = mkLHsWrap (WpTyApp (idType meth_id)) error_id
+ error_rhs = mkHsApp error_id_app $ L loc $
+ HsLit (HsStringPrim (mkFastString error_msg))
+ error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
+
+ mk_dm_app dm_id -- dm tys inst_dict
+ = mkLHsWrap (WpApp this_dict_id `WpCompose` mkWpTyApps inst_tys)
+ (L loc (HsVar dm_id))
+
+
+---------------------------
+tc_method_bind :: [TyVar] -> TcThetaType -> [Inst] -> (Name -> Maybe [Name])
+ -> (Name -> [LSig Name]) -> Id -> Id -> LHsBind Name
+ -> TcRn (LHsBindsLR Id Var)
+tc_method_bind inst_tyvars inst_theta avail_insts sig_fn prag_fn
+ sel_id meth_id meth_bind
+ = recoverM (return emptyLHsBinds) $
-- If anything fails, recover returning no bindings.
-- This is particularly useful when checking the default-method binding of
-- a class decl. If we don't recover, we don't add the default method to
-- Check the bindings; first adding inst_tyvars to the envt
-- so that we don't quantify over them in nested places
-
- let sel_name = idName sel_id
- meth_sig_fn meth_name = ASSERT( meth_name == idName meth_id ) sig_fn sel_name
- -- The meth_bind metions the meth_name, but sig_fn is indexed by sel_name
- in
- tcExtendTyVarEnv inst_tyvars (
- tcExtendIdEnv [meth_id] $ -- In scope for tcInstSig
- addErrCtxt (methodCtxt sel_id) $
- getLIE $
- tcMonoBinds [meth_bind] meth_sig_fn Recursive
- ) `thenM` \ ((meth_bind, mono_bind_infos), meth_lie) ->
-
- -- Now do context reduction. We simplify wrt both the local tyvars
- -- and the ones of the class/instance decl, so that there is
- -- no problem with
- -- class C a where
- -- op :: Eq a => a -> b -> a
- --
- -- We do this for each method independently to localise error messages
-
- let
- [(_, Just sig, local_meth_id)] = mono_bind_infos
- loc = sig_loc sig
- in
- addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $
- newDictBndrs loc (sig_theta sig) `thenM` \ meth_dicts ->
- let
- meth_tvs = sig_tvs sig
- all_tyvars = meth_tvs ++ inst_tyvars
- all_insts = avail_insts ++ meth_dicts
- in
- tcSimplifyCheck
- loc all_tyvars all_insts meth_lie `thenM` \ lie_binds ->
-
- checkSigTyVars all_tyvars `thenM_`
-
- tcPrags meth_id (prag_fn sel_name) `thenM` \ prags ->
- let
- poly_meth_bind = noLoc $ AbsBinds meth_tvs
+ do { let sel_name = idName sel_id
+ meth_name = idName meth_id
+ meth_sig_fn name = ASSERT( name == meth_name ) sig_fn sel_name
+ -- The meth_bind metions the meth_name, but sig_fn is indexed by sel_name
+
+ ; ((meth_bind, mono_bind_infos), meth_lie)
+ <- tcExtendTyVarEnv inst_tyvars $
+ tcExtendIdEnv [meth_id] $ -- In scope for tcInstSig
+ addErrCtxt (methodCtxt sel_id) $
+ getLIE $
+ tcMonoBinds [meth_bind] meth_sig_fn Recursive
+
+ -- Now do context reduction. We simplify wrt both the local tyvars
+ -- and the ones of the class/instance decl, so that there is
+ -- no problem with
+ -- class C a where
+ -- op :: Eq a => a -> b -> a
+ --
+ -- We do this for each method independently to localise error messages
+
+ ; let [(_, Just sig, local_meth_id)] = mono_bind_infos
+ loc = sig_loc sig
+
+ ; addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $ do
+ { meth_dicts <- newDictBndrs loc (sig_theta sig)
+ ; let meth_tvs = sig_tvs sig
+ all_tyvars = meth_tvs ++ inst_tyvars
+ all_insts = avail_insts ++ meth_dicts
+
+ ; lie_binds <- tcSimplifyCheck loc all_tyvars all_insts meth_lie
+
+ ; checkSigTyVars all_tyvars
+
+ ; prags <- tcPrags meth_id (prag_fn sel_name)
+ ; let poly_meth_bind = noLoc $ AbsBinds meth_tvs
(map instToId meth_dicts)
[(meth_tvs, meth_id, local_meth_id, prags)]
(lie_binds `unionBags` meth_bind)
- in
- returnM (unitBag poly_meth_bind)
+ ; return (unitBag poly_meth_bind) }}
-mkMethodBind :: InstOrigin
- -> Class -> [TcType] -- Class and instance types
- -> LHsBinds Name -- Method binding (pick the right one from in here)
- -> ClassOpItem
- -> TcM (Maybe Inst, -- Method inst
- MethodSpec)
--- Find the binding for the specified method, or make
--- up a suitable default method if it isn't there
-mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info)
- = mkMethId origin clas sel_id inst_tys `thenM` \ (mb_inst, meth_id) ->
- let
- meth_name = idName meth_id
- in
- -- Figure out what method binding to use
- -- If the user suppplied one, use it, else construct a default one
- getSrcSpanM `thenM` \ loc ->
- (case find_bind (idName sel_id) meth_name meth_binds of
- Just user_bind -> returnM user_bind
- Nothing ->
- mkDefMethRhs origin clas inst_tys sel_id loc dm_info `thenM` \ rhs ->
- -- Not infix decl
- returnM (noLoc $ mkFunBind (noLoc meth_name) [mkSimpleMatch [] rhs])
- ) `thenM` \ meth_bind ->
-
- returnM (mb_inst, (sel_id, meth_id, meth_bind))
-
-mkMethId :: InstOrigin -> Class
+---------------------------
+mkMethId :: InstOrigin -> Class
-> Id -> [TcType] -- Selector, and instance types
-> TcM (Maybe Inst, Id)
rho_ty = ASSERT( length tyvars == length inst_tys )
substTyWith tyvars inst_tys rho
(preds,tau) = tcSplitPhiTy rho_ty
- first_pred = head preds
+ first_pred = ASSERT( not (null preds)) head preds
in
-- The first predicate should be of form (C a b)
-- where C is the class in question
ASSERT( not (null preds) &&
case getClassPredTys_maybe first_pred of
- { Just (clas1,tys) -> clas == clas1 ; Nothing -> False }
+ { Just (clas1, _tys) -> clas == clas1 ; Nothing -> False }
)
- if isSingleton preds then
+ if isSingleton preds then do
-- If it's the only one, make a 'method'
- getInstLoc origin `thenM` \ inst_loc ->
- newMethod inst_loc sel_id inst_tys `thenM` \ meth_inst ->
- returnM (Just meth_inst, instToId meth_inst)
- else
+ inst_loc <- getInstLoc origin
+ meth_inst <- newMethod inst_loc sel_id inst_tys
+ return (Just meth_inst, instToId meth_inst)
+ else do
-- If it's not the only one we need to be careful
-- For example, given 'op' defined thus:
-- class Foo a where
-- That is, the class-op's context is still there.
-- BUT: it can't be a Method any more, because it breaks
-- INVARIANT 2 of methods. (See the data decl for Inst.)
- newUnique `thenM` \ uniq ->
- getSrcSpanM `thenM` \ loc ->
+ uniq <- newUnique
+ loc <- getSrcSpanM
let
real_tau = mkPhiTy (tail preds) tau
meth_id = mkUserLocal (getOccName sel_id) uniq real_tau loc
- in
- returnM (Nothing, meth_id)
-
- -- The user didn't supply a method binding,
- -- so we have to make up a default binding
- -- The RHS of a default method depends on the default-method info
-mkDefMethRhs origin clas inst_tys sel_id loc DefMeth
- = -- An polymorphic default method
- lookupImportedName (mkDefMethRdrName sel_id) `thenM` \ dm_name ->
- -- Might not be imported, but will be an OrigName
- traceRn (text "mkDefMeth" <+> ppr dm_name) `thenM_`
- returnM (nlHsVar dm_name)
-
-mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth
- = -- No default method
- -- Warn only if -fwarn-missing-methods
- doptM Opt_WarnMissingMethods `thenM` \ warn ->
- warnTc (isInstDecl origin
- && warn
- && reportIfUnused (getOccName sel_id))
- (omittedMethodWarn sel_id) `thenM_`
- returnM error_rhs
- where
- error_rhs = noLoc $ HsLam (mkMatchGroup [mkSimpleMatch wild_pats simple_rhs])
- simple_rhs = nlHsApp (nlHsVar (getName nO_METHOD_BINDING_ERROR_ID))
- (nlHsLit (HsStringPrim (mkFastString error_msg)))
- error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
-
- -- When the type is of form t1 -> t2 -> t3
- -- make a default method like (\ _ _ -> noMethBind "blah")
- -- rather than simply (noMethBind "blah")
- -- Reason: if t1 or t2 are higher-ranked types we get n
- -- silly ambiguity messages.
- -- Example: f :: (forall a. Eq a => a -> a) -> Int
- -- f = error "urk"
- -- Here, tcSub tries to force (error "urk") to have the right type,
- -- thus: f = \(x::forall a. Eq a => a->a) -> error "urk" (x t)
- -- where 't' is fresh ty var. This leads directly to "ambiguous t".
- --
- -- NB: technically this changes the meaning of the default-default
- -- method slightly, because `seq` can see the lambdas. Oh well.
- (_,_,tau1) = tcSplitSigmaTy (idType sel_id)
- (_,_,tau2) = tcSplitSigmaTy tau1
- -- Need two splits because the selector can have a type like
- -- forall a. Foo a => forall b. Eq b => ...
- (arg_tys, _) = tcSplitFunTys tau2
- wild_pats = [nlWildPat | ty <- arg_tys]
-
-mkDefMethRhs origin clas inst_tys sel_id loc GenDefMeth
+
+ return (Nothing, meth_id)
+
+---------------------------
+-- The renamer just puts the selector ID as the binder in the method binding
+-- but we must use the method name; so we substitute it here. Crude but simple.
+find_bind :: Name -> Name -- Selector and method name
+ -> LHsBinds Name -- A group of bindings
+ -> Maybe (LHsBind Name) -- The binding, with meth_name replacing sel_name
+find_bind sel_name meth_name binds
+ = foldlBag mplus Nothing (mapBag f binds)
+ where
+ f (L loc1 bind@(FunBind { fun_id = L loc2 op_name })) | op_name == sel_name
+ = Just (L loc1 (bind { fun_id = L loc2 meth_name }))
+ f _other = Nothing
+
+---------------------------
+mkGenericDefMethBind :: Class -> [Type] -> Id -> Name -> TcM (LHsBind Name)
+mkGenericDefMethBind clas inst_tys sel_id meth_name
= -- A generic default method
-- If the method is defined generically, we can only do the job if the
-- instance declaration is for a single-parameter type class with
-- a type constructor applied to type arguments in the instance decl
-- (checkTc, so False provokes the error)
- ASSERT( isInstDecl origin ) -- We never get here from a class decl
do { checkTc (isJust maybe_tycon)
(badGenericInstance sel_id (notSimple inst_tys))
; checkTc (tyConHasGenerics tycon)
(badGenericInstance sel_id (notGeneric tycon))
; dflags <- getDOpts
- ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Filling in method body"
+ ; liftIO (dumpIfSet_dyn dflags Opt_D_dump_deriv "Filling in method body"
(vcat [ppr clas <+> ppr inst_tys,
nest 2 (ppr sel_id <+> equals <+> ppr rhs)]))
-- Rename it before returning it
; (rn_rhs, _) <- rnLExpr rhs
- ; returnM rn_rhs }
+ ; return (noLoc $ mkFunBind (noLoc meth_name) [mkSimpleMatch [] rn_rhs]) }
where
rhs = mkGenericRhs sel_id clas_tyvar tycon
-- case we require that the instance decl is for a single-parameter
-- type class with type variable arguments:
-- instance (...) => C (T a b)
- clas_tyvar = head (classTyVars clas)
- Just tycon = maybe_tycon
- maybe_tycon = case inst_tys of
+ clas_tyvar = ASSERT (not (null (classTyVars clas))) head (classTyVars clas)
+ Just tycon = maybe_tycon
+ maybe_tycon = case inst_tys of
[ty] -> case tcSplitTyConApp_maybe ty of
Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon
- other -> Nothing
- other -> Nothing
+ _ -> Nothing
+ _ -> Nothing
+isInstDecl :: InstOrigin -> Bool
isInstDecl (SigOrigin InstSkol) = True
isInstDecl (SigOrigin (ClsSkol _)) = False
+isInstDecl o = pprPanic "isInstDecl" (ppr o)
\end{code}
-\begin{code}
--- The renamer just puts the selector ID as the binder in the method binding
--- but we must use the method name; so we substitute it here. Crude but simple.
-find_bind sel_name meth_name binds
- = foldlBag seqMaybe Nothing (mapBag f binds)
- where
- f (L loc1 bind@(FunBind { fun_id = L loc2 op_name })) | op_name == sel_name
- = Just (L loc1 (bind { fun_id = L loc2 meth_name }))
- f _other = Nothing
-\end{code}
+Note [Default methods]
+~~~~~~~~~~~~~~~~~~~~~~~
+The default methods for a class are each passed a dictionary for the
+class, so that they get access to the other methods at the same type.
+So, given the class decl
+
+ class Foo a where
+ op1 :: a -> Bool
+ op2 :: forall b. Ord b => a -> b -> b -> b
+
+ op1 x = True
+ op2 x y z = if (op1 x) && (y < z) then y else z
+
+we get the default methods:
+
+ $dmop1 :: forall a. Foo a => a -> Bool
+ $dmop1 = /\a -> \dfoo -> \x -> True
+
+ $dmop2 :: forall a. Foo a => forall b. Ord b => a -> b -> b -> b
+ $dmop2 = /\ a -> \ dfoo -> /\ b -> \ dord -> \x y z ->
+ if (op1 a dfoo x) && (< b dord y z) then y else z
+
+When we come across an instance decl, we may need to use the default methods:
+
+ instance Foo Int where {}
+
+ $dFooInt :: Foo Int
+ $dFooInt = MkFoo ($dmop1 Int $dFooInt)
+ ($dmop2 Int $dFooInt)
+
+Notice that, as with method selectors above, we assume that dictionary
+application is curried, so there's no need to mention the Ord dictionary
+in the application of $dmop2.
+
+ instance Foo a => Foo [a] where {}
+
+ $dFooList :: forall a. Foo a -> Foo [a]
+ $dFooList = /\ a -> \ dfoo_a ->
+ let rec
+ op1 = defm.Foo.op1 [a] dfoo_list
+ op2 = defm.Foo.op2 [a] dfoo_list
+ dfoo_list = MkFoo ($dmop1 [a] dfoo_list)
+ ($dmop2 [a] dfoo_list)
+ in
+ dfoo_list
+
+Note [Default methods in instances]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider this
+
+ class Baz v x where
+ foo :: x -> x
+ foo y = y
+
+ instance Baz Int Int
+
+From the class decl we get
+
+ $dmfoo :: forall v x. Baz v x => x -> x
+
+Notice that the type is ambiguous. That's fine, though. The instance decl generates
+
+ $dBazIntInt = MkBaz ($dmfoo Int Int $dBazIntInt)
+
+BUT this does mean we must generate the dictionary translation directly, rather
+than generating source-code and type-checking it. That was the bug ing
+Trac #1061. In any case it's less work to generate the translated version!
%************************************************************************
\begin{code}
-getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo]
+getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo Name]
getGenericInstances class_decls
- = do { gen_inst_infos <- mappM (addLocM get_generics) class_decls
+ = do { gen_inst_infos <- mapM (addLocM get_generics) class_decls
; let { gen_inst_info = concat gen_inst_infos }
-- Return right away if there is no generic stuff
- ; if null gen_inst_info then returnM []
+ ; if null gen_inst_info then return []
else do
-- Otherwise print it out
{ dflags <- getDOpts
- ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances"
- (vcat (map pprInstInfoDetails gen_inst_info)))
- ; returnM gen_inst_info }}
+ ; liftIO (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances"
+ (vcat (map pprInstInfoDetails gen_inst_info)))
+ ; return gen_inst_info }}
+get_generics :: TyClDecl Name -> TcM [InstInfo Name]
get_generics decl@(ClassDecl {tcdLName = class_name, tcdMeths = def_methods})
| null generic_binds
- = returnM [] -- The comon case: no generic default methods
+ = return [] -- The comon case: no generic default methods
| otherwise -- A source class decl with generic default methods
- = recoverM (returnM []) $
- tcAddDeclCtxt decl $
- tcLookupLocatedClass class_name `thenM` \ clas ->
+ = recoverM (return []) $
+ tcAddDeclCtxt decl $ do
+ clas <- tcLookupLocatedClass class_name
-- Group by type, and
-- make an InstInfo out of each group
let
groups = groupWith listToBag generic_binds
- in
- mappM (mkGenericInstance clas) groups `thenM` \ inst_infos ->
+
+ inst_infos <- mapM (mkGenericInstance clas) groups
-- Check that there is only one InstInfo for each type constructor
-- The main way this can fail is if you write
--
-- The class should be unary, which is why simpleInstInfoTyCon should be ok
let
- tc_inst_infos :: [(TyCon, InstInfo)]
+ tc_inst_infos :: [(TyCon, InstInfo Name)]
tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos]
bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos,
group `lengthExceeds` 1]
get_uniq (tc,_) = getUnique tc
- in
- mappM (addErrTc . dupGenericInsts) bad_groups `thenM_`
+
+ mapM (addErrTc . dupGenericInsts) bad_groups
-- Check that there is an InstInfo for each generic type constructor
let
missing = genericTyConNames `minusList` [tyConName tc | (tc,_) <- tc_inst_infos]
- in
- checkTc (null missing) (missingGenericInstances missing) `thenM_`
- returnM inst_infos
+ checkTc (null missing) (missingGenericInstances missing)
+
+ return inst_infos
where
generic_binds :: [(HsType Name, LHsBind Name)]
generic_binds = getGenericBinds def_methods
+get_generics decl = pprPanic "get_generics" (ppr decl)
---------------------------------
-- them in finite map indexed by the type parameter in the definition.
getGenericBinds binds = concat (map getGenericBind (bagToList binds))
+getGenericBind :: LHsBindLR Name Name -> [(HsType Name, LHsBindLR Name Name)]
getGenericBind (L loc bind@(FunBind { fun_matches = MatchGroup matches ty }))
= groupWith wrap (mapCatMaybes maybeGenericMatch matches)
where
= []
groupWith :: ([a] -> b) -> [(HsType Name, a)] -> [(HsType Name, b)]
-groupWith op [] = []
+groupWith _ [] = []
groupWith op ((t,v):prs) = (t, op (v:vs)) : groupWith op rest
where
- vs = map snd this
- (this,rest) = partition same_t prs
- same_t (t',v) = t `eqPatType` t'
+ vs = map snd this
+ (this,rest) = partition same_t prs
+ same_t (t', _v) = t `eqPatType` t'
eqPatLType :: LHsType Name -> LHsType Name -> Bool
eqPatLType t1 t2 = unLoc t1 `eqPatType` unLoc t2
-- A very simple equality function, only for
-- type patterns in generic function definitions.
eqPatType (HsTyVar v1) (HsTyVar v2) = v1==v2
-eqPatType (HsAppTy s1 t1) (HsAppTy s2 t2) = s1 `eqPatLType` s2 && t2 `eqPatLType` t2
-eqPatType (HsOpTy s1 op1 t1) (HsOpTy s2 op2 t2) = s1 `eqPatLType` s2 && t2 `eqPatLType` t2 && unLoc op1 == unLoc op2
+eqPatType (HsAppTy s1 t1) (HsAppTy s2 t2) = s1 `eqPatLType` s2 && t1 `eqPatLType` t2
+eqPatType (HsOpTy s1 op1 t1) (HsOpTy s2 op2 t2) = s1 `eqPatLType` s2 && t1 `eqPatLType` t2 && unLoc op1 == unLoc op2
eqPatType (HsNumTy n1) (HsNumTy n2) = n1 == n2
eqPatType (HsParTy t1) t2 = unLoc t1 `eqPatType` t2
eqPatType t1 (HsParTy t2) = t1 `eqPatType` unLoc t2
---------------------------------
mkGenericInstance :: Class
-> (HsType Name, LHsBinds Name)
- -> TcM InstInfo
+ -> TcM (InstInfo Name)
-mkGenericInstance clas (hs_ty, binds)
+mkGenericInstance clas (hs_ty, binds) = do
-- Make a generic instance declaration
-- For example: instance (C a, C b) => C (a+b) where { binds }
- = -- Extract the universally quantified type variables
+ -- Extract the universally quantified type variables
-- and wrap them as forall'd tyvars, so that kind inference
-- works in the standard way
let
sig_tvs = map (noLoc.UserTyVar) (nameSetToList (extractHsTyVars (noLoc hs_ty)))
hs_forall_ty = noLoc $ mkExplicitHsForAllTy sig_tvs (noLoc []) (noLoc hs_ty)
- in
+
-- Type-check the instance type, and check its form
- tcHsSigType GenPatCtxt hs_forall_ty `thenM` \ forall_inst_ty ->
+ forall_inst_ty <- tcHsSigType GenPatCtxt hs_forall_ty
let
(tyvars, inst_ty) = tcSplitForAllTys forall_inst_ty
- in
+
checkTc (validGenericInstanceType inst_ty)
- (badGenericInstanceType binds) `thenM_`
+ (badGenericInstanceType binds)
-- Make the dictionary function.
- getSrcSpanM `thenM` \ span ->
- getOverlapFlag `thenM` \ overlap_flag ->
- newDFunName clas [inst_ty] span `thenM` \ dfun_name ->
+ span <- getSrcSpanM
+ overlap_flag <- getOverlapFlag
+ dfun_name <- newDFunName clas [inst_ty] span
let
inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars]
dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty]
ispec = mkLocalInstance dfun_id overlap_flag
- in
- returnM (InstInfo { iSpec = ispec, iBinds = VanillaInst binds [] })
+
+ return (InstInfo { iSpec = ispec, iBinds = VanillaInst binds [] })
\end{code}
%************************************************************************
\begin{code}
+tcAddDeclCtxt :: TyClDecl Name -> TcM a -> TcM a
tcAddDeclCtxt decl thing_inside
= addErrCtxt ctxt thing_inside
where
then "newtype" ++ maybeInst
else "data type" ++ maybeInst
| isFamilyDecl decl = "family"
+ | otherwise = panic "tcAddDeclCtxt/thing"
- maybeInst | isFamInstDecl decl = " family"
+ maybeInst | isFamInstDecl decl = " instance"
| otherwise = ""
- ctxt = hsep [ptext SLIT("In the"), text thing,
- ptext SLIT("declaration for"), quotes (ppr (tcdName decl))]
+ ctxt = hsep [ptext (sLit "In the"), text thing,
+ ptext (sLit "declaration for"), quotes (ppr (tcdName decl))]
+defltMethCtxt :: Class -> SDoc
defltMethCtxt clas
- = ptext SLIT("When checking the default methods for class") <+> quotes (ppr clas)
+ = ptext (sLit "When checking the default methods for class") <+> quotes (ppr clas)
+methodCtxt :: Var -> SDoc
methodCtxt sel_id
- = ptext SLIT("In the definition for method") <+> quotes (ppr sel_id)
+ = ptext (sLit "In the definition for method") <+> quotes (ppr sel_id)
+badMethodErr :: Outputable a => a -> Name -> SDoc
badMethodErr clas op
- = hsep [ptext SLIT("Class"), quotes (ppr clas),
- ptext SLIT("does not have a method"), quotes (ppr op)]
+ = hsep [ptext (sLit "Class"), quotes (ppr clas),
+ ptext (sLit "does not have a method"), quotes (ppr op)]
+badATErr :: Class -> Name -> SDoc
badATErr clas at
- = hsep [ptext SLIT("Class"), quotes (ppr clas),
- ptext SLIT("does not have an associated type"), quotes (ppr at)]
+ = hsep [ptext (sLit "Class"), quotes (ppr clas),
+ ptext (sLit "does not have an associated type"), quotes (ppr at)]
+omittedMethodWarn :: Id -> SDoc
omittedMethodWarn sel_id
- = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id)
+ = ptext (sLit "No explicit method nor default method for") <+> quotes (ppr sel_id)
+omittedATWarn :: Name -> SDoc
omittedATWarn at
- = ptext SLIT("No explicit AT declaration for") <+> quotes (ppr at)
+ = ptext (sLit "No explicit AT declaration for") <+> quotes (ppr at)
+badGenericInstance :: Var -> SDoc -> SDoc
badGenericInstance sel_id because
- = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id),
+ = sep [ptext (sLit "Can't derive generic code for") <+> quotes (ppr sel_id),
because]
+notSimple :: [Type] -> SDoc
notSimple inst_tys
- = vcat [ptext SLIT("because the instance type(s)"),
+ = vcat [ptext (sLit "because the instance type(s)"),
nest 2 (ppr inst_tys),
- ptext SLIT("is not a simple type of form (T a1 ... an)")]
+ ptext (sLit "is not a simple type of form (T a1 ... an)")]
+notGeneric :: TyCon -> SDoc
notGeneric tycon
- = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+>
- ptext SLIT("was not compiled with -fgenerics")]
+ = vcat [ptext (sLit "because the instance type constructor") <+> quotes (ppr tycon) <+>
+ ptext (sLit "was not compiled with -XGenerics")]
+badGenericInstanceType :: LHsBinds Name -> SDoc
badGenericInstanceType binds
- = vcat [ptext SLIT("Illegal type pattern in the generic bindings"),
+ = vcat [ptext (sLit "Illegal type pattern in the generic bindings"),
nest 4 (ppr binds)]
+missingGenericInstances :: [Name] -> SDoc
missingGenericInstances missing
- = ptext SLIT("Missing type patterns for") <+> pprQuotedList missing
+ = ptext (sLit "Missing type patterns for") <+> pprQuotedList missing
+dupGenericInsts :: [(TyCon, InstInfo a)] -> SDoc
dupGenericInsts tc_inst_infos
- = vcat [ptext SLIT("More than one type pattern for a single generic type constructor:"),
+ = vcat [ptext (sLit "More than one type pattern for a single generic type constructor:"),
nest 4 (vcat (map ppr_inst_ty tc_inst_infos)),
- ptext SLIT("All the type patterns for a generic type constructor must be identical")
+ ptext (sLit "All the type patterns for a generic type constructor must be identical")
]
where
ppr_inst_ty (_,inst) = ppr (simpleInstInfoTy inst)
+mixedGenericErr :: Name -> SDoc
mixedGenericErr op
- = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op)
+ = ptext (sLit "Can't mix generic and non-generic equations for class method") <+> quotes (ppr op)
\end{code}
projects / ghc-hetmet.git / blobdiff