Typechecking class declarations
\begin{code}
-{-# OPTIONS -w #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
--- for details
-
module TcClassDcl ( tcClassSigs, tcClassDecl2,
- getGenericInstances,
- MethodSpec, tcMethodBind, mkMethId,
+ findMethodBind, tcInstanceMethodBody,
+ mkGenericDefMethBind, getGenericInstances, mkDefMethRdrName,
tcAddDeclCtxt, badMethodErr, badATErr, omittedATWarn
) where
import InstEnv
import TcEnv
import TcBinds
-import TcHsType
import TcSimplify
-import TcUnify
+import TcHsType
import TcMType
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
; 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)
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;
Just False -> DefMeth
Just True -> GenDefMeth
; return (op_name, dm, op_ty) }
+tcClassSig _ s = pprPanic "tcClassSig" (ppr s)
\end{code}
tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs,
tcdMeths = default_binds}))
= recoverM (return (emptyLHsBinds, [])) $
- setSrcSpan loc $ do
- clas <- tcLookupLocatedClass class_name
+ 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
-- dm1 = \d -> case ds d of (a,b,c) -> a
-- And since ds is big, it doesn't get inlined, so we don't get good
-- default methods. Better to make separate AbsBinds for each
- let
- (tyvars, _, _, op_items) = classBigSig clas
- rigid_info = ClsSkol clas
- origin = SigOrigin rigid_info
- prag_fn = mkPragFun sigs
- sig_fn = mkTcSigFun sigs
- clas_tyvars = tcSkolSigTyVars rigid_info tyvars
- tc_dm = tcDefMeth origin clas clas_tyvars
- default_binds sig_fn prag_fn
-
- dm_sel_ids = [sel_id | (sel_id, DefMeth) <- op_items]
- -- Generate code for polymorphic default methods only
- -- (Generic default methods have turned into instance decls by now.)
- -- This is incompatible with Hugs, which expects a polymorphic
- -- 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.)
-
- (defm_binds, dm_ids_s) <- mapAndUnzipM tc_dm dm_sel_ids
- return (listToBag defm_binds, concat dm_ids_s)
-
-tcDefMeth origin clas tyvars binds_in sig_fn prag_fn sel_id
- = do { dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_id)
- ; let inst_tys = mkTyVarTys tyvars
- dm_ty = idType sel_id -- Same as dict selector!
- cls_pred = mkClassPred clas inst_tys
- local_dm_id = mkDefaultMethodId dm_name dm_ty
-
- ; loc <- getInstLoc origin
- ; this_dict <- newDictBndr loc cls_pred
- ; (_, 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
-
- -- Check the context
- { dict_binds <- tcSimplifyCheck
- loc
- tyvars
- [this_dict]
- insts_needed
-
- -- Simplification can do unification
- ; checkSigTyVars tyvars
+ ; let
+ (tyvars, _, _, op_items) = classBigSig clas
+ rigid_info = ClsSkol clas
+ prag_fn = mkPragFun sigs
+ sig_fn = mkTcSigFun sigs
+ clas_tyvars = tcSkolSigTyVars rigid_info tyvars
+ pred = mkClassPred clas (mkTyVarTys clas_tyvars)
+ ; inst_loc <- getInstLoc (SigOrigin rigid_info)
+ ; this_dict <- newDictBndr inst_loc pred
+
+ ; let tc_dm = tcDefMeth rigid_info clas clas_tyvars [pred]
+ this_dict default_binds
+ sig_fn prag_fn
+ -- tc_dm is called only for a sel_id
+ -- that has a binding in default_binds
+
+ dm_sel_ids = [sel_id | (sel_id, DefMeth) <- op_items]
+ -- Generate code for polymorphic default methods only (hence DefMeth)
+ -- (Generic default methods have turned into instance decls by now.)
+ -- This is incompatible with Hugs, which expects a polymorphic
+ -- 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.)
+
+ ; (defm_binds, dm_ids) <- tcExtendTyVarEnv clas_tyvars $
+ mapAndUnzipM tc_dm dm_sel_ids
+
+ ; return (unionManyBags defm_binds, dm_ids) }
+
+tcClassDecl2 d = pprPanic "tcClassDecl2" (ppr d)
- -- Inline pragmas
- -- 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 sel_name = idName sel_id
- inline_prags = filter isInlineLSig (prag_fn sel_name)
- ; prags <- tcPrags meth_id inline_prags
-
- ; let full_bind = AbsBinds tyvars
- [instToId this_dict]
- [(tyvars, local_dm_id, meth_id, prags)]
- (dict_binds `unionBags` defm_bind)
- ; return (noLoc full_bind, [local_dm_id]) }}
-
-mkDefMethRdrName :: Id -> RdrName
-mkDefMethRdrName sel_id = mkDerivedRdrName (idName sel_id) mkDefaultMethodOcc
-\end{code}
+tcDefMeth :: SkolemInfo -> Class -> [TyVar] -> ThetaType -> Inst -> LHsBinds Name
+ -> TcSigFun -> TcPragFun -> Id
+ -> TcM (LHsBinds Id, Id)
+tcDefMeth rigid_info clas tyvars theta this_dict binds_in sig_fn prag_fn sel_id
+ = do { let sel_name = idName sel_id
+ ; local_dm_name <- newLocalName sel_name
+ ; let meth_bind = findMethodBind sel_name local_dm_name binds_in
+ `orElse` pprPanic "tcDefMeth" (ppr sel_id)
+ -- We only call tcDefMeth on selectors for which
+ -- there is a binding in binds_in
+
+ meth_sig_fn _ = sig_fn sel_name
+ meth_prag_fn _ = prag_fn sel_name
+
+ ; (top_dm_id, bind) <- tcInstanceMethodBody rigid_info
+ clas tyvars [this_dict] theta (mkTyVarTys tyvars)
+ Nothing sel_id
+ local_dm_name
+ meth_sig_fn meth_prag_fn
+ meth_bind
+
+ ; return (bind, top_dm_id) }
+
+mkDefMethRdrName :: Name -> RdrName
+mkDefMethRdrName sel_name = mkDerivedRdrName sel_name mkDefaultMethodOcc
+---------------------------
+-- 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.
+findMethodBind :: Name -> Name -- Selector and method name
+ -> LHsBinds Name -- A group of bindings
+ -> Maybe (LHsBind Name) -- The binding, with meth_name replacing sel_name
+findMethodBind 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
-%************************************************************************
-%* *
-\subsection{Typechecking a method}
-%* *
-%************************************************************************
+---------------
+tcInstanceMethodBody :: SkolemInfo -> Class -> [TcTyVar] -> [Inst]
+ -> TcThetaType -> [TcType]
+ -> Maybe (Inst, LHsBind Id) -> Id
+ -> Name -- The local method name
+ -> TcSigFun -> TcPragFun -> LHsBind Name
+ -> TcM (Id, LHsBinds Id)
+tcInstanceMethodBody rigid_info clas tyvars dfun_dicts theta inst_tys
+ mb_this_bind sel_id local_meth_name
+ sig_fn prag_fn bind@(L loc _)
+ = do { let (sel_tyvars,sel_rho) = tcSplitForAllTys (idType sel_id)
+ rho_ty = ASSERT( length sel_tyvars == length inst_tys )
+ substTyWith sel_tyvars inst_tys sel_rho
+
+ (first_pred, local_meth_ty) = tcSplitPredFunTy_maybe rho_ty
+ `orElse` pprPanic "tcInstanceMethod" (ppr sel_id)
+
+ local_meth_id = mkLocalId local_meth_name local_meth_ty
+ meth_ty = mkSigmaTy tyvars theta local_meth_ty
+ sel_name = idName sel_id
+
+ -- The first predicate should be of form (C a b)
+ -- where C is the class in question
+ ; MASSERT( case getClassPredTys_maybe first_pred of
+ { Just (clas1, _tys) -> clas == clas1 ; Nothing -> False } )
+
+ -- Typecheck the binding, first extending the envt
+ -- so that when tcInstSig looks up the local_meth_id to find
+ -- its signature, we'll find it in the environment
+ ; ((tc_bind, _), lie) <- getLIE $
+ tcExtendIdEnv [local_meth_id] $
+ tcPolyBinds TopLevel sig_fn prag_fn
+ NonRecursive NonRecursive
+ (unitBag bind)
+
+ ; meth_id <- case rigid_info of
+ ClsSkol _ -> do { dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_name)
+ ; return (mkDefaultMethodId dm_name meth_ty) }
+ _other -> do { meth_name <- newLocalName sel_name
+ ; return (mkLocalId meth_name meth_ty) }
+
+ ; let (avails, this_dict_bind)
+ = case mb_this_bind of
+ Nothing -> (dfun_dicts, emptyBag)
+ Just (this, bind) -> (this : dfun_dicts, unitBag bind)
+
+ ; inst_loc <- getInstLoc (SigOrigin rigid_info)
+ ; lie_binds <- tcSimplifyCheck inst_loc tyvars avails lie
+
+ ; let full_bind = L loc $
+ AbsBinds tyvars dfun_lam_vars
+ [(tyvars, meth_id, local_meth_id, [])]
+ (this_dict_bind `unionBags` lie_binds
+ `unionBags` tc_bind)
+
+ dfun_lam_vars = map instToVar dfun_dicts -- Includes equalities
+
+ ; return (meth_id, unitBag full_bind) }
+\end{code}
-@tcMethodBind@ is used to type-check both default-method and
-instance-decl method declarations. We must type-check methods one at a
-time, because their signatures may have different contexts and
-tyvar sets.
+Note [Polymorphic methods]
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+ class Foo a where
+ op :: forall b. Ord b => a -> b -> b -> b
+ instance Foo c => Foo [c] where
+ op = e
-\begin{code}
-type MethodSpec = (Id, -- Global selector Id
- Id, -- Local Id (class tyvars instantiated)
- LHsBind Name) -- Binding for the method
-
-tcMethodBind
- :: 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 -- 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
- -> LHsBinds Name -- Method binding (pick the right one from in here)
- -> ClassOpItem
- -> TcId -- The method Id
- -> TcM (LHsBinds Id)
-
-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 }
+When typechecking the binding 'op = e', we'll have a meth_id for op
+whose type is
+ op :: forall c. Foo c => forall b. Ord b => [c] -> b -> b -> b
- where
- meth_name = idName meth_id
- sel_name = idName sel_id
- loc = getSrcSpan meth_id
- (clas, inst_tys) = getDictClassTys this_dict
+So tcPolyBinds must be capable of dealing with nested polytypes;
+and so it is. See TcBinds.tcMonoBinds (with type-sig case).
- 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 ])
+Note [Silly default-method bind]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+When we pass the default method binding to the type checker, it must
+look like op2 = e
+not $dmop2 = e
+otherwise the "$dm" stuff comes out error messages. But we want the
+"$dm" to come out in the interface file. So we typecheck the former,
+and wrap it in a let, thus
+ $dmop2 = let op2 = e in op2
+This makes the error messages right.
- mk_dm_app dm_id -- dm tys inst_dict
- = mkLHsWrap (WpApp this_dict_id `WpCompose` mkWpTyApps inst_tys)
- (L loc (HsVar dm_id))
+%************************************************************************
+%* *
+ Extracting generic instance declaration from class declarations
+%* *
+%************************************************************************
----------------------------
-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
- -- the type enviroment, and we get a tcLookup failure on $dmeth later.
-
- -- Check the bindings; first adding inst_tyvars to the envt
- -- so that we don't quantify over them in nested places
-
- 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
+@getGenericInstances@ extracts the generic instance declarations from a class
+declaration. For exmaple
+
+ class C a where
+ op :: a -> a
- ; 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)
+ op{ x+y } (Inl v) = ...
+ op{ x+y } (Inr v) = ...
+ op{ x*y } (v :*: w) = ...
+ op{ 1 } Unit = ...
- ; return (unitBag poly_meth_bind) }}
+gives rise to the instance declarations
+ instance C (x+y) where
+ op (Inl v) = ...
+ op (Inr v) = ...
+
+ instance C (x*y) where
+ op (v :*: w) = ...
----------------------------
-mkMethId :: InstOrigin -> Class
- -> Id -> [TcType] -- Selector, and instance types
- -> TcM (Maybe Inst, Id)
-
--- mkMethId instantiates the selector Id at the specified types
-mkMethId origin clas sel_id inst_tys
- = let
- (tyvars,rho) = tcSplitForAllTys (idType sel_id)
- rho_ty = ASSERT( length tyvars == length inst_tys )
- substTyWith tyvars inst_tys rho
- (preds,tau) = tcSplitPhiTy rho_ty
- 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 }
- )
- if isSingleton preds then do
- -- If it's the only one, make a 'method'
- 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
- -- op :: (?x :: String) => a -> a
- -- (mkMethId op T) should return an Inst with type
- -- (?x :: String) => T -> T
- -- 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.)
- uniq <- newUnique
- loc <- getSrcSpanM
- let
- real_tau = mkPhiTy (tail preds) tau
- meth_id = mkUserLocal (getOccName sel_id) uniq real_tau loc
-
- return (Nothing, meth_id)
+ instance C 1 where
+ op Unit = ...
----------------------------
--- 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
----------------------------
+\begin{code}
+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
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 (SigOrigin InstSkol) = True
-isInstDecl (SigOrigin (ClsSkol _)) = False
-\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!
-
-
-%************************************************************************
-%* *
-\subsection{Extracting generic instance declaration from class declarations}
-%* *
-%************************************************************************
-
-@getGenericInstances@ extracts the generic instance declarations from a class
-declaration. For exmaple
-
- class C a where
- op :: a -> a
-
- op{ x+y } (Inl v) = ...
- op{ x+y } (Inr v) = ...
- op{ x*y } (v :*: w) = ...
- op{ 1 } Unit = ...
-
-gives rise to the instance declarations
-
- instance C (x+y) where
- op (Inl v) = ...
- op (Inr v) = ...
-
- instance C (x*y) where
- op (v :*: w) = ...
-
- instance C 1 where
- op Unit = ...
-
-
-\begin{code}
-getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo]
+---------------------------
+getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo Name]
getGenericInstances class_decls
= do { gen_inst_infos <- mapM (addLocM get_generics) class_decls
; let { gen_inst_info = concat gen_inst_infos }
(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
= return [] -- The comon case: no generic default methods
--
-- 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
- mapM (addErrTc . dupGenericInsts) bad_groups
+ mapM_ (addErrTc . dupGenericInsts) bad_groups
-- Check that there is an InstInfo for each generic type constructor
let
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
---------------------------------
mkGenericInstance :: Class
-> (HsType Name, LHsBinds Name)
- -> TcM InstInfo
+ -> TcM (InstInfo Name)
mkGenericInstance clas (hs_ty, binds) = do
-- Make a generic instance declaration
%************************************************************************
\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 = " instance"
| otherwise = ""
ctxt = hsep [ptext (sLit "In the"), text thing,
ptext (sLit "declaration for"), quotes (ppr (tcdName decl))]
-defltMethCtxt clas
- = ptext (sLit "When checking the default methods for class") <+> quotes (ppr clas)
-
-methodCtxt 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)]
+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)]
-omittedMethodWarn 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)
+badGenericInstance :: Var -> SDoc -> SDoc
badGenericInstance sel_id because
= 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)"),
nest 2 (ppr inst_tys),
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")]
+ ptext (sLit "was not compiled with -XGenerics")]
+badGenericInstanceType :: LHsBinds Name -> SDoc
badGenericInstanceType binds
= 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
+dupGenericInsts :: [(TyCon, InstInfo a)] -> SDoc
dupGenericInsts tc_inst_infos
= vcat [ptext (sLit "More than one type pattern for a single generic type constructor:"),
nest 4 (vcat (map ppr_inst_ty tc_inst_infos)),
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)
\end{code}
projects / ghc-hetmet.git / blobdiff