%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
-\section[TcClassDcl]{Typechecking class declarations}
+
+Typechecking class declarations
\begin{code}
module TcClassDcl ( tcClassSigs, tcClassDecl2,
- getGenericInstances,
- MethodSpec, tcMethodBind, mkMethodBind,
- tcAddDeclCtxt, badMethodErr
+ findMethodBind, instantiateMethod, tcInstanceMethodBody,
+ mkGenericDefMethBind,
+ tcAddDeclCtxt, badMethodErr, badATErr, omittedATWarn
) where
#include "HsVersions.h"
import HsSyn
-import RnHsSyn ( maybeGenericMatch, extractHsTyVars )
-import RnExpr ( rnLExpr )
-import RnEnv ( lookupTopBndrRn, lookupImportedName )
-import Inst ( instToId, newDicts, newDictsAtLoc, newMethod, getOverlapFlag )
-import InstEnv ( mkLocalInstance )
-import TcEnv ( tcLookupLocatedClass,
- tcExtendTyVarEnv, tcExtendIdEnv,
- InstInfo(..), pprInstInfoDetails,
- simpleInstInfoTyCon, simpleInstInfoTy,
- InstBindings(..), newDFunName
- )
-import TcBinds ( TcPragFun, tcMonoBinds, tcPrags, mkPragFun, TcSigInfo(..) )
-import TcHsType ( tcHsKindedType, tcHsSigType )
-import TcSimplify ( tcSimplifyCheck )
-import TcUnify ( checkSigTyVars, sigCtxt )
-import TcMType ( tcSkolSigTyVars )
-import TcType ( Type, SkolemInfo(ClsSkol, InstSkol), UserTypeCtxt( GenPatCtxt ),
- TcType, TcThetaType, TcTyVar, mkTyVarTys,
- mkClassPred, tcSplitSigmaTy, tcSplitFunTys,
- tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitForAllTys, tcSplitPhiTy,
- getClassPredTys_maybe, mkPhiTy, mkTyVarTy
- )
+import TcEnv
+import TcPat( addInlinePrags )
+import TcBinds
+import TcUnify
+import TcHsType
+import TcMType
+import TcType
import TcRnMonad
-import Generics ( mkGenericRhs, validGenericInstanceType )
-import PrelInfo ( nO_METHOD_BINDING_ERROR_ID )
-import Class ( classTyVars, classBigSig,
- Class, ClassOpItem, DefMeth (..) )
-import TyCon ( TyCon, tyConName, tyConHasGenerics )
-import Type ( substTyWith )
-import MkId ( mkDefaultMethodId, mkDictFunId )
-import Id ( Id, idType, idName, mkUserLocal )
-import Name ( Name, NamedThing(..) )
-import NameEnv ( NameEnv, lookupNameEnv, mkNameEnv )
-import NameSet ( nameSetToList )
-import OccName ( reportIfUnused, mkDefaultMethodOcc )
-import RdrName ( RdrName, mkDerivedRdrName )
+import BuildTyCl( TcMethInfo )
+import Class
+import Id
+import Name
+import NameEnv
+import NameSet
+import Var
import Outputable
-import PrelNames ( genericTyConNames )
import DynFlags
-import ErrUtils ( dumpIfSet_dyn )
-import Util ( count, lengthIs, isSingleton, lengthExceeds )
-import Unique ( Uniquable(..) )
-import ListSetOps ( equivClassesByUniq, minusList )
-import SrcLoc ( Located(..), srcSpanStart, unLoc, noLoc )
-import Maybes ( seqMaybe, isJust, mapCatMaybes )
-import List ( partition )
-import BasicTypes ( RecFlag(..), Boxity(..) )
+import ErrUtils
+import SrcLoc
+import Maybes
+import BasicTypes
import Bag
import FastString
-\end{code}
+import Control.Monad
+\end{code}
Dictionary handling
%************************************************************************
\begin{code}
-tcClassSigs :: Name -- Name of the class
+tcClassSigs :: Name -- Name of the class
-> [LSig Name]
-> LHsBinds Name
- -> TcM [TcMethInfo]
-
-type TcMethInfo = (Name, DefMeth, Type) -- A temporary intermediate, to communicate
- -- between tcClassSigs and buildClass
+ -> TcM ([TcMethInfo], -- Exactly one for each method
+ NameEnv Type) -- Types of the generic-default methods
tcClassSigs clas sigs def_methods
- = do { dm_env <- checkDefaultBinds clas op_names def_methods
- ; mappM (tcClassSig dm_env) op_sigs }
- where
- op_sigs = [sig | sig@(L _ (TypeSig _ _)) <- sigs]
- op_names = [n | sig@(L _ (TypeSig (L _ n) _)) <- op_sigs]
-
+ = do { gen_dm_prs <- mapM (addLocM tc_gen_sig) gen_sigs
+ ; let gen_dm_env = mkNameEnv gen_dm_prs
-checkDefaultBinds :: Name -> [Name] -> LHsBinds Name -> TcM (NameEnv Bool)
- -- Check default bindings
- -- a) must be for a class op for this class
- -- b) must be all generic or all non-generic
- -- and return a mapping from class-op to Bool
- -- where True <=> it's a generic default method
-checkDefaultBinds clas ops binds
- = do dm_infos <- mapM (addLocM (checkDefaultBind clas ops)) (bagToList binds)
- return (mkNameEnv dm_infos)
+ ; op_info <- mapM (addLocM (tc_sig gen_dm_env)) vanilla_sigs
-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)
+ ; let op_names = mkNameSet [ n | (n,_,_) <- op_info ]
+ ; sequence_ [ failWithTc (badMethodErr clas n)
+ | n <- dm_bind_names, not (n `elemNameSet` op_names) ]
+ -- Value binding for non class-method (ie no TypeSig)
- -- Check that all the defns ar generic, or none are
- ; checkTc (all_generic || none_generic) (mixedGenericErr op)
+ ; sequence_ [ failWithTc (badGenericMethod clas n)
+ | (n,_) <- gen_dm_prs, not (n `elem` dm_bind_names) ]
+ -- Generic signature without value binding
- ; returnM (op, all_generic)
- }
+ ; return (op_info, gen_dm_env) }
where
- n_generic = count (isJust . maybeGenericMatch) matches
- none_generic = n_generic == 0
- all_generic = matches `lengthIs` n_generic
-
-
-tcClassSig :: NameEnv Bool -- Info about default methods;
- -> LSig Name
- -> TcM TcMethInfo
-
-tcClassSig dm_env (L loc (TypeSig (L _ op_name) op_hs_ty))
- = setSrcSpan loc $ do
- { op_ty <- tcHsKindedType op_hs_ty -- Class tyvars already in scope
- ; let dm = case lookupNameEnv dm_env op_name of
- Nothing -> NoDefMeth
- Just False -> DefMeth
- Just True -> GenDefMeth
- ; returnM (op_name, dm, op_ty) }
+ vanilla_sigs = [L loc (nm,ty) | L loc (TypeSig nm ty) <- sigs]
+ gen_sigs = [L loc (nm,ty) | L loc (GenericSig nm ty) <- sigs]
+ dm_bind_names :: [Name] -- These ones have a value binding in the class decl
+ dm_bind_names = [op | L _ (FunBind {fun_id = L _ op}) <- bagToList def_methods]
+
+ tc_sig genop_env (L _ op_name, op_hs_ty)
+ = do { op_ty <- tcHsKindedType op_hs_ty -- Class tyvars already in scope
+ ; let dm | op_name `elemNameEnv` genop_env = GenericDM
+ | op_name `elem` dm_bind_names = VanillaDM
+ | otherwise = NoDM
+ ; return (op_name, dm, op_ty) }
+
+ tc_gen_sig (L _ op_name, gen_hs_ty)
+ = do { gen_op_ty <- tcHsKindedType gen_hs_ty
+ ; return (op_name, gen_op_ty) }
\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])
+ -> TcM (LHsBinds 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
-- 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
- prag_fn = mkPragFun sigs
- tc_dm = tcDefMeth clas tyvars default_binds 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.)
- in
- mapAndUnzipM tc_dm dm_sel_ids `thenM` \ (defm_binds, dm_ids_s) ->
- returnM (listToBag defm_binds, concat dm_ids_s)
-
-tcDefMeth clas tyvars binds_in prag_fn sel_id
- = do { dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_id)
- ; let rigid_info = ClsSkol clas
- clas_tyvars = tcSkolSigTyVars rigid_info tyvars
- inst_tys = mkTyVarTys clas_tyvars
- dm_ty = idType sel_id -- Same as dict selector!
- theta = [mkClassPred clas inst_tys]
- local_dm_id = mkDefaultMethodId dm_name dm_ty
- origin = SigOrigin rigid_info
-
- ; (_, meth_info) <- mkMethodBind origin clas inst_tys binds_in (sel_id, DefMeth)
- ; [this_dict] <- newDicts origin theta
- ; (defm_bind, insts_needed) <- getLIE (tcMethodBind clas_tyvars theta
- [this_dict] prag_fn meth_info)
-
- ; addErrCtxt (defltMethCtxt clas) $ do
-
- -- Check the context
- { dict_binds <- tcSimplifyCheck
- (ptext SLIT("class") <+> ppr clas)
- clas_tyvars
- [this_dict]
- insts_needed
-
- -- Simplification can do unification
- ; checkSigTyVars clas_tyvars
-
- -- 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 (_,dm_inst_id,_) = meth_info
- sel_name = idName sel_id
- inline_prags = filter isInlineLSig (prag_fn sel_name)
- ; prags <- tcPrags dm_inst_id inline_prags
-
- ; let full_bind = AbsBinds clas_tyvars
- [instToId this_dict]
- [(clas_tyvars, local_dm_id, dm_inst_id, prags)]
- (dict_binds `unionBags` defm_bind)
- ; returnM (noLoc full_bind, [local_dm_id]) }}
-
-mkDefMethRdrName :: Id -> RdrName
-mkDefMethRdrName sel_id = mkDerivedRdrName (idName sel_id) mkDefaultMethodOcc
-\end{code}
-
+ ; let
+ (tyvars, _, _, op_items) = classBigSig clas
+ prag_fn = mkPragFun sigs default_binds
+ sig_fn = mkSigFun sigs
+ clas_tyvars = tcSuperSkolTyVars tyvars
+ pred = mkClassPred clas (mkTyVarTys clas_tyvars)
+ ; this_dict <- newEvVar pred
-%************************************************************************
-%* *
-\subsection{Typechecking a method}
-%* *
-%************************************************************************
+ ; traceTc "TIM2" (ppr sigs)
+ ; let tc_dm = tcDefMeth clas clas_tyvars
+ this_dict default_binds
+ sig_fn prag_fn
-@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.
+ ; dm_binds <- tcExtendTyVarEnv clas_tyvars $
+ mapM tc_dm op_items
-\begin{code}
-type MethodSpec = (Id, -- Global selector Id
- Id, -- Local Id (class tyvars instantiated)
- LHsBind Name) -- Binding for the method
-
-tcMethodBind
- :: [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
- -> TcPragFun -- Pragmas (e.g. inline pragmas)
- -> MethodSpec -- Details of this method
- -> TcM (LHsBinds Id)
-
-tcMethodBind inst_tyvars inst_theta avail_insts prag_fn
- (sel_id, meth_id, meth_bind)
- = recoverM (returnM 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
+ ; return (unionManyBags dm_binds) }
-
- let meth_sig = noLoc (TypeSig (noLoc (idName meth_id)) (noLoc bogus_ty))
- bogus_ty = HsTupleTy Boxed [] -- *Only* used to extract scoped type
- -- variables... and there aren't any
- lookup_sig name = ASSERT( name == idName meth_id )
- Just meth_sig
- in
- tcExtendTyVarEnv inst_tyvars (
- tcExtendIdEnv [meth_id] $ -- In scope for tcInstSig
- addErrCtxt (methodCtxt sel_id) $
- getLIE $
- tcMonoBinds [meth_bind] lookup_sig 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
- in
-
- addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $
- newDictsAtLoc (sig_loc sig) (sig_theta sig) `thenM` \ meth_dicts ->
- let
- meth_tvs = sig_tvs sig
- all_tyvars = meth_tvs ++ inst_tyvars
- all_insts = avail_insts ++ meth_dicts
- sel_name = idName sel_id
- in
- tcSimplifyCheck
- (ptext SLIT("class or instance method") <+> quotes (ppr sel_id))
- 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
- (map instToId meth_dicts)
- [(meth_tvs, meth_id, local_meth_id, prags)]
- (lie_binds `unionBags` meth_bind)
- in
- returnM (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
- -> 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 = 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
- -- 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
- -- 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.)
- newUnique `thenM` \ uniq ->
- getSrcSpanM `thenM` \ loc ->
- let
- real_tau = mkPhiTy (tail preds) tau
- meth_id = mkUserLocal (getOccName sel_id) uniq real_tau
- (srcSpanStart loc) --TODO
- 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
+tcClassDecl2 d = pprPanic "tcClassDecl2" (ppr d)
+
+tcDefMeth :: Class -> [TyVar] -> EvVar -> LHsBinds Name
+ -> SigFun -> PragFun -> ClassOpItem
+ -> TcM (LHsBinds TcId)
+-- 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.)
+tcDefMeth clas tyvars this_dict binds_in sig_fn prag_fn (sel_id, dm_info)
+ = case dm_info of
+ NoDefMeth -> do { mapM_ (addLocM (badDmPrag sel_id)) prags
+ ; return emptyBag }
+ DefMeth dm_name -> tc_dm dm_name
+ GenDefMeth dm_name -> tc_dm dm_name
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
- = -- 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"
- (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 }
+ sel_name = idName sel_id
+ prags = prag_fn sel_name
+ dm_sig_fn _ = sig_fn sel_name
+ dm_bind = findMethodBind sel_name binds_in
+ `orElse` pprPanic "tcDefMeth" (ppr sel_id)
+
+ -- Eg. class C a where
+ -- op :: forall b. Eq b => a -> [b] -> a
+ -- gen_op :: a -> a
+ -- generic gen_op :: D a => a -> a
+ -- The "local_dm_ty" is precisely the type in the above
+ -- type signatures, ie with no "forall a. C a =>" prefix
+
+ tc_dm dm_name
+ = do { dm_id <- tcLookupId dm_name
+ ; local_dm_name <- newLocalName sel_name
+ -- Base the local_dm_name on the selector name, because
+ -- type errors from tcInstanceMethodBody come from here
+
+ ; let local_dm_ty = instantiateMethod clas dm_id (mkTyVarTys tyvars)
+ local_dm_id = mkLocalId local_dm_name local_dm_ty
+
+ ; dm_id_w_inline <- addInlinePrags dm_id prags
+ ; spec_prags <- tcSpecPrags dm_id prags
+
+ ; warnTc (not (null spec_prags))
+ (ptext (sLit "Ignoring SPECIALISE pragmas on default method")
+ <+> quotes (ppr sel_name))
+
+ ; tc_bind <- tcInstanceMethodBody (ClsSkol clas) tyvars [this_dict]
+ dm_id_w_inline local_dm_id dm_sig_fn
+ IsDefaultMethod dm_bind
+
+ ; return (unitBag tc_bind) }
+
+---------------
+tcInstanceMethodBody :: SkolemInfo -> [TcTyVar] -> [EvVar]
+ -> Id -> Id
+ -> SigFun -> TcSpecPrags -> LHsBind Name
+ -> TcM (LHsBind Id)
+tcInstanceMethodBody skol_info tyvars dfun_ev_vars
+ meth_id local_meth_id
+ meth_sig_fn specs
+ (L loc bind)
+ = do { -- 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
+ let lm_bind = L loc (bind { fun_id = L loc (idName local_meth_id) })
+ -- Substitute the local_meth_name for the binder
+ -- NB: the binding is always a FunBind
+ ; traceTc "TIM" (ppr local_meth_id $$ ppr (meth_sig_fn (idName local_meth_id)))
+ ; (ev_binds, (tc_bind, _))
+ <- checkConstraints skol_info tyvars dfun_ev_vars $
+ tcExtendIdEnv [local_meth_id] $
+ tcPolyBinds TopLevel meth_sig_fn no_prag_fn
+ NonRecursive NonRecursive
+ [lm_bind]
+
+ ; let full_bind = AbsBinds { abs_tvs = tyvars, abs_ev_vars = dfun_ev_vars
+ , abs_exports = [(tyvars, meth_id, local_meth_id, specs)]
+ , abs_ev_binds = ev_binds
+ , abs_binds = tc_bind }
+
+ ; return (L loc full_bind) }
where
- rhs = mkGenericRhs sel_id clas_tyvar tycon
-
- -- The tycon is only used in the generic case, and in that
- -- 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
- [ty] -> case tcSplitTyConApp_maybe ty of
- Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon
- other -> Nothing
- other -> Nothing
-
-isInstDecl (SigOrigin (InstSkol _)) = True
-isInstDecl (SigOrigin (ClsSkol _)) = False
+ no_prag_fn _ = [] -- No pragmas for local_meth_id;
+ -- they are all for meth_id
\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)
+instantiateMethod :: Class -> Id -> [TcType] -> TcType
+-- Take a class operation, say
+-- op :: forall ab. C a => forall c. Ix c => (b,c) -> a
+-- Instantiate it at [ty1,ty2]
+-- Return the "local method type":
+-- forall c. Ix x => (ty2,c) -> ty1
+instantiateMethod clas sel_id inst_tys
+ = ASSERT( ok_first_pred ) local_meth_ty
+ where
+ (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)
+
+ ok_first_pred = case getClassPredTys_maybe first_pred of
+ Just (clas1, _tys) -> clas == clas1
+ Nothing -> False
+ -- The first predicate should be of form (C a b)
+ -- where C is the class in question
+
+
+---------------------------
+findMethodBind :: Name -- Selector name
+ -> LHsBinds Name -- A group of bindings
+ -> Maybe (LHsBind Name) -- The binding
+findMethodBind sel_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
+ f bind@(L _ (FunBind { fun_id = L _ op_name }))
+ | op_name == sel_name
+ = Just bind
+ f _other = Nothing
\end{code}
+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
+
+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
+
+So tcPolyBinds must be capable of dealing with nested polytypes;
+and so it is. See TcBinds.tcMonoBinds (with type-sig case).
+
+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.
+
%************************************************************************
%* *
-\subsection{Extracting generic instance declaration from class declarations}
+ Extracting generic instance declaration from class declarations
%* *
%************************************************************************
instance C 1 where
op Unit = ...
-
\begin{code}
-getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo]
-getGenericInstances class_decls
- = do { gen_inst_infos <- mappM (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 []
- 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 }}
-
-get_generics decl@(ClassDecl {tcdLName = class_name, tcdMeths = def_methods})
- | null generic_binds
- = returnM [] -- 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 ->
-
- -- 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 ->
-
- -- Check that there is only one InstInfo for each type constructor
- -- The main way this can fail is if you write
- -- f {| a+b |} ... = ...
- -- f {| x+y |} ... = ...
- -- Then at this point we'll have an InstInfo for each
- let
- tc_inst_infos :: [(TyCon, InstInfo)]
- 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_`
-
- -- 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
- where
- generic_binds :: [(HsType Name, LHsBind Name)]
- generic_binds = getGenericBinds def_methods
-
-
----------------------------------
-getGenericBinds :: LHsBinds Name -> [(HsType Name, LHsBind Name)]
- -- Takes a group of method bindings, finds the generic ones, and returns
- -- them in finite map indexed by the type parameter in the definition.
-getGenericBinds binds = concat (map getGenericBind (bagToList binds))
+mkGenericDefMethBind :: Class -> [Type] -> Id -> Name -> TcM (LHsBind Name)
+mkGenericDefMethBind clas inst_tys sel_id dm_name
+ = -- A generic default method
+ -- If the method is defined generically, we only have to call the
+ -- dm_name.
+ do { dflags <- getDOpts
+ ; 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)]))
-getGenericBind (L loc bind@(FunBind { fun_matches = MatchGroup matches ty }))
- = groupWith wrap (mapCatMaybes maybeGenericMatch matches)
+ ; return (noLoc $ mkFunBind (noLoc (idName sel_id))
+ [mkSimpleMatch [] rhs]) }
where
- wrap ms = L loc (bind { fun_matches = MatchGroup ms ty })
-getGenericBind _
- = []
-
-groupWith :: ([a] -> b) -> [(HsType Name, a)] -> [(HsType Name, b)]
-groupWith op [] = []
-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'
-
-eqPatLType :: LHsType Name -> LHsType Name -> Bool
-eqPatLType t1 t2 = unLoc t1 `eqPatType` unLoc t2
-
-eqPatType :: HsType Name -> HsType Name -> Bool
--- 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 (HsNumTy n1) (HsNumTy n2) = n1 == n2
-eqPatType (HsParTy t1) t2 = unLoc t1 `eqPatType` t2
-eqPatType t1 (HsParTy t2) = t1 `eqPatType` unLoc t2
-eqPatType _ _ = False
-
----------------------------------
-mkGenericInstance :: Class
- -> (HsType Name, LHsBinds Name)
- -> TcM InstInfo
-
-mkGenericInstance clas (hs_ty, binds)
- -- Make a generic instance declaration
- -- For example: instance (C a, C b) => C (a+b) where { binds }
-
- = -- 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 ->
- let
- (tyvars, inst_ty) = tcSplitForAllTys forall_inst_ty
- in
- checkTc (validGenericInstanceType inst_ty)
- (badGenericInstanceType binds) `thenM_`
-
- -- Make the dictionary function.
- getSrcSpanM `thenM` \ span ->
- getOverlapFlag `thenM` \ overlap_flag ->
- newDFunName clas [inst_ty] (srcSpanStart span) `thenM` \ dfun_name ->
- 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 [] })
+ rhs = nlHsVar dm_name
\end{code}
-
%************************************************************************
%* *
Error messages
%************************************************************************
\begin{code}
+tcAddDeclCtxt :: TyClDecl Name -> TcM a -> TcM a
tcAddDeclCtxt decl thing_inside
= addErrCtxt ctxt thing_inside
where
- thing = case decl of
- ClassDecl {} -> "class"
- TySynonym {} -> "type synonym"
- TyData {tcdND = NewType} -> "newtype"
- TyData {tcdND = DataType} -> "data type"
+ thing | isClassDecl decl = "class"
+ | isTypeDecl decl = "type synonym" ++ maybeInst
+ | isDataDecl decl = if tcdND decl == NewType
+ then "newtype" ++ maybeInst
+ else "data type" ++ maybeInst
+ | isFamilyDecl decl = "family"
+ | otherwise = panic "tcAddDeclCtxt/thing"
- ctxt = hsep [ptext SLIT("In the"), text thing,
- ptext SLIT("declaration for"), quotes (ppr (tcdName decl))]
+ maybeInst | isFamInstDecl decl = " instance"
+ | otherwise = ""
-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)
+ ctxt = hsep [ptext (sLit "In the"), text thing,
+ ptext (sLit "declaration for"), quotes (ppr (tcdName decl))]
+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)]
-
-omittedMethodWarn sel_id
- = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id)
-
-badGenericInstance sel_id because
- = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id),
- because]
-
-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 a b c)")]
-
-notGeneric tycon
- = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+>
- ptext SLIT("was not compiled with -fgenerics")]
-
+ = hsep [ptext (sLit "Class"), quotes (ppr clas),
+ ptext (sLit "does not have a method"), quotes (ppr op)]
+
+badGenericMethod :: Outputable a => a -> Name -> SDoc
+badGenericMethod clas op
+ = hsep [ptext (sLit "Class"), quotes (ppr clas),
+ ptext (sLit "has a generic-default signature without a binding"), 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)]
+
+omittedATWarn :: Name -> SDoc
+omittedATWarn at
+ = ptext (sLit "No explicit AT declaration for") <+> quotes (ppr at)
+{-
+badGenericInstanceType :: LHsBinds Name -> SDoc
badGenericInstanceType binds
- = vcat [ptext SLIT("Illegal type pattern in the generic bindings"),
- nest 4 (ppr binds)]
+ = vcat [ptext (sLit "Illegal type pattern in the generic bindings"),
+ nest 2 (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:"),
- nest 4 (vcat (map ppr_inst_ty tc_inst_infos)),
- ptext SLIT("All the type patterns for a generic type constructor must be identical")
+ = vcat [ptext (sLit "More than one type pattern for a single generic type constructor:"),
+ nest 2 (vcat (map ppr_inst_ty tc_inst_infos)),
+ ptext (sLit "All the type patterns for a generic type constructor must be identical")
]
where
ppr_inst_ty (_,inst) = ppr (simpleInstInfoTy inst)
-
-mixedGenericErr op
- = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op)
+-}
+badDmPrag :: Id -> Sig Name -> TcM ()
+badDmPrag sel_id prag
+ = addErrTc (ptext (sLit "The") <+> hsSigDoc prag <+> ptext (sLit "for default method")
+ <+> quotes (ppr sel_id)
+ <+> ptext (sLit "lacks an accompanying binding"))
\end{code}
projects / ghc-hetmet.git / blobdiff