\section[TcClassDcl]{Typechecking class declarations}
\begin{code}
-module TcClassDcl ( tcClassDecl1, tcClassDecls2, mkImplicitClassBinds,
- tcMethodBind, badMethodErr
+module TcClassDcl ( tcClassDecl1, tcClassDecls2,
+ tcMethodBind, mkMethodBind, badMethodErr
) where
#include "HsVersions.h"
-import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..),
- HsExpr(..), HsLit(..), HsType(..), HsPred(..),
+import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..),
+ HsExpr(..), HsLit(..), InPat(WildPatIn),
mkSimpleMatch, andMonoBinds, andMonoBindList,
- isClassDecl, isClassOpSig, isPragSig,
- fromClassDeclNameList, tyClDeclName
+ isClassOpSig, isPragSig,
+ getClassDeclSysNames, placeHolderType
)
-import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..), EP(..) )
+import BasicTypes ( RecFlag(..), StrictnessMark(..) )
import RnHsSyn ( RenamedTyClDecl,
RenamedClassOpSig, RenamedMonoBinds,
- RenamedContext, RenamedHsDecl, RenamedSig,
- RenamedHsExpr, maybeGenericMatch
+ maybeGenericMatch
)
-import TcHsSyn ( TcMonoBinds, idsToMonoBinds )
+import TcHsSyn ( TcMonoBinds )
-import Inst ( InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, newDicts, newMethod )
-import TcEnv ( TcId, TcEnv, TyThing(..), TyThingDetails(..), tcAddImportedIdInfo,
- tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars,
- tcExtendLocalValEnv, tcExtendTyVarEnv, newDefaultMethodName
+import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs,
+ instToId, newDicts, newMethod )
+import TcEnv ( TyThingDetails(..),
+ tcLookupClass, tcExtendTyVarEnv2,
+ tcExtendTyVarEnv
+ )
+import TcBinds ( tcMonoBinds )
+import TcMonoType ( TcSigInfo(..), tcHsType, tcHsTheta, mkTcSig )
+import TcSimplify ( tcSimplifyCheck )
+import TcUnify ( checkSigTyVars, sigCtxt )
+import TcMType ( tcInstTyVars )
+import TcType ( Type, TyVarDetails(..), TcType, TcThetaType, TcTyVar,
+ mkTyVarTys, mkPredTys, mkClassPred, tcSplitSigmaTy, tcSplitFunTys,
+ tcIsTyVarTy, tcSplitTyConApp_maybe
)
-import TcBinds ( tcBindWithSigs, tcSpecSigs )
-import TcMonoType ( tcHsSigType, tcClassContext, checkSigTyVars, sigCtxt, mkTcSig )
-import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
-import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcSigTyVars )
import TcMonad
-import Generics ( mkGenericRhs, validGenericMethodType )
+import Generics ( mkGenericRhs )
import PrelInfo ( nO_METHOD_BINDING_ERROR_ID )
-import Class ( classTyVars, classBigSig, classSelIds, classTyCon, Class, ClassOpItem,
- DefMeth (..) )
-import Bag ( bagToList )
-import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods, opt_PprStyle_Debug )
+import Class ( classTyVars, classBigSig, classTyCon,
+ Class, ClassOpItem, DefMeth (..) )
+import TyCon ( tyConGenInfo )
import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId )
-import DataCon ( mkDataCon, notMarkedStrict )
-import Id ( Id, idType, idName )
-import Name ( Name, nameOccName, isLocallyDefined, NamedThing(..), mkSysLocalName,
- NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv, nameEnvElts )
-import NameSet ( NameSet, mkNameSet, elemNameSet, emptyNameSet )
+import DataCon ( mkDataCon )
+import Id ( Id, idType, idName, setIdLocalExported )
+import Module ( Module )
+import Name ( Name, NamedThing(..) )
+import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv )
+import NameSet ( emptyNameSet )
import Outputable
-import Type ( Type, ClassContext, mkTyVarTys, mkDictTys, mkSigmaTy, mkClassPred,
- splitTyConApp_maybe, isTyVarTy
- )
import Var ( TyVar )
-import VarSet ( mkVarSet, emptyVarSet )
+import CmdLineOpts
+import UnicodeUtil ( stringToUtf8 )
import ErrUtils ( dumpIfSet )
-import Util ( count )
-import Maybes ( seqMaybe, maybeToBool, orElse )
+import Util ( count, lengthIs, equalLength )
+import Maybes ( seqMaybe )
+import Maybe ( isJust )
+import FastString
\end{code}
%************************************************************************
\begin{code}
-tcClassDecl1 :: TcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails)
-tcClassDecl1 rec_env
- (ClassDecl context class_name
- tyvar_names fundeps class_sigs def_methods pragmas
- sys_names src_loc)
- = -- CHECK ARITY 1 FOR HASKELL 1.4
- checkTc (opt_GlasgowExts || length tyvar_names == 1)
- (classArityErr class_name) `thenTc_`
-
- -- LOOK THINGS UP IN THE ENVIRONMENT
+
+tcClassDecl1 :: RenamedTyClDecl -> TcM (Name, TyThingDetails)
+tcClassDecl1 (ClassDecl {tcdCtxt = context, tcdName = class_name,
+ tcdTyVars = tyvar_names, tcdFDs = fundeps,
+ tcdSigs = class_sigs, tcdMeths = def_methods,
+ tcdSysNames = sys_names, tcdLoc = src_loc})
+ = -- LOOK THINGS UP IN THE ENVIRONMENT
tcLookupClass class_name `thenTc` \ clas ->
let
tyvars = classTyVars clas
op_sigs = filter isClassOpSig class_sigs
op_names = [n | ClassOpSig n _ _ _ <- op_sigs]
- (_, datacon_name, datacon_wkr_name, sc_sel_names) = fromClassDeclNameList sys_names
+ (_, datacon_name, datacon_wkr_name, sc_sel_names) = getClassDeclSysNames sys_names
in
tcExtendTyVarEnv tyvars $
- -- CHECK THAT THE DEFAULT BINDINGS ARE LEGAL
- checkDefaultBinds clas op_names def_methods `thenTc` \ dm_info ->
- checkGenericClassIsUnary clas dm_info `thenTc_`
+ checkDefaultBinds clas op_names def_methods `thenTc` \ mb_dm_env ->
-- CHECK THE CONTEXT
- tcSuperClasses clas context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) ->
+ -- The renamer has already checked that the context mentions
+ -- only the type variable of the class decl.
+ -- Context is already kind-checked
+ ASSERT( equalLength context sc_sel_names )
+ tcHsTheta context `thenTc` \ sc_theta ->
-- CHECK THE CLASS SIGNATURES,
- mapTc (tcClassSig rec_env clas tyvars dm_info) op_sigs `thenTc` \ sig_stuff ->
+ mapTc (tcClassSig clas tyvars mb_dm_env) op_sigs `thenTc` \ sig_stuff ->
-- MAKE THE CLASS DETAILS
let
(op_tys, op_items) = unzip sig_stuff
- sc_tys = mkDictTys sc_theta
+ sc_tys = mkPredTys sc_theta
dict_component_tys = sc_tys ++ op_tys
+ sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names]
dict_con = mkDataCon datacon_name
- [notMarkedStrict | _ <- dict_component_tys]
+ [NotMarkedStrict | _ <- dict_component_tys]
[{- No labelled fields -}]
tyvars
[{-No context-}]
\end{code}
\begin{code}
-checkDefaultBinds :: Class -> [Name] -> RenamedMonoBinds -> TcM (NameEnv (DefMeth Name))
+checkDefaultBinds :: Class -> [Name] -> Maybe RenamedMonoBinds
+ -> TcM (Maybe (NameEnv Bool))
+ -- The returned environment says
+ -- x not in env => no default method
+ -- x -> True => generic default method
+ -- x -> False => polymorphic default method
+
-- 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 DefMeth info
-checkDefaultBinds clas ops EmptyMonoBinds = returnTc emptyNameEnv
+ -- But do all this only for source binds
-checkDefaultBinds clas ops (AndMonoBinds b1 b2)
- = checkDefaultBinds clas ops b1 `thenTc` \ dm_info1 ->
- checkDefaultBinds clas ops b2 `thenTc` \ dm_info2 ->
- returnTc (dm_info1 `plusNameEnv` dm_info2)
+checkDefaultBinds clas ops Nothing
+ = returnTc Nothing
-checkDefaultBinds clas ops (FunMonoBind op _ matches loc)
- = tcAddSrcLoc loc $
+checkDefaultBinds clas ops (Just mbs)
+ = go mbs `thenTc` \ dm_env ->
+ returnTc (Just dm_env)
+ where
+ go EmptyMonoBinds = returnTc emptyNameEnv
+
+ go (AndMonoBinds b1 b2)
+ = go b1 `thenTc` \ dm_info1 ->
+ go b2 `thenTc` \ dm_info2 ->
+ returnTc (dm_info1 `plusNameEnv` dm_info2)
+
+ go (FunMonoBind op _ matches loc)
+ = tcAddSrcLoc loc $
-- Check that the op is from this class
- checkTc (op `elem` ops) (badMethodErr clas op) `thenTc_`
+ checkTc (op `elem` ops) (badMethodErr clas op) `thenTc_`
-- Check that all the defns ar generic, or none are
- checkTc (all_generic || none_generic) (mixedGenericErr op) `thenTc_`
-
- -- Make up the right dm_info
- if all_generic then
- returnTc (unitNameEnv op GenDefMeth)
- else
- -- An explicit non-generic default method
- newDefaultMethodName op loc `thenNF_Tc` \ dm_name ->
- returnTc (unitNameEnv op (DefMeth dm_name))
+ checkTc (all_generic || none_generic) (mixedGenericErr op) `thenTc_`
- where
- n_generic = count (maybeToBool . maybeGenericMatch) matches
- none_generic = n_generic == 0
- all_generic = n_generic == length matches
-
-checkGenericClassIsUnary clas dm_info
- = -- Check that if the class has generic methods, then the
- -- class has only one parameter. We can't do generic
- -- multi-parameter type classes!
- checkTc (unary || no_generics) (genericMultiParamErr clas)
- where
- unary = length (classTyVars clas) == 1
- no_generics = null [() | GenDefMeth <- nameEnvElts dm_info]
+ returnTc (unitNameEnv op all_generic)
+ where
+ n_generic = count (isJust . maybeGenericMatch) matches
+ none_generic = n_generic == 0
+ all_generic = matches `lengthIs` n_generic
\end{code}
\begin{code}
-tcSuperClasses :: Class
- -> RenamedContext -- class context
- -> [Name] -- Names for superclass selectors
- -> TcM (ClassContext, -- the superclass context
- [Id]) -- superclass selector Ids
-
-tcSuperClasses clas context sc_sel_names
- = -- Check the context.
- -- The renamer has already checked that the context mentions
- -- only the type variable of the class decl.
-
- -- For std Haskell check that the context constrains only tyvars
- (if opt_GlasgowExts then
- returnTc ()
- else
- mapTc_ check_constraint context
- ) `thenTc_`
-
- -- Context is already kind-checked
- tcClassContext context `thenTc` \ sc_theta ->
- let
- sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names]
- in
- -- Done
- returnTc (sc_theta, sc_sel_ids)
-
- where
- check_constraint sc@(HsPClass c tys)
- = checkTc (all is_tyvar tys) (superClassErr clas sc)
-
- is_tyvar (HsTyVar _) = True
- is_tyvar other = False
-
-
-tcClassSig :: TcEnv -- Knot tying only!
- -> Class -- ...ditto...
+tcClassSig :: Class -- ...ditto...
-> [TyVar] -- The class type variable, used for error check only
- -> NameEnv (DefMeth Name) -- Info about default methods
+ -> Maybe (NameEnv Bool) -- Info about default methods;
+ -- Nothing => imported class defn with no method binds
-> RenamedClassOpSig
-> TcM (Type, -- Type of the method
ClassOpItem) -- Selector Id, default-method Id, True if explicit default binding
-- so we distinguish them in checkDefaultBinds, and pass this knowledge in the
-- Class.DefMeth data structure.
-tcClassSig rec_env clas clas_tyvars dm_info
- (ClassOpSig op_name maybe_dm op_ty src_loc)
+tcClassSig clas clas_tyvars maybe_dm_env
+ (ClassOpSig op_name sig_dm op_ty src_loc)
= tcAddSrcLoc src_loc $
-- Check the type signature. NB that the envt *already has*
-- bindings for the type variables; see comments in TcTyAndClassDcls.
+ tcHsType op_ty `thenTc` \ local_ty ->
- -- NB: Renamer checks that the class type variable is mentioned in local_ty,
- -- and that it is not constrained by theta
- tcHsSigType op_ty `thenTc` \ local_ty ->
let
- global_ty = mkSigmaTy clas_tyvars
- [mkClassPred clas (mkTyVarTys clas_tyvars)]
- local_ty
+ theta = [mkClassPred clas (mkTyVarTys clas_tyvars)]
-- Build the selector id and default method id
- sel_id = mkDictSelId op_name clas
+ sel_id = mkDictSelId op_name clas
+ DefMeth dm_name = sig_dm
- dm_info_name = maybe_dm `orElse` lookupNameEnv dm_info op_name `orElse` NoDefMeth
+ dm_info = case maybe_dm_env of
+ Nothing -> sig_dm
+ Just dm_env -> mk_src_dm_info dm_env
- dm_info_id = case dm_info_name of
- NoDefMeth -> NoDefMeth
- GenDefMeth -> GenDefMeth
- DefMeth dm_name -> DefMeth (tcAddImportedIdInfo rec_env dm_id)
- where
- dm_id = mkDefaultMethodId dm_name clas global_ty
+ mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of
+ Nothing -> NoDefMeth
+ Just True -> GenDefMeth
+ Just False -> DefMeth dm_name
in
- -- Check that for a generic method, the type of
- -- the method is sufficiently simple
- checkTc (dm_info_name /= GenDefMeth || validGenericMethodType local_ty)
- (badGenericMethodType op_name op_ty) `thenTc_`
-
- returnTc (local_ty, (sel_id, dm_info_id))
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[ClassDcl-pass2]{Class decls pass 2: default methods}
-%* *
-%************************************************************************
-
-@mkImplicitClassBinds@ produces a binding for the selector function for each method
-and superclass dictionary.
-
-\begin{code}
-mkImplicitClassBinds :: [Class] -> NF_TcM ([Id], TcMonoBinds)
-mkImplicitClassBinds classes
- = returnNF_Tc (concat cls_ids_s, andMonoBindList binds_s)
- -- The selector binds are already in the selector Id's unfoldings
- -- We don't return the data constructor etc from the class,
- -- because that's done via the class's TyCon
- where
- (cls_ids_s, binds_s) = unzip (map mk_implicit classes)
-
- mk_implicit clas = (sel_ids, binds)
- where
- sel_ids = classSelIds clas
- binds | isLocallyDefined clas = idsToMonoBinds sel_ids
- | otherwise = EmptyMonoBinds
+ returnTc (local_ty, (sel_id, dm_info))
\end{code}
-
%************************************************************************
%* *
\subsection[Default methods]{Default methods}
each local class decl.
\begin{code}
-tcClassDecls2 :: [RenamedHsDecl] -> NF_TcM (LIE, TcMonoBinds)
+tcClassDecls2 :: Module -> [RenamedTyClDecl] -> NF_TcM (LIE, TcMonoBinds, [Id])
-tcClassDecls2 decls
+tcClassDecls2 this_mod decls
= foldr combine
- (returnNF_Tc (emptyLIE, EmptyMonoBinds))
- [tcClassDecl2 cls_decl | TyClD cls_decl <- decls,
- isClassDecl cls_decl,
- isLocallyDefined (tyClDeclName cls_decl)]
+ (returnNF_Tc (emptyLIE, EmptyMonoBinds, []))
+ [tcClassDecl2 cls_decl | cls_decl@(ClassDecl {tcdMeths = Just _}) <- decls]
+ -- The 'Just' picks out source ClassDecls
where
- combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
- tc2 `thenNF_Tc` \ (lie2, binds2) ->
+ combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1, ids1) ->
+ tc2 `thenNF_Tc` \ (lie2, binds2, ids2) ->
returnNF_Tc (lie1 `plusLIE` lie2,
- binds1 `AndMonoBinds` binds2)
+ binds1 `AndMonoBinds` binds2,
+ ids1 ++ ids2)
\end{code}
@tcClassDecl2@ generates bindings for polymorphic default methods
\begin{code}
tcClassDecl2 :: RenamedTyClDecl -- The class declaration
- -> NF_TcM (LIE, TcMonoBinds)
+ -> NF_TcM (LIE, TcMonoBinds, [Id])
-tcClassDecl2 (ClassDecl context class_name
- tyvar_names _ sigs default_binds pragmas _ src_loc)
- = -- A locally defined class
- recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
+tcClassDecl2 (ClassDecl {tcdName = class_name, tcdSigs = sigs,
+ tcdMeths = Just default_binds, tcdLoc = src_loc})
+ = -- The 'Just' picks out source ClassDecls
+ recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds, [])) $
tcAddSrcLoc src_loc $
tcLookupClass class_name `thenNF_Tc` \ clas ->
prags = filter isPragSig sigs
tc_dm = tcDefMeth clas tyvars default_binds prags
in
- mapAndUnzipTc tc_dm op_items `thenTc` \ (defm_binds, const_lies) ->
+ mapAndUnzip3Tc tc_dm op_items `thenTc` \ (defm_binds, const_lies, dm_ids_s) ->
- returnTc (plusLIEs const_lies, andMonoBindList defm_binds)
+ returnTc (plusLIEs const_lies, andMonoBindList defm_binds, concat dm_ids_s)
-tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnTc (EmptyMonoBinds, emptyLIE)
-tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnTc (EmptyMonoBinds, emptyLIE)
+tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnTc (EmptyMonoBinds, emptyLIE, [])
+tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnTc (EmptyMonoBinds, emptyLIE, [])
-- 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
-- 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 binds_in prags op_item@(_, DefMeth dm_id)
- = tcInstTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) ->
+tcDefMeth clas tyvars binds_in prags op_item@(sel_id, DefMeth dm_name)
+ = tcInstTyVars ClsTv tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) ->
let
- theta = [(mkClassPred clas inst_tys)]
+ dm_ty = idType sel_id -- Same as dict selector!
+ -- The default method's type should really come from the
+ -- iface file, since it could be usage-generalised, but this
+ -- requires altering the mess of knots in TcModule and I'm
+ -- too scared to do that. Instead, I have disabled generalisation
+ -- of types of default methods (and dict funs) by annotating them
+ -- TyGenNever (in MkId). Ugh! KSW 1999-09.
+
+ theta = [mkClassPred clas inst_tys]
+ dm_id = mkDefaultMethodId dm_name dm_ty
+ local_dm_id = setIdLocalExported dm_id
+ -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId
+ xtve = tyvars `zip` clas_tyvars
in
- newDicts origin theta `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+ newDicts origin theta `thenNF_Tc` \ [this_dict] ->
- tcExtendTyVarEnvForMeths tyvars clas_tyvars (
- tcMethodBind clas origin clas_tyvars inst_tys theta
- binds_in prags False op_item
- ) `thenTc` \ (defm_bind, insts_needed, (_, local_dm_id)) ->
+ mkMethodBind origin clas inst_tys binds_in op_item `thenTc` \ (dm_inst, meth_info) ->
+ tcMethodBind xtve clas_tyvars theta
+ [this_dict] meth_info `thenTc` \ (defm_bind, insts_needed) ->
tcAddErrCtxt (defltMethCtxt clas) $
- -- tcMethodBind has checked that the class_tyvars havn't
- -- been unified with each other or another type, but we must
- -- still zonk them before passing them to tcSimplifyAndCheck
- zonkTcSigTyVars clas_tyvars `thenNF_Tc` \ clas_tyvars' ->
-
-- Check the context
- tcSimplifyAndCheck
+ tcSimplifyCheck
(ptext SLIT("class") <+> ppr clas)
- (mkVarSet clas_tyvars')
- this_dict
+ clas_tyvars
+ [this_dict]
insts_needed `thenTc` \ (const_lie, dict_binds) ->
+
+ -- Simplification can do unification
+ checkSigTyVars clas_tyvars `thenTc` \ clas_tyvars' ->
let
full_bind = AbsBinds
clas_tyvars'
- [this_dict_id]
- [(clas_tyvars', dm_id, local_dm_id)]
+ [instToId this_dict]
+ [(clas_tyvars', local_dm_id, instToId dm_inst)]
emptyNameSet -- No inlines (yet)
(dict_binds `andMonoBinds` defm_bind)
in
- returnTc (full_bind, const_lie)
+ returnTc (full_bind, const_lie, [dm_id])
where
origin = ClassDeclOrigin
\end{code}
\begin{code}
tcMethodBind
- :: Class
- -> InstOrigin
+ :: [(TyVar,TcTyVar)] -- Bindings for type environment
-> [TcTyVar] -- Instantiated type variables for the
- -- enclosing class/instance decl.
- -- They'll be signature tyvars, and we
- -- want to check that they don't get bound
- -> [TcType] -- Instance types
- -> TcThetaType -- Available theta; this could be used to check
- -- the method signature, but actually that's done by
- -- the caller; here, it's just used for the error message
- -> RenamedMonoBinds -- Method binding (pick the right one from in here)
- -> [RenamedSig] -- Pramgas (just for this one)
- -> Bool -- True <=> This method is from an instance declaration
- -> ClassOpItem -- The method selector and default-method Id
- -> TcM (TcMonoBinds, LIE, (LIE, TcId))
-
-tcMethodBind clas origin inst_tyvars inst_tys inst_theta
- meth_binds prags is_inst_decl (sel_id, dm_info)
+ -- enclosing class/instance decl.
+ -- They'll be signature tyvars, and we
+ -- want to check that they don't get bound
+ -- 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
+ -> (Id, TcSigInfo, RenamedMonoBinds) -- Details of this method
+ -> TcM (TcMonoBinds, LIE)
+
+tcMethodBind xtve inst_tyvars inst_theta avail_insts
+ (sel_id, meth_sig, meth_bind)
+ =
+ -- Check the bindings; first adding inst_tyvars to the envt
+ -- so that we don't quantify over them in nested places
+ tcExtendTyVarEnv2 xtve (
+ tcAddErrCtxt (methodCtxt sel_id) $
+ tcMonoBinds meth_bind [meth_sig] NonRecursive
+ ) `thenTc` \ (meth_bind, 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
+ TySigInfo meth_id meth_tvs meth_theta _ local_meth_id _ _ = meth_sig
+ in
+ tcAddErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $
+ newDicts SignatureOrigin meth_theta `thenNF_Tc` \ meth_dicts ->
+ let
+ all_tyvars = meth_tvs ++ inst_tyvars
+ all_insts = avail_insts ++ meth_dicts
+ in
+ tcSimplifyCheck
+ (ptext SLIT("class or instance method") <+> quotes (ppr sel_id))
+ all_tyvars all_insts meth_lie `thenTc` \ (lie, lie_binds) ->
+
+ checkSigTyVars all_tyvars `thenTc` \ all_tyvars' ->
+
+ let
+ meth_tvs' = take (length meth_tvs) all_tyvars'
+ poly_meth_bind = AbsBinds meth_tvs'
+ (map instToId meth_dicts)
+ [(meth_tvs', meth_id, local_meth_id)]
+ emptyNameSet -- Inlines?
+ (lie_binds `andMonoBinds` meth_bind)
+ in
+ returnTc (poly_meth_bind, lie)
+
+
+mkMethodBind :: InstOrigin
+ -> Class -> [TcType] -- Class and instance types
+ -> RenamedMonoBinds -- Method binding (pick the right one from in here)
+ -> ClassOpItem
+ -> TcM (Inst, -- Method inst
+ (Id, -- Global selector Id
+ TcSigInfo, -- Signature
+ RenamedMonoBinds)) -- Binding for the method
+
+mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info)
= tcGetSrcLoc `thenNF_Tc` \ loc ->
- newMethod origin sel_id inst_tys `thenNF_Tc` \ meth@(_, meth_id) ->
- mkTcSig meth_id loc `thenNF_Tc` \ sig_info ->
+ newMethod origin sel_id inst_tys `thenNF_Tc` \ meth_inst ->
let
+ meth_id = instToId meth_inst
meth_name = idName meth_id
- sig_msg = ptext SLIT("When checking the expected type for class method") <+> ppr sel_id
- meth_prags = find_prags (idName sel_id) meth_name prags
in
-- Figure out what method binding to use
-- If the user suppplied one, use it, else construct a default one
(case find_bind (idName sel_id) meth_name meth_binds of
Just user_bind -> returnTc user_bind
- Nothing -> mkDefMethRhs is_inst_decl clas inst_tys sel_id loc dm_info `thenTc` \ rhs ->
+ Nothing -> mkDefMethRhs origin clas inst_tys sel_id loc dm_info `thenTc` \ rhs ->
returnTc (FunMonoBind meth_name False -- Not infix decl
- [mkSimpleMatch [] rhs Nothing loc] loc)
+ [mkSimpleMatch [] rhs placeHolderType loc] loc)
) `thenTc` \ meth_bind ->
- -- Check the bindings; first add inst_tyvars to the envt
- -- so that we don't quantify over them in nested places
- -- The *caller* put the class/inst decl tyvars into the envt
- tcExtendGlobalTyVars (mkVarSet inst_tyvars)
- (tcAddErrCtxt (methodCtxt sel_id) $
- tcBindWithSigs NotTopLevel meth_bind
- [sig_info] meth_prags NonRecursive
- ) `thenTc` \ (binds, insts, _) ->
-
- tcExtendLocalValEnv [(meth_name, meth_id)]
- (tcSpecSigs meth_prags) `thenTc` \ (prag_binds1, prag_lie) ->
-
- -- The prag_lie for a SPECIALISE pragma will mention the function
- -- itself, so we have to simplify them away right now lest they float
- -- outwards!
- bindInstsOfLocalFuns prag_lie [meth_id] `thenTc` \ (prag_lie', prag_binds2) ->
-
- -- Now check that the instance type variables
- -- (or, in the case of a class decl, the class tyvars)
- -- have not been unified with anything in the environment
- --
- -- We do this for each method independently to localise error messages
- -- ...and this is why the call to tcExtendGlobalTyVars must be here
- -- rather than in the caller
- tcAddErrCtxtM (sigCtxt sig_msg inst_tyvars inst_theta (idType meth_id)) $
- checkSigTyVars inst_tyvars emptyVarSet `thenTc_`
-
- returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2,
- insts `plusLIE` prag_lie',
- meth)
+
+ mkTcSig meth_id loc `thenNF_Tc` \ meth_sig ->
+
+ returnTc (meth_inst, (sel_id, meth_sig, meth_bind))
+
-- 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 is_inst_decl clas inst_tys sel_id loc (DefMeth dm_id)
+mkDefMethRhs origin clas inst_tys sel_id loc (DefMeth dm_name)
= -- An polymorphic default method
- returnTc (HsVar (idName dm_id))
+ returnTc (HsVar dm_name)
-mkDefMethRhs is_inst_decl clas inst_tys sel_id loc NoDefMeth
+mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth
= -- No default method
-- Warn only if -fwarn-missing-methods
- warnTc (is_inst_decl && opt_WarnMissingMethods)
- (omittedMethodWarn sel_id clas) `thenNF_Tc_`
+ doptsTc Opt_WarnMissingMethods `thenNF_Tc` \ warn ->
+ warnTc (isInstDecl origin && warn)
+ (omittedMethodWarn sel_id) `thenNF_Tc_`
returnTc error_rhs
where
- error_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
- (HsLit (HsString (_PK_ error_msg)))
+ error_rhs = HsLam (mkSimpleMatch wild_pats simple_rhs placeHolderType loc)
+ simple_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
+ (HsLit (HsStringPrim (mkFastString (stringToUtf8 error_msg))))
error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
-
-mkDefMethRhs is_inst_decl clas inst_tys sel_id loc GenDefMeth
+ -- 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 = [WildPatIn | 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)
- checkTc (not is_inst_decl || simple_inst)
- (badGenericInstance sel_id clas) `thenTc_`
-
+ ASSERT( isInstDecl origin ) -- We never get here from a class decl
+
+ checkTc (isJust maybe_tycon)
+ (badGenericInstance sel_id (notSimple inst_tys)) `thenTc_`
+ checkTc (isJust (tyConGenInfo tycon))
+ (badGenericInstance sel_id (notGeneric tycon)) `thenTc_`
+
ioToTc (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenNF_Tc_`
returnTc rhs
where
-- case we require that the instance decl is for a single-parameter
-- type class with type variable arguments:
-- instance (...) => C (T a b)
- simple_inst = maybeToBool maybe_tycon
clas_tyvar = head (classTyVars clas)
Just tycon = maybe_tycon
maybe_tycon = case inst_tys of
- [ty] -> case splitTyConApp_maybe ty of
- Just (tycon, arg_tys) | all isTyVarTy arg_tys -> Just tycon
- other -> Nothing
+ [ty] -> case tcSplitTyConApp_maybe ty of
+ Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon
+ other -> Nothing
other -> Nothing
+
+isInstDecl InstanceDeclOrigin = True
+isInstDecl ClassDeclOrigin = False
\end{code}
find_prags sel_name meth_name [] = []
find_prags sel_name meth_name (SpecSig name ty loc : prags)
| name == sel_name = SpecSig meth_name ty loc : find_prags sel_name meth_name prags
-find_prags sel_name meth_name (InlineSig name phase loc : prags)
- | name == sel_name = InlineSig meth_name phase loc : find_prags sel_name meth_name prags
-find_prags sel_name meth_name (NoInlineSig name phase loc : prags)
- | name == sel_name = NoInlineSig meth_name phase loc : find_prags sel_name meth_name prags
+find_prags sel_name meth_name (InlineSig sense name phase loc : prags)
+ | name == sel_name = InlineSig sense meth_name phase loc : find_prags sel_name meth_name prags
find_prags sel_name meth_name (prag:prags) = find_prags sel_name meth_name prags
\end{code}
Contexts and errors
~~~~~~~~~~~~~~~~~~~
\begin{code}
-classArityErr class_name
- = ptext SLIT("Too many parameters for class") <+> quotes (ppr class_name)
-
-superClassErr clas sc
- = ptext SLIT("Illegal superclass constraint") <+> quotes (ppr sc)
- <+> ptext SLIT("in declaration for class") <+> quotes (ppr clas)
-
defltMethCtxt clas
= ptext SLIT("When checking the default methods for class") <+> quotes (ppr clas)
= hsep [ptext SLIT("Class"), quotes (ppr clas),
ptext SLIT("does not have a method"), quotes (ppr op)]
-omittedMethodWarn sel_id clas
- = sep [ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id),
- ptext SLIT("in an instance declaration for") <+> quotes (ppr clas)]
-
-badGenericMethodType op op_ty
- = hang (ptext SLIT("Generic method type is too complex"))
- 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
- ptext SLIT("You can only use type variables, arrows, and tuples")])
+omittedMethodWarn sel_id
+ = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id)
-badGenericInstance sel_id clas
+badGenericInstance sel_id because
= sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id),
- ptext SLIT("because the instance declaration is not for a simple type (T a b c)"),
- ptext SLIT("(where T is a derivable type constructor)"),
- ptext SLIT("in an instance declaration for") <+> quotes (ppr clas)]
+ 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")]
mixedGenericErr op
= ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op)
-
-genericMultiParamErr clas
- = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
- ptext SLIT("cannot have generic methods")
\end{code}
projects / ghc-hetmet.git / blobdiff