\begin{code}
module TcClassDcl ( tcClassDecl1, tcClassDecls2, mkImplicitClassBinds,
- tcMethodBind, checkFromThisClass
+ tcMethodBind, badMethodErr
) where
#include "HsVersions.h"
import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..),
HsExpr(..), HsLit(..), HsType(..), HsPred(..),
mkSimpleMatch, andMonoBinds, andMonoBindList,
- isClassDecl, isClassOpSig, isPragSig, collectMonoBinders
+ isClassDecl, isClassOpSig, isPragSig,
+ fromClassDeclNameList, tyClDeclName
)
-import BasicTypes ( TopLevelFlag(..), RecFlag(..) )
+import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..), EP(..) )
import RnHsSyn ( RenamedTyClDecl,
RenamedClassOpSig, RenamedMonoBinds,
- RenamedContext, RenamedHsDecl, RenamedSig
+ RenamedContext, RenamedHsDecl, RenamedSig,
+ RenamedHsExpr, maybeGenericMatch
)
import TcHsSyn ( TcMonoBinds, idsToMonoBinds )
import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcSigTyVars )
import TcMonad
+import Generics ( mkGenericRhs, validGenericMethodType )
import PrelInfo ( nO_METHOD_BINDING_ERROR_ID )
+import Class ( classTyVars, classBigSig, classSelIds, classTyCon, Class, ClassOpItem,
+ DefMeth (..) )
import Bag ( bagToList )
-import Class ( classTyVars, classBigSig, classSelIds, classTyCon, Class, ClassOpItem )
-import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods )
+import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods, opt_PprStyle_Debug )
import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId )
import DataCon ( mkDataCon, notMarkedStrict )
import Id ( Id, idType, idName )
-import Name ( Name, nameOccName, isLocallyDefined, NamedThing(..) )
+import Name ( Name, nameOccName, isLocallyDefined, NamedThing(..), mkSysLocalName,
+ NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv, nameEnvElts )
import NameSet ( NameSet, mkNameSet, elemNameSet, emptyNameSet )
import Outputable
-import Type ( Type, ClassContext, mkTyVarTys, mkDictTys, mkSigmaTy, mkClassPred )
+import Type ( Type, ClassContext, mkTyVarTys, mkDictTys, mkSigmaTy, mkClassPred,
+ splitTyConApp_maybe, isTyVarTy
+ )
import Var ( TyVar )
import VarSet ( mkVarSet, emptyVarSet )
-import Maybes ( seqMaybe )
+import ErrUtils ( dumpIfSet )
+import Util ( count )
+import Maybes ( seqMaybe, maybeToBool, orElse )
\end{code}
tcClassDecl1 rec_env
(ClassDecl context class_name
tyvar_names fundeps class_sigs def_methods pragmas
- tycon_name datacon_name datacon_wkr_name sc_sel_names src_loc)
+ 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
tcLookupTy class_name `thenTc` \ (AClass clas) ->
let
- tyvars = classTyVars clas
- dm_bndrs_w_locs = bagToList (collectMonoBinders def_methods)
- dm_bndr_set = mkNameSet (map fst dm_bndrs_w_locs)
+ 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
in
- tcExtendTyVarEnv tyvars $
+ tcExtendTyVarEnv tyvars $
+
+ -- CHECK THAT THE DEFAULT BINDINGS ARE LEGAL
+ checkDefaultBinds clas op_names def_methods `thenTc` \ dm_info ->
+ checkGenericClassIsUnary clas dm_info `thenTc_`
-- CHECK THE CONTEXT
- tcSuperClasses class_name clas
- context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) ->
+ tcSuperClasses clas context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) ->
-- CHECK THE CLASS SIGNATURES,
- mapTc (tcClassSig rec_env dm_bndr_set clas tyvars)
- (filter isClassOpSig class_sigs) `thenTc` \ sig_stuff ->
+ mapTc (tcClassSig rec_env clas tyvars dm_info) op_sigs `thenTc` \ sig_stuff ->
-- MAKE THE CLASS DETAILS
let
dict_component_tys = sc_tys ++ op_tys
dict_con = mkDataCon datacon_name
- [notMarkedStrict | _ <- dict_component_tys]
- [{- No labelled fields -}]
- tyvars
- [{-No context-}]
- [{-No existential tyvars-}] [{-Or context-}]
- dict_component_tys
- (classTyCon clas)
- dict_con_id dict_wrap_id
+ [notMarkedStrict | _ <- dict_component_tys]
+ [{- No labelled fields -}]
+ tyvars
+ [{-No context-}]
+ [{-No existential tyvars-}] [{-Or context-}]
+ dict_component_tys
+ (classTyCon clas)
+ dict_con_id dict_wrap_id
dict_con_id = mkDataConId datacon_wkr_name dict_con
dict_wrap_id = mkDataConWrapId dict_con
\end{code}
\begin{code}
-tcSuperClasses :: Name -> Class
+checkDefaultBinds :: Class -> [Name] -> RenamedMonoBinds -> TcM s (NameEnv (DefMeth Name))
+ -- 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
+
+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 (FunMonoBind op _ matches loc)
+ = tcAddSrcLoc loc $
+
+ -- Check that the op is from this class
+ 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))
+
+ 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]
+\end{code}
+
+
+\begin{code}
+tcSuperClasses :: Class
-> RenamedContext -- class context
-> [Name] -- Names for superclass selectors
-> TcM s (ClassContext, -- the superclass context
[Id]) -- superclass selector Ids
-tcSuperClasses class_name clas context sc_sel_names
+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.
where
check_constraint sc@(HsPClass c tys)
- = checkTc (all is_tyvar tys) (superClassErr class_name sc)
+ = checkTc (all is_tyvar tys) (superClassErr clas sc)
is_tyvar (HsTyVar _) = True
is_tyvar other = False
-tcClassSig :: ValueEnv -- Knot tying only!
- -> NameSet -- Names bound in the default-method bindings
+tcClassSig :: ValueEnv -- Knot tying only!
-> Class -- ...ditto...
-> [TyVar] -- The class type variable, used for error check only
+ -> NameEnv (DefMeth Name) -- Info about default methods
-> RenamedClassOpSig
-> TcM s (Type, -- Type of the method
ClassOpItem) -- Selector Id, default-method Id, True if explicit default binding
+-- This warrants an explanation: we need to separate generic
+-- default methods and default methods later on in the compiler
+-- so we distinguish them in checkDefaultBinds, and pass this knowledge in the
+-- Class.DefMeth data structure.
-tcClassSig rec_env dm_bind_names clas clas_tyvars
- (ClassOpSig op_name maybe_dm_stuff op_ty src_loc)
+tcClassSig rec_env clas clas_tyvars dm_info
+ (ClassOpSig op_name maybe_dm op_ty src_loc)
= tcAddSrcLoc src_loc $
-- Check the type signature. NB that the envt *already has*
-- Build the selector id and default method id
sel_id = mkDictSelId op_name clas
+
+ dm_info_name = maybe_dm `orElse` lookupNameEnv dm_info op_name `orElse` NoDefMeth
+
+ 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
in
- (case maybe_dm_stuff of
- Nothing -> -- Source-file class declaration
- newDefaultMethodName op_name src_loc `thenNF_Tc` \ dm_name ->
- returnNF_Tc (mkDefaultMethodId dm_name clas global_ty, op_name `elemNameSet` dm_bind_names)
-
- Just (dm_name, explicit_dm) -> -- Interface-file class decl
- let
- dm_id = mkDefaultMethodId dm_name clas global_ty
- in
- returnNF_Tc (tcAddImportedIdInfo rec_env dm_id, explicit_dm)
- ) `thenNF_Tc` \ (dm_id, explicit_dm) ->
-
- returnTc (local_ty, (sel_id, dm_id, explicit_dm))
+ -- 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}
%* *
%************************************************************************
-The purpose of pass 2 is
-\begin{enumerate}
-\item
-to beat on the explicitly-provided default-method decls (if any),
-using them to produce a complete set of default-method decls.
-(Omitted ones elicit an error message.)
-\item
-to produce a definition for the selector function for each method
+@mkImplicitClassBinds@ produces a binding for the selector function for each method
and superclass dictionary.
-\end{enumerate}
-
-Pass~2 only applies to locally-defined class declarations.
-
-The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to
-each local class decl.
-
-\begin{code}
-tcClassDecls2 :: [RenamedHsDecl]
- -> NF_TcM s (LIE, TcMonoBinds)
-
-tcClassDecls2 decls
- = foldr combine
- (returnNF_Tc (emptyLIE, EmptyMonoBinds))
- [tcClassDecl2 cls_decl | TyClD cls_decl <- decls, isClassDecl cls_decl]
- where
- combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
- tc2 `thenNF_Tc` \ (lie2, binds2) ->
- returnNF_Tc (lie1 `plusLIE` lie2,
- binds1 `AndMonoBinds` binds2)
-\end{code}
-
-@tcClassDecl2@ is the business end of things.
-
-\begin{code}
-tcClassDecl2 :: RenamedTyClDecl -- The class declaration
- -> NF_TcM s (LIE, TcMonoBinds)
-
-tcClassDecl2 (ClassDecl context class_name
- tyvar_names _ class_sigs default_binds pragmas _ _ _ _ src_loc)
-
- | not (isLocallyDefined class_name)
- = returnNF_Tc (emptyLIE, EmptyMonoBinds)
-
- | otherwise -- It is locally defined
- = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
- tcAddSrcLoc src_loc $
- tcLookupTy class_name `thenNF_Tc` \ (AClass clas) ->
- tcDefaultMethodBinds clas default_binds class_sigs
-\end{code}
\begin{code}
mkImplicitClassBinds :: [Class] -> NF_TcM s ([Id], TcMonoBinds)
| otherwise = EmptyMonoBinds
\end{code}
+
+
%************************************************************************
%* *
\subsection[Default methods]{Default methods}
dfoo_list
\end{verbatim}
+The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to
+each local class decl.
+
\begin{code}
-tcDefaultMethodBinds
- :: Class
- -> RenamedMonoBinds
- -> [RenamedSig]
- -> TcM s (LIE, TcMonoBinds)
-
-tcDefaultMethodBinds clas default_binds sigs
- = -- Check that the default bindings come from this class
- checkFromThisClass clas default_binds `thenNF_Tc_`
-
- -- Do each default method separately
- -- For Hugs compatibility we make a default-method for every
- -- class op, regardless of whether or not the programmer supplied an
- -- explicit default decl for the class. GHC will actually never
- -- call the default method for such operations, because it'll whip up
- -- a more-informative default method at each instance decl.
- mapAndUnzipTc tc_dm op_items `thenTc` \ (defm_binds, const_lies) ->
+tcClassDecls2 :: [RenamedHsDecl] -> NF_TcM s (LIE, TcMonoBinds)
- returnTc (plusLIEs const_lies, andMonoBindList defm_binds)
+tcClassDecls2 decls
+ = foldr combine
+ (returnNF_Tc (emptyLIE, EmptyMonoBinds))
+ [tcClassDecl2 cls_decl | TyClD cls_decl <- decls,
+ isClassDecl cls_decl,
+ isLocallyDefined (tyClDeclName cls_decl)]
where
- prags = filter isPragSig sigs
+ combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
+ tc2 `thenNF_Tc` \ (lie2, binds2) ->
+ returnNF_Tc (lie1 `plusLIE` lie2,
+ binds1 `AndMonoBinds` binds2)
+\end{code}
- (tyvars, _, _, op_items) = classBigSig clas
+@tcClassDecl2@ generates bindings for polymorphic default methods
+(generic default methods have by now turned into instance declarations)
- origin = ClassDeclOrigin
+\begin{code}
+tcClassDecl2 :: RenamedTyClDecl -- The class declaration
+ -> NF_TcM s (LIE, TcMonoBinds)
+
+tcClassDecl2 (ClassDecl context class_name
+ tyvar_names _ sigs default_binds pragmas _ src_loc)
+ = -- A locally defined class
+ recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
+ tcAddSrcLoc src_loc $
+ tcLookupTy class_name `thenNF_Tc` \ (AClass clas) ->
+
+ -- We make a separate binding for each default method.
+ -- At one time I used a single AbsBinds for all of them, thus
+ -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... }
+ -- But that desugars into
+ -- ds = \d -> (..., ..., ...)
+ -- 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
+ prags = filter isPragSig sigs
+ tc_dm = tcDefMeth clas tyvars default_binds prags
+ in
+ mapAndUnzipTc tc_dm op_items `thenTc` \ (defm_binds, const_lies) ->
- -- We make a separate binding for each default method.
- -- At one time I used a single AbsBinds for all of them, thus
- -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... }
- -- But that desugars into
- -- ds = \d -> (..., ..., ...)
- -- 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
+ returnTc (plusLIEs const_lies, andMonoBindList defm_binds)
- tc_dm op_item@(_, dm_id, _)
- = tcInstTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) ->
- let
- theta = [(mkClassPred clas inst_tys)]
- in
- newDicts origin theta `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
- let
- avail_insts = this_dict
- in
- tcExtendTyVarEnvForMeths tyvars clas_tyvars (
- tcMethodBind clas origin clas_tyvars inst_tys theta
- default_binds prags False
- op_item
- ) `thenTc` \ (defm_bind, insts_needed, (_, local_dm_id)) ->
+
+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
+ -- 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 binds_in prags op_item@(_, DefMeth dm_id)
+ = tcInstTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) ->
+ let
+ theta = [(mkClassPred clas inst_tys)]
+ in
+ newDicts origin theta `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+
+ 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)) ->
- tcAddErrCtxt (defltMethCtxt clas) $
+ 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' ->
+ -- 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
- (ptext SLIT("class") <+> ppr clas)
- (mkVarSet clas_tyvars')
- avail_insts
- insts_needed `thenTc` \ (const_lie, dict_binds) ->
+ -- Check the context
+ tcSimplifyAndCheck
+ (ptext SLIT("class") <+> ppr clas)
+ (mkVarSet clas_tyvars')
+ this_dict
+ insts_needed `thenTc` \ (const_lie, dict_binds) ->
- let
- full_bind = AbsBinds
- clas_tyvars'
- [this_dict_id]
- [(clas_tyvars', dm_id, local_dm_id)]
- emptyNameSet -- No inlines (yet)
- (dict_binds `andMonoBinds` defm_bind)
- in
- returnTc (full_bind, const_lie)
-\end{code}
-
-\begin{code}
-checkFromThisClass :: Class -> RenamedMonoBinds -> NF_TcM s ()
-checkFromThisClass clas mbinds
- = mapNF_Tc check_from_this_class bndrs_w_locs `thenNF_Tc_`
- returnNF_Tc ()
+ let
+ full_bind = AbsBinds
+ clas_tyvars'
+ [this_dict_id]
+ [(clas_tyvars', dm_id, local_dm_id)]
+ emptyNameSet -- No inlines (yet)
+ (dict_binds `andMonoBinds` defm_bind)
+ in
+ returnTc (full_bind, const_lie)
where
- check_from_this_class (bndr, loc)
- | nameOccName bndr `elem` sel_names = returnNF_Tc ()
- | otherwise = tcAddSrcLoc loc $
- addErrTc (badMethodErr bndr clas)
- sel_names = map getOccName (classSelIds clas)
- bndrs_w_locs = bagToList (collectMonoBinders mbinds)
+ origin = ClassDeclOrigin
\end{code}
+
+%************************************************************************
+%* *
+\subsection{Typechecking a method}
+%* *
+%************************************************************************
+
@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
-> TcM s (TcMonoBinds, LIE, (LIE, TcId))
tcMethodBind clas origin inst_tyvars inst_tys inst_theta
- meth_binds prags is_inst_decl
- (sel_id, dm_id, explicit_dm)
- = tcGetSrcLoc `thenNF_Tc` \ loc ->
-
- newMethod origin sel_id inst_tys `thenNF_Tc` \ meth@(_, meth_id) ->
- mkTcSig meth_id loc `thenNF_Tc` \ sig_info ->
-
- let
- meth_name = idName meth_id
- maybe_user_bind = find_bind meth_name meth_binds
-
- no_user_bind = case maybe_user_bind of {Nothing -> True; other -> False}
-
- meth_bind = case maybe_user_bind of
- Just bind -> bind
- Nothing -> mk_default_bind meth_name loc
-
- meth_prags = find_prags meth_name prags
- in
-
- -- Warn if no method binding, only if -fwarn-missing-methods
- warnTc (is_inst_decl && opt_WarnMissingMethods && no_user_bind && not explicit_dm)
- (omittedMethodWarn sel_id clas) `thenNF_Tc_`
-
- -- 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
- 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)
- where
- sig_msg = ptext SLIT("When checking the expected type for class method") <+> ppr sel_name
-
- sel_name = idName sel_id
-
- -- The renamer just puts the selector ID as the binder in the method binding
- -- but we must use the method name; so we substitute it here. Crude but simple.
- find_bind meth_name (FunMonoBind op_name fix matches loc)
- | op_name == sel_name = Just (FunMonoBind meth_name fix matches loc)
- find_bind meth_name (AndMonoBinds b1 b2)
- = find_bind meth_name b1 `seqMaybe` find_bind meth_name b2
- find_bind meth_name other = Nothing -- Default case
-
-
- -- Find the prags for this method, and replace the
- -- selector name with the method name
- find_prags meth_name [] = []
- find_prags meth_name (SpecSig name ty loc : prags)
- | name == sel_name = SpecSig meth_name ty loc : find_prags meth_name prags
- find_prags meth_name (InlineSig name phase loc : prags)
- | name == sel_name = InlineSig meth_name phase loc : find_prags meth_name prags
- find_prags meth_name (NoInlineSig name phase loc : prags)
- | name == sel_name = NoInlineSig meth_name phase loc : find_prags meth_name prags
- find_prags meth_name (prag:prags) = find_prags meth_name prags
-
- mk_default_bind local_meth_name loc
- = FunMonoBind local_meth_name
- False -- Not infix decl
- [mkSimpleMatch [] (default_expr loc) Nothing loc]
- loc
-
- default_expr loc
- | explicit_dm = HsVar (getName dm_id) -- There's a default method
- | otherwise = error_expr loc -- No default method
-
- error_expr loc = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
- (HsLit (HsString (_PK_ (error_msg loc))))
-
- error_msg loc = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
+ meth_binds prags is_inst_decl (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 ->
+ let
+ 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 ->
+ returnTc (FunMonoBind meth_name False -- Not infix decl
+ [mkSimpleMatch [] rhs Nothing 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
+ 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)
+
+ -- 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)
+ = -- An polymorphic default method
+ returnTc (HsVar (idName dm_id))
+
+mkDefMethRhs is_inst_decl 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_`
+ returnTc error_rhs
+ where
+ error_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
+ (HsLit (HsString (_PK_ error_msg)))
+ error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
+
+
+mkDefMethRhs is_inst_decl 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_`
+
+ ioToTc (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenNF_Tc_`
+ returnTc rhs
+ where
+ rhs = mkGenericRhs sel_id clas_tyvar tycon
+
+ stuff = vcat [ppr clas <+> ppr inst_tys,
+ nest 4 (ppr sel_id <+> equals <+> ppr rhs)]
+
+ -- 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)
+ 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
+ other -> Nothing
+\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 (FunMonoBind op_name fix matches loc)
+ | op_name == sel_name = Just (FunMonoBind meth_name fix matches loc)
+find_bind sel_name meth_name (AndMonoBinds b1 b2)
+ = find_bind sel_name meth_name b1 `seqMaybe` find_bind sel_name meth_name b2
+find_bind sel_name meth_name other = Nothing -- Default case
+
+ -- Find the prags for this method, and replace the
+ -- selector name with the method name
+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 (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 class_name sc
+superClassErr clas sc
= ptext SLIT("Illegal superclass constraint") <+> quotes (ppr sc)
- <+> ptext SLIT("in declaration for class") <+> quotes (ppr class_name)
+ <+> ptext SLIT("in declaration for class") <+> quotes (ppr clas)
-defltMethCtxt class_name
- = ptext SLIT("When checking the default methods for class") <+> quotes (ppr class_name)
+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 bndr clas
+badMethodErr clas op
= hsep [ptext SLIT("Class"), quotes (ppr clas),
- ptext SLIT("does not have a method"), quotes (ppr bndr)]
+ 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")])
+
+badGenericInstance sel_id clas
+ = 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)]
+
+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