%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcClassDcl]{Typechecking class declarations}
\begin{code}
+module TcClassDcl ( tcClassDecl1, checkValidClass, tcClassDecls2,
+ tcMethodBind, badMethodErr
+ ) where
+
#include "HsVersions.h"
-module TcClassDcl (
- tcClassDecl1, tcClassDecls2
- ) where
-
-IMP_Ubiq()
-
-import HsSyn ( ClassDecl(..), HsBinds(..), Bind(..), MonoBinds(..),
- Match(..), GRHSsAndBinds(..), GRHS(..), HsExpr(..),
- HsLit(..), OutPat(..), Sig(..), PolyType(..), MonoType,
- Stmt, Qualifier, ArithSeqInfo, InPat, Fake )
-import HsPragmas ( ClassPragmas(..) )
-import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..),
- RenamedClassOpSig(..), RenamedMonoBinds(..),
- RenamedGenPragmas(..), RenamedContext(..),
- RnName{-instance Uniquable-}
+import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..),
+ HsExpr(..), HsLit(..),
+ mkSimpleMatch, andMonoBinds, andMonoBindList,
+ isClassOpSig, isPragSig,
+ getClassDeclSysNames, placeHolderType
+ )
+import BasicTypes ( TopLevelFlag(..), RecFlag(..), StrictnessMark(..) )
+import RnHsSyn ( RenamedTyClDecl,
+ RenamedClassOpSig, RenamedMonoBinds,
+ RenamedSig, maybeGenericMatch
)
-import TcHsSyn ( TcIdOcc(..), TcHsBinds(..), TcMonoBinds(..), TcExpr(..),
- mkHsTyApp, mkHsTyLam, mkHsDictApp, mkHsDictLam, tcIdType )
-
-import Inst ( Inst, InstOrigin(..), LIE(..), emptyLIE, plusLIE, newDicts )
-import TcEnv ( tcLookupClass, tcLookupTyVar, tcLookupTyCon, newLocalIds)
-import TcInstDcls ( processInstBinds, newMethodId )
-import TcKind ( TcKind )
-import TcKind ( unifyKind )
-import TcMonad hiding ( rnMtoTcM )
-import TcMonoType ( tcPolyType, tcMonoType, tcContext )
-import TcSimplify ( tcSimplifyAndCheck )
-import TcType ( TcType(..), TcTyVar(..), tcInstType, tcInstSigTyVars, tcInstSigType )
-
-import Bag ( foldBag, unionManyBags )
-import Class ( GenClass, mkClass, mkClassOp, classBigSig,
- classOps, classOpString, classOpLocalType,
- classOpTagByString
+import TcHsSyn ( TcMonoBinds )
+
+import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs,
+ instToId, newDicts, newMethod )
+import TcEnv ( RecTcEnv, TyThingDetails(..), tcAddImportedIdInfo,
+ tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars,
+ tcExtendLocalValEnv, tcExtendTyVarEnv
)
-import Id ( mkSuperDictSelId, mkMethodSelId, mkDefaultMethodId,
- idType )
-import IdInfo ( noIdInfo )
-import Name ( isLocallyDefined, origName, getLocalName )
-import PrelVals ( nO_DEFAULT_METHOD_ERROR_ID )
-import PprStyle
-import Pretty
-import PprType ( GenType, GenTyVar, GenClassOp )
-import SpecEnv ( SpecEnv(..) )
-import SrcLoc ( mkGeneratedSrcLoc )
-import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy,
- mkForAllTy, mkSigmaTy, splitSigmaTy)
-import TysWiredIn ( stringTy )
-import TyVar ( mkTyVarSet, GenTyVar )
-import Unique ( Unique )
-import Util
-
-
--- import TcPragmas ( tcGenPragmas, tcClassOpPragmas )
-tcGenPragmas ty id ps = returnNF_Tc noIdInfo
-tcClassOpPragmas ty sel def spec ps = returnNF_Tc (noIdInfo, noIdInfo)
+import TcBinds ( tcBindWithSigs, tcSpecSigs )
+import TcMonoType ( tcHsType, tcHsTheta, checkSigTyVars, sigCtxt, mkTcSig )
+import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
+import TcMType ( tcInstSigTyVars, checkValidTheta, checkValidType, SourceTyCtxt(..), UserTypeCtxt(..) )
+import TcType ( Type, TyVarDetails(..), TcType, TcThetaType, TcTyVar,
+ mkSigmaTy, mkTyVarTys, mkPredTys, mkClassPred,
+ tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitSigmaTy
+ )
+import TcMonad
+import Generics ( mkGenericRhs, validGenericMethodType )
+import PrelInfo ( nO_METHOD_BINDING_ERROR_ID )
+import Class ( classTyVars, classBigSig, classTyCon, className,
+ Class, ClassOpItem, DefMeth (..) )
+import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId )
+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 Var ( TyVar )
+import VarSet ( mkVarSet, emptyVarSet )
+import CmdLineOpts
+import ErrUtils ( dumpIfSet )
+import Util ( count, isSingleton, lengthIs, equalLength )
+import Maybes ( seqMaybe, maybeToBool )
\end{code}
Death to "ExpandingDicts".
+%************************************************************************
+%* *
+\subsection{Type checking}
+%* *
+%************************************************************************
+
\begin{code}
-tcClassDecl1 rec_inst_mapper
- (ClassDecl context class_name
- tyvar_name class_sigs def_methods pragmas src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (classDeclCtxt class_name) $
-
- -- LOOK THINGS UP IN THE ENVIRONMENT
- tcLookupClass class_name `thenNF_Tc` \ (class_kind, rec_class) ->
- tcLookupTyVar tyvar_name `thenNF_Tc` \ (tyvar_kind, rec_tyvar) ->
+
+tcClassDecl1 :: RecTcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails)
+tcClassDecl1 rec_env
+ (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
- (rec_class_inst_env, rec_class_op_inst_fn) = rec_inst_mapper rec_class
+ tyvars = classTyVars clas
+ op_sigs = filter isClassOpSig class_sigs
+ op_names = [n | ClassOpSig n _ _ _ <- op_sigs]
+ (_, datacon_name, datacon_wkr_name, sc_sel_names) = getClassDeclSysNames sys_names
in
+ tcExtendTyVarEnv tyvars $
- -- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND
- unifyKind class_kind tyvar_kind `thenTc_`
-
+ checkDefaultBinds clas op_names def_methods `thenTc` \ mb_dm_env ->
+
-- CHECK THE CONTEXT
- tcClassContext rec_class rec_tyvar context pragmas
- `thenTc` \ (scs, 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_class rec_tyvar rec_class_op_inst_fn) class_sigs
- `thenTc` \ sig_stuff ->
+ mapTc (tcClassSig rec_env clas tyvars mb_dm_env) op_sigs `thenTc` \ sig_stuff ->
- -- MAKE THE CLASS OBJECT ITSELF
+ -- MAKE THE CLASS DETAILS
let
- (ops, op_sel_ids, defm_ids) = unzip3 sig_stuff
- clas = mkClass (uniqueOf class_name) (getName class_name) rec_tyvar
- scs sc_sel_ids ops op_sel_ids defm_ids
- rec_class_inst_env
+ (op_tys, op_items) = unzip sig_stuff
+ 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]
+ [{- 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
in
- returnTc clas
+ returnTc (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con)
\end{code}
-
- let
- clas_ty = mkTyVarTy clas_tyvar
- dict_component_tys = [mkDictTy sc clas_ty | sc <- scs] ++
- [classOpLocalType op | op <- ops])
- new_or_data = case dict_component_tys of
- [_] -> NewType
- other -> DataType
-
- dict_con_id = mkDataCon class_name
- [NotMarkedStrict]
- [{- No labelled fields -}]
- [clas_tyvar]
- [{-No context-}]
- dict_component_tys
- tycon
-
- tycon = mkDataTyCon class_name
- (tyVarKind rec_tyvar `mkArrowKind` mkBoxedTypeKind)
- [rec_tyvar]
- [{- Empty context -}]
- [dict_con_id]
- [{- No derived classes -}]
- new_or_data
- in
-
-
\begin{code}
-tcClassContext :: Class -> TyVar
- -> RenamedContext -- class context
- -> RenamedClassPragmas -- pragmas for superclasses
- -> TcM s ([Class], -- the superclasses
- [Id]) -- superclass selector Ids
-
-tcClassContext rec_class rec_tyvar context pragmas
- = -- Check the context.
- -- The renamer has already checked that the context mentions
- -- only the type variable of the class decl.
- tcContext context `thenTc` \ theta ->
- let
- super_classes = [ supers | (supers, _) <- theta ]
- in
-
- -- Make super-class selector ids
- mapTc (mk_super_id rec_class)
- (super_classes `zip` maybe_pragmas) `thenTc` \ sc_sel_ids ->
- -- NB: we worry about matching list lengths below
-
- -- Done
- returnTc (super_classes, sc_sel_ids)
-
+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
+
+ -- But do all this only for source binds
+
+checkDefaultBinds clas ops Nothing
+ = returnTc Nothing
+
+checkDefaultBinds clas ops (Just mbs)
+ = go mbs `thenTc` \ dm_env ->
+ returnTc (Just dm_env)
where
- mk_super_id rec_class (super_class, maybe_pragma)
- = fixTc ( \ rec_super_id ->
- tcGetUnique `thenNF_Tc` \ uniq ->
-
- -- GET THE PRAGMA INFO FOR THE SUPERCLASS
- (case maybe_pragma of
- Nothing -> returnNF_Tc noIdInfo
- Just prag -> tcGenPragmas Nothing{-ty unknown-} rec_super_id prag
- ) `thenNF_Tc` \ id_info ->
- let
- rec_tyvar_ty = mkTyVarTy rec_tyvar
- ty = mkForAllTy rec_tyvar $
- mkFunTy (mkDictTy rec_class rec_tyvar_ty)
- (mkDictTy super_class rec_tyvar_ty)
- in
- -- BUILD THE SUPERCLASS ID
- returnTc (mkSuperDictSelId uniq rec_class super_class ty id_info)
- )
-
- maybe_pragmas :: [Maybe RenamedGenPragmas]
- maybe_pragmas = case pragmas of
- NoClassPragmas -> repeat Nothing
- SuperDictPragmas prags -> ASSERT(length prags == length context)
- map Just prags
- -- If there are any pragmas there should
- -- be one for each superclass
-
-
-
-tcClassSig :: Class -- Knot tying only!
- -> TyVar -- The class type variable, used for error check only
- -> (ClassOp -> SpecEnv) -- Ditto; the spec info for the class ops
- -> RenamedClassOpSig
- -> TcM s (ClassOp, -- class op
- Id, -- selector id
- Id) -- default-method ids
-
-tcClassSig rec_clas rec_clas_tyvar rec_classop_spec_fn
- (ClassOpSig op_name
- op_ty
- pragmas src_loc)
- = tcAddSrcLoc src_loc $
- fixTc ( \ ~(_, rec_sel_id, rec_defm_id) -> -- Knot for pragmas
-
- -- Check the type signature. NB that the envt *already has*
- -- bindings for the type variables; see comments in TcTyAndClassDcls.
-
- -- NB: Renamer checks that the class type variable is mentioned in local_ty,
- -- and that it is not constrained by theta
- tcPolyType op_ty `thenTc` \ local_ty ->
- let
- global_ty = mkSigmaTy [rec_clas_tyvar]
- [(rec_clas, mkTyVarTy rec_clas_tyvar)]
- local_ty
- class_op_nm = getLocalName op_name
- class_op = mkClassOp class_op_nm
- (classOpTagByString rec_clas{-yeeps!-} class_op_nm)
- local_ty
- in
+ go EmptyMonoBinds = returnTc emptyNameEnv
- -- Munch the pragmas
- tcClassOpPragmas
- global_ty
- rec_sel_id rec_defm_id
- (rec_classop_spec_fn class_op)
- pragmas `thenNF_Tc` \ (op_info, defm_info) ->
+ go (AndMonoBinds b1 b2)
+ = go b1 `thenTc` \ dm_info1 ->
+ go b2 `thenTc` \ dm_info2 ->
+ returnTc (dm_info1 `plusNameEnv` dm_info2)
- -- Build the selector id and default method id
- tcGetUnique `thenNF_Tc` \ d_uniq ->
- let
- op_uniq = uniqueOf op_name
- sel_id = mkMethodSelId op_uniq rec_clas class_op global_ty op_info
- defm_id = mkDefaultMethodId d_uniq rec_clas class_op False global_ty defm_info
- -- ToDo: improve the "False"
- in
- returnTc (class_op, sel_id, defm_id)
- )
-\end{code}
+ go (FunMonoBind op _ matches loc)
+ = tcAddSrcLoc loc $
+ -- Check that the op is from this class
+ checkTc (op `elem` ops) (badMethodErr clas op) `thenTc_`
-%************************************************************************
-%* *
-\subsection[ClassDcl-pass2]{Class decls pass 2: default methods}
-%* *
-%************************************************************************
+ -- Check that all the defns ar generic, or none are
+ checkTc (all_generic || none_generic) (mixedGenericErr op) `thenTc_`
-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
-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 :: Bag RenamedClassDecl
- -> NF_TcM s (LIE s, TcHsBinds s)
-
-tcClassDecls2 decls
- = foldBag combine
- tcClassDecl2
- (returnNF_Tc (emptyLIE, EmptyBinds))
- decls
- where
- combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
- tc2 `thenNF_Tc` \ (lie2, binds2) ->
- returnNF_Tc (lie1 `plusLIE` lie2,
- binds1 `ThenBinds` binds2)
+ returnTc (unitNameEnv op all_generic)
+ where
+ n_generic = count (maybeToBool . maybeGenericMatch) matches
+ none_generic = n_generic == 0
+ all_generic = matches `lengthIs` n_generic
\end{code}
-@tcClassDecl2@ is the business end of things.
\begin{code}
-tcClassDecl2 :: RenamedClassDecl -- The class declaration
- -> NF_TcM s (LIE s, TcHsBinds s)
+tcClassSig :: RecTcEnv -- Knot tying only!
+ -> Class -- ...ditto...
+ -> [TyVar] -- The class type variable, used for error check only
+ -> 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
-tcClassDecl2 (ClassDecl context class_name
- tyvar_name class_sigs default_binds pragmas src_loc)
+-- 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.
- | not (isLocallyDefined class_name)
- = returnNF_Tc (emptyLIE, EmptyBinds)
+tcClassSig unf_env clas clas_tyvars maybe_dm_env
+ (ClassOpSig op_name sig_dm op_ty src_loc)
+ = tcAddSrcLoc src_loc $
- | otherwise -- It is locally defined
- = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $
- 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 ->
- -- Get the relevant class
- tcLookupClass class_name `thenNF_Tc` \ (_, clas) ->
let
- (tyvar, scs, sc_sel_ids, ops, op_sel_ids, defm_ids)
- = classBigSig clas
- in
- tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], _, _) ->
-
- -- Generate bindings for the selector functions
- buildSelectors clas tyvar clas_tyvar scs sc_sel_ids ops op_sel_ids
- `thenNF_Tc` \ sel_binds ->
- -- Ditto for the methods
- buildDefaultMethodBinds clas clas_tyvar defm_ids default_binds
- `thenTc` \ (const_insts, meth_binds) ->
-
- returnTc (const_insts, sel_binds `ThenBinds` meth_binds)
-\end{code}
+ theta = [mkClassPred clas (mkTyVarTys clas_tyvars)]
-%************************************************************************
-%* *
-\subsection[ClassDcl-bld-sels]{Building the selector functions for methods and superclasses}
-%* *
-%************************************************************************
-
-\begin{code}
-buildSelectors :: Class -- The class object
- -> TyVar -- Class type variable
- -> TcTyVar s -- Instantiated class type variable (TyVarTy)
- -> [Class] -> [Id] -- Superclasses and selectors
- -> [ClassOp] -> [Id] -- Class ops and selectors
- -> NF_TcM s (TcHsBinds s)
-
-buildSelectors clas clas_tyvar clas_tc_tyvar scs sc_sel_ids ops op_sel_ids
- =
- -- Make new Ids for the components of the dictionary
- let
- clas_tyvar_ty = mkTyVarTy clas_tc_tyvar
- mk_op_ty = tcInstType [(clas_tyvar, clas_tyvar_ty)] . classOpLocalType
- in
- mapNF_Tc mk_op_ty ops `thenNF_Tc` \ op_tys ->
- newLocalIds (map classOpString ops) op_tys `thenNF_Tc` \ method_ids ->
-
- newDicts ClassDeclOrigin
- [ (super_clas, clas_tyvar_ty)
- | super_clas <- scs ] `thenNF_Tc` \ (_,dict_ids) ->
+ -- Build the selector id and default method id
+ sel_id = mkDictSelId op_name clas
+ DefMeth dm_name = sig_dm
- newDicts ClassDeclOrigin
- [ (clas, clas_tyvar_ty) ] `thenNF_Tc` \ (_,[clas_dict]) ->
+ dm_info = case maybe_dm_env of
+ Nothing -> sig_dm
+ Just dm_env -> mk_src_dm_info dm_env
- -- Make suitable bindings for the selectors
- let
- mk_sel sel_id method_or_dict
- = mkSelBind sel_id clas_tc_tyvar clas_dict dict_ids method_ids method_or_dict
+ mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of
+ Nothing -> NoDefMeth
+ Just True -> GenDefMeth
+ Just False -> DefMeth dm_name
in
- listNF_Tc (zipWithEqual "mk_sel1" mk_sel op_sel_ids method_ids) `thenNF_Tc` \ op_sel_binds ->
- listNF_Tc (zipWithEqual "mk_sel2" mk_sel sc_sel_ids dict_ids) `thenNF_Tc` \ sc_sel_binds ->
-
- returnNF_Tc (SingleBind (
- NonRecBind (
- foldr AndMonoBinds
- (foldr AndMonoBinds EmptyMonoBinds op_sel_binds)
- sc_sel_binds
- )))
+ returnTc (local_ty, (sel_id, dm_info))
\end{code}
-%************************************************************************
-%* *
-\subsection[ClassDcl-misc]{Miscellaneous}
-%* *
-%************************************************************************
+checkValidClass is called once the mutually-recursive knot has been
+tied, so we can look at things freely.
-Make a selector expression for @sel_id@ from a dictionary @clas_dict@
-consisting of @dicts@ and @methods@.
-
-====================== OLD ============================
-We have to do a bit of jiggery pokery to get the type variables right.
-Suppose we have the class decl:
-\begin{verbatim}
- class Foo a where
- op1 :: Ord b => a -> b -> a
- op2 :: ...
-\end{verbatim}
-Then the method selector for \tr{op1} is like this:
-\begin{verbatim}
- op1_sel = /\a b -> \dFoo dOrd -> case dFoo of
- (op1_method,op2_method) -> op1_method b dOrd
-\end{verbatim}
-Note that the type variable for \tr{b} and the (Ord b) dictionary
-are lifted to the top lambda, and
-\tr{op1_method} is applied to them. This is preferable to the alternative:
-\begin{verbatim}
- op1_sel' = /\a -> \dFoo -> case dFoo of
- (op1_method,op2_method) -> op1_method
-\end{verbatim}
-because \tr{op1_sel'} then has the rather strange type
-\begin{verbatim}
- op1_sel' :: forall a. Foo a -> forall b. Ord b -> a -> b -> a
-\end{verbatim}
-whereas \tr{op1_sel} (the one we use) has the decent type
-\begin{verbatim}
- op1_sel :: forall a b. Foo a -> Ord b -> a -> b -> a
-\end{verbatim}
-========================= END OF OLD ===========================
-
-NEW COMMENT: instead we now go for op1_sel' above. Seems tidier and
-the rest of the compiler darn well ought to cope.
+\begin{code}
+checkValidClass :: Class -> TcM ()
+checkValidClass cls
+ = -- CHECK ARITY 1 FOR HASKELL 1.4
+ doptsTc Opt_GlasgowExts `thenTc` \ gla_exts ->
+ -- Check that the class is unary, unless GlaExs
+ checkTc (not (null tyvars)) (nullaryClassErr cls) `thenTc_`
+ checkTc (gla_exts || unary) (classArityErr cls) `thenTc_`
+ -- Check the super-classes
+ checkValidTheta (ClassSCCtxt (className cls)) theta `thenTc_`
-NOTE that we return a TcMonoBinds (which is later zonked) even though
-there's no real back-substitution to do. It's just simpler this way!
+ -- Check the class operations
+ mapTc_ check_op op_stuff `thenTc_`
-NOTE ALSO that the selector has no free type variables, so we
-don't bother to instantiate the class-op's local type; instead
-we just use the variables inside it.
+ -- 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 cls)
-\begin{code}
-mkSelBind :: Id -- the selector id
- -> TcTyVar s -> TcIdOcc s -- class tyvar and dict
- -> [TcIdOcc s] -> [TcIdOcc s] -- superclasses and methods in class dict
- -> TcIdOcc s -- the superclass/method being slected
- -> NF_TcM s (TcMonoBinds s)
-
-mkSelBind sel_id clas_tyvar clas_dict dicts methods method_or_dict@(TcId op)
- =
- -- sel_id = /\ clas_tyvar -> \ clas_dict ->
- -- case clas_dict of
- -- <dicts..methods> -> method_or_dict
-
- returnNF_Tc (VarMonoBind (RealId sel_id) (
- TyLam [clas_tyvar] (
- DictLam [clas_dict] (
- HsCase
- (HsVar clas_dict)
- ([PatMatch (DictPat dicts methods) (
- GRHSMatch (GRHSsAndBindsOut
- [OtherwiseGRHS
- (HsVar method_or_dict)
- mkGeneratedSrcLoc]
- EmptyBinds
- (idType op)))])
- mkGeneratedSrcLoc
- ))))
+ where
+ (tyvars, theta, _, op_stuff) = classBigSig cls
+ unary = isSingleton tyvars
+ no_generics = null [() | (_, GenDefMeth) <- op_stuff]
+
+ check_op (sel_id, dm)
+ = checkValidTheta SigmaCtxt (tail theta) `thenTc_`
+ -- The 'tail' removes the initial (C a) from the
+ -- class itself, leaving just the method type
+
+ checkValidType (FunSigCtxt op_name) tau `thenTc_`
+
+ -- Check that for a generic method, the type of
+ -- the method is sufficiently simple
+ checkTc (dm /= GenDefMeth || validGenericMethodType op_ty)
+ (badGenericMethodType op_name op_ty)
+ where
+ op_name = idName sel_id
+ op_ty = idType sel_id
+ (_,theta,tau) = tcSplitSigmaTy op_ty
\end{code}
defm.Foo.op1 :: forall a. Foo a => a -> Bool
defm.Foo.op1 = /\a -> \dfoo -> \x -> True
-====================== OLD ==================
-\begin{verbatim}
-defm.Foo.op2 :: forall a, b. (Foo a, Ord b) => a -> b -> b -> b
-defm.Foo.op2 = /\ a b -> \ dfoo dord -> \x y z ->
- if (op1 a dfoo x) && (< b dord y z) then y else z
-\end{verbatim}
-Notice that, like all ids, the foralls of defm.Foo.op2 are at the top.
-====================== END OF OLD ===================
-
-NEW:
-\begin{verbatim}
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}
dfoo_list
\end{verbatim}
+The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to
+each local class decl.
+
\begin{code}
-buildDefaultMethodBinds
- :: Class
- -> TcTyVar s
- -> [Id]
- -> RenamedMonoBinds
- -> TcM s (LIE s, TcHsBinds s)
-
-buildDefaultMethodBinds clas clas_tyvar
- default_method_ids default_binds
- = newDicts origin [(clas,inst_ty)] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
- mapAndUnzipNF_Tc mk_method default_method_ids `thenNF_Tc` \ (insts_s, local_defm_ids) ->
+tcClassDecls2 :: Module -> [RenamedTyClDecl] -> NF_TcM (LIE, TcMonoBinds, [Id])
+
+tcClassDecls2 this_mod decls
+ = foldr combine
+ (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, ids1) ->
+ tc2 `thenNF_Tc` \ (lie2, binds2, ids2) ->
+ returnNF_Tc (lie1 `plusLIE` lie2,
+ binds1 `AndMonoBinds` binds2,
+ ids1 ++ ids2)
+\end{code}
+
+@tcClassDecl2@ generates bindings for polymorphic default methods
+(generic default methods have by now turned into instance declarations)
+
+\begin{code}
+tcClassDecl2 :: RenamedTyClDecl -- The class declaration
+ -> NF_TcM (LIE, TcMonoBinds, [Id])
+
+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 ->
+
+ -- 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
- avail_insts = this_dict `plusLIE` unionManyBags insts_s -- Insts available
+ (tyvars, _, _, op_items) = classBigSig clas
+ prags = filter isPragSig sigs
+ tc_dm = tcDefMeth clas tyvars default_binds prags
in
- processInstBinds
- clas
- (makeClassDeclDefaultMethodRhs clas local_defm_ids)
- [clas_tyvar] -- Tyvars in scope
- avail_insts
- local_defm_ids
- default_binds `thenTc` \ (insts_needed, default_binds') ->
-
- tcSimplifyAndCheck
- (mkTyVarSet [clas_tyvar])
- avail_insts
- insts_needed `thenTc` \ (const_lie, dict_binds) ->
-
-
+ mapAndUnzip3Tc tc_dm op_items `thenTc` \ (defm_binds, const_lies, dm_ids_s) ->
+
+ 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, [])
+ -- 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@(sel_id, DefMeth dm_name)
+ = tcInstSigTyVars ClsTv tyvars `thenNF_Tc` \ clas_tyvars ->
let
- defm_binds = AbsBinds
- [clas_tyvar]
- [this_dict_id]
- (local_defm_ids `zip` map RealId default_method_ids)
- dict_binds
- (RecBind default_binds')
+ 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.
+
+ inst_tys = mkTyVarTys clas_tyvars
+ 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
in
- returnTc (const_lie, defm_binds)
+ 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_inst) ->
+
+ tcAddErrCtxt (defltMethCtxt clas) $
+
+ -- Check the context
+ tcSimplifyCheck
+ (ptext SLIT("class") <+> ppr clas)
+ clas_tyvars
+ [this_dict]
+ insts_needed `thenTc` \ (const_lie, dict_binds) ->
+
+ -- Simplification can do unification
+ checkSigTyVars clas_tyvars emptyVarSet `thenTc` \ clas_tyvars' ->
+
+ let
+ full_bind = AbsBinds
+ clas_tyvars'
+ [instToId this_dict]
+ [(clas_tyvars', local_dm_id, instToId local_dm_inst)]
+ emptyNameSet -- No inlines (yet)
+ (dict_binds `andMonoBinds` defm_bind)
+ in
+ returnTc (full_bind, const_lie, [dm_id])
where
- inst_ty = mkTyVarTy clas_tyvar
- mk_method defm_id = newMethodId defm_id inst_ty origin
origin = ClassDeclOrigin
\end{code}
-@makeClassDeclDefaultMethodRhs@ builds the default method for a
-class declaration when no explicit default method is given.
+
+
+%************************************************************************
+%* *
+\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
+tyvar sets.
\begin{code}
-makeClassDeclDefaultMethodRhs
+tcMethodBind
:: Class
- -> [TcIdOcc s]
- -> Int
- -> NF_TcM s (TcExpr s)
-
-makeClassDeclDefaultMethodRhs clas method_ids tag
- = -- Return the expression
- -- error ty "No default method for ..."
- -- The interesting thing is that method_ty is a for-all type;
- -- this is fun, although unusual in a type application!
-
- returnNF_Tc (HsApp (mkHsTyApp (HsVar (RealId nO_DEFAULT_METHOD_ERROR_ID)) [tcIdType method_id])
- (HsLitOut (HsString (_PK_ error_msg)) stringTy))
-
-{- OLD AND COMPLICATED
- tcInstSigType () `thenNF_Tc` \ method_ty ->
- let
- (tyvars, theta, tau) = splitSigmaTy method_ty
- in
- newDicts ClassDeclOrigin theta `thenNF_Tc` \ (lie, dict_ids) ->
-
- returnNF_Tc (mkHsTyLam tyvars (
- mkHsDictLam dict_ids (
- HsApp (mkHsTyApp (HsVar (RealId nO_DEFAULT_METHOD_ERROR_ID)) [tau])
- (HsLitOut (HsString (_PK_ error_msg)) stringTy))))
--}
-
+ -> InstOrigin
+ -> [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, Inst)
+
+tcMethodBind clas origin inst_tyvars inst_tys inst_theta
+ meth_binds prags is_inst_decl (sel_id, dm_info)
+ = tcGetSrcLoc `thenNF_Tc` \ loc ->
+ newMethod origin sel_id inst_tys `thenNF_Tc` \ meth ->
+ let
+ meth_id = instToId meth
+ 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
+ mkTcSig meth_id loc `thenNF_Tc` \ sig_info ->
+
+ -- 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 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)
+
+ -- 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_name)
+ = -- An polymorphic default method
+ returnTc (HsVar dm_name)
+
+mkDefMethRhs is_inst_decl clas inst_tys sel_id loc NoDefMeth
+ = -- No default method
+ -- Warn only if -fwarn-missing-methods
+ doptsTc Opt_WarnMissingMethods `thenNF_Tc` \ warn ->
+ warnTc (is_inst_decl && 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_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) `thenTc_`
+
+ ioToTc (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenNF_Tc_`
+ returnTc rhs
where
- (OrigName clas_mod clas_name) = origName "makeClassDeclDefaultMethodRhs" clas
+ 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 tcSplitTyConApp_maybe ty of
+ Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon
+ other -> Nothing
+ other -> Nothing
+\end{code}
- method_id = method_ids !! (tag-1)
- class_op = (classOps clas) !! (tag-1)
- error_msg = _UNPK_ clas_mod ++ "." ++ _UNPK_ clas_name ++ "."
- ++ (ppShow 80 (ppr PprForUser class_op))
- ++ "\""
+\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 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
-~~~~~~~~
+Contexts and errors
+~~~~~~~~~~~~~~~~~~~
\begin{code}
-classDeclCtxt class_name sty
- = ppCat [ppStr "In the class declaration for", ppr sty class_name]
+nullaryClassErr cls
+ = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
+
+classArityErr cls
+ = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
+ parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
+
+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 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)
+
+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
+ = 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)")]
+
+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