%
-% (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}
-#include "HsVersions.h"
-
module TcClassDcl ( tcClassDecl1, tcClassDecls2,
- badMethodErr, tcMethodBind
+ tcMethodBind, badMethodErr
) where
-IMP_Ubiq()
-
-import HsSyn ( HsDecl(..), ClassDecl(..), HsBinds(..), MonoBinds(..),
- Match(..), GRHSsAndBinds(..), GRHS(..), HsExpr(..),
- DefaultDecl, TyDecl, InstDecl, IfaceSig, Fixity,
- HsLit(..), OutPat(..), Sig(..), HsType(..), HsTyVar, InPat(..),
- SYN_IE(RecFlag), nonRecursive, andMonoBinds, collectMonoBinders,
- Stmt, DoOrListComp, ArithSeqInfo, Fake )
-import HsTypes ( getTyVarName )
-import HsPragmas ( ClassPragmas(..) )
-import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..),
- RenamedClassOpSig(..), SYN_IE(RenamedMonoBinds),
- RenamedGenPragmas(..), RenamedContext(..), SYN_IE(RenamedHsDecl)
+#include "HsVersions.h"
+
+import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..),
+ HsExpr(..), HsLit(..), HsType(..), HsPred(..),
+ mkSimpleMatch, andMonoBinds, andMonoBindList,
+ isClassOpSig, isPragSig,
+ getClassDeclSysNames,
)
-import TcHsSyn ( SYN_IE(TcHsBinds), SYN_IE(TcMonoBinds), SYN_IE(TcExpr),
- mkHsTyApp, mkHsTyLam, mkHsDictApp, mkHsDictLam, tcIdType )
-
-import Inst ( Inst, InstOrigin(..), SYN_IE(LIE), emptyLIE, plusLIE, newDicts, newMethod )
-import TcEnv ( tcLookupClass, tcLookupTyVar, newLocalIds, tcAddImportedIdInfo,
- tcExtendGlobalTyVars )
-import TcBinds ( tcBindWithSigs, TcSigInfo(..) )
-import TcKind ( unifyKind, TcKind )
-import TcMonad
-import TcMonoType ( tcHsType, tcContext )
-import TcSimplify ( tcSimplifyAndCheck )
-import TcType ( TcIdOcc(..), SYN_IE(TcType), SYN_IE(TcTyVar), tcInstType, tcInstSigTyVars,
- tcInstSigType, tcInstSigTcType )
-import PragmaInfo ( PragmaInfo(..) )
-
-import Bag ( bagToList, unionManyBags )
-import Class ( GenClass, mkClass, classBigSig,
- classDefaultMethodId,
- SYN_IE(Class)
+import BasicTypes ( TopLevelFlag(..), RecFlag(..) )
+import RnHsSyn ( RenamedTyClDecl,
+ RenamedClassOpSig, RenamedMonoBinds,
+ RenamedContext, RenamedSig,
+ maybeGenericMatch
)
-import CmdLineOpts ( opt_PprUserLength )
-import Id ( GenId, mkSuperDictSelId, mkMethodSelId,
- mkDefaultMethodId, getIdUnfolding,
- idType, SYN_IE(Id)
+import TcHsSyn ( TcMonoBinds )
+
+import Inst ( InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs,
+ newDicts, newMethod )
+import TcEnv ( TcId, TcEnv, RecTcEnv, TyThingDetails(..), tcAddImportedIdInfo,
+ tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars,
+ tcExtendLocalValEnv, tcExtendTyVarEnv
)
-import CoreUnfold ( getUnfoldingTemplate )
-import IdInfo
-import Name ( Name, isLocallyDefined, moduleString, getSrcLoc,
- OccName, nameOccName,
- nameString, NamedThing(..) )
+import TcBinds ( tcBindWithSigs, tcSpecSigs )
+import TcMonoType ( tcHsRecType, tcRecClassContext, checkSigTyVars, checkAmbiguity, sigCtxt, mkTcSig )
+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, classTyCon,
+ Class, ClassOpItem, DefMeth (..) )
+import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId )
+import DataCon ( mkDataCon, notMarkedStrict )
+import Id ( Id, idType, idName )
+import Module ( Module )
+import Name ( Name, NamedThing(..) )
+import Name ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv, nameEnvElts )
+import NameSet ( emptyNameSet )
import Outputable
-import Pretty
-import PprType ( GenClass, GenType, GenTyVar )
-import SpecEnv ( SpecEnv )
-import SrcLoc ( mkGeneratedSrcLoc )
-import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, splitRhoTy,
- mkForAllTy, mkSigmaTy, splitSigmaTy, SYN_IE(Type)
+import Type ( Type, ClassContext, mkTyVarTys, mkDictTys, mkClassPred,
+ splitTyConApp_maybe, isTyVarTy
)
-import TysWiredIn ( stringTy )
-import TyVar ( unitTyVarSet, GenTyVar, SYN_IE(TyVar) )
-import Unique ( Unique, Uniquable(..) )
-import Util
-import Maybes ( assocMaybe, maybeToBool )
-
-
--- import TcPragmas ( tcGenPragmas, tcClassOpPragmas )
-tcGenPragmas ty id ps = returnNF_Tc noIdInfo
-tcClassOpPragmas ty sel def spec ps = returnNF_Tc (noIdInfo `addSpecInfo` spec,
- noIdInfo)
+import Var ( TyVar )
+import VarSet ( mkVarSet, emptyVarSet )
+import CmdLineOpts
+import ErrUtils ( dumpIfSet )
+import Util ( count )
+import Maybes ( seqMaybe, maybeToBool )
\end{code}
Death to "ExpandingDicts".
+%************************************************************************
+%* *
+\subsection{Type checking}
+%* *
+%************************************************************************
+
\begin{code}
-tcClassDecl1 rec_env 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 `thenTc` \ (class_kind, rec_class) ->
- tcLookupTyVar (getTyVarName tyvar_name) `thenNF_Tc` \ (tyvar_kind, rec_tyvar) ->
+tcClassDecl1 :: RecFlag -> RecTcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails)
+tcClassDecl1 is_rec 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})
+ = -- CHECK ARITY 1 FOR HASKELL 1.4
+ doptsTc Opt_GlasgowExts `thenTc` \ gla_ext_opt ->
let
- rec_class_inst_env = rec_inst_mapper rec_class
- in
+ gla_exts = gla_ext_opt || not (maybeToBool def_methods)
+ -- Accept extensions if gla_exts is on,
+ -- or if we're looking at an interface file decl
+ in -- (in which case def_methods = Nothing
- -- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND
- unifyKind class_kind tyvar_kind `thenTc_`
+ checkTc (gla_exts || length tyvar_names == 1)
+ (classArityErr class_name) `thenTc_`
+ -- 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) = getClassDeclSysNames sys_names
+ in
+ tcExtendTyVarEnv tyvars $
+
+ -- SOURCE-CODE CONSISTENCY CHECKS
+ (case def_methods of
+ Nothing -> returnTc Nothing -- Not source
+ Just dms -> checkDefaultBinds clas op_names dms `thenTc` \ dm_env ->
+ checkGenericClassIsUnary clas dm_env `thenTc_`
+ returnTc (Just dm_env)
+ ) `thenTc` \ mb_dm_env ->
+
-- CHECK THE CONTEXT
- tcClassContext rec_class rec_tyvar context pragmas
- `thenTc` \ (scs, sc_sel_ids) ->
+ tcSuperClasses is_rec gla_exts clas context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) ->
-- CHECK THE CLASS SIGNATURES,
- mapTc (tcClassSig rec_env rec_class rec_tyvar) class_sigs
- `thenTc` \ sig_stuff ->
+ mapTc (tcClassSig is_rec rec_env clas tyvars mb_dm_env) op_sigs `thenTc` \ sig_stuff ->
- -- MAKE THE CLASS OBJECT ITSELF
+ -- MAKE THE CLASS DETAILS
let
- (op_sel_ids, defm_ids) = unzip sig_stuff
- clas = mkClass (uniqueOf class_name) (getName class_name) rec_tyvar
- scs sc_sel_ids op_sel_ids defm_ids
- rec_class_inst_env
+ (op_tys, op_items) = unzip sig_stuff
+ sc_tys = mkDictTys sc_theta
+ 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
+
+ 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}
+\begin{code}
+checkDefaultBinds :: Class -> [Name] -> RenamedMonoBinds
+ -> TcM (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
- let
- clas_ty = mkTyVarTy clas_tyvar
- dict_component_tys = classDictArgTys clas_ty
- 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
+ -- But do all this only for source binds
+
+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_`
+
+ returnTc (unitNameEnv op all_generic)
+ where
+ n_generic = count (maybeToBool . maybeGenericMatch) matches
+ none_generic = n_generic == 0
+ all_generic = n_generic == length matches
+
+checkGenericClassIsUnary clas dm_env
+ = -- 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 = not (or (nameEnvElts dm_env))
+\end{code}
\begin{code}
-tcClassContext :: Class -> TyVar
+tcSuperClasses :: RecFlag -> Bool -> Class
-> RenamedContext -- class context
- -> RenamedClassPragmas -- pragmas for superclasses
- -> TcM s ([Class], -- the superclasses
- [Id]) -- superclass selector Ids
+ -> [Name] -- Names for superclass selectors
+ -> TcM (ClassContext, -- the superclass context
+ [Id]) -- superclass selector Ids
-tcClassContext rec_class rec_tyvar context pragmas
+tcSuperClasses is_rec gla_exts 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.
- tcContext context `thenTc` \ theta ->
- let
- super_classes = [ supers | (supers, _) <- theta ]
- in
- -- Make super-class selector ids
- mapTc (mk_super_id rec_class) super_classes `thenTc` \ sc_sel_ids ->
+ -- For std Haskell check that the context constrains only tyvars
+ (if gla_exts then
+ returnTc ()
+ else
+ mapTc_ check_constraint context
+ ) `thenTc_`
+ -- Context is already kind-checked
+ tcRecClassContext is_rec context `thenTc` \ sc_theta ->
+ let
+ sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names]
+ in
-- Done
- returnTc (super_classes, sc_sel_ids)
+ returnTc (sc_theta, sc_sel_ids)
where
- rec_tyvar_ty = mkTyVarTy rec_tyvar
+ check_constraint sc@(HsPClass c tys)
+ = checkTc (all is_tyvar tys) (superClassErr clas sc)
- mk_super_id rec_class super_class
- = tcGetUnique `thenNF_Tc` \ uniq ->
- let
- ty = mkForAllTy rec_tyvar $
- mkFunTy (mkDictTy rec_class rec_tyvar_ty)
- (mkDictTy super_class rec_tyvar_ty)
- in
- returnTc (mkSuperDictSelId uniq rec_class super_class ty)
+ is_tyvar (HsTyVar _) = True
+ is_tyvar other = False
-tcClassSig :: TcEnv s -- Knot tying only!
+tcClassSig :: RecFlag -> RecTcEnv -- Knot tying only!
-> Class -- ...ditto...
- -> TyVar -- The class type variable, used for error check only
+ -> [TyVar] -- The class type variable, used for error check only
+ -> Maybe (NameEnv Bool) -- Info about default methods
-> RenamedClassOpSig
- -> TcM s (Id, -- selector id
- Maybe Id) -- default-method ids
+ -> TcM (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 rec_clas rec_clas_tyvar
- (ClassOpSig op_name maybe_dm_name
- op_ty
- src_loc)
+tcClassSig is_rec unf_env 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.
- -- NB: Renamer checks that the class type variable is mentioned in local_ty,
- -- and that it is not constrained by theta
- tcHsType op_ty `thenTc` \ local_ty ->
- let
- global_ty = mkSigmaTy [rec_clas_tyvar]
- [(rec_clas, mkTyVarTy rec_clas_tyvar)]
- local_ty
- in
+ tcHsRecType is_rec op_ty `thenTc` \ local_ty ->
- -- Build the selector id and default method id
+ -- Check for ambiguous class op types
let
- sel_id = mkMethodSelId op_name rec_clas global_ty
- maybe_dm_id = case maybe_dm_name of
- Nothing -> Nothing
- Just dm_name -> let
- dm_id = mkDefaultMethodId dm_name rec_clas global_ty
- in
- Just (tcAddImportedIdInfo rec_env dm_id)
+ theta = [mkClassPred clas (mkTyVarTys clas_tyvars)]
in
- returnTc (sel_id, maybe_dm_id)
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[ClassDcl-pass2]{Class decls pass 2: default methods}
-%* *
-%************************************************************************
-
-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 :: [RenamedHsDecl]
- -> NF_TcM s (LIE s, TcMonoBinds s)
-
-tcClassDecls2 decls
- = foldr combine
- (returnNF_Tc (emptyLIE, EmptyMonoBinds))
- [tcClassDecl2 cls_decl | ClD cls_decl <- decls]
- 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 :: RenamedClassDecl -- The class declaration
- -> NF_TcM s (LIE s, TcMonoBinds s)
-
-tcClassDecl2 (ClassDecl context class_name
- tyvar_name 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 $
+ checkAmbiguity is_rec True clas_tyvars theta local_ty `thenTc` \ global_ty ->
+ -- 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.
- -- Get the relevant class
- tcLookupClass class_name `thenTc` \ (_, clas) ->
let
- (tyvar, scs, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
-
- -- The selector binds are already in the selector Id's unfoldings
- sel_binds = [ CoreMonoBind (RealId sel_id) (getUnfoldingTemplate (getIdUnfolding sel_id))
- | sel_id <- sc_sel_ids ++ op_sel_ids,
- isLocallyDefined sel_id
- ]
-
- final_sel_binds = andMonoBinds sel_binds
+ -- Build the selector id and default method id
+ sel_id = mkDictSelId op_name clas
+ dm_id = mkDefaultMethodId dm_name clas global_ty
+ DefMeth dm_name = sig_dm
+
+ dm_info = case maybe_dm_env of
+ Nothing -> iface_dm_info
+ Just dm_env -> mk_src_dm_info dm_env
+
+ iface_dm_info = case sig_dm of
+ NoDefMeth -> NoDefMeth
+ GenDefMeth -> GenDefMeth
+ DefMeth dm_name -> DefMeth (tcAddImportedIdInfo unf_env dm_id)
+
+ mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of
+ Nothing -> NoDefMeth
+ Just True -> GenDefMeth
+ Just False -> DefMeth dm_id
in
- -- Generate bindings for the default methods
- tcDefaultMethodBinds clas default_binds `thenTc` \ (const_insts, meth_binds) ->
+ -- Check that for a generic method, the type of
+ -- the method is sufficiently simple
+ checkTc (dm_info /= GenDefMeth || validGenericMethodType local_ty)
+ (badGenericMethodType op_name op_ty) `thenTc_`
- returnTc (const_insts,
- final_sel_binds `AndMonoBinds` meth_binds)
+ returnTc (local_ty, (sel_id, dm_info))
\end{code}
+
%************************************************************************
%* *
\subsection[Default methods]{Default methods}
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}
-tcDefaultMethodBinds
- :: Class
- -> RenamedMonoBinds
- -> TcM s (LIE s, TcMonoBinds s)
+tcClassDecls2 :: Module -> [RenamedTyClDecl] -> NF_TcM (LIE, TcMonoBinds)
-tcDefaultMethodBinds clas default_binds
- = -- Construct suitable signatures
- tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], [inst_ty], inst_env) ->
+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) ->
+ tc2 `thenNF_Tc` \ (lie2, binds2) ->
+ returnNF_Tc (lie1 `plusLIE` lie2,
+ binds1 `AndMonoBinds` binds2)
+\end{code}
- -- Typecheck the default bindings
+@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)
+
+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
- clas_tyvar_set = unitTyVarSet clas_tyvar
-
- tc_dm meth_bind
- | not (maybeToBool maybe_stuff)
- = -- Binding for something that isn't in the class signature
- failTc (badMethodErr bndr_name clas)
-
- | otherwise
- = -- Normal case
- tcMethodBind clas origin inst_ty sel_id meth_bind
- `thenTc` \ (bind, insts, (_, local_dm_id)) ->
- returnTc (bind, insts, ([clas_tyvar], RealId dm_id, local_dm_id))
- where
- bndr_name = case meth_bind of
- FunMonoBind name _ _ _ -> name
- PatMonoBind (VarPatIn name) _ _ -> name
-
- maybe_stuff = assocMaybe assoc_list (nameOccName bndr_name)
- assoc_list = [ (getOccName sel_id, pair)
- | pair@(sel_id, dm_ie) <- op_sel_ids `zip` defm_ids
- ]
- Just (sel_id, Just dm_id) = maybe_stuff
- -- We're looking at a default-method binding, so the dm_id
- -- is sure to be there! Hence the inner "Just".
- in
- tcExtendGlobalTyVars clas_tyvar_set (
- mapAndUnzip3Tc tc_dm (flatten default_binds [])
- ) `thenTc` \ (defm_binds, insts_needed, abs_bind_stuff) ->
-
- -- Check the context
- newDicts origin [(clas,inst_ty)] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+ (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) ->
+
+ returnTc (plusLIEs const_lies, andMonoBindList defm_binds)
+
+
+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
- avail_insts = this_dict
+ 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) $
+
+ -- 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
- clas_tyvar_set
- avail_insts
- (unionManyBags insts_needed) `thenTc` \ (const_lie, dict_binds) ->
-
+ (ptext SLIT("class") <+> ppr clas)
+ (mkVarSet clas_tyvars')
+ this_dict
+ insts_needed `thenTc` \ (const_lie, dict_binds) ->
+
let
- full_binds = AbsBinds
- [clas_tyvar]
- [this_dict_id]
- abs_bind_stuff
- (dict_binds `AndMonoBinds` andMonoBinds defm_binds)
+ 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 (const_lie, full_binds)
-
+ returnTc (full_bind, const_lie)
where
- (tyvar, scs, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
origin = ClassDeclOrigin
-
- flatten EmptyMonoBinds rest = rest
- flatten (AndMonoBinds b1 b2) rest = flatten b1 (flatten b2 rest)
- flatten a_bind rest = a_bind : rest
\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
\begin{code}
tcMethodBind
:: Class
- -> InstOrigin s
- -> TcType s -- Instance type
- -> Id -- The method selector
- -> RenamedMonoBinds -- Method binding (just one)
- -> TcM s (TcMonoBinds s, LIE s, (LIE s, TcIdOcc s))
-
-tcMethodBind clas origin inst_ty sel_id meth_bind
- = tcAddSrcLoc src_loc $
- newMethod origin (RealId sel_id) [inst_ty] `thenNF_Tc` \ meth@(_, TcId local_meth_id) ->
- tcInstSigTcType (idType local_meth_id) `thenNF_Tc` \ (tyvars', rho_ty') ->
- let
- (theta', tau') = splitRhoTy rho_ty'
- sig_info = TySigInfo bndr_name local_meth_id tyvars' theta' tau' src_loc
- in
- tcBindWithSigs [bndr_name] meth_bind [sig_info]
- nonRecursive (\_ -> NoPragmaInfo) `thenTc` \ (binds, insts, _) ->
-
- returnTc (binds, insts, meth)
+ -> 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, (LIE, TcId))
+
+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@(_, 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
+ -- ...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_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
+ doptsTc Opt_WarnMissingMethods `thenNF_Tc` \ warn ->
+ warnTc (is_inst_decl && warn)
+ (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
- (bndr_name, src_loc) = case meth_bind of
- FunMonoBind name _ _ loc -> (name, loc)
- PatMonoBind (VarPatIn name) _ loc -> (name, loc)
+ 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}
-badMethodErr bndr clas sty
- = hsep [ptext SLIT("Class"), ppr sty clas, ptext SLIT("does not have a method"), ppr sty bndr]
+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)
+
+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 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)
-classDeclCtxt class_name sty
- = hsep [ptext SLIT("In the class declaration for"), ppr sty class_name]
+genericMultiParamErr clas
+ = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
+ ptext SLIT("cannot have generic methods")
\end{code}
projects / ghc-hetmet.git / blobdiff