%
-% (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, tcClassDecls2,
+ tcMethodBind, mkMethodBind, badMethodErr
+ ) where
+
#include "HsVersions.h"
-module TcClassDcl ( tcClassDecl1, tcClassDecls2 ) where
-
-IMP_Ubiq()
-
-import HsSyn ( HsDecl(..), ClassDecl(..), HsBinds(..), MonoBinds(..),
- Match(..), GRHSsAndBinds(..), GRHS(..), HsExpr(..),
- DefaultDecl, TyDecl, InstDecl, IfaceSig, Fixity,
- HsLit(..), OutPat(..), Sig(..), HsType(..), HsTyVar,
- SYN_IE(RecFlag), nonRecursive, andMonoBinds,
- Stmt, DoOrListComp, ArithSeqInfo, InPat, Fake )
-import HsTypes ( getTyVarName )
-import HsPragmas ( ClassPragmas(..) )
-import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..),
- RenamedClassOpSig(..), SYN_IE(RenamedMonoBinds),
- RenamedGenPragmas(..), RenamedContext(..), SYN_IE(RenamedHsDecl)
+import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..),
+ HsExpr(..), HsLit(..), InPat(WildPatIn),
+ mkSimpleMatch, andMonoBinds, andMonoBindList,
+ isClassOpSig, isPragSig,
+ getClassDeclSysNames, placeHolderType
)
-import TcHsSyn ( TcIdOcc(..), 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, tcLookupTyCon, newLocalIds, tcAddImportedIdInfo,
- tcExtendGlobalTyVars )
-import TcInstDcls ( tcMethodBind )
-import TcKind ( unifyKind, TcKind )
-import TcMonad
-import TcMonoType ( tcHsType, tcContext )
-import TcSimplify ( tcSimplifyAndCheck )
-import TcType ( SYN_IE(TcType), SYN_IE(TcTyVar), tcInstType, tcInstSigTyVars, tcInstSigType )
-
-import Bag ( foldBag, unionManyBags )
-import Class ( GenClass, GenClassOp, mkClass, mkClassOp, classBigSig,
- classOps, classOpString, classOpLocalType, classDefaultMethodId,
- classOpTagByOccName, SYN_IE(ClassOp), SYN_IE(Class)
+import BasicTypes ( RecFlag(..), StrictnessMark(..) )
+import RnHsSyn ( RenamedTyClDecl,
+ RenamedClassOpSig, RenamedMonoBinds,
+ maybeGenericMatch
)
-import Id ( GenId, mkSuperDictSelId, mkMethodSelId,
- mkDefaultMethodId, getIdUnfolding,
- idType, SYN_IE(Id)
+import TcHsSyn ( TcMonoBinds )
+
+import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs,
+ instToId, newDicts, newMethod )
+import TcEnv ( TyThingDetails(..),
+ tcLookupClass, tcExtendTyVarEnv2,
+ tcExtendTyVarEnv
)
-import CoreUnfold ( getUnfoldingTemplate )
-import IdInfo
-import Name ( Name, isLocallyDefined, moduleString,
- modAndOcc, nameString, NamedThing(..) )
-import Outputable
-import PrelVals ( nO_DEFAULT_METHOD_ERROR_ID )
-import PprStyle
-import Pretty
-import PprType ( GenClass, GenType, GenTyVar, GenClassOp )
-import SpecEnv ( SpecEnv )
-import SrcLoc ( mkGeneratedSrcLoc )
-import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy,
- mkForAllTy, mkSigmaTy, splitSigmaTy, SYN_IE(Type)
+import TcBinds ( tcMonoBinds )
+import TcMonoType ( TcSigInfo(..), tcHsType, tcHsTheta, mkTcSig )
+import TcSimplify ( tcSimplifyCheck )
+import TcUnify ( checkSigTyVars, sigCtxt )
+import TcMType ( tcInstTyVars )
+import TcType ( Type, TyVarDetails(..), TcType, TcThetaType, TcTyVar,
+ mkTyVarTys, mkPredTys, mkClassPred, tcSplitSigmaTy, tcSplitFunTys,
+ tcIsTyVarTy, tcSplitTyConApp_maybe
)
-import TysWiredIn ( stringTy )
-import TyVar ( unitTyVarSet, GenTyVar, SYN_IE(TyVar) )
-import Unique ( Unique )
-import UniqFM ( Uniquable(..) )
-import Util
-
-
--- import TcPragmas ( tcGenPragmas, tcClassOpPragmas )
-tcGenPragmas ty id ps = returnNF_Tc noIdInfo
-tcClassOpPragmas ty sel def spec ps = returnNF_Tc (noIdInfo `addSpecInfo` spec,
- noIdInfo)
+import TcMonad
+import Generics ( mkGenericRhs )
+import PrelInfo ( nO_METHOD_BINDING_ERROR_ID )
+import Class ( classTyVars, classBigSig, classTyCon,
+ Class, ClassOpItem, DefMeth (..) )
+import TyCon ( tyConGenInfo )
+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 CmdLineOpts
+import UnicodeUtil ( stringToUtf8 )
+import ErrUtils ( dumpIfSet )
+import Util ( count, lengthIs, equalLength )
+import Maybes ( seqMaybe )
+import Maybe ( isJust )
+import FastString
\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 `thenTc` \ (class_kind, rec_class) ->
- tcLookupTyVar (getTyVarName tyvar_name) `thenNF_Tc` \ (tyvar_kind, rec_tyvar) ->
+
+tcClassDecl1 :: RenamedTyClDecl -> TcM (Name, TyThingDetails)
+tcClassDecl1 (ClassDecl {tcdCtxt = context, tcdName = class_name,
+ tcdTyVars = tyvar_names, tcdFDs = fundeps,
+ tcdSigs = class_sigs, tcdMeths = def_methods,
+ tcdSysNames = sys_names, tcdLoc = src_loc})
+ = -- LOOK THINGS UP IN THE ENVIRONMENT
+ tcLookupClass class_name `thenTc` \ clas ->
let
- (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 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}
+\begin{code}
+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
+ go EmptyMonoBinds = returnTc emptyNameEnv
- 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
+ go (AndMonoBinds b1 b2)
+ = go b1 `thenTc` \ dm_info1 ->
+ go b2 `thenTc` \ dm_info2 ->
+ returnTc (dm_info1 `plusNameEnv` dm_info2)
+ go (FunMonoBind op _ matches loc)
+ = tcAddSrcLoc loc $
-\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
+ -- Check that the op is from this class
+ checkTc (op `elem` ops) (badMethodErr clas op) `thenTc_`
- -- Make super-class selector ids
- mapTc (mk_super_id rec_class) super_classes `thenTc` \ sc_sel_ids ->
+ -- Check that all the defns ar generic, or none are
+ checkTc (all_generic || none_generic) (mixedGenericErr op) `thenTc_`
- -- Done
- returnTc (super_classes, sc_sel_ids)
+ returnTc (unitNameEnv op all_generic)
+ where
+ n_generic = count (isJust . maybeGenericMatch) matches
+ none_generic = n_generic == 0
+ all_generic = matches `lengthIs` n_generic
+\end{code}
- where
- rec_tyvar_ty = mkTyVarTy rec_tyvar
- 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)
+\begin{code}
+tcClassSig :: 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
+-- 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 :: 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 dm_name
- op_ty
- src_loc)
+tcClassSig clas clas_tyvars maybe_dm_env
+ (ClassOpSig op_name sig_dm op_ty 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.
+ tcHsType op_ty `thenTc` \ local_ty ->
- -- NB: Renamer checks that the class type variable is mentioned in local_ty,
- -- and that it is not constrained by theta
- tcHsType op_ty `thenTc` \ local_ty ->
let
- global_ty = mkSigmaTy [rec_clas_tyvar]
- [(rec_clas, mkTyVarTy rec_clas_tyvar)]
- local_ty
- class_op_nm = getOccName op_name
- class_op = mkClassOp class_op_nm
- (classOpTagByOccName rec_clas{-yeeps!-} class_op_nm)
- local_ty
- in
+ theta = [mkClassPred clas (mkTyVarTys clas_tyvars)]
-- Build the selector id and default method id
- let
- sel_id = mkMethodSelId op_name rec_clas class_op global_ty
- defm_id = mkDefaultMethodId dm_name rec_clas class_op False global_ty
- -- ToDo: improve the "False"
- in
- tcAddImportedIdInfo defm_id `thenNF_Tc` \ final_defm_id ->
- returnTc (class_op, sel_id, final_defm_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, TcHsBinds s)
-
-tcClassDecls2 decls
- = foldr combine
- (returnNF_Tc (emptyLIE, EmptyBinds))
- [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 `ThenBinds` binds2)
-\end{code}
+ sel_id = mkDictSelId op_name clas
+ DefMeth dm_name = sig_dm
-@tcClassDecl2@ is the business end of things.
+ dm_info = case maybe_dm_env of
+ Nothing -> sig_dm
+ Just dm_env -> mk_src_dm_info dm_env
-\begin{code}
-tcClassDecl2 :: RenamedClassDecl -- The class declaration
- -> NF_TcM s (LIE s, TcHsBinds s)
-
-tcClassDecl2 (ClassDecl context class_name
- tyvar_name class_sigs default_binds pragmas src_loc)
-
- | not (isLocallyDefined class_name)
- = returnNF_Tc (emptyLIE, EmptyBinds)
-
- | otherwise -- It is locally defined
- = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $
- tcAddSrcLoc src_loc $
-
- -- Get the relevant class
- tcLookupClass class_name `thenTc` \ (_, clas) ->
- let
- (tyvar, scs, sc_sel_ids, ops, 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 = MonoBind (andMonoBinds sel_binds) [] nonRecursive
+ mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of
+ Nothing -> NoDefMeth
+ Just True -> GenDefMeth
+ Just False -> DefMeth dm_name
in
- -- Generate bindings for the default methods
- tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], _, _) ->
- mapAndUnzipTc (buildDefaultMethodBind clas clas_tyvar default_binds)
- (op_sel_ids `zip` [0..])
- `thenTc` \ (const_insts_s, meth_binds) ->
-
- returnTc (unionManyBags const_insts_s,
- final_sel_binds `ThenBinds`
- MonoBind (andMonoBinds meth_binds) [] nonRecursive)
+ 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}
+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}
-buildDefaultMethodBind
- :: Class
- -> TcTyVar s
- -> RenamedMonoBinds
- -> (Id, Int)
- -> TcM s (LIE s, TcMonoBinds s)
-
-buildDefaultMethodBind clas clas_tyvar default_binds (sel_id, idx)
- = newDicts origin [(clas,inst_ty)] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+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
- defm_id = classDefaultMethodId clas idx
+ (tyvars, _, _, op_items) = classBigSig clas
+ prags = filter isPragSig sigs
+ tc_dm = tcDefMeth clas tyvars default_binds prags
in
- tcExtendGlobalTyVars clas_tyvar_set (
- tcMethodBind noDefmExpr inst_ty default_binds (sel_id, idx)
- ) `thenTc` \ (defm_bind, insts_needed, (_, local_defm_id)) ->
+ 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)
+ = tcInstTyVars ClsTv tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) ->
+ let
+ dm_ty = idType sel_id -- Same as dict selector!
+ -- The default method's type should really come from the
+ -- iface file, since it could be usage-generalised, but this
+ -- requires altering the mess of knots in TcModule and I'm
+ -- too scared to do that. Instead, I have disabled generalisation
+ -- of types of default methods (and dict funs) by annotating them
+ -- TyGenNever (in MkId). Ugh! KSW 1999-09.
+
+ theta = [mkClassPred clas inst_tys]
+ dm_id = mkDefaultMethodId dm_name dm_ty
+ local_dm_id = setIdLocalExported dm_id
+ -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId
+ xtve = tyvars `zip` clas_tyvars
+ in
+ newDicts origin theta `thenNF_Tc` \ [this_dict] ->
+
+ mkMethodBind origin clas inst_tys binds_in op_item `thenTc` \ (dm_inst, meth_info) ->
+ tcMethodBind xtve clas_tyvars theta
+ [this_dict] meth_info `thenTc` \ (defm_bind, insts_needed) ->
+
+ tcAddErrCtxt (defltMethCtxt clas) $
+
+ -- 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 `thenTc` \ clas_tyvars' ->
+
+ let
+ full_bind = AbsBinds
+ clas_tyvars'
+ [instToId this_dict]
+ [(clas_tyvars', local_dm_id, instToId dm_inst)]
+ emptyNameSet -- No inlines (yet)
+ (dict_binds `andMonoBinds` defm_bind)
+ in
+ returnTc (full_bind, const_lie, [dm_id])
+ where
+ origin = ClassDeclOrigin
+\end{code}
- -- CHECK THE CONTEXT OF THE DEFAULT-METHOD BINDS
- tcSimplifyAndCheck
- clas_tyvar_set
- avail_insts
- insts_needed `thenTc` \ (const_lie, dict_binds) ->
+
+%************************************************************************
+%* *
+\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}
+tcMethodBind
+ :: [(TyVar,TcTyVar)] -- Bindings for type environment
+ -> [TcTyVar] -- Instantiated type variables for the
+ -- enclosing class/instance decl.
+ -- They'll be signature tyvars, and we
+ -- want to check that they don't get bound
+ -- Always equal the range of the type envt
+ -> TcThetaType -- Available theta; it's just used for the error message
+ -> [Inst] -- Available from context, used to simplify constraints
+ -- from the method body
+ -> (Id, TcSigInfo, RenamedMonoBinds) -- Details of this method
+ -> TcM (TcMonoBinds, LIE)
+
+tcMethodBind xtve inst_tyvars inst_theta avail_insts
+ (sel_id, meth_sig, meth_bind)
+ =
+ -- Check the bindings; first adding inst_tyvars to the envt
+ -- so that we don't quantify over them in nested places
+ tcExtendTyVarEnv2 xtve (
+ tcAddErrCtxt (methodCtxt sel_id) $
+ tcMonoBinds meth_bind [meth_sig] NonRecursive
+ ) `thenTc` \ (meth_bind, meth_lie, _, _) ->
+
+ -- Now do context reduction. We simplify wrt both the local tyvars
+ -- and the ones of the class/instance decl, so that there is
+ -- no problem with
+ -- class C a where
+ -- op :: Eq a => a -> b -> a
+ --
+ -- We do this for each method independently to localise error messages
+
+ let
+ TySigInfo meth_id meth_tvs meth_theta _ local_meth_id _ _ = meth_sig
+ in
+ tcAddErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $
+ newDicts SignatureOrigin meth_theta `thenNF_Tc` \ meth_dicts ->
+ let
+ all_tyvars = meth_tvs ++ inst_tyvars
+ all_insts = avail_insts ++ meth_dicts
+ in
+ tcSimplifyCheck
+ (ptext SLIT("class or instance method") <+> quotes (ppr sel_id))
+ all_tyvars all_insts meth_lie `thenTc` \ (lie, lie_binds) ->
+
+ checkSigTyVars all_tyvars `thenTc` \ all_tyvars' ->
+
+ let
+ meth_tvs' = take (length meth_tvs) all_tyvars'
+ poly_meth_bind = AbsBinds meth_tvs'
+ (map instToId meth_dicts)
+ [(meth_tvs', meth_id, local_meth_id)]
+ emptyNameSet -- Inlines?
+ (lie_binds `andMonoBinds` meth_bind)
+ in
+ returnTc (poly_meth_bind, lie)
+
+
+mkMethodBind :: InstOrigin
+ -> Class -> [TcType] -- Class and instance types
+ -> RenamedMonoBinds -- Method binding (pick the right one from in here)
+ -> ClassOpItem
+ -> TcM (Inst, -- Method inst
+ (Id, -- Global selector Id
+ TcSigInfo, -- Signature
+ RenamedMonoBinds)) -- Binding for the method
+
+mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info)
+ = tcGetSrcLoc `thenNF_Tc` \ loc ->
+ newMethod origin sel_id inst_tys `thenNF_Tc` \ meth_inst ->
let
- defm_binds = AbsBinds
- [clas_tyvar]
- [this_dict_id]
- [([clas_tyvar], RealId defm_id, local_defm_id)]
- (dict_binds `AndMonoBinds` defm_bind)
+ meth_id = instToId meth_inst
+ meth_name = idName meth_id
in
- returnTc (const_lie, defm_binds)
-
+ -- 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 origin 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 ->
+
+ mkTcSig meth_id loc `thenNF_Tc` \ meth_sig ->
+
+ returnTc (meth_inst, (sel_id, meth_sig, meth_bind))
+
+
+ -- The user didn't supply a method binding,
+ -- so we have to make up a default binding
+ -- The RHS of a default method depends on the default-method info
+mkDefMethRhs origin clas inst_tys sel_id loc (DefMeth dm_name)
+ = -- An polymorphic default method
+ returnTc (HsVar dm_name)
+
+mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth
+ = -- No default method
+ -- Warn only if -fwarn-missing-methods
+ doptsTc Opt_WarnMissingMethods `thenNF_Tc` \ warn ->
+ warnTc (isInstDecl origin && warn)
+ (omittedMethodWarn sel_id) `thenNF_Tc_`
+ returnTc error_rhs
+ where
+ error_rhs = HsLam (mkSimpleMatch wild_pats simple_rhs placeHolderType loc)
+ simple_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
+ (HsLit (HsStringPrim (mkFastString (stringToUtf8 error_msg))))
+ error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
+
+ -- When the type is of form t1 -> t2 -> t3
+ -- make a default method like (\ _ _ -> noMethBind "blah")
+ -- rather than simply (noMethBind "blah")
+ -- Reason: if t1 or t2 are higher-ranked types we get n
+ -- silly ambiguity messages.
+ -- Example: f :: (forall a. Eq a => a -> a) -> Int
+ -- f = error "urk"
+ -- Here, tcSub tries to force (error "urk") to have the right type,
+ -- thus: f = \(x::forall a. Eq a => a->a) -> error "urk" (x t)
+ -- where 't' is fresh ty var. This leads directly to "ambiguous t".
+ --
+ -- NB: technically this changes the meaning of the default-default
+ -- method slightly, because `seq` can see the lambdas. Oh well.
+ (_,_,tau1) = tcSplitSigmaTy (idType sel_id)
+ (_,_,tau2) = tcSplitSigmaTy tau1
+ -- Need two splits because the selector can have a type like
+ -- forall a. Foo a => forall b. Eq b => ...
+ (arg_tys, _) = tcSplitFunTys tau2
+ wild_pats = [WildPatIn | ty <- arg_tys]
+
+mkDefMethRhs origin clas inst_tys sel_id loc GenDefMeth
+ = -- A generic default method
+ -- If the method is defined generically, we can only do the job if the
+ -- instance declaration is for a single-parameter type class with
+ -- a type constructor applied to type arguments in the instance decl
+ -- (checkTc, so False provokes the error)
+ ASSERT( isInstDecl origin ) -- We never get here from a class decl
+
+ checkTc (isJust maybe_tycon)
+ (badGenericInstance sel_id (notSimple inst_tys)) `thenTc_`
+ checkTc (isJust (tyConGenInfo tycon))
+ (badGenericInstance sel_id (notGeneric tycon)) `thenTc_`
+
+ ioToTc (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenNF_Tc_`
+ returnTc rhs
where
- clas_tyvar_set = unitTyVarSet clas_tyvar
- inst_ty = mkTyVarTy clas_tyvar
- origin = ClassDeclOrigin
- noDefmExpr _ = HsApp (HsVar (getName nO_DEFAULT_METHOD_ERROR_ID))
- (HsLit (HsString (_PK_ error_msg)))
-
- error_msg = show (sep [text "Class", ppr PprForUser clas,
- text "Method", ppr PprForUser sel_id])
+ 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)
+ clas_tyvar = head (classTyVars clas)
+ Just tycon = maybe_tycon
+ maybe_tycon = case inst_tys of
+ [ty] -> case tcSplitTyConApp_maybe ty of
+ Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon
+ other -> Nothing
+ other -> Nothing
+
+isInstDecl InstanceDeclOrigin = True
+isInstDecl ClassDeclOrigin = False
\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 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
- = hsep [ptext SLIT("In the class declaration for"), ppr sty 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 clas op
+ = hsep [ptext SLIT("Class"), quotes (ppr clas),
+ ptext SLIT("does not have a method"), quotes (ppr op)]
+
+omittedMethodWarn sel_id
+ = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id)
+
+badGenericInstance sel_id because
+ = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id),
+ because]
+
+notSimple inst_tys
+ = vcat [ptext SLIT("because the instance type(s)"),
+ nest 2 (ppr inst_tys),
+ ptext SLIT("is not a simple type of form (T a b c)")]
+
+notGeneric tycon
+ = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+>
+ ptext SLIT("was not compiled with -fgenerics")]
+
+mixedGenericErr op
+ = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op)
\end{code}
projects / ghc-hetmet.git / blobdiff