%
-% (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, tcMethodBind ) where
+module TcClassDcl ( tcClassDecl1, tcClassDecls2, tcMethodBind, badMethodErr ) where
-IMP_Ubiq()
+#include "HsVersions.h"
-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 HsSyn ( HsDecl(..), ClassDecl(..), Sig(..), MonoBinds(..),
+ InPat(..), HsBinds(..), GRHSsAndBinds(..),
+ HsExpr(..), HsLit(..), HsType(..), pprClassAssertion,
+ unguardedRHS, andMonoBinds, andMonoBindList, getTyVarName
+ )
import HsPragmas ( ClassPragmas(..) )
-import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..),
- RenamedClassOpSig(..), SYN_IE(RenamedMonoBinds),
- RenamedGenPragmas(..), RenamedContext(..), SYN_IE(RenamedHsDecl)
+import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..), StrictnessMark(..) )
+import RnHsSyn ( RenamedClassDecl, RenamedClassPragmas,
+ RenamedClassOpSig, RenamedMonoBinds,
+ RenamedContext, RenamedHsDecl, RenamedSig
+ )
+import TcHsSyn ( TcMonoBinds )
+
+import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, newDicts, newMethod )
+import TcEnv ( TcIdOcc(..), GlobalValueEnv, tcAddImportedIdInfo,
+ tcLookupClass, tcLookupTyVar,
+ tcExtendGlobalTyVars, tcExtendLocalValEnv
)
-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 TcBinds ( tcBindWithSigs, tcPragmaSigs )
+import TcUnify ( unifyKinds )
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,
- classOpTagByOccName, SYN_IE(Class)
+import TcMonoType ( tcHsType, tcContext, checkSigTyVars, sigCtxt, mkTcSig )
+import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
+import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcTyVarBndr )
+import PrelVals ( nO_METHOD_BINDING_ERROR_ID )
+import FieldLabel ( firstFieldLabelTag )
+import Bag ( unionManyBags )
+import Class ( mkClass, classBigSig, Class )
+import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods )
+import MkId ( mkSuperDictSelId, mkDataConId,
+ mkMethodSelId, mkDefaultMethodId
)
-import CmdLineOpts ( opt_PprUserLength )
-import Id ( GenId, mkSuperDictSelId, mkMethodSelId,
- mkDefaultMethodId, getIdUnfolding,
- idType, SYN_IE(Id)
+import DataCon ( mkDataCon )
+import Id ( Id,
+ getIdUnfolding, idType, idName
)
import CoreUnfold ( getUnfoldingTemplate )
import IdInfo
-import Name ( Name, isLocallyDefined, moduleString, getSrcLoc, nameOccName,
- nameString, NamedThing(..) )
+import Name ( Name, isLocallyDefined, NamedThing(..) )
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 ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy,
+ mkSigmaTy, mkForAllTys, Type, ThetaType,
+ boxedTypeKind, mkArrowKind
)
-import TysWiredIn ( stringTy )
-import TyVar ( unitTyVarSet, GenTyVar, SYN_IE(TyVar) )
+import Var ( tyVarKind, TyVar )
+import VarSet ( mkVarSet )
+import TyCon ( mkAlgTyCon )
import Unique ( Unique, Uniquable(..) )
import Util
+import Maybes ( seqMaybe )
-- import TcPragmas ( tcGenPragmas, tcClassOpPragmas )
tcGenPragmas ty id ps = returnNF_Tc noIdInfo
-tcClassOpPragmas ty sel def spec ps = returnNF_Tc (noIdInfo `addSpecInfo` spec,
+tcClassOpPragmas ty sel def spec ps = returnNF_Tc (spec `setSpecInfo` noIdInfo,
noIdInfo)
\end{code}
\begin{code}
tcClassDecl1 rec_env rec_inst_mapper
(ClassDecl context class_name
- tyvar_name class_sigs def_methods pragmas src_loc)
+ tyvar_names class_sigs def_methods pragmas
+ tycon_name datacon_name src_loc)
= tcAddSrcLoc src_loc $
tcAddErrCtxt (classDeclCtxt class_name) $
+ -- CHECK ARITY 1 FOR HASKELL 1.4
+ checkTc (opt_GlasgowExts || length tyvar_names == 1)
+ (classArityErr class_name) `thenTc_`
+
-- LOOK THINGS UP IN THE ENVIRONMENT
- tcLookupClass class_name `thenTc` \ (class_kind, rec_class) ->
- tcLookupTyVar (getTyVarName tyvar_name) `thenNF_Tc` \ (tyvar_kind, rec_tyvar) ->
- let
- rec_class_inst_env = rec_inst_mapper rec_class
- in
+ tcLookupClass class_name `thenTc` \ (class_kinds, rec_class) ->
+ mapAndUnzipNF_Tc (tcLookupTyVar . getTyVarName) tyvar_names
+ `thenNF_Tc` \ (tyvar_kinds, rec_tyvars) ->
-- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND
- unifyKind class_kind tyvar_kind `thenTc_`
+ unifyKinds class_kinds tyvar_kinds `thenTc_`
-- CHECK THE CONTEXT
- tcClassContext rec_class rec_tyvar context pragmas
- `thenTc` \ (scs, sc_sel_ids) ->
+ tcClassContext class_name rec_class rec_tyvars context pragmas
+ `thenTc` \ (sc_theta, sc_tys, sc_sel_ids) ->
-- CHECK THE CLASS SIGNATURES,
- mapTc (tcClassSig rec_env rec_class rec_tyvar) class_sigs
- `thenTc` \ sig_stuff ->
+ mapTc (tcClassSig rec_env rec_class rec_tyvars) class_sigs
+ `thenTc` \ sig_stuff ->
-- MAKE THE CLASS OBJECT ITSELF
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
+ (op_tys, op_sel_ids, defm_ids) = unzip3 sig_stuff
+ rec_class_inst_env = rec_inst_mapper rec_class
+ clas = mkClass (getName class_name) rec_tyvars
+ sc_theta sc_sel_ids op_sel_ids defm_ids
+ tycon
rec_class_inst_env
- in
- returnTc clas
-\end{code}
-
- let
- clas_ty = mkTyVarTy clas_tyvar
- dict_component_tys = classDictArgTys clas_ty
+ dict_component_tys = sc_tys ++ op_tys
new_or_data = case dict_component_tys of
[_] -> NewType
other -> DataType
- dict_con_id = mkDataCon class_name
- [NotMarkedStrict]
+ dict_con = mkDataCon datacon_name
+ [NotMarkedStrict | _ <- dict_component_tys]
[{- No labelled fields -}]
- [clas_tyvar]
+ rec_tyvars
[{-No context-}]
+ [{-No existential tyvars-}] [{-Or context-}]
dict_component_tys
- tycon
-
- tycon = mkDataTyCon class_name
- (tyVarKind rec_tyvar `mkArrowKind` mkBoxedTypeKind)
- [rec_tyvar]
- [{- Empty context -}]
- [dict_con_id]
- [{- No derived classes -}]
+ tycon dict_con_id
+ dict_con_id = mkDataConId dict_con
+
+ tycon = mkAlgTyCon tycon_name
+ (foldr (mkArrowKind . tyVarKind) boxedTypeKind rec_tyvars)
+ rec_tyvars
+ [] -- No context
+ [dict_con] -- Constructors
+ [] -- No derivings
+ (Just clas) -- Yes! It's a dictionary
new_or_data
+ NonRecursive
in
+ returnTc clas
+\end{code}
\begin{code}
-tcClassContext :: Class -> TyVar
+tcClassContext :: Name -> Class -> [TyVar]
-> RenamedContext -- class context
-> RenamedClassPragmas -- pragmas for superclasses
- -> TcM s ([Class], -- the superclasses
- [Id]) -- superclass selector Ids
+ -> TcM s (ThetaType, -- the superclass context
+ [Type], -- types of the superclass dictionaries
+ [Id]) -- superclass selector Ids
-tcClassContext rec_class rec_tyvar context pragmas
+tcClassContext class_name rec_class rec_tyvars 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 ->
+
+ -- For std Haskell check that the context constrains only tyvars
+ (if opt_GlasgowExts then
+ returnTc []
+ else
+ mapTc check_constraint context
+ ) `thenTc_`
+
+ tcContext context `thenTc` \ sc_theta ->
+
let
- super_classes = [ supers | (supers, _) <- theta ]
+ sc_tys = [mkDictTy sc tys | (sc,tys) <- sc_theta]
in
-- Make super-class selector ids
- mapTc (mk_super_id rec_class) super_classes `thenTc` \ sc_sel_ids ->
+ -- We number them off, 1, 2, 3 etc so that we can construct
+ -- names for the selectors. Thus
+ -- class (C a, C b) => D a b where ...
+ -- gives superclass selectors
+ -- D_sc1, D_sc2
+ -- (We used to call them D_C, but now we can have two different
+ -- superclasses both called C!)
+ mapTc mk_super_id (sc_theta `zip` [firstFieldLabelTag..]) `thenTc` \ sc_sel_ids ->
-- Done
- returnTc (super_classes, sc_sel_ids)
+ returnTc (sc_theta, sc_tys, sc_sel_ids)
where
- rec_tyvar_ty = mkTyVarTy rec_tyvar
+ rec_tyvar_tys = mkTyVarTys rec_tyvars
- mk_super_id rec_class super_class
+ mk_super_id ((super_class, tys), index)
= tcGetUnique `thenNF_Tc` \ uniq ->
let
- ty = mkForAllTy rec_tyvar $
- mkFunTy (mkDictTy rec_class rec_tyvar_ty)
- (mkDictTy super_class rec_tyvar_ty)
+ ty = mkForAllTys rec_tyvars $
+ mkFunTy (mkDictTy rec_class rec_tyvar_tys) (mkDictTy super_class tys)
in
- returnTc (mkSuperDictSelId uniq rec_class super_class ty)
+ returnTc (mkSuperDictSelId uniq rec_class index ty)
+ check_constraint (c, tys) = checkTc (all is_tyvar tys)
+ (superClassErr class_name (c, tys))
-tcClassSig :: TcEnv s -- Knot tying only!
+ is_tyvar (MonoTyVar _) = True
+ is_tyvar other = False
+
+
+tcClassSig :: GlobalValueEnv -- 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
-> RenamedClassOpSig
- -> TcM s (Id, -- selector id
+ -> TcM s (Type, -- Type of the method
+ Id, -- selector id
Maybe Id) -- default-method ids
-tcClassSig rec_env rec_clas rec_clas_tyvar
+tcClassSig rec_env rec_clas rec_clas_tyvars
(ClassOpSig op_name maybe_dm_name
op_ty
src_loc)
-- 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)]
+ global_ty = mkSigmaTy rec_clas_tyvars
+ [(rec_clas, mkTyVarTys rec_clas_tyvars)]
local_ty
in
in
Just (tcAddImportedIdInfo rec_env dm_id)
in
- returnTc (sel_id, maybe_dm_id)
+ returnTc (local_ty, sel_id, maybe_dm_id)
\end{code}
-> NF_TcM s (LIE s, TcMonoBinds s)
tcClassDecl2 (ClassDecl context class_name
- tyvar_name class_sigs default_binds pragmas src_loc)
+ tyvar_names class_sigs default_binds pragmas _ _ src_loc)
| not (isLocallyDefined class_name)
= returnNF_Tc (emptyLIE, EmptyMonoBinds)
-- Get the relevant class
tcLookupClass class_name `thenTc` \ (_, clas) ->
let
- (tyvar, scs, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
+ (tyvars, sc_theta, 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
+-- sel_binds = [ CoreMonoBind (RealId sel_id) (getUnfoldingTemplate (getIdUnfolding sel_id))
+-- | sel_id <- sc_sel_ids ++ op_sel_ids,
+-- isLocallyDefined sel_id
+-- ]
+--
+-- final_sel_binds = andMonoBindList sel_binds
in
-- Generate bindings for the default methods
tcDefaultMethodBinds clas default_binds `thenTc` \ (const_insts, meth_binds) ->
- returnTc (const_insts,
- final_sel_binds `AndMonoBinds` meth_binds)
+ returnTc (const_insts, meth_binds)
+-- final_sel_binds `AndMonoBinds` meth_binds)
+-- Leave 'em out for now. They always get inlined anyway. SLPJ June '98
\end{code}
%************************************************************************
tcDefaultMethodBinds clas default_binds
= -- Construct suitable signatures
- tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], [inst_ty], inst_env) ->
+ tcInstTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, inst_env) ->
-- Typecheck the default bindings
let
- clas_tyvar_set = unitTyVarSet clas_tyvar
-
- tc_dm meth_bind
- = let
- bndr_name = case meth_bind of
- FunMonoBind name _ _ _ -> name
- PatMonoBind (VarPatIn name) _ _ -> name
-
- idx = classOpTagByOccName clas (nameOccName bndr_name) - 1
- sel_id = op_sel_ids !! idx
- Just dm_id = defm_ids !! idx
- in
- 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))
+ tc_dm sel_id_w_dm@(_, Just dm_id)
+ = tcMethodBind clas origin inst_tys clas_tyvars
+ default_binds [{-no prags-}] False
+ sel_id_w_dm `thenTc` \ (bind, insts, (_, local_dm_id)) ->
+ returnTc (bind, insts, (clas_tyvars, RealId dm_id, local_dm_id))
in
- tcExtendGlobalTyVars clas_tyvar_set (
- mapAndUnzip3Tc tc_dm (flatten default_binds [])
- ) `thenTc` \ (defm_binds, insts_needed, abs_bind_stuff) ->
+ mapAndUnzip3Tc tc_dm sel_ids_w_dms `thenTc` \ (defm_binds, insts_needed, abs_bind_stuff) ->
-- Check the context
- newDicts origin [(clas,inst_ty)] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+ newDicts origin [(clas,inst_tys)] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
let
- avail_insts = this_dict
+ avail_insts = this_dict
in
+ tcAddErrCtxt (classDeclCtxt clas) $
+
+ -- tcMethodBind has checked that the class_tyvars havn't
+ -- been unified with each other or another type, but we must
+ -- still zonk them
+ mapNF_Tc zonkTcTyVarBndr clas_tyvars `thenNF_Tc` \ clas_tyvars' ->
+
tcSimplifyAndCheck
- clas_tyvar_set
+ (ptext SLIT("class") <+> ppr clas)
+ (mkVarSet clas_tyvars')
avail_insts
(unionManyBags insts_needed) `thenTc` \ (const_lie, dict_binds) ->
let
full_binds = AbsBinds
- [clas_tyvar]
+ clas_tyvars'
[this_dict_id]
abs_bind_stuff
- (dict_binds `AndMonoBinds` andMonoBinds defm_binds)
+ (dict_binds `andMonoBinds` andMonoBindList defm_binds)
in
returnTc (const_lie, full_binds)
where
- (tyvar, scs, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
- origin = ClassDeclOrigin
+ (tyvars, sc_theta, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
+
+ sel_ids_w_dms = [pair | pair@(_, Just _) <- op_sel_ids `zip` defm_ids]
+ -- Just the ones for which there is an explicit
+ -- user default declaration
- flatten EmptyMonoBinds rest = rest
- flatten (AndMonoBinds b1 b2) rest = flatten b1 (flatten b2 rest)
- flatten a_bind rest = a_bind : rest
+ origin = ClassDeclOrigin
\end{code}
@tcMethodBind@ is used to type-check both default-method and
tcMethodBind
:: Class
-> InstOrigin s
- -> TcType s -- Instance type
- -> Id -- The method selector
- -> RenamedMonoBinds -- Method binding (just one)
+ -> [TcType s] -- Instance types
+ -> [TcTyVar s] -- Free variables of those instance types
+ -- they'll be signature tyvars, and we
+ -- want to check that they don't bound
+ -> RenamedMonoBinds -- Method binding (pick the right one from in here)
+ -> [RenamedSig] -- Pramgas (just for this one)
+ -> Bool -- True <=> supply default decl if no explicit decl
+ -- This is true for instance decls,
+ -- false for class decls
+ -> (Id, Maybe Id) -- The method selector and default-method Id
-> 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') ->
+tcMethodBind clas origin inst_tys inst_tyvars
+ meth_binds prags supply_default_bind
+ (sel_id, maybe_dm_id)
+ = tcGetSrcLoc `thenNF_Tc` \ loc ->
+
+ newMethod origin (RealId sel_id) inst_tys `thenNF_Tc` \ meth@(_, TcId meth_id) ->
+ mkTcSig meth_id loc `thenNF_Tc` \ sig_info ->
+
let
- (theta', tau') = splitRhoTy rho_ty'
- sig_info = TySigInfo bndr_name local_meth_id tyvars' theta' tau' src_loc
+ meth_name = idName meth_id
+ maybe_user_bind = find_bind meth_name meth_binds
+
+ no_user_bind = case maybe_user_bind of {Nothing -> True; other -> False}
+ no_user_default = case maybe_dm_id of {Nothing -> True; other -> False}
+
+ meth_bind = case maybe_user_bind of
+ Just bind -> bind
+ Nothing -> mk_default_bind meth_name loc
+
+ meth_prags = find_prags meth_name prags
in
- tcBindWithSigs [bndr_name] meth_bind [sig_info]
- nonRecursive (\_ -> NoPragmaInfo) `thenTc` \ (binds, insts, _) ->
- returnTc (binds, insts, meth)
- where
- (bndr_name, src_loc) = case meth_bind of
- FunMonoBind name _ _ loc -> (name, loc)
- PatMonoBind (VarPatIn name) _ loc -> (name, loc)
+ -- Warn if no method binding, only if -fwarn-missing-methods
+ if no_user_bind && not supply_default_bind then
+ pprPanic "tcMethodBind" (ppr clas <+> ppr inst_tys)
+ else
+ warnTc (opt_WarnMissingMethods && no_user_bind && no_user_default)
+ (omittedMethodWarn sel_id clas) `thenNF_Tc_`
+
+ -- Check the pragmas
+ tcExtendLocalValEnv [meth_name] [meth_id] (
+ tcPragmaSigs meth_prags
+ ) `thenTc` \ (prag_info_fn, prag_binds1, prag_lie) ->
+
+ -- Check the bindings
+ tcExtendGlobalTyVars (mkVarSet inst_tyvars) (
+ tcAddErrCtxt (methodCtxt sel_id) $
+ tcBindWithSigs NotTopLevel meth_bind [sig_info]
+ NonRecursive prag_info_fn
+ ) `thenTc` \ (binds, insts, _) ->
+
+
+ -- 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
+ tcAddErrCtxtM (sigCtxt (quotes (ppr sel_id)) (idType meth_id)) (
+ checkSigTyVars inst_tyvars `thenTc_`
+
+ returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2,
+ insts `plusLIE` prag_lie',
+ meth))
+
+ where
+ sel_name = idName sel_id
+
+ -- The renamer just puts the selector ID as the binder in the method binding
+ -- but we must use the method name; so we substitute it here. Crude but simple.
+ find_bind meth_name (FunMonoBind op_name fix matches loc)
+ | op_name == sel_name = Just (FunMonoBind meth_name fix matches loc)
+ find_bind meth_name (PatMonoBind (VarPatIn op_name) rhs loc)
+ | op_name == sel_name = Just (PatMonoBind (VarPatIn meth_name) rhs loc)
+ find_bind meth_name (AndMonoBinds b1 b2)
+ = find_bind meth_name b1 `seqMaybe` find_bind meth_name b2
+ find_bind meth_name other = Nothing -- Default case
+
+
+ -- Find the prags for this method, and replace the
+ -- selector name with the method name
+ find_prags meth_name [] = []
+ find_prags meth_name (SpecSig name ty spec loc : prags)
+ | name == sel_name = SpecSig meth_name ty spec loc : find_prags meth_name prags
+ find_prags meth_name (InlineSig name loc : prags)
+ | name == sel_name = InlineSig meth_name loc : find_prags meth_name prags
+ find_prags meth_name (NoInlineSig name loc : prags)
+ | name == sel_name = NoInlineSig meth_name loc : find_prags meth_name prags
+ find_prags meth_name (prag:prags) = find_prags meth_name prags
+
+ mk_default_bind local_meth_name loc
+ = PatMonoBind (VarPatIn local_meth_name)
+ (GRHSsAndBindsIn (unguardedRHS (default_expr loc) loc) EmptyBinds)
+ loc
+
+ default_expr loc
+ = case maybe_dm_id of
+ Just dm_id -> HsVar (getName dm_id) -- There's a default method
+ Nothing -> error_expr loc -- No default method
+
+ error_expr loc = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
+ (HsLit (HsString (_PK_ (error_msg loc))))
+
+ error_msg loc = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
\end{code}
-Contexts
-~~~~~~~~
+Contexts and errors
+~~~~~~~~~~~~~~~~~~~
\begin{code}
-classDeclCtxt class_name sty
- = hsep [ptext SLIT("In the class declaration for"), ppr sty class_name]
+classArityErr class_name
+ = ptext SLIT("Too many parameters for class") <+> quotes (ppr class_name)
+
+classDeclCtxt class_name
+ = ptext SLIT("In the class declaration for") <+> quotes (ppr class_name)
+
+superClassErr class_name sc
+ = ptext SLIT("Illegal superclass constraint") <+> quotes (pprClassAssertion sc)
+ <+> ptext SLIT("in declaration for class") <+> quotes (ppr class_name)
+
+methodCtxt sel_id
+ = ptext SLIT("In the definition for method") <+> quotes (ppr sel_id)
+
+badMethodErr bndr clas
+ = hsep [ptext SLIT("Class"), quotes (ppr clas),
+ ptext SLIT("does not have a method"), quotes (ppr bndr)]
+
+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)]
\end{code}