%
-% (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 (
- tcClassDecls1, tcClassDecls2,
- ClassInfo -- abstract
- ) where
-
-IMPORT_Trace -- ToDo: rm (debugging)
-import Pretty -- add proper one below
+module TcClassDcl ( tcClassSigs, tcClassDecl2,
+ getGenericInstances,
+ MethodSpec, tcMethodBind, mkMethodBind,
+ tcAddDeclCtxt, badMethodErr
+ ) where
-import TcMonad -- typechecking monad machinery
-import TcMonadFns ( newDicts, newClassOpLocals, copyTyVars )
-import AbsSyn -- the stuff being typechecked
+#include "HsVersions.h"
-import AbsPrel ( pAT_ERROR_ID )
-import AbsUniType ( mkClass, getClassKey, getClassBigSig,
- getClassOpString, getClassOps, splitType,
- mkSuperDictSelType, InstTyEnv(..),
- instantiateTy, instantiateThetaTy, UniType
- )
-import BackSubst ( applyTcSubstToBinds )
-import CE -- ( nullCE, unitCE, plusCE, CE(..), UniqFM )
-import E ( mkE, getE_TCE, getE_CE, tvOfE, nullGVE, plusGVE, E, TCE(..), UniqFM, GVE(..) )
-import Errors ( confusedNameErr, Error(..) )
-import HsPragmas -- ****** NEED TO SEE CONSTRUCTORS ******
-import Id ( mkSuperDictSelId, mkInstId, getIdUniType,
- Id, DictFun(..)
+import HsSyn
+import BasicTypes ( RecFlag(..) )
+import RnHsSyn ( maybeGenericMatch, extractHsTyVars )
+import RnExpr ( rnLExpr )
+import RnEnv ( lookupTopBndrRn, lookupImportedName )
+
+import Inst ( Inst, InstOrigin(..), instToId, newDicts, newDictsAtLoc, newMethod )
+import TcEnv ( tcLookupLocatedClass, tcExtendIdEnv2,
+ tcExtendTyVarEnv,
+ InstInfo(..), pprInstInfoDetails,
+ simpleInstInfoTyCon, simpleInstInfoTy,
+ InstBindings(..), newDFunName
)
-import IdInfo
-import Inst ( InstOrigin(..), Inst )
-import InstEnv
-import LIE ( nullLIE, mkLIE, plusLIE, LIE )
-import Maybes ( Maybe(..) )
-import Name ( Name(..) )
-import PlainCore ( escErrorMsg )
-import Spec ( specTy )
-import TVE ( mkTVE, TVE(..)
- IF_ATTACK_PRAGMAS(COMMA u2i)
+import TcBinds ( tcMonoBinds, tcSpecSigs )
+import TcHsType ( TcSigInfo(..), tcHsKindedType, tcHsSigType )
+import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
+import TcUnify ( checkSigTyVars, sigCtxt )
+import TcMType ( tcSkolSigTyVars, UserTypeCtxt( GenPatCtxt ), tcSkolType )
+import TcType ( Type, SkolemInfo(ClsSkol, InstSkol, SigSkol),
+ TcType, TcThetaType, TcTyVar, mkTyVarTys,
+ mkClassPred, tcSplitSigmaTy, tcSplitFunTys,
+ tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitForAllTys, tcSplitPhiTy,
+ getClassPredTys_maybe, mkPhiTy, mkTyVarTy
)
-import TcClassSig ( tcClassSigs )
-import TcContext ( tcContext )
-import TcInstDcls ( processInstBinds )
-import TcPragmas ( tcGenPragmas )
-import Util
+import TcRnMonad
+import Generics ( mkGenericRhs, validGenericInstanceType )
+import PrelInfo ( nO_METHOD_BINDING_ERROR_ID )
+import Class ( classTyVars, classBigSig,
+ Class, ClassOpItem, DefMeth (..) )
+import TyCon ( TyCon, tyConName, tyConHasGenerics )
+import Type ( substTyWith )
+import MkId ( mkDefaultMethodId, mkDictFunId )
+import Id ( Id, idType, idName, mkUserLocal, setInlinePragma )
+import Name ( Name, NamedThing(..) )
+import NameEnv ( NameEnv, lookupNameEnv, mkNameEnv )
+import NameSet ( emptyNameSet, unitNameSet, nameSetToList )
+import OccName ( reportIfUnused, mkDefaultMethodOcc )
+import RdrName ( RdrName, mkDerivedRdrName )
+import Outputable
+import PrelNames ( genericTyConNames )
+import CmdLineOpts
+import UnicodeUtil ( stringToUtf8 )
+import ErrUtils ( dumpIfSet_dyn )
+import Util ( count, lengthIs, isSingleton, lengthExceeds )
+import Unique ( Uniquable(..) )
+import ListSetOps ( equivClassesByUniq, minusList )
+import SrcLoc ( Located(..), srcSpanStart, unLoc, noLoc )
+import Maybes ( seqMaybe, isJust, mapCatMaybes )
+import List ( partition )
+import Bag
+import FastString
\end{code}
-@ClassInfo@ communicates the essential information about
-locally-defined classes between passes 1 and 2.
-\begin{code}
-data ClassInfo
- = ClassInfo Class
- RenamedMonoBinds
-\end{code}
+Dictionary handling
+~~~~~~~~~~~~~~~~~~~
+Every class implicitly declares a new data type, corresponding to dictionaries
+of that class. So, for example:
-%************************************************************************
-%* *
-\subsection[TcClassDcl]{Does the real work (apart from default methods)}
-%* *
-%************************************************************************
-
-\begin{code}
-tcClassDecls1
- :: E -- Consult the CE/TCE args only to build knots
- -> InstanceMapper -- Maps class name to its instances,
- -- ...and its ops to their instances,
- -> [RenamedClassDecl]
- -> TcM ([ClassInfo], -- boiled-down info related to classes
- CE, -- env so we can look up classes elsewhere
- GVE) -- env so we can look up class ops elsewhere
-
-tcClassDecls1 e rec_inst_mapper []
- = returnTc ([], nullCE, nullGVE)
-
-tcClassDecls1 e rec_inst_mapper (cd:cds)
- = tc_clas1 cd `thenTc` \ (cinfo1_maybe, ce1, gve1) ->
- tcClassDecls1 e rec_inst_mapper cds `thenTc` \ (cinfo2, ce2, gve2) ->
- let
- glued_cinfos
- = case cinfo1_maybe of
- Nothing -> cinfo2
- Just xx -> xx : cinfo2
- in
- returnTc (glued_cinfos, ce1 `plusCE` ce2, gve1 `plusGVE` gve2)
- where
- rec_ce = getE_CE e
- rec_tce = getE_TCE e
-
- tc_clas1 (ClassDecl context class_name
- tyvar_name class_sigs def_methods pragmas src_loc)
-
- = addSrcLocTc src_loc (
-
- -- The knot is needed so that the signatures etc can point
- -- back to the class itself
- fixTc (\ ~(rec_clas, _) ->
- let
- (rec_clas_inst_env, rec_class_op_inst_fn) = rec_inst_mapper rec_clas
- in
- -- Get new (template) type variables for the class
- let (tve, [clas_tyvar], [alpha]) = mkTVE [tyvar_name] in
-
- -- Typecheck the class context; since there is only one type
- -- variable in scope, we are assured that the it will be of
- -- the form (C1 a, C2 a...)
- babyTcMtoTcM (tcContext rec_ce rec_tce tve context) `thenTc` \ theta ->
-
- -- Make the superclass selector ids; the "class" pragmas
- -- may have info about the superclass dict selectors;
- -- so it is only tcClassPragmas that gives back the
- -- final Ids.
- getUniquesTc (length theta) `thenNF_Tc` \ uniqs ->
- let
- super_classes = [ supers | (supers, _) <- theta ]
- super_tys
- = [ mkSuperDictSelType rec_clas super | super <- super_classes ]
- super_info = zip3 super_classes uniqs super_tys
- in
- (case pragmas of
- NoClassPragmas ->
- returnNF_Tc [ mk_super_id rec_clas info noIdInfo | info <- super_info ]
-
- SuperDictPragmas prags ->
--- pprTrace "SuperDictPragmas:" (ppAboves (ppr PprDebug prags : map pp super_info)) (
- mapNF_Tc (mk_super_id_w_info rec_clas) (super_info `zipEqual` prags)
--- )
--- where
--- pp (sc, u, ty) = ppCat [ppr PprDebug sc, ppr PprDebug ty]
-
- ) `thenNF_Tc` \ super_class_sel_ids ->
-
- -- Typecheck the class signatures, checking that each mentions
- -- the class type variable somewhere, and manufacturing
- -- suitable Ids for selectors and default methods.
- babyTcMtoTcM
- (tcClassSigs e tve rec_clas rec_class_op_inst_fn
- clas_tyvar defm_names class_sigs)
- `thenTc` \ (ops, ops_gve, op_sel_ids, defm_ids) ->
-
- -- Make the class object itself, producing clas::Class
- let
- clas
- = mkClass class_name clas_tyvar
- super_classes super_class_sel_ids
- ops op_sel_ids defm_ids
- rec_clas_inst_env
- in
- returnTc (clas, ops_gve)
- ) `thenTc` \ (clas, ops_gve) ->
-
- -- Return the class decl for further work if it is
- -- local, otherwise just return the CE
- returnTc (if (isLocallyDefined class_name) then
- Just (ClassInfo clas def_methods)
- else
- Nothing,
- unitCE (getClassKey clas) clas,
- ops_gve
- ))
- where
- defm_names = collectMonoBinders def_methods
-
- -----------
- mk_super_id clas (super_clas, uniq, ty) id_info
- = mkSuperDictSelId uniq clas super_clas ty id_info
-
- -----------
- mk_super_id_w_info clas ((super_clas, uniq, ty), gen_prags)
- = fixNF_Tc ( \ rec_super_id ->
- babyTcMtoNF_TcM
- (tcGenPragmas e{-fake_E-} Nothing{-ty unknown-} rec_super_id gen_prags)
- `thenNF_Tc` \ id_info ->
-
- returnNF_Tc(mkSuperDictSelId uniq clas super_clas ty id_info)
- )
-
-{- SOMETHING LIKE THIS NEEDED? ToDo [WDP]
- tc_clas1 (ClassDecl _ bad_name _ _ _ _ src_loc)
- = failTc (confusedNameErr
- "Bad name for a class (a type constructor, or Prelude name?)"
- bad_name src_loc)
--}
-\end{code}
-
+ class (D a) => C a where
+ op1 :: a -> a
+ op2 :: forall b. Ord b => a -> b -> b
-%************************************************************************
-%* *
-\subsection[ClassDcl-pass2]{Class decls pass 2: default methods}
-%* *
-%************************************************************************
+would implicitly declare
-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
-\end{enumerate}
+ data CDict a = CDict (D a)
+ (a -> a)
+ (forall b. Ord b => a -> b -> b)
-Pass~2 only applies to locally-defined class declarations.
+(We could use a record decl, but that means changing more of the existing apparatus.
+One step at at time!)
-The function @tcClassDecls2@ just arranges to apply
-@tcClassDecls2_help@ to each local class decl.
+For classes with just one superclass+method, we use a newtype decl instead:
-\begin{code}
-tcClassDecls2 e class_info
- = let
- -- Get type variables free in environment. Sadly, there may be
- -- some, because of the dreaded monomorphism restriction
- free_tyvars = tvOfE e
- in
- tcClassDecls2_help e free_tyvars class_info
+ class C a where
+ op :: forallb. a -> b -> b
-tcClassDecls2_help
- :: E
- -> [TyVar]
- -> [ClassInfo]
- -> NF_TcM (LIE, TypecheckedBinds)
+generates
-tcClassDecls2_help e free_tyvars [] = returnNF_Tc (nullLIE, EmptyBinds)
+ newtype CDict a = CDict (forall b. a -> b -> b)
-tcClassDecls2_help e free_tyvars ((ClassInfo clas default_binds) : rest)
- = tcClassDecl2 e free_tyvars clas default_binds `thenNF_Tc` \ (lie1, binds1) ->
- tcClassDecls2_help e free_tyvars rest `thenNF_Tc` \ (lie2, binds2) ->
- returnNF_Tc (lie1 `plusLIE` lie2, binds1 `ThenBinds` binds2)
-\end{code}
+Now DictTy in Type is just a form of type synomym:
+ DictTy c t = TyConTy CDict `AppTy` t
-@tcClassDecl2@ is the business end of things.
+Death to "ExpandingDicts".
-\begin{code}
-tcClassDecl2 :: E
- -> [TyVar] -- Free in the envt
- -> Class
- -> RenamedMonoBinds -- The default decls
- -> NF_TcM (LIE, TypecheckedBinds)
-
-tcClassDecl2 e free_tyvars clas default_binds
- = let
- src_loc = getSrcLoc clas
- origin = ClassDeclOrigin src_loc
- (clas_tyvar_tmpl, scs, sc_sel_ids, ops, op_sel_ids, defm_ids)
- = getClassBigSig clas
- in
- -- Prune the substitution when we are finished, and arrange error recovery
- recoverTc (nullLIE, EmptyBinds) (
- addSrcLocTc src_loc (
- pruneSubstTc free_tyvars (
-
- -- Generate bindings for the selector functions
- buildSelectors origin clas clas_tyvar_tmpl scs sc_sel_ids ops op_sel_ids
- `thenNF_Tc` \ sel_binds ->
- -- Ditto for the methods
- buildDefaultMethodBinds e free_tyvars origin clas clas_tyvar_tmpl
- defm_ids default_binds `thenTc` \ (const_insts, meth_binds) ->
-
- -- Back-substitute through the definitions
- applyTcSubstToInsts const_insts `thenNF_Tc` \ final_const_insts ->
- applyTcSubstToBinds (sel_binds `ThenBinds` meth_binds) `thenNF_Tc` \ final_binds ->
- returnTc (mkLIE final_const_insts, final_binds)
- )))
-\end{code}
%************************************************************************
%* *
-\subsection[ClassDcl-bld-sels]{Building the selector functions for methods and superclasses}
+ Type-checking the class op signatures
%* *
%************************************************************************
\begin{code}
-buildSelectors :: InstOrigin
- -> Class -- The class object
- -> TyVarTemplate -- Class type variable
- -> [Class] -> [Id] -- Superclasses and selectors
- -> [ClassOp] -> [Id] -- Class ops and selectors
- -> NF_TcM TypecheckedBinds
-
-buildSelectors origin clas clas_tyvar_tmpl
- scs sc_sel_ids
- ops op_sel_ids
- =
- -- Instantiate the class variable
- copyTyVars [clas_tyvar_tmpl] `thenNF_Tc` \ (inst_env, [clas_tyvar], [clas_tyvar_ty]) ->
- -- Make an Inst for each class op, and
- -- dicts for the superclasses. These are used to
- -- construct the selector functions
- newClassOpLocals inst_env ops `thenNF_Tc` \ method_ids ->
- newDicts origin [ (super_clas, clas_tyvar_ty)
- | super_clas <- scs
- ] `thenNF_Tc` \ dicts ->
- let dict_ids = map mkInstId dicts in
-
- -- Make suitable bindings for the selectors
- let mk_op_sel op sel_id method_id
- = mkSelExpr origin clas_tyvar dict_ids method_ids method_id `thenNF_Tc` \ rhs ->
- returnNF_Tc (VarMonoBind sel_id rhs)
- mk_sc_sel sc sel_id dict_id
- = mkSelExpr origin clas_tyvar dict_ids method_ids dict_id `thenNF_Tc` \ rhs ->
- returnNF_Tc (VarMonoBind sel_id rhs)
- in
- listNF_Tc (zipWith3 mk_op_sel ops op_sel_ids method_ids) `thenNF_Tc` \ op_sel_binds ->
- listNF_Tc (zipWith3 mk_sc_sel scs sc_sel_ids dict_ids) `thenNF_Tc` \ sc_sel_binds ->
-
- returnNF_Tc (SingleBind (
- NonRecBind (
- foldr AndMonoBinds EmptyMonoBinds (
- op_sel_binds ++ sc_sel_binds))))
-\end{code}
-
-%************************************************************************
-%* *
-\subsection[ClassDcl-misc]{Miscellaneous}
-%* *
-%************************************************************************
+tcClassSigs :: Name -- Name of the class
+ -> [LSig Name]
+ -> LHsBinds Name
+ -> TcM [TcMethInfo]
+
+type TcMethInfo = (Name, DefMeth, Type) -- A temporary intermediate, to communicate
+ -- between tcClassSigs and buildClass
+tcClassSigs clas sigs def_methods
+ = do { dm_env <- checkDefaultBinds clas op_names def_methods
+ ; mappM (tcClassSig dm_env) op_sigs }
+ where
+ op_sigs = [sig | sig@(L _ (Sig _ _)) <- sigs]
+ op_names = [n | sig@(L _ (Sig (L _ n) _)) <- op_sigs]
-Make a selector expression for @local@ from a dictionary consisting of
-@dicts@ and @op_locals@.
-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 = /\ab -> \dFoo -> case dFoo of
- (op1_method,op2_method) -> op1_method b
-\end{verbatim}
-Note that the type variable for \tr{b} is lifted to the top big lambda, and
-\tr{op1_method} is applied to it. 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}
+checkDefaultBinds :: Name -> [Name] -> LHsBinds Name -> TcM (NameEnv Bool)
+ -- 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 Bool
+ -- where True <=> it's a generic default method
+checkDefaultBinds clas ops binds
+ = do dm_infos <- mapM (addLocM (checkDefaultBind clas ops)) (bagToList binds)
+ return (mkNameEnv dm_infos)
-{\em NOTE:}
-We could do the same thing for the dictionaries, giving
-\begin{verbatim}
- op1_sel = /\ab -> \dFoo -> \dOrd -> case dFoo of
- (m1,m2) -> m1 b dOrd
-\end{verbatim}
-but WE ASSUME THAT DICTIONARY APPLICATION IS CURRIED, so the two are
-precisely equivalent, and have the same type, namely
-\begin{verbatim}
- op1_sel :: forall a b. Foo a -> Ord b -> a -> b -> a
-\end{verbatim}
-
-WDP 95/03: Quite false (``DICTIONARY APPLICATION IS CURRIED'').
-Specialisation now wants to see all type- and dictionary-applications
-absolutely explicitly.
+checkDefaultBind clas ops (FunBind (L _ op) _ (MatchGroup matches _))
+ = do { -- Check that the op is from this class
+ checkTc (op `elem` ops) (badMethodErr clas op)
-\begin{code}
-mkSelExpr :: InstOrigin -> TyVar -> [Id] -> [Id] -> Id -> NF_TcM TypecheckedExpr
+ -- Check that all the defns ar generic, or none are
+ ; checkTc (all_generic || none_generic) (mixedGenericErr op)
-mkSelExpr origin clas_tyvar dicts op_locals local
- = let
- (op_tyvar_tmpls,local_theta,_) = splitType (getIdUniType local)
- in
- copyTyVars op_tyvar_tmpls `thenNF_Tc` \ (inst_env, op_tyvars, tys) ->
- let
- inst_theta = instantiateThetaTy inst_env local_theta
- in
- newDicts origin inst_theta `thenNF_Tc` \ local_dict_insts ->
- let
- local_dicts = map mkInstId local_dict_insts
- in
- returnNF_Tc (TyLam (clas_tyvar:op_tyvars)
- (ClassDictLam
- dicts
- op_locals
- (mkDictLam local_dicts
- (mkDictApp (mkTyApp (Var local) tys) local_dicts))))
+ ; returnM (op, all_generic)
+ }
+ where
+ n_generic = count (isJust . maybeGenericMatch) matches
+ none_generic = n_generic == 0
+ all_generic = matches `lengthIs` n_generic
+
+
+tcClassSig :: NameEnv Bool -- Info about default methods;
+ -> LSig Name
+ -> TcM TcMethInfo
+
+tcClassSig dm_env (L loc (Sig (L _ op_name) op_hs_ty))
+ = setSrcSpan loc $ do
+ { op_ty <- tcHsKindedType op_hs_ty -- Class tyvars already in scope
+ ; let dm = case lookupNameEnv dm_env op_name of
+ Nothing -> NoDefMeth
+ Just False -> DefMeth
+ Just True -> GenDefMeth
+ ; returnM (op_name, dm, op_ty) }
\end{code}
defm.Foo.op1 :: forall a. Foo a => a -> Bool
defm.Foo.op1 = /\a -> \dfoo -> \x -> True
-defm.Foo.op2 :: forall a, b. (Foo a, Ord b) => a -> b -> b -> b
-defm.Foo.op2 = /\ a b -> \ dfoo dord -> \x y z ->
+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}
-Notice that, like all ids, the foralls of defm.Foo.op2 are at the top.
When we come across an instance decl, we may need to use the default
methods:
const.Foo.Int.op1 = defm.Foo.op1 Int dfun.Foo.Int
const.Foo.Int.op2 :: forall b. Ord b => Int -> b -> b -> b
-const.Foo.Int.op2 = /\b -> defm.Foo.op2 Int b dfun.Foo.Int
+const.Foo.Int.op2 = defm.Foo.op2 Int dfun.Foo.Int
dfun.Foo.Int :: Foo Int
dfun.Foo.Int = (const.Foo.Int.op1, const.Foo.Int.op2)
\end{verbatim}
Notice that, as with method selectors above, we assume that dictionary
application is curried, so there's no need to mention the Ord dictionary
-in const.Foo.Int.op2
+in const.Foo.Int.op2 (or the type variable).
+
\begin{verbatim}
instance Foo a => Foo [a] where {}
= /\ a -> \ dfoo_a ->
let rec
op1 = defm.Foo.op1 [a] dfoo_list
- op2 = /\b -> defm.Foo.op2 [a] b dfoo_list
+ op2 = defm.Foo.op2 [a] dfoo_list
dfoo_list = (op1, op2)
in
dfoo_list
\end{verbatim}
+@tcClassDecls2@ generates bindings for polymorphic default methods
+(generic default methods have by now turned into instance declarations)
+
+\begin{code}
+tcClassDecl2 :: LTyClDecl Name -- The class declaration
+ -> TcM (LHsBinds Id, [Id])
+
+tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs,
+ tcdMeths = default_binds}))
+ = recoverM (returnM (emptyLHsBinds, [])) $
+ setSrcSpan loc $
+ tcLookupLocatedClass class_name `thenM` \ clas ->
+
+ -- We make a separate binding for each default method.
+ -- At one time I used a single AbsBinds for all of them, thus
+ -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... }
+ -- But that desugars into
+ -- ds = \d -> (..., ..., ...)
+ -- dm1 = \d -> case ds d of (a,b,c) -> a
+ -- And since ds is big, it doesn't get inlined, so we don't get good
+ -- default methods. Better to make separate AbsBinds for each
+ let
+ (tyvars, _, _, op_items) = classBigSig clas
+ prags = filter isPragLSig sigs
+ tc_dm = tcDefMeth clas tyvars default_binds prags
+
+ dm_sel_ids = [sel_id | (sel_id, DefMeth) <- op_items]
+ -- 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.)
+ in
+ mapAndUnzipM tc_dm dm_sel_ids `thenM` \ (defm_binds, dm_ids_s) ->
+ returnM (listToBag defm_binds, concat dm_ids_s)
+
+tcDefMeth clas tyvars binds_in prags sel_id
+ = do { dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_id)
+ ; let rigid_info = ClsSkol clas
+ clas_tyvars = tcSkolSigTyVars rigid_info tyvars
+ inst_tys = mkTyVarTys clas_tyvars
+ dm_ty = idType sel_id -- Same as dict selector!
+ theta = [mkClassPred clas inst_tys]
+ local_dm_id = mkDefaultMethodId dm_name dm_ty
+ origin = SigOrigin rigid_info
+
+ ; (_, meth_info) <- mkMethodBind origin clas inst_tys binds_in (sel_id, DefMeth)
+ ; [this_dict] <- newDicts origin theta
+ ; (defm_bind, insts_needed) <- getLIE (tcMethodBind clas_tyvars theta
+ [this_dict] prags meth_info)
+
+ ; addErrCtxt (defltMethCtxt clas) $ do
+
+ -- Check the context
+ { dict_binds <- tcSimplifyCheck
+ (ptext SLIT("class") <+> ppr clas)
+ clas_tyvars
+ [this_dict]
+ insts_needed
+
+ -- Simplification can do unification
+ ; checkSigTyVars clas_tyvars
+
+ ; let
+ (_,dm_inst_id,_) = meth_info
+ full_bind = AbsBinds
+ clas_tyvars
+ [instToId this_dict]
+ [(clas_tyvars, local_dm_id, dm_inst_id)]
+ emptyNameSet -- No inlines (yet)
+ (dict_binds `unionBags` defm_bind)
+ ; returnM (noLoc full_bind, [local_dm_id]) }}
+
+mkDefMethRdrName :: Id -> RdrName
+mkDefMethRdrName sel_id = mkDerivedRdrName (idName sel_id) mkDefaultMethodOcc
+\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
+tyvar sets.
+
\begin{code}
-buildDefaultMethodBinds
- :: E
- -> [TyVar]
- -> InstOrigin
- -> Class
- -> TyVarTemplate
- -> [Id]
- -> RenamedMonoBinds
- -> TcM ([Inst], TypecheckedBinds)
-
-buildDefaultMethodBinds e free_tyvars origin clas clas_tyvar_tmpl
- default_method_ids default_binds
- = -- Deal with the method declarations themselves
- processInstBinds e
- free_tyvars
- (makeClassDeclDefaultMethodRhs clas origin default_method_ids)
- [] -- No tyvars in scope for "this inst decl"
- [] -- No insts available
- default_method_ids
- default_binds `thenTc` \ (dicts_needed, default_binds') ->
-
- returnTc (dicts_needed, SingleBind (NonRecBind default_binds'))
+type MethodSpec = (Id, -- Global selector Id
+ Id, -- Local Id (class tyvars instantiated)
+ LHsBind Name) -- Binding for the method
+
+tcMethodBind
+ :: [TcTyVar] -- Skolemised type variables for the
+ -- enclosing class/instance decl.
+ -- They'll be signature tyvars, and we
+ -- want to check that they don't get bound
+ -- Also they are scoped, so we bring them into scope
+ -- 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
+ -> [LSig Name] -- Pragmas (e.g. inline pragmas)
+ -> MethodSpec -- Details of this method
+ -> TcM (LHsBinds Id)
+
+tcMethodBind inst_tyvars inst_theta avail_insts prags
+ (sel_id, meth_id, meth_bind)
+ = recoverM (returnM emptyLHsBinds) $
+ -- If anything fails, recover returning no bindings.
+ -- This is particularly useful when checking the default-method binding of
+ -- a class decl. If we don't recover, we don't add the default method to
+ -- the type enviroment, and we get a tcLookup failure on $dmeth later.
+
+ -- Check the bindings; first adding inst_tyvars to the envt
+ -- so that we don't quantify over them in nested places
+
+
+ let -- Fake up a TcSigInfo to pass to tcMonoBinds
+ rigid_info = SigSkol (idName meth_id)
+ in
+ tcSkolType rigid_info (idType meth_id) `thenM` \ (tyvars', theta', tau') ->
+ getInstLoc (SigOrigin rigid_info) `thenM` \ loc ->
+ let meth_sig = TcSigInfo { sig_id = meth_id, sig_tvs = tyvars', sig_scoped = [],
+ sig_theta = theta', sig_tau = tau', sig_loc = loc }
+ lookup_sig name = ASSERT( name == idName meth_id )
+ Just meth_sig
+ in
+ tcExtendTyVarEnv inst_tyvars (
+ addErrCtxt (methodCtxt sel_id) $
+ getLIE $
+ tcMonoBinds (unitBag meth_bind) lookup_sig NonRecursive
+ ) `thenM` \ ((meth_bind, mono_bind_infos), 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
+
+ addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $
+ newDictsAtLoc (sig_loc meth_sig) (sig_theta meth_sig) `thenM` \ meth_dicts ->
+ let
+ meth_tvs = sig_tvs meth_sig
+ 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 `thenM` \ lie_binds ->
+
+ checkSigTyVars all_tyvars `thenM_`
+
+ let
+ sel_name = idName sel_id
+ inline_prags = [ (is_inl, phase)
+ | L _ (InlineSig is_inl (L _ name) phase) <- prags,
+ name == sel_name ]
+ spec_prags = [ prag
+ | prag@(L _ (SpecSig (L _ name) _)) <- prags,
+ name == sel_name]
+
+ -- Attach inline pragmas as appropriate
+ (final_meth_id, inlines)
+ | ((is_inline, phase) : _) <- inline_prags
+ = (meth_id `setInlinePragma` phase,
+ if is_inline then unitNameSet (idName meth_id) else emptyNameSet)
+ | otherwise
+ = (meth_id, emptyNameSet)
+
+ [(_,_,local_meth_id)] = mono_bind_infos
+ poly_meth_bind = noLoc $ AbsBinds meth_tvs
+ (map instToId meth_dicts)
+ [(meth_tvs, final_meth_id, local_meth_id)]
+ inlines
+ (lie_binds `unionBags` meth_bind)
+
+ in
+ -- Deal with specialisation pragmas
+ -- The sel_name is what appears in the pragma
+ tcExtendIdEnv2 [(sel_name, final_meth_id)] (
+ getLIE (tcSpecSigs spec_prags) `thenM` \ (spec_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 [final_meth_id] `thenM` \ spec_binds2 ->
+ returnM (spec_binds1 `unionBags` spec_binds2)
+ ) `thenM` \ spec_binds ->
+
+ returnM (poly_meth_bind `consBag` spec_binds)
+
+
+mkMethodBind :: InstOrigin
+ -> Class -> [TcType] -- Class and instance types
+ -> LHsBinds Name -- Method binding (pick the right one from in here)
+ -> ClassOpItem
+ -> TcM (Maybe Inst, -- Method inst
+ MethodSpec)
+-- Find the binding for the specified method, or make
+-- up a suitable default method if it isn't there
+
+mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info)
+ = mkMethId origin clas sel_id inst_tys `thenM` \ (mb_inst, meth_id) ->
+ let
+ meth_name = idName meth_id
+ in
+ -- Figure out what method binding to use
+ -- If the user suppplied one, use it, else construct a default one
+ getSrcSpanM `thenM` \ loc ->
+ (case find_bind (idName sel_id) meth_name meth_binds of
+ Just user_bind -> returnM user_bind
+ Nothing ->
+ mkDefMethRhs origin clas inst_tys sel_id loc dm_info `thenM` \ rhs ->
+ -- Not infix decl
+ returnM (noLoc $ FunBind (noLoc meth_name) False
+ (mkMatchGroup [mkSimpleMatch [] rhs]))
+ ) `thenM` \ meth_bind ->
+
+ returnM (mb_inst, (sel_id, meth_id, meth_bind))
+
+mkMethId :: InstOrigin -> Class
+ -> Id -> [TcType] -- Selector, and instance types
+ -> TcM (Maybe Inst, Id)
+
+-- mkMethId instantiates the selector Id at the specified types
+mkMethId origin clas sel_id inst_tys
+ = let
+ (tyvars,rho) = tcSplitForAllTys (idType sel_id)
+ rho_ty = ASSERT( length tyvars == length inst_tys )
+ substTyWith tyvars inst_tys rho
+ (preds,tau) = tcSplitPhiTy rho_ty
+ first_pred = head preds
+ in
+ -- The first predicate should be of form (C a b)
+ -- where C is the class in question
+ ASSERT( not (null preds) &&
+ case getClassPredTys_maybe first_pred of
+ { Just (clas1,tys) -> clas == clas1 ; Nothing -> False }
+ )
+ if isSingleton preds then
+ -- If it's the only one, make a 'method'
+ getInstLoc origin `thenM` \ inst_loc ->
+ newMethod inst_loc sel_id inst_tys preds tau `thenM` \ meth_inst ->
+ returnM (Just meth_inst, instToId meth_inst)
+ else
+ -- If it's not the only one we need to be careful
+ -- For example, given 'op' defined thus:
+ -- class Foo a where
+ -- op :: (?x :: String) => a -> a
+ -- (mkMethId op T) should return an Inst with type
+ -- (?x :: String) => T -> T
+ -- That is, the class-op's context is still there.
+ -- BUT: it can't be a Method any more, because it breaks
+ -- INVARIANT 2 of methods. (See the data decl for Inst.)
+ newUnique `thenM` \ uniq ->
+ getSrcSpanM `thenM` \ loc ->
+ let
+ real_tau = mkPhiTy (tail preds) tau
+ meth_id = mkUserLocal (getOccName sel_id) uniq real_tau
+ (srcSpanStart loc) --TODO
+ in
+ returnM (Nothing, meth_id)
+
+ -- 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
+ = -- An polymorphic default method
+ lookupImportedName (mkDefMethRdrName sel_id) `thenM` \ dm_name ->
+ -- Might not be imported, but will be an OrigName
+ traceRn (text "mkDefMeth" <+> ppr dm_name) `thenM_`
+ returnM (nlHsVar dm_name)
+
+mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth
+ = -- No default method
+ -- Warn only if -fwarn-missing-methods
+ doptM Opt_WarnMissingMethods `thenM` \ warn ->
+ warnTc (isInstDecl origin
+ && warn
+ && reportIfUnused (getOccName sel_id))
+ (omittedMethodWarn sel_id) `thenM_`
+ returnM error_rhs
+ where
+ error_rhs = noLoc $ HsLam (mkMatchGroup [mkSimpleMatch wild_pats simple_rhs])
+ simple_rhs = nlHsApp (nlHsVar (getName nO_METHOD_BINDING_ERROR_ID))
+ (nlHsLit (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 = [nlWildPat | 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
+ do { checkTc (isJust maybe_tycon)
+ (badGenericInstance sel_id (notSimple inst_tys))
+ ; checkTc (tyConHasGenerics tycon)
+ (badGenericInstance sel_id (notGeneric tycon))
+
+ ; dflags <- getDOpts
+ ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Filling in method body"
+ (vcat [ppr clas <+> ppr inst_tys,
+ nest 2 (ppr sel_id <+> equals <+> ppr rhs)]))
+
+ -- Rename it before returning it
+ ; (rn_rhs, _) <- rnLExpr rhs
+ ; returnM rn_rhs }
+ where
+ rhs = mkGenericRhs sel_id clas_tyvar tycon
+
+ -- 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 (SigOrigin (InstSkol _)) = True
+isInstDecl (SigOrigin (ClsSkol _)) = False
\end{code}
-@makeClassDeclDefaultMethodRhs@ builds the default method for a
-class declaration when no explicit default method is given.
\begin{code}
-makeClassDeclDefaultMethodRhs
- :: Class
- -> InstOrigin
- -> [Id]
- -> Int
- -> NF_TcM TypecheckedExpr
-
-makeClassDeclDefaultMethodRhs clas origin method_ids tag
- = specTy origin (getIdUniType method_id) `thenNF_Tc` \ (tyvars, dicts, tau) ->
-
- returnNF_Tc (mkTyLam tyvars (
- mkDictLam (map mkInstId dicts) (
- App (mkTyApp (Var pAT_ERROR_ID) [tau])
- (Lit (StringLit (_PK_ error_msg))))))
+-- 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 binds
+ = foldlBag seqMaybe Nothing (mapBag f binds)
+ where
+ f (L loc1 (FunBind (L loc2 op_name) fix matches)) | op_name == sel_name
+ = Just (L loc1 (FunBind (L loc2 meth_name) fix matches))
+ f _other = Nothing
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{Extracting generic instance declaration from class declarations}
+%* *
+%************************************************************************
+
+@getGenericInstances@ extracts the generic instance declarations from a class
+declaration. For exmaple
+
+ class C a where
+ op :: a -> a
+
+ op{ x+y } (Inl v) = ...
+ op{ x+y } (Inr v) = ...
+ op{ x*y } (v :*: w) = ...
+ op{ 1 } Unit = ...
+
+gives rise to the instance declarations
+
+ instance C (x+y) where
+ op (Inl v) = ...
+ op (Inr v) = ...
+
+ instance C (x*y) where
+ op (v :*: w) = ...
+
+ instance C 1 where
+ op Unit = ...
+
+
+\begin{code}
+getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo]
+getGenericInstances class_decls
+ = do { gen_inst_infos <- mappM (addLocM get_generics) class_decls
+ ; let { gen_inst_info = concat gen_inst_infos }
+
+ -- Return right away if there is no generic stuff
+ ; if null gen_inst_info then returnM []
+ else do
+
+ -- Otherwise print it out
+ { dflags <- getDOpts
+ ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances"
+ (vcat (map pprInstInfoDetails gen_inst_info)))
+ ; returnM gen_inst_info }}
+
+get_generics decl@(ClassDecl {tcdLName = class_name, tcdMeths = def_methods})
+ | null generic_binds
+ = returnM [] -- The comon case: no generic default methods
+
+ | otherwise -- A source class decl with generic default methods
+ = recoverM (returnM []) $
+ tcAddDeclCtxt decl $
+ tcLookupLocatedClass class_name `thenM` \ clas ->
+
+ -- Group by type, and
+ -- make an InstInfo out of each group
+ let
+ groups = groupWith listToBag generic_binds
+ in
+ mappM (mkGenericInstance clas) groups `thenM` \ inst_infos ->
+
+ -- Check that there is only one InstInfo for each type constructor
+ -- The main way this can fail is if you write
+ -- f {| a+b |} ... = ...
+ -- f {| x+y |} ... = ...
+ -- Then at this point we'll have an InstInfo for each
+ let
+ tc_inst_infos :: [(TyCon, InstInfo)]
+ tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos]
+
+ bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos,
+ group `lengthExceeds` 1]
+ get_uniq (tc,_) = getUnique tc
+ in
+ mappM (addErrTc . dupGenericInsts) bad_groups `thenM_`
+
+ -- Check that there is an InstInfo for each generic type constructor
+ let
+ missing = genericTyConNames `minusList` [tyConName tc | (tc,_) <- tc_inst_infos]
+ in
+ checkTc (null missing) (missingGenericInstances missing) `thenM_`
+
+ returnM inst_infos
where
- method_id = method_ids !! (tag-1)
- class_op = (getClassOps clas) !! (tag-1)
+ generic_binds :: [(HsType Name, LHsBind Name)]
+ generic_binds = getGenericBinds def_methods
- error_msg = "%D" -- => No default method for \"
- ++ unencoded_part_of_msg
- unencoded_part_of_msg = escErrorMsg (
- _UNPK_ clas_mod ++ "." ++ _UNPK_ clas_name ++ "."
- ++ (ppShow 80 (ppr PprForUser class_op))
- ++ "\"" )
+---------------------------------
+getGenericBinds :: LHsBinds Name -> [(HsType Name, LHsBind Name)]
+ -- Takes a group of method bindings, finds the generic ones, and returns
+ -- them in finite map indexed by the type parameter in the definition.
+getGenericBinds binds = concat (map getGenericBind (bagToList binds))
- (clas_mod, clas_name) = getOrigName clas
+getGenericBind (L loc (FunBind id infixop (MatchGroup matches ty)))
+ = groupWith wrap (mapCatMaybes maybeGenericMatch matches)
+ where
+ wrap ms = L loc (FunBind id infixop (MatchGroup ms ty))
+getGenericBind _
+ = []
+
+groupWith :: ([a] -> b) -> [(HsType Name, a)] -> [(HsType Name, b)]
+groupWith op [] = []
+groupWith op ((t,v):prs) = (t, op (v:vs)) : groupWith op rest
+ where
+ vs = map snd this
+ (this,rest) = partition same_t prs
+ same_t (t',v) = t `eqPatType` t'
+
+eqPatLType :: LHsType Name -> LHsType Name -> Bool
+eqPatLType t1 t2 = unLoc t1 `eqPatType` unLoc t2
+
+eqPatType :: HsType Name -> HsType Name -> Bool
+-- A very simple equality function, only for
+-- type patterns in generic function definitions.
+eqPatType (HsTyVar v1) (HsTyVar v2) = v1==v2
+eqPatType (HsAppTy s1 t1) (HsAppTy s2 t2) = s1 `eqPatLType` s2 && t2 `eqPatLType` t2
+eqPatType (HsOpTy s1 op1 t1) (HsOpTy s2 op2 t2) = s1 `eqPatLType` s2 && t2 `eqPatLType` t2 && unLoc op1 == unLoc op2
+eqPatType (HsNumTy n1) (HsNumTy n2) = n1 == n2
+eqPatType (HsParTy t1) t2 = unLoc t1 `eqPatType` t2
+eqPatType t1 (HsParTy t2) = t1 `eqPatType` unLoc t2
+eqPatType _ _ = False
+
+---------------------------------
+mkGenericInstance :: Class
+ -> (HsType Name, LHsBinds Name)
+ -> TcM InstInfo
+
+mkGenericInstance clas (hs_ty, binds)
+ -- Make a generic instance declaration
+ -- For example: instance (C a, C b) => C (a+b) where { binds }
+
+ = -- Extract the universally quantified type variables
+ -- and wrap them as forall'd tyvars, so that kind inference
+ -- works in the standard way
+ let
+ sig_tvs = map (noLoc.UserTyVar) (nameSetToList (extractHsTyVars (noLoc hs_ty)))
+ hs_forall_ty = noLoc $ mkExplicitHsForAllTy sig_tvs (noLoc []) (noLoc hs_ty)
+ in
+ -- Type-check the instance type, and check its form
+ tcHsSigType GenPatCtxt hs_forall_ty `thenM` \ forall_inst_ty ->
+ let
+ (tyvars, inst_ty) = tcSplitForAllTys forall_inst_ty
+ in
+ checkTc (validGenericInstanceType inst_ty)
+ (badGenericInstanceType binds) `thenM_`
+
+ -- Make the dictionary function.
+ getSrcSpanM `thenM` \ span ->
+ newDFunName clas [inst_ty] (srcSpanStart span) `thenM` \ dfun_name ->
+ let
+ inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars]
+ dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty]
+ in
+
+ returnM (InstInfo { iDFunId = dfun_id, iBinds = VanillaInst binds [] })
+\end{code}
+
+
+%************************************************************************
+%* *
+ Error messages
+%* *
+%************************************************************************
+
+\begin{code}
+tcAddDeclCtxt decl thing_inside
+ = addErrCtxt ctxt thing_inside
+ where
+ thing = case decl of
+ ClassDecl {} -> "class"
+ TySynonym {} -> "type synonym"
+ TyData {tcdND = NewType} -> "newtype"
+ TyData {tcdND = DataType} -> "data type"
+
+ ctxt = hsep [ptext SLIT("In the"), text thing,
+ ptext SLIT("declaration for"), quotes (ppr (tcdName decl))]
+
+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")]
+
+badGenericInstanceType binds
+ = vcat [ptext SLIT("Illegal type pattern in the generic bindings"),
+ nest 4 (ppr binds)]
+
+missingGenericInstances missing
+ = ptext SLIT("Missing type patterns for") <+> pprQuotedList missing
+
+dupGenericInsts tc_inst_infos
+ = vcat [ptext SLIT("More than one type pattern for a single generic type constructor:"),
+ nest 4 (vcat (map ppr_inst_ty tc_inst_infos)),
+ ptext SLIT("All the type patterns for a generic type constructor must be identical")
+ ]
+ where
+ ppr_inst_ty (tc,inst) = ppr tc <+> ppr (simpleInstInfoTy inst)
+
+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