%
-% (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
+module TcClassDcl ( tcClassDecl1, tcClassDecls2,
+ MethodSpec, tcMethodBind, mkMethodBind, badMethodErr
+ ) where
-IMPORT_Trace -- ToDo: rm (debugging)
-import Pretty -- add proper one below
-
-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 HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..),
+ HsExpr(..), HsLit(..), Pat(WildPat),
+ mkSimpleMatch, andMonoBinds, andMonoBindList,
+ isClassOpSig, isPragSig,
+ placeHolderType
)
-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 BasicTypes ( RecFlag(..), StrictnessMark(..) )
+import RnHsSyn ( RenamedTyClDecl, RenamedSig,
+ RenamedClassOpSig, RenamedMonoBinds,
+ maybeGenericMatch
)
-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 RnEnv ( lookupSysName )
+import TcHsSyn ( TcMonoBinds )
+
+import Inst ( Inst, InstOrigin(..), instToId, newDicts, newMethodAtLoc )
+import TcEnv ( TyThingDetails(..),
+ tcLookupClass, tcExtendTyVarEnv2,
+ tcExtendTyVarEnv
+ )
+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 TcClassSig ( tcClassSigs )
-import TcContext ( tcContext )
-import TcInstDcls ( processInstBinds )
-import TcPragmas ( tcGenPragmas )
-import Util
+import TcRnMonad
+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, setInlinePragma )
+import Name ( Name, NamedThing(..) )
+import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv )
+import NameSet ( emptyNameSet, unitNameSet )
+import OccName ( mkClassTyConOcc, mkClassDataConOcc, mkWorkerOcc, mkSuperDictSelOcc )
+import Outputable
+import Var ( TyVar )
+import CmdLineOpts
+import UnicodeUtil ( stringToUtf8 )
+import ErrUtils ( dumpIfSet )
+import Util ( count, lengthIs )
+import Maybes ( seqMaybe )
+import Maybe ( isJust )
+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}
-%************************************************************************
-%* *
-\subsection[TcClassDcl]{Does the real work (apart from default methods)}
-%* *
-%************************************************************************
+Dictionary handling
+~~~~~~~~~~~~~~~~~~~
+Every class implicitly declares a new data type, corresponding to dictionaries
+of that class. So, for example:
-\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
+would implicitly declare
-%************************************************************************
-%* *
-\subsection[ClassDcl-pass2]{Class decls pass 2: default methods}
-%* *
-%************************************************************************
+ data CDict a = CDict (D a)
+ (a -> a)
+ (forall b. Ord b => a -> b -> b)
-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}
+(We could use a record decl, but that means changing more of the existing apparatus.
+One step at at time!)
-Pass~2 only applies to locally-defined class declarations.
+For classes with just one superclass+method, we use a newtype decl instead:
-The function @tcClassDecls2@ just arranges to apply
-@tcClassDecls2_help@ to each local class decl.
+ class C a where
+ op :: forallb. a -> b -> b
-\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
+generates
-tcClassDecls2_help
- :: E
- -> [TyVar]
- -> [ClassInfo]
- -> NF_TcM (LIE, TypecheckedBinds)
+ newtype CDict a = CDict (forall b. a -> b -> b)
-tcClassDecls2_help e free_tyvars [] = returnNF_Tc (nullLIE, EmptyBinds)
+Now DictTy in Type is just a form of type synomym:
+ DictTy c t = TyConTy CDict `AppTy` t
-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}
+Death to "ExpandingDicts".
-@tcClassDecl2@ is the business end of things.
-
-\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}
+\subsection{Type checking}
%* *
%************************************************************************
\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))))
+tcClassDecl1 :: RenamedTyClDecl -> TcM (Name, TyThingDetails)
+tcClassDecl1 (ClassDecl {tcdCtxt = context, tcdName = class_name,
+ tcdTyVars = tyvar_names, tcdFDs = fundeps,
+ tcdSigs = class_sigs, tcdMeths = def_methods,
+ tcdLoc = src_loc})
+ = -- LOOK THINGS UP IN THE ENVIRONMENT
+ tcLookupClass class_name `thenM` \ clas ->
+ let
+ tyvars = classTyVars clas
+ op_sigs = filter isClassOpSig class_sigs
+ op_names = [n | ClassOpSig n _ _ _ <- op_sigs]
+ in
+ tcExtendTyVarEnv tyvars $
+
+ checkDefaultBinds clas op_names def_methods `thenM` \ mb_dm_env ->
+
+ -- CHECK THE CONTEXT
+ -- The renamer has already checked that the context mentions
+ -- only the type variable of the class decl.
+ -- Context is already kind-checked
+ tcHsTheta context `thenM` \ sc_theta ->
+
+ -- CHECK THE CLASS SIGNATURES,
+ mappM (tcClassSig clas tyvars mb_dm_env) op_sigs `thenM` \ sig_stuff ->
+
+ -- MAKE THE CLASS DETAILS
+ lookupSysName class_name mkClassDataConOcc `thenM` \ datacon_name ->
+ lookupSysName datacon_name mkWorkerOcc `thenM` \ datacon_wkr_name ->
+ mapM (lookupSysName class_name . mkSuperDictSelOcc)
+ [1..length context] `thenM` \ sc_sel_names ->
+ -- We number off the superclass selectors, 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!)
+ lookupSysName class_name mkClassTyConOcc `thenM` \ tycon_name ->
+ let
+ (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
+ returnM (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con tycon_name)
\end{code}
-%************************************************************************
-%* *
-\subsection[ClassDcl-misc]{Miscellaneous}
-%* *
-%************************************************************************
+\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
+ = returnM Nothing
+
+checkDefaultBinds clas ops (Just mbs)
+ = go mbs `thenM` \ dm_env ->
+ returnM (Just dm_env)
+ where
+ go EmptyMonoBinds = returnM emptyNameEnv
-Make a selector expression for @local@ from a dictionary consisting of
-@dicts@ and @op_locals@.
+ go (AndMonoBinds b1 b2)
+ = go b1 `thenM` \ dm_info1 ->
+ go b2 `thenM` \ dm_info2 ->
+ returnM (dm_info1 `plusNameEnv` dm_info2)
-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}
+ go (FunMonoBind op _ matches loc)
+ = addSrcLoc loc $
-{\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}
+ -- Check that the op is from this class
+ checkTc (op `elem` ops) (badMethodErr clas op) `thenM_`
+
+ -- Check that all the defns ar generic, or none are
+ checkTc (all_generic || none_generic) (mixedGenericErr op) `thenM_`
+
+ returnM (unitNameEnv op all_generic)
+ where
+ n_generic = count (isJust . maybeGenericMatch) matches
+ none_generic = n_generic == 0
+ all_generic = matches `lengthIs` n_generic
+\end{code}
-WDP 95/03: Quite false (``DICTIONARY APPLICATION IS CURRIED'').
-Specialisation now wants to see all type- and dictionary-applications
-absolutely explicitly.
\begin{code}
-mkSelExpr :: InstOrigin -> TyVar -> [Id] -> [Id] -> Id -> NF_TcM TypecheckedExpr
+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 clas clas_tyvars maybe_dm_env
+ (ClassOpSig op_name sig_dm op_ty src_loc)
+ = addSrcLoc src_loc $
+
+ -- Check the type signature. NB that the envt *already has*
+ -- bindings for the type variables; see comments in TcTyAndClassDcls.
+ tcHsType op_ty `thenM` \ local_ty ->
-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
+ theta = [mkClassPred clas (mkTyVarTys clas_tyvars)]
+
+ -- Build the selector id and default method id
+ sel_id = mkDictSelId op_name clas
+ DefMeth dm_name = sig_dm
+
+ dm_info = case maybe_dm_env of
+ Nothing -> sig_dm
+ Just dm_env -> mk_src_dm_info dm_env
+
+ mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of
+ Nothing -> NoDefMeth
+ Just True -> GenDefMeth
+ Just False -> DefMeth dm_name
in
- returnNF_Tc (TyLam (clas_tyvar:op_tyvars)
- (ClassDictLam
- dicts
- op_locals
- (mkDictLam local_dicts
- (mkDictApp (mkTyApp (Var local) tys) local_dicts))))
+ returnM (local_ty, (sel_id, dm_info))
\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}
+The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to
+each local class decl.
+
+\begin{code}
+tcClassDecls2 :: [RenamedTyClDecl] -> TcM (TcMonoBinds, [Id])
+
+tcClassDecls2 decls
+ = foldr combine
+ (returnM (EmptyMonoBinds, []))
+ [tcClassDecl2 cls_decl | cls_decl@(ClassDecl {tcdMeths = Just _}) <- decls]
+ -- The 'Just' picks out source ClassDecls
+ where
+ combine tc1 tc2 = tc1 `thenM` \ (binds1, ids1) ->
+ tc2 `thenM` \ (binds2, ids2) ->
+ returnM (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}
-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'))
+tcClassDecl2 :: RenamedTyClDecl -- The class declaration
+ -> TcM (TcMonoBinds, [Id])
+
+tcClassDecl2 (ClassDecl {tcdName = class_name, tcdSigs = sigs,
+ tcdMeths = Just default_binds, tcdLoc = src_loc})
+ = -- The 'Just' picks out source ClassDecls
+ recoverM (returnM (EmptyMonoBinds, [])) $
+ addSrcLoc src_loc $
+ tcLookupClass 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 isPragSig sigs
+ tc_dm = tcDefMeth clas tyvars default_binds prags
+ in
+ mapAndUnzipM tc_dm op_items `thenM` \ (defm_binds, dm_ids_s) ->
+
+ returnM (andMonoBindList defm_binds, concat dm_ids_s)
+
+
+tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnM (EmptyMonoBinds, [])
+tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnM (EmptyMonoBinds, [])
+ -- 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 `thenM` \ (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 `thenM` \ [this_dict] ->
+
+ mkMethodBind origin clas inst_tys binds_in op_item `thenM` \ (dm_inst, meth_info) ->
+ getLIE (tcMethodBind xtve clas_tyvars theta
+ [this_dict] prags meth_info) `thenM` \ (defm_bind, insts_needed) ->
+
+ addErrCtxt (defltMethCtxt clas) $
+
+ -- Check the context
+ tcSimplifyCheck
+ (ptext SLIT("class") <+> ppr clas)
+ clas_tyvars
+ [this_dict]
+ insts_needed `thenM` \ dict_binds ->
+
+ -- Simplification can do unification
+ checkSigTyVars clas_tyvars `thenM` \ 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
+ returnM (full_bind, [dm_id])
+ where
+ origin = ClassDeclOrigin
\end{code}
-@makeClassDeclDefaultMethodRhs@ builds the default method for a
-class declaration when no explicit default method is given.
+
+
+%************************************************************************
+%* *
+\subsection{Typechecking a method}
+%* *
+%************************************************************************
+
+@tcMethodBind@ is used to type-check both default-method and
+instance-decl method declarations. We must type-check methods one at a
+time, because their signatures may have different contexts and
+tyvar sets.
\begin{code}
-makeClassDeclDefaultMethodRhs
- :: 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))))))
+type MethodSpec = (Id, -- Global selector Id
+ TcSigInfo, -- Signature
+ RenamedMonoBinds) -- Binding for the method
+
+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
+ -> [RenamedSig] -- Pragmas (e.g. inline pragmas)
+ -> MethodSpec -- Details of this method
+ -> TcM TcMonoBinds
+
+tcMethodBind xtve inst_tyvars inst_theta avail_insts prags
+ (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 (
+ addErrCtxt (methodCtxt sel_id) $
+ getLIE (tcMonoBinds meth_bind [meth_sig] NonRecursive)
+ ) `thenM` \ ((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
+ addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $
+ newDicts SignatureOrigin meth_theta `thenM` \ 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 `thenM` \ lie_binds ->
+
+ checkSigTyVars all_tyvars `thenM` \ all_tyvars' ->
+
+ let
+ -- Attach inline pragmas as appropriate
+ (final_meth_id, inlines)
+ | (InlineSig inl _ phase _ : _) <- filter is_inline prags
+ = (meth_id `setInlinePragma` phase,
+ if inl then unitNameSet (idName meth_id) else emptyNameSet)
+ | otherwise
+ = (meth_id, emptyNameSet)
+
+ is_inline (InlineSig _ name _ _) = name == idName sel_id
+ is_inline other = False
+
+ meth_tvs' = take (length meth_tvs) all_tyvars'
+ poly_meth_bind = AbsBinds meth_tvs'
+ (map instToId meth_dicts)
+ [(meth_tvs', final_meth_id, local_meth_id)]
+ inlines
+ (lie_binds `andMonoBinds` meth_bind)
+ in
+ returnM poly_meth_bind
+
+
+mkMethodBind :: InstOrigin
+ -> Class -> [TcType] -- Class and instance types
+ -> RenamedMonoBinds -- Method binding (pick the right one from in here)
+ -> ClassOpItem
+ -> TcM (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)
+ = getInstLoc origin `thenM` \ inst_loc ->
+ newMethodAtLoc inst_loc sel_id inst_tys `thenM` \ meth_inst ->
+ -- Do not dump anything into the LIE
+ let
+ meth_id = instToId meth_inst
+ 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
+ getSrcLocM `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 ->
+ returnM (FunMonoBind meth_name False -- Not infix decl
+ [mkSimpleMatch [] rhs placeHolderType loc] loc)
+ ) `thenM` \ meth_bind ->
+
+ mkTcSig meth_id loc `thenM` \ meth_sig ->
+
+ returnM (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
+ traceRn (text "mkDefMeth" <+> ppr dm_name) `thenM_`
+ returnM (HsVar 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)
+ (omittedMethodWarn sel_id) `thenM_`
+ returnM 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 = [WildPat placeHolderType | 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)) `thenM_`
+ checkTc (isJust (tyConGenInfo tycon))
+ (badGenericInstance sel_id (notGeneric tycon)) `thenM_`
+
+ ioToTcRn (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenM_`
+ returnM rhs
where
- method_id = method_ids !! (tag-1)
- class_op = (getClassOps clas) !! (tag-1)
+ 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 and errors
+~~~~~~~~~~~~~~~~~~~
+\begin{code}
+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]
- error_msg = "%D" -- => No default method for \"
- ++ unencoded_part_of_msg
+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)")]
- unencoded_part_of_msg = escErrorMsg (
- _UNPK_ clas_mod ++ "." ++ _UNPK_ clas_name ++ "."
- ++ (ppShow 80 (ppr PprForUser class_op))
- ++ "\"" )
+notGeneric tycon
+ = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+>
+ ptext SLIT("was not compiled with -fgenerics")]
- (clas_mod, clas_name) = getOrigName clas
+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