\section[TcClassDcl]{Typechecking class declarations}
\begin{code}
-#include "HsVersions.h"
-
-module TcClassDcl (
- tcClassDecls1, tcClassDecls2,
- ClassInfo -- abstract
- ) where
+module TcClassDcl ( tcClassDecl1, tcClassDecls2, tcMethodBind, badMethodErr ) where
-IMPORT_Trace -- ToDo: rm (debugging)
-import Pretty -- add proper one below
+#include "HsVersions.h"
-import TcMonad -- typechecking monad machinery
-import TcMonadFns ( newDicts, newClassOpLocals, copyTyVars )
-import AbsSyn -- the stuff being typechecked
+import HsSyn ( HsDecl(..), ClassDecl(..), Sig(..), MonoBinds(..),
+ InPat(..), andMonoBinds, getTyVarName
+ )
+import HsPragmas ( ClassPragmas(..) )
+import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..) )
+import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..),
+ RenamedClassOpSig(..), RenamedMonoBinds,
+ RenamedContext(..), RenamedHsDecl, RenamedSig
+ )
+import TcHsSyn ( TcMonoBinds )
-import AbsPrel ( pAT_ERROR_ID )
-import AbsUniType ( mkClass, getClassKey, getClassBigSig,
- getClassOpString, getClassOps, splitType,
- mkSuperDictSelType, InstTyEnv(..),
- instantiateTy, instantiateThetaTy, UniType
+import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, newDicts, newMethod )
+import TcEnv ( TcIdOcc(..), tcAddImportedIdInfo,
+ tcLookupClass, tcLookupTyVar,
+ tcExtendGlobalTyVars, tcExtendLocalValEnv
+ )
+import TcBinds ( tcBindWithSigs, checkSigTyVars, sigCtxt, tcPragmaSigs, TcSigInfo(..) )
+import TcKind ( unifyKinds, TcKind )
+import TcMonad
+import TcMonoType ( tcHsType, tcContext )
+import TcSimplify ( tcSimplifyAndCheck )
+import TcType ( TcType, TcTyVar, TcTyVarSet, tcInstSigTyVars,
+ zonkSigTyVar, tcInstSigTcType
)
-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 FieldLabel ( firstFieldLabelTag )
+import Bag ( unionManyBags )
+import Class ( mkClass, classBigSig, Class )
+import CmdLineOpts ( opt_GlasgowExts )
+import MkId ( mkDataCon, mkSuperDictSelId,
+ mkMethodSelId, mkDefaultMethodId
)
+import Id ( Id, StrictnessMark(..),
+ getIdUnfolding, idType, idName
+ )
+import CoreUnfold ( getUnfoldingTemplate )
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 Name ( Name, isLocallyDefined, OccName, nameOccName,
+ NamedThing(..) )
+import Outputable
+import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, splitRhoTy,
+ mkSigmaTy, mkForAllTys, Type, ThetaType
)
-import TcClassSig ( tcClassSigs )
-import TcContext ( tcContext )
-import TcInstDcls ( processInstBinds )
-import TcPragmas ( tcGenPragmas )
+import TyVar ( mkTyVarSet, tyVarKind, TyVar )
+import TyCon ( mkDataTyCon )
+import Kind ( mkBoxedTypeKind, mkArrowKind )
+import Unique ( Unique, Uniquable(..) )
import Util
+import Maybes ( assocMaybe, maybeToBool )
+
+
+-- import TcPragmas ( tcGenPragmas, tcClassOpPragmas )
+tcGenPragmas ty id ps = returnNF_Tc noIdInfo
+tcClassOpPragmas ty sel def spec ps = returnNF_Tc (spec `setSpecInfo` noIdInfo,
+ noIdInfo)
\end{code}
-@ClassInfo@ communicates the essential information about
-locally-defined classes between passes 1 and 2.
+
+
+Dictionary handling
+~~~~~~~~~~~~~~~~~~~
+Every class implicitly declares a new data type, corresponding to dictionaries
+of that class. So, for example:
+
+ class (D a) => C a where
+ op1 :: a -> a
+ op2 :: forall b. Ord b => a -> b -> b
+
+would implicitly declare
+
+ data CDict a = CDict (D a)
+ (a -> a)
+ (forall b. Ord b => a -> b -> b)
+
+(We could use a record decl, but that means changing more of the existing apparatus.
+One step at at time!)
+
+For classes with just one superclass+method, we use a newtype decl instead:
+
+ class C a where
+ op :: forallb. a -> b -> b
+
+generates
+
+ newtype CDict a = CDict (forall b. a -> b -> b)
+
+Now DictTy in Type is just a form of type synomym:
+ DictTy c t = TyConTy CDict `AppTy` t
+
+Death to "ExpandingDicts".
+
\begin{code}
-data ClassInfo
- = ClassInfo Class
- RenamedMonoBinds
+tcClassDecl1 rec_env rec_inst_mapper
+ (ClassDecl context class_name
+ 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_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
+ unifyKinds class_kinds tyvar_kinds `thenTc_`
+
+ -- CHECK THE CONTEXT
+ tcClassContext 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_tyvars) class_sigs
+ `thenTc` \ sig_stuff ->
+
+ -- MAKE THE CLASS OBJECT ITSELF
+ let
+ (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
+
+ dict_component_tys = sc_tys ++ op_tys
+ new_or_data = case dict_component_tys of
+ [_] -> NewType
+ other -> DataType
+
+ dict_con_id = mkDataCon datacon_name
+ [NotMarkedStrict | _ <- dict_component_tys]
+ [{- No labelled fields -}]
+ rec_tyvars
+ [{-No context-}]
+ [{-No existential tyvars-}] [{-Or context-}]
+ dict_component_tys
+ tycon
+
+ tycon = mkDataTyCon tycon_name
+ (foldr (mkArrowKind . tyVarKind) mkBoxedTypeKind rec_tyvars)
+ rec_tyvars
+ [] -- No context
+ [dict_con_id] -- Constructors
+ [] -- No derivings
+ (Just clas) -- Yes! It's a dictionary
+ new_or_data
+ NonRecursive
+ in
+ returnTc clas
\end{code}
-%************************************************************************
-%* *
-\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) ->
+tcClassContext :: Class -> [TyVar]
+ -> RenamedContext -- class context
+ -> RenamedClassPragmas -- pragmas for superclasses
+ -> TcM s (ThetaType, -- the superclass context
+ [Type], -- types of the superclass dictionaries
+ [Id]) -- superclass selector Ids
+
+tcClassContext 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` \ sc_theta ->
let
- glued_cinfos
- = case cinfo1_maybe of
- Nothing -> cinfo2
- Just xx -> xx : cinfo2
+ sc_tys = [mkDictTy sc tys | (sc,tys) <- sc_theta]
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)
+ -- Make super-class selector 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 ->
- = addSrcLocTc src_loc (
+ -- Done
+ returnTc (sc_theta, sc_tys, sc_sel_ids)
- -- 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
+ where
+ rec_tyvar_tys = mkTyVarTys rec_tyvars
+
+ mk_super_id ((super_class, tys), index)
+ = tcGetUnique `thenNF_Tc` \ uniq ->
let
- clas
- = mkClass class_name clas_tyvar
- super_classes super_class_sel_ids
- ops op_sel_ids defm_ids
- rec_clas_inst_env
+ ty = mkForAllTys rec_tyvars $
+ mkFunTy (mkDictTy rec_class rec_tyvar_tys) (mkDictTy super_class tys)
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)
--}
+ returnTc (mkSuperDictSelId uniq rec_class index ty)
+
+
+tcClassSig :: TcEnv s -- Knot tying only!
+ -> Class -- ...ditto...
+ -> [TyVar] -- The class type variable, used for error check only
+ -> RenamedClassOpSig
+ -> TcM s (Type, -- Type of the method
+ Id, -- selector id
+ Maybe Id) -- default-method ids
+
+tcClassSig rec_env rec_clas rec_clas_tyvars
+ (ClassOpSig op_name maybe_dm_name
+ op_ty
+ src_loc)
+ = tcAddSrcLoc src_loc $
+
+ -- Check the type signature. NB that the envt *already has*
+ -- bindings for the type variables; see comments in TcTyAndClassDcls.
+
+ -- NB: Renamer checks that the class type variable is mentioned in local_ty,
+ -- and that it is not constrained by theta
+ tcHsType op_ty `thenTc` \ local_ty ->
+ let
+ global_ty = mkSigmaTy rec_clas_tyvars
+ [(rec_clas, mkTyVarTys rec_clas_tyvars)]
+ local_ty
+ in
+
+ -- Build the selector id and default method id
+ let
+ sel_id = mkMethodSelId op_name rec_clas global_ty
+ maybe_dm_id = case maybe_dm_name of
+ Nothing -> Nothing
+ Just dm_name -> let
+ dm_id = mkDefaultMethodId dm_name rec_clas global_ty
+ in
+ Just (tcAddImportedIdInfo rec_env dm_id)
+ in
+ returnTc (local_ty, sel_id, maybe_dm_id)
\end{code}
(Omitted ones elicit an error message.)
\item
to produce a definition for the selector function for each method
+and superclass dictionary.
\end{enumerate}
Pass~2 only applies to locally-defined class declarations.
-The function @tcClassDecls2@ just arranges to apply
-@tcClassDecls2_help@ to each local class decl.
+The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to
+each local class decl.
\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
+tcClassDecls2 :: [RenamedHsDecl]
+ -> NF_TcM s (LIE s, TcMonoBinds s)
-tcClassDecls2_help
- :: E
- -> [TyVar]
- -> [ClassInfo]
- -> NF_TcM (LIE, TypecheckedBinds)
-
-tcClassDecls2_help e free_tyvars [] = returnNF_Tc (nullLIE, EmptyBinds)
-
-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)
+tcClassDecls2 decls
+ = foldr combine
+ (returnNF_Tc (emptyLIE, EmptyMonoBinds))
+ [tcClassDecl2 cls_decl | ClD cls_decl <- decls]
+ where
+ combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
+ tc2 `thenNF_Tc` \ (lie2, binds2) ->
+ returnNF_Tc (lie1 `plusLIE` lie2,
+ binds1 `AndMonoBinds` binds2)
\end{code}
@tcClassDecl2@ is the business end of things.
\begin{code}
-tcClassDecl2 :: 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}
+tcClassDecl2 :: RenamedClassDecl -- The class declaration
+ -> NF_TcM s (LIE s, TcMonoBinds s)
-%************************************************************************
-%* *
-\subsection[ClassDcl-bld-sels]{Building the selector functions for methods and superclasses}
-%* *
-%************************************************************************
+tcClassDecl2 (ClassDecl context class_name
+ tyvar_names class_sigs default_binds pragmas _ _ src_loc)
-\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}
-%* *
-%************************************************************************
-
-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}
+ | not (isLocallyDefined class_name)
+ = returnNF_Tc (emptyLIE, EmptyMonoBinds)
-{\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}
+ | otherwise -- It is locally defined
+ = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
+ tcAddSrcLoc src_loc $
-WDP 95/03: Quite false (``DICTIONARY APPLICATION IS CURRIED'').
-Specialisation now wants to see all type- and dictionary-applications
-absolutely explicitly.
+ -- Get the relevant class
+ tcLookupClass class_name `thenTc` \ (_, clas) ->
+ let
+ (tyvars, sc_theta, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
-\begin{code}
-mkSelExpr :: InstOrigin -> TyVar -> [Id] -> [Id] -> Id -> NF_TcM TypecheckedExpr
+ -- 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
+ ]
-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
+ final_sel_binds = andMonoBinds sel_binds
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))))
-\end{code}
+ -- Generate bindings for the default methods
+ tcDefaultMethodBinds clas default_binds `thenTc` \ (const_insts, meth_binds) ->
+ returnTc (const_insts,
+ final_sel_binds `AndMonoBinds` meth_binds)
+\end{code}
%************************************************************************
%* *
defm.Foo.op1 :: forall a. Foo a => a -> Bool
defm.Foo.op1 = /\a -> \dfoo -> \x -> True
+====================== OLD ==================
+\begin{verbatim}
defm.Foo.op2 :: forall a, b. (Foo a, Ord b) => a -> b -> b -> b
defm.Foo.op2 = /\ a b -> \ dfoo dord -> \x y z ->
if (op1 a dfoo x) && (< b dord y z) then y else z
\end{verbatim}
Notice that, like all ids, the foralls of defm.Foo.op2 are at the top.
+====================== END OF OLD ===================
+
+NEW:
+\begin{verbatim}
+defm.Foo.op2 :: forall a. Foo a => forall b. Ord b => a -> b -> b -> b
+defm.Foo.op2 = /\ a -> \ dfoo -> /\ b -> \ dord -> \x y z ->
+ if (op1 a dfoo x) && (< b dord y z) then y else z
+\end{verbatim}
+
When we come across an instance decl, we may need to use the default
methods:
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}
\begin{code}
-buildDefaultMethodBinds
- :: E
- -> [TyVar]
- -> InstOrigin
- -> Class
- -> TyVarTemplate
- -> [Id]
+tcDefaultMethodBinds
+ :: Class
-> 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'))
+ -> TcM s (LIE s, TcMonoBinds s)
+
+tcDefaultMethodBinds clas default_binds
+ = -- Construct suitable signatures
+ tcInstSigTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, inst_env) ->
+
+ -- Typecheck the default bindings
+ let
+ tc_dm meth_bind
+ = case [pair | pair@(sel_id,_) <- sel_ids_w_dms,
+ idName sel_id == bndr_name] of
+
+ [] -> -- Binding for something that isn't in the class signature
+ failWithTc (badMethodErr bndr_name clas)
+
+ ((sel_id, Just dm_id):_) ->
+ -- We're looking at a default-method binding, so the dm_id
+ -- is sure to be there! Hence the inner "Just".
+ -- Normal case
+
+ tcMethodBind clas origin inst_tys clas_tyvars
+ sel_id meth_bind [{- No prags -}]
+ `thenTc` \ (bind, insts, (_, local_dm_id)) ->
+ returnTc (bind, insts, (clas_tyvars, RealId dm_id, local_dm_id))
+ where
+ bndr_name = case meth_bind of
+ FunMonoBind name _ _ _ -> name
+ PatMonoBind (VarPatIn name) _ _ -> name
+
+ in
+ mapAndUnzip3Tc tc_dm
+ (flatten default_binds []) `thenTc` \ (defm_binds, insts_needed, abs_bind_stuff) ->
+
+ -- Check the context
+ newDicts origin [(clas,inst_tys)] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+ let
+ avail_insts = this_dict
+ in
+ tcAddErrCtxt (classDeclCtxt clas) $
+ mapNF_Tc zonkSigTyVar clas_tyvars `thenNF_Tc` \ clas_tyvars' ->
+ tcSimplifyAndCheck
+ (ptext SLIT("class") <+> ppr clas)
+ (mkTyVarSet clas_tyvars')
+ avail_insts
+ (unionManyBags insts_needed) `thenTc` \ (const_lie, dict_binds) ->
+
+ let
+ full_binds = AbsBinds
+ clas_tyvars'
+ [this_dict_id]
+ abs_bind_stuff
+ (dict_binds `AndMonoBinds` andMonoBinds defm_binds)
+ in
+ returnTc (const_lie, full_binds)
+
+ where
+ (tyvars, sc_theta, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
+ sel_ids_w_dms = op_sel_ids `zip` defm_ids
+ origin = ClassDeclOrigin
+
+ flatten EmptyMonoBinds rest = rest
+ flatten (AndMonoBinds b1 b2) rest = flatten b1 (flatten b2 rest)
+ flatten a_bind rest = a_bind : rest
\end{code}
-@makeClassDeclDefaultMethodRhs@ builds the default method for a
-class declaration when no explicit default method is given.
+@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
+tcMethodBind
:: 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))))))
- where
- method_id = method_ids !! (tag-1)
- class_op = (getClassOps clas) !! (tag-1)
+ -> InstOrigin s
+ -> [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
+ -> Id -- The method selector
+ -> RenamedMonoBinds -- Method binding (just one)
+ -> [RenamedSig] -- Pramgas (just for this one)
+ -> TcM s (TcMonoBinds s, LIE s, (LIE s, TcIdOcc s))
+
+tcMethodBind clas origin inst_tys inst_tyvars sel_id meth_bind prags
+ = tcAddSrcLoc src_loc $
+ newMethod origin (RealId sel_id) inst_tys `thenNF_Tc` \ meth@(_, TcId meth_id) ->
+ tcInstSigTcType (idType meth_id) `thenNF_Tc` \ (tyvars', rho_ty') ->
+ let
+ (theta', tau') = splitRhoTy rho_ty'
+ sig_info = TySigInfo meth_name meth_id tyvars' theta' tau' src_loc
+ meth_name = idName meth_id
+ meth_bind' = case meth_bind of
+ FunMonoBind _ fix matches loc -> FunMonoBind meth_name fix matches loc
+ PatMonoBind (VarPatIn _) rhs loc -> PatMonoBind (VarPatIn meth_name) rhs loc
+ -- 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.
+ in
+ tcExtendLocalValEnv [meth_name] [meth_id] (
+ tcPragmaSigs prags
+ ) `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
+
+ tcExtendGlobalTyVars inst_tyvars (
+ tcAddErrCtxt (methodCtxt sel_id) $
+ tcBindWithSigs NotTopLevel [meth_name] meth_bind' [sig_info]
+ NonRecursive prag_info_fn
+ ) `thenTc` \ (binds, insts, _) ->
+
+ -- 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
+ tcAddErrCtxt (monoCtxt sel_id) (
+ tcAddErrCtxt (sigCtxt sel_id) $
+ checkSigTyVars inst_tyvars (idType meth_id)
+ ) `thenTc_`
+
+ returnTc (binds `AndMonoBinds` prag_binds,
+ insts `plusLIE` prag_lie,
+ meth)
+ where
+ src_loc = case meth_bind of
+ FunMonoBind name _ _ loc -> loc
+ PatMonoBind (VarPatIn name) _ loc -> loc
+\end{code}
+
+Contexts and errors
+~~~~~~~~~~~~~~~~~~~
+\begin{code}
+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)
- error_msg = "%D" -- => No default method for \"
- ++ unencoded_part_of_msg
+methodCtxt sel_id
+ = ptext SLIT("In the definition for method") <+> quotes (ppr sel_id)
- unencoded_part_of_msg = escErrorMsg (
- _UNPK_ clas_mod ++ "." ++ _UNPK_ clas_name ++ "."
- ++ (ppShow 80 (ppr PprForUser class_op))
- ++ "\"" )
+monoCtxt sel_id
+ = sep [ptext SLIT("Probable cause: the right hand side of") <+> quotes (ppr sel_id),
+ nest 4 (ptext SLIT("mentions a top-level variable subject to the dreaded monomorphism restriction"))
+ ]
- (clas_mod, clas_name) = getOrigName clas
+badMethodErr bndr clas
+ = hsep [ptext SLIT("Class"), quotes (ppr clas),
+ ptext SLIT("does not have a method"), quotes (ppr bndr)]
\end{code}
projects / ghc-hetmet.git / blobdiff