\begin{code}
#include "HsVersions.h"
-module TcClassDcl (
- tcClassDecls1, tcClassDecls2,
- ClassInfo -- abstract
- ) 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
-
-import AbsPrel ( pAT_ERROR_ID )
-import AbsUniType ( mkClass, getClassKey, getClassBigSig,
- getClassOpString, getClassOps, splitType,
- mkSuperDictSelType, InstTyEnv(..),
- instantiateTy, instantiateThetaTy, UniType
+module TcClassDcl ( tcClassDecl1, tcClassDecls2 ) where
+
+IMP_Ubiq()
+
+import HsSyn ( ClassDecl(..), HsBinds(..), Bind(..), MonoBinds(..),
+ Match(..), GRHSsAndBinds(..), GRHS(..), HsExpr(..),
+ HsLit(..), OutPat(..), Sig(..), PolyType(..), MonoType,
+ Stmt, Qualifier, ArithSeqInfo, InPat, Fake )
+import HsPragmas ( ClassPragmas(..) )
+import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..),
+ RenamedClassOpSig(..), SYN_IE(RenamedMonoBinds),
+ RenamedGenPragmas(..), RenamedContext(..),
+ RnName{-instance Uniquable-}
)
-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 TcHsSyn ( TcIdOcc(..), SYN_IE(TcHsBinds), SYN_IE(TcMonoBinds), SYN_IE(TcExpr),
+ mkHsTyApp, mkHsTyLam, mkHsDictApp, mkHsDictLam, tcIdType )
+
+import Inst ( Inst, InstOrigin(..), SYN_IE(LIE), emptyLIE, plusLIE, newDicts, newMethod )
+import TcEnv ( tcLookupClass, tcLookupTyVar, tcLookupTyCon, newLocalIds, tcExtendGlobalTyVars )
+import TcInstDcls ( processInstBinds )
+import TcKind ( unifyKind, TcKind )
+import TcMonad hiding ( rnMtoTcM )
+import TcMonoType ( tcPolyType, tcMonoType, tcContext )
+import TcSimplify ( tcSimplifyAndCheck )
+import TcType ( SYN_IE(TcType), SYN_IE(TcTyVar), tcInstType, tcInstSigTyVars, tcInstSigType )
+
+import Bag ( foldBag, unionManyBags )
+import Class ( GenClass, mkClass, mkClassOp, classBigSig,
+ classOps, classOpString, classOpLocalType,
+ classOpTagByString, SYN_IE(ClassOp)
)
+import Id ( mkSuperDictSelId, mkMethodSelId, mkDefaultMethodId,
+ idType )
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 TcClassSig ( tcClassSigs )
-import TcContext ( tcContext )
-import TcInstDcls ( processInstBinds )
-import TcPragmas ( tcGenPragmas )
+import Name ( isLocallyDefined, origName, getLocalName )
+import PrelVals ( nO_DEFAULT_METHOD_ERROR_ID )
+import PprStyle
+import Pretty
+import PprType ( GenType, GenTyVar, GenClassOp )
+import SpecEnv ( SpecEnv )
+import SrcLoc ( mkGeneratedSrcLoc )
+import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy,
+ mkForAllTy, mkSigmaTy, splitSigmaTy)
+import TysWiredIn ( stringTy )
+import TyVar ( unitTyVarSet, GenTyVar )
+import Unique ( Unique )
import Util
+
+
+-- import TcPragmas ( tcGenPragmas, tcClassOpPragmas )
+tcGenPragmas ty id ps = returnNF_Tc noIdInfo
+tcClassOpPragmas ty sel def spec ps = returnNF_Tc (noIdInfo `addInfo` spec,
+ 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_inst_mapper
+ (ClassDecl context class_name
+ tyvar_name class_sigs def_methods pragmas src_loc)
+ = tcAddSrcLoc src_loc $
+ tcAddErrCtxt (classDeclCtxt class_name) $
+
+ -- LOOK THINGS UP IN THE ENVIRONMENT
+ tcLookupClass class_name `thenNF_Tc` \ (class_kind, rec_class) ->
+ tcLookupTyVar tyvar_name `thenNF_Tc` \ (tyvar_kind, rec_tyvar) ->
+ let
+ (rec_class_inst_env, rec_class_op_inst_fn) = rec_inst_mapper rec_class
+ in
+
+ -- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND
+ unifyKind class_kind tyvar_kind `thenTc_`
+
+ -- CHECK THE CONTEXT
+ tcClassContext rec_class rec_tyvar context pragmas
+ `thenTc` \ (scs, sc_sel_ids) ->
+
+ -- CHECK THE CLASS SIGNATURES,
+ mapTc (tcClassSig rec_class rec_tyvar rec_class_op_inst_fn) class_sigs
+ `thenTc` \ sig_stuff ->
+
+ -- MAKE THE CLASS OBJECT ITSELF
+ let
+ (ops, op_sel_ids, defm_ids) = unzip3 sig_stuff
+ clas = mkClass (uniqueOf class_name) (getName class_name) rec_tyvar
+ scs sc_sel_ids ops op_sel_ids defm_ids
+ rec_class_inst_env
+ in
+ returnTc clas
\end{code}
-%************************************************************************
-%* *
-\subsection[TcClassDcl]{Does the real work (apart from default methods)}
-%* *
-%************************************************************************
+ let
+ clas_ty = mkTyVarTy clas_tyvar
+ dict_component_tys = [mkDictTy sc clas_ty | sc <- scs] ++
+ [classOpLocalType op | op <- ops])
+ new_or_data = case dict_component_tys of
+ [_] -> NewType
+ other -> DataType
+
+ dict_con_id = mkDataCon class_name
+ [NotMarkedStrict]
+ [{- No labelled fields -}]
+ [clas_tyvar]
+ [{-No context-}]
+ dict_component_tys
+ tycon
+
+ tycon = mkDataTyCon class_name
+ (tyVarKind rec_tyvar `mkArrowKind` mkBoxedTypeKind)
+ [rec_tyvar]
+ [{- Empty context -}]
+ [dict_con_id]
+ [{- No derived classes -}]
+ new_or_data
+ in
+
\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 ([Class], -- the superclasses
+ [Id]) -- superclass selector Ids
+
+tcClassContext rec_class rec_tyvar context pragmas
+ = -- Check the context.
+ -- The renamer has already checked that the context mentions
+ -- only the type variable of the class decl.
+ tcContext context `thenTc` \ theta ->
let
- glued_cinfos
- = case cinfo1_maybe of
- Nothing -> cinfo2
- Just xx -> xx : cinfo2
+ super_classes = [ supers | (supers, _) <- theta ]
in
- returnTc (glued_cinfos, ce1 `plusCE` ce2, gve1 `plusGVE` gve2)
+
+ -- Make super-class selector ids
+ mapTc (mk_super_id rec_class)
+ (super_classes `zip` maybe_pragmas) `thenTc` \ sc_sel_ids ->
+ -- NB: we worry about matching list lengths below
+
+ -- Done
+ returnTc (super_classes, sc_sel_ids)
+
where
- rec_ce = getE_CE e
- rec_tce = getE_TCE e
+ mk_super_id rec_class (super_class, maybe_pragma)
+ = fixTc ( \ rec_super_id ->
+ tcGetUnique `thenNF_Tc` \ uniq ->
+
+ -- GET THE PRAGMA INFO FOR THE SUPERCLASS
+ (case maybe_pragma of
+ Nothing -> returnNF_Tc noIdInfo
+ Just prag -> tcGenPragmas Nothing{-ty unknown-} rec_super_id prag
+ ) `thenNF_Tc` \ id_info ->
+ let
+ rec_tyvar_ty = mkTyVarTy rec_tyvar
+ ty = mkForAllTy rec_tyvar $
+ mkFunTy (mkDictTy rec_class rec_tyvar_ty)
+ (mkDictTy super_class rec_tyvar_ty)
+ in
+ -- BUILD THE SUPERCLASS ID
+ returnTc (mkSuperDictSelId uniq rec_class super_class ty id_info)
+ )
+
+ maybe_pragmas :: [Maybe RenamedGenPragmas]
+ maybe_pragmas = case pragmas of
+ NoClassPragmas -> repeat Nothing
+ SuperDictPragmas prags -> ASSERT(length prags == length context)
+ map Just prags
+ -- If there are any pragmas there should
+ -- be one for each superclass
+
+
+
+tcClassSig :: Class -- Knot tying only!
+ -> TyVar -- The class type variable, used for error check only
+ -> (ClassOp -> SpecEnv) -- Ditto; the spec info for the class ops
+ -> RenamedClassOpSig
+ -> TcM s (ClassOp, -- class op
+ Id, -- selector id
+ Id) -- default-method ids
+
+tcClassSig rec_clas rec_clas_tyvar rec_classop_spec_fn
+ (ClassOpSig op_name
+ op_ty
+ pragmas src_loc)
+ = tcAddSrcLoc src_loc $
+ fixTc ( \ ~(_, rec_sel_id, rec_defm_id) -> -- Knot for pragmas
+
+ -- Check the type signature. NB that the envt *already has*
+ -- bindings for the type variables; see comments in TcTyAndClassDcls.
+
+ -- NB: Renamer checks that the class type variable is mentioned in local_ty,
+ -- and that it is not constrained by theta
+ tcPolyType op_ty `thenTc` \ local_ty ->
+ let
+ global_ty = mkSigmaTy [rec_clas_tyvar]
+ [(rec_clas, mkTyVarTy rec_clas_tyvar)]
+ local_ty
+ class_op_nm = getLocalName op_name
+ class_op = mkClassOp class_op_nm
+ (classOpTagByString rec_clas{-yeeps!-} class_op_nm)
+ local_ty
+ in
- tc_clas1 (ClassDecl context class_name
- tyvar_name class_sigs def_methods pragmas src_loc)
+ -- Munch the pragmas
+ tcClassOpPragmas
+ global_ty
+ rec_sel_id rec_defm_id
+ (rec_classop_spec_fn class_op)
+ pragmas `thenNF_Tc` \ (op_info, defm_info) ->
- = 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)
--}
+ -- Build the selector id and default method id
+ tcGetUnique `thenNF_Tc` \ d_uniq ->
+ let
+ op_uniq = uniqueOf op_name
+ sel_id = mkMethodSelId op_uniq rec_clas class_op global_ty op_info
+ defm_id = mkDefaultMethodId d_uniq rec_clas class_op False global_ty defm_info
+ -- ToDo: improve the "False"
+ in
+ returnTc (class_op, sel_id, defm_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_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 :: Bag RenamedClassDecl
+ -> NF_TcM s (LIE s, TcHsBinds s)
+
+tcClassDecls2 decls
+ = foldBag combine
+ tcClassDecl2
+ (returnNF_Tc (emptyLIE, EmptyBinds))
+ decls
+ where
+ combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
+ tc2 `thenNF_Tc` \ (lie2, binds2) ->
+ returnNF_Tc (lie1 `plusLIE` lie2,
+ binds1 `ThenBinds` binds2)
\end{code}
@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
+tcClassDecl2 :: RenamedClassDecl -- The class declaration
+ -> NF_TcM s (LIE s, TcHsBinds s)
+
+tcClassDecl2 (ClassDecl context class_name
+ tyvar_name class_sigs default_binds pragmas src_loc)
+
+ | not (isLocallyDefined class_name)
+ = returnNF_Tc (emptyLIE, EmptyBinds)
+
+ | otherwise -- It is locally defined
+ = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $
+ tcAddSrcLoc src_loc $
+
+ -- Get the relevant class
+ tcLookupClass class_name `thenNF_Tc` \ (_, clas) ->
+ let
+ (tyvar, scs, sc_sel_ids, ops, op_sel_ids, defm_ids)
+ = classBigSig 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)
- )))
+ tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], _, _) ->
+
+ -- Generate bindings for the selector functions
+ buildSelectors clas tyvar clas_tyvar scs sc_sel_ids ops op_sel_ids
+ `thenNF_Tc` \ sel_binds ->
+ -- Ditto for the methods
+ buildDefaultMethodBinds clas clas_tyvar defm_ids default_binds
+ `thenTc` \ (const_insts, meth_binds) ->
+
+ returnTc (const_insts, sel_binds `ThenBinds` meth_binds)
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-buildSelectors :: InstOrigin
- -> Class -- The class object
- -> TyVarTemplate -- Class type variable
+buildSelectors :: Class -- The class object
+ -> TyVar -- Class type variable
+ -> TcTyVar s -- Instantiated class type variable (TyVarTy)
-> [Class] -> [Id] -- Superclasses and selectors
-> [ClassOp] -> [Id] -- Class ops and selectors
- -> NF_TcM TypecheckedBinds
+ -> NF_TcM s (TcHsBinds s)
-buildSelectors origin clas clas_tyvar_tmpl
- scs sc_sel_ids
- ops op_sel_ids
+buildSelectors clas clas_tyvar clas_tc_tyvar 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 new Ids for the components of the dictionary
+ let
+ clas_tyvar_ty = mkTyVarTy clas_tc_tyvar
+ mk_op_ty = tcInstType [(clas_tyvar, clas_tyvar_ty)] . classOpLocalType
+ in
+ mapNF_Tc mk_op_ty ops `thenNF_Tc` \ op_tys ->
+ newLocalIds (map classOpString ops) op_tys `thenNF_Tc` \ method_ids ->
+
+ newDicts ClassDeclOrigin
+ [ (super_clas, clas_tyvar_ty)
+ | super_clas <- scs ] `thenNF_Tc` \ (_,dict_ids) ->
+
+ newDicts ClassDeclOrigin
+ [ (clas, clas_tyvar_ty) ] `thenNF_Tc` \ (_,[clas_dict]) ->
-- 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)
+ let
+ mk_sel sel_id method_or_dict
+ = mkSelBind sel_id clas_tc_tyvar clas_dict dict_ids method_ids method_or_dict
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 ->
+ listNF_Tc (zipWithEqual "mk_sel1" mk_sel op_sel_ids method_ids) `thenNF_Tc` \ op_sel_binds ->
+ listNF_Tc (zipWithEqual "mk_sel2" mk_sel sc_sel_ids dict_ids) `thenNF_Tc` \ sc_sel_binds ->
returnNF_Tc (SingleBind (
NonRecBind (
- foldr AndMonoBinds EmptyMonoBinds (
- op_sel_binds ++ sc_sel_binds))))
+ foldr AndMonoBinds
+ (foldr AndMonoBinds EmptyMonoBinds op_sel_binds)
+ sc_sel_binds
+ )))
\end{code}
%************************************************************************
%* *
%************************************************************************
-Make a selector expression for @local@ from a dictionary consisting of
-@dicts@ and @op_locals@.
+Make a selector expression for @sel_id@ from a dictionary @clas_dict@
+consisting of @dicts@ and @methods@.
+====================== OLD ============================
We have to do a bit of jiggery pokery to get the type variables right.
Suppose we have the class decl:
\begin{verbatim}
\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
+ op1_sel = /\a b -> \dFoo dOrd -> case dFoo of
+ (op1_method,op2_method) -> op1_method b dOrd
\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:
+Note that the type variable for \tr{b} and the (Ord b) dictionary
+are lifted to the top lambda, and
+\tr{op1_method} is applied to them. This is preferable to the alternative:
\begin{verbatim}
op1_sel' = /\a -> \dFoo -> case dFoo of
(op1_method,op2_method) -> op1_method
\begin{verbatim}
op1_sel :: forall a b. Foo a -> Ord b -> a -> b -> a
\end{verbatim}
+========================= END OF OLD ===========================
-{\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}
+NEW COMMENT: instead we now go for op1_sel' above. Seems tidier and
+the rest of the compiler darn well ought to cope.
-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
-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))))
+NOTE that we return a TcMonoBinds (which is later zonked) even though
+there's no real back-substitution to do. It's just simpler this way!
+
+NOTE ALSO that the selector has no free type variables, so we
+don't bother to instantiate the class-op's local type; instead
+we just use the variables inside it.
+
+\begin{code}
+mkSelBind :: Id -- the selector id
+ -> TcTyVar s -> TcIdOcc s -- class tyvar and dict
+ -> [TcIdOcc s] -> [TcIdOcc s] -- superclasses and methods in class dict
+ -> TcIdOcc s -- the superclass/method being slected
+ -> NF_TcM s (TcMonoBinds s)
+
+mkSelBind sel_id clas_tyvar clas_dict dicts methods method_or_dict@(TcId op)
+ =
+ -- sel_id = /\ clas_tyvar -> \ clas_dict ->
+ -- case clas_dict of
+ -- <dicts..methods> -> method_or_dict
+
+ returnNF_Tc (VarMonoBind (RealId sel_id) (
+ TyLam [clas_tyvar] (
+ DictLam [clas_dict] (
+ HsCase
+ (HsVar clas_dict)
+ ([PatMatch (DictPat dicts methods) (
+ GRHSMatch (GRHSsAndBindsOut
+ [OtherwiseGRHS
+ (HsVar method_or_dict)
+ mkGeneratedSrcLoc]
+ EmptyBinds
+ (idType op)))])
+ mkGeneratedSrcLoc
+ ))))
\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
\begin{code}
buildDefaultMethodBinds
- :: E
- -> [TyVar]
- -> InstOrigin
- -> Class
- -> TyVarTemplate
+ :: Class
+ -> TcTyVar s
-> [Id]
-> RenamedMonoBinds
- -> TcM ([Inst], TypecheckedBinds)
+ -> TcM s (LIE s, TcHsBinds s)
-buildDefaultMethodBinds e free_tyvars origin clas clas_tyvar_tmpl
+buildDefaultMethodBinds clas clas_tyvar
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'))
+ = newDicts origin [(clas,inst_ty)] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+ mapAndUnzipNF_Tc mk_method default_method_ids `thenNF_Tc` \ (insts_s, local_defm_ids) ->
+ let
+ avail_insts = this_dict `plusLIE` unionManyBags insts_s -- Insts available
+ clas_tyvar_set = unitTyVarSet clas_tyvar
+ in
+ tcExtendGlobalTyVars clas_tyvar_set (
+ processInstBinds
+ clas
+ (makeClassDeclDefaultMethodRhs clas local_defm_ids)
+ avail_insts
+ local_defm_ids
+ default_binds
+ ) `thenTc` \ (insts_needed, default_binds') ->
+
+ tcSimplifyAndCheck
+ clas_tyvar_set
+ avail_insts
+ insts_needed `thenTc` \ (const_lie, dict_binds) ->
+
+
+ let
+ defm_binds = AbsBinds
+ [clas_tyvar]
+ [this_dict_id]
+ (local_defm_ids `zip` map RealId default_method_ids)
+ dict_binds
+ (RecBind default_binds')
+ in
+ returnTc (const_lie, defm_binds)
+ where
+ inst_ty = mkTyVarTy clas_tyvar
+ mk_method defm_id = newMethod origin (RealId defm_id) [inst_ty]
+ origin = ClassDeclOrigin
\end{code}
@makeClassDeclDefaultMethodRhs@ builds the default method for a
\begin{code}
makeClassDeclDefaultMethodRhs
:: Class
- -> InstOrigin
- -> [Id]
+ -> [TcIdOcc s]
-> Int
- -> NF_TcM TypecheckedExpr
-
-makeClassDeclDefaultMethodRhs clas origin method_ids tag
- = specTy origin (getIdUniType method_id) `thenNF_Tc` \ (tyvars, dicts, tau) ->
+ -> NF_TcM s (TcExpr s)
+
+makeClassDeclDefaultMethodRhs clas method_ids tag
+ = -- Return the expression
+ -- error ty "No default method for ..."
+ -- The interesting thing is that method_ty is a for-all type;
+ -- this is fun, although unusual in a type application!
+
+ returnNF_Tc (HsApp (mkHsTyApp (HsVar (RealId nO_DEFAULT_METHOD_ERROR_ID)) [tcIdType method_id])
+ (HsLitOut (HsString (_PK_ error_msg)) stringTy))
+
+{- OLD AND COMPLICATED
+ tcInstSigType () `thenNF_Tc` \ method_ty ->
+ let
+ (tyvars, theta, tau) = splitSigmaTy method_ty
+ in
+ newDicts ClassDeclOrigin theta `thenNF_Tc` \ (lie, dict_ids) ->
+
+ returnNF_Tc (mkHsTyLam tyvars (
+ mkHsDictLam dict_ids (
+ HsApp (mkHsTyApp (HsVar (RealId nO_DEFAULT_METHOD_ERROR_ID)) [tau])
+ (HsLitOut (HsString (_PK_ error_msg)) stringTy))))
+-}
- returnNF_Tc (mkTyLam tyvars (
- mkDictLam (map mkInstId dicts) (
- App (mkTyApp (Var pAT_ERROR_ID) [tau])
- (Lit (StringLit (_PK_ error_msg))))))
where
+ (OrigName clas_mod clas_name) = origName "makeClassDeclDefaultMethodRhs" clas
+
method_id = method_ids !! (tag-1)
- class_op = (getClassOps clas) !! (tag-1)
+ class_op = (classOps clas) !! (tag-1)
- error_msg = "%D" -- => No default method for \"
- ++ unencoded_part_of_msg
+ error_msg = _UNPK_ clas_mod ++ "." ++ _UNPK_ clas_name ++ "."
+ ++ (ppShow 80 (ppr PprForUser class_op))
+ ++ "\""
+\end{code}
- unencoded_part_of_msg = escErrorMsg (
- _UNPK_ clas_mod ++ "." ++ _UNPK_ clas_name ++ "."
- ++ (ppShow 80 (ppr PprForUser class_op))
- ++ "\"" )
- (clas_mod, clas_name) = getOrigName clas
+Contexts
+~~~~~~~~
+\begin{code}
+classDeclCtxt class_name sty
+ = ppCat [ppStr "In the class declaration for", ppr sty class_name]
\end{code}
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