%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcClassDcl]{Typechecking class declarations}
\begin{code}
-#include "HsVersions.h"
-
-module TcClassDcl (
- tcClassDecl1, tcClassDecls2
- ) where
+module TcClassDcl ( tcClassDecl1, tcClassDecls2, tcMethodBind, badMethodErr ) where
-import Ubiq
+#include "HsVersions.h"
-import HsSyn ( ClassDecl(..), HsBinds(..), Bind(..), MonoBinds(..),
- Match(..), GRHSsAndBinds(..), GRHS(..), HsExpr(..),
- HsLit(..), OutPat(..), Sig(..), PolyType(..), MonoType,
- Stmt, Qual, ArithSeqInfo, InPat, Fake )
+import HsSyn ( HsDecl(..), ClassDecl(..), Sig(..), MonoBinds(..),
+ InPat(..), HsBinds(..), GRHSsAndBinds(..),
+ HsExpr(..), HsLit(..), HsType(..), pprClassAssertion,
+ unguardedRHS, andMonoBinds, andMonoBindList, getTyVarName
+ )
import HsPragmas ( ClassPragmas(..) )
-import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..),
- RenamedClassOpSig(..), RenamedMonoBinds(..),
- RenamedGenPragmas(..), RenamedContext(..),
- RnName{-instance Uniquable-}
+import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..), StrictnessMark(..) )
+import RnHsSyn ( RenamedClassDecl, RenamedClassPragmas,
+ RenamedClassOpSig, RenamedMonoBinds,
+ RenamedContext, RenamedHsDecl, RenamedSig
)
-import TcHsSyn ( TcIdOcc(..), TcHsBinds(..), TcMonoBinds(..), TcExpr(..),
- mkHsTyApp, mkHsTyLam, mkHsDictApp, mkHsDictLam, unZonkId )
+import TcHsSyn ( TcMonoBinds )
+import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, newDicts, newMethod )
+import TcEnv ( TcIdOcc(..), GlobalValueEnv, tcAddImportedIdInfo,
+ tcLookupClass, tcLookupTyVar,
+ tcExtendGlobalTyVars, tcExtendLocalValEnv
+ )
+import TcBinds ( tcBindWithSigs, tcPragmaSigs )
+import TcUnify ( unifyKinds )
import TcMonad
-import Inst ( Inst, InstOrigin(..), LIE(..), emptyLIE, plusLIE, newDicts )
-import TcEnv ( tcLookupClass, tcLookupTyVar, tcLookupTyCon, newLocalIds)
-import TcInstDcls ( processInstBinds )
-import TcKind ( unifyKind )
-import TcMonoType ( tcMonoType, tcContext )
-import TcType ( TcType(..), TcTyVar(..), tcInstType, tcInstSigTyVars )
-import TcKind ( TcKind )
-
-import Bag ( foldBag )
-import Class ( GenClass, mkClass, mkClassOp, classBigSig,
- classOps, classOpString, classOpLocalType,
- classOpTagByString
+import TcMonoType ( tcHsType, tcContext, checkSigTyVars, sigCtxt, mkTcSig )
+import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
+import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcTyVarBndr )
+import PrelVals ( nO_METHOD_BINDING_ERROR_ID )
+import FieldLabel ( firstFieldLabelTag )
+import Bag ( unionManyBags )
+import Class ( mkClass, classBigSig, Class )
+import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods )
+import MkId ( mkSuperDictSelId, mkDataConId,
+ mkMethodSelId, mkDefaultMethodId
+ )
+import DataCon ( mkDataCon )
+import Id ( Id,
+ getIdUnfolding, idType, idName
)
-import Id ( mkSuperDictSelId, mkMethodSelId, mkDefaultMethodId,
- idType )
-import IdInfo ( noIdInfo )
-import Name ( isLocallyDefined, moduleNamePair, getLocalName )
-import PrelVals ( nO_DEFAULT_METHOD_ERROR_ID )
-import PprStyle
-import Pretty
-import PprType ( GenType, GenTyVar, GenClassOp )
-import SpecEnv ( SpecEnv(..) )
-import SrcLoc ( mkGeneratedSrcLoc )
+import CoreUnfold ( getUnfoldingTemplate )
+import IdInfo
+import Name ( Name, isLocallyDefined, NamedThing(..) )
+import Outputable
import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy,
- mkForAllTy, mkSigmaTy, splitSigmaTy)
-import TysWiredIn ( stringTy )
-import TyVar ( GenTyVar )
-import Unique ( Unique )
+ mkSigmaTy, mkForAllTys, Type, ThetaType,
+ boxedTypeKind, mkArrowKind
+ )
+import Var ( tyVarKind, TyVar )
+import VarSet ( mkVarSet )
+import TyCon ( mkAlgTyCon )
+import Unique ( Unique, Uniquable(..) )
import Util
+import Maybes ( seqMaybe )
+
-- import TcPragmas ( tcGenPragmas, tcClassOpPragmas )
tcGenPragmas ty id ps = returnNF_Tc noIdInfo
-tcClassOpPragmas ty sel def spec ps = returnNF_Tc (noIdInfo, noIdInfo)
-
+tcClassOpPragmas ty sel def spec ps = returnNF_Tc (spec `setSpecInfo` noIdInfo,
+ noIdInfo)
\end{code}
+
+
+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}
-tcClassDecl1 rec_inst_mapper
+tcClassDecl1 rec_env rec_inst_mapper
(ClassDecl context class_name
- tyvar_name class_sigs def_methods pragmas src_loc)
+ tyvar_names class_sigs def_methods pragmas
+ tycon_name datacon_name src_loc)
= tcAddSrcLoc src_loc $
tcAddErrCtxt (classDeclCtxt class_name) $
+ -- CHECK ARITY 1 FOR HASKELL 1.4
+ checkTc (opt_GlasgowExts || length tyvar_names == 1)
+ (classArityErr class_name) `thenTc_`
+
-- LOOK THINGS UP IN THE ENVIRONMENT
- tcLookupClass class_name `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
+ tcLookupClass class_name `thenTc` \ (class_kinds, rec_class) ->
+ mapAndUnzipNF_Tc (tcLookupTyVar . getTyVarName) tyvar_names
+ `thenNF_Tc` \ (tyvar_kinds, rec_tyvars) ->
-- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND
- unifyKind class_kind tyvar_kind `thenTc_`
+ unifyKinds class_kinds tyvar_kinds `thenTc_`
-- CHECK THE CONTEXT
- tcClassContext rec_class rec_tyvar context pragmas
- `thenTc` \ (scs, sc_sel_ids) ->
+ tcClassContext class_name rec_class rec_tyvars context pragmas
+ `thenTc` \ (sc_theta, sc_tys, sc_sel_ids) ->
-- CHECK THE CLASS SIGNATURES,
- mapTc (tcClassSig rec_class rec_tyvar rec_class_op_inst_fn) class_sigs
- `thenTc` \ sig_stuff ->
+ mapTc (tcClassSig rec_env rec_class rec_tyvars) class_sigs
+ `thenTc` \ sig_stuff ->
-- MAKE THE CLASS OBJECT ITSELF
--- BOGUS:
--- tcGetUnique `thenNF_Tc` \ uniq ->
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
+ (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 = mkDataCon datacon_name
+ [NotMarkedStrict | _ <- dict_component_tys]
+ [{- No labelled fields -}]
+ rec_tyvars
+ [{-No context-}]
+ [{-No existential tyvars-}] [{-Or context-}]
+ dict_component_tys
+ tycon dict_con_id
+ dict_con_id = mkDataConId dict_con
+
+ tycon = mkAlgTyCon tycon_name
+ (foldr (mkArrowKind . tyVarKind) boxedTypeKind rec_tyvars)
+ rec_tyvars
+ [] -- No context
+ [dict_con] -- Constructors
+ [] -- No derivings
+ (Just clas) -- Yes! It's a dictionary
+ new_or_data
+ NonRecursive
in
returnTc clas
\end{code}
\begin{code}
-tcClassContext :: Class -> TyVar
+tcClassContext :: Name -> Class -> [TyVar]
-> RenamedContext -- class context
-> RenamedClassPragmas -- pragmas for superclasses
- -> TcM s ([Class], -- the superclasses
- [Id]) -- superclass selector Ids
+ -> TcM s (ThetaType, -- the superclass context
+ [Type], -- types of the superclass dictionaries
+ [Id]) -- superclass selector Ids
-tcClassContext rec_class rec_tyvar context pragmas
+tcClassContext class_name rec_class rec_tyvars context pragmas
= -- Check the context.
-- The renamer has already checked that the context mentions
-- only the type variable of the class decl.
- tcContext context `thenTc` \ theta ->
+
+ -- For std Haskell check that the context constrains only tyvars
+ (if opt_GlasgowExts then
+ returnTc []
+ else
+ mapTc check_constraint context
+ ) `thenTc_`
+
+ tcContext context `thenTc` \ sc_theta ->
+
let
- super_classes = [ supers | (supers, _) <- theta ]
+ sc_tys = [mkDictTy sc tys | (sc,tys) <- sc_theta]
in
-- Make super-class selector ids
- mapTc (mk_super_id rec_class)
- (super_classes `zip` maybe_pragmas) `thenTc` \ sc_sel_ids ->
+ -- We number them off, 1, 2, 3 etc so that we can construct
+ -- names for the selectors. Thus
+ -- class (C a, C b) => D a b where ...
+ -- gives superclass selectors
+ -- D_sc1, D_sc2
+ -- (We used to call them D_C, but now we can have two different
+ -- superclasses both called C!)
+ mapTc mk_super_id (sc_theta `zip` [firstFieldLabelTag..]) `thenTc` \ sc_sel_ids ->
-- Done
- returnTc (super_classes, sc_sel_ids)
+ returnTc (sc_theta, sc_tys, sc_sel_ids)
where
- 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
- ty = mkForAllTy rec_tyvar (
- mkFunTy (mkDictTy rec_class (mkTyVarTy rec_tyvar))
- (mkDictTy super_class (mkTyVarTy rec_tyvar))
- )
- 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
+ rec_tyvar_tys = mkTyVarTys rec_tyvars
+
+ mk_super_id ((super_class, tys), index)
+ = tcGetUnique `thenNF_Tc` \ uniq ->
+ let
+ ty = mkForAllTys rec_tyvars $
+ mkFunTy (mkDictTy rec_class rec_tyvar_tys) (mkDictTy super_class tys)
+ in
+ returnTc (mkSuperDictSelId uniq rec_class index ty)
+
+ check_constraint (c, tys) = checkTc (all is_tyvar tys)
+ (superClassErr class_name (c, tys))
+
+ is_tyvar (MonoTyVar _) = True
+ is_tyvar other = False
+
+
+tcClassSig :: GlobalValueEnv -- Knot tying only!
+ -> Class -- ...ditto...
+ -> [TyVar] -- The class type variable, used for error check only
-> RenamedClassOpSig
- -> TcM s (ClassOp, -- class op
+ -> TcM s (Type, -- Type of the method
Id, -- selector id
- Id) -- default-method ids
+ Maybe Id) -- default-method ids
-tcClassSig rec_clas rec_clas_tyvar rec_classop_spec_fn
- (ClassOpSig op_name
- (HsForAllTy tyvar_names context monotype)
- pragmas src_loc)
+tcClassSig rec_env rec_clas rec_clas_tyvars
+ (ClassOpSig op_name maybe_dm_name
+ op_ty
+ 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.
- tcContext context `thenTc` \ theta ->
- tcMonoType monotype `thenTc` \ tau ->
- mapAndUnzipNF_Tc tcLookupTyVar tyvar_names `thenNF_Tc` \ (_,tyvars) ->
+
+ -- 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
- full_tyvars = rec_clas_tyvar : tyvars
- full_theta = (rec_clas, mkTyVarTy rec_clas_tyvar) : theta
- global_ty = mkSigmaTy full_tyvars full_theta tau
- local_ty = mkSigmaTy tyvars theta tau
- class_op_nm = getLocalName op_name
- class_op = mkClassOp class_op_nm
- (classOpTagByString rec_clas{-yeeps!-} class_op_nm)
- local_ty
+ global_ty = mkSigmaTy rec_clas_tyvars
+ [(rec_clas, mkTyVarTys rec_clas_tyvars)]
+ local_ty
in
- -- 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) ->
-
-- 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"
+ 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 (class_op, sel_id, defm_id)
- )
+ returnTc (local_ty, sel_id, maybe_dm_id)
\end{code}
each local class decl.
\begin{code}
-tcClassDecls2 :: Bag RenamedClassDecl
- -> NF_TcM s (LIE s, TcHsBinds s)
+tcClassDecls2 :: [RenamedHsDecl]
+ -> NF_TcM s (LIE s, TcMonoBinds s)
tcClassDecls2 decls
- = foldBag combine
- tcClassDecl2
- (returnNF_Tc (emptyLIE, EmptyBinds))
- 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 `ThenBinds` binds2)
+ binds1 `AndMonoBinds` binds2)
\end{code}
@tcClassDecl2@ is the business end of things.
\begin{code}
tcClassDecl2 :: RenamedClassDecl -- The class declaration
- -> NF_TcM s (LIE s, TcHsBinds s)
+ -> NF_TcM s (LIE s, TcMonoBinds s)
tcClassDecl2 (ClassDecl context class_name
- tyvar_name class_sigs default_binds pragmas src_loc)
+ tyvar_names class_sigs default_binds pragmas _ _ src_loc)
| not (isLocallyDefined class_name)
- = returnNF_Tc (emptyLIE, EmptyBinds)
+ = returnNF_Tc (emptyLIE, EmptyMonoBinds)
| otherwise -- It is locally defined
- = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $
- tcAddSrcLoc src_loc $
+ = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
+ 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
- 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}
-
-%************************************************************************
-%* *
-\subsection[ClassDcl-bld-sels]{Building the selector functions for methods and superclasses}
-%* *
-%************************************************************************
-
-\begin{code}
-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 s (TcHsBinds s)
-
-buildSelectors clas clas_tyvar clas_tc_tyvar scs sc_sel_ids ops op_sel_ids
- =
- -- Make new Ids for the components of the dictionary
+ tcLookupClass class_name `thenTc` \ (_, clas) ->
let
- clas_tyvar_ty = mkTyVarTy clas_tc_tyvar
- mk_op_ty = tcInstType [(clas_tyvar, clas_tyvar_ty)] . classOpLocalType
+ (tyvars, sc_theta, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
+
+ -- The selector binds are already in the selector Id's unfoldings
+-- sel_binds = [ CoreMonoBind (RealId sel_id) (getUnfoldingTemplate (getIdUnfolding sel_id))
+-- | sel_id <- sc_sel_ids ++ op_sel_ids,
+-- isLocallyDefined sel_id
+-- ]
+--
+-- final_sel_binds = andMonoBindList sel_binds
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) ->
+ -- Generate bindings for the default methods
+ tcDefaultMethodBinds clas default_binds `thenTc` \ (const_insts, meth_binds) ->
- newDicts ClassDeclOrigin
- [ (clas, clas_tyvar_ty) ] `thenNF_Tc` \ (_,[clas_dict]) ->
-
- -- Make suitable bindings for the selectors
- 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 (zipWithEqual mk_sel op_sel_ids method_ids) `thenNF_Tc` \ op_sel_binds ->
- listNF_Tc (zipWithEqual mk_sel sc_sel_ids dict_ids) `thenNF_Tc` \ sc_sel_binds ->
-
- returnNF_Tc (SingleBind (
- NonRecBind (
- foldr AndMonoBinds
- (foldr AndMonoBinds EmptyMonoBinds op_sel_binds)
- sc_sel_binds
- )))
+ returnTc (const_insts, meth_binds)
+-- final_sel_binds `AndMonoBinds` meth_binds)
+-- Leave 'em out for now. They always get inlined anyway. SLPJ June '98
\end{code}
%************************************************************************
%* *
-\subsection[ClassDcl-misc]{Miscellaneous}
-%* *
-%************************************************************************
-
-Make a selector expression for @sel_id@ from a dictionary @clas_dict@
-consisting of @dicts@ and @methods@.
-
-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 = /\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} 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
-\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}
-
-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)
- = let
- (op_tyvars,op_theta,op_tau) = splitSigmaTy (idType op)
- op_tys = mkTyVarTys op_tyvars
- in
- newDicts ClassDeclOrigin op_theta `thenNF_Tc` \ (_, op_dicts) ->
-
- -- sel_id = /\ clas_tyvar op_tyvars -> \ clas_dict op_dicts ->
- -- case clas_dict of
- -- <dicts..methods> -> method_or_dict op_tyvars op_dicts
-
- returnNF_Tc (VarMonoBind (RealId sel_id) (
- TyLam (clas_tyvar:op_tyvars) (
- DictLam (clas_dict:op_dicts) (
- HsCase
- (HsVar clas_dict)
- ([PatMatch (DictPat dicts methods) (
- GRHSMatch (GRHSsAndBindsOut
- [OtherwiseGRHS
- (mkHsDictApp (mkHsTyApp (HsVar method_or_dict) op_tys) op_dicts)
- mkGeneratedSrcLoc]
- EmptyBinds
- op_tau))])
- mkGeneratedSrcLoc
- ))))
-\end{code}
-
-
-%************************************************************************
-%* *
\subsection[Default methods]{Default methods}
%* *
%************************************************************************
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 -> \dord -> defm.Foo.op2 [a] b dfoo_list dord
+ op2 = defm.Foo.op2 [a] dfoo_list
dfoo_list = (op1, op2)
in
dfoo_list
\end{verbatim}
\begin{code}
-buildDefaultMethodBinds
+tcDefaultMethodBinds
:: Class
- -> TcTyVar s
- -> [Id]
-> RenamedMonoBinds
- -> TcM s (LIE s, TcHsBinds s)
-
-buildDefaultMethodBinds clas clas_tyvar
- default_method_ids default_binds
- = -- Deal with the method declarations themselves
- mapNF_Tc unZonkId default_method_ids `thenNF_Tc` \ tc_defm_ids ->
- processInstBinds
- clas
- (makeClassDeclDefaultMethodRhs clas default_method_ids)
- [] -- No tyvars in scope for "this inst decl"
- emptyLIE -- No insts available
- (map TcId tc_defm_ids)
- default_binds `thenTc` \ (dicts_needed, default_binds') ->
-
- returnTc (dicts_needed, SingleBind (NonRecBind default_binds'))
-\end{code}
+ -> TcM s (LIE s, TcMonoBinds s)
-@makeClassDeclDefaultMethodRhs@ builds the default method for a
-class declaration when no explicit default method is given.
+tcDefaultMethodBinds clas default_binds
+ = -- Construct suitable signatures
+ tcInstTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, inst_env) ->
+
+ -- Typecheck the default bindings
+ let
+ tc_dm sel_id_w_dm@(_, Just dm_id)
+ = tcMethodBind clas origin inst_tys clas_tyvars
+ default_binds [{-no prags-}] False
+ sel_id_w_dm `thenTc` \ (bind, insts, (_, local_dm_id)) ->
+ returnTc (bind, insts, (clas_tyvars, RealId dm_id, local_dm_id))
+ in
+ mapAndUnzip3Tc tc_dm sel_ids_w_dms `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) $
+
+ -- tcMethodBind has checked that the class_tyvars havn't
+ -- been unified with each other or another type, but we must
+ -- still zonk them
+ mapNF_Tc zonkTcTyVarBndr clas_tyvars `thenNF_Tc` \ clas_tyvars' ->
+
+ tcSimplifyAndCheck
+ (ptext SLIT("class") <+> ppr clas)
+ (mkVarSet 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` andMonoBindList defm_binds)
+ in
+ returnTc (const_lie, full_binds)
-\begin{code}
-makeClassDeclDefaultMethodRhs
- :: Class
- -> [Id]
- -> Int
- -> NF_TcM s (TcExpr s)
-
-makeClassDeclDefaultMethodRhs clas method_ids tag
- = tcInstType [] (idType method_id) `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))))
where
- (clas_mod, clas_name) = moduleNamePair clas
+ (tyvars, sc_theta, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
- method_id = method_ids !! (tag-1)
- class_op = (classOps clas) !! (tag-1)
+ sel_ids_w_dms = [pair | pair@(_, Just _) <- op_sel_ids `zip` defm_ids]
+ -- Just the ones for which there is an explicit
+ -- user default declaration
- error_msg = _UNPK_ clas_mod ++ "." ++ _UNPK_ clas_name ++ "."
- ++ (ppShow 80 (ppr PprForUser class_op))
- ++ "\""
+ origin = ClassDeclOrigin
\end{code}
+@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.
-Contexts
-~~~~~~~~
\begin{code}
-classDeclCtxt class_name sty
- = ppCat [ppStr "In the class declaration for", ppr sty class_name]
+tcMethodBind
+ :: Class
+ -> 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
+ -> RenamedMonoBinds -- Method binding (pick the right one from in here)
+ -> [RenamedSig] -- Pramgas (just for this one)
+ -> Bool -- True <=> supply default decl if no explicit decl
+ -- This is true for instance decls,
+ -- false for class decls
+ -> (Id, Maybe Id) -- The method selector and default-method Id
+ -> TcM s (TcMonoBinds s, LIE s, (LIE s, TcIdOcc s))
+
+tcMethodBind clas origin inst_tys inst_tyvars
+ meth_binds prags supply_default_bind
+ (sel_id, maybe_dm_id)
+ = tcGetSrcLoc `thenNF_Tc` \ loc ->
+
+ newMethod origin (RealId sel_id) inst_tys `thenNF_Tc` \ meth@(_, TcId meth_id) ->
+ mkTcSig meth_id loc `thenNF_Tc` \ sig_info ->
+
+ let
+ meth_name = idName meth_id
+ maybe_user_bind = find_bind meth_name meth_binds
+
+ no_user_bind = case maybe_user_bind of {Nothing -> True; other -> False}
+ no_user_default = case maybe_dm_id of {Nothing -> True; other -> False}
+
+ meth_bind = case maybe_user_bind of
+ Just bind -> bind
+ Nothing -> mk_default_bind meth_name loc
+
+ meth_prags = find_prags meth_name prags
+ in
+
+ -- Warn if no method binding, only if -fwarn-missing-methods
+ if no_user_bind && not supply_default_bind then
+ pprPanic "tcMethodBind" (ppr clas <+> ppr inst_tys)
+ else
+ warnTc (opt_WarnMissingMethods && no_user_bind && no_user_default)
+ (omittedMethodWarn sel_id clas) `thenNF_Tc_`
+
+ -- Check the pragmas
+ tcExtendLocalValEnv [meth_name] [meth_id] (
+ tcPragmaSigs meth_prags
+ ) `thenTc` \ (prag_info_fn, prag_binds1, prag_lie) ->
+
+ -- Check the bindings
+ tcExtendGlobalTyVars (mkVarSet inst_tyvars) (
+ tcAddErrCtxt (methodCtxt sel_id) $
+ tcBindWithSigs NotTopLevel meth_bind [sig_info]
+ NonRecursive prag_info_fn
+ ) `thenTc` \ (binds, insts, _) ->
+
+
+ -- The prag_lie for a SPECIALISE pragma will mention the function
+ -- itself, so we have to simplify them away right now lest they float
+ -- outwards!
+ bindInstsOfLocalFuns prag_lie [meth_id] `thenTc` \ (prag_lie', prag_binds2) ->
+
+
+ -- Now check that the instance type variables
+ -- (or, in the case of a class decl, the class tyvars)
+ -- have not been unified with anything in the environment
+ tcAddErrCtxtM (sigCtxt (quotes (ppr sel_id)) (idType meth_id)) (
+ checkSigTyVars inst_tyvars `thenTc_`
+
+ returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2,
+ insts `plusLIE` prag_lie',
+ meth))
+
+ where
+ sel_name = idName sel_id
+
+ -- The renamer just puts the selector ID as the binder in the method binding
+ -- but we must use the method name; so we substitute it here. Crude but simple.
+ find_bind meth_name (FunMonoBind op_name fix matches loc)
+ | op_name == sel_name = Just (FunMonoBind meth_name fix matches loc)
+ find_bind meth_name (PatMonoBind (VarPatIn op_name) rhs loc)
+ | op_name == sel_name = Just (PatMonoBind (VarPatIn meth_name) rhs loc)
+ find_bind meth_name (AndMonoBinds b1 b2)
+ = find_bind meth_name b1 `seqMaybe` find_bind meth_name b2
+ find_bind meth_name other = Nothing -- Default case
+
+
+ -- Find the prags for this method, and replace the
+ -- selector name with the method name
+ find_prags meth_name [] = []
+ find_prags meth_name (SpecSig name ty spec loc : prags)
+ | name == sel_name = SpecSig meth_name ty spec loc : find_prags meth_name prags
+ find_prags meth_name (InlineSig name loc : prags)
+ | name == sel_name = InlineSig meth_name loc : find_prags meth_name prags
+ find_prags meth_name (NoInlineSig name loc : prags)
+ | name == sel_name = NoInlineSig meth_name loc : find_prags meth_name prags
+ find_prags meth_name (prag:prags) = find_prags meth_name prags
+
+ mk_default_bind local_meth_name loc
+ = PatMonoBind (VarPatIn local_meth_name)
+ (GRHSsAndBindsIn (unguardedRHS (default_expr loc) loc) EmptyBinds)
+ loc
+
+ default_expr loc
+ = case maybe_dm_id of
+ Just dm_id -> HsVar (getName dm_id) -- There's a default method
+ Nothing -> error_expr loc -- No default method
+
+ error_expr loc = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
+ (HsLit (HsString (_PK_ (error_msg loc))))
+
+ error_msg loc = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
+\end{code}
+
+Contexts 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)
+
+superClassErr class_name sc
+ = ptext SLIT("Illegal superclass constraint") <+> quotes (pprClassAssertion sc)
+ <+> ptext SLIT("in declaration for class") <+> quotes (ppr class_name)
+
+methodCtxt sel_id
+ = ptext SLIT("In the definition for method") <+> quotes (ppr sel_id)
+
+badMethodErr bndr clas
+ = hsep [ptext SLIT("Class"), quotes (ppr clas),
+ ptext SLIT("does not have a method"), quotes (ppr bndr)]
+
+omittedMethodWarn sel_id clas
+ = sep [ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id),
+ ptext SLIT("in an instance declaration for") <+> quotes (ppr clas)]
\end{code}
projects / ghc-hetmet.git / blobdiff