\section[TcClassDcl]{Typechecking class declarations}
\begin{code}
-#include "HsVersions.h"
-
-module TcClassDcl ( tcClassDecl1, tcClassDecls2 ) where
+module TcClassDcl ( tcClassDecl1, tcClassDecls2, tcMethodBind, badMethodErr ) where
-IMP_Ubiq()
+#include "HsVersions.h"
-import HsSyn ( HsDecl(..), ClassDecl(..), HsBinds(..), MonoBinds(..),
- Match(..), GRHSsAndBinds(..), GRHS(..), HsExpr(..),
- DefaultDecl, TyDecl, InstDecl, IfaceSig, Fixity,
- HsLit(..), OutPat(..), Sig(..), HsType(..), HsTyVar,
- SYN_IE(RecFlag), nonRecursive, andMonoBinds,
- Stmt, DoOrListComp, ArithSeqInfo, InPat, Fake )
-import HsTypes ( getTyVarName )
+import HsSyn ( HsDecl(..), ClassDecl(..), Sig(..), MonoBinds(..),
+ InPat(..), andMonoBinds, getTyVarName
+ )
import HsPragmas ( ClassPragmas(..) )
+import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..) )
import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..),
- RenamedClassOpSig(..), SYN_IE(RenamedMonoBinds),
- RenamedGenPragmas(..), RenamedContext(..), SYN_IE(RenamedHsDecl)
+ RenamedClassOpSig(..), RenamedMonoBinds,
+ RenamedContext(..), RenamedHsDecl, RenamedSig
)
-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, tcAddImportedIdInfo,
- tcExtendGlobalTyVars )
-import TcInstDcls ( tcMethodBind )
-import TcKind ( unifyKind, TcKind )
+import TcHsSyn ( TcMonoBinds )
+
+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 ( SYN_IE(TcType), SYN_IE(TcTyVar), tcInstType, tcInstSigTyVars, tcInstSigType )
-import PragmaInfo ( PragmaInfo(..) )
-
-import Bag ( foldBag, unionManyBags )
-import Class ( GenClass, GenClassOp, mkClass, mkClassOp, classBigSig,
- classOps, classOpString, classOpLocalType, classDefaultMethodId,
- classOpTagByOccName, SYN_IE(ClassOp), SYN_IE(Class)
+import TcType ( TcType, TcTyVar, TcTyVarSet, tcInstSigTyVars,
+ zonkSigTyVar, tcInstSigTcType
+ )
+import FieldLabel ( firstFieldLabelTag )
+import Bag ( unionManyBags )
+import Class ( mkClass, classBigSig, Class )
+import CmdLineOpts ( opt_GlasgowExts )
+import MkId ( mkDataCon, mkSuperDictSelId,
+ mkMethodSelId, mkDefaultMethodId
)
-import CmdLineOpts ( opt_PprUserLength )
-import Id ( GenId, mkSuperDictSelId, mkMethodSelId,
- mkDefaultMethodId, getIdUnfolding,
- idType, SYN_IE(Id)
+import Id ( Id, StrictnessMark(..),
+ getIdUnfolding, idType, idName
)
import CoreUnfold ( getUnfoldingTemplate )
import IdInfo
-import Name ( Name, isLocallyDefined, moduleString,
- nameString, NamedThing(..) )
+import Name ( Name, isLocallyDefined, OccName, nameOccName,
+ NamedThing(..) )
import Outputable
-import PrelVals ( nO_DEFAULT_METHOD_ERROR_ID )
-import Pretty
-import PprType ( GenClass, GenType, GenTyVar, GenClassOp )
-import SpecEnv ( SpecEnv )
-import SrcLoc ( mkGeneratedSrcLoc )
-import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy,
- mkForAllTy, mkSigmaTy, splitSigmaTy, SYN_IE(Type)
+import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, splitRhoTy,
+ mkSigmaTy, mkForAllTys, Type, ThetaType
)
-import TysWiredIn ( stringTy )
-import TyVar ( unitTyVarSet, GenTyVar, SYN_IE(TyVar) )
-import Unique ( Unique )
-import UniqFM ( Uniquable(..) )
+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 (noIdInfo `addSpecInfo` spec,
+tcClassOpPragmas ty sel def spec ps = returnNF_Tc (spec `setSpecInfo` noIdInfo,
noIdInfo)
\end{code}
\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 `thenTc` \ (class_kind, rec_class) ->
- tcLookupTyVar (getTyVarName 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 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
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
- in
- returnTc clas
-\end{code}
-
- let
- clas_ty = mkTyVarTy clas_tyvar
- dict_component_tys = [mkDictTy sc clas_ty | sc <- scs] ++
- [classOpLocalType op | op <- ops])
+ dict_component_tys = sc_tys ++ op_tys
new_or_data = case dict_component_tys of
[_] -> NewType
other -> DataType
- dict_con_id = mkDataCon class_name
- [NotMarkedStrict]
+ dict_con_id = mkDataCon datacon_name
+ [NotMarkedStrict | _ <- dict_component_tys]
[{- No labelled fields -}]
- [clas_tyvar]
+ rec_tyvars
[{-No context-}]
+ [{-No existential tyvars-}] [{-Or context-}]
dict_component_tys
tycon
- tycon = mkDataTyCon class_name
- (tyVarKind rec_tyvar `mkArrowKind` mkBoxedTypeKind)
- [rec_tyvar]
- [{- Empty context -}]
- [dict_con_id]
- [{- No derived classes -}]
+ 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}
\begin{code}
-tcClassContext :: Class -> TyVar
+tcClassContext :: 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 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 ->
+ 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 `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
- rec_tyvar_ty = mkTyVarTy rec_tyvar
+ rec_tyvar_tys = mkTyVarTys rec_tyvars
- mk_super_id rec_class super_class
+ mk_super_id ((super_class, tys), index)
= tcGetUnique `thenNF_Tc` \ uniq ->
let
- ty = mkForAllTy rec_tyvar $
- mkFunTy (mkDictTy rec_class rec_tyvar_ty)
- (mkDictTy super_class rec_tyvar_ty)
+ ty = mkForAllTys rec_tyvars $
+ mkFunTy (mkDictTy rec_class rec_tyvar_tys) (mkDictTy super_class tys)
in
- returnTc (mkSuperDictSelId uniq rec_class super_class ty)
+ returnTc (mkSuperDictSelId uniq rec_class index ty)
-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
+tcClassSig :: TcEnv s -- 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 dm_name
+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.
-- and that it is not constrained by theta
tcHsType op_ty `thenTc` \ local_ty ->
let
- global_ty = mkSigmaTy [rec_clas_tyvar]
- [(rec_clas, mkTyVarTy rec_clas_tyvar)]
+ global_ty = mkSigmaTy rec_clas_tyvars
+ [(rec_clas, mkTyVarTys rec_clas_tyvars)]
local_ty
- class_op_nm = getOccName op_name
- class_op = mkClassOp class_op_nm
- (classOpTagByOccName rec_clas{-yeeps!-} class_op_nm)
- local_ty
in
-- Build the selector id and default method id
let
- sel_id = mkMethodSelId op_name rec_clas class_op global_ty
- defm_id = mkDefaultMethodId dm_name rec_clas class_op False global_ty
- -- 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
- tcAddImportedIdInfo defm_id `thenNF_Tc` \ final_defm_id ->
- returnTc (class_op, sel_id, final_defm_id)
- )
+ returnTc (local_ty, sel_id, maybe_dm_id)
\end{code}
\begin{code}
tcClassDecls2 :: [RenamedHsDecl]
- -> NF_TcM s (LIE s, TcHsBinds s)
+ -> NF_TcM s (LIE s, TcMonoBinds s)
tcClassDecls2 decls
= foldr combine
- (returnNF_Tc (emptyLIE, EmptyBinds))
+ (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 `thenTc` \ (_, clas) ->
let
- (tyvar, scs, sc_sel_ids, ops, op_sel_ids, defm_ids)
- = classBigSig clas
+ (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))
isLocallyDefined sel_id
]
- final_sel_binds = MonoBind (andMonoBinds sel_binds) [] nonRecursive
+ final_sel_binds = andMonoBinds sel_binds
in
-- Generate bindings for the default methods
- tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], _, _) ->
- mapAndUnzipTc (buildDefaultMethodBind clas clas_tyvar default_binds)
- (op_sel_ids `zip` [0..])
- `thenTc` \ (const_insts_s, meth_binds) ->
-
- returnTc (unionManyBags const_insts_s,
- final_sel_binds `ThenBinds`
- MonoBind (andMonoBinds meth_binds) [] nonRecursive)
+ tcDefaultMethodBinds clas default_binds `thenTc` \ (const_insts, meth_binds) ->
+
+ returnTc (const_insts,
+ final_sel_binds `AndMonoBinds` meth_binds)
\end{code}
%************************************************************************
\end{verbatim}
\begin{code}
-buildDefaultMethodBind
+tcDefaultMethodBinds
:: Class
- -> TcTyVar s
-> RenamedMonoBinds
- -> (Id, Int)
-> TcM s (LIE s, TcMonoBinds s)
-buildDefaultMethodBind clas clas_tyvar default_binds (sel_id, idx)
- = newDicts origin [(clas,inst_ty)] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+tcDefaultMethodBinds clas default_binds
+ = -- Construct suitable signatures
+ tcInstSigTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, inst_env) ->
+
+ -- Typecheck the default bindings
let
- avail_insts = this_dict
- defm_id = classDefaultMethodId clas idx
- no_prags name = NoPragmaInfo -- No pragmas yet for default methods
+ 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
- tcExtendGlobalTyVars clas_tyvar_set (
- tcMethodBind noDefmExpr inst_ty no_prags default_binds (sel_id, idx)
- ) `thenTc` \ (defm_bind, insts_needed, (_, local_defm_id)) ->
-
- -- CHECK THE CONTEXT OF THE DEFAULT-METHOD BINDS
+ tcAddErrCtxt (classDeclCtxt clas) $
+ mapNF_Tc zonkSigTyVar clas_tyvars `thenNF_Tc` \ clas_tyvars' ->
tcSimplifyAndCheck
- clas_tyvar_set
+ (ptext SLIT("class") <+> ppr clas)
+ (mkTyVarSet clas_tyvars')
avail_insts
- insts_needed `thenTc` \ (const_lie, dict_binds) ->
+ (unionManyBags insts_needed) `thenTc` \ (const_lie, dict_binds) ->
let
- defm_binds = AbsBinds
- [clas_tyvar]
+ full_binds = AbsBinds
+ clas_tyvars'
[this_dict_id]
- [([clas_tyvar], RealId defm_id, local_defm_id)]
- (dict_binds `AndMonoBinds` defm_bind)
+ abs_bind_stuff
+ (dict_binds `AndMonoBinds` andMonoBinds defm_binds)
in
- returnTc (const_lie, defm_binds)
+ returnTc (const_lie, full_binds)
where
- clas_tyvar_set = unitTyVarSet clas_tyvar
- inst_ty = mkTyVarTy clas_tyvar
- origin = ClassDeclOrigin
- noDefmExpr _ = HsApp (HsVar (getName nO_DEFAULT_METHOD_ERROR_ID))
- (HsLit (HsString (_PK_ error_msg)))
-
- error_msg = show (sep [text "Class", ppr (PprForUser opt_PprUserLength) clas,
- text "Method", ppr (PprForUser opt_PprUserLength) sel_id])
+ (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}
+@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}
+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
+ -> 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
-~~~~~~~~
+Contexts and errors
+~~~~~~~~~~~~~~~~~~~
\begin{code}
-classDeclCtxt class_name sty
- = hsep [ptext SLIT("In the class declaration for"), ppr sty class_name]
+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)
+
+methodCtxt sel_id
+ = ptext SLIT("In the definition for method") <+> quotes (ppr sel_id)
+
+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"))
+ ]
+
+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