%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
-module TcInstDcls (
- tcInstDecls1,
- tcInstDecls2
- ) where
+module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where
#include "HsVersions.h"
import HsSyn ( HsDecl(..), InstDecl(..),
- HsBinds(..), MonoBinds(..), GRHSsAndBinds(..), GRHS(..),
- HsExpr(..), InPat(..), HsLit(..), Sig(..),
- unguardedRHS,
- collectMonoBinders, andMonoBinds
- )
-import HsBinds ( sigsForMe )
-import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds,
- RenamedInstDecl, RenamedHsExpr,
- RenamedSig, RenamedHsDecl
- )
-import TcHsSyn ( TcMonoBinds, TcIdOcc(..), TcIdBndr,
- maybeBoxedPrimType, tcIdType
+ MonoBinds(..), HsExpr(..), HsLit(..), Sig(..),
+ andMonoBindList
)
+import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl )
+import TcHsSyn ( TcMonoBinds, mkHsConApp )
-import TcBinds ( tcPragmaSigs )
-import TcClassDcl ( tcMethodBind, badMethodErr )
+import TcBinds ( tcSpecSigs )
+import TcClassDcl ( tcMethodBind, checkFromThisClass )
import TcMonad
-import RnMonad ( RnNameSupply )
-import Inst ( Inst, InstOrigin(..),
- newDicts, LIE, emptyLIE, plusLIE, plusLIEs )
+import RnMonad ( RnNameSupply, FixityEnv )
+import Inst ( InstOrigin(..),
+ newDicts, newClassDicts,
+ LIE, emptyLIE, plusLIE, plusLIEs )
import TcDeriv ( tcDeriving )
-import TcEnv ( tcExtendGlobalValEnv, tcAddImportedIdInfo )
-import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, classDataCon )
-import TcKind ( TcKind, unifyKind )
-import TcMonoType ( tcHsType )
-import TcSimplify ( tcSimplifyAndCheck )
-import TcType ( TcType, TcTyVar, TcTyVarSet,
- zonkSigTyVar, tcInstSigTyVars, tcInstType, tcInstTheta
+import TcEnv ( ValueEnv, tcExtendGlobalValEnv, tcExtendTyVarEnvForMeths,
+ tcAddImportedIdInfo, tcInstId, newDFunName
)
+import TcInstUtil ( InstInfo(..), classDataCon )
+import TcMonoType ( tcHsSigType )
+import TcSimplify ( tcSimplifyAndCheck )
+import TcType ( zonkTcSigTyVars )
import Bag ( emptyBag, unitBag, unionBags, unionManyBags,
- foldBag, bagToList, Bag
- )
-import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods )
-import Class ( classBigSig, Class )
-import Id ( isNullaryDataCon, dataConArgTys, replaceIdInfo, idName, Id )
-import Maybes ( maybeToBool, seqMaybe, catMaybes )
-import Name ( nameOccName, mkLocalName,
- isLocallyDefined, Module,
- NamedThing(..)
+ foldBag, Bag
)
-import PrelVals ( nO_METHOD_BINDING_ERROR_ID, eRROR_ID )
-import PprType ( pprParendType, pprConstraint )
-import SrcLoc ( SrcLoc, noSrcLoc )
-import TyCon ( isSynTyCon, isDataTyCon, tyConDerivings )
-import Type ( Type, ThetaType, isUnpointedType,
- splitSigmaTy, isTyVarTy, mkSigmaTy,
+import CmdLineOpts ( opt_GlasgowExts, opt_AllowUndecidableInstances )
+import Class ( classBigSig )
+import Var ( idName, idType )
+import Maybes ( maybeToBool, expectJust )
+import MkId ( mkDictFunId )
+import Module ( Module )
+import Name ( isLocallyDefined )
+import NameSet ( emptyNameSet )
+import PrelInfo ( eRROR_ID )
+import PprType ( pprConstraint )
+import TyCon ( isSynTyCon, tyConDerivings )
+import Type ( mkTyVarTys, splitSigmaTy, isTyVarTy,
splitTyConApp_maybe, splitDictTy_maybe,
- splitAlgTyConApp_maybe, splitRhoTy,
- tyVarsOfTypes
+ splitAlgTyConApp_maybe,
+ classesToPreds, classesOfPreds,
+ unUsgTy, tyVarsOfTypes
)
-import TyVar ( zipTyVarEnv, mkTyVarSet, tyVarSetToList, TyVar )
-import TysPrim ( byteArrayPrimTyCon, mutableByteArrayPrimTyCon )
-import TysWiredIn ( stringTy )
-import Unique ( Unique, cCallableClassKey, cReturnableClassKey, Uniquable(..) )
+import Subst ( mkTopTyVarSubst, substClasses )
+import VarSet ( mkVarSet, varSetElems )
+import TysWiredIn ( isFFIArgumentTy, isFFIResultTy )
+import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey )
import Outputable
\end{code}
\end{enumerate}
\begin{code}
-tcInstDecls1 :: TcEnv s -- Contains IdInfo for dfun ids
+tcInstDecls1 :: ValueEnv -- Contains IdInfo for dfun ids
-> [RenamedHsDecl]
- -> Module -- module name for deriving
- -> RnNameSupply -- for renaming derivings
+ -> Module -- Module for deriving
+ -> FixityEnv -- For derivings
+ -> RnNameSupply -- For renaming derivings
-> TcM s (Bag InstInfo,
- RenamedHsBinds,
- SDoc)
+ RenamedHsBinds)
-tcInstDecls1 unf_env decls mod_name rn_name_supply
+tcInstDecls1 unf_env decls mod fixs rn_name_supply
= -- Do the ordinary instance declarations
- mapNF_Tc (tcInstDecl1 unf_env mod_name)
+ mapNF_Tc (tcInstDecl1 mod unf_env)
[inst_decl | InstD inst_decl <- decls] `thenNF_Tc` \ inst_info_bags ->
let
decl_inst_info = unionManyBags inst_info_bags
-- Handle "derived" instances; note that we only do derivings
-- for things in this module; we ignore deriving decls from
-- interfaces!
- tcDeriving mod_name rn_name_supply decl_inst_info
- `thenTc` \ (deriv_inst_info, deriv_binds, ddump_deriv) ->
+ tcDeriving mod fixs rn_name_supply decl_inst_info
+ `thenTc` \ (deriv_inst_info, deriv_binds) ->
let
full_inst_info = deriv_inst_info `unionBags` decl_inst_info
in
- returnTc (full_inst_info, deriv_binds, ddump_deriv)
+ returnTc (full_inst_info, deriv_binds)
-tcInstDecl1 :: TcEnv s -> Module -> RenamedInstDecl -> NF_TcM s (Bag InstInfo)
+tcInstDecl1 :: Module -> ValueEnv -> RenamedInstDecl -> NF_TcM s (Bag InstInfo)
-tcInstDecl1 unf_env mod_name (InstDecl poly_ty binds uprags (Just dfun_name) src_loc)
+tcInstDecl1 mod unf_env (InstDecl poly_ty binds uprags maybe_dfun_name src_loc)
= -- Prime error recovery, set source location
recoverNF_Tc (returnNF_Tc emptyBag) $
tcAddSrcLoc src_loc $
-- Type-check all the stuff before the "where"
- tcHsType poly_ty `thenTc` \ poly_ty' ->
+ tcHsSigType poly_ty `thenTc` \ poly_ty' ->
let
(tyvars, theta, dict_ty) = splitSigmaTy poly_ty'
- (clas, inst_tys) = case splitDictTy_maybe dict_ty of
- Nothing -> pprPanic "tcInstDecl1" (ppr poly_ty)
- Just pair -> pair
+ constr = classesOfPreds theta
+ (clas, inst_tys) = case splitDictTy_maybe dict_ty of
+ Just ct -> ct
+ Nothing -> pprPanic "tcInstDecl1" (ppr poly_ty)
in
- -- Check for respectable instance type
- scrutiniseInstanceType clas inst_tys `thenTc_`
-
- -- Make the dfun id and constant-method ids
- let
- (dfun_id, dfun_theta) = mkInstanceRelatedIds dfun_name
- clas tyvars inst_tys theta
- -- Add info from interface file
- final_dfun_id = tcAddImportedIdInfo unf_env dfun_id
- in
- returnTc (unitBag (InstInfo clas tyvars inst_tys theta
- dfun_theta final_dfun_id
- binds src_loc uprags))
+ (case maybe_dfun_name of
+ Nothing -> -- A source-file instance declaration
+
+ -- Check for respectable instance type, and context
+ -- but only do this for non-imported instance decls.
+ -- Imported ones should have been checked already, and may indeed
+ -- contain something illegal in normal Haskell, notably
+ -- instance CCallable [Char]
+ scrutiniseInstanceHead clas inst_tys `thenNF_Tc_`
+ mapNF_Tc scrutiniseInstanceConstraint constr `thenNF_Tc_`
+
+ -- Make the dfun id and return it
+ newDFunName mod clas inst_tys src_loc `thenNF_Tc` \ dfun_name ->
+ returnNF_Tc (mkDictFunId dfun_name clas tyvars inst_tys constr)
+
+ Just dfun_name -> -- An interface-file instance declaration
+ -- Make the dfun id and add info from interface file
+ let
+ dfun_id = mkDictFunId dfun_name clas tyvars inst_tys constr
+ in
+ returnNF_Tc (tcAddImportedIdInfo unf_env dfun_id)
+ ) `thenNF_Tc` \ dfun_id ->
+
+ returnTc (unitBag (InstInfo clas tyvars inst_tys constr dfun_id binds src_loc uprags))
\end{code}
\begin{code}
tcInstDecls2 :: Bag InstInfo
- -> NF_TcM s (LIE s, TcMonoBinds s)
+ -> NF_TcM s (LIE, TcMonoBinds)
tcInstDecls2 inst_decls
= foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyMonoBinds)) inst_decls
First comes the easy case of a non-local instance decl.
\begin{code}
-tcInstDecl2 :: InstInfo -> NF_TcM s (LIE s, TcMonoBinds s)
+tcInstDecl2 :: InstInfo -> NF_TcM s (LIE, TcMonoBinds)
tcInstDecl2 (InstInfo clas inst_tyvars inst_tys
- inst_decl_theta dfun_theta
+ inst_decl_theta
dfun_id monobinds
locn uprags)
| not (isLocallyDefined dfun_id)
= returnNF_Tc (emptyLIE, EmptyMonoBinds)
-{-
- -- I deleted this "optimisation" because when importing these
- -- instance decls the renamer would look for the dfun bindings and they weren't there.
- -- This would be fixable, but it seems simpler just to produce a tiny void binding instead,
- -- even though it's never used.
-
- -- This case deals with CCallable etc, which don't need any bindings
- | isNoDictClass clas
- = returnNF_Tc (emptyLIE, EmptyBinds)
--}
-
| otherwise
= -- Prime error recovery
recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
tcAddSrcLoc locn $
- -- Get the class signature
- let
- origin = InstanceDeclOrigin
- (class_tyvars,
- sc_theta, sc_sel_ids,
- op_sel_ids, defm_ids) = classBigSig clas
- in
-
+ -- Check that all the method bindings come from this class
+ checkFromThisClass clas monobinds `thenNF_Tc_`
+
-- Instantiate the instance decl with tc-style type variables
- tcInstSigTyVars inst_tyvars `thenNF_Tc` \ (inst_tyvars', _, tenv) ->
- mapNF_Tc (tcInstType tenv) inst_tys `thenNF_Tc` \ inst_tys' ->
- tcInstTheta tenv dfun_theta `thenNF_Tc` \ dfun_theta' ->
- tcInstTheta tenv inst_decl_theta `thenNF_Tc` \ inst_decl_theta' ->
+ tcInstId dfun_id `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') ->
+ let
+ (clas, inst_tys') = expectJust "tcInstDecl2" (splitDictTy_maybe dict_ty')
- -- Instantiate the super-class context with inst_tys
- tcInstTheta (zipTyVarEnv class_tyvars inst_tys') sc_theta `thenNF_Tc` \ sc_theta' ->
+ origin = InstanceDeclOrigin
- -- Create dictionary Ids from the specified instance contexts.
- newDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) ->
- newDicts origin dfun_theta' `thenNF_Tc` \ (dfun_arg_dicts, dfun_arg_dicts_ids) ->
- newDicts origin inst_decl_theta' `thenNF_Tc` \ (inst_decl_dicts, _) ->
- newDicts origin [(clas,inst_tys')] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+ (class_tyvars, sc_theta, _, op_items) = classBigSig clas
- -- Check that all the method bindings come from this class
- let
- check_from_this_class (bndr, loc)
- | nameOccName bndr `elem` sel_names = returnNF_Tc ()
- | otherwise = tcAddSrcLoc loc $
- addErrTc (badMethodErr bndr clas)
- sel_names = map getOccName op_sel_ids
- bndrs = bagToList (collectMonoBinders monobinds)
- in
- mapNF_Tc check_from_this_class bndrs `thenNF_Tc_`
+ dm_ids = [dm_id | (_, dm_id, _) <- op_items]
+
+ -- Instantiate the theta found in the original instance decl
+ inst_decl_theta' = substClasses (mkTopTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars'))
+ inst_decl_theta
- tcExtendGlobalValEnv (catMaybes defm_ids) (
+ -- Instantiate the super-class context with inst_tys
+ sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys') sc_theta
+ in
+ -- Create dictionary Ids from the specified instance contexts.
+ newClassDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) ->
+ newDicts origin dfun_theta' `thenNF_Tc` \ (dfun_arg_dicts, dfun_arg_dicts_ids) ->
+ newClassDicts origin inst_decl_theta' `thenNF_Tc` \ (inst_decl_dicts, _) ->
+ newClassDicts origin [(clas,inst_tys')] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+ tcExtendTyVarEnvForMeths inst_tyvars inst_tyvars' (
+ tcExtendGlobalValEnv dm_ids (
-- Default-method Ids may be mentioned in synthesised RHSs
- mapAndUnzip3Tc (tcInstMethodBind clas inst_tys' inst_tyvars' monobinds uprags)
- (op_sel_ids `zip` defm_ids)
- ) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) ->
- -- Deal with SPECIALISE instance pragmas
+ mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys'
+ (classesToPreds inst_decl_theta')
+ monobinds uprags True)
+ op_items
+ )) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) ->
+
+ -- Deal with SPECIALISE instance pragmas by making them
+ -- look like SPECIALISE pragmas for the dfun
let
- dfun_prags = [Sig (idName dfun_id) ty loc | SpecInstSig ty loc <- uprags]
+ dfun_prags = [SpecSig (idName dfun_id) ty loc | SpecInstSig ty loc <- uprags]
in
tcExtendGlobalValEnv [dfun_id] (
- tcPragmaSigs dfun_prags
- ) `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
+ tcSpecSigs dfun_prags
+ ) `thenTc` \ (prag_binds, prag_lie) ->
-- Check the overloading constraints of the methods and superclasses
- mapNF_Tc zonkSigTyVar inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars ->
+ -- tcMethodBind has checked that the class_tyvars havn't
+ -- been unified with each other or another type, but we must
+ -- still zonk them before passing them to tcSimplifyAndCheck
+ zonkTcSigTyVars inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars ->
let
- inst_tyvars_set = mkTyVarSet zonked_inst_tyvars
+ inst_tyvars_set = mkVarSet zonked_inst_tyvars
(meth_lies, meth_ids) = unzip meth_lies_w_ids
methods_lie = plusLIEs insts_needed_s
in
+ -- Ditto method bindings
+ tcAddErrCtxt methodCtxt (
+ tcSimplifyAndCheck
+ (ptext SLIT("instance declaration context"))
+ inst_tyvars_set -- Local tyvars
+ avail_insts
+ methods_lie
+ ) `thenTc` \ (const_lie1, lie_binds1) ->
+
-- Check that we *could* construct the superclass dictionaries,
-- even though we are *actually* going to pass the superclass dicts in;
- -- the check ensures that the caller will never have a problem building
- -- them.
+ -- the check ensures that the caller will never have
+ --a problem building them.
tcAddErrCtxt superClassCtxt (
tcSimplifyAndCheck
(ptext SLIT("instance declaration context"))
inst_tyvars_set -- Local tyvars
inst_decl_dicts -- The instance dictionaries available
sc_dicts -- The superclass dicationaries reqd
- ) `thenTc_`
+ ) `thenTc` \ _ ->
-- Ignore the result; we're only doing
-- this to make sure it can be done.
- -- Ditto method bindings
- tcAddErrCtxt methodCtxt (
- tcSimplifyAndCheck
- (ptext SLIT("instance declaration context"))
- inst_tyvars_set -- Local tyvars
- avail_insts
- methods_lie
- ) `thenTc_`
-
- -- Now do the simplification again, this time to get the
- -- bindings; this time we use an enhanced "avails"
- -- Ignore errors because they come from the *previous* tcSimplifys
+ -- Now do the simplification again, this time to get the
+ -- bindings; this time we use an enhanced "avails"
+ -- Ignore errors because they come from the *previous* tcSimplify
discardErrsTc (
tcSimplifyAndCheck
(ptext SLIT("instance declaration context"))
inst_tyvars_set
dfun_arg_dicts -- NB! Don't include this_dict here, else the sc_dicts
-- get bound by just selecting from this_dict!!
- (sc_dicts `plusLIE` methods_lie `plusLIE` prag_lie)
- ) `thenTc` \ (const_lie, lie_binds) ->
+ sc_dicts
+ ) `thenTc` \ (const_lie2, lie_binds2) ->
-- Create the result bindings
-- emit an error message. This in turn means that we don't
-- mention the constructor, which doesn't exist for CCallable, CReturnable
-- Hardly beautiful, but only three extra lines.
- HsApp (TyApp (HsVar (RealId eRROR_ID)) [tcIdType this_dict_id])
- (HsLitOut (HsString msg) stringTy)
+ HsApp (TyApp (HsVar eRROR_ID) [(unUsgTy . idType) this_dict_id])
+ (HsLit (HsString msg))
| otherwise -- The common case
- = foldl HsApp (TyApp (HsVar (RealId dict_constr)) inst_tys')
- (map HsVar (sc_dict_ids ++ meth_ids))
+ = mkHsConApp dict_constr inst_tys' (map HsVar (sc_dict_ids ++ meth_ids))
-- We don't produce a binding for the dict_constr; instead we
-- rely on the simplifier to unfold this saturated application
+ -- We do this rather than generate an HsCon directly, because
+ -- it means that the special cases (e.g. dictionary with only one
+ -- member) are dealt with by the common MkId.mkDataConWrapId code rather
+ -- than needing to be repeated here.
+
where
msg = _PK_ ("Compiler error: bad dictionary " ++ showSDoc (ppr clas))
dict_bind = VarMonoBind this_dict_id dict_rhs
- method_binds = andMonoBinds method_binds_s
+ method_binds = andMonoBindList method_binds_s
- final_dfun_id = replaceIdInfo dfun_id (prag_info_fn (idName dfun_id))
- -- Pretty truesome
main_bind
= AbsBinds
zonked_inst_tyvars
dfun_arg_dicts_ids
- [(inst_tyvars', RealId final_dfun_id, this_dict_id)]
- (lie_binds `AndMonoBinds`
+ [(inst_tyvars', dfun_id, this_dict_id)]
+ emptyNameSet -- No inlines (yet)
+ (lie_binds1 `AndMonoBinds`
+ lie_binds2 `AndMonoBinds`
method_binds `AndMonoBinds`
- prag_binds `AndMonoBinds`
dict_bind)
in
- returnTc (const_lie,
+ returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie,
main_bind `AndMonoBinds` prag_binds)
\end{code}
%************************************************************************
%* *
-\subsection{Processing each method}
-%* *
-%************************************************************************
-
-\begin{code}
-tcInstMethodBind
- :: Class
- -> [TcType s] -- Instance types
- -> [TcTyVar s] -- and their free (sig) tyvars
- -> RenamedMonoBinds -- Method binding
- -> [RenamedSig] -- Pragmas
- -> (Id, Maybe Id) -- Selector id and default-method id
- -> TcM s (TcMonoBinds s, LIE s, (LIE s, TcIdOcc s))
-
-tcInstMethodBind clas inst_tys inst_tyvars meth_binds prags (sel_id, maybe_dm_id)
- = tcGetSrcLoc `thenNF_Tc` \ loc ->
- tcGetUnique `thenNF_Tc` \ uniq ->
- let
- sel_name = idName sel_id
- meth_occ = getOccName sel_name
- default_meth_name = mkLocalName uniq meth_occ loc
- maybe_meth_bind = find meth_occ meth_binds
- the_meth_bind = case maybe_meth_bind of
- Just stuff -> stuff
- Nothing -> mk_default_bind default_meth_name loc
- meth_prags = sigsForMe (== sel_name) prags
- in
-
- -- Warn if no method binding, only if -fwarn-missing-methods
-
- warnTc (opt_WarnMissingMethods &&
- not (maybeToBool maybe_meth_bind) &&
- not (maybeToBool maybe_dm_id))
- (omittedMethodWarn sel_id clas) `thenNF_Tc_`
-
- -- Typecheck the method binding
- tcMethodBind clas origin inst_tys inst_tyvars sel_id the_meth_bind meth_prags
- where
- origin = InstanceDeclOrigin -- Poor
-
- find occ EmptyMonoBinds = Nothing
- find occ (AndMonoBinds b1 b2) = find occ b1 `seqMaybe` find occ b2
-
- find occ b@(FunMonoBind op_name _ _ _) | nameOccName op_name == occ = Just b
- | otherwise = Nothing
- find occ b@(PatMonoBind (VarPatIn op_name) _ _) | nameOccName op_name == occ = Just b
- | otherwise = Nothing
- find occ other = panic "Urk! Bad instance method binding"
-
-
- 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}
-
-
-
-%************************************************************************
-%* *
\subsection{Checking for a decent instance type}
%* *
%************************************************************************
-@scrutiniseInstanceType@ checks the type {\em and} its syntactic constraints:
+@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints:
it must normally look like: @instance Foo (Tycon a b c ...) ...@
The exceptions to this syntactic checking: (1)~if the @GlasgowExts@
We can also have instances for functions: @instance Foo (a -> b) ...@.
\begin{code}
-scrutiniseInstanceType clas inst_taus
- | -- CCALL CHECK (a).... urgh!
- -- To verify that a user declaration of a CCallable/CReturnable
- -- instance is OK, we must be able to see the constructor(s)
- -- of the instance type (see next guard.)
- --
- -- We flag this separately to give a more precise error msg.
- --
- (uniqueOf clas == cCallableClassKey || uniqueOf clas == cReturnableClassKey)
- && is_alg_tycon_app && not constructors_visible
- = failWithTc (invisibleDataConPrimCCallErr clas first_inst_tau)
-
- | -- CCALL CHECK (b)
+scrutiniseInstanceConstraint (clas, tys)
+ | all isTyVarTy tys
+ || opt_AllowUndecidableInstances = returnNF_Tc ()
+ | otherwise = addErrTc (instConstraintErr clas tys)
+
+scrutiniseInstanceHead clas inst_taus
+ | -- CCALL CHECK
-- A user declaration of a CCallable/CReturnable instance
-- must be for a "boxed primitive" type.
- (uniqueOf clas == cCallableClassKey && not (ccallable_type first_inst_tau)) ||
- (uniqueOf clas == cReturnableClassKey && not (creturnable_type first_inst_tau))
- = failWithTc (nonBoxedPrimCCallErr clas first_inst_tau)
+ (clas `hasKey` cCallableClassKey && not (ccallable_type first_inst_tau)) ||
+ (clas `hasKey` cReturnableClassKey && not (creturnable_type first_inst_tau))
+ = addErrTc (nonBoxedPrimCCallErr clas first_inst_tau)
-- DERIVING CHECK
-- It is obviously illegal to have an explicit instance
-- for something that we are also planning to `derive'
| maybeToBool alg_tycon_app_maybe && clas `elem` (tyConDerivings alg_tycon)
- = failWithTc (derivingWhenInstanceExistsErr clas first_inst_tau)
+ = addErrTc (derivingWhenInstanceExistsErr clas first_inst_tau)
-- Kind check will have ensured inst_taus is of length 1
+ -- Allow anything for AllowUndecidableInstances
+ | opt_AllowUndecidableInstances
+ = returnNF_Tc ()
+
+ -- If GlasgowExts then check at least one isn't a type variable
+ | opt_GlasgowExts
+ = if all isTyVarTy inst_taus then
+ addErrTc (instTypeErr clas inst_taus (text "There must be at least one non-type-variable in the instance head"))
+ else
+ returnNF_Tc ()
+
-- WITH HASKELL 1.4, MUST HAVE C (T a b c)
- | not opt_GlasgowExts
- && not (length inst_taus == 1 &&
+ | not (length inst_taus == 1 &&
maybeToBool maybe_tycon_app && -- Yes, there's a type constuctor
not (isSynTyCon tycon) && -- ...but not a synonym
all isTyVarTy arg_tys && -- Applied to type variables
- length (tyVarSetToList (tyVarsOfTypes arg_tys)) == length arg_tys
+ length (varSetElems (tyVarsOfTypes arg_tys)) == length arg_tys
-- This last condition checks that all the type variables are distinct
)
- = failWithTc (instTypeErr clas inst_taus
+ = addErrTc (instTypeErr clas inst_taus
(text "the instance type must be of form (T a b c)" $$
text "where T is not a synonym, and a,b,c are distinct type variables")
)
| otherwise
- = returnTc ()
+ = returnNF_Tc ()
where
(first_inst_tau : _) = inst_taus
Just (tycon, arg_tys) = maybe_tycon_app
-- Stuff for an *algebraic* data type
- alg_tycon_app_maybe = splitAlgTyConApp_maybe first_inst_tau
- -- The "Alg" part looks through synonyms
- is_alg_tycon_app = maybeToBool alg_tycon_app_maybe
- Just (alg_tycon, _, data_cons) = alg_tycon_app_maybe
-
- constructors_visible = not (null data_cons)
+ alg_tycon_app_maybe = splitAlgTyConApp_maybe first_inst_tau
+ -- The "Alg" part looks through synonyms
+ Just (alg_tycon, _, _) = alg_tycon_app_maybe
-
--- These conditions come directly from what the DsCCall is capable of.
--- Totally grotesque. Green card should solve this.
-
-ccallable_type ty = isUnpointedType ty || -- Allow CCallable Int# etc
- maybeToBool (maybeBoxedPrimType ty) || -- Ditto Int etc
- ty == stringTy ||
- byte_arr_thing
- where
- byte_arr_thing = case splitAlgTyConApp_maybe ty of
- Just (tycon, ty_args, [data_con]) | isDataTyCon tycon ->
- length data_con_arg_tys == 2 &&
- maybeToBool maybe_arg2_tycon &&
- (arg2_tycon == byteArrayPrimTyCon ||
- arg2_tycon == mutableByteArrayPrimTyCon)
- where
- data_con_arg_tys = dataConArgTys data_con ty_args
- (data_con_arg_ty1 : data_con_arg_ty2 : _) = data_con_arg_tys
- maybe_arg2_tycon = splitTyConApp_maybe data_con_arg_ty2
- Just (arg2_tycon,_) = maybe_arg2_tycon
-
- other -> False
-
-creturnable_type ty = maybeToBool (maybeBoxedPrimType ty) ||
- -- Or, a data type with a single nullary constructor
- case (splitAlgTyConApp_maybe ty) of
- Just (tycon, tys_applied, [data_con])
- -> isNullaryDataCon data_con
- other -> False
+ccallable_type ty = isFFIArgumentTy False {- Not safe call -} ty
+creturnable_type ty = isFFIResultTy ty
\end{code}
\begin{code}
-
+instConstraintErr clas tys
+ = hang (ptext SLIT("Illegal constraint") <+>
+ quotes (pprConstraint clas tys) <+>
+ ptext SLIT("in instance context"))
+ 4 (ptext SLIT("(Instance contexts must constrain only type variables)"))
+
instTypeErr clas tys msg
= sep [ptext SLIT("Illegal instance declaration for") <+> quotes (pprConstraint clas tys),
nest 4 (parens msg)
4 (hsep [ ptext SLIT("class"), ppr clas, ptext SLIT("type"),
ppr inst_ty])
-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)]
-
-{-
- Declaring CCallable & CReturnable instances in a module different
- from where the type was defined. Caused by importing data type
- abstractly (either programmatically or by the renamer being over-eager
- in its pruning.)
--}
-invisibleDataConPrimCCallErr clas inst_ty
- = hang (hsep [ptext SLIT("Constructors for"), quotes (ppr inst_ty),
- ptext SLIT("not visible when checking"),
- quotes (ppr clas), ptext SLIT("instance")])
- 4 (hsep [text "(Try either importing", ppr inst_ty,
- text "non-abstractly or compile using -fno-prune-tydecls ..)"])
-
methodCtxt = ptext SLIT("When checking the methods of an instance declaration")
superClassCtxt = ptext SLIT("When checking the superclasses of an instance declaration")
\end{code}
projects / ghc-hetmet.git / blobdiff