\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
-module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where
+module TcInstDcls ( tcInstDecls1, tcInstDecls2, tcAddDeclCtxt ) where
#include "HsVersions.h"
-import HsSyn ( HsDecl(..), InstDecl(..),
- HsBinds(..), MonoBinds(..),
- HsExpr(..), InPat(..), HsLit(..), Sig(..),
- andMonoBindList
+
+import CmdLineOpts ( DynFlag(..), dopt )
+
+import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..),
+ MonoBinds(..), HsExpr(..), HsLit(..), Sig(..),
+ andMonoBindList, collectMonoBinders, isClassDecl
)
-import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl )
+import HsTypes ( HsType (..), HsTyVarBndr(..), toHsTyVar )
+import HsPat ( InPat (..) )
+import HsMatches ( Match (..) )
+import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl,
+ extractHsTyVars )
import TcHsSyn ( TcMonoBinds, mkHsConApp )
-
import TcBinds ( tcSpecSigs )
-import TcClassDcl ( tcMethodBind, checkFromThisClass )
-import TcMonad
-import RnMonad ( RnNameSupply, FixityEnv )
-import Inst ( Inst, InstOrigin(..),
+import TcClassDcl ( tcMethodBind, badMethodErr )
+import TcMonad
+import Inst ( InstOrigin(..),
newDicts, newClassDicts,
LIE, emptyLIE, plusLIE, plusLIEs )
import TcDeriv ( tcDeriving )
-import TcEnv ( ValueEnv, tcExtendGlobalValEnv, tcExtendTyVarEnvForMeths,
- tcAddImportedIdInfo, tcInstId, newDFunName
+import TcEnv ( TcEnv, tcExtendGlobalValEnv,
+ tcExtendTyVarEnvForMeths, TyThing (..),
+ tcAddImportedIdInfo, tcInstId, tcLookupClass,
+ newDFunName, tcExtendTyVarEnv
)
-import TcInstUtil ( InstInfo(..), classDataCon )
-import TcMonoType ( tcHsSigType )
+import InstEnv ( InstInfo(..), InstEnv, pprInstInfo, classDataCon,
+ simpleInstInfoTyCon, simpleInstInfoTy, isLocalInst,
+ extendInstEnv )
+import TcMonoType ( tcTyVars, tcHsSigType, tcHsType, kcHsSigType )
import TcSimplify ( tcSimplifyAndCheck )
-import TcType ( TcTyVar, zonkTcSigTyVars )
+import TcType ( zonkTcSigTyVars )
+import HscTypes ( PersistentCompilerState(..), HomeSymbolTable, DFunId,
+ ModDetails(..) )
import Bag ( emptyBag, unitBag, unionBags, unionManyBags,
- foldBag, Bag
+ foldBag, Bag, listToBag
)
-import CmdLineOpts ( opt_GlasgowExts, opt_AllowUndecidableInstances )
-import Class ( classBigSig, Class )
-import Var ( idName, idType, Id, TyVar )
-import Maybes ( maybeToBool, catMaybes, expectJust )
+import Class ( Class, DefMeth(..), classBigSig )
+import Var ( idName, idType )
+import Maybes ( maybeToBool, expectJust )
import MkId ( mkDictFunId )
-import Module ( Module )
-import Name ( isLocallyDefined, NamedThing(..) )
-import NameSet ( emptyNameSet )
+import Generics ( validGenericInstanceType )
+import Module ( Module, foldModuleEnv )
+import Name ( isLocallyDefined )
+import NameSet ( emptyNameSet, nameSetToList )
import PrelInfo ( eRROR_ID )
-import PprType ( pprConstraint )
-import TyCon ( isSynTyCon, tyConDerivings )
-import Type ( Type, isUnLiftedType, mkTyVarTys,
- splitSigmaTy, isTyVarTy,
- splitTyConApp_maybe, splitDictTy_maybe,
- getClassTys_maybe, splitAlgTyConApp_maybe,
- classesToPreds, classesOfPreds,
- unUsgTy, tyVarsOfTypes
+import PprType ( pprConstraint, pprPred )
+import TyCon ( TyCon, isSynTyCon, tyConDerivings )
+import Type ( mkTyVarTys, splitDFunTy, isTyVarTy,
+ splitTyConApp_maybe, splitDictTy,
+ splitAlgTyConApp_maybe, classesToPreds, classesOfPreds,
+ unUsgTy, tyVarsOfTypes, mkClassPred, mkTyVarTy,
+ getClassTys_maybe
)
-import Subst ( mkTopTyVarSubst, substClasses )
+import Subst ( mkTopTyVarSubst, substClasses, substTheta )
import VarSet ( mkVarSet, varSetElems )
-import TysWiredIn ( stringTy, isFFIArgumentTy, isFFIResultTy )
-import Unique ( Unique, cCallableClassKey, cReturnableClassKey, hasKey, Uniquable(..) )
+import TysWiredIn ( genericTyCons, isFFIArgumentTy, isFFIResultTy )
+import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey )
+import Name ( Name, NameEnv, extendNameEnv_C, emptyNameEnv,
+ plusNameEnv_C, nameEnvElts )
+import FiniteMap ( mapFM )
+import SrcLoc ( SrcLoc )
+import RnHsSyn -- ( RenamedMonoBinds )
+import VarSet ( varSetElems )
+import UniqFM ( mapUFM )
+import Unique ( Uniquable(..) )
+import BasicTypes ( NewOrData(..) )
+import ErrUtils ( dumpIfSet_dyn )
+import ListSetOps ( Assoc, emptyAssoc, plusAssoc_C, mapAssoc,
+ assocElts, extendAssoc_C,
+ equivClassesByUniq, minusList
+ )
+import List ( intersect, (\\), partition )
import Outputable
\end{code}
and $dbinds_super$ bind the superclass dictionaries sd1 \ldots sdm.
\end{enumerate}
+
+%************************************************************************
+%* *
+\subsection{Extracting instance decls}
+%* *
+%************************************************************************
+
+Gather up the instance declarations from their various sources
+
\begin{code}
-tcInstDecls1 :: ValueEnv -- Contains IdInfo for dfun ids
- -> [RenamedHsDecl]
+tcInstDecls1 :: PersistentCompilerState
+ -> HomeSymbolTable -- Contains instances
+ -> TcEnv -- Contains IdInfo for dfun ids
+ -> (Name -> Maybe Fixity) -- for deriving Show and Read
-> Module -- Module for deriving
- -> FixityEnv -- For derivings
- -> RnNameSupply -- For renaming derivings
- -> TcM s (Bag InstInfo,
- RenamedHsBinds)
-
-tcInstDecls1 unf_env decls mod fixs rn_name_supply
- = -- Do the ordinary instance declarations
- 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
- in
- -- Handle "derived" instances; note that we only do derivings
- -- for things in this module; we ignore deriving decls from
- -- interfaces!
- tcDeriving mod fixs rn_name_supply decl_inst_info
- `thenTc` \ (deriv_inst_info, deriv_binds) ->
+ -> [TyCon]
+ -> [RenamedHsDecl]
+ -> TcM (PersistentCompilerState, InstEnv, [InstInfo], RenamedHsBinds)
- let
- full_inst_info = deriv_inst_info `unionBags` decl_inst_info
+tcInstDecls1 pcs hst unf_env get_fixity mod local_tycons decls
+ = let
+ inst_decls = [inst_decl | InstD inst_decl <- decls]
+ clas_decls = [clas_decl | TyClD clas_decl <- decls, isClassDecl clas_decl]
in
- returnTc (full_inst_info, deriv_binds)
+ -- (1) Do the ordinary instance declarations
+ mapNF_Tc (tcInstDecl1 mod unf_env) inst_decls `thenNF_Tc` \ inst_infos ->
+
+ -- (2) Instances from generic class declarations
+ getGenericInstances mod clas_decls `thenTc` \ generic_inst_info ->
+
+ -- Next, construct the instance environment so far, consisting of
+ -- a) cached non-home-package InstEnv (gotten from pcs) pcs_insts pcs
+ -- b) imported instance decls (not in the home package) inst_env1
+ -- c) other modules in this package (gotten from hst) inst_env2
+ -- d) local instance decls inst_env3
+ -- e) generic instances inst_env4
+ -- The result of (b) replaces the cached InstEnv in the PCS
+ let
+ (local_inst_info, imported_inst_info)
+ = partition isLocalInst (concat inst_infos)
+ imported_dfuns = map (tcAddImportedIdInfo unf_env . iDFunId)
+ imported_inst_info
+ hst_dfuns = foldModuleEnv ((++) . md_insts) [] hst
+ in
+ addInstDFuns (pcs_insts pcs) imported_dfuns `thenNF_Tc` \ inst_env1 ->
+ addInstDFuns inst_env1 hst_dfuns `thenNF_Tc` \ inst_env2 ->
+ addInstInfos inst_env2 local_inst_info `thenNF_Tc` \ inst_env3 ->
+ addInstInfos inst_env3 generic_inst_info `thenNF_Tc` \ inst_env4 ->
+
+ -- (3) Compute instances from "deriving" clauses;
+ -- note that we only do derivings for things in this module;
+ -- we ignore deriving decls from interfaces!
+ -- This stuff computes a context for the derived instance decl, so it
+ -- needs to know about all the instances possible; hecne inst_env4
+ tcDeriving (pcs_PRS pcs) mod inst_env4 get_fixity local_tycons
+ `thenTc` \ (deriv_inst_info, deriv_binds) ->
+ addInstInfos inst_env4 deriv_inst_info
+ `thenNF_Tc` \ final_inst_env ->
+
+ returnTc (pcs { pcs_insts = inst_env1 },
+ final_inst_env,
+ generic_inst_info ++ deriv_inst_info ++ local_inst_info,
+ deriv_binds)
+
+addInstInfos :: InstEnv -> [InstInfo] -> NF_TcM InstEnv
+addInstInfos inst_env infos = addInstDFuns inst_env (map iDFunId infos)
+
+addInstDFuns :: InstEnv -> [DFunId] -> NF_TcM InstEnv
+addInstDFuns dfuns infos
+ = getDOptsTc `thenTc` \ dflags ->
+ extendInstEnv dflags dfuns infos `bind` \ (inst_env', errs) ->
+ addErrsTc errs `thenNF_Tc_`
+ returnTc inst_env'
+ where
+ bind x f = f x
-tcInstDecl1 :: Module -> ValueEnv -> RenamedInstDecl -> NF_TcM s (Bag InstInfo)
+\end{code}
+\begin{code}
+tcInstDecl1 :: Module -> TcEnv -> RenamedInstDecl -> NF_TcM [InstInfo]
+-- Deal with a single instance declaration
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) $
+ recoverNF_Tc (returnNF_Tc []) $
tcAddSrcLoc src_loc $
-- Type-check all the stuff before the "where"
tcHsSigType poly_ty `thenTc` \ poly_ty' ->
let
- (tyvars, theta, dict_ty) = splitSigmaTy poly_ty'
- constr = classesOfPreds theta
- (clas, inst_tys) = case splitDictTy_maybe dict_ty of
- Just ct -> ct
- Nothing -> pprPanic "tcInstDecl1" (ppr poly_ty)
+ (tyvars, theta, clas, inst_tys) = splitDFunTy poly_ty'
in
(case maybe_dfun_name of
-- contain something illegal in normal Haskell, notably
-- instance CCallable [Char]
scrutiniseInstanceHead clas inst_tys `thenNF_Tc_`
- mapNF_Tc scrutiniseInstanceConstraint constr `thenNF_Tc_`
+ mapNF_Tc scrutiniseInstanceConstraint theta `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)
+ returnNF_Tc (True, mkDictFunId dfun_name clas tyvars inst_tys theta)
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))
+ -- Make the dfun id
+ returnNF_Tc (False, mkDictFunId dfun_name clas tyvars inst_tys theta)
+ ) `thenNF_Tc` \ (is_local, dfun_id) ->
+
+ returnTc [InstInfo { iLocal = is_local,
+ iClass = clas, iTyVars = tyvars, iTys = inst_tys,
+ iTheta = theta, iDFunId = dfun_id,
+ iBinds = binds, iLoc = src_loc, iPrags = uprags }]
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{Extracting generic instance declaration from class declarations}
+%* *
+%************************************************************************
+
+@getGenericInstances@ extracts the generic instance declarations from a class
+declaration. For exmaple
+
+ class C a where
+ op :: a -> a
+
+ op{ x+y } (Inl v) = ...
+ op{ x+y } (Inr v) = ...
+ op{ x*y } (v :*: w) = ...
+ op{ 1 } Unit = ...
+
+gives rise to the instance declarations
+
+ instance C (x+y) where
+ op (Inl v) = ...
+ op (Inr v) = ...
+
+ instance C (x*y) where
+ op (v :*: w) = ...
+
+ instance C 1 where
+ op Unit = ...
+
+
+\begin{code}
+getGenericInstances :: Module -> [RenamedTyClDecl] -> TcM [InstInfo]
+getGenericInstances mod class_decls
+ = mapTc (get_generics mod) class_decls `thenTc` \ gen_inst_infos ->
+ let
+ gen_inst_info = concat gen_inst_infos
+ in
+ getDOptsTc `thenTc` \ dflags ->
+ ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances"
+ (vcat (map pprInstInfo gen_inst_info)))
+ `thenNF_Tc_`
+ returnTc gen_inst_info
+
+get_generics mod decl@(ClassDecl context class_name tyvar_names
+ fundeps class_sigs def_methods
+ name_list loc)
+ | null groups
+ = returnTc [] -- The comon case:
+ -- no generic default methods, or
+ -- its an imported class decl (=> has no methods at all)
+
+ | otherwise -- A local class decl with generic default methods
+ = recoverNF_Tc (returnNF_Tc []) $
+ tcAddDeclCtxt decl $
+ tcLookupClass class_name `thenTc` \ clas ->
+
+ -- Make an InstInfo out of each group
+ mapTc (mkGenericInstance mod clas loc) groups `thenTc` \ inst_infos ->
+
+ -- Check that there is only one InstInfo for each type constructor
+ -- The main way this can fail is if you write
+ -- f {| a+b |} ... = ...
+ -- f {| x+y |} ... = ...
+ -- Then at this point we'll have an InstInfo for each
+ let
+ bad_groups = [group | group <- equivClassesByUniq get_uniq inst_infos,
+ length group > 1]
+ get_uniq inst = getUnique (simpleInstInfoTyCon inst)
+ in
+ mapTc (addErrTc . dupGenericInsts) bad_groups `thenTc_`
+
+ -- Check that there is an InstInfo for each generic type constructor
+ let
+ missing = genericTyCons `minusList` map simpleInstInfoTyCon inst_infos
+ in
+ checkTc (null missing) (missingGenericInstances missing) `thenTc_`
+
+ returnTc inst_infos
+
+ where
+ -- Group the declarations by type pattern
+ groups :: [(RenamedHsType, RenamedMonoBinds)]
+ groups = assocElts (getGenericBinds def_methods)
+
+
+---------------------------------
+getGenericBinds :: RenamedMonoBinds -> Assoc RenamedHsType RenamedMonoBinds
+ -- Takes a group of method bindings, finds the generic ones, and returns
+ -- them in finite map indexed by the type parameter in the definition.
+
+getGenericBinds EmptyMonoBinds = emptyAssoc
+getGenericBinds (AndMonoBinds m1 m2)
+ = plusAssoc_C AndMonoBinds (getGenericBinds m1) (getGenericBinds m2)
+
+getGenericBinds (FunMonoBind id infixop matches loc)
+ = mapAssoc wrap (foldr add emptyAssoc matches)
+ where
+ add match env = case maybeGenericMatch match of
+ Nothing -> env
+ Just (ty, match') -> extendAssoc_C (++) env (ty, [match'])
+
+ wrap ms = FunMonoBind id infixop ms loc
+
+---------------------------------
+mkGenericInstance :: Module -> Class -> SrcLoc
+ -> (RenamedHsType, RenamedMonoBinds)
+ -> TcM InstInfo
+
+mkGenericInstance mod clas loc (hs_ty, binds)
+ -- Make a generic instance declaration
+ -- For example: instance (C a, C b) => C (a+b) where { binds }
+
+ = -- Extract the universally quantified type variables
+ tcTyVars (nameSetToList (extractHsTyVars hs_ty))
+ (kcHsSigType hs_ty) `thenTc` \ tyvars ->
+ tcExtendTyVarEnv tyvars $
+
+ -- Type-check the instance type, and check its form
+ tcHsSigType hs_ty `thenTc` \ inst_ty ->
+ checkTc (validGenericInstanceType inst_ty)
+ (badGenericInstanceType binds) `thenTc_`
+
+ -- Make the dictionary function.
+ newDFunName mod clas [inst_ty] loc `thenNF_Tc` \ dfun_name ->
+ let
+ inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars]
+ inst_tys = [inst_ty]
+ dfun_id = mkDictFunId dfun_name clas tyvars inst_tys inst_theta
+ in
+
+ returnTc (InstInfo { iLocal = True,
+ iClass = clas, iTyVars = tyvars, iTys = inst_tys,
+ iTheta = inst_theta, iDFunId = dfun_id, iBinds = binds,
+ iLoc = loc, iPrags = [] })
\end{code}
%************************************************************************
\begin{code}
-tcInstDecls2 :: Bag InstInfo
- -> NF_TcM s (LIE, TcMonoBinds)
+tcInstDecls2 :: [InstInfo]
+ -> NF_TcM (LIE, TcMonoBinds)
tcInstDecls2 inst_decls
- = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyMonoBinds)) inst_decls
+-- = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyMonoBinds)) inst_decls
+ = foldr combine (returnNF_Tc (emptyLIE, EmptyMonoBinds))
+ (map tcInstDecl2 inst_decls)
where
combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
tc2 `thenNF_Tc` \ (lie2, binds2) ->
binds1 `AndMonoBinds` binds2)
\end{code}
-
======= New documentation starts here (Sept 92) ==============
The main purpose of @tcInstDecl2@ is to return a @HsBinds@ which defines
First comes the easy case of a non-local instance decl.
\begin{code}
-tcInstDecl2 :: InstInfo -> NF_TcM s (LIE, TcMonoBinds)
+tcInstDecl2 :: InstInfo -> NF_TcM (LIE, TcMonoBinds)
-tcInstDecl2 (InstInfo clas inst_tyvars inst_tys
- inst_decl_theta
- dfun_id monobinds
- locn uprags)
+tcInstDecl2 (InstInfo { iClass = clas, iTyVars = inst_tyvars, iTys = inst_tys,
+ iTheta = inst_decl_theta, iDFunId = dfun_id,
+ iBinds = monobinds, iLoc = locn, iPrags = uprags })
| not (isLocallyDefined dfun_id)
= returnNF_Tc (emptyLIE, EmptyMonoBinds)
recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
tcAddSrcLoc locn $
- -- Check that all the method bindings come from this class
- checkFromThisClass clas monobinds `thenNF_Tc_`
-
-- Instantiate the instance decl with tc-style type variables
tcInstId dfun_id `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') ->
let
- (clas, inst_tys') = expectJust "tcInstDecl2" (splitDictTy_maybe dict_ty')
-
- origin = InstanceDeclOrigin
+ (clas, inst_tys') = splitDictTy dict_ty'
+ origin = InstanceDeclOrigin
(class_tyvars, sc_theta, _, op_items) = classBigSig clas
- dm_ids = [dm_id | (_, dm_id, _) <- op_items]
+ dm_ids = [dm_id | (_, DefMeth dm_id) <- op_items]
+ sel_names = [idName sel_id | (sel_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
+ inst_decl_theta' = substTheta (mkTopTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars'))
+ inst_decl_theta
- -- Instantiate the super-class context with inst_tys
+ -- Instantiate the super-class context with inst_tys
sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys') sc_theta
+
+ -- Find any definitions in monobinds that aren't from the class
+ bad_bndrs = collectMonoBinders monobinds `minusList` sel_names
in
+ -- Check that all the method bindings come from this class
+ mapTc (addErrTc . badMethodErr clas) bad_bndrs `thenNF_Tc_`
+
-- 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]) ->
+ newClassDicts 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, _) ->
+ 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 (tcMethodBind clas origin inst_tyvars' inst_tys'
- (classesToPreds inst_decl_theta')
+ inst_decl_theta'
monobinds uprags True)
op_items
)) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) ->
-- mention the constructor, which doesn't exist for CCallable, CReturnable
-- Hardly beautiful, but only three extra lines.
HsApp (TyApp (HsVar eRROR_ID) [(unUsgTy . idType) this_dict_id])
- (HsLitOut (HsString msg) stringTy)
+ (HsLit (HsString msg))
| otherwise -- The common case
= mkHsConApp dict_constr inst_tys' (map HsVar (sc_dict_ids ++ meth_ids))
We can also have instances for functions: @instance Foo (a -> b) ...@.
\begin{code}
-scrutiniseInstanceConstraint (clas, tys)
- | all isTyVarTy tys
- || opt_AllowUndecidableInstances = returnNF_Tc ()
- | otherwise = addErrTc (instConstraintErr clas tys)
+scrutiniseInstanceConstraint pred
+ = getDOptsTc `thenTc` \ dflags -> case () of
+ ()
+ | dopt Opt_AllowUndecidableInstances dflags
+ -> returnNF_Tc ()
+
+ | Just (clas,tys) <- getClassTys_maybe pred,
+ all isTyVarTy tys
+ -> returnNF_Tc ()
+
+ | otherwise
+ -> addErrTc (instConstraintErr pred)
scrutiniseInstanceHead clas inst_taus
- | -- CCALL CHECK
+ = getDOptsTc `thenTc` \ dflags -> case () of
+ ()
+ | -- CCALL CHECK
-- A user declaration of a CCallable/CReturnable instance
-- must be for a "boxed primitive" type.
- (clas `hasKey` cCallableClassKey && not (ccallable_type first_inst_tau)) ||
- (clas `hasKey` cReturnableClassKey && not (creturnable_type first_inst_tau))
- = addErrTc (nonBoxedPrimCCallErr clas first_inst_tau)
+ (clas `hasKey` cCallableClassKey
+ && not (ccallable_type dflags 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)
- = addErrTc (derivingWhenInstanceExistsErr clas first_inst_tau)
+ | maybeToBool alg_tycon_app_maybe && clas `elem` (tyConDerivings alg_tycon)
+ -> 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 ()
+ | dopt Opt_AllowUndecidableInstances dflags
+ -> 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 ()
+ | dopt Opt_GlasgowExts dflags
+ -> 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 (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 (varSetElems (tyVarsOfTypes arg_tys)) == length arg_tys
- -- This last condition checks that all the type variables are distinct
- )
- = addErrTc (instTypeErr clas inst_taus
- (text "the instance type must be of form (T a b c)" $$
- text "where T is not a synonym, and a,b,c are distinct type variables")
- )
-
- | otherwise
- = returnNF_Tc ()
+ | not (length inst_taus == 1 &&
+ maybeToBool maybe_tycon_app && -- Yes, there's a type constuctor
+ not (isSynTyCon tycon) && -- ...but not a synonym
+ all isTyVarTy arg_tys && -- Applied to type variables
+ length (varSetElems (tyVarsOfTypes arg_tys)) == length arg_tys
+ -- This last condition checks that all the type variables are distinct
+ )
+ -> addErrTc (instTypeErr clas inst_taus
+ (text "the instance type must be of form (T a b c)" $$
+ text "where T is not a synonym, and a,b,c are distinct type variables")
+ )
+
+ | otherwise
+ -> returnNF_Tc ()
where
(first_inst_tau : _) = inst_taus
-- The "Alg" part looks through synonyms
Just (alg_tycon, _, _) = alg_tycon_app_maybe
-ccallable_type ty = isFFIArgumentTy False {- Not safe call -} ty
-creturnable_type ty = isFFIResultTy ty
+ ccallable_type dflags ty = isFFIArgumentTy dflags False {- Not safe call -} ty
+ creturnable_type ty = isFFIResultTy ty
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{Error messages}
+%* *
+%************************************************************************
+
+\begin{code}
+tcAddDeclCtxt decl thing_inside
+ = tcAddSrcLoc loc $
+ tcAddErrCtxt ctxt $
+ thing_inside
+ where
+ (name, loc, thing)
+ = case decl of
+ (ClassDecl _ name _ _ _ _ _ loc) -> (name, loc, "class")
+ (TySynonym name _ _ loc) -> (name, loc, "type synonym")
+ (TyData NewType _ name _ _ _ _ loc _ _) -> (name, loc, "newtype")
+ (TyData DataType _ name _ _ _ _ loc _ _) -> (name, loc, "data type")
+
+ ctxt = hsep [ptext SLIT("In the"), text thing,
+ ptext SLIT("declaration for"), quotes (ppr name)]
\end{code}
\begin{code}
-instConstraintErr clas tys
+instConstraintErr pred
= hang (ptext SLIT("Illegal constraint") <+>
- quotes (pprConstraint clas tys) <+>
+ quotes (pprPred pred) <+>
ptext SLIT("in instance context"))
4 (ptext SLIT("(Instance contexts must constrain only type variables)"))
+badGenericInstanceType binds
+ = vcat [ptext SLIT("Illegal type pattern in the generic bindings"),
+ nest 4 (ppr binds)]
+
+missingGenericInstances missing
+ = ptext SLIT("Missing type patterns for") <+> pprQuotedList missing
+
+
+
+dupGenericInsts inst_infos
+ = vcat [ptext SLIT("More than one type pattern for a single generic type constructor:"),
+ nest 4 (vcat (map (ppr . simpleInstInfoTy) inst_infos)),
+ ptext SLIT("All the type patterns for a generic type constructor must be identical")
+ ]
+
instTypeErr clas tys msg
= sep [ptext SLIT("Illegal instance declaration for") <+> quotes (pprConstraint clas tys),
nest 4 (parens msg)
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