\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(..), HsType(..),
+ MonoBinds(..), HsExpr(..), HsLit(..), Sig(..),
+ andMonoBindList, collectMonoBinders, isClassDecl, toHsType
)
-import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl )
-import TcHsSyn ( TcMonoBinds,
- maybeBoxedPrimType
+import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl,
+ RenamedMonoBinds, RenamedTyClDecl, RenamedHsType,
+ extractHsTyVars, maybeGenericMatch
)
-
+import TcHsSyn ( TcMonoBinds, mkHsConApp )
import TcBinds ( tcSpecSigs )
-import TcClassDcl ( tcMethodBind, checkFromThisClass )
-import TcMonad
-import RnMonad ( RnNameSupply, Fixities )
-import Inst ( Inst, InstOrigin(..),
- newDicts, LIE, emptyLIE, plusLIE, plusLIEs )
+import TcClassDcl ( tcMethodBind, badMethodErr )
+import TcMonad
+import TcType ( tcInstType )
+import Inst ( InstOrigin(..),
+ newDicts, instToId,
+ LIE, mkLIE, emptyLIE, plusLIE, plusLIEs )
import TcDeriv ( tcDeriving )
-import TcEnv ( ValueEnv, tcExtendGlobalValEnv, tcExtendTyVarEnvForMeths,
- tcAddImportedIdInfo, tcInstId
+import TcEnv ( TcEnv, tcExtendGlobalValEnv,
+ tcExtendTyVarEnvForMeths,
+ tcAddImportedIdInfo, tcLookupClass,
+ InstInfo(..), pprInstInfo, simpleInstInfoTyCon,
+ simpleInstInfoTy, newDFunName, tcExtendTyVarEnv,
+ isLocalThing,
)
-import TcInstUtil ( InstInfo(..), classDataCon )
-import TcMonoType ( tcHsTopType )
-import TcSimplify ( tcSimplifyAndCheck )
-import TcType ( TcTyVar, zonkTcTyVarBndr )
-
-import Bag ( emptyBag, unitBag, unionBags, unionManyBags,
- foldBag, Bag
+import InstEnv ( InstEnv, extendInstEnv )
+import TcMonoType ( tcTyVars, tcHsSigType, kcHsSigType, checkSigTyVars )
+import TcSimplify ( tcSimplifyCheck )
+import HscTypes ( HomeSymbolTable, DFunId,
+ ModDetails(..), PackageInstEnv, PersistentRenamerState
)
-import CmdLineOpts ( opt_GlasgowExts, opt_AllowUndecidableInstances )
-import Class ( classBigSig, Class )
-import Var ( idName, idType, Id, TyVar )
-import DataCon ( isNullaryDataCon, dataConArgTys, dataConId )
-import Maybes ( maybeToBool, catMaybes, expectJust )
+
+import DataCon ( classDataCon )
+import Class ( Class, DefMeth(..), classBigSig )
+import Var ( idName, idType )
+import VarSet ( emptyVarSet )
+import Maybes ( maybeToBool )
import MkId ( mkDictFunId )
-import Module ( ModuleName )
-import Name ( isLocallyDefined, NamedThing(..) )
-import NameSet ( emptyNameSet )
+import FunDeps ( checkInstFDs )
+import Generics ( validGenericInstanceType )
+import Module ( Module, foldModuleEnv )
+import Name ( getSrcLoc )
+import NameSet ( emptyNameSet, unitNameSet, nameSetToList )
import PrelInfo ( eRROR_ID )
-import PprType ( pprConstraint )
-import SrcLoc ( SrcLoc )
-import TyCon ( isSynTyCon, isDataTyCon, tyConDerivings )
-import Type ( Type, isUnLiftedType, mkTyVarTys,
- splitSigmaTy, isTyVarTy,
- splitTyConApp_maybe, splitDictTy_maybe, unUsgTy,
- splitAlgTyConApp_maybe,
- tyVarsOfTypes
+import PprType ( pprClassPred, pprPred )
+import TyCon ( TyCon, isSynTyCon )
+import Type ( splitDFunTy, isTyVarTy,
+ splitTyConApp_maybe, splitDictTy,
+ splitForAllTys,
+ tyVarsOfTypes, mkClassPred, mkTyVarTy,
+ isTyVarClassPred, inheritablePred
)
import Subst ( mkTopTyVarSubst, substTheta )
-import VarSet ( mkVarSet, varSetElems )
-import TysPrim ( byteArrayPrimTyCon, mutableByteArrayPrimTyCon )
-import TysWiredIn ( stringTy )
-import Unique ( Unique, cCallableClassKey, cReturnableClassKey, Uniquable(..) )
+import VarSet ( varSetElems )
+import TysWiredIn ( genericTyCons, isFFIArgumentTy, isFFIImportResultTy )
+import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey )
+import Name ( Name )
+import SrcLoc ( SrcLoc )
+import VarSet ( varSetElems )
+import Unique ( Uniquable(..) )
+import BasicTypes ( NewOrData(..), Fixity )
+import ErrUtils ( dumpIfSet_dyn )
+import ListSetOps ( Assoc, emptyAssoc, plusAssoc_C, mapAssoc,
+ assocElts, extendAssoc_C,
+ equivClassesByUniq, minusList
+ )
+import List ( 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
+tcInstDecls1 :: PackageInstEnv
+ -> PersistentRenamerState
+ -> HomeSymbolTable -- Contains instances
+ -> TcEnv -- Contains IdInfo for dfun ids
+ -> (Name -> Maybe Fixity) -- for deriving Show and Read
+ -> Module -- Module for deriving
-> [RenamedHsDecl]
- -> ModuleName -- module name for deriving
- -> Fixities
- -> RnNameSupply -- for renaming derivings
- -> TcM s (Bag InstInfo,
- RenamedHsBinds)
-
-tcInstDecls1 unf_env decls mod_name fixs rn_name_supply
- = -- Do the ordinary instance declarations
- mapNF_Tc (tcInstDecl1 unf_env)
- [inst_decl | InstD inst_decl <- decls] `thenNF_Tc` \ inst_info_bags ->
- let
- decl_inst_info = unionManyBags inst_info_bags
+ -> TcM (PackageInstEnv, InstEnv, [InstInfo], RenamedHsBinds)
+
+tcInstDecls1 inst_env0 prs hst unf_env get_fixity this_mod decls
+ = let
+ inst_decls = [inst_decl | InstD inst_decl <- decls]
+ tycl_decls = [decl | TyClD decl <- decls]
+ clas_decls = filter isClassDecl tycl_decls
in
- -- Handle "derived" instances; note that we only do derivings
- -- for things in this module; we ignore deriving decls from
- -- interfaces!
- tcDeriving mod_name fixs rn_name_supply decl_inst_info
- `thenTc` \ (deriv_inst_info, deriv_binds) ->
+ -- (1) Do the ordinary instance declarations
+ mapNF_Tc tcInstDecl1 inst_decls `thenNF_Tc` \ inst_infos ->
+
+ -- (2) Instances from generic class declarations
+ getGenericInstances 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 (isLocalThing this_mod . iDFunId) (concat inst_infos)
+ imported_dfuns = map (tcAddImportedIdInfo unf_env . iDFunId)
+ imported_inst_info
+ hst_dfuns = foldModuleEnv ((++) . md_insts) [] hst
+ in
+ addInstDFuns inst_env0 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 prs this_mod inst_env4 get_fixity tycl_decls
+ `thenTc` \ (deriv_inst_info, deriv_binds) ->
+ addInstInfos inst_env4 deriv_inst_info `thenNF_Tc` \ final_inst_env ->
+
+ returnTc (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 ->
let
- full_inst_info = deriv_inst_info `unionBags` decl_inst_info
+ (inst_env', errs) = extendInstEnv dflags dfuns infos
in
- returnTc (full_inst_info, deriv_binds)
-
+ addErrsTc errs `thenNF_Tc_`
+ returnTc inst_env'
+\end{code}
-tcInstDecl1 :: ValueEnv -> RenamedInstDecl -> NF_TcM s (Bag InstInfo)
-
-tcInstDecl1 unf_env (InstDecl poly_ty binds uprags dfun_name src_loc)
+\begin{code}
+tcInstDecl1 :: RenamedInstDecl -> NF_TcM [InstInfo]
+-- Deal with a single instance declaration
+tcInstDecl1 decl@(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"
- tcHsTopType poly_ty `thenTc` \ poly_ty' ->
+ tcAddErrCtxt (instDeclCtxt 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
+ (tyvars, theta, clas, inst_tys) = splitDFunTy poly_ty'
in
- -- 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]
- (if isLocallyDefined dfun_name then
- scrutiniseInstanceHead clas inst_tys `thenNF_Tc_`
- mapNF_Tc scrutiniseInstanceConstraint theta
- else
- returnNF_Tc []
- ) `thenNF_Tc_`
-
- -- Make the dfun id
+ (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]
+ getDOptsTc `thenTc` \ dflags ->
+ checkInstValidity dflags theta clas inst_tys `thenTc_`
+
+ -- Make the dfun id and return it
+ newDFunName clas inst_tys src_loc `thenNF_Tc` \ dfun_name ->
+ returnNF_Tc (True, dfun_name)
+
+ Just dfun_name -> -- An interface-file instance declaration
+ -- Make the dfun id
+ returnNF_Tc (False, dfun_name)
+ ) `thenNF_Tc` \ (is_local, dfun_name) ->
+
let
dfun_id = mkDictFunId dfun_name clas tyvars inst_tys theta
+ in
+ returnTc [InstInfo { iDFunId = dfun_id,
+ iBinds = binds, 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 :: [RenamedTyClDecl] -> TcM [InstInfo]
+getGenericInstances class_decls
+ = mapTc get_generics class_decls `thenTc` \ gen_inst_infos ->
+ let
+ gen_inst_info = concat gen_inst_infos
+ in
+ if null gen_inst_info then
+ returnTc []
+ else
+ 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 decl@(ClassDecl {tcdMeths = Nothing})
+ = returnTc [] -- Imported class decls
+
+get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, tcdLoc = loc})
+ | null groups
+ = returnTc [] -- The comon case: no generic default methods
+
+ | 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 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
+ tc_inst_infos :: [(TyCon, InstInfo)]
+ tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos]
+
+ bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos,
+ length group > 1]
+ get_uniq (tc,_) = getUnique tc
+ in
+ mapTc (addErrTc . dupGenericInsts) bad_groups `thenTc_`
+
+ -- Check that there is an InstInfo for each generic type constructor
+ let
+ missing = genericTyCons `minusList` [tc | (tc,_) <- tc_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 (foldl add emptyAssoc matches)
+ -- Using foldl not foldr is vital, else
+ -- we reverse the order of the bindings!
+ where
+ add env match = case maybeGenericMatch match of
+ Nothing -> env
+ Just (ty, match') -> extendAssoc_C (++) env (ty, [match'])
+
+ wrap ms = FunMonoBind id infixop ms loc
- -- Add info from interface file
- final_dfun_id = tcAddImportedIdInfo unf_env dfun_id
+---------------------------------
+mkGenericInstance :: Class -> SrcLoc
+ -> (RenamedHsType, RenamedMonoBinds)
+ -> TcM InstInfo
+
+mkGenericInstance 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 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 (unitBag (InstInfo clas tyvars inst_tys theta
- final_dfun_id
- binds src_loc uprags))
+
+ returnTc (InstInfo { iDFunId = dfun_id,
+ iBinds = binds, 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 clas inst_tyvars inst_tys
- 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)
--}
+tcInstDecl2 :: InstInfo -> NF_TcM (LIE, TcMonoBinds)
+-- tcInstDecl2 is called *only* on InstInfos
- | otherwise
+tcInstDecl2 (InstInfo { iDFunId = dfun_id,
+ iBinds = monobinds, iPrags = uprags })
= -- Prime error recovery
- recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
- tcAddSrcLoc locn $
+ recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
+ tcAddSrcLoc (getSrcLoc dfun_id) $
+ tcAddErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $
-- Instantiate the instance decl with tc-style type variables
- tcInstId dfun_id `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') ->
+ tcInstType (idType dfun_id) `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') ->
let
- (clas, inst_tys') = expectJust "tcInstDecl2" (splitDictTy_maybe dict_ty')
+ (clas, inst_tys') = splitDictTy dict_ty'
+ origin = InstanceDeclOrigin
- origin = InstanceDeclOrigin
+ (class_tyvars, sc_theta, _, op_items) = classBigSig clas
- (class_tyvars,
- sc_theta, sc_sel_ids,
- op_sel_ids, defm_ids) = classBigSig clas
+ 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' = 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' = substTheta (mkTopTyVarSubst class_tyvars inst_tys') sc_theta
- in
- -- 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]) ->
+ -- Find any definitions in monobinds that aren't from the class
+ bad_bndrs = collectMonoBinders monobinds `minusList` sel_names
+
+ -- The type variable from the dict fun actually scope
+ -- over the bindings. They were gotten from
+ -- the original instance declaration
+ (inst_tyvars, _) = splitForAllTys (idType dfun_id)
+ in
-- Check that all the method bindings come from this class
- checkFromThisClass clas op_sel_ids monobinds `thenNF_Tc_`
+ mapTc (addErrTc . badMethodErr clas) bad_bndrs `thenNF_Tc_`
+
+ -- Create dictionary Ids from the specified instance contexts.
+ newDicts origin sc_theta' `thenNF_Tc` \ sc_dicts ->
+ newDicts origin dfun_theta' `thenNF_Tc` \ dfun_arg_dicts ->
+ newDicts origin [mkClassPred clas inst_tys'] `thenNF_Tc` \ [this_dict] ->
tcExtendTyVarEnvForMeths inst_tyvars inst_tyvars' (
- tcExtendGlobalValEnv (catMaybes defm_ids) (
+ tcExtendGlobalValEnv dm_ids (
-- Default-method Ids may be mentioned in synthesised RHSs
- mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys' inst_decl_theta'
- monobinds uprags True)
- (op_sel_ids `zip` defm_ids)
- )) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) ->
+ mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys'
+ dfun_theta'
+ monobinds uprags True)
+ op_items
+ )) `thenTc` \ (method_binds_s, insts_needed_s, meth_insts) ->
-- Deal with SPECIALISE instance pragmas by making them
-- look like SPECIALISE pragmas for the dfun
) `thenTc` \ (prag_binds, prag_lie) ->
-- Check the overloading constraints of the methods and superclasses
-
- -- 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 inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars ->
let
- inst_tyvars_set = mkVarSet zonked_inst_tyvars
-
- (meth_lies, meth_ids) = unzip meth_lies_w_ids
-
-- These insts are in scope; quite a few, eh?
- avail_insts = this_dict `plusLIE`
- dfun_arg_dicts `plusLIE`
- sc_dicts `plusLIE`
- unionManyBags meth_lies
+ avail_insts = [this_dict] ++
+ dfun_arg_dicts ++
+ sc_dicts ++
+ meth_insts
- methods_lie = plusLIEs insts_needed_s
+ methods_lie = plusLIEs insts_needed_s
in
- -- Ditto method bindings
+ -- Simplify the constraints from methods
tcAddErrCtxt methodCtxt (
- tcSimplifyAndCheck
+ tcSimplifyCheck
(ptext SLIT("instance declaration context"))
- inst_tyvars_set -- Local tyvars
+ inst_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.
+ -- Figure out bindings for the superclass context
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` \ _ ->
- -- Ignore the result; we're only doing
- -- this to make sure it can be done.
-
- -- 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
+ tcSimplifyCheck
(ptext SLIT("instance declaration context"))
- inst_tyvars_set
+ inst_tyvars'
dfun_arg_dicts -- NB! Don't include this_dict here, else the sc_dicts
-- get bound by just selecting from this_dict!!
- sc_dicts
- ) `thenTc` \ (const_lie2, lie_binds2) ->
-
+ (mkLIE sc_dicts)
+ ) `thenTc` \ (const_lie2, lie_binds2) ->
+
+ checkSigTyVars inst_tyvars' emptyVarSet `thenNF_Tc` \ zonked_inst_tyvars ->
-- Create the result bindings
let
dict_constr = classDataCon clas
- scs_and_meths = sc_dict_ids ++ meth_ids
+ scs_and_meths = map instToId (sc_dicts ++ meth_insts)
+ this_dict_id = instToId this_dict
+ inlines = unitNameSet (idName dfun_id)
+ -- Always inline the dfun; this is an experimental decision
+ -- because it makes a big performance difference sometimes.
+ -- Often it means we can do the method selection, and then
+ -- inline the method as well. Marcin's idea.
dict_rhs
| null scs_and_meths
-- 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 eRROR_ID) [(unUsgTy . idType) this_dict_id])
- (HsLitOut (HsString msg) stringTy)
+ HsApp (TyApp (HsVar eRROR_ID) [idType this_dict_id])
+ (HsLit (HsString msg))
| otherwise -- The common case
- = foldl HsApp (TyApp (HsVar (dataConId dict_constr)) inst_tys')
- (map HsVar (sc_dict_ids ++ meth_ids))
+ = mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths)
-- 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.mkDataConId code rather
+ -- member) are dealt with by the common MkId.mkDataConWrapId code rather
-- than needing to be repeated here.
where
main_bind
= AbsBinds
zonked_inst_tyvars
- dfun_arg_dicts_ids
+ (map instToId dfun_arg_dicts)
[(inst_tyvars', dfun_id, this_dict_id)]
- emptyNameSet -- No inlines (yet)
+ inlines
(lie_binds1 `AndMonoBinds`
lie_binds2 `AndMonoBinds`
method_binds `AndMonoBinds`
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)
-
-scrutiniseInstanceHead 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.
- --
- (getUnique clas == cCallableClassKey || getUnique clas == cReturnableClassKey)
- && is_alg_tycon_app && not constructors_visible
- = addErrTc (invisibleDataConPrimCCallErr clas first_inst_tau)
-
- | -- CCALL CHECK (b)
- -- A user declaration of a CCallable/CReturnable instance
- -- must be for a "boxed primitive" type.
- (getUnique clas == cCallableClassKey && not (ccallable_type first_inst_tau)) ||
- (getUnique clas == cReturnableClassKey && not (creturnable_type first_inst_tau))
- = addErrTc (nonBoxedPrimCCallErr clas first_inst_tau)
+checkInstValidity dflags theta clas inst_tys
+ | null errs = returnTc ()
+ | otherwise = addErrsTc errs `thenNF_Tc_` failTc
+ where
+ errs = checkInstHead dflags theta clas inst_tys ++
+ [err | pred <- theta, err <- checkInstConstraint dflags pred]
+
+checkInstConstraint dflags pred
+ -- Checks whether a predicate is legal in the
+ -- context of an instance declaration
+ | ok = []
+ | otherwise = [instConstraintErr pred]
+ where
+ ok = inheritablePred pred &&
+ (isTyVarClassPred pred || arbitrary_preds_ok)
- -- 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)
- -- Kind check will have ensured inst_taus is of length 1
+ arbitrary_preds_ok = dopt Opt_AllowUndecidableInstances dflags
- -- Allow anything for AllowUndecidableInstances
- | opt_AllowUndecidableInstances
- = returnNF_Tc ()
+
+checkInstHead dflags theta clas inst_taus
+ | -- CCALL CHECK
+ -- A user declaration of a CCallable/CReturnable instance
+ -- must be for a "boxed primitive" type.
+ (clas `hasKey` cCallableClassKey
+ && not (ccallable_type dflags first_inst_tau))
+ ||
+ (clas `hasKey` cReturnableClassKey
+ && not (creturnable_type first_inst_tau))
+ = [nonBoxedPrimCCallErr clas first_inst_tau]
-- 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
+ = -- GlasgowExts case
+ check_tyvars dflags clas inst_taus ++ check_fundeps dflags theta clas inst_taus
-- 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)" $$
- text "where T is not a synonym, and a,b,c are distinct type variables")
- )
+ | not (length inst_taus == 1 &&
+ maybeToBool maybe_tycon_app && -- Yes, there's a type constuctor
+ not (isSynTyCon tycon) && -- ...but not a synonym
+ all isTyVarTy arg_tys && -- Applied to type variables
+ length (varSetElems (tyVarsOfTypes arg_tys)) == length arg_tys
+ -- This last condition checks that all the type variables are distinct
+ )
+ = [instTypeErr clas inst_taus
+ (text "the instance type must be of form (T a b c)" $$
+ text "where T is not a synonym, and a,b,c are distinct type variables")]
| otherwise
- = returnNF_Tc ()
+ = []
where
(first_inst_tau : _) = inst_taus
maybe_tycon_app = splitTyConApp_maybe first_inst_tau
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
+ ccallable_type dflags ty = isFFIArgumentTy dflags False {- Not safe call -} ty
+ creturnable_type ty = isFFIImportResultTy dflags ty
+
+check_tyvars dflags clas inst_taus
+ -- Check that at least one isn't a type variable
+ -- unless -fallow-undecideable-instances
+ | dopt Opt_AllowUndecidableInstances dflags = []
+ | not (all isTyVarTy inst_taus) = []
+ | otherwise = [the_err]
+ where
+ the_err = instTypeErr clas inst_taus msg
+ msg = ptext SLIT("There must be at least one non-type-variable in the instance head")
+ $$ ptext SLIT("Use -fallow-undecidable-instances to lift this restriction")
+
+check_fundeps dflags theta clas inst_taus
+ | checkInstFDs theta clas inst_taus = []
+ | otherwise = [the_err]
+ where
+ the_err = instTypeErr clas inst_taus msg
+ msg = ptext SLIT("the instance types do not agree with the functional dependencies of the class")
+\end{code}
- constructors_visible = not (null data_cons)
-
--- These conditions come directly from what the DsCCall is capable of.
--- Totally grotesque. Green card should solve this.
+%************************************************************************
+%* *
+\subsection{Error messages}
+%* *
+%************************************************************************
-ccallable_type ty = isUnLiftedType ty || -- Allow CCallable Int# etc
- maybeToBool (maybeBoxedPrimType ty) || -- Ditto Int etc
- ty == stringTy ||
- byte_arr_thing
+\begin{code}
+tcAddDeclCtxt decl thing_inside
+ = tcAddSrcLoc (tcdLoc decl) $
+ tcAddErrCtxt ctxt $
+ thing_inside
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
+ thing = case decl of
+ ClassDecl {} -> "class"
+ TySynonym {} -> "type synonym"
+ TyData {tcdND = NewType} -> "newtype"
+ TyData {tcdND = DataType} -> "data type"
+
+ ctxt = hsep [ptext SLIT("In the"), text thing,
+ ptext SLIT("declaration for"), quotes (ppr (tcdName decl))]
+
+instDeclCtxt inst_ty = ptext SLIT("In the instance declaration for") <+> quotes doc
+ where
+ doc = case inst_ty of
+ HsForAllTy _ _ (HsPredTy pred) -> ppr pred
+ HsPredTy pred -> ppr pred
+ other -> ppr inst_ty -- Don't expect this
\end{code}
\begin{code}
-instConstraintErr clas tys
- = hang (ptext SLIT("Illegal constaint") <+>
- quotes (pprConstraint clas tys) <+>
+instConstraintErr pred
+ = hang (ptext SLIT("Illegal constraint") <+>
+ 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 tc_inst_infos
+ = vcat [ptext SLIT("More than one type pattern for a single generic type constructor:"),
+ nest 4 (vcat (map ppr_inst_ty tc_inst_infos)),
+ ptext SLIT("All the type patterns for a generic type constructor must be identical")
+ ]
+ where
+ ppr_inst_ty (tc,inst) = ppr (simpleInstInfoTy inst)
+
instTypeErr clas tys msg
- = sep [ptext SLIT("Illegal instance declaration for") <+> quotes (pprConstraint clas tys),
+ = sep [ptext SLIT("Illegal instance declaration for") <+>
+ quotes (pprClassPred clas tys),
nest 4 (parens msg)
]
-derivingWhenInstanceExistsErr clas tycon
- = hang (hsep [ptext SLIT("Deriving class"),
- quotes (ppr clas),
- ptext SLIT("type"), quotes (ppr tycon)])
- 4 (ptext SLIT("when an explicit instance exists"))
-
nonBoxedPrimCCallErr clas inst_ty
= hang (ptext SLIT("Unacceptable instance type for ccall-ish class"))
- 4 (hsep [ ptext SLIT("class"), ppr clas, ptext SLIT("type"),
- ppr inst_ty])
-
-{-
- 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 ..)"])
+ 4 (pprClassPred clas [inst_ty])
methodCtxt = ptext SLIT("When checking the methods of an instance declaration")
-superClassCtxt = ptext SLIT("When checking the superclasses of an instance declaration")
+superClassCtxt = ptext SLIT("When checking the super-classes of an instance declaration")
\end{code}