\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
-module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where
+module TcInstDcls ( tcInstDecls1, tcIfaceInstDecls,
+ tcInstDecls2, tcAddDeclCtxt ) where
#include "HsVersions.h"
-import HsSyn ( HsDecl(..), InstDecl(..),
- MonoBinds(..), HsExpr(..), HsLit(..), Sig(..),
- andMonoBindList
+
+import CmdLineOpts ( DynFlag(..) )
+
+import HsSyn ( InstDecl(..), TyClDecl(..), HsType(..),
+ MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..),
+ andMonoBindList, collectMonoBinders,
+ isClassDecl, isSourceInstDecl, toHsType
+ )
+import RnHsSyn ( RenamedHsBinds, RenamedInstDecl,
+ RenamedMonoBinds, RenamedTyClDecl, RenamedHsType,
+ extractHsTyVars, maybeGenericMatch
)
-import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl )
import TcHsSyn ( TcMonoBinds, mkHsConApp )
-
import TcBinds ( tcSpecSigs )
-import TcClassDcl ( tcMethodBind, checkFromThisClass )
-import TcMonad
-import RnMonad ( RnNameSupply, FixityEnv )
-import Inst ( InstOrigin(..),
- newDicts, newClassDicts,
- LIE, emptyLIE, plusLIE, plusLIEs )
-import TcDeriv ( tcDeriving )
-import TcEnv ( ValueEnv, tcExtendGlobalValEnv, tcExtendTyVarEnvForMeths,
- tcAddImportedIdInfo, tcInstId, newDFunName
+import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr )
+import TcRnMonad
+import TcMType ( tcInstType, checkValidTheta, checkValidInstHead, instTypeErr,
+ checkAmbiguity, UserTypeCtxt(..), SourceTyCtxt(..) )
+import TcType ( mkClassPred, mkTyVarTy, tcSplitForAllTys, tyVarsOfType,
+ tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe, mkTyVarTys,
+ TyVarDetails(..)
)
-import TcInstUtil ( InstInfo(..), classDataCon )
-import TcMonoType ( tcHsSigType )
-import TcSimplify ( tcSimplifyAndCheck )
-import TcType ( zonkTcSigTyVars )
-
-import Bag ( emptyBag, unitBag, unionBags, unionManyBags,
- foldBag, Bag
+import Inst ( InstOrigin(..), newMethod, newMethodAtLoc,
+ newDicts, instToId, showLIE )
+import TcDeriv ( tcDeriving )
+import TcEnv ( tcExtendGlobalValEnv,
+ tcLookupClass, tcExtendTyVarEnv2,
+ tcExtendInstEnv, tcExtendLocalInstEnv, tcLookupGlobalId,
+ InstInfo(..), InstBindings(..), pprInstInfo, simpleInstInfoTyCon,
+ simpleInstInfoTy, newDFunName
)
-import CmdLineOpts ( opt_GlasgowExts, opt_AllowUndecidableInstances )
-import Class ( classBigSig )
+import PprType ( pprClassPred )
+import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType )
+import TcUnify ( checkSigTyVars )
+import TcSimplify ( tcSimplifyCheck, tcSimplifyTop )
+import HscTypes ( DFunId )
+import Subst ( mkTyVarSubst, substTheta, substTy )
+import DataCon ( classDataCon )
+import Class ( 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,
- classesToPreds, classesOfPreds,
- unUsgTy, tyVarsOfTypes
+import NameSet
+import Id ( setIdLocalExported )
+import MkId ( mkDictFunId, rUNTIME_ERROR_ID )
+import FunDeps ( checkInstFDs )
+import Generics ( validGenericInstanceType )
+import Name ( getSrcLoc )
+import NameSet ( unitNameSet, emptyNameSet, nameSetToList )
+import TyCon ( TyCon )
+import TysWiredIn ( genericTyCons )
+import SrcLoc ( SrcLoc )
+import Unique ( Uniquable(..) )
+import Util ( lengthExceeds )
+import BasicTypes ( NewOrData(..) )
+import UnicodeUtil ( stringToUtf8 )
+import ErrUtils ( dumpIfSet_dyn )
+import ListSetOps ( Assoc, emptyAssoc, plusAssoc_C, mapAssoc,
+ assocElts, extendAssoc_C, equivClassesByUniq, minusList
)
-import Subst ( mkTopTyVarSubst, substClasses )
-import VarSet ( mkVarSet, varSetElems )
-import TysWiredIn ( isFFIArgumentTy, isFFIResultTy )
-import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey )
+import Maybe ( catMaybes )
+import List ( partition )
import Outputable
+import FastString
\end{code}
Typechecking instance declarations is done in two passes. The first
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]
- -> 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 ->
+tcInstDecls1 -- Deal with both source-code and imported instance decls
+ :: [RenamedTyClDecl] -- For deriving stuff
+ -> [RenamedInstDecl] -- Source code instance decls
+ -> TcM (TcGblEnv, -- The full inst env
+ [InstInfo], -- Source-code instance decls to process;
+ -- contains all dfuns for this module
+ RenamedHsBinds, -- Supporting bindings for derived instances
+ FreeVars) -- And the free vars of the derived code
+
+tcInstDecls1 tycl_decls inst_decls
+ = checkNoErrs $
+ -- Stop if addInstInfos etc discovers any errors
+ -- (they recover, so that we get more than one error each round)
+ let
+ (src_inst_decls, iface_inst_decls) = partition isSourceInstDecl inst_decls
+ in
+
+ -- (0) Deal with the imported instance decls
+ tcIfaceInstDecls iface_inst_decls `thenM` \ imp_dfuns ->
+ tcExtendInstEnv imp_dfuns $
+
+ -- (1) Do the ordinary instance declarations
+ mappM tcLocalInstDecl1 src_inst_decls `thenM` \ local_inst_infos ->
+
let
- decl_inst_info = unionManyBags inst_info_bags
+ local_inst_info = catMaybes local_inst_infos
+ 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 fixs rn_name_supply decl_inst_info
- `thenTc` \ (deriv_inst_info, deriv_binds) ->
+ -- (2) Instances from generic class declarations
+ getGenericInstances clas_decls `thenM` \ generic_inst_info ->
+
+ -- Next, construct the instance environment so far, consisting of
+ -- a) imported instance decls (from this module)
+ -- b) local instance decls
+ -- c) generic instances
+ tcExtendLocalInstEnv local_inst_info $
+ tcExtendLocalInstEnv generic_inst_info $
+
+ -- (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; hence inst_env4
+ tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds, fvs) ->
+ tcExtendLocalInstEnv deriv_inst_info $
+
+ getGblEnv `thenM` \ gbl_env ->
+ returnM (gbl_env,
+ generic_inst_info ++ deriv_inst_info ++ local_inst_info,
+ deriv_binds, fvs)
+\end{code}
+\begin{code}
+tcLocalInstDecl1 :: RenamedInstDecl
+ -> TcM (Maybe InstInfo) -- Nothing if there was an error
+ -- A source-file instance declaration
+ -- Type-check all the stuff before the "where"
+ --
+ -- We 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]
+tcLocalInstDecl1 decl@(InstDecl poly_ty binds uprags Nothing src_loc)
+ = -- Prime error recovery, set source location
+ recoverM (returnM Nothing) $
+ addSrcLoc src_loc $
+ addErrCtxt (instDeclCtxt poly_ty) $
+
+ -- Typecheck the instance type itself. We can't use
+ -- tcHsSigType, because it's not a valid user type.
+ kcHsSigType poly_ty `thenM_`
+ tcHsType poly_ty `thenM` \ poly_ty' ->
let
- full_inst_info = deriv_inst_info `unionBags` decl_inst_info
+ (tyvars, theta, tau) = tcSplitSigmaTy poly_ty'
in
- returnTc (full_inst_info, deriv_binds)
+ checkValidTheta InstThetaCtxt theta `thenM_`
+ checkAmbiguity tyvars theta (tyVarsOfType tau) `thenM_`
+ checkValidInstHead tau `thenM` \ (clas,inst_tys) ->
+ checkTc (checkInstFDs theta clas inst_tys)
+ (instTypeErr (pprClassPred clas inst_tys) msg) `thenM_`
+ newDFunName clas inst_tys src_loc `thenM` \ dfun_name ->
+ returnM (Just (InstInfo { iDFunId = mkDictFunId dfun_name tyvars theta clas inst_tys,
+ iBinds = VanillaInst binds uprags }))
+ where
+ msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class"))
+\end{code}
+Imported instance declarations
-tcInstDecl1 :: Module -> ValueEnv -> RenamedInstDecl -> NF_TcM s (Bag InstInfo)
+\begin{code}
+tcIfaceInstDecls :: [RenamedInstDecl] -> TcM [DFunId]
+-- Deal with the instance decls,
+tcIfaceInstDecls decls = mappM tcIfaceInstDecl decls
+
+tcIfaceInstDecl :: RenamedInstDecl -> TcM DFunId
+ -- An interface-file instance declaration
+ -- Should be in scope by now, because we should
+ -- have sucked in its interface-file definition
+ -- So it will be replete with its unfolding etc
+tcIfaceInstDecl decl@(InstDecl poly_ty binds uprags (Just dfun_name) src_loc)
+ = tcLookupGlobalId dfun_name
+\end{code}
-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"
- tcHsSigType poly_ty `thenTc` \ poly_ty' ->
+%************************************************************************
+%* *
+\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
+ = mappM get_generics class_decls `thenM` \ gen_inst_infos ->
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)
+ gen_inst_info = concat gen_inst_infos
in
+ if null gen_inst_info then
+ returnM []
+ else
+ getDOpts `thenM` \ dflags ->
+ ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances"
+ (vcat (map pprInstInfo gen_inst_info)))
+ `thenM_`
+ returnM gen_inst_info
+
+get_generics decl@(ClassDecl {tcdMeths = Nothing})
+ = returnM [] -- Imported class decls
+
+get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, tcdLoc = loc})
+ | null groups
+ = returnM [] -- The comon case: no generic default methods
+
+ | otherwise -- A source class decl with generic default methods
+ = recoverM (returnM []) $
+ tcAddDeclCtxt decl $
+ tcLookupClass class_name `thenM` \ clas ->
+
+ -- Make an InstInfo out of each group
+ mappM (mkGenericInstance clas loc) groups `thenM` \ 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,
+ group `lengthExceeds` 1]
+ get_uniq (tc,_) = getUnique tc
+ in
+ mappM (addErrTc . dupGenericInsts) bad_groups `thenM_`
+
+ -- 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) `thenM_`
+
+ returnM inst_infos
+
+ where
+ -- Group the declarations by type pattern
+ groups :: [(RenamedHsType, RenamedMonoBinds)]
+ groups = assocElts (getGenericBinds def_methods)
+
- (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))
+---------------------------------
+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
+
+---------------------------------
+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
+ let
+ sig_tvs = map UserTyVar (nameSetToList (extractHsTyVars hs_ty))
+ in
+ tcHsTyVars sig_tvs (kcHsSigType hs_ty) $ \ tyvars ->
+
+ -- Type-check the instance type, and check its form
+ tcHsSigType GenPatCtxt hs_ty `thenM` \ inst_ty ->
+ checkTc (validGenericInstanceType inst_ty)
+ (badGenericInstanceType binds) `thenM_`
+
+ -- Make the dictionary function.
+ newDFunName clas [inst_ty] loc `thenM` \ dfun_name ->
+ let
+ inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars]
+ dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty]
+ in
+
+ returnM (InstInfo { iDFunId = dfun_id, iBinds = VanillaInst binds [] })
\end{code}
%************************************************************************
\begin{code}
-tcInstDecls2 :: Bag InstInfo
- -> NF_TcM s (LIE, TcMonoBinds)
-
+tcInstDecls2 :: [InstInfo] -> TcM TcMonoBinds
tcInstDecls2 inst_decls
- = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyMonoBinds)) inst_decls
- where
- combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
- tc2 `thenNF_Tc` \ (lie2, binds2) ->
- returnNF_Tc (lie1 `plusLIE` lie2,
- binds1 `AndMonoBinds` binds2)
+ = mappM tcInstDecl2 inst_decls `thenM` \ binds_s ->
+ returnM (andMonoBindList binds_s)
\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)
+\begin{code}
+tcInstDecl2 :: InstInfo -> TcM TcMonoBinds
- | otherwise
+tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds })
= -- Prime error recovery
- recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
- tcAddSrcLoc locn $
-
- -- Check that all the method bindings come from this class
- checkFromThisClass clas monobinds `thenNF_Tc_`
+ recoverM (returnM EmptyMonoBinds) $
+ addSrcLoc (getSrcLoc dfun_id) $
+ addErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $
+ let
+ inst_ty = idType dfun_id
+ (inst_tyvars, _) = tcSplitForAllTys inst_ty
+ -- The tyvars of the instance decl scope over the 'where' part
+ -- Those tyvars are inside the dfun_id's type, which is a bit
+ -- bizarre, but OK so long as you realise it!
+ in
-- Instantiate the instance decl with tc-style type variables
- tcInstId dfun_id `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') ->
+ tcInstType InstTv inst_ty `thenM` \ (inst_tyvars', dfun_theta', inst_head') ->
let
- (clas, inst_tys') = expectJust "tcInstDecl2" (splitDictTy_maybe dict_ty')
-
- origin = InstanceDeclOrigin
-
+ Just pred = tcSplitPredTy_maybe inst_head'
+ (clas, inst_tys') = getClassPredTys pred
(class_tyvars, sc_theta, _, op_items) = classBigSig clas
- 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
-
- -- Instantiate the super-class context with inst_tys
- sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys') sc_theta
+ -- Instantiate the super-class context with inst_tys
+ sc_theta' = substTheta (mkTyVarSubst class_tyvars inst_tys') sc_theta
+ origin = InstanceDeclOrigin
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 (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 = [SpecSig (idName dfun_id) ty loc | SpecInstSig ty loc <- uprags]
+ newDicts origin sc_theta' `thenM` \ sc_dicts ->
+ newDicts origin dfun_theta' `thenM` \ dfun_arg_dicts ->
+ newDicts origin [pred] `thenM` \ [this_dict] ->
+ -- Default-method Ids may be mentioned in synthesised RHSs,
+ -- but they'll already be in the environment.
+
+ ------------------
+ -- Typecheck the methods
+ let -- These insts are in scope; quite a few, eh?
+ avail_insts = [this_dict] ++ dfun_arg_dicts ++ sc_dicts
in
- tcExtendGlobalValEnv [dfun_id] (
- tcSpecSigs dfun_prags
- ) `thenTc` \ (prag_binds, prag_lie) ->
+ tcMethods clas inst_tyvars inst_tyvars'
+ dfun_theta' inst_tys' avail_insts
+ op_items binds `thenM` \ (meth_ids, meth_binds) ->
- -- Check the overloading constraints of the methods and superclasses
+ -- Figure out bindings for the superclass context
+ tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts
+ `thenM` \ (zonked_inst_tyvars, sc_binds_inner, sc_binds_outer) ->
- -- 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 ->
+ -- Deal with 'SPECIALISE instance' pragmas by making them
+ -- look like SPECIALISE pragmas for the dfun
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
-
- methods_lie = plusLIEs insts_needed_s
+ uprags = case binds of
+ VanillaInst _ uprags -> uprags
+ other -> []
+ spec_prags = [ SpecSig (idName dfun_id) ty loc
+ | SpecInstSig ty loc <- uprags ]
+ xtve = inst_tyvars `zip` inst_tyvars'
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.
- 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
- (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
- ) `thenTc` \ (const_lie2, lie_binds2) ->
-
+ tcExtendGlobalValEnv [dfun_id] (
+ tcExtendTyVarEnv2 xtve $
+ tcSpecSigs spec_prags
+ ) `thenM` \ prag_binds ->
-- Create the result bindings
let
+ local_dfun_id = setIdLocalExported dfun_id
+ -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId
+
dict_constr = classDataCon clas
- scs_and_meths = sc_dict_ids ++ meth_ids
+ scs_and_meths = map instToId sc_dicts ++ meth_ids
+ this_dict_id = instToId this_dict
+ inlines | null dfun_arg_dicts = emptyNameSet
+ | otherwise = 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; see comments below.
+ --
+ -- BUT: don't inline it if it's a constant dictionary;
+ -- we'll get all the benefit without inlining, and we get
+ -- a **lot** of code duplication if we inline it
+ --
+ -- See Note [Inline dfuns] below
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])
- (HsLit (HsString msg))
+ HsApp (TyApp (HsVar rUNTIME_ERROR_ID) [idType this_dict_id])
+ (HsLit (HsStringPrim (mkFastString (stringToUtf8 msg))))
| otherwise -- The common case
- = mkHsConApp 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
-- 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 = andMonoBindList method_binds_s
-
- main_bind
- = AbsBinds
- zonked_inst_tyvars
- dfun_arg_dicts_ids
- [(inst_tyvars', dfun_id, this_dict_id)]
- emptyNameSet -- No inlines (yet)
- (lie_binds1 `AndMonoBinds`
- lie_binds2 `AndMonoBinds`
- method_binds `AndMonoBinds`
- dict_bind)
+ msg = "Compiler error: bad dictionary " ++ showSDoc (ppr clas)
+
+ dict_bind = VarMonoBind this_dict_id dict_rhs
+ all_binds = sc_binds_inner `AndMonoBinds` meth_binds `AndMonoBinds` dict_bind
+
+ main_bind = AbsBinds
+ zonked_inst_tyvars
+ (map instToId dfun_arg_dicts)
+ [(inst_tyvars', local_dfun_id, this_dict_id)]
+ inlines all_binds
+ in
+ showLIE "instance" `thenM_`
+ returnM (main_bind `AndMonoBinds` prag_binds `AndMonoBinds` sc_binds_outer)
+
+
+tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys'
+ avail_insts op_items (VanillaInst monobinds uprags)
+ = -- Check that all the method bindings come from this class
+ let
+ sel_names = [idName sel_id | (sel_id, _) <- op_items]
+ bad_bndrs = collectMonoBinders monobinds `minusList` sel_names
in
- returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie,
- main_bind `AndMonoBinds` prag_binds)
+ mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_`
+
+ -- Make the method bindings
+ mapAndUnzipM do_one op_items `thenM` \ (meth_ids, meth_binds_s) ->
+
+ returnM (meth_ids, andMonoBindList meth_binds_s)
+
+ where
+ xtve = inst_tyvars `zip` inst_tyvars'
+ do_one op_item
+ = mkMethodBind InstanceDeclOrigin clas
+ inst_tys' monobinds op_item `thenM` \ (meth_inst, meth_info) ->
+ tcMethodBind xtve inst_tyvars' dfun_theta'
+ avail_insts uprags meth_info `thenM` \ meth_bind ->
+ -- Could add meth_insts to avail_insts, but not worth the bother
+ returnM (instToId meth_inst, meth_bind)
+
+-- Derived newtype instances
+tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys'
+ avail_insts op_items (NewTypeDerived rep_tys)
+ = getInstLoc InstanceDeclOrigin `thenM` \ inst_loc ->
+ getLIE (mapAndUnzipM (do_one inst_loc) op_items) `thenM` \ ((meth_ids, meth_binds), lie) ->
+
+ tcSimplifyCheck
+ (ptext SLIT("newtype derived instance"))
+ inst_tyvars' avail_insts lie `thenM` \ lie_binds ->
+
+ -- I don't think we have to do the checkSigTyVars thing
+
+ returnM (meth_ids, lie_binds `AndMonoBinds` andMonoBindList meth_binds)
+
+ where
+ do_one inst_loc (sel_id, _)
+ = newMethodAtLoc inst_loc sel_id inst_tys' `thenM` \ meth_inst ->
+ -- Like in mkMethodBind
+ newMethod InstanceDeclOrigin sel_id rep_tys' `thenM` \ rhs_id ->
+ -- The binding is like "op @ NewTy = op @ RepTy"
+ let
+ meth_id = instToId meth_inst
+ in
+ return (meth_id, VarMonoBind meth_id (HsVar rhs_id))
+
+ -- Instantiate rep_tys with the relevant type variables
+ rep_tys' = map (substTy subst) rep_tys
+ subst = mkTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars')
\end{code}
+Note: [Superclass loops]
+~~~~~~~~~~~~~~~~~~~~~~~~~
+We have to be very, very careful when generating superclasses, lest we
+accidentally build a loop. Here's an example:
-%************************************************************************
-%* *
-\subsection{Checking for a decent instance type}
-%* *
-%************************************************************************
+ class S a
+
+ class S a => C a where { opc :: a -> a }
+ class S b => D b where { opd :: b -> b }
+
+ instance C Int where
+ opc = opd
+
+ instance D Int where
+ opd = opc
+
+From (instance C Int) we get the constraint set {ds1:S Int, dd:D Int}
+Simplifying, we may well get:
+ $dfCInt = :C ds1 (opd dd)
+ dd = $dfDInt
+ ds1 = $p1 dd
+Notice that we spot that we can extract ds1 from dd.
-@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints:
-it must normally look like: @instance Foo (Tycon a b c ...) ...@
+Alas! Alack! We can do the same for (instance D Int):
-The exceptions to this syntactic checking: (1)~if the @GlasgowExts@
-flag is on, or (2)~the instance is imported (they must have been
-compiled elsewhere). In these cases, we let them go through anyway.
+ $dfDInt = :D ds2 (opc dc)
+ dc = $dfCInt
+ ds2 = $p1 dc
-We can also have instances for functions: @instance Foo (a -> b) ...@.
+And now we've defined the superclass in terms of itself.
+
+
+Solution: treat the superclass context separately, and simplify it
+all the way down to nothing on its own. Don't toss any 'free' parts
+out to be simplified together with other bits of context.
+Hence the tcSimplifyTop below.
+
+At a more basic level, don't include this_dict in the context wrt
+which we simplify sc_dicts, else sc_dicts get bound by just selecting
+from this_dict!!
\begin{code}
-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.
- (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)
- = 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 (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 ()
+tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts
+ = addErrCtxt superClassCtxt $
+ getLIE (tcSimplifyCheck doc inst_tyvars'
+ dfun_arg_dicts
+ sc_dicts) `thenM` \ (sc_binds1, sc_lie) ->
+
+ -- It's possible that the superclass stuff might have done unification
+ checkSigTyVars inst_tyvars' `thenM` \ zonked_inst_tyvars ->
+
+ -- We must simplify this all the way down
+ -- lest we build superclass loops
+ -- See Note [Superclass loops] above
+ tcSimplifyTop sc_lie `thenM` \ sc_binds2 ->
+
+ returnM (zonked_inst_tyvars, sc_binds1, sc_binds2)
where
- (first_inst_tau : _) = inst_taus
-
- -- Stuff for algebraic or -> type
- 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
- Just (alg_tycon, _, _) = alg_tycon_app_maybe
-
-ccallable_type ty = isFFIArgumentTy False {- Not safe call -} ty
-creturnable_type ty = isFFIResultTy ty
+ doc = ptext SLIT("instance declaration superclass context")
\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)
- ]
-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"))
+ ------------------------------
+ [Inline dfuns] Inlining dfuns unconditionally
+ ------------------------------
+
+The code above unconditionally inlines dict funs. Here's why.
+Consider this program:
+
+ test :: Int -> Int -> Bool
+ test x y = (x,y) == (y,x) || test y x
+ -- Recursive to avoid making it inline.
+
+This needs the (Eq (Int,Int)) instance. If we inline that dfun
+the code we end up with is good:
+
+ Test.$wtest =
+ \r -> case ==# [ww ww1] of wild {
+ PrelBase.False -> Test.$wtest ww1 ww;
+ PrelBase.True ->
+ case ==# [ww1 ww] of wild1 {
+ PrelBase.False -> Test.$wtest ww1 ww;
+ PrelBase.True -> PrelBase.True [];
+ };
+ };
+ Test.test = \r [w w1]
+ case w of w2 {
+ PrelBase.I# ww ->
+ case w1 of w3 { PrelBase.I# ww1 -> Test.$wtest ww ww1; };
+ };
+
+If we don't inline the dfun, the code is not nearly as good:
+
+ (==) = case PrelTup.$fEq(,) PrelBase.$fEqInt PrelBase.$fEqInt of tpl {
+ PrelBase.:DEq tpl1 tpl2 -> tpl2;
+ };
+
+ Test.$wtest =
+ \r [ww ww1]
+ let { y = PrelBase.I#! [ww1]; } in
+ let { x = PrelBase.I#! [ww]; } in
+ let { sat_slx = PrelTup.(,)! [y x]; } in
+ let { sat_sly = PrelTup.(,)! [x y];
+ } in
+ case == sat_sly sat_slx of wild {
+ PrelBase.False -> Test.$wtest ww1 ww;
+ PrelBase.True -> PrelBase.True [];
+ };
+
+ Test.test =
+ \r [w w1]
+ case w of w2 {
+ PrelBase.I# ww ->
+ case w1 of w3 { PrelBase.I# ww1 -> Test.$wtest ww ww1; };
+ };
+
+Why doesn't GHC inline $fEq? Because it looks big:
+
+ PrelTup.zdfEqZ1T{-rcX-}
+ = \ @ a{-reT-} :: * @ b{-reS-} :: *
+ zddEq{-rf6-} _Ks :: {PrelBase.Eq{-23-} a{-reT-}}
+ zddEq1{-rf7-} _Ks :: {PrelBase.Eq{-23-} b{-reS-}} ->
+ let {
+ zeze{-rf0-} _Kl :: (b{-reS-} -> b{-reS-} -> PrelBase.Bool{-3c-})
+ zeze{-rf0-} = PrelBase.zeze{-01L-}@ b{-reS-} zddEq1{-rf7-} } in
+ let {
+ zeze1{-rf3-} _Kl :: (a{-reT-} -> a{-reT-} -> PrelBase.Bool{-3c-})
+ zeze1{-rf3-} = PrelBase.zeze{-01L-} @ a{-reT-} zddEq{-rf6-} } in
+ let {
+ zeze2{-reN-} :: ((a{-reT-}, b{-reS-}) -> (a{-reT-}, b{-reS-})-> PrelBase.Bool{-3c-})
+ zeze2{-reN-} = \ ds{-rf5-} _Ks :: (a{-reT-}, b{-reS-})
+ ds1{-rf4-} _Ks :: (a{-reT-}, b{-reS-}) ->
+ case ds{-rf5-}
+ of wild{-reW-} _Kd { (a1{-rf2-} _Ks, a2{-reZ-} _Ks) ->
+ case ds1{-rf4-}
+ of wild1{-reX-} _Kd { (b1{-rf1-} _Ks, b2{-reY-} _Ks) ->
+ PrelBase.zaza{-r4e-}
+ (zeze1{-rf3-} a1{-rf2-} b1{-rf1-})
+ (zeze{-rf0-} a2{-reZ-} b2{-reY-})
+ }
+ } } in
+ let {
+ a1{-reR-} :: ((a{-reT-}, b{-reS-})-> (a{-reT-}, b{-reS-})-> PrelBase.Bool{-3c-})
+ a1{-reR-} = \ a2{-reV-} _Ks :: (a{-reT-}, b{-reS-})
+ b1{-reU-} _Ks :: (a{-reT-}, b{-reS-}) ->
+ PrelBase.not{-r6I-} (zeze2{-reN-} a2{-reV-} b1{-reU-})
+ } in
+ PrelBase.zdwZCDEq{-r8J-} @ (a{-reT-}, b{-reS-}) a1{-reR-} zeze2{-reN-})
+
+and it's not as bad as it seems, because it's further dramatically
+simplified: only zeze2 is extracted and its body is simplified.
+
+
+%************************************************************************
+%* *
+\subsection{Error messages}
+%* *
+%************************************************************************
+
+\begin{code}
+tcAddDeclCtxt decl thing_inside
+ = addSrcLoc (tcdLoc decl) $
+ addErrCtxt ctxt $
+ thing_inside
+ where
+ 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}
-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])
+\begin{code}
+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)
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}
projects / ghc-hetmet.git / blobdiff