\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
-module TcInstDcls ( tcInstDecls1, tcInstDecls2, tcAddDeclCtxt ) where
+module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where
#include "HsVersions.h"
-
-import CmdLineOpts ( DynFlag(..), dopt )
-
-import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..),
- MonoBinds(..), HsExpr(..), HsLit(..), Sig(..),
- andMonoBindList, collectMonoBinders, isClassDecl
- )
-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, badMethodErr )
-import TcMonad
-import Inst ( InstOrigin(..),
- newDicts, newClassDicts,
- LIE, emptyLIE, plusLIE, plusLIEs )
+import HsSyn
+import TcBinds ( mkPragFun, tcPrags, badBootDeclErr )
+import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr,
+ tcClassDecl2, getGenericInstances )
+import TcRnMonad
+import TcMType ( tcSkolSigType, checkValidTheta, checkValidInstHead,
+ checkInstTermination, instTypeErr,
+ checkAmbiguity, SourceTyCtxt(..) )
+import TcType ( mkClassPred, tyVarsOfType,
+ tcSplitSigmaTy, tcSplitDFunHead, mkTyVarTys,
+ SkolemInfo(InstSkol), tcSplitDFunTy, pprClassPred )
+import Inst ( tcInstClassOp, newDicts, instToId, showLIE,
+ getOverlapFlag, tcExtendLocalInstEnv )
+import InstEnv ( mkLocalInstance, instanceDFunId )
import TcDeriv ( tcDeriving )
-import TcEnv ( TcEnv, tcExtendGlobalValEnv,
- tcExtendTyVarEnvForMeths, TyThing (..),
- tcAddImportedIdInfo, tcInstId, tcLookupClass,
- newDFunName, tcExtendTyVarEnv
- )
-import InstEnv ( InstInfo(..), InstEnv, pprInstInfo, classDataCon,
- simpleInstInfoTyCon, simpleInstInfoTy, isLocalInst,
- extendInstEnv )
-import TcMonoType ( tcTyVars, tcHsSigType, tcHsType, kcHsSigType )
-import TcSimplify ( tcSimplifyAndCheck )
-import TcType ( zonkTcSigTyVars )
-import HscTypes ( PersistentCompilerState(..), HomeSymbolTable, DFunId,
- ModDetails(..) )
-
-import Bag ( emptyBag, unitBag, unionBags, unionManyBags,
- foldBag, Bag, listToBag
+import TcEnv ( InstInfo(..), InstBindings(..),
+ newDFunName, tcExtendIdEnv
)
-import Class ( Class, DefMeth(..), classBigSig )
-import Var ( idName, idType )
-import Maybes ( maybeToBool, expectJust )
-import MkId ( mkDictFunId )
-import Generics ( validGenericInstanceType )
-import Module ( Module, foldModuleEnv )
-import Name ( isLocallyDefined )
-import NameSet ( emptyNameSet, nameSetToList )
-import PrelInfo ( eRROR_ID )
-import PprType ( pprConstraint, pprPred )
-import TyCon ( TyCon, isSynTyCon, tyConDerivings )
-import Type ( mkTyVarTys, splitSigmaTy, isTyVarTy,
- splitTyConApp_maybe, splitDictTy_maybe,
- splitAlgTyConApp_maybe, classesToPreds, classesOfPreds,
- unUsgTy, tyVarsOfTypes, mkClassPred, mkTyVarTy,
- getClassTys_maybe
- )
-import Subst ( mkTopTyVarSubst, substClasses, substTheta )
-import VarSet ( mkVarSet, varSetElems )
-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 TcHsType ( kcHsSigType, tcHsKindedType )
+import TcUnify ( checkSigTyVars )
+import TcSimplify ( tcSimplifyCheck, tcSimplifySuperClasses )
+import Type ( zipOpenTvSubst, substTheta, substTys )
+import DataCon ( classDataCon )
+import Class ( classBigSig )
+import Var ( Id, idName, idType )
+import MkId ( mkDictFunId, rUNTIME_ERROR_ID )
+import FunDeps ( checkInstFDs )
+import Name ( Name, getSrcLoc )
+import Maybe ( catMaybes )
+import SrcLoc ( srcLocSpan, unLoc, noLoc, Located(..), srcSpanStart )
+import ListSetOps ( minusList )
import Outputable
+import Bag
+import BasicTypes ( Activation( AlwaysActive ), InlineSpec(..) )
+import FastString
\end{code}
Typechecking instance declarations is done in two passes. The first
Gather up the instance declarations from their various sources
\begin{code}
-tcInstDecls1 :: PersistentCompilerState
- -> HomeSymbolTable -- Contains instances
- -> TcEnv -- Contains IdInfo for dfun ids
- -> Module -- Module for deriving
- -> [TyCon]
- -> [RenamedHsDecl]
- -> TcM (PersistentCompilerState, InstEnv, [InstInfo], RenamedHsBinds)
-
-tcInstDecls1 pcs hst unf_env 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
+tcInstDecls1 -- Deal with both source-code and imported instance decls
+ :: [LTyClDecl Name] -- For deriving stuff
+ -> [LInstDecl Name] -- Source code instance decls
+ -> TcM (TcGblEnv, -- The full inst env
+ [InstInfo], -- Source-code instance decls to process;
+ -- contains all dfuns for this module
+ HsValBinds Name) -- Supporting bindings for derived instances
+
+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)
+
-- (1) Do the ordinary instance declarations
- mapNF_Tc (tcInstDecl1 mod unf_env) inst_decls `thenNF_Tc` \ inst_infos ->
+ mappM tcLocalInstDecl1 inst_decls `thenM` \ local_inst_infos ->
+ let
+ local_inst_info = catMaybes local_inst_infos
+ clas_decls = filter (isClassDecl.unLoc) tycl_decls
+ in
-- (2) Instances from generic class declarations
- getGenericInstances mod clas_decls `thenTc` \ generic_inst_info ->
+ getGenericInstances clas_decls `thenM` \ 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 ->
+ -- a) local instance decls
+ -- b) generic instances
+ addInsts local_inst_info $
+ addInsts 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; hecne inst_env4
- tcDeriving (pcs_PRS pcs) mod inst_env4 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
-
+ -- needs to know about all the instances possible; hence inst_env4
+ tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds) ->
+ addInsts deriv_inst_info $
+
+ getGblEnv `thenM` \ gbl_env ->
+ returnM (gbl_env,
+ generic_inst_info ++ deriv_inst_info ++ local_inst_info,
+ deriv_binds)
+
+addInsts :: [InstInfo] -> TcM a -> TcM a
+addInsts infos thing_inside
+ = tcExtendLocalInstEnv (map iSpec infos) thing_inside
\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 []) $
- tcAddSrcLoc src_loc $
-
+tcLocalInstDecl1 :: LInstDecl Name
+ -> TcM (Maybe InstInfo) -- Nothing if there was an error
+ -- A source-file instance declaration
-- Type-check all the stuff before the "where"
- tcHsSigType poly_ty `thenTc` \ poly_ty' ->
+ --
+ -- We check for respectable instance type, and context
+tcLocalInstDecl1 decl@(L loc (InstDecl poly_ty binds uprags))
+ = -- Prime error recovery, set source location
+ recoverM (returnM Nothing) $
+ setSrcSpan loc $
+ addErrCtxt (instDeclCtxt1 poly_ty) $
+
+ -- Typecheck the instance type itself. We can't use
+ -- tcHsSigType, because it's not a valid user type.
+ kcHsSigType poly_ty `thenM` \ kinded_ty ->
+ tcHsKindedType kinded_ty `thenM` \ poly_ty' ->
let
- (tyvars, theta, dict_ty) = splitSigmaTy poly_ty'
- (clas, inst_tys) = case splitDictTy_maybe dict_ty of
- Just ct -> ct
- Nothing -> pprPanic "tcInstDecl1" (ppr poly_ty)
+ (tyvars, theta, tau) = tcSplitSigmaTy poly_ty'
in
-
- (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 theta `thenNF_Tc_`
-
- -- Make the dfun id and return it
- newDFunName mod clas inst_tys src_loc `thenNF_Tc` \ dfun_name ->
- returnNF_Tc (True, mkDictFunId dfun_name clas tyvars inst_tys theta)
-
- Just dfun_name -> -- An interface-file instance declaration
- -- 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 pragmas
- 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
+ checkValidTheta InstThetaCtxt theta `thenM_`
+ checkAmbiguity tyvars theta (tyVarsOfType tau) `thenM_`
+ checkValidInstHead tau `thenM` \ (clas,inst_tys) ->
+ checkInstTermination theta inst_tys `thenM_`
+ checkTc (checkInstFDs theta clas inst_tys)
+ (instTypeErr (pprClassPred clas inst_tys) msg) `thenM_`
+ newDFunName clas inst_tys (srcSpanStart loc) `thenM` \ dfun_name ->
+ getOverlapFlag `thenM` \ overlap_flag ->
+ let dfun = mkDictFunId dfun_name tyvars theta clas inst_tys
+ ispec = mkLocalInstance dfun overlap_flag
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)
+ tcIsHsBoot `thenM` \ is_boot ->
+ checkTc (not is_boot || (isEmptyLHsBinds binds && null uprags))
+ badBootDeclErr `thenM_`
-getGenericBinds (FunMonoBind id infixop matches loc)
- = mapAssoc wrap (foldr add emptyAssoc matches)
+ returnM (Just (InstInfo { iSpec = ispec, iBinds = VanillaInst binds uprags }))
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 = [] })
+ msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class"))
\end{code}
%************************************************************************
\begin{code}
-tcInstDecls2 :: [InstInfo]
- -> NF_TcM (LIE, TcMonoBinds)
-
-tcInstDecls2 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) ->
- returnNF_Tc (lie1 `plusLIE` lie2,
- binds1 `AndMonoBinds` binds2)
+tcInstDecls2 :: [LTyClDecl Name] -> [InstInfo]
+ -> TcM (LHsBinds Id, TcLclEnv)
+-- (a) From each class declaration,
+-- generate any default-method bindings
+-- (b) From each instance decl
+-- generate the dfun binding
+
+tcInstDecls2 tycl_decls inst_decls
+ = do { -- (a) Default methods from class decls
+ (dm_binds_s, dm_ids_s) <- mapAndUnzipM tcClassDecl2 $
+ filter (isClassDecl.unLoc) tycl_decls
+ ; tcExtendIdEnv (concat dm_ids_s) $ do
+
+ -- (b) instance declarations
+ ; inst_binds_s <- mappM tcInstDecl2 inst_decls
+
+ -- Done
+ ; let binds = unionManyBags dm_binds_s `unionBags`
+ unionManyBags inst_binds_s
+ ; tcl_env <- getLclEnv -- Default method Ids in here
+ ; returnM (binds, tcl_env) }
\end{code}
======= New documentation starts here (Sept 92) ==============
First comes the easy case of a non-local instance decl.
-\begin{code}
-tcInstDecl2 :: InstInfo -> NF_TcM (LIE, TcMonoBinds)
-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)
-
- | otherwise
- = -- Prime error recovery
- recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
- tcAddSrcLoc locn $
+\begin{code}
+tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id)
- -- Instantiate the instance decl with tc-style type variables
- tcInstId dfun_id `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') ->
+tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = binds })
+ = let
+ dfun_id = instanceDFunId ispec
+ rigid_info = InstSkol dfun_id
+ inst_ty = idType dfun_id
+ in
+ -- Prime error recovery
+ recoverM (returnM emptyLHsBinds) $
+ setSrcSpan (srcLocSpan (getSrcLoc dfun_id)) $
+ addErrCtxt (instDeclCtxt2 (idType dfun_id)) $
+
+ -- Instantiate the instance decl with skolem constants
+ tcSkolSigType rigid_info inst_ty `thenM` \ (inst_tyvars', dfun_theta', inst_head') ->
+ -- These inst_tyvars' 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!
let
- (clas, inst_tys') = expectJust "tcInstDecl2" (splitDictTy_maybe dict_ty')
- origin = InstanceDeclOrigin
-
+ (clas, inst_tys') = tcSplitDFunHead inst_head'
(class_tyvars, sc_theta, _, op_items) = 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
- 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
+ sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta
+ origin = SigOrigin rigid_info
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) ->
- 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'
- 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 InstScOrigin sc_theta' `thenM` \ sc_dicts ->
+ newDicts origin dfun_theta' `thenM` \ dfun_arg_dicts ->
+ newDicts origin [mkClassPred clas inst_tys'] `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) ->
-
- -- 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 before passing them to tcSimplifyAndCheck
- zonkTcSigTyVars inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars ->
+ tcMethods origin clas inst_tyvars'
+ dfun_theta' inst_tys' avail_insts
+ op_items binds `thenM` \ (meth_ids, meth_binds) ->
+
+ -- Figure out bindings for the superclass context
+ -- Don't include this_dict in the 'givens', else
+ -- sc_dicts get bound by just selecting from this_dict!!
+ addErrCtxt superClassCtxt
+ (tcSimplifySuperClasses inst_tyvars'
+ dfun_arg_dicts
+ sc_dicts) `thenM` \ sc_binds ->
+
+ -- It's possible that the superclass stuff might unified one
+ -- of the inst_tyavars' with something in the envt
+ checkSigTyVars inst_tyvars' `thenM_`
+
+ -- Deal with 'SPECIALISE instance' pragmas
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
+ specs = case binds of
+ VanillaInst _ prags -> filter isSpecInstLSig prags
+ other -> []
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) ->
+ tcPrags dfun_id specs `thenM` \ prags ->
- -- 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) ->
-
-
-- 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_ids
+ this_dict_id = instToId this_dict
+ inline_prag | null dfun_arg_dicts = []
+ | otherwise = [InlinePrag (Inline AlwaysActive True)]
+ -- 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
- = -- Blatant special case for CCallable, CReturnable
- -- If the dictionary is empty then we should never
- -- select anything from it, so we make its RHS just
- -- 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))
-
- | 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 = noLoc (VarBind this_dict_id dict_rhs)
+ all_binds = dict_bind `consBag` (sc_binds `unionBags` meth_binds)
+
+ main_bind = noLoc $ AbsBinds
+ inst_tyvars'
+ (map instToId dfun_arg_dicts)
+ [(inst_tyvars', dfun_id, this_dict_id,
+ inline_prag ++ prags)]
+ all_binds
in
- returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie,
- main_bind `AndMonoBinds` prag_binds)
-\end{code}
+ showLIE (text "instance") `thenM_`
+ returnM (unitBag main_bind)
-%************************************************************************
-%* *
-\subsection{Checking for a decent instance type}
-%* *
-%************************************************************************
+tcMethods origin clas 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 = collectHsBindBinders monobinds `minusList` sel_names
+ in
+ mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_`
+
+ -- Make the method bindings
+ let
+ mk_method_bind = mkMethodBind origin clas inst_tys' monobinds
+ in
+ mapAndUnzipM mk_method_bind op_items `thenM` \ (meth_insts, meth_infos) ->
+
+ -- And type check them
+ -- It's really worth making meth_insts available to the tcMethodBind
+ -- Consider instance Monad (ST s) where
+ -- {-# INLINE (>>) #-}
+ -- (>>) = ...(>>=)...
+ -- If we don't include meth_insts, we end up with bindings like this:
+ -- rec { dict = MkD then bind ...
+ -- then = inline_me (... (GHC.Base.>>= dict) ...)
+ -- bind = ... }
+ -- The trouble is that (a) 'then' and 'dict' are mutually recursive,
+ -- and (b) the inline_me prevents us inlining the >>= selector, which
+ -- would unravel the loop. Result: (>>) ends up as a loop breaker, and
+ -- is not inlined across modules. Rather ironic since this does not
+ -- happen without the INLINE pragma!
+ --
+ -- Solution: make meth_insts available, so that 'then' refers directly
+ -- to the local 'bind' rather than going via the dictionary.
+ --
+ -- BUT WATCH OUT! If the method type mentions the class variable, then
+ -- this optimisation is not right. Consider
+ -- class C a where
+ -- op :: Eq a => a
+ --
+ -- instance C Int where
+ -- op = op
+ -- The occurrence of 'op' on the rhs gives rise to a constraint
+ -- op at Int
+ -- The trouble is that the 'meth_inst' for op, which is 'available', also
+ -- looks like 'op at Int'. But they are not the same.
+ let
+ prag_fn = mkPragFun uprags
+ all_insts = avail_insts ++ catMaybes meth_insts
+ tc_method_bind = tcMethodBind inst_tyvars' dfun_theta' all_insts prag_fn
+ meth_ids = [meth_id | (_,meth_id,_) <- meth_infos]
+ in
+
+ mapM tc_method_bind meth_infos `thenM` \ meth_binds_s ->
+
+ returnM (meth_ids, unionManyBags meth_binds_s)
-@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints:
-it must normally look like: @instance Foo (Tycon a b c ...) ...@
-The exceptions to this syntactic checking: (1)~if the @GlasgowExts@
-flag is on, or (2)~the instance is imported (they must have been
-compiled elsewhere). In these cases, we let them go through anyway.
+-- Derived newtype instances
+tcMethods origin clas inst_tyvars' dfun_theta' inst_tys'
+ avail_insts op_items (NewTypeDerived rep_tys)
+ = getInstLoc origin `thenM` \ inst_loc ->
+ mapAndUnzip3M (do_one inst_loc) op_items `thenM` \ (meth_ids, meth_binds, rhs_insts) ->
+
+ tcSimplifyCheck
+ (ptext SLIT("newtype derived instance"))
+ inst_tyvars' avail_insts rhs_insts `thenM` \ lie_binds ->
-We can also have instances for functions: @instance Foo (a -> b) ...@.
+ -- I don't think we have to do the checkSigTyVars thing
-\begin{code}
-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
- = 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 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)
- -- Kind check will have ensured inst_taus is of length 1
-
- -- Allow anything for AllowUndecidableInstances
- | dopt Opt_AllowUndecidableInstances dflags
- -> returnNF_Tc ()
-
- -- If GlasgowExts then check at least one isn't a type variable
- | 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 ()
+ returnM (meth_ids, lie_binds `unionBags` listToBag meth_binds)
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 dflags ty = isFFIArgumentTy dflags False {- Not safe call -} ty
- creturnable_type ty = isFFIResultTy ty
+ do_one inst_loc (sel_id, _)
+ = -- The binding is like "op @ NewTy = op @ RepTy"
+ -- Make the *binder*, like in mkMethodBind
+ tcInstClassOp inst_loc sel_id inst_tys' `thenM` \ meth_inst ->
+
+ -- Make the *occurrence on the rhs*
+ tcInstClassOp inst_loc sel_id rep_tys' `thenM` \ rhs_inst ->
+ let
+ meth_id = instToId meth_inst
+ in
+ return (meth_id, noLoc (VarBind meth_id (nlHsVar (instToId rhs_inst))), rhs_inst)
+
+ -- Instantiate rep_tys with the relevant type variables
+ -- This looks a bit odd, because inst_tyvars' are the skolemised version
+ -- of the type variables in the instance declaration; but rep_tys doesn't
+ -- have the skolemised version, so we substitute them in here
+ rep_tys' = substTys subst rep_tys
+ subst = zipOpenTvSubst inst_tyvars' (mkTyVarTys inst_tyvars')
\end{code}
+ ------------------------------
+ [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
- = tcAddSrcLoc loc $
- tcAddErrCtxt ctxt $
- thing_inside
+instDeclCtxt1 hs_inst_ty
+ = inst_decl_ctxt (case unLoc hs_inst_ty of
+ HsForAllTy _ _ _ (L _ (HsPredTy pred)) -> ppr pred
+ HsPredTy pred -> ppr pred
+ other -> ppr hs_inst_ty) -- Don't expect this
+instDeclCtxt2 dfun_ty
+ = inst_decl_ctxt (ppr (mkClassPred cls tys))
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}
+ (_,_,cls,tys) = tcSplitDFunTy dfun_ty
-\begin{code}
-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 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)
- ]
-
-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])
-
-methodCtxt = ptext SLIT("When checking the methods of an instance declaration")
-superClassCtxt = ptext SLIT("When checking the superclasses of an instance declaration")
+inst_decl_ctxt doc = ptext SLIT("In the instance declaration for") <+> quotes doc
+
+superClassCtxt = ptext SLIT("When checking the super-classes of an instance declaration")
\end{code}
projects / ghc-hetmet.git / blobdiff