%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
+module TcInstDcls ( tcInstDecls1, tcIfaceInstDecls,
+ tcInstDecls2, tcAddDeclCtxt ) where
+
#include "HsVersions.h"
-module TcInstDcls (
- tcInstDecls1,
- tcInstDecls2,
- processInstBinds
- ) where
-
-
-import Ubiq
-
-import HsSyn ( InstDecl(..), FixityDecl, Sig(..),
- SpecInstSig(..), HsBinds(..), Bind(..),
- MonoBinds(..), GRHSsAndBinds, Match,
- InPat(..), OutPat(..), HsExpr(..), HsLit(..),
- Stmt, Qual, ArithSeqInfo, Fake,
- PolyType(..), MonoType )
-import RnHsSyn ( RenamedHsBinds(..), RenamedMonoBinds(..),
- RenamedInstDecl(..), RenamedFixityDecl(..),
- RenamedSig(..), RenamedSpecInstSig(..),
- RnName(..){-incl instance Outputable-}
- )
-import TcHsSyn ( TcIdOcc(..), TcHsBinds(..),
- TcMonoBinds(..), TcExpr(..), tcIdType,
- mkHsTyLam, mkHsTyApp,
- mkHsDictLam, mkHsDictApp )
+import CmdLineOpts ( DynFlag(..) )
-import TcMonad
-import GenSpecEtc ( checkSigTyVars )
-import Inst ( Inst, InstOrigin(..), InstanceMapper(..),
- newDicts, newMethod, LIE(..), emptyLIE, plusLIE )
-import TcBinds ( tcPragmaSigs )
+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 TcHsSyn ( TcMonoBinds, mkHsConApp )
+import TcBinds ( tcSpecSigs )
+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 Inst ( InstOrigin(..), tcInstClassOp, newDicts, instToId, showLIE )
import TcDeriv ( tcDeriving )
-import TcEnv ( tcLookupClass, tcTyVarScope, newLocalId )
-import TcGRHSs ( tcGRHSsAndBinds )
-import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs )
-import TcKind ( TcKind, unifyKind )
-import TcMatches ( tcMatchesFun )
-import TcMonoType ( tcContext, tcMonoTypeKind )
-import TcSimplify ( tcSimplifyAndCheck, tcSimplifyThetas )
-import TcType ( TcType(..), TcTyVar(..),
- tcInstSigTyVars, tcInstType, tcInstTheta
+import TcEnv ( tcExtendGlobalValEnv,
+ tcLookupClass, tcExtendTyVarEnv2,
+ tcExtendInstEnv, tcExtendLocalInstEnv, tcLookupGlobalId,
+ InstInfo(..), InstBindings(..), pprInstInfo, simpleInstInfoTyCon,
+ simpleInstInfoTy, newDFunName
)
-import Unify ( unifyTauTy )
-
-
-import Bag ( emptyBag, unitBag, unionBags, unionManyBags,
- concatBag, foldBag, bagToList )
-import CmdLineOpts ( opt_GlasgowExts, opt_CompilingPrelude,
- opt_OmitDefaultInstanceMethods,
- opt_SpecialiseOverloaded )
-import Class ( GenClass, GenClassOp,
- isCcallishClass, getClassBigSig,
- getClassOps, getClassOpLocalType )
-import CoreUtils ( escErrorMsg )
-import Id ( GenId, idType, isDefaultMethodId_maybe )
-import ListSetOps ( minusList )
-import Maybes ( maybeToBool, expectJust )
-import Name ( getLocalName, getOrigName )
-import PrelInfo ( pAT_ERROR_ID )
-import PprType ( GenType, GenTyVar, GenClass, GenClassOp, TyCon,
- pprParendGenType )
-import PprStyle
-import Pretty
-import RnUtils ( GlobalNameMappers(..), GlobalNameMapper(..) )
-import TyCon ( derivedFor )
-import Type ( GenType(..), ThetaType(..), mkTyVarTys,
- splitSigmaTy, splitAppTy, isTyVarTy, matchTy, mkSigmaTy,
- getTyCon_maybe, maybeBoxedPrimType )
-import TyVar ( GenTyVar, mkTyVarSet )
-import TysWiredIn ( stringTy )
-import Unique ( Unique )
-import Util ( panic )
+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 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 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 :: Bag RenamedInstDecl
- -> [RenamedSpecInstSig]
- -> Module -- module name for deriving
- -> GlobalNameMappers -- renamer fns for deriving
- -> [RenamedFixityDecl] -- fixities for deriving
- -> TcM s (Bag InstInfo,
- RenamedHsBinds,
- PprStyle -> Pretty)
-
-tcInstDecls1 inst_decls specinst_sigs mod_name renamer_name_funs fixities
- = -- Do the ordinary instance declarations
- mapBagNF_Tc (tcInstDecl1 mod_name) inst_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
- decl_inst_info = concatBag inst_info_bags
+ (src_inst_decls, iface_inst_decls) = partition isSourceInstDecl inst_decls
in
- -- Handle "derived" instances; note that we only do derivings
- -- for things in this module; we ignore deriving decls from
- -- interfaces! We pass fixities, because they may be used
- -- in deriving Read and Show.
- tcDeriving mod_name renamer_name_funs decl_inst_info fixities
- `thenTc` \ (deriv_inst_info, deriv_binds, ddump_deriv) ->
+
+ -- (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
- inst_info = deriv_inst_info `unionBags` decl_inst_info
+ local_inst_info = catMaybes local_inst_infos
+ clas_decls = filter isClassDecl tycl_decls
in
-{- LATER
- -- Handle specialise instance pragmas
- tcSpecInstSigs inst_info specinst_sigs
- `thenTc` \ spec_inst_info ->
--}
- let
- spec_inst_info = emptyBag -- For now
+ -- (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}
- full_inst_info = inst_info `unionBags` spec_inst_info
+\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
+ (tyvars, theta, tau) = tcSplitSigmaTy poly_ty'
in
- returnTc (full_inst_info, deriv_binds, ddump_deriv)
+ 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 :: FAST_STRING -> 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}
+
+
+%************************************************************************
+%* *
+\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 = ...
-tcInstDecl1 mod_name
- (InstDecl class_name
- poly_ty@(HsForAllTy tyvar_names context inst_ty)
- binds
- from_here inst_mod uprags pragmas src_loc)
- = -- Prime error recovery, set source location
- recoverNF_Tc (returnNF_Tc emptyBag) $
- tcAddSrcLoc src_loc $
+gives rise to the instance declarations
- -- Look things up
- tcLookupClass class_name `thenNF_Tc` \ (clas_kind, clas) ->
+ 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
- de_rn (RnName n) = n
+ gen_inst_info = concat gen_inst_infos
in
- -- Typecheck the context and instance type
- tcTyVarScope (map de_rn tyvar_names) (\ tyvars ->
- tcContext context `thenTc` \ theta ->
- tcMonoTypeKind inst_ty `thenTc` \ (tau_kind, tau) ->
- unifyKind clas_kind tau_kind `thenTc_`
- returnTc (tyvars, theta, tau)
- ) `thenTc` \ (inst_tyvars, inst_theta, inst_tau) ->
-
- -- Check for respectable instance type
- scrutiniseInstanceType from_here clas inst_tau
- `thenTc` \ (inst_tycon,arg_tys) ->
-
- -- Deal with the case where we are deriving
- -- and importing the same instance
- if (not from_here && (clas `derivedFor` inst_tycon)
- && all isTyVarTy arg_tys)
- then
- if not opt_CompilingPrelude && maybeToBool inst_mod &&
- mod_name == expectJust "inst_mod" inst_mod
- then
- -- Imported instance came from this module;
- -- discard and derive fresh instance
- returnTc emptyBag
- else
- -- Imported instance declared in another module;
- -- report duplicate instance error
- failTc (derivingWhenInstanceImportedErr inst_mod clas inst_tycon)
+ 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_`
- -- Make the dfun id and constant-method ids
- mkInstanceRelatedIds from_here inst_mod pragmas
- clas inst_tyvars inst_tau inst_theta uprags
- `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) ->
+ -- 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_`
- returnTc (unitBag (InstInfo clas inst_tyvars inst_tau inst_theta
- dfun_theta dfun_id const_meth_ids
- binds from_here inst_mod src_loc uprags))
+ returnM 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
+
+---------------------------------
+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 s, TcHsBinds s)
-
+tcInstDecls2 :: [InstInfo] -> TcM TcMonoBinds
tcInstDecls2 inst_decls
- = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyBinds)) inst_decls
- where
- combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
- tc2 `thenNF_Tc` \ (lie2, binds2) ->
- returnNF_Tc (lie1 `plusLIE` lie2,
- binds1 `ThenBinds` 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 s, TcHsBinds s)
-tcInstDecl2 (InstInfo _ _ _ _ _ _ _ _ False{-import-} _ _ _)
- = returnNF_Tc (emptyLIE, EmptyBinds)
+\begin{code}
+tcInstDecl2 :: InstInfo -> TcM TcMonoBinds
-tcInstDecl2 (InstInfo clas inst_tyvars inst_ty
- inst_decl_theta dfun_theta
- dfun_id const_meth_ids monobinds
- True{-here-} inst_mod locn uprags)
+tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds })
= -- Prime error recovery
- recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $
- tcAddSrcLoc locn $
-
- -- Get the class signature
- tcInstSigTyVars inst_tyvars `thenNF_Tc` \ (inst_tyvars', _, tenv) ->
- let
- (class_tyvar,
- super_classes, sc_sel_ids,
- class_ops, op_sel_ids, defm_ids) = getClassBigSig clas
+ 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
- tcInstType tenv inst_ty `thenNF_Tc` \ inst_ty' ->
- tcInstTheta tenv dfun_theta `thenNF_Tc` \ dfun_theta' ->
- tcInstTheta tenv inst_decl_theta `thenNF_Tc` \ inst_decl_theta' ->
+
+ -- Instantiate the instance decl with tc-style type variables
+ tcInstType InstTv inst_ty `thenM` \ (inst_tyvars', dfun_theta', inst_head') ->
let
- sc_theta' = super_classes `zip` (repeat inst_ty')
- origin = InstanceDeclOrigin
- mk_method sel_id = newMethodId sel_id inst_ty' origin locn
+ Just pred = tcSplitPredTy_maybe inst_head'
+ (clas, inst_tys') = getClassPredTys pred
+ (class_tyvars, sc_theta, _, op_items) = classBigSig clas
+
+ -- 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.
- 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_ty')] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+ 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
+ tcMethods clas inst_tyvars inst_tyvars'
+ dfun_theta' inst_tys' avail_insts
+ op_items binds `thenM` \ (meth_ids, meth_binds) ->
- -- Create method variables
- mapAndUnzipNF_Tc mk_method op_sel_ids `thenNF_Tc` \ (meth_insts_s, meth_ids) ->
+ -- 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) ->
- -- Collect available Insts
+ -- Deal with 'SPECIALISE instance' pragmas by making them
+ -- look like SPECIALISE pragmas for the dfun
let
- avail_insts -- These insts are in scope; quite a few, eh?
- = unionManyBags (this_dict : dfun_arg_dicts : meth_insts_s)
-
- mk_method_expr
- = if opt_OmitDefaultInstanceMethods then
- makeInstanceDeclNoDefaultExpr origin meth_ids defm_ids inst_ty' clas inst_mod
- else
- makeInstanceDeclDefaultMethodExpr origin meth_ids defm_ids inst_ty' this_dict_id
+ 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
- processInstBinds mk_method_expr inst_tyvars' avail_insts meth_ids monobinds
- `thenTc` \ (insts_needed, method_mbinds) ->
+ tcExtendGlobalValEnv [dfun_id] (
+ tcExtendTyVarEnv2 xtve $
+ tcSpecSigs spec_prags
+ ) `thenM` \ prag_binds ->
+
+ -- Create the result bindings
let
- -- Create the dict and method binds
- dict_bind
- = VarMonoBind this_dict_id (Dictionary sc_dict_ids meth_ids)
+ local_dfun_id = setIdLocalExported dfun_id
+ -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId
+
+ dict_constr = classDataCon clas
+ 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
+ = -- 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 rUNTIME_ERROR_ID) [idType this_dict_id])
+ (HsLit (HsStringPrim (mkFastString (stringToUtf8 msg))))
+
+ | otherwise -- The common case
+ = 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.mkDataConWrapId code rather
+ -- than needing to be repeated here.
+
+ where
+ 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)
- dict_and_method_binds
- = dict_bind `AndMonoBinds` method_mbinds
- inst_tyvars_set' = mkTyVarSet inst_tyvars'
+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
- -- Check the overloading constraints of the methods and superclasses
- tcAddErrCtxt (bindSigCtxt meth_ids) (
- tcSimplifyAndCheck
- inst_tyvars_set' -- Local tyvars
- avail_insts
- (sc_dicts `unionBags` insts_needed) -- Need to get defns for all these
- ) `thenTc` \ (const_lie, super_binds) ->
-
- -- 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 superClassSigCtxt (
- tcSimplifyAndCheck
- 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 process any SPECIALIZE pragmas for the methods
+ mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_`
+
+ -- Make the method bindings
let
- spec_sigs = [ s | s@(SpecSig _ _ _ _) <- uprags ]
+ mk_method_bind = mkMethodBind InstanceDeclOrigin clas inst_tys' monobinds
in
- tcPragmaSigs spec_sigs `thenTc` \ (_, spec_binds, spec_lie) ->
+ 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.
let
- -- Complete the binding group, adding any spec_binds
- inst_binds
- = AbsBinds
- inst_tyvars'
- dfun_arg_dicts_ids
- ((this_dict_id, RealId dfun_id)
- : (meth_ids `zip` (map RealId const_meth_ids)))
- -- const_meth_ids will often be empty
- super_binds
- (RecBind dict_and_method_binds)
-
- `ThenBinds`
- spec_binds
+ all_insts = avail_insts ++ meth_insts
+ xtve = inst_tyvars `zip` inst_tyvars'
+ tc_method_bind = tcMethodBind xtve inst_tyvars' dfun_theta' all_insts uprags
in
+ mapM tc_method_bind meth_infos `thenM` \ meth_binds_s ->
+
+ returnM (map instToId meth_insts, andMonoBindList meth_binds_s)
- returnTc (const_lie `plusLIE` spec_lie, inst_binds)
-\end{code}
-@mkMethodId@ manufactures an id for a local method.
-It's rather turgid stuff, because there are two cases:
+-- 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 ->
+ 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 ->
- (a) For methods with no local polymorphism, we can make an Inst of the
- class-op selector function and a corresp InstId;
- which is good because then other methods which call
- this one will do so directly.
+ -- I don't think we have to do the checkSigTyVars thing
- (b) For methods with local polymorphism, we can't do this. For example,
+ returnM (meth_ids, lie_binds `AndMonoBinds` andMonoBindList meth_binds)
- class Foo a where
- op :: (Num b) => a -> b -> a
+ where
+ 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, VarMonoBind meth_id (HsVar (instToId rhs_inst)), rhs_inst)
+
+ -- Instantiate rep_tys with the relevant type variables
+ rep_tys' = map (substTy subst) rep_tys
+ subst = mkTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars')
+\end{code}
- Here the type of the class-op-selector is
+Note: [Superclass loops]
+~~~~~~~~~~~~~~~~~~~~~~~~~
+We have to be very, very careful when generating superclasses, lest we
+accidentally build a loop. Here's an example:
- forall a b. (Foo a, Num b) => a -> b -> a
+ class S a
- The locally defined method at (say) type Float will have type
+ 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
- forall b. (Num b) => Float -> b -> Float
+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.
- and the one is not an instance of the other.
+Alas! Alack! We can do the same for (instance D Int):
- So for these we just make a local (non-Inst) id with a suitable type.
+ $dfDInt = :D ds2 (opc dc)
+ dc = $dfCInt
+ ds2 = $p1 dc
-How disgusting.
+And now we've defined the superclass in terms of itself.
-\begin{code}
-newMethodId sel_id inst_ty origin loc
- = let (sel_tyvars,sel_theta,sel_tau) = splitSigmaTy (idType sel_id)
- (_:meth_theta) = sel_theta -- The local theta is all except the
- -- first element of the context
- in
- case sel_tyvars of
- -- Ah! a selector for a class op with no local polymorphism
- -- Build an Inst for this
- [clas_tyvar] -> newMethod origin (RealId sel_id) [inst_ty]
-
- -- Ho! a selector for a class op with local polymorphism.
- -- Just make a suitably typed local id for this
- (clas_tyvar:local_tyvars) ->
- tcInstType [(clas_tyvar,inst_ty)]
- (mkSigmaTy local_tyvars meth_theta sel_tau)
- `thenNF_Tc` \ method_ty ->
- newLocalId (getLocalName sel_id) method_ty `thenNF_Tc` \ meth_id ->
- returnNF_Tc (emptyLIE, meth_id)
-\end{code}
-The next function makes a default method which calls the global default method, at
-the appropriate instance type.
+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.
-See the notes under default decls in TcClassDcl.lhs.
+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}
-makeInstanceDeclDefaultMethodExpr
- :: InstOrigin s
- -> [TcIdOcc s]
- -> [Id]
- -> TcType s
- -> TcIdOcc s
- -> Int
- -> NF_TcM s (TcExpr s)
-
-makeInstanceDeclDefaultMethodExpr origin meth_ids defm_ids inst_ty this_dict tag
- = newDicts origin op_theta `thenNF_Tc` \ (op_lie,op_dicts) ->
-
- -- def_op_id = /\ op_tyvars -> \ op_dicts ->
- -- defm_id inst_ty op_tyvars this_dict op_dicts
- returnNF_Tc (
- mkHsTyLam op_tyvars (
- mkHsDictLam op_dicts (
- mkHsDictApp (mkHsTyApp (HsVar (RealId defm_id))
- (inst_ty : mkTyVarTys op_tyvars))
- (this_dict : op_dicts)
- )))
- where
- idx = tag - 1
- meth_id = meth_ids !! idx
- defm_id = defm_ids !! idx
- (op_tyvars, op_theta, op_tau) = splitSigmaTy (tcIdType meth_id)
-
-makeInstanceDeclNoDefaultExpr
- :: InstOrigin s
- -> [TcIdOcc s]
- -> [Id]
- -> TcType s
- -> Class
- -> Maybe Module
- -> Int
- -> NF_TcM s (TcExpr s)
-
-makeInstanceDeclNoDefaultExpr origin meth_ids defm_ids inst_ty clas inst_mod tag
- = newDicts origin op_theta `thenNF_Tc` \ (op_lie, op_dicts) ->
-
- -- Produce a warning if the default instance method
- -- has been omitted when one exists in the class
- warnTc (not err_defm_ok)
- (omitDefaultMethodWarn clas_op clas_name inst_ty)
- `thenNF_Tc_`
- returnNF_Tc (mkHsTyLam op_tyvars (
- mkHsDictLam op_dicts (
- HsApp (mkHsTyApp (HsVar (RealId pAT_ERROR_ID)) [op_tau])
- (HsLitOut (HsString (_PK_ error_msg)) stringTy))))
- where
- idx = tag - 1
- meth_id = meth_ids !! idx
- clas_op = (getClassOps clas) !! idx
- defm_id = defm_ids !! idx
- (op_tyvars,op_theta,op_tau) = splitSigmaTy (tcIdType meth_id)
+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) ->
- Just (_, _, err_defm_ok) = isDefaultMethodId_maybe defm_id
+ -- It's possible that the superclass stuff might have done unification
+ checkSigTyVars inst_tyvars' `thenM` \ zonked_inst_tyvars ->
- error_msg = "%E" -- => No explicit method for \"
- ++ escErrorMsg error_str
+ -- We must simplify this all the way down
+ -- lest we build superclass loops
+ -- See Note [Superclass loops] above
+ tcSimplifyTop sc_lie `thenM` \ sc_binds2 ->
- mod_str = case inst_mod of { Nothing -> SLIT("Prelude"); Just m -> m }
+ returnM (zonked_inst_tyvars, sc_binds1, sc_binds2)
- error_str = _UNPK_ mod_str ++ "." ++ _UNPK_ clas_name ++ "."
- ++ (ppShow 80 (ppr PprForUser inst_ty)) ++ "."
- ++ (ppShow 80 (ppr PprForUser clas_op)) ++ "\""
-
- (_, clas_name) = getOrigName clas
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection{Processing each method}
-%* *
-%************************************************************************
-
-@processInstBinds@ returns a @MonoBinds@ which binds
-all the method ids (which are passed in). It is used
- - both for instance decls,
- - and to compile the default-method declarations in a class decl.
-
-Any method ids which don't have a binding have a suitable default
-binding created for them. The actual right-hand side used is
-created using a function which is passed in, because the right thing to
-do differs between instance and class decls.
-
-\begin{code}
-processInstBinds
- :: (Int -> NF_TcM s (TcExpr s)) -- Function to make default method
- -> [TcTyVar s] -- Tyvars for this instance decl
- -> LIE s -- available Insts
- -> [TcIdOcc s] -- Local method ids in tag order
- -- (instance tyvars are free in their types)
- -> RenamedMonoBinds
- -> TcM s (LIE s, -- These are required
- TcMonoBinds s)
-
-processInstBinds mk_default_method_rhs inst_tyvars avail_insts method_ids monobinds
- =
- -- Process the explicitly-given method bindings
- processInstBinds1 inst_tyvars avail_insts method_ids monobinds
- `thenTc` \ (tags, insts_needed_in_methods, method_binds) ->
-
- -- Find the methods not handled, and make default method bindings for them.
- let
- unmentioned_tags = [1.. length method_ids] `minusList` tags
- in
- mapNF_Tc mk_default_method unmentioned_tags
- `thenNF_Tc` \ default_bind_list ->
-
- returnTc (insts_needed_in_methods,
- foldr AndMonoBinds method_binds default_bind_list)
where
- -- From a tag construct us the passed-in function to construct
- -- the binding for the default method
- mk_default_method tag = mk_default_method_rhs tag `thenNF_Tc` \ rhs ->
- returnNF_Tc (VarMonoBind (method_ids !! (tag-1)) rhs)
-\end{code}
-
-\begin{code}
-processInstBinds1
- :: [TcTyVar s] -- Tyvars for this instance decl
- -> LIE s -- available Insts
- -> [TcIdOcc s] -- Local method ids in tag order (instance tyvars are free),
- -> RenamedMonoBinds
- -> TcM s ([Int], -- Class-op tags accounted for
- LIE s, -- These are required
- TcMonoBinds s)
-
-processInstBinds1 inst_tyvars avail_insts method_ids EmptyMonoBinds
- = returnTc ([], emptyLIE, EmptyMonoBinds)
-
-processInstBinds1 inst_tyvars avail_insts method_ids (AndMonoBinds mb1 mb2)
- = processInstBinds1 inst_tyvars avail_insts method_ids mb1
- `thenTc` \ (op_tags1,dicts1,method_binds1) ->
- processInstBinds1 inst_tyvars avail_insts method_ids mb2
- `thenTc` \ (op_tags2,dicts2,method_binds2) ->
- returnTc (op_tags1 ++ op_tags2,
- dicts1 `unionBags` dicts2,
- AndMonoBinds method_binds1 method_binds2)
+ doc = ptext SLIT("instance declaration superclass context")
\end{code}
-\begin{code}
-processInstBinds1 inst_tyvars avail_insts method_ids mbind
- =
- -- Find what class op is being defined here. The complication is
- -- that we could have a PatMonoBind or a FunMonoBind. If the
- -- former, it should only bind a single variable, or else we're in
- -- trouble (I'm not sure what the static semantics of methods
- -- defined in a pattern binding with multiple patterns is!)
- -- Renamer has reduced us to these two cases.
- let
- (op,locn) = case mbind of
- FunMonoBind op _ _ locn -> (op, locn)
- PatMonoBind (VarPatIn op) _ locn -> (op, locn)
- occ = getLocalName op
- origin = InstanceDeclOrigin
- in
- tcAddSrcLoc locn $
-
- -- Make a method id for the method
- let tag = panic "processInstBinds1:getTagFromClassOpName"{-getTagFromClassOpName op-}
- method_id = method_ids !! (tag-1)
-
- method_ty = tcIdType method_id
- (method_tyvars, method_theta, method_tau) = splitSigmaTy method_ty
- in
- newDicts origin method_theta `thenNF_Tc` \ (method_dicts,method_dict_ids) ->
-
- case (method_tyvars, method_dict_ids) of
-
- ([],[]) -> -- The simple case; no local polymorphism or overloading in the method
-
- -- Type check the method itself
- tcMethodBind method_id method_tau mbind `thenTc` \ (mbind', lieIop) ->
- returnTc ([tag], lieIop, mbind')
-
- other -> -- It's a locally-polymorphic and/or overloaded method; UGH!
-
- -- Make a new id for (a) the local, non-overloaded method
- -- and (b) the locally-overloaded method
- -- The latter is needed just so we can return an AbsBinds wrapped
- -- up inside a MonoBinds.
-
- newLocalId occ method_tau `thenNF_Tc` \ local_id ->
- newLocalId occ method_ty `thenNF_Tc` \ copy_id ->
- let
- inst_method_tyvars = inst_tyvars ++ method_tyvars
- in
- -- Typecheck the method
- tcMethodBind local_id method_tau mbind `thenTc` \ (mbind', lieIop) ->
-
- -- Check the overloading part of the signature.
- -- Simplify everything fully, even though some
- -- constraints could "really" be left to the next
- -- level out. The case which forces this is
- --
- -- class Foo a where { op :: Bar a => a -> a }
- --
- -- Here we must simplify constraints on "a" to catch all
- -- the Bar-ish things.
- tcAddErrCtxt (methodSigCtxt op method_ty) (
- tcSimplifyAndCheck
- (mkTyVarSet inst_method_tyvars)
- (method_dicts `plusLIE` avail_insts)
- lieIop
- ) `thenTc` \ (f_dicts, dict_binds) ->
-
- returnTc ([tag],
- f_dicts,
- VarMonoBind method_id
- (HsLet
- (AbsBinds
- method_tyvars
- method_dict_ids
- [(local_id, copy_id)]
- dict_binds
- (NonRecBind mbind'))
- (HsVar copy_id)))
-\end{code}
-
-\begin{code}
-tcMethodBind :: TcIdOcc s -> TcType s -> RenamedMonoBinds
- -> TcM s (TcMonoBinds s, LIE s)
-
-tcMethodBind meth_id meth_ty (FunMonoBind name inf matches locn)
- = tcMatchesFun name meth_ty matches `thenTc` \ (rhs', lie) ->
- returnTc (FunMonoBind meth_id inf rhs' locn, lie)
-
-tcMethodBind meth_id meth_ty pbind@(PatMonoBind pat grhss_and_binds locn)
- -- pat is sure to be a (VarPatIn op)
- = tcAddErrCtxt (patMonoBindsCtxt pbind) $
- tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, rhs_ty) ->
- unifyTauTy meth_ty rhs_ty `thenTc_`
- returnTc (PatMonoBind (VarPat meth_id) grhss_and_binds' locn, lie)
-\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{Type-checking specialise instance pragmas}
+\subsection{Error messages}
%* *
%************************************************************************
\begin{code}
-{- LATER
-tcSpecInstSigs :: E -> CE -> TCE
- -> Bag InstInfo -- inst decls seen (declared and derived)
- -> [RenamedSpecInstSig] -- specialise instance upragmas
- -> TcM (Bag InstInfo) -- new, overlapped, inst decls
-
-tcSpecInstSigs e ce tce inst_infos []
- = returnTc emptyBag
-
-tcSpecInstSigs e ce tce inst_infos sigs
- = buildInstanceEnvs inst_infos `thenTc` \ inst_mapper ->
- tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ spec_inst_infos ->
- returnTc spec_inst_infos
- where
- tc_inst_spec_sigs inst_mapper []
- = returnNF_Tc emptyBag
- tc_inst_spec_sigs inst_mapper (sig:sigs)
- = tcSpecInstSig e ce tce inst_infos inst_mapper sig `thenNF_Tc` \ info_sig ->
- tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ info_sigs ->
- returnNF_Tc (info_sig `unionBags` info_sigs)
-
-tcSpecInstSig :: E -> CE -> TCE
- -> Bag InstInfo
- -> InstanceMapper
- -> RenamedSpecInstSig
- -> NF_TcM (Bag InstInfo)
-
-tcSpecInstSig e ce tce inst_infos inst_mapper (SpecInstSig class_name ty src_loc)
- = recoverTc emptyBag (
- tcAddSrcLoc src_loc (
- let
- clas = lookupCE ce class_name -- Renamer ensures this can't fail
-
- -- Make some new type variables, named as in the specialised instance type
- ty_names = extractMonoTyNames (==) ty
- (tmpl_e,inst_tmpls,inst_tmpl_tys) = mkTVE ty_names
- in
- babyTcMtoTcM (tcInstanceType ce tce tmpl_e True src_loc ty)
- `thenTc` \ inst_ty ->
- let
- maybe_tycon = case maybeAppDataTyCon inst_ty of
- Just (tc,_,_) -> Just tc
- Nothing -> Nothing
-
- maybe_unspec_inst = lookup_unspec_inst clas maybe_tycon inst_infos
- in
- -- Check that we have a local instance declaration to specialise
- checkMaybeTc maybe_unspec_inst
- (specInstUnspecInstNotFoundErr clas inst_ty src_loc) `thenTc_`
-
- -- Create tvs to substitute for tmpls while simplifying the context
- copyTyVars inst_tmpls `thenNF_Tc` \ (tv_e, inst_tvs, inst_tv_tys) ->
- let
- Just (InstInfo _ unspec_tyvars unspec_inst_ty unspec_theta
- _ _ _ binds True{-from here-} mod _ uprag) = maybe_unspec_inst
-
- subst = case matchTy unspec_inst_ty inst_ty of
- Just subst -> subst
- Nothing -> panic "tcSpecInstSig:matchTy"
-
- subst_theta = instantiateThetaTy subst unspec_theta
- subst_tv_theta = instantiateThetaTy tv_e subst_theta
-
- mk_spec_origin clas ty
- = InstanceSpecOrigin inst_mapper clas ty src_loc
- in
- tcSimplifyThetas mk_spec_origin subst_tv_theta
- `thenTc` \ simpl_tv_theta ->
- let
- simpl_theta = [ (clas, tv_to_tmpl tv) | (clas, tv) <- simpl_tv_theta ]
-
- tv_tmpl_map = inst_tv_tys `zipEqual` inst_tmpl_tys
- tv_to_tmpl tv = assoc "tcSpecInstSig" tv_tmpl_map tv
- in
- mkInstanceRelatedIds e True{-from here-} mod NoInstancePragmas src_loc
- clas inst_tmpls inst_ty simpl_theta uprag
- `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) ->
-
- getSwitchCheckerTc `thenNF_Tc` \ sw_chkr ->
- (if sw_chkr SpecialiseTrace then
- pprTrace "Specialised Instance: "
- (ppAboves [ppCat [if null simpl_theta then ppNil else ppr PprDebug simpl_theta,
- if null simpl_theta then ppNil else ppStr "=>",
- ppr PprDebug clas,
- pprParendGenType PprDebug inst_ty],
- ppCat [ppStr " derived from:",
- if null unspec_theta then ppNil else ppr PprDebug unspec_theta,
- if null unspec_theta then ppNil else ppStr "=>",
- ppr PprDebug clas,
- pprParendGenType PprDebug unspec_inst_ty]])
- else id) (
-
- returnTc (unitBag (InstInfo clas inst_tmpls inst_ty simpl_theta
- dfun_theta dfun_id const_meth_ids
- binds True{-from here-} mod src_loc uprag))
- )))
-
-
-lookup_unspec_inst clas maybe_tycon inst_infos
- = case filter (match_info match_inst_ty) (bagToList inst_infos) of
- [] -> Nothing
- (info:_) -> Just info
- where
- match_info match_ty (InstInfo inst_clas _ inst_ty _ _ _ _ _ from_here _ _ _)
- = from_here && clas == inst_clas &&
- match_ty inst_ty && is_plain_instance inst_ty
-
- match_inst_ty = case maybe_tycon of
- Just tycon -> match_tycon tycon
- Nothing -> match_fun
-
- match_tycon tycon inst_ty = case (maybeAppDataTyCon inst_ty) of
- Just (inst_tc,_,_) -> tycon == inst_tc
- Nothing -> False
-
- match_fun inst_ty = isFunType inst_ty
-
-
-is_plain_instance inst_ty
- = case (maybeAppDataTyCon inst_ty) of
- Just (_,tys,_) -> all isTyVarTemplateTy tys
- Nothing -> case maybeUnpackFunTy inst_ty of
- Just (arg, res) -> isTyVarTemplateTy arg && isTyVarTemplateTy res
- Nothing -> error "TcInstDecls:is_plain_instance"
--}
-\end{code}
-
-
-Checking for a decent instance type
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-@scrutiniseInstanceType@ 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.
-
-We can also have instances for functions: @instance Foo (a -> b) ...@.
-
-\begin{code}
-scrutiniseInstanceType from_here clas inst_tau
- -- TYCON CHECK
- | not (maybeToBool inst_tycon_maybe)
- = failTc (instTypeErr inst_tau)
-
- -- IMPORTED INSTANCES ARE OK (but see tcInstDecl1)
- | from_here
- = returnTc (inst_tycon,arg_tys)
-
- -- TYVARS CHECK
- | not (all isTyVarTy arg_tys ||
- not from_here ||
- opt_GlasgowExts)
- = failTc (instTypeErr inst_tau)
-
- -- DERIVING CHECK
- -- It is obviously illegal to have an explicit instance
- -- for something that we are also planning to `derive'
- -- Though we can have an explicit instance which is more
- -- specific than the derived instance
- | clas `derivedFor` inst_tycon
- && all isTyVarTy arg_tys
- = failTc (derivingWhenInstanceExistsErr clas inst_tycon)
-
- | -- CCALL CHECK
- -- A user declaration of a _CCallable/_CReturnable instance
- -- must be for a "boxed primitive" type.
- isCcallishClass clas
- && not opt_CompilingPrelude -- which allows anything
- && maybeToBool (maybeBoxedPrimType inst_tau)
- = failTc (nonBoxedPrimCCallErr clas inst_tau)
-
- | otherwise
- = returnTc (inst_tycon,arg_tys)
-
+tcAddDeclCtxt decl thing_inside
+ = addSrcLoc (tcdLoc decl) $
+ addErrCtxt ctxt $
+ thing_inside
where
- (possible_tycon, arg_tys) = splitAppTy inst_tau
- inst_tycon_maybe = getTyCon_maybe possible_tycon
- inst_tycon = expectJust "tcInstDecls1:inst_tycon" inst_tycon_maybe
+ 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}
-
-instTypeErr ty sty
- = case ty of
- SynTy tc _ _ -> ppBesides [ppStr "The type synonym `", ppr sty tc, rest_of_msg]
- TyVarTy tv -> ppBesides [ppStr "The type variable `", ppr sty tv, rest_of_msg]
- other -> ppBesides [ppStr "The type `", ppr sty ty, rest_of_msg]
- where
- rest_of_msg = ppStr "' cannot be used as an instance type."
-
-derivingWhenInstanceExistsErr clas tycon sty
- = ppHang (ppBesides [ppStr "Deriving class `", ppr sty clas, ppStr "' type `", ppr sty tycon, ppStr "'"])
- 4 (ppStr "when an explicit instance exists")
-
-derivingWhenInstanceImportedErr inst_mod clas tycon sty
- = ppHang (ppBesides [ppStr "Deriving class `", ppr sty clas, ppStr "' type `", ppr sty tycon, ppStr "'"])
- 4 (ppBesides [ppStr "when an instance declared in module `", pp_mod, ppStr "' has been imported"])
- where
- pp_mod = case inst_mod of
- Nothing -> ppPStr SLIT("the standard Prelude")
- Just m -> ppBesides [ppStr "module `", ppPStr m, ppStr "'"]
-
-nonBoxedPrimCCallErr clas inst_ty sty
- = ppHang (ppStr "Instance isn't for a `boxed-primitive' type")
- 4 (ppBesides [ ppStr "class `", ppr sty clas, ppStr "' type `",
- ppr sty inst_ty, ppStr "'"])
-
-omitDefaultMethodWarn clas_op clas_name inst_ty sty
- = ppCat [ppStr "Warning: Omitted default method for",
- ppr sty clas_op, ppStr "in instance",
- ppPStr clas_name, pprParendGenType sty inst_ty]
-
-
-patMonoBindsCtxt pbind sty
- = ppHang (ppStr "In a pattern binding:")
- 4 (ppr sty pbind)
-
-methodSigCtxt name ty sty
- = ppHang (ppBesides [ppStr "When matching the definition of class method `",
- ppr sty name, ppStr "' to its signature :" ])
- 4 (ppr sty ty)
-
-bindSigCtxt method_ids sty
- = ppHang (ppStr "When checking type signatures for: ")
- 4 (ppInterleave (ppStr ", ") (map (ppr sty) method_ids))
-
-superClassSigCtxt sty
- = ppStr "When checking superclass constraints on instance declaration"
-
+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 super-classes of an instance declaration")
\end{code}
projects / ghc-hetmet.git / blobdiff