%
-% (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,
- tcInstDecls2
- ) where
+module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where
#include "HsVersions.h"
-import HsSyn ( HsDecl(..), InstDecl(..),
- HsBinds(..), MonoBinds(..), GRHSsAndBinds(..), GRHS(..),
- HsExpr(..), InPat(..), HsLit(..), Sig(..),
- unguardedRHS,
- collectMonoBinders, andMonoBinds
- )
-import HsBinds ( sigsForMe )
-import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds,
- RenamedInstDecl, RenamedHsExpr,
- RenamedSig, RenamedHsDecl
- )
-import TcHsSyn ( TcMonoBinds, TcIdOcc(..), TcIdBndr,
- maybeBoxedPrimType, tcIdType
- )
-
-import TcBinds ( tcPragmaSigs )
-import TcClassDcl ( tcMethodBind, badMethodErr )
-import TcMonad
-import RnMonad ( RnNameSupply )
-import Inst ( Inst, InstOrigin(..),
- newDicts, 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 ( GlobalValueEnv, tcExtendGlobalValEnv, tcAddImportedIdInfo )
-import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, classDataCon )
-import TcKind ( TcKind, unifyKind )
-import TcMonoType ( tcHsType )
-import TcSimplify ( tcSimplifyAndCheck )
-import TcType ( TcType, TcTyVar, TcTyVarSet,
- zonkSigTyVar, tcInstSigType, tcInstTheta
- )
-
-import Bag ( emptyBag, unitBag, unionBags, unionManyBags,
- foldBag, bagToList, Bag
- )
-import CmdLineOpts ( opt_GlasgowExts )
-import Class ( classBigSig, Class )
-import Id ( isNullaryDataCon, dataConArgTys, replaceIdInfo, idName, idType, Id )
-import Maybes ( maybeToBool, seqMaybe, catMaybes, expectJust )
-import Name ( nameOccName, mkLocalName,
- isLocallyDefined, Module,
- NamedThing(..)
- )
-import PrelVals ( eRROR_ID )
-import PprType ( pprParendType, pprConstraint )
-import SrcLoc ( SrcLoc, noSrcLoc )
-import TyCon ( isSynTyCon, isDataTyCon, tyConDerivings )
-import Type ( Type, ThetaType, isUnpointedType,
- splitSigmaTy, isTyVarTy, mkSigmaTy,
- splitTyConApp_maybe, splitDictTy_maybe,
- splitAlgTyConApp_maybe, splitRhoTy,
- tyVarsOfTypes, mkTyVarTys,
+import TcEnv ( InstInfo(..), InstBindings(..),
+ newDFunName, tcExtendIdEnv
)
-import TyVar ( zipTyVarEnv, mkTyVarSet, tyVarSetToList, TyVar )
-import TysPrim ( byteArrayPrimTyCon, mutableByteArrayPrimTyCon )
-import TysWiredIn ( stringTy )
-import Unique ( Unique, cCallableClassKey, cReturnableClassKey, Uniquable(..) )
+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
and $dbinds_super$ bind the superclass dictionaries sd1 \ldots sdm.
\end{enumerate}
-\begin{code}
-tcInstDecls1 :: GlobalValueEnv -- Contains IdInfo for dfun ids
- -> [RenamedHsDecl]
- -> Module -- module name for deriving
- -> RnNameSupply -- for renaming derivings
- -> TcM s (Bag InstInfo,
- RenamedHsBinds,
- SDoc)
-
-tcInstDecls1 unf_env decls mod_name rn_name_supply
- = -- Do the ordinary instance declarations
- mapNF_Tc (tcInstDecl1 unf_env mod_name)
- [inst_decl | InstD inst_decl <- decls] `thenNF_Tc` \ inst_info_bags ->
- let
- decl_inst_info = unionManyBags inst_info_bags
- in
- -- Handle "derived" instances; note that we only do derivings
- -- for things in this module; we ignore deriving decls from
- -- interfaces!
- tcDeriving mod_name rn_name_supply decl_inst_info
- `thenTc` \ (deriv_inst_info, deriv_binds, ddump_deriv) ->
- let
- full_inst_info = deriv_inst_info `unionBags` decl_inst_info
- in
- returnTc (full_inst_info, deriv_binds, ddump_deriv)
+%************************************************************************
+%* *
+\subsection{Extracting instance decls}
+%* *
+%************************************************************************
+Gather up the instance declarations from their various sources
-tcInstDecl1 :: GlobalValueEnv -> Module -> RenamedInstDecl -> NF_TcM s (Bag InstInfo)
+\begin{code}
+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
+ mappM tcLocalInstDecl1 inst_decls `thenM` \ local_inst_infos ->
-tcInstDecl1 unf_env mod_name (InstDecl poly_ty binds uprags (Just dfun_name) src_loc)
- = -- Prime error recovery, set source location
- recoverNF_Tc (returnNF_Tc emptyBag) $
- tcAddSrcLoc src_loc $
+ let
+ local_inst_info = catMaybes local_inst_infos
+ clas_decls = filter (isClassDecl.unLoc) tycl_decls
+ in
+ -- (2) Instances from generic class declarations
+ getGenericInstances clas_decls `thenM` \ generic_inst_info ->
+
+ -- Next, construct the instance environment so far, consisting of
+ -- a) local instance decls
+ -- b) generic instances
+ addInsts local_inst_info $
+ addInsts generic_inst_info $
+
+ -- (3) Compute instances from "deriving" clauses;
+ -- 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) ->
+ 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}
+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"
- tcHsType 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
- Nothing -> pprPanic "tcInstDecl1" (ppr poly_ty)
- Just pair -> pair
+ (tyvars, theta, tau) = tcSplitSigmaTy poly_ty'
+ in
+ 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
- -- Check for respectable instance type, and context
- scrutiniseInstanceHead clas inst_tys `thenNF_Tc_`
- mapNF_Tc scrutiniseInstanceConstraint theta `thenNF_Tc_`
+ tcIsHsBoot `thenM` \ is_boot ->
+ checkTc (not is_boot || (isEmptyLHsBinds binds && null uprags))
+ badBootDeclErr `thenM_`
- -- Make the dfun id and constant-method ids
- let
- (dfun_id, dfun_theta) = mkInstanceRelatedIds dfun_name
- clas tyvars inst_tys theta
- -- Add info from interface file
- final_dfun_id = tcAddImportedIdInfo unf_env dfun_id
- in
- returnTc (unitBag (InstInfo clas tyvars inst_tys theta
- dfun_theta final_dfun_id
- binds src_loc uprags))
+ returnM (Just (InstInfo { iSpec = ispec, iBinds = VanillaInst binds uprags }))
+ where
+ msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class"))
\end{code}
%************************************************************************
\begin{code}
-tcInstDecls2 :: Bag InstInfo
- -> NF_TcM s (LIE s, TcMonoBinds s)
-
-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)
+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) ==============
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, TcMonoBinds s)
-
-tcInstDecl2 (InstInfo clas inst_tyvars inst_tys
- inst_decl_theta dfun_theta
- dfun_id monobinds
- locn uprags)
- | not (isLocallyDefined dfun_id)
- = returnNF_Tc (emptyLIE, EmptyMonoBinds)
-
-{-
- -- I deleted this "optimisation" because when importing these
- -- instance decls the renamer would look for the dfun bindings and they weren't there.
- -- This would be fixable, but it seems simpler just to produce a tiny void binding instead,
- -- even though it's never used.
-
- -- This case deals with CCallable etc, which don't need any bindings
- | isNoDictClass clas
- = returnNF_Tc (emptyLIE, EmptyBinds)
--}
-
- | otherwise
- = -- Prime error recovery
- recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
- tcAddSrcLoc locn $
-
- -- Instantiate the instance decl with tc-style type variables
- tcInstSigType (idType dfun_id) `thenNF_Tc` \ dfun_ty' ->
- let
- (inst_tyvars',
- dfun_theta', dict_ty') = splitSigmaTy dfun_ty'
-
- (clas, inst_tys') = expectJust "tcInstDecl2" (splitDictTy_maybe dict_ty')
- (class_tyvars,
- sc_theta, sc_sel_ids,
- op_sel_ids, defm_ids) = classBigSig clas
+\begin{code}
+tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id)
- origin = InstanceDeclOrigin
+tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = binds })
+ = let
+ dfun_id = instanceDFunId ispec
+ rigid_info = InstSkol dfun_id
+ inst_ty = idType dfun_id
in
- -- Instantiate the theta found in the original instance decl
- tcInstTheta (zipTyVarEnv inst_tyvars (mkTyVarTys inst_tyvars'))
- inst_decl_theta `thenNF_Tc` \ inst_decl_theta' ->
-
- -- Instantiate the super-class context with the instance types
- tcInstTheta (zipTyVarEnv class_tyvars inst_tys') sc_theta `thenNF_Tc` \ sc_theta' ->
+ -- 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') = tcSplitDFunHead inst_head'
+ (class_tyvars, sc_theta, _, op_items) = classBigSig clas
+ -- Instantiate the super-class context with inst_tys
+ sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta
+ origin = SigOrigin rigid_info
+ in
-- Create dictionary Ids from the specified instance contexts.
- newDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) ->
- newDicts origin dfun_theta' `thenNF_Tc` \ (dfun_arg_dicts, dfun_arg_dicts_ids) ->
- newDicts origin inst_decl_theta' `thenNF_Tc` \ (inst_decl_dicts, _) ->
- newDicts origin [(clas,inst_tys')] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
-
- -- Check that all the method bindings come from this class
+ 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
+ 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
- check_from_this_class (bndr, loc)
- | nameOccName bndr `elem` sel_names = returnNF_Tc ()
- | otherwise = tcAddSrcLoc loc $
- addErrTc (badMethodErr bndr clas)
- sel_names = map getOccName op_sel_ids
- bndrs = bagToList (collectMonoBinders monobinds)
+ specs = case binds of
+ VanillaInst _ prags -> filter isSpecInstLSig prags
+ other -> []
in
- mapNF_Tc check_from_this_class bndrs `thenNF_Tc_`
+ tcPrags dfun_id specs `thenM` \ prags ->
+
+ -- Create the result bindings
+ let
+ dict_constr = classDataCon clas
+ 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
+ = 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.
- tcExtendGlobalValEnv (catMaybes defm_ids) (
+ where
+ msg = "Compiler error: bad dictionary " ++ showSDoc (ppr clas)
- -- Default-method Ids may be mentioned in synthesised RHSs
- mapAndUnzip3Tc (tcMethodBind clas origin inst_tys' inst_tyvars' monobinds uprags True)
- (op_sel_ids `zip` defm_ids)
- ) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) ->
+ dict_bind = noLoc (VarBind this_dict_id dict_rhs)
+ all_binds = dict_bind `consBag` (sc_binds `unionBags` meth_binds)
- -- Deal with SPECIALISE instance pragmas
- let
- dfun_prags = [Sig (idName dfun_id) ty loc | SpecInstSig ty loc <- uprags]
+ main_bind = noLoc $ AbsBinds
+ inst_tyvars'
+ (map instToId dfun_arg_dicts)
+ [(inst_tyvars', dfun_id, this_dict_id,
+ inline_prag ++ prags)]
+ all_binds
in
- tcExtendGlobalValEnv [dfun_id] (
- tcPragmaSigs dfun_prags
- ) `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
+ showLIE (text "instance") `thenM_`
+ returnM (unitBag main_bind)
- -- Check the overloading constraints of the methods and superclasses
- mapNF_Tc zonkSigTyVar inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars ->
+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
- inst_tyvars_set = mkTyVarSet zonked_inst_tyvars
+ sel_names = [idName sel_id | (sel_id, _) <- op_items]
+ bad_bndrs = collectHsBindBinders monobinds `minusList` sel_names
+ in
+ mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_`
- (meth_lies, meth_ids) = unzip meth_lies_w_ids
+ -- 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
- -- These insts are in scope; quite a few, eh?
- avail_insts = this_dict `plusLIE`
- dfun_arg_dicts `plusLIE`
- sc_dicts `plusLIE`
- unionManyBags meth_lies
+ mapM tc_method_bind meth_infos `thenM` \ meth_binds_s ->
+
+ returnM (meth_ids, unionManyBags meth_binds_s)
- methods_lie = plusLIEs insts_needed_s
- 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) ->
+-- 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) ->
- -- 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) ->
-
+ tcSimplifyCheck
+ (ptext SLIT("newtype derived instance"))
+ inst_tyvars' avail_insts rhs_insts `thenM` \ lie_binds ->
- -- Create the result bindings
- let
- dict_constr = classDataCon clas
- scs_and_meths = sc_dict_ids ++ meth_ids
+ -- I don't think we have to do the checkSigTyVars thing
- dict_rhs
- | null scs_and_meths
- = -- Blatant special case for CCallable, CReturnable [and Eval -- sof 5/98]
- -- 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 (RealId eRROR_ID)) [tcIdType this_dict_id])
- (HsLitOut (HsString msg) stringTy)
-
- | otherwise -- The common case
- = HsCon dict_constr inst_tys' (map HsVar (sc_dict_ids ++ meth_ids))
- -- We don't produce a binding for the dict_constr; instead we
- -- just generate the saturated constructor directly
- where
- msg = _PK_ ("Compiler error: bad dictionary " ++ showSDoc (ppr clas))
-
- dict_bind = VarMonoBind this_dict_id dict_rhs
- method_binds = andMonoBinds method_binds_s
-
- final_dfun_id = replaceIdInfo dfun_id (prag_info_fn (idName dfun_id))
- -- Pretty truesome
- main_bind
- = AbsBinds
- zonked_inst_tyvars
- dfun_arg_dicts_ids
- [(inst_tyvars', RealId final_dfun_id, this_dict_id)]
- (lie_binds1 `AndMonoBinds`
- lie_binds2 `AndMonoBinds`
- method_binds `AndMonoBinds`
- dict_bind)
- in
- returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie,
- main_bind `AndMonoBinds` prag_binds)
+ returnM (meth_ids, lie_binds `unionBags` listToBag meth_binds)
+
+ 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, 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{Checking for a decent instance type}
+\subsection{Error messages}
%* *
%************************************************************************
-@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.
-
-We can also have instances for functions: @instance Foo (a -> b) ...@.
-
\begin{code}
-scrutiniseInstanceConstraint (clas, tys)
- | all isTyVarTy tys = returnNF_Tc ()
- | otherwise = addErrTc (instConstraintErr clas tys)
-
-scrutiniseInstanceHead clas inst_taus
- | -- CCALL CHECK (a).... urgh!
- -- To verify that a user declaration of a CCallable/CReturnable
- -- instance is OK, we must be able to see the constructor(s)
- -- of the instance type (see next guard.)
- --
- -- We flag this separately to give a more precise error msg.
- --
- (uniqueOf clas == cCallableClassKey || uniqueOf clas == cReturnableClassKey)
- && is_alg_tycon_app && not constructors_visible
- = addErrTc (invisibleDataConPrimCCallErr clas first_inst_tau)
-
- | -- CCALL CHECK (b)
- -- A user declaration of a CCallable/CReturnable instance
- -- must be for a "boxed primitive" type.
- (uniqueOf clas == cCallableClassKey && not (ccallable_type first_inst_tau)) ||
- (uniqueOf clas == 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
-
- -- WITH HASKELL 1.4, MUST HAVE C (T a b c)
- | not opt_GlasgowExts
- && 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 (tyVarSetToList (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 ()
-
+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
- (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
- is_alg_tycon_app = maybeToBool alg_tycon_app_maybe
- Just (alg_tycon, _, data_cons) = alg_tycon_app_maybe
-
- constructors_visible = not (null data_cons)
-
+ (_,_,cls,tys) = tcSplitDFunTy dfun_ty
--- These conditions come directly from what the DsCCall is capable of.
--- Totally grotesque. Green card should solve this.
+inst_decl_ctxt doc = ptext SLIT("In the instance declaration for") <+> quotes doc
-ccallable_type ty = isUnpointedType ty || -- Allow CCallable Int# etc
- maybeToBool (maybeBoxedPrimType ty) || -- Ditto Int etc
- ty == stringTy ||
- byte_arr_thing
- where
- byte_arr_thing = case splitAlgTyConApp_maybe ty of
- Just (tycon, ty_args, [data_con]) | isDataTyCon tycon ->
- length data_con_arg_tys == 2 &&
- maybeToBool maybe_arg2_tycon &&
- (arg2_tycon == byteArrayPrimTyCon ||
- arg2_tycon == mutableByteArrayPrimTyCon)
- where
- data_con_arg_tys = dataConArgTys data_con ty_args
- (data_con_arg_ty1 : data_con_arg_ty2 : _) = data_con_arg_tys
- maybe_arg2_tycon = splitTyConApp_maybe data_con_arg_ty2
- Just (arg2_tycon,_) = maybe_arg2_tycon
-
- other -> False
-
-creturnable_type ty = maybeToBool (maybeBoxedPrimType ty) ||
- -- Or, a data type with a single nullary constructor
- case (splitAlgTyConApp_maybe ty) of
- Just (tycon, tys_applied, [data_con])
- -> isNullaryDataCon data_con
- other -> False
-\end{code}
-
-\begin{code}
-instConstraintErr clas tys
- = hang (ptext SLIT("Illegal constaint") <+>
- 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"))
-
-nonBoxedPrimCCallErr clas inst_ty
- = hang (ptext SLIT("Unacceptable instance type for ccall-ish class"))
- 4 (hsep [ ptext SLIT("class"), ppr clas, ptext SLIT("type"),
- ppr inst_ty])
-
-{-
- Declaring CCallable & CReturnable instances in a module different
- from where the type was defined. Caused by importing data type
- abstractly (either programmatically or by the renamer being over-eager
- in its pruning.)
--}
-invisibleDataConPrimCCallErr clas inst_ty
- = hang (hsep [ptext SLIT("Constructors for"), quotes (ppr inst_ty),
- ptext SLIT("not visible when checking"),
- quotes (ppr clas), ptext SLIT("instance")])
- 4 (hsep [text "(Try either importing", ppr inst_ty,
- text "non-abstractly or compile using -fno-prune-tydecls ..)"])
-
-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