\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
-module TcInstDcls ( tcInstDecls1, tcInstDecls2, tcAddDeclCtxt ) where
+module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where
#include "HsVersions.h"
-
-import CmdLineOpts ( DynFlag(..) )
-
-import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..), HsType(..),
- MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..),
- andMonoBindList, collectMonoBinders, isClassDecl, toHsType
- )
-import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl,
- RenamedMonoBinds, RenamedTyClDecl, RenamedHsType,
- extractHsTyVars, maybeGenericMatch
- )
-import TcHsSyn ( TcMonoBinds, mkHsConApp )
-import TcBinds ( tcSpecSigs )
-import TcClassDcl ( tcMethodBind, badMethodErr )
-import TcMonad
-import TcMType ( tcInstSigTyVars, checkValidTheta, checkValidInstHead, instTypeErr,
- UserTypeCtxt(..), SourceTyCtxt(..) )
-import TcType ( tcSplitDFunTy, mkClassPred, mkTyVarTy, mkTyVarTys,
- tcSplitSigmaTy, tcSplitPredTy_maybe, getClassPredTys,
- TyVarDetails(..)
- )
-import Inst ( InstOrigin(..),
- newDicts, instToId,
- LIE, mkLIE, 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,
- tcAddImportedIdInfo, tcLookupClass,
- InstInfo(..), pprInstInfo, simpleInstInfoTyCon,
- simpleInstInfoTy, newDFunName,
- isLocalThing,
+import TcEnv ( InstInfo(..), InstBindings(..),
+ newDFunName, tcExtendIdEnv
)
-import InstEnv ( InstEnv, extendInstEnv )
-import PprType ( pprClassPred )
-import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType )
+import TcHsType ( kcHsSigType, tcHsKindedType )
import TcUnify ( checkSigTyVars )
-import TcSimplify ( tcSimplifyCheck )
-import HscTypes ( HomeSymbolTable, DFunId,
- ModDetails(..), PackageInstEnv, PersistentRenamerState
- )
-
-import Subst ( substTy, substTheta )
+import TcSimplify ( tcSimplifyCheck, tcSimplifySuperClasses )
+import Type ( zipOpenTvSubst, substTheta, substTys )
import DataCon ( classDataCon )
-import Class ( Class, classBigSig )
-import Var ( idName, idType )
-import VarSet ( emptyVarSet )
-import Id ( setIdLocalExported )
-import MkId ( mkDictFunId )
+import Class ( classBigSig )
+import Var ( Id, idName, idType )
+import MkId ( mkDictFunId, rUNTIME_ERROR_ID )
import FunDeps ( checkInstFDs )
-import Generics ( validGenericInstanceType )
-import Module ( Module, foldModuleEnv )
-import Name ( getSrcLoc )
-import NameSet ( unitNameSet, emptyNameSet, nameSetToList )
-import PrelInfo ( eRROR_ID )
-import TyCon ( TyCon )
-import Subst ( mkTopTyVarSubst, substTheta )
-import TysWiredIn ( genericTyCons )
-import Name ( Name )
-import SrcLoc ( SrcLoc )
-import Unique ( Uniquable(..) )
-import Util ( lengthExceeds )
-import BasicTypes ( NewOrData(..), Fixity )
-import ErrUtils ( dumpIfSet_dyn )
-import ListSetOps ( Assoc, emptyAssoc, plusAssoc_C, mapAssoc,
- assocElts, extendAssoc_C,
- equivClassesByUniq, minusList
- )
-import List ( partition )
+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 :: PackageInstEnv
- -> PersistentRenamerState
- -> HomeSymbolTable -- Contains instances
- -> TcEnv -- Contains IdInfo for dfun ids
- -> (Name -> Maybe Fixity) -- for deriving Show and Read
- -> Module -- Module for deriving
- -> [RenamedHsDecl]
- -> TcM (PackageInstEnv, InstEnv, [InstInfo], RenamedHsBinds)
-
-tcInstDecls1 inst_env0 prs hst unf_env get_fixity this_mod decls
- = let
- inst_decls = [inst_decl | InstD inst_decl <- decls]
- tycl_decls = [decl | TyClD decl <- decls]
- clas_decls = filter isClassDecl tycl_decls
- in
+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 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 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 (isLocalThing this_mod . iDFunId) (concat inst_infos)
-
- imported_dfuns = map (tcAddImportedIdInfo unf_env . iDFunId)
- imported_inst_info
- hst_dfuns = foldModuleEnv ((++) . md_insts) [] hst
- in
-
--- pprTrace "tcInstDecls" (vcat [ppr imported_dfuns, ppr hst_dfuns]) $
-
- addInstDFuns inst_env0 imported_dfuns `thenNF_Tc` \ inst_env1 ->
- addInstDFuns inst_env1 hst_dfuns `thenNF_Tc` \ inst_env2 ->
- addInstInfos inst_env2 local_inst_info `thenNF_Tc` \ inst_env3 ->
- addInstInfos inst_env3 generic_inst_info `thenNF_Tc` \ inst_env4 ->
+ -- 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 prs this_mod inst_env4 get_fixity tycl_decls
- `thenTc` \ (deriv_inst_info, deriv_binds) ->
- addInstInfos inst_env4 deriv_inst_info `thenNF_Tc` \ final_inst_env ->
-
- returnTc (inst_env1,
- final_inst_env,
- generic_inst_info ++ deriv_inst_info ++ local_inst_info,
- deriv_binds)
-
-addInstInfos :: InstEnv -> [InstInfo] -> NF_TcM InstEnv
-addInstInfos inst_env infos = addInstDFuns inst_env (map iDFunId infos)
-
-addInstDFuns :: InstEnv -> [DFunId] -> NF_TcM InstEnv
-addInstDFuns inst_env dfuns
- = getDOptsTc `thenTc` \ dflags ->
- let
- (inst_env', errs) = extendInstEnv dflags inst_env dfuns
- in
- addErrsTc errs `thenNF_Tc_`
- traceTc (text "Adding instances:" <+> vcat (map pp dfuns)) `thenTc_`
- returnTc inst_env'
- where
- pp dfun = ppr dfun <+> dcolon <+> ppr (idType dfun)
+ -- 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 :: RenamedInstDecl -> NF_TcM [InstInfo]
--- Deal with a single instance declaration
--- Type-check all the stuff before the "where"
-tcInstDecl1 decl@(InstDecl poly_ty binds uprags maybe_dfun_name src_loc)
- = -- Prime error recovery, set source location
- recoverNF_Tc (returnNF_Tc []) $
- tcAddSrcLoc src_loc $
- tcAddErrCtxt (instDeclCtxt poly_ty) $
+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"
+ --
+ -- 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 `thenTc_`
- tcHsType poly_ty `thenTc` \ poly_ty' ->
+ kcHsSigType poly_ty `thenM` \ kinded_ty ->
+ tcHsKindedType kinded_ty `thenM` \ poly_ty' ->
let
(tyvars, theta, tau) = tcSplitSigmaTy poly_ty'
- (clas,inst_tys) = case tcSplitPredTy_maybe tau of { Just st -> getClassPredTys st }
- -- The checkValidInstHead makes sure these splits succeed
- 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]
- checkValidTheta InstThetaCtxt theta `thenTc_`
- checkValidInstHead tau `thenTc_`
- checkTc (checkInstFDs theta clas inst_tys)
- (instTypeErr (pprClassPred clas inst_tys) msg) `thenTc_`
- newDFunName clas inst_tys src_loc
-
- Just dfun_name -> -- An interface-file instance declaration
- returnNF_Tc dfun_name
- ) `thenNF_Tc` \ dfun_name ->
- let
- dfun_id = mkDictFunId dfun_name clas tyvars inst_tys theta
- in
- returnTc [InstInfo { iDFunId = dfun_id, iBinds = binds, iPrags = uprags }]
- where
- msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class"))
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection{Extracting generic instance declaration from class declarations}
-%* *
-%************************************************************************
-
-@getGenericInstances@ extracts the generic instance declarations from a class
-declaration. For exmaple
-
- class C a where
- op :: a -> a
-
- op{ x+y } (Inl v) = ...
- op{ x+y } (Inr v) = ...
- op{ x*y } (v :*: w) = ...
- op{ 1 } Unit = ...
-
-gives rise to the instance declarations
-
- instance C (x+y) where
- op (Inl v) = ...
- op (Inr v) = ...
-
- instance C (x*y) where
- op (v :*: w) = ...
-
- instance C 1 where
- op Unit = ...
-
-
-\begin{code}
-getGenericInstances :: [RenamedTyClDecl] -> TcM [InstInfo]
-getGenericInstances class_decls
- = mapTc get_generics class_decls `thenTc` \ gen_inst_infos ->
- let
- gen_inst_info = concat gen_inst_infos
in
- if null gen_inst_info then
- returnTc []
- else
- getDOptsTc `thenTc` \ dflags ->
- ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances"
- (vcat (map pprInstInfo gen_inst_info)))
- `thenNF_Tc_`
- returnTc gen_inst_info
-
-get_generics decl@(ClassDecl {tcdMeths = Nothing})
- = returnTc [] -- Imported class decls
-
-get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, tcdLoc = loc})
- | null groups
- = returnTc [] -- The comon case: no generic default methods
-
- | otherwise -- A source class decl with generic default methods
- = recoverNF_Tc (returnNF_Tc []) $
- tcAddDeclCtxt decl $
- tcLookupClass class_name `thenTc` \ clas ->
-
- -- Make an InstInfo out of each group
- mapTc (mkGenericInstance clas loc) groups `thenTc` \ inst_infos ->
-
- -- Check that there is only one InstInfo for each type constructor
- -- The main way this can fail is if you write
- -- f {| a+b |} ... = ...
- -- f {| x+y |} ... = ...
- -- Then at this point we'll have an InstInfo for each
- let
- tc_inst_infos :: [(TyCon, InstInfo)]
- tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos]
-
- bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos,
- group `lengthExceeds` 1]
- get_uniq (tc,_) = getUnique tc
- in
- mapTc (addErrTc . dupGenericInsts) bad_groups `thenTc_`
-
- -- Check that there is an InstInfo for each generic type constructor
- let
- missing = genericTyCons `minusList` [tc | (tc,_) <- tc_inst_infos]
+ 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
+ tcIsHsBoot `thenM` \ is_boot ->
+ checkTc (not is_boot || (isEmptyLHsBinds binds && null uprags))
+ badBootDeclErr `thenM_`
+ returnM (Just (InstInfo { iSpec = ispec, iBinds = VanillaInst binds uprags }))
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 `thenTc` \ inst_ty ->
- checkTc (validGenericInstanceType inst_ty)
- (badGenericInstanceType binds) `thenTc_`
-
- -- Make the dictionary function.
- newDFunName clas [inst_ty] loc `thenNF_Tc` \ dfun_name ->
- let
- inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars]
- inst_tys = [inst_ty]
- dfun_id = mkDictFunId dfun_name clas tyvars inst_tys inst_theta
- in
-
- returnTc (InstInfo { iDFunId = dfun_id,
- iBinds = binds, 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) ==============
\begin{code}
-tcInstDecl2 :: InstInfo -> NF_TcM (LIE, TcMonoBinds)
--- tcInstDecl2 is called *only* on InstInfos
+tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id)
-tcInstDecl2 (InstInfo { iDFunId = dfun_id,
- iBinds = monobinds, iPrags = uprags })
- = -- Prime error recovery
- recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
- tcAddSrcLoc (getSrcLoc dfun_id) $
- tcAddErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $
-
- -- Instantiate the instance decl with tc-style type variables
- let
- (inst_tyvars, dfun_theta, clas, inst_tys) = tcSplitDFunTy (idType dfun_id)
+tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = binds })
+ = let
+ dfun_id = instanceDFunId ispec
+ rigid_info = InstSkol dfun_id
+ inst_ty = idType dfun_id
in
- tcInstSigTyVars InstTv inst_tyvars `thenNF_Tc` \ inst_tyvars' ->
+ -- 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
- tenv = mkTopTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars')
- inst_tys' = map (substTy tenv) inst_tys
- dfun_theta' = substTheta tenv dfun_theta
- origin = InstanceDeclOrigin
-
+ (clas, inst_tys') = tcSplitDFunHead inst_head'
(class_tyvars, sc_theta, _, op_items) = classBigSig clas
- sel_names = [idName sel_id | (sel_id, _) <- op_items]
-
-- Instantiate the super-class context with inst_tys
- sc_theta' = substTheta (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.
- newDicts origin sc_theta' `thenNF_Tc` \ sc_dicts ->
- newDicts origin dfun_theta' `thenNF_Tc` \ dfun_arg_dicts ->
- newDicts origin [mkClassPred clas inst_tys'] `thenNF_Tc` \ [this_dict] ->
-
- tcExtendTyVarEnvForMeths inst_tyvars inst_tyvars' (
- -- The type variable from the dict fun actually scope
- -- over the bindings. They were gotten from
- -- the original instance declaration
-
+ 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.
- mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys'
- dfun_theta'
- monobinds uprags True)
- op_items
- ) `thenTc` \ (method_binds_s, insts_needed_s, meth_insts) ->
-
- -- Deal with SPECIALISE instance pragmas by making them
- -- look like SPECIALISE pragmas for the dfun
- let
- dfun_prags = [SpecSig (idName dfun_id) ty loc | SpecInstSig ty loc <- uprags]
+ -- Typecheck the methods
+ let -- These insts are in scope; quite a few, eh?
+ avail_insts = [this_dict] ++ dfun_arg_dicts ++ sc_dicts
in
- tcExtendGlobalValEnv [dfun_id] (
- tcSpecSigs dfun_prags
- ) `thenTc` \ (prag_binds, prag_lie) ->
+ tcMethods origin clas inst_tyvars'
+ dfun_theta' inst_tys' avail_insts
+ op_items binds `thenM` \ (meth_ids, meth_binds) ->
- -- Check the overloading constraints of the methods and superclasses
+ -- Figure out bindings for the superclass context
+ -- 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
- -- These insts are in scope; quite a few, eh?
- avail_insts = [this_dict] ++
- dfun_arg_dicts ++
- sc_dicts ++
- meth_insts
-
- methods_lie = plusLIEs insts_needed_s
+ specs = case binds of
+ VanillaInst _ prags -> filter isSpecInstLSig prags
+ other -> []
in
-
- -- Simplify the constraints from methods
- tcAddErrCtxt methodCtxt (
- tcSimplifyCheck
- (ptext SLIT("instance declaration context"))
- inst_tyvars'
- avail_insts
- methods_lie
- ) `thenTc` \ (const_lie1, lie_binds1) ->
+ tcPrags dfun_id specs `thenM` \ prags ->
- -- Figure out bindings for the superclass context
- tcAddErrCtxt superClassCtxt (
- tcSimplifyCheck
- (ptext SLIT("instance declaration context"))
- inst_tyvars'
- dfun_arg_dicts -- NB! Don't include this_dict here, else the sc_dicts
- -- get bound by just selecting from this_dict!!
- (mkLIE sc_dicts)
- ) `thenTc` \ (const_lie2, lie_binds2) ->
-
- checkSigTyVars inst_tyvars' emptyVarSet `thenNF_Tc` \ zonked_inst_tyvars ->
-
-- Create the result bindings
let
- local_dfun_id = setIdLocalExported dfun_id
- -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId
-
dict_constr = classDataCon clas
- scs_and_meths = map instToId (sc_dicts ++ meth_insts)
+ 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)
+ 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
-- 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) [idType this_dict_id])
- (HsLit (HsString 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
-- 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
- (map instToId dfun_arg_dicts)
- [(inst_tyvars', local_dfun_id, this_dict_id)]
- inlines
- (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
+ showLIE (text "instance") `thenM_`
+ returnM (unitBag main_bind)
+
+
+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
- returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie,
- main_bind `AndMonoBinds` prag_binds)
+ mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_`
+
+ -- Make the method bindings
+ 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)
+
+
+-- 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 ->
+
+ -- I don't think we have to do the checkSigTyVars thing
+
+ 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}
+
------------------------------
- Inlining dfuns unconditionally
+ [Inline dfuns] Inlining dfuns unconditionally
------------------------------
The code above unconditionally inlines dict funs. Here's why.
%************************************************************************
\begin{code}
-tcAddDeclCtxt decl thing_inside
- = tcAddSrcLoc (tcdLoc decl) $
- 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
- 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}
+ (_,_,cls,tys) = tcSplitDFunTy dfun_ty
+
+inst_decl_ctxt doc = ptext SLIT("In the instance declaration for") <+> quotes doc
-\begin{code}
-badGenericInstanceType binds
- = vcat [ptext SLIT("Illegal type pattern in the generic bindings"),
- nest 4 (ppr binds)]
-
-missingGenericInstances missing
- = ptext SLIT("Missing type patterns for") <+> pprQuotedList missing
-
-dupGenericInsts tc_inst_infos
- = vcat [ptext SLIT("More than one type pattern for a single generic type constructor:"),
- nest 4 (vcat (map ppr_inst_ty tc_inst_infos)),
- ptext SLIT("All the type patterns for a generic type constructor must be identical")
- ]
- where
- ppr_inst_ty (tc,inst) = ppr (simpleInstInfoTy inst)
-
-methodCtxt = ptext SLIT("When checking the methods of an instance declaration")
superClassCtxt = ptext SLIT("When checking the super-classes of an instance declaration")
\end{code}
projects / ghc-hetmet.git / blobdiff