\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
-module TcInstDcls ( tcInstDecls1, tcIfaceInstDecls1, addInstDFuns,
- tcInstDecls2, initInstEnv, tcAddDeclCtxt ) where
+module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where
#include "HsVersions.h"
-
-import CmdLineOpts ( DynFlag(..) )
-
-import HsSyn ( InstDecl(..), TyClDecl(..), HsType(..),
- MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..),
- andMonoBindList, collectMonoBinders,
- isClassDecl, toHsType
- )
-import RnHsSyn ( RenamedHsBinds, RenamedInstDecl,
- RenamedMonoBinds, RenamedTyClDecl, RenamedHsType,
- extractHsTyVars, maybeGenericMatch
- )
-import TcHsSyn ( TcMonoBinds, mkHsConApp )
+import HsSyn
import TcBinds ( tcSpecSigs )
-import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr )
-import TcMonad
+import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr,
+ tcClassDecl2, getGenericInstances )
+import TcRnMonad
import TcMType ( tcInstType, checkValidTheta, checkValidInstHead, instTypeErr,
- UserTypeCtxt(..), SourceTyCtxt(..) )
-import TcType ( mkClassPred, mkTyVarTy, tcSplitForAllTys,
- tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe,
- TyVarDetails(..)
- )
-import Inst ( InstOrigin(..), newDicts, instToId,
- LIE, mkLIE, emptyLIE, plusLIE, plusLIEs )
+ checkAmbiguity, SourceTyCtxt(..) )
+import TcType ( mkClassPred, tcSplitForAllTys, tyVarsOfType,
+ tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe, mkTyVarTys,
+ TyVarDetails(..), tcSplitDFunTy, pprClassPred )
+import Inst ( tcInstClassOp, newDicts, instToId, showLIE, tcExtendLocalInstEnv )
import TcDeriv ( tcDeriving )
-import TcEnv ( tcExtendGlobalValEnv, tcExtendLocalValEnv2,
- tcLookupId, tcLookupClass, tcExtendTyVarEnv2,
- InstInfo(..), pprInstInfo, simpleInstInfoTyCon,
- simpleInstInfoTy, newDFunName
+import TcEnv ( tcExtendGlobalValEnv, tcExtendTyVarEnv2,
+ InstInfo(..), InstBindings(..),
+ newDFunName, tcExtendLocalValEnv
)
-import InstEnv ( InstEnv, extendInstEnv )
-import PprType ( pprClassPred )
-import TcMonoType ( tcSigPolyId, tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType )
+import TcHsType ( kcHsSigType, tcHsKindedType )
import TcUnify ( checkSigTyVars )
-import TcSimplify ( tcSimplifyCheck )
-import HscTypes ( HomeSymbolTable, DFunId, FixityEnv,
- PersistentCompilerState(..), PersistentRenamerState,
- ModDetails(..)
- )
-import Subst ( mkTyVarSubst, substTheta )
+import TcSimplify ( tcSimplifyCheck, tcSimplifyTop )
+import Subst ( mkTyVarSubst, substTheta, substTy )
import DataCon ( classDataCon )
-import Class ( Class, classBigSig )
-import Var ( idName, idType )
-import Id ( setIdLocalExported )
-import MkId ( mkDictFunId, unsafeCoerceId, eRROR_ID )
+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 TyCon ( TyCon )
-import TysWiredIn ( genericTyCons )
-import SrcLoc ( SrcLoc )
-import Unique ( Uniquable(..) )
-import Util ( lengthExceeds, isSingleton )
-import BasicTypes ( NewOrData(..) )
-import ErrUtils ( dumpIfSet_dyn )
-import ListSetOps ( Assoc, emptyAssoc, plusAssoc_C, mapAssoc,
- assocElts, extendAssoc_C, equivClassesByUniq, minusList
- )
+import Name ( Name, getSrcLoc )
+import NameSet ( unitNameSet, emptyNameSet, nameSetToList, unionNameSets )
+import UnicodeUtil ( stringToUtf8 )
import Maybe ( catMaybes )
+import SrcLoc ( srcLocSpan, unLoc, noLoc, Located(..), srcSpanStart )
+import ListSetOps ( minusList )
import Outputable
+import Bag
+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 -- Deal with source-code instance decls
- :: PersistentRenamerState
- -> InstEnv -- Imported instance envt
- -> FixityEnv -- for deriving Show and Read
- -> Module -- Module for deriving
- -> [RenamedTyClDecl] -- For deriving stuff
- -> [RenamedInstDecl] -- Source code instance decls
- -> TcM (InstEnv, -- the full inst env
- [InstInfo], -- instance decls to process; contains all dfuns
- -- for this module
- RenamedHsBinds) -- derived instances
-
-tcInstDecls1 prs inst_env get_fixity this_mod
- tycl_decls inst_decls
--- The incoming inst_env includes all the imported instances already
- = checkNoErrsTc $
+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
+ [HsBindGroup 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 tcLocalInstDecl1 inst_decls `thenNF_Tc` \ local_inst_infos ->
+ mappM tcLocalInstDecl1 inst_decls `thenM` \ local_inst_infos ->
let
local_inst_info = catMaybes local_inst_infos
- clas_decls = filter isClassDecl tycl_decls
+ 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) imported instance decls (from this module) inst_env1
- -- b) local instance decls inst_env2
- -- c) generic instances final_inst_env
- addInstInfos inst_env local_inst_info `thenNF_Tc` \ inst_env1 ->
- addInstInfos inst_env1 generic_inst_info `thenNF_Tc` \ inst_env2 ->
+ -- 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; hence inst_env4
- tcDeriving prs this_mod inst_env2
- get_fixity tycl_decls `thenTc` \ (deriv_inst_info, deriv_binds) ->
- addInstInfos inst_env2 deriv_inst_info `thenNF_Tc` \ final_inst_env ->
-
- returnTc (final_inst_env,
- generic_inst_info ++ deriv_inst_info ++ local_inst_info,
- deriv_binds)
-
-initInstEnv :: PersistentCompilerState -> HomeSymbolTable -> NF_TcM InstEnv
--- Initialise the instance environment from the
--- persistent compiler state and the home symbol table
-initInstEnv pcs hst
- = let
- pkg_inst_env = pcs_insts pcs
- hst_dfuns = foldModuleEnv ((++) . md_insts) [] hst
- in
- addInstDFuns pkg_inst_env hst_dfuns
+ tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds, keep_alive) ->
+ addInsts deriv_inst_info $
-addInstInfos :: InstEnv -> [InstInfo] -> NF_TcM InstEnv
-addInstInfos inst_env infos = addInstDFuns inst_env (map iDFunId infos)
+ getGblEnv `thenM` \ gbl_env ->
+ returnM (gbl_env { tcg_keep = tcg_keep gbl_env `unionNameSets` keep_alive },
+ generic_inst_info ++ deriv_inst_info ++ local_inst_info,
+ deriv_binds)
-addInstDFuns :: InstEnv -> [DFunId] -> NF_TcM InstEnv
-addInstDFuns inst_env dfuns
- = getDOptsTc `thenNF_Tc` \ 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)
+addInsts :: [InstInfo] -> TcM a -> TcM a
+addInsts infos thing_inside
+ = tcExtendLocalInstEnv (map iDFunId infos) thing_inside
\end{code}
\begin{code}
-tcIfaceInstDecls1 :: [RenamedInstDecl] -> NF_TcM [DFunId]
-tcIfaceInstDecls1 decls = mapNF_Tc tcIfaceInstDecl1 decls
-
-tcIfaceInstDecl1 :: RenamedInstDecl -> NF_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
-tcIfaceInstDecl1 decl@(InstDecl poly_ty binds uprags (Just dfun_name) src_loc)
- = tcLookupId dfun_name
-
-
-tcLocalInstDecl1 :: RenamedInstDecl
- -> NF_TcM (Maybe InstInfo) -- Nothing if there was an error
+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"
--
-- 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)
+tcLocalInstDecl1 decl@(L loc (InstDecl poly_ty binds uprags))
= -- Prime error recovery, set source location
- recoverNF_Tc (returnNF_Tc Nothing) $
- tcAddSrcLoc src_loc $
- tcAddErrCtxt (instDeclCtxt poly_ty) $
+ recoverM (returnM Nothing) $
+ addSrcSpan 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'
in
- checkValidTheta InstThetaCtxt theta `thenTc_`
- checkValidInstHead tau `thenTc` \ (clas,inst_tys) ->
+ 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) `thenTc_`
- newDFunName clas inst_tys src_loc `thenNF_Tc` \ dfun_name ->
- returnTc (Just (InstInfo { iDFunId = mkDictFunId dfun_name clas tyvars inst_tys theta,
- iBinds = binds, iPrags = uprags }))
+ (instTypeErr (pprClassPred clas inst_tys) msg) `thenM_`
+ newDFunName clas inst_tys (srcSpanStart 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}
%************************************************************************
%* *
-\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 `thenNF_Tc` \ 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]
- in
- checkTc (null missing) (missingGenericInstances missing) `thenTc_`
-
- returnTc inst_infos
-
- where
- -- Group the declarations by type pattern
- groups :: [(RenamedHsType, RenamedMonoBinds)]
- groups = assocElts (getGenericBinds def_methods)
-
-
----------------------------------
-getGenericBinds :: RenamedMonoBinds -> Assoc RenamedHsType RenamedMonoBinds
- -- Takes a group of method bindings, finds the generic ones, and returns
- -- them in finite map indexed by the type parameter in the definition.
-
-getGenericBinds EmptyMonoBinds = emptyAssoc
-getGenericBinds (AndMonoBinds m1 m2)
- = plusAssoc_C AndMonoBinds (getGenericBinds m1) (getGenericBinds m2)
-
-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]
- dfun_id = mkDictFunId dfun_name clas tyvars [inst_ty] inst_theta
- in
-
- returnTc (InstInfo { iDFunId = dfun_id, iBinds = binds, iPrags = [] })
-\end{code}
-
-
-%************************************************************************
-%* *
\subsection{Type-checking instance declarations, pass 2}
%* *
%************************************************************************
\begin{code}
-tcInstDecls2 :: [InstInfo]
- -> NF_TcM (LIE, TcMonoBinds)
+tcInstDecls2 :: [LTyClDecl Name] -> [InstInfo]
+ -> TcM (TcLclEnv, LHsBinds Id)
+-- (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
+ ; tcExtendLocalValEnv (concat dm_ids_s) $ do
+
+ -- (b) instance declarations
+ ; inst_binds_s <- mappM tcInstDecl2 inst_decls
-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)
+ -- Done
+ ; tcl_env <- getLclEnv
+ ; returnM (tcl_env, unionManyBags dm_binds_s `unionBags`
+ unionManyBags inst_binds_s) }
\end{code}
======= New documentation starts here (Sept 92) ==============
\begin{code}
-tcInstDecl2 :: InstInfo -> TcM (LIE, TcMonoBinds)
+tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id)
-tcInstDecl2 (NewTypeDerived { iDFunId = dfun_id })
- = tcInstType InstTv (idType dfun_id) `thenNF_Tc` \ (inst_tyvars', dfun_theta', inst_head') ->
- newDicts InstanceDeclOrigin dfun_theta' `thenNF_Tc` \ rep_dicts ->
- let
- rep_dict_id = ASSERT( isSingleton rep_dicts )
- instToId (head rep_dicts) -- Derived newtypes have just one dict arg
-
- body = TyLam inst_tyvars' $
- DictLam [rep_dict_id] $
- (HsVar unsafeCoerceId `TyApp` [idType rep_dict_id, inst_head'])
- `HsApp`
- (HsVar rep_dict_id)
- -- You might wonder why we have the 'coerce'. It's because the
- -- type equality mechanism isn't clever enough; see comments with Type.eqType.
- -- So Lint complains if we don't have this.
- in
- returnTc (emptyLIE, VarMonoBind dfun_id body)
-
-tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = monobinds, iPrags = uprags })
+tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds })
= -- Prime error recovery
- recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
- tcAddSrcLoc (getSrcLoc dfun_id) $
- tcAddErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $
+ recoverM (returnM emptyBag) $
+ addSrcSpan (srcLocSpan (getSrcLoc dfun_id)) $
+ addErrCtxt (instDeclCtxt2 (idType dfun_id)) $
let
- inst_ty = idType dfun_id
+ 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
in
-- Instantiate the instance decl with tc-style type variables
- tcInstType InstTv inst_ty `thenNF_Tc` \ (inst_tyvars', dfun_theta', inst_head') ->
+ tcInstType InstTv inst_ty `thenM` \ (inst_tyvars', dfun_theta', inst_head') ->
let
Just pred = tcSplitPredTy_maybe inst_head'
(clas, inst_tys') = getClassPredTys pred
(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 (mkTyVarSubst class_tyvars inst_tys') sc_theta
-
- -- Find any definitions in monobinds that aren't from the class
- bad_bndrs = collectMonoBinders monobinds `minusList` sel_names
origin = InstanceDeclOrigin
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] ->
+ 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.
- mapAndUnzipTc (mkMethodBind origin clas inst_tys' monobinds)
- op_items `thenTc` \ (meth_insts, meth_infos) ->
-
- let
- -- These insts are in scope; quite a few, eh?
- avail_insts = [this_dict] ++
- dfun_arg_dicts ++
- sc_dicts ++
- meth_insts
-
- xtve = inst_tyvars `zip` inst_tyvars'
- tc_meth = tcMethodBind xtve inst_tyvars' dfun_theta' avail_insts
+ ------------------
+ -- Typecheck the methods
+ let -- These insts are in scope; quite a few, eh?
+ avail_insts = [this_dict] ++ dfun_arg_dicts ++ sc_dicts
in
- mapAndUnzipTc tc_meth meth_infos `thenTc` \ (meth_binds_s, meth_lie_s) ->
+ tcMethods clas inst_tyvars inst_tyvars'
+ dfun_theta' inst_tys' avail_insts
+ op_items binds `thenM` \ (meth_ids, meth_binds) ->
-- Figure out bindings for the superclass context
- tcAddErrCtxt superClassCtxt $
- tcSimplifyCheck
- (ptext SLIT("instance declaration superclass 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` \ (sc_lie, sc_binds) ->
- -- It's possible that the superclass stuff might have done unification
- checkSigTyVars inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars ->
+ tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts
+ `thenM` \ (zonked_inst_tyvars, sc_binds_inner, sc_binds_outer) ->
- -- Deal with SPECIALISE instance pragmas by making them
+ -- Deal with 'SPECIALISE instance' pragmas by making them
-- look like SPECIALISE pragmas for the dfun
let
- mk_prag (SpecInstSig ty loc) = SpecSig (idName dfun_id) ty loc
- mk_prag prag = prag
-
- all_prags = map mk_prag uprags
+ uprags = case binds of
+ VanillaInst _ uprags -> uprags
+ other -> []
+ spec_prags = [ L loc (SpecSig (L loc (idName dfun_id)) ty)
+ | L loc (SpecInstSig ty) <- uprags ]
+ xtve = inst_tyvars `zip` inst_tyvars'
in
-
tcExtendGlobalValEnv [dfun_id] (
- tcExtendTyVarEnv2 xtve $
- tcExtendLocalValEnv2 [(idName sel_id, tcSigPolyId sig)
- | (sel_id, sig, _) <- meth_infos] $
- -- Map sel_id to the local method name we are using
- tcSpecSigs all_prags
- ) `thenTc` \ (prag_binds, prag_lie) ->
+ tcExtendTyVarEnv2 xtve $
+ tcSpecSigs spec_prags
+ ) `thenM` \ prag_binds ->
-- Create the result bindings
let
- local_dfun_id = setIdLocalExported dfun_id
- -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId
-
dict_constr = classDataCon clas
- scs_and_meths = 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)
-- BUT: don't inline it if it's a constant dictionary;
-- we'll get all the benefit without inlining, and we get
-- a **lot** of code duplication if we inline it
+ --
+ -- See Note [Inline dfuns] below
dict_rhs
| null scs_and_meths
-- emit an error message. This in turn means that we don't
-- mention the constructor, which doesn't exist for CCallable, CReturnable
-- Hardly beautiful, but only three extra lines.
- HsApp (TyApp (HsVar eRROR_ID) [idType this_dict_id])
- (HsLit (HsString msg))
+ nlHsApp (noLoc $ TyApp (nlHsVar rUNTIME_ERROR_ID)
+ [idType this_dict_id])
+ (nlHsLit (HsStringPrim (mkFastString (stringToUtf8 msg))))
| otherwise -- The common case
= mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths)
-- than needing to be repeated here.
where
- msg = _PK_ ("Compiler error: bad dictionary " ++ showSDoc (ppr clas))
+ msg = "Compiler error: bad dictionary " ++ showSDoc (ppr clas)
- dict_bind = VarMonoBind this_dict_id dict_rhs
- meth_binds = andMonoBindList meth_binds_s
- all_binds = sc_binds `AndMonoBinds` meth_binds `AndMonoBinds` dict_bind
+ dict_bind = noLoc (VarBind this_dict_id dict_rhs)
+ all_binds = dict_bind `consBag` (sc_binds_inner `unionBags` meth_binds)
- main_bind = AbsBinds
+ main_bind = noLoc $ AbsBinds
zonked_inst_tyvars
(map instToId dfun_arg_dicts)
- [(inst_tyvars', local_dfun_id, this_dict_id)]
+ [(inst_tyvars', dfun_id, this_dict_id)]
inlines all_binds
in
- returnTc (plusLIEs meth_lie_s `plusLIE` sc_lie `plusLIE` prag_lie,
- main_bind `AndMonoBinds` prag_binds)
+ showLIE (text "instance") `thenM_`
+ returnM (unitBag main_bind `unionBags`
+ prag_binds `unionBags`
+ sc_binds_outer)
+
+
+tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys'
+ avail_insts op_items (VanillaInst monobinds uprags)
+ = -- Check that all the method bindings come from this class
+ let
+ sel_names = [idName sel_id | (sel_id, _) <- op_items]
+ bad_bndrs = collectHsBindBinders monobinds `minusList` sel_names
+ in
+ mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_`
+
+ -- Make the method bindings
+ let
+ mk_method_bind = mkMethodBind InstanceDeclOrigin 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
+ all_insts = avail_insts ++ catMaybes 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 ([meth_id | (_,meth_id,_) <- meth_infos],
+ unionManyBags meth_binds_s)
+
+
+-- 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 ->
+
+ -- 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
+ rep_tys' = map (substTy subst) rep_tys
+ subst = mkTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars')
\end{code}
+Note: [Superclass loops]
+~~~~~~~~~~~~~~~~~~~~~~~~~
+We have to be very, very careful when generating superclasses, lest we
+accidentally build a loop. Here's an example:
+
+ class S a
+
+ class S a => C a where { opc :: a -> a }
+ class S b => D b where { opd :: b -> b }
+
+ instance C Int where
+ opc = opd
+
+ instance D Int where
+ opd = opc
+
+From (instance C Int) we get the constraint set {ds1:S Int, dd:D Int}
+Simplifying, we may well get:
+ $dfCInt = :C ds1 (opd dd)
+ dd = $dfDInt
+ ds1 = $p1 dd
+Notice that we spot that we can extract ds1 from dd.
+
+Alas! Alack! We can do the same for (instance D Int):
+
+ $dfDInt = :D ds2 (opc dc)
+ dc = $dfCInt
+ ds2 = $p1 dc
+
+And now we've defined the superclass in terms of itself.
+
+
+Solution: treat the superclass context separately, and simplify it
+all the way down to nothing on its own. Don't toss any 'free' parts
+out to be simplified together with other bits of context.
+Hence the tcSimplifyTop below.
+
+At a more basic level, don't include this_dict in the context wrt
+which we simplify sc_dicts, else sc_dicts get bound by just selecting
+from this_dict!!
+
+\begin{code}
+tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts
+ = addErrCtxt superClassCtxt $
+ getLIE (tcSimplifyCheck doc inst_tyvars'
+ dfun_arg_dicts
+ sc_dicts) `thenM` \ (sc_binds1, sc_lie) ->
+
+ -- It's possible that the superclass stuff might have done unification
+ checkSigTyVars inst_tyvars' `thenM` \ zonked_inst_tyvars ->
+
+ -- We must simplify this all the way down
+ -- lest we build superclass loops
+ -- See Note [Superclass loops] above
+ tcSimplifyTop sc_lie `thenM` \ sc_binds2 ->
+
+ returnM (zonked_inst_tyvars, sc_binds1, sc_binds2)
+
+ where
+ doc = ptext SLIT("instance declaration superclass context")
+\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}