\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
-module TcInstDcls ( tcInstDecls1, tcInstDecls2, tcAddDeclCtxt ) where
+module TcInstDcls ( tcInstDecls1, tcIfaceInstDecls,
+ tcInstDecls2, tcAddDeclCtxt ) where
#include "HsVersions.h"
import CmdLineOpts ( DynFlag(..) )
-import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..), HsType(..),
+import HsSyn ( InstDecl(..), TyClDecl(..), HsType(..),
MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..),
andMonoBindList, collectMonoBinders,
- isClassDecl, isIfaceInstDecl, toHsType
+ isClassDecl, isSourceInstDecl, toHsType
)
-import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl,
+import RnHsSyn ( RenamedHsBinds, RenamedInstDecl,
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,
+import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr )
+import TcRnMonad
+import TcMType ( tcInstType, checkValidTheta, checkValidInstHead, instTypeErr,
+ checkAmbiguity, UserTypeCtxt(..), SourceTyCtxt(..) )
+import TcType ( mkClassPred, mkTyVarTy, tcSplitForAllTys, tyVarsOfType,
+ tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe, mkTyVarTys,
TyVarDetails(..)
)
-import Inst ( InstOrigin(..),
- newDicts, instToId,
- LIE, mkLIE, emptyLIE, plusLIE, plusLIEs )
+import Inst ( InstOrigin(..), tcInstClassOp, newDicts, instToId, showLIE )
import TcDeriv ( tcDeriving )
-import TcEnv ( TcEnv, tcExtendGlobalValEnv,
- tcExtendTyVarEnvForMeths, tcLookupId, tcLookupClass,
- InstInfo(..), pprInstInfo, simpleInstInfoTyCon,
+import TcEnv ( tcExtendGlobalValEnv,
+ tcLookupClass, tcExtendTyVarEnv2,
+ tcExtendInstEnv, tcExtendLocalInstEnv, tcLookupGlobalId,
+ InstInfo(..), InstBindings(..), pprInstInfo, simpleInstInfoTyCon,
simpleInstInfoTy, newDFunName
)
-import InstEnv ( InstEnv, extendInstEnv )
import PprType ( pprClassPred )
import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType )
import TcUnify ( checkSigTyVars )
-import TcSimplify ( tcSimplifyCheck )
-import HscTypes ( HomeSymbolTable, DFunId,
- ModDetails(..), PackageInstEnv, PersistentRenamerState
- )
-
-import Subst ( substTy, substTheta )
+import TcSimplify ( tcSimplifyCheck, tcSimplifyTop )
+import HscTypes ( DFunId )
+import Subst ( mkTyVarSubst, substTheta, substTy )
import DataCon ( classDataCon )
import Class ( Class, classBigSig )
import Var ( idName, idType )
-import VarSet ( emptyVarSet )
+import NameSet
import Id ( setIdLocalExported )
-import MkId ( mkDictFunId )
+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 BasicTypes ( NewOrData(..) )
+import UnicodeUtil ( stringToUtf8 )
import ErrUtils ( dumpIfSet_dyn )
import ListSetOps ( Assoc, emptyAssoc, plusAssoc_C, mapAssoc,
- assocElts, extendAssoc_C,
- equivClassesByUniq, minusList
+ assocElts, extendAssoc_C, equivClassesByUniq, minusList
)
-import List ( partition )
+import Maybe ( catMaybes )
+import List ( partition )
import Outputable
+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
- (imported_inst_ds, local_inst_ds) = partition isIfaceInstDecl inst_decls
+tcInstDecls1 -- Deal with both source-code and imported instance decls
+ :: [RenamedTyClDecl] -- For deriving stuff
+ -> [RenamedInstDecl] -- Source code instance decls
+ -> TcM (TcGblEnv, -- The full inst env
+ [InstInfo], -- Source-code instance decls to process;
+ -- contains all dfuns for this module
+ RenamedHsBinds, -- Supporting bindings for derived instances
+ FreeVars) -- And the free vars of the derived code
+
+tcInstDecls1 tycl_decls inst_decls
+ = checkNoErrs $
+ -- Stop if addInstInfos etc discovers any errors
+ -- (they recover, so that we get more than one error each round)
+ let
+ (src_inst_decls, iface_inst_decls) = partition isSourceInstDecl inst_decls
in
+
+ -- (0) Deal with the imported instance decls
+ tcIfaceInstDecls iface_inst_decls `thenM` \ imp_dfuns ->
+ tcExtendInstEnv imp_dfuns $
+
-- (1) Do the ordinary instance declarations
- mapNF_Tc tcInstDecl1 local_inst_ds `thenNF_Tc` \ local_inst_infos ->
- mapNF_Tc tcInstDecl1 imported_inst_ds `thenNF_Tc` \ imported_inst_infos ->
+ mappM tcLocalInstDecl1 src_inst_decls `thenM` \ local_inst_infos ->
+ let
+ local_inst_info = catMaybes local_inst_infos
+ clas_decls = filter isClassDecl 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 = concat local_inst_infos
- imported_inst_info = concat imported_inst_infos
- hst_dfuns = foldModuleEnv ((++) . md_insts) [] hst
- in
-
--- pprTrace "tcInstDecls" (vcat [ppr imported_dfuns, ppr hst_dfuns]) $
-
- addInstInfos inst_env0 imported_inst_info `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) imported instance decls (from this module)
+ -- b) local instance decls
+ -- c) generic instances
+ tcExtendLocalInstEnv local_inst_info $
+ tcExtendLocalInstEnv generic_inst_info $
-- (3) Compute instances from "deriving" clauses;
-- note that we only do derivings for things in this module;
-- we ignore deriving decls from interfaces!
-- This stuff computes a context for the derived instance decl, so it
-- needs to know about all the instances possible; hence inst_env4
- tcDeriving 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)
+ tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds, fvs) ->
+ tcExtendLocalInstEnv deriv_inst_info $
-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)
+ getGblEnv `thenM` \ gbl_env ->
+ returnM (gbl_env,
+ generic_inst_info ++ deriv_inst_info ++ local_inst_info,
+ deriv_binds, fvs)
\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 :: RenamedInstDecl
+ -> TcM (Maybe InstInfo) -- Nothing if there was an error
+ -- A source-file instance declaration
+ -- Type-check all the stuff before the "where"
+ --
+ -- We check for respectable instance type, and context
+ -- but only do this for non-imported instance decls.
+ -- Imported ones should have been checked already, and may indeed
+ -- contain something illegal in normal Haskell, notably
+ -- instance CCallable [Char]
+tcLocalInstDecl1 decl@(InstDecl poly_ty binds uprags Nothing src_loc)
+ = -- Prime error recovery, set source location
+ recoverM (returnM Nothing) $
+ addSrcLoc src_loc $
+ addErrCtxt (instDeclCtxt poly_ty) $
-- Typecheck the instance type itself. We can't use
-- tcHsSigType, because it's not a valid user type.
- kcHsSigType poly_ty `thenTc_`
- tcHsType poly_ty `thenTc` \ poly_ty' ->
+ kcHsSigType poly_ty `thenM_`
+ tcHsType poly_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 `thenTc` \ dfun_name ->
- returnTc (mkDictFunId dfun_name clas tyvars inst_tys theta)
-
- Just dfun_name -> -- 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
- tcLookupId dfun_name
- ) `thenNF_Tc` \ dfun_id ->
- returnTc [InstInfo { iDFunId = dfun_id, iBinds = binds, iPrags = uprags }]
+ checkValidTheta InstThetaCtxt theta `thenM_`
+ checkAmbiguity tyvars theta (tyVarsOfType tau) `thenM_`
+ checkValidInstHead tau `thenM` \ (clas,inst_tys) ->
+ checkTc (checkInstFDs theta clas inst_tys)
+ (instTypeErr (pprClassPred clas inst_tys) msg) `thenM_`
+ newDFunName clas inst_tys src_loc `thenM` \ dfun_name ->
+ returnM (Just (InstInfo { iDFunId = mkDictFunId dfun_name tyvars theta clas inst_tys,
+ iBinds = VanillaInst binds uprags }))
where
msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class"))
\end{code}
+Imported instance declarations
+
+\begin{code}
+tcIfaceInstDecls :: [RenamedInstDecl] -> TcM [DFunId]
+-- Deal with the instance decls,
+tcIfaceInstDecls decls = mappM tcIfaceInstDecl decls
+
+tcIfaceInstDecl :: RenamedInstDecl -> TcM DFunId
+ -- An interface-file instance declaration
+ -- Should be in scope by now, because we should
+ -- have sucked in its interface-file definition
+ -- So it will be replete with its unfolding etc
+tcIfaceInstDecl decl@(InstDecl poly_ty binds uprags (Just dfun_name) src_loc)
+ = tcLookupGlobalId dfun_name
+\end{code}
+
%************************************************************************
%* *
\begin{code}
getGenericInstances :: [RenamedTyClDecl] -> TcM [InstInfo]
getGenericInstances class_decls
- = mapTc get_generics class_decls `thenTc` \ gen_inst_infos ->
+ = mappM get_generics class_decls `thenM` \ gen_inst_infos ->
let
gen_inst_info = concat gen_inst_infos
in
if null gen_inst_info then
- returnTc []
+ returnM []
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
+ getDOpts `thenM` \ dflags ->
+ ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances"
+ (vcat (map pprInstInfo gen_inst_info)))
+ `thenM_`
+ returnM gen_inst_info
get_generics decl@(ClassDecl {tcdMeths = Nothing})
- = returnTc [] -- Imported class decls
+ = returnM [] -- 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
+ = returnM [] -- 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 ->
+ = recoverM (returnM []) $
+ tcAddDeclCtxt decl $
+ tcLookupClass class_name `thenM` \ clas ->
-- Make an InstInfo out of each group
- mapTc (mkGenericInstance clas loc) groups `thenTc` \ inst_infos ->
+ mappM (mkGenericInstance clas loc) groups `thenM` \ inst_infos ->
-- Check that there is only one InstInfo for each type constructor
-- The main way this can fail is if you write
group `lengthExceeds` 1]
get_uniq (tc,_) = getUnique tc
in
- mapTc (addErrTc . dupGenericInsts) bad_groups `thenTc_`
+ mappM (addErrTc . dupGenericInsts) bad_groups `thenM_`
-- 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_`
+ checkTc (null missing) (missingGenericInstances missing) `thenM_`
- returnTc inst_infos
+ returnM inst_infos
where
-- Group the declarations by type pattern
tcHsTyVars sig_tvs (kcHsSigType hs_ty) $ \ tyvars ->
-- Type-check the instance type, and check its form
- tcHsSigType GenPatCtxt hs_ty `thenTc` \ inst_ty ->
+ tcHsSigType GenPatCtxt hs_ty `thenM` \ inst_ty ->
checkTc (validGenericInstanceType inst_ty)
- (badGenericInstanceType binds) `thenTc_`
+ (badGenericInstanceType binds) `thenM_`
-- Make the dictionary function.
- newDFunName clas [inst_ty] loc `thenNF_Tc` \ dfun_name ->
+ newDFunName clas [inst_ty] loc `thenM` \ 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
+ dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty]
in
- returnTc (InstInfo { iDFunId = dfun_id,
- iBinds = binds, iPrags = [] })
+ returnM (InstInfo { iDFunId = dfun_id, iBinds = VanillaInst binds [] })
\end{code}
%************************************************************************
\begin{code}
-tcInstDecls2 :: [InstInfo]
- -> NF_TcM (LIE, TcMonoBinds)
-
+tcInstDecls2 :: [InstInfo] -> TcM 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)
+ = mappM tcInstDecl2 inst_decls `thenM` \ binds_s ->
+ returnM (andMonoBindList binds_s)
\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 TcMonoBinds
-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))) $
-
- -- Instantiate the instance decl with tc-style type variables
+ recoverM (returnM EmptyMonoBinds) $
+ addSrcLoc (getSrcLoc dfun_id) $
+ addErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $
let
- (inst_tyvars, dfun_theta, clas, inst_tys) = tcSplitDFunTy (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
+ -- bizarre, but OK so long as you realise it!
in
- tcInstSigTyVars InstTv inst_tyvars `thenNF_Tc` \ inst_tyvars' ->
- let
- tenv = mkTopTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars')
- inst_tys' = map (substTy tenv) inst_tys
- dfun_theta' = substTheta tenv dfun_theta
- origin = InstanceDeclOrigin
+ -- Instantiate the instance decl with tc-style type variables
+ 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 (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 (mkTyVarSubst class_tyvars inst_tys') sc_theta
+ 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] ->
-
- 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 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.
- mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys'
- dfun_theta'
- monobinds uprags True)
- op_items
- ) `thenTc` \ (method_binds_s, insts_needed_s, meth_insts) ->
+ ------------------
+ -- Typecheck the methods
+ let -- These insts are in scope; quite a few, eh?
+ avail_insts = [this_dict] ++ dfun_arg_dicts ++ sc_dicts
+ in
+ tcMethods clas inst_tyvars inst_tyvars'
+ dfun_theta' inst_tys' avail_insts
+ op_items binds `thenM` \ (meth_ids, meth_binds) ->
+
+ -- Figure out bindings for the superclass context
+ tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts
+ `thenM` \ (zonked_inst_tyvars, sc_binds_inner, sc_binds_outer) ->
- -- Deal with SPECIALISE instance pragmas by making them
+ -- 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]
+ uprags = case binds of
+ VanillaInst _ uprags -> uprags
+ other -> []
+ spec_prags = [ SpecSig (idName dfun_id) ty loc
+ | SpecInstSig ty loc <- uprags ]
+ xtve = inst_tyvars `zip` inst_tyvars'
in
tcExtendGlobalValEnv [dfun_id] (
- tcSpecSigs dfun_prags
- ) `thenTc` \ (prag_binds, prag_lie) ->
-
- -- Check the overloading constraints of the methods and superclasses
- 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
- 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) ->
-
- -- 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 ->
+ 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))
+ HsApp (TyApp (HsVar rUNTIME_ERROR_ID) [idType this_dict_id])
+ (HsLit (HsStringPrim (mkFastString (stringToUtf8 msg))))
| otherwise -- The common case
= mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths)
-- 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 = VarMonoBind this_dict_id dict_rhs
+ all_binds = sc_binds_inner `AndMonoBinds` meth_binds `AndMonoBinds` dict_bind
+
+ main_bind = AbsBinds
+ zonked_inst_tyvars
+ (map instToId dfun_arg_dicts)
+ [(inst_tyvars', dfun_id, this_dict_id)]
+ inlines all_binds
+ in
+ showLIE "instance" `thenM_`
+ returnM (main_bind `AndMonoBinds` prag_binds `AndMonoBinds` 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 = collectMonoBinders 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 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.
+ let
+ all_insts = avail_insts ++ meth_insts
+ xtve = inst_tyvars `zip` inst_tyvars'
+ tc_method_bind = tcMethodBind xtve inst_tyvars' dfun_theta' all_insts uprags
+ in
+ mapM tc_method_bind meth_infos `thenM` \ meth_binds_s ->
+
+ returnM (map instToId meth_insts, andMonoBindList meth_binds_s)
+
+
+-- 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 `AndMonoBinds` andMonoBindList 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, VarMonoBind meth_id (HsVar (instToId rhs_inst)), rhs_inst)
+
+ -- Instantiate rep_tys with the relevant type variables
+ rep_tys' = map (substTy subst) rep_tys
+ subst = mkTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars')
\end{code}
+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 $
+ = addSrcLoc (tcdLoc decl) $
+ addErrCtxt ctxt $
thing_inside
where
thing = case decl of
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