\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
-module TcInstDcls ( tcInstDecls1, tcInstDecls2, tcAddDeclCtxt ) where
+module TcInstDcls ( tcInstDecls1, tcIfaceInstDecls1, addInstDFuns,
+ tcInstDecls2, initInstEnv, 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, toHsType
+ andMonoBindList, collectMonoBinders,
+ isClassDecl, toHsType
)
-import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl,
+import RnHsSyn ( RenamedHsBinds, RenamedInstDecl,
RenamedMonoBinds, RenamedTyClDecl, RenamedHsType,
extractHsTyVars, maybeGenericMatch
)
import TcBinds ( tcSpecSigs )
import TcClassDcl ( tcMethodBind, badMethodErr )
import TcMonad
-import TcMType ( tcInstTyVars, checkValidTheta, checkValidInstHead, instTypeErr,
+import TcMType ( tcInstSigType, checkValidTheta, checkValidInstHead, instTypeErr,
UserTypeCtxt(..), SourceTyCtxt(..) )
-import TcType ( tcSplitDFunTy, mkClassPred, mkTyVarTy,
- tcSplitSigmaTy, tcSplitPredTy_maybe, getClassPredTys
+import TcType ( mkClassPred, mkTyVarTy, tcSplitForAllTys,
+ tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe,
+ TyVarDetails(..)
)
-import Inst ( InstOrigin(..),
- newDicts, instToId,
+import Inst ( InstOrigin(..), newDicts, instToId,
LIE, mkLIE, emptyLIE, plusLIE, plusLIEs )
import TcDeriv ( tcDeriving )
-import TcEnv ( TcEnv, tcExtendGlobalValEnv,
- tcExtendTyVarEnvForMeths,
- tcAddImportedIdInfo, tcLookupClass,
+import TcEnv ( tcExtendGlobalValEnv,
+ tcExtendTyVarEnvForMeths, tcLookupId, tcLookupClass,
InstInfo(..), pprInstInfo, simpleInstInfoTyCon,
- simpleInstInfoTy, newDFunName,
- isLocalThing,
+ simpleInstInfoTy, newDFunName
)
import InstEnv ( InstEnv, extendInstEnv )
import PprType ( pprClassPred )
-import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType, checkSigTyVars )
+import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType )
+import TcUnify ( checkSigTyVars )
import TcSimplify ( tcSimplifyCheck )
-import HscTypes ( HomeSymbolTable, DFunId,
- ModDetails(..), PackageInstEnv, PersistentRenamerState
+import HscTypes ( HomeSymbolTable, DFunId, FixityEnv,
+ PersistentCompilerState(..), PersistentRenamerState,
+ ModDetails(..)
)
-
-import Subst ( substTy, substTheta )
+import Subst ( substTheta )
import DataCon ( classDataCon )
-import Class ( Class, DefMeth(..), classBigSig )
+import Class ( Class, classBigSig )
import Var ( idName, idType )
import VarSet ( emptyVarSet )
-import MkId ( mkDictFunId )
+import Id ( setIdLocalExported )
+import MkId ( mkDictFunId, unsafeCoerceId, eRROR_ID )
import FunDeps ( checkInstFDs )
import Generics ( validGenericInstanceType )
import Module ( Module, foldModuleEnv )
import Name ( getSrcLoc )
-import NameSet ( unitNameSet, nameSetToList )
-import PrelInfo ( eRROR_ID )
+import NameSet ( unitNameSet, emptyNameSet, nameSetToList )
import TyCon ( TyCon )
import Subst ( mkTopTyVarSubst, substTheta )
import TysWiredIn ( genericTyCons )
-import Name ( Name )
import SrcLoc ( SrcLoc )
import Unique ( Uniquable(..) )
-import BasicTypes ( NewOrData(..), Fixity )
+import Util ( lengthExceeds, isSingleton )
+import BasicTypes ( NewOrData(..) )
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 Outputable
\end{code}
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 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 $
+ -- 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 ->
+ mapNF_Tc tcLocalInstDecl1 inst_decls `thenNF_Tc` \ 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 ->
-- 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) 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 ->
-- (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 ->
+ -- 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 (inst_env1,
- 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
+
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 ->
+ = getDOptsTc `thenNF_Tc` \ dflags ->
let
(inst_env', errs) = extendInstEnv dflags inst_env dfuns
in
\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 []) $
+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
+ -- 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
+ recoverNF_Tc (returnNF_Tc Nothing) $
tcAddSrcLoc src_loc $
tcAddErrCtxt (instDeclCtxt poly_ty) $
tcHsType poly_ty `thenTc` \ 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 }]
+ checkValidTheta InstThetaCtxt theta `thenTc_`
+ checkValidInstHead tau `thenTc` \ (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 }))
where
msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class"))
\end{code}
if null gen_inst_info then
returnTc []
else
- getDOptsTc `thenTc` \ dflags ->
+ getDOptsTc `thenNF_Tc` \ dflags ->
ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances"
(vcat (map pprInstInfo gen_inst_info)))
`thenNF_Tc_`
| null groups
= returnTc [] -- The comon case: no generic default methods
- | otherwise -- A local class decl with generic default methods
+ | otherwise -- A source class decl with generic default methods
= recoverNF_Tc (returnNF_Tc []) $
tcAddDeclCtxt decl $
tcLookupClass class_name `thenTc` \ clas ->
tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos]
bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos,
- length group > 1]
+ group `lengthExceeds` 1]
get_uniq (tc,_) = getUnique tc
in
mapTc (addErrTc . dupGenericInsts) bad_groups `thenTc_`
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
+ dfun_id = mkDictFunId dfun_name clas tyvars [inst_ty] inst_theta
in
- returnTc (InstInfo { iDFunId = dfun_id,
- iBinds = binds, iPrags = [] })
+ returnTc (InstInfo { iDFunId = dfun_id, iBinds = binds, iPrags = [] })
\end{code}
\begin{code}
-tcInstDecl2 :: InstInfo -> NF_TcM (LIE, TcMonoBinds)
--- tcInstDecl2 is called *only* on InstInfos
+tcInstDecl2 :: InstInfo -> TcM (LIE, TcMonoBinds)
+
+tcInstDecl2 (NewTypeDerived { iDFunId = dfun_id })
+ = tcInstSigType 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 = 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
+ tcInstSigType InstTv (idType dfun_id) `thenNF_Tc` \ (inst_tyvars', dfun_theta', inst_head') ->
let
- (inst_tyvars, dfun_theta, clas, inst_tys) = tcSplitDFunTy (idType dfun_id)
- in
- tcInstTyVars inst_tyvars `thenNF_Tc` \ (inst_tyvars', _, tenv) ->
- let
- inst_tys' = map (substTy tenv) inst_tys
- dfun_theta' = substTheta tenv dfun_theta
- origin = InstanceDeclOrigin
-
+ Just pred = tcSplitPredTy_maybe inst_head'
+ (clas, inst_tys') = getClassPredTys pred
(class_tyvars, sc_theta, _, op_items) = classBigSig clas
- dm_ids = [dm_id | (_, DefMeth dm_id) <- op_items]
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
+ bad_bndrs = collectMonoBinders monobinds `minusList` sel_names
+ (inst_tyvars, _) = tcSplitForAllTys (idType dfun_id)
+ origin = InstanceDeclOrigin
in
-- Check that all the method bindings come from this class
mapTc (addErrTc . badMethodErr clas) bad_bndrs `thenNF_Tc_`
-- The type variable from the dict fun actually scope
-- over the bindings. They were gotten from
-- the original instance declaration
- tcExtendGlobalValEnv dm_ids (
- -- Default-method Ids may be mentioned in synthesised RHSs
+
+ -- 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) ->
+ ) `thenTc` \ (method_binds_s, insts_needed_s, meth_insts) ->
-- Deal with SPECIALISE instance pragmas by making them
-- look like SPECIALISE pragmas for the dfun
-- 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)
this_dict_id = instToId this_dict
- inlines = unitNameSet (idName dfun_id)
+ inlines | null dfun_arg_dicts = emptyNameSet
+ | otherwise = unitNameSet (idName dfun_id)
-- Always inline the dfun; this is an experimental decision
-- because it makes a big performance difference sometimes.
-- Often it means we can do the method selection, and then
-- inline the method as well. Marcin's idea; see comments below.
+ --
+ -- BUT: don't inline it if it's a constant dictionary;
+ -- we'll get all the benefit without inlining, and we get
+ -- a **lot** of code duplication if we inline it
dict_rhs
| null scs_and_meths
= AbsBinds
zonked_inst_tyvars
(map instToId dfun_arg_dicts)
- [(inst_tyvars', dfun_id, this_dict_id)]
+ [(inst_tyvars', local_dfun_id, this_dict_id)]
inlines
(lie_binds1 `AndMonoBinds`
lie_binds2 `AndMonoBinds`