\begin{code}
module Inst (
- LIE, emptyLIE, unitLIE, plusLIE, consLIE,
- plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
showLIE,
Inst,
- pprInst, pprInsts, pprInstsInFull, tidyInsts, tidyMoreInsts,
+ pprInst, pprInsts, pprInstsInFull, pprDFuns,
+ tidyInsts, tidyMoreInsts,
- newDictsFromOld, newDicts, cloneDict,
- newMethod, newMethodFromName, newMethodWithGivenTy,
- newMethodWith, newMethodAtLoc,
+ newDictsFromOld, newDicts, cloneDict,
newOverloadedLit, newIPDict,
- tcInstCall, tcInstDataCon, tcSyntaxName,
+ newMethod, newMethodFromName, newMethodWithGivenTy,
+ tcInstClassOp, tcInstCall, tcInstDataCon,
+ tcSyntaxName, tcStdSyntaxName,
tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE,
ipNamesOfInst, ipNamesOfInsts, fdPredsOfInst, fdPredsOfInsts,
instLoc, getDictClassTys, dictPred,
- lookupInst, lookupSimpleInst, LookupInstResult(..),
+ lookupInst, LookupInstResult(..),
+ tcExtendLocalInstEnv, tcGetInstEnvs,
isDict, isClassDict, isMethod,
isLinearInst, linearInstType, isIPDict, isInheritableInst,
isTyVarDict, isStdClassTyVarDict, isMethodFor,
- instBindingRequired, instCanBeGeneralised,
+ instBindingRequired,
zonkInst, zonkInsts,
instToId, instName,
- InstOrigin(..), InstLoc, pprInstLoc
+ InstOrigin(..), InstLoc(..), pprInstLoc
) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcExpr( tcExpr )
+import {-# SOURCE #-} TcExpr( tcCheckSigma )
import HsSyn ( HsLit(..), HsOverLit(..), HsExpr(..) )
-import TcHsSyn ( TcExpr, TcId, TcIdSet, TypecheckedHsExpr,
- mkHsTyApp, mkHsDictApp, mkHsConApp, zonkId
+import TcHsSyn ( TcExpr, TcId, TcIdSet,
+ mkHsTyApp, mkHsDictApp, mkHsConApp, zonkId,
+ mkCoercion, ExprCoFn
)
import TcRnMonad
-import TcEnv ( tcGetInstEnv, tcLookupId, tcLookupTyCon )
-import InstEnv ( InstLookupResult(..), lookupInstEnv )
-import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType, zapToType,
+import TcEnv ( tcLookupId, checkWellStaged, topIdLvl, tcMetaTy )
+import InstEnv ( DFunId, InstEnv, lookupInstEnv, checkFunDeps, extendInstEnv )
+import TcIface ( loadImportedInsts )
+import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType,
zonkTcThetaType, tcInstTyVar, tcInstType, tcInstTyVars
)
import TcType ( Type, TcType, TcThetaType, TcTyVarSet,
- SourceType(..), PredType, ThetaType, TyVarDetails(VanillaTv),
+ PredType(..), TyVarDetails(VanillaTv),
tcSplitForAllTys, tcSplitForAllTys, mkTyConApp,
- tcSplitMethodTy, tcSplitPhiTy, mkGenTyConApp,
+ tcSplitPhiTy, tcIsTyVarTy, tcSplitDFunTy,
isIntTy,isFloatTy, isIntegerTy, isDoubleTy,
tcIsTyVarTy, mkPredTy, mkTyVarTy, mkTyVarTys,
tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tidyPred,
- isClassPred, isTyVarClassPred, isLinearPred, predHasFDs,
+ isClassPred, isTyVarClassPred, isLinearPred,
getClassPredTys, getClassPredTys_maybe, mkPredName,
- isInheritablePred, isIPPred,
- tidyType, tidyTypes, tidyFreeTyVars, tcSplitSigmaTy
+ isInheritablePred, isIPPred, matchTys,
+ tidyType, tidyTypes, tidyFreeTyVars, tcSplitSigmaTy,
+ pprPred, pprParendType, pprThetaArrow, pprClassPred
)
+import HscTypes ( ExternalPackageState(..) )
import CoreFVs ( idFreeTyVars )
-import Class ( Class )
import DataCon ( DataCon,dataConSig )
import Id ( Id, idName, idType, mkUserLocal, mkSysLocal, mkLocalId, setIdUnique )
-import PrelInfo ( isStandardClass, isCcallishClass, isNoDictClass )
-import Name ( Name, mkMethodOcc, getOccName )
-import PprType ( pprPred, pprParendType )
-import Subst ( emptyInScopeSet, mkSubst,
- substTy, substTyWith, substTheta, mkTyVarSubst, mkTopTyVarSubst
- )
+import PrelInfo ( isStandardClass, isNoDictClass )
+import Name ( Name, mkMethodOcc, getOccName, getSrcLoc, isHomePackageName, isInternalName )
+import NameSet ( addOneToNameSet )
+import Subst ( substTy, substTyWith, substTheta, mkTyVarSubst )
import Literal ( inIntRange )
import Var ( TyVar )
import VarEnv ( TidyEnv, emptyTidyEnv, lookupSubstEnv, SubstResult(..) )
-import VarSet ( elemVarSet, emptyVarSet, unionVarSet )
+import VarSet ( elemVarSet, emptyVarSet, unionVarSet, mkVarSet )
import TysWiredIn ( floatDataCon, doubleDataCon )
-import PrelNames( fromIntegerName, fromRationalName, rationalTyConName )
-import Util ( equalLength )
+import PrelNames ( integerTyConName, fromIntegerName, fromRationalName, rationalTyConName )
import BasicTypes( IPName(..), mapIPName, ipNameName )
import UniqSupply( uniqsFromSupply )
+import CmdLineOpts( DynFlags, DynFlag( Opt_AllowUndecidableInstances ), dopt )
+import Maybes ( isJust )
import Outputable
\end{code}
getDictClassTys (Dict _ pred _) = getClassPredTys pred
-- fdPredsOfInst is used to get predicates that contain functional
--- dependencies; i.e. should participate in improvement
-fdPredsOfInst (Dict _ pred _) | predHasFDs pred = [pred]
- | otherwise = []
-fdPredsOfInst (Method _ _ _ theta _ _) = filter predHasFDs theta
-fdPredsOfInst other = []
+-- dependencies *or* might do so. The "might do" part is because
+-- a constraint (C a b) might have a superclass with FDs
+-- Leaving these in is really important for the call to fdPredsOfInsts
+-- in TcSimplify.inferLoop, because the result is fed to 'grow',
+-- which is supposed to be conservative
+fdPredsOfInst (Dict _ pred _) = [pred]
+fdPredsOfInst (Method _ _ _ theta _ _) = theta
+fdPredsOfInst other = [] -- LitInsts etc
fdPredsOfInsts :: [Inst] -> [PredType]
fdPredsOfInsts insts = concatMap fdPredsOfInst insts
instBindingRequired :: Inst -> Bool
instBindingRequired (Dict _ (ClassP clas _) _) = not (isNoDictClass clas)
instBindingRequired other = True
-
-instCanBeGeneralised :: Inst -> Bool
-instCanBeGeneralised (Dict _ (ClassP clas _) _) = not (isCcallishClass clas)
-instCanBeGeneralised other = True
\end{code}
newDictsAtLoc :: InstLoc
-> TcThetaType
-> TcM [Inst]
-newDictsAtLoc inst_loc@(_,loc,_) theta
+newDictsAtLoc inst_loc theta
= newUniqueSupply `thenM` \ us ->
returnM (zipWith mk_dict (uniqsFromSupply us) theta)
where
- mk_dict uniq pred = Dict (mkLocalId (mkPredName uniq loc pred) (mkPredTy pred)) pred inst_loc
+ mk_dict uniq pred = Dict (mkLocalId (mkPredName uniq loc pred) (mkPredTy pred))
+ pred inst_loc
+ loc = instLocSrcLoc inst_loc
-- For vanilla implicit parameters, there is only one in scope
-- at any time, so we used to use the name of the implicit parameter itself
newIPDict :: InstOrigin -> IPName Name -> Type
-> TcM (IPName Id, Inst)
newIPDict orig ip_name ty
- = getInstLoc orig `thenM` \ inst_loc@(_,loc,_) ->
+ = getInstLoc orig `thenM` \ inst_loc@(InstLoc _ loc _) ->
newUnique `thenM` \ uniq ->
let
pred = IParam ip_name ty
\begin{code}
-tcInstCall :: InstOrigin -> TcType -> TcM (TypecheckedHsExpr -> TypecheckedHsExpr, TcType)
+tcInstCall :: InstOrigin -> TcType -> TcM (ExprCoFn, TcType)
tcInstCall orig fun_ty -- fun_ty is usually a sigma-type
= tcInstType VanillaTv fun_ty `thenM` \ (tyvars, theta, tau) ->
newDicts orig theta `thenM` \ dicts ->
let
inst_fn e = mkHsDictApp (mkHsTyApp e (mkTyVarTys tyvars)) (map instToId dicts)
in
- returnM (inst_fn, tau)
+ returnM (mkCoercion inst_fn, tau)
tcInstDataCon :: InstOrigin -> DataCon
-> TcM ([TcType], -- Types to instantiate at
returnM (ty_args', ex_dicts, arg_tys', result_ty, ex_tvs')
-
newMethodFromName :: InstOrigin -> TcType -> Name -> TcM TcId
newMethodFromName origin ty name
= tcLookupId name `thenM` \ id ->
-- always a class op, but with -fno-implicit-prelude GHC is
-- meant to find whatever thing is in scope, and that may
-- be an ordinary function.
- newMethod origin id [ty]
-
-newMethod :: InstOrigin
- -> TcId
- -> [TcType]
- -> TcM Id
-newMethod orig id tys
- = -- Get the Id type and instantiate it at the specified types
- let
- (tyvars, rho) = tcSplitForAllTys (idType id)
- rho_ty = substTyWith tyvars tys rho
- (pred, tau) = tcSplitMethodTy rho_ty
- in
- newMethodWithGivenTy orig id tys [pred] tau
+ getInstLoc origin `thenM` \ loc ->
+ tcInstClassOp loc id [ty] `thenM` \ inst ->
+ extendLIE inst `thenM_`
+ returnM (instToId inst)
newMethodWithGivenTy orig id tys theta tau
= getInstLoc orig `thenM` \ loc ->
- newMethodWith loc id tys theta tau `thenM` \ inst ->
+ newMethod loc id tys theta tau `thenM` \ inst ->
extendLIE inst `thenM_`
returnM (instToId inst)
--------------------------------------------
--- newMethodWith and newMethodAtLoc do *not* drop the
+-- tcInstClassOp, and newMethod do *not* drop the
-- Inst into the LIE; they just returns the Inst
-- This is important because they are used by TcSimplify
-- to simplify Insts
-newMethodWith inst_loc@(_,loc,_) id tys theta tau
+tcInstClassOp :: InstLoc -> Id -> [TcType] -> TcM Inst
+tcInstClassOp inst_loc sel_id tys
+ = let
+ (tyvars,rho) = tcSplitForAllTys (idType sel_id)
+ rho_ty = ASSERT( length tyvars == length tys )
+ substTyWith tyvars tys rho
+ (preds,tau) = tcSplitPhiTy rho_ty
+ in
+ newMethod inst_loc sel_id tys preds tau
+
+---------------------------
+newMethod inst_loc id tys theta tau
= newUnique `thenM` \ new_uniq ->
let
meth_id = mkUserLocal (mkMethodOcc (getOccName id)) new_uniq tau loc
inst = Method meth_id id tys theta tau inst_loc
+ loc = instLocSrcLoc inst_loc
in
returnM inst
-
-newMethodAtLoc :: InstLoc
- -> Id -> [TcType]
- -> TcM Inst
-newMethodAtLoc inst_loc real_id tys
- -- This actually builds the Inst
- = -- Get the Id type and instantiate it at the specified types
- let
- (tyvars,rho) = tcSplitForAllTys (idType real_id)
- rho_ty = ASSERT( equalLength tyvars tys )
- substTy (mkTopTyVarSubst tyvars tys) rho
- (theta, tau) = tcSplitPhiTy rho_ty
- in
- newMethodWith inst_loc real_id tys theta tau
\end{code}
In newOverloadedLit we convert directly to an Int or Integer if we
| fi /= fromIntegerName -- Do not generate a LitInst for rebindable
-- syntax. Reason: tcSyntaxName does unification
-- which is very inconvenient in tcSimplify
- = tcSyntaxName orig expected_ty fromIntegerName fi `thenM` \ (expr, _) ->
- returnM (HsApp expr (HsLit (HsInteger i)))
+ = tcSyntaxName orig expected_ty (fromIntegerName, HsVar fi) `thenM` \ (_,expr) ->
+ mkIntegerLit i `thenM` \ integer_lit ->
+ returnM (HsApp expr integer_lit)
| Just expr <- shortCutIntLit i expected_ty
= returnM expr
newOverloadedLit orig lit@(HsFractional r fr) expected_ty
| fr /= fromRationalName -- c.f. HsIntegral case
- = tcSyntaxName orig expected_ty fromRationalName fr `thenM` \ (expr, _) ->
- mkRatLit r `thenM` \ rat_lit ->
+ = tcSyntaxName orig expected_ty (fromRationalName, HsVar fr) `thenM` \ (_,expr) ->
+ mkRatLit r `thenM` \ rat_lit ->
returnM (HsApp expr rat_lit)
| Just expr <- shortCutFracLit r expected_ty
newLitInst orig lit expected_ty
= getInstLoc orig `thenM` \ loc ->
newUnique `thenM` \ new_uniq ->
- zapToType expected_ty `thenM_`
- -- The expected type might be a 'hole' type variable,
- -- in which case we must zap it to an ordinary type variable
let
lit_inst = LitInst lit_id lit expected_ty loc
lit_id = mkSysLocal FSLIT("lit") new_uniq expected_ty
shortCutIntLit :: Integer -> TcType -> Maybe TcExpr
shortCutIntLit i ty
- | isIntTy ty && inIntRange i -- Short cut for Int
+ | isIntTy ty && inIntRange i -- Short cut for Int
= Just (HsLit (HsInt i))
- | isIntegerTy ty -- Short cut for Integer
- = Just (HsLit (HsInteger i))
+ | isIntegerTy ty -- Short cut for Integer
+ = Just (HsLit (HsInteger i ty))
| otherwise = Nothing
shortCutFracLit :: Rational -> TcType -> Maybe TcExpr
= Just (mkHsConApp doubleDataCon [] [HsLit (HsDoublePrim f)])
| otherwise = Nothing
+mkIntegerLit :: Integer -> TcM TcExpr
+mkIntegerLit i
+ = tcMetaTy integerTyConName `thenM` \ integer_ty ->
+ returnM (HsLit (HsInteger i integer_ty))
+
mkRatLit :: Rational -> TcM TcExpr
mkRatLit r
- = tcLookupTyCon rationalTyConName `thenM` \ rat_tc ->
- let
- rational_ty = mkGenTyConApp rat_tc []
- in
- returnM (HsLit (HsRat r rational_ty))
+ = tcMetaTy rationalTyConName `thenM` \ rat_ty ->
+ returnM (HsLit (HsRat r rat_ty))
\end{code}
pprInstsInFull insts
= vcat (map go insts)
where
- go inst = quotes (ppr inst) <+> pprInstLoc (instLoc inst)
+ go inst = sep [quotes (ppr inst), nest 2 (pprInstLoc (instLoc inst))]
pprInst (LitInst u lit ty loc)
= hsep [ppr lit, ptext SLIT("at"), ppr ty, show_uniq u]
show_uniq u,
ppr (instToId m) -}]
+
+pprDFuns :: [DFunId] -> SDoc
+-- Prints the dfun as an instance declaration
+pprDFuns dfuns = vcat [ hang (ppr (getSrcLoc dfun) <> colon)
+ 2 (ptext SLIT("instance") <+> sep [pprThetaArrow theta,
+ pprClassPred clas tys])
+ | dfun <- dfuns
+ , let (_, theta, clas, tys) = tcSplitDFunTy (idType dfun) ]
+ -- Print without the for-all, which the programmer doesn't write
+
show_uniq u = ifPprDebug (text "{-" <> ppr u <> text "-}")
tidyInst :: TidyEnv -> Inst -> Inst
tidyInsts :: [Inst] -> (TidyEnv, [Inst])
tidyInsts insts = tidyMoreInsts emptyTidyEnv insts
-showLIE :: String -> TcM () -- Debugging
+showLIE :: SDoc -> TcM () -- Debugging
showLIE str
= do { lie_var <- getLIEVar ;
lie <- readMutVar lie_var ;
- traceTc (text str <+> pprInstsInFull (lieToList lie)) }
+ traceTc (str <+> pprInstsInFull (lieToList lie)) }
\end{code}
%************************************************************************
%* *
+ Extending the instance environment
+%* *
+%************************************************************************
+
+\begin{code}
+tcExtendLocalInstEnv :: [DFunId] -> TcM a -> TcM a
+ -- Add new locally-defined instances
+tcExtendLocalInstEnv dfuns thing_inside
+ = do { traceDFuns dfuns
+ ; env <- getGblEnv
+ ; dflags <- getDOpts
+ ; inst_env' <- foldlM (addInst dflags) (tcg_inst_env env) dfuns
+ ; let env' = env { tcg_insts = dfuns ++ tcg_insts env,
+ tcg_inst_env = inst_env' }
+ ; setGblEnv env' thing_inside }
+
+addInst :: DynFlags -> InstEnv -> DFunId -> TcM InstEnv
+-- Check that the proposed new instance is OK,
+-- and then add it to the home inst env
+addInst dflags home_ie dfun
+ = do { -- Load imported instances, so that we report
+ -- duplicates correctly
+ pkg_ie <- loadImportedInsts cls tys
+
+ -- Check functional dependencies
+ ; case checkFunDeps (pkg_ie, home_ie) dfun of
+ Just dfuns -> funDepErr dfun dfuns
+ Nothing -> return ()
+
+ -- Check for duplicate instance decls
+ ; let { (matches, _) = lookupInstEnv dflags (pkg_ie, home_ie) cls tys
+ ; dup_dfuns = [dup_dfun | (_, (_, dup_tys, dup_dfun)) <- matches,
+ isJust (matchTys (mkVarSet tvs) tys dup_tys)] }
+ -- Find memebers of the match list which
+ -- dfun itself matches. If the match is 2-way, it's a duplicate
+ ; case dup_dfuns of
+ dup_dfun : _ -> dupInstErr dfun dup_dfun
+ [] -> return ()
+
+ -- OK, now extend the envt
+ ; return (extendInstEnv home_ie dfun) }
+ where
+ (tvs, _, cls, tys) = tcSplitDFunTy (idType dfun)
+
+traceDFuns dfuns
+ = traceTc (text "Adding instances:" <+> vcat (map pp dfuns))
+ where
+ pp dfun = ppr dfun <+> dcolon <+> ppr (idType dfun)
+
+funDepErr dfun dfuns
+ = addSrcLoc (getSrcLoc dfun) $
+ addErr (hang (ptext SLIT("Functional dependencies conflict between instance declarations:"))
+ 2 (pprDFuns (dfun:dfuns)))
+dupInstErr dfun dup_dfun
+ = addSrcLoc (getSrcLoc dfun) $
+ addErr (hang (ptext SLIT("Duplicate instance declarations:"))
+ 2 (pprDFuns [dfun, dup_dfun]))
+\end{code}
+
+%************************************************************************
+%* *
\subsection{Looking up Insts}
%* *
%************************************************************************
-- the LookupInstResult, where they can be further processed by tcSimplify
--- Dictionaries
-lookupInst dict@(Dict _ (ClassP clas tys) loc)
- = getDOpts `thenM` \ dflags ->
- tcGetInstEnv `thenM` \ inst_env ->
- case lookupInstEnv dflags inst_env clas tys of
-
- FoundInst tenv dfun_id
- -> -- It's possible that not all the tyvars are in
- -- the substitution, tenv. For example:
- -- instance C X a => D X where ...
- -- (presumably there's a functional dependency in class C)
- -- Hence the mk_ty_arg to instantiate any un-substituted tyvars.
- let
- (tyvars, rho) = tcSplitForAllTys (idType dfun_id)
- mk_ty_arg tv = case lookupSubstEnv tenv tv of
- Just (DoneTy ty) -> returnM ty
- Nothing -> tcInstTyVar VanillaTv tv `thenM` \ tc_tv ->
- returnM (mkTyVarTy tc_tv)
- in
- mappM mk_ty_arg tyvars `thenM` \ ty_args ->
- let
- dfun_rho = substTy (mkTyVarSubst tyvars ty_args) rho
- (theta, _) = tcSplitPhiTy dfun_rho
- ty_app = mkHsTyApp (HsVar dfun_id) ty_args
- in
- if null theta then
- returnM (SimpleInst ty_app)
- else
- newDictsAtLoc loc theta `thenM` \ dicts ->
- let
- rhs = mkHsDictApp ty_app (map instToId dicts)
- in
- returnM (GenInst dicts rhs)
-
- other -> returnM NoInstance
-
-lookupInst (Dict _ _ _) = returnM NoInstance
-
-- Methods
lookupInst inst@(Method _ id tys theta _ loc)
| otherwise
= ASSERT( from_integer_name == fromIntegerName ) -- A LitInst invariant
tcLookupId fromIntegerName `thenM` \ from_integer ->
- newMethodAtLoc loc from_integer [ty] `thenM` \ method_inst ->
+ tcInstClassOp loc from_integer [ty] `thenM` \ method_inst ->
+ mkIntegerLit i `thenM` \ integer_lit ->
returnM (GenInst [method_inst]
- (HsApp (HsVar (instToId method_inst)) (HsLit (HsInteger i))))
-
+ (HsApp (HsVar (instToId method_inst)) integer_lit))
lookupInst inst@(LitInst u (HsFractional f from_rat_name) ty loc)
| Just expr <- shortCutFracLit f ty
| otherwise
= ASSERT( from_rat_name == fromRationalName ) -- A LitInst invariant
tcLookupId fromRationalName `thenM` \ from_rational ->
- newMethodAtLoc loc from_rational [ty] `thenM` \ method_inst ->
+ tcInstClassOp loc from_rational [ty] `thenM` \ method_inst ->
mkRatLit f `thenM` \ rat_lit ->
returnM (GenInst [method_inst] (HsApp (HsVar (instToId method_inst)) rat_lit))
-\end{code}
-There is a second, simpler interface, when you want an instance of a
-class at a given nullary type constructor. It just returns the
-appropriate dictionary if it exists. It is used only when resolving
-ambiguous dictionaries.
+-- Dictionaries
+lookupInst dict@(Dict _ pred@(ClassP clas tys) loc)
+ = do { dflags <- getDOpts
+ ; if all tcIsTyVarTy tys &&
+ not (dopt Opt_AllowUndecidableInstances dflags)
+ -- Common special case; no lookup
+ -- NB: tcIsTyVarTy... don't look through newtypes!
+ -- Don't take this short cut if we allow undecidable instances
+ -- because we might have "instance T a where ...".
+ -- [That means we need -fallow-undecidable-instances in the
+ -- client module, as well as the module with the instance decl.]
+ then return NoInstance
+
+ else do
+ { pkg_ie <- loadImportedInsts clas tys
+ -- Suck in any instance decls that may be relevant
+ ; tcg_env <- getGblEnv
+ ; case lookupInstEnv dflags (pkg_ie, tcg_inst_env tcg_env) clas tys of {
+ ([(tenv, (_,_,dfun_id))], []) -> instantiate_dfun tenv dfun_id pred loc ;
+ (matches, unifs) -> do
+ { traceTc (text "lookupInst" <+> vcat [text "matches" <+> ppr matches,
+ text "unifs" <+> ppr unifs])
+ ; return NoInstance } } } }
+ -- In the case of overlap (multiple matches) we report
+ -- NoInstance here. That has the effect of making the
+ -- context-simplifier return the dict as an irreducible one.
+ -- Then it'll be given to addNoInstanceErrs, which will do another
+ -- lookupInstEnv to get the detailed info about what went wrong.
+
+lookupInst (Dict _ _ _) = returnM NoInstance
+
+-----------------
+instantiate_dfun tenv dfun_id pred loc
+ = -- Record that this dfun is needed
+ record_dfun_usage dfun_id `thenM_`
+
+ -- It's possible that not all the tyvars are in
+ -- the substitution, tenv. For example:
+ -- instance C X a => D X where ...
+ -- (presumably there's a functional dependency in class C)
+ -- Hence the mk_ty_arg to instantiate any un-substituted tyvars.
+ getStage `thenM` \ use_stage ->
+ checkWellStaged (ptext SLIT("instance for") <+> quotes (ppr pred))
+ (topIdLvl dfun_id) use_stage `thenM_`
+ let
+ (tyvars, rho) = tcSplitForAllTys (idType dfun_id)
+ mk_ty_arg tv = case lookupSubstEnv tenv tv of
+ Just (DoneTy ty) -> returnM ty
+ Nothing -> tcInstTyVar VanillaTv tv `thenM` \ tc_tv ->
+ returnM (mkTyVarTy tc_tv)
+ in
+ mappM mk_ty_arg tyvars `thenM` \ ty_args ->
+ let
+ dfun_rho = substTy (mkTyVarSubst tyvars ty_args) rho
+ (theta, _) = tcSplitPhiTy dfun_rho
+ ty_app = mkHsTyApp (HsVar dfun_id) ty_args
+ in
+ if null theta then
+ returnM (SimpleInst ty_app)
+ else
+ newDictsAtLoc loc theta `thenM` \ dicts ->
+ let
+ rhs = mkHsDictApp ty_app (map instToId dicts)
+ in
+ returnM (GenInst dicts rhs)
+
+record_dfun_usage dfun_id
+ | isInternalName dfun_name = return () -- From this module
+ | not (isHomePackageName dfun_name) = return () -- From another package package
+ | otherwise = getGblEnv `thenM` \ tcg_env ->
+ updMutVar (tcg_inst_uses tcg_env)
+ (`addOneToNameSet` idName dfun_id)
+ where
+ dfun_name = idName dfun_id
-\begin{code}
-lookupSimpleInst :: Class
- -> [Type] -- Look up (c,t)
- -> TcM (Maybe ThetaType) -- Here are the needed (c,t)s
-
-lookupSimpleInst clas tys
- = getDOpts `thenM` \ dflags ->
- tcGetInstEnv `thenM` \ inst_env ->
- case lookupInstEnv dflags inst_env clas tys of
- FoundInst tenv dfun
- -> returnM (Just (substTheta (mkSubst emptyInScopeSet tenv) theta))
- where
- (_, rho) = tcSplitForAllTys (idType dfun)
- (theta,_) = tcSplitPhiTy rho
-
- other -> returnM Nothing
+tcGetInstEnvs :: TcM (InstEnv, InstEnv)
+-- Gets both the home-pkg inst env (includes module being compiled)
+-- and the external-package inst-env
+tcGetInstEnvs = do { eps <- getEps; env <- getGblEnv;
+ return (tcg_inst_env env, eps_inst_env eps) }
\end{code}
+
%************************************************************************
%* *
Re-mappable syntax
\begin{code}
tcSyntaxName :: InstOrigin
-> TcType -- Type to instantiate it at
- -> Name -> Name -- (Standard name, user name)
- -> TcM (TcExpr, TcType) -- Suitable expression with its type
+ -> (Name, HsExpr Name) -- (Standard name, user name)
+ -> TcM (Name, TcExpr) -- (Standard name, suitable expression)
-- NB: tcSyntaxName calls tcExpr, and hence can do unification.
-- So we do not call it from lookupInst, which is called from tcSimplify
-tcSyntaxName orig ty std_nm user_nm
+tcSyntaxName orig ty (std_nm, HsVar user_nm)
| std_nm == user_nm
- = newMethodFromName orig ty std_nm `thenM` \ id ->
- returnM (HsVar id, idType id)
+ = tcStdSyntaxName orig ty std_nm
- | otherwise
+tcSyntaxName orig ty (std_nm, user_nm_expr)
= tcLookupId std_nm `thenM` \ std_id ->
let
-- C.f. newMethodAtLoc
([tv], _, tau) = tcSplitSigmaTy (idType std_id)
- tau1 = substTy (mkTopTyVarSubst [tv] [ty]) tau
+ tau1 = substTyWith [tv] [ty] tau
+ -- Actually, the "tau-type" might be a sigma-type in the
+ -- case of locally-polymorphic methods.
in
- addErrCtxtM (syntaxNameCtxt user_nm orig tau1) $
- tcExpr (HsVar user_nm) tau1 `thenM` \ user_fn ->
- returnM (user_fn, tau1)
+ addErrCtxtM (syntaxNameCtxt user_nm_expr orig tau1) $
+
+ -- Check that the user-supplied thing has the
+ -- same type as the standard one
+ tcCheckSigma user_nm_expr tau1 `thenM` \ expr ->
+ returnM (std_nm, expr)
+
+tcStdSyntaxName :: InstOrigin
+ -> TcType -- Type to instantiate it at
+ -> Name -- Standard name
+ -> TcM (Name, TcExpr) -- (Standard name, suitable expression)
+
+tcStdSyntaxName orig ty std_nm
+ = newMethodFromName orig ty std_nm `thenM` \ id ->
+ returnM (std_nm, HsVar id)
syntaxNameCtxt name orig ty tidy_env
= getInstLoc orig `thenM` \ inst_loc ->
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