X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FInst.lhs;h=cd189a5475862c1b3b7e99d7ad486aac00957d84;hb=115f0fae2f782836550a9419f739fd29c09e4f1b;hp=155ed13c4d2f07b21cd7f37d041996b70fe9d86c;hpb=69e14f75a4b031e489b7774914e5a176409cea78;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/Inst.lhs b/ghc/compiler/typecheck/Inst.lhs index 155ed13..cd189a5 100644 --- a/ghc/compiler/typecheck/Inst.lhs +++ b/ghc/compiler/typecheck/Inst.lhs @@ -4,252 +4,181 @@ \section[Inst]{The @Inst@ type: dictionaries or method instances} \begin{code} -module Inst ( - LIE, emptyLIE, unitLIE, plusLIE, consLIE, zonkLIE, - plusLIEs, mkLIE, isEmptyLIE, +module Inst ( + LIE, emptyLIE, unitLIE, plusLIE, consLIE, + plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE, + showLIE, - Inst, OverloadedLit(..), - pprInst, pprInsts, pprInstsInFull, tidyInst, tidyInsts, + Inst, + pprInst, pprInsts, pprInstsInFull, tidyInsts, tidyMoreInsts, - InstanceMapper, + newDictsFromOld, newDicts, cloneDict, + newOverloadedLit, newIPDict, + newMethod, newMethodFromName, newMethodWithGivenTy, + tcInstClassOp, tcInstCall, tcInstDataCon, tcSyntaxName, - newDictFromOld, newDicts, newDictsAtLoc, - newMethod, newMethodWithGivenTy, newOverloadedLit, instOverloadedFun, + tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE, + ipNamesOfInst, ipNamesOfInsts, fdPredsOfInst, fdPredsOfInsts, + instLoc, getDictClassTys, dictPred, - tyVarsOfInst, instLoc, getDictClassTys, + lookupInst, LookupInstResult(..), - lookupInst, lookupSimpleInst, LookupInstResult(..), - - isDict, isTyVarDict, isStdClassTyVarDict, isMethodFor, + isDict, isClassDict, isMethod, + isLinearInst, linearInstType, isIPDict, isInheritableInst, + isTyVarDict, isStdClassTyVarDict, isMethodFor, instBindingRequired, instCanBeGeneralised, - zonkInst, instToId, instToIdBndr, + zonkInst, zonkInsts, + instToId, instName, - InstOrigin(..), pprOrigin + InstOrigin(..), InstLoc(..), pprInstLoc ) where #include "HsVersions.h" -import HsSyn ( HsLit(..), HsExpr(..) ) -import RnHsSyn ( RenamedArithSeqInfo, RenamedHsExpr, RenamedPat ) -import TcHsSyn ( TcExpr, TcId, - mkHsTyApp, mkHsDictApp, zonkId - ) -import TcMonad -import TcEnv ( TcIdSet, tcLookupValueByKey, tcLookupTyConByKey ) -import TcType ( TcThetaType, - TcType, TcTauType, TcTyVarSet, - zonkTcType, zonkTcTypes, - zonkTcThetaType - ) -import Bag -import Class ( classInstEnv, Class ) -import Id ( Id, idFreeTyVars, idType, mkUserLocal, mkSysLocal ) -import VarSet ( elemVarSet ) -import PrelInfo ( isStandardClass, isCcallishClass, isNoDictClass ) -import Name ( OccName, Name, mkDictOcc, mkMethodOcc, getOccName ) -import PprType ( pprConstraint ) -import InstEnv ( InstEnv, lookupInstEnv ) -import SrcLoc ( SrcLoc ) -import Type ( Type, ThetaType, - mkTyVarTy, isTyVarTy, mkDictTy, splitForAllTys, splitSigmaTy, - splitRhoTy, tyVarsOfType, tyVarsOfTypes, - mkSynTy, tidyOpenType, tidyOpenTypes - ) -import InstEnv ( InstEnv ) -import Subst ( emptyInScopeSet, mkSubst, - substTy, substTheta, mkTyVarSubst, mkTopTyVarSubst +import {-# SOURCE #-} TcExpr( tcExpr ) + +import HsSyn ( HsLit(..), HsOverLit(..), HsExpr(..) ) +import TcHsSyn ( TcExpr, TcId, TcIdSet, TypecheckedHsExpr, + mkHsTyApp, mkHsDictApp, mkHsConApp, zonkId ) -import TyCon ( TyCon ) -import Subst ( mkTyVarSubst ) -import VarEnv ( lookupVarEnv, TidyEnv, - lookupSubstEnv, SubstResult(..) +import TcRnMonad +import TcEnv ( tcGetInstEnv, tcLookupId, tcLookupTyCon, checkWellStaged, topIdLvl ) +import InstEnv ( InstLookupResult(..), lookupInstEnv ) +import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType, zapToType, + zonkTcThetaType, tcInstTyVar, tcInstType, tcInstTyVars ) -import VarSet ( unionVarSet ) -import TysPrim ( intPrimTy, floatPrimTy, doublePrimTy ) -import TysWiredIn ( intDataCon, isIntTy, inIntRange, - floatDataCon, isFloatTy, - doubleDataCon, isDoubleTy, - integerTy, isIntegerTy - ) -import Unique ( fromRationalClassOpKey, rationalTyConKey, - fromIntClassOpKey, fromIntegerClassOpKey, Unique +import TcType ( Type, TcType, TcThetaType, TcTyVarSet, + SourceType(..), PredType, ThetaType, TyVarDetails(VanillaTv), + tcSplitForAllTys, tcSplitForAllTys, mkTyConApp, + tcSplitMethodTy, tcSplitPhiTy, mkGenTyConApp, + isIntTy,isFloatTy, isIntegerTy, isDoubleTy, + tcIsTyVarTy, mkPredTy, mkTyVarTy, mkTyVarTys, + tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tidyPred, + isClassPred, isTyVarClassPred, isLinearPred, predHasFDs, + getClassPredTys, getClassPredTys_maybe, mkPredName, + isInheritablePred, isIPPred, + tidyType, tidyTypes, tidyFreeTyVars, tcSplitSigmaTy ) -import Maybes ( expectJust ) -import Util ( thenCmp, zipWithEqual, mapAccumL ) +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 ) +import Literal ( inIntRange ) +import Var ( TyVar ) +import VarEnv ( TidyEnv, emptyTidyEnv, lookupSubstEnv, SubstResult(..) ) +import VarSet ( elemVarSet, emptyVarSet, unionVarSet ) +import TysWiredIn ( floatDataCon, doubleDataCon ) +import PrelNames( fromIntegerName, fromRationalName, rationalTyConName ) +import BasicTypes( IPName(..), mapIPName, ipNameName ) +import UniqSupply( uniqsFromSupply ) import Outputable \end{code} -%************************************************************************ -%* * -\subsection[Inst-collections]{LIE: a collection of Insts} -%* * -%************************************************************************ +Selection +~~~~~~~~~ \begin{code} -type LIE = Bag Inst - -isEmptyLIE = isEmptyBag -emptyLIE = emptyBag -unitLIE inst = unitBag inst -mkLIE insts = listToBag insts -plusLIE lie1 lie2 = lie1 `unionBags` lie2 -consLIE inst lie = inst `consBag` lie -plusLIEs lies = unionManyBags lies - -zonkLIE :: LIE -> NF_TcM s LIE -zonkLIE lie = mapBagNF_Tc zonkInst lie +instName :: Inst -> Name +instName inst = idName (instToId inst) -pprInsts :: [Inst] -> SDoc -pprInsts insts = parens (sep (punctuate comma (map pprInst insts))) - - -pprInstsInFull insts - = vcat (map go insts) - where - go inst = quotes (ppr inst) <+> pprOrigin inst -\end{code} - -%************************************************************************ -%* * -\subsection[Inst-types]{@Inst@ types} -%* * -%************************************************************************ +instToId :: Inst -> TcId +instToId (Dict id _ _) = id +instToId (Method id _ _ _ _ _) = id +instToId (LitInst id _ _ _) = id -An @Inst@ is either a dictionary, an instance of an overloaded -literal, or an instance of an overloaded value. We call the latter a -``method'' even though it may not correspond to a class operation. -For example, we might have an instance of the @double@ function at -type Int, represented by +instLoc (Dict _ _ loc) = loc +instLoc (Method _ _ _ _ _ loc) = loc +instLoc (LitInst _ _ _ loc) = loc - Method 34 doubleId [Int] origin +dictPred (Dict _ pred _ ) = pred +dictPred inst = pprPanic "dictPred" (ppr inst) -\begin{code} -data Inst - = Dict - Unique - Class -- The type of the dict is (c ts), where - [TcType] -- c is the class and ts the types; - InstOrigin - SrcLoc - - | Method - Unique - - TcId -- The overloaded function - -- This function will be a global, local, or ClassOpId; - -- inside instance decls (only) it can also be an InstId! - -- The id needn't be completely polymorphic. - -- You'll probably find its name (for documentation purposes) - -- inside the InstOrigin - - [TcType] -- The types to which its polymorphic tyvars - -- should be instantiated. - -- These types must saturate the Id's foralls. - - TcThetaType -- The (types of the) dictionaries to which the function - -- must be applied to get the method - - TcTauType -- The type of the method - - InstOrigin - SrcLoc - - -- INVARIANT: in (Method u f tys theta tau loc) - -- type of (f tys dicts(from theta)) = tau - - | LitInst - Unique - OverloadedLit - TcType -- The type at which the literal is used - InstOrigin -- Always a literal; but more convenient to carry this around - SrcLoc - -data OverloadedLit - = OverloadedIntegral Integer -- The number - | OverloadedFractional Rational -- The number -\end{code} +getDictClassTys (Dict _ pred _) = getClassPredTys pred -Ordering -~~~~~~~~ -@Insts@ are ordered by their class/type info, rather than by their -unique. This allows the context-reduction mechanism to use standard finite -maps to do their stuff. +-- 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 = [] -\begin{code} -instance Ord Inst where - compare = cmpInst - -instance Eq Inst where - (==) i1 i2 = case i1 `cmpInst` i2 of - EQ -> True - other -> False - -cmpInst (Dict _ clas1 tys1 _ _) (Dict _ clas2 tys2 _ _) - = (clas1 `compare` clas2) `thenCmp` (tys1 `compare` tys2) -cmpInst (Dict _ _ _ _ _) other - = LT - - -cmpInst (Method _ _ _ _ _ _ _) (Dict _ _ _ _ _) - = GT -cmpInst (Method _ id1 tys1 _ _ _ _) (Method _ id2 tys2 _ _ _ _) - = (id1 `compare` id2) `thenCmp` (tys1 `compare` tys2) -cmpInst (Method _ _ _ _ _ _ _) other - = LT - -cmpInst (LitInst _ lit1 ty1 _ _) (LitInst _ lit2 ty2 _ _) - = (lit1 `cmpOverLit` lit2) `thenCmp` (ty1 `compare` ty2) -cmpInst (LitInst _ _ _ _ _) other - = GT - -cmpOverLit (OverloadedIntegral i1) (OverloadedIntegral i2) = i1 `compare` i2 -cmpOverLit (OverloadedFractional f1) (OverloadedFractional f2) = f1 `compare` f2 -cmpOverLit (OverloadedIntegral _) (OverloadedFractional _) = LT -cmpOverLit (OverloadedFractional _) (OverloadedIntegral _) = GT -\end{code} +fdPredsOfInsts :: [Inst] -> [PredType] +fdPredsOfInsts insts = concatMap fdPredsOfInst insts +isInheritableInst (Dict _ pred _) = isInheritablePred pred +isInheritableInst (Method _ _ _ theta _ _) = all isInheritablePred theta +isInheritableInst other = True -Selection -~~~~~~~~~ -\begin{code} -instOrigin (Dict u clas tys origin loc) = origin -instOrigin (Method u clas ty _ _ origin loc) = origin -instOrigin (LitInst u lit ty origin loc) = origin -instLoc (Dict u clas tys origin loc) = loc -instLoc (Method u clas ty _ _ origin loc) = loc -instLoc (LitInst u lit ty origin loc) = loc +ipNamesOfInsts :: [Inst] -> [Name] +ipNamesOfInst :: Inst -> [Name] +-- Get the implicit parameters mentioned by these Insts +-- NB: ?x and %x get different Names +ipNamesOfInsts insts = [n | inst <- insts, n <- ipNamesOfInst inst] -getDictClassTys (Dict u clas tys _ _) = (clas, tys) +ipNamesOfInst (Dict _ (IParam n _) _) = [ipNameName n] +ipNamesOfInst (Method _ _ _ theta _ _) = [ipNameName n | IParam n _ <- theta] +ipNamesOfInst other = [] tyVarsOfInst :: Inst -> TcTyVarSet -tyVarsOfInst (Dict _ _ tys _ _) = tyVarsOfTypes tys -tyVarsOfInst (Method _ id tys _ _ _ _) = tyVarsOfTypes tys `unionVarSet` idFreeTyVars id +tyVarsOfInst (LitInst _ _ ty _) = tyVarsOfType ty +tyVarsOfInst (Dict _ pred _) = tyVarsOfPred pred +tyVarsOfInst (Method _ id tys _ _ _) = tyVarsOfTypes tys `unionVarSet` idFreeTyVars id -- The id might have free type variables; in the case of -- locally-overloaded class methods, for example -tyVarsOfInst (LitInst _ _ ty _ _) = tyVarsOfType ty + + +tyVarsOfInsts insts = foldr (unionVarSet . tyVarsOfInst) emptyVarSet insts +tyVarsOfLIE lie = tyVarsOfInsts (lieToList lie) \end{code} Predicates ~~~~~~~~~~ \begin{code} isDict :: Inst -> Bool -isDict (Dict _ _ _ _ _) = True -isDict other = False +isDict (Dict _ _ _) = True +isDict other = False -isMethodFor :: TcIdSet -> Inst -> Bool -isMethodFor ids (Method uniq id tys _ _ orig loc) - = id `elemVarSet` ids -isMethodFor ids inst - = False +isClassDict :: Inst -> Bool +isClassDict (Dict _ pred _) = isClassPred pred +isClassDict other = False isTyVarDict :: Inst -> Bool -isTyVarDict (Dict _ _ tys _ _) = all isTyVarTy tys -isTyVarDict other = False +isTyVarDict (Dict _ pred _) = isTyVarClassPred pred +isTyVarDict other = False + +isIPDict :: Inst -> Bool +isIPDict (Dict _ pred _) = isIPPred pred +isIPDict other = False + +isMethod :: Inst -> Bool +isMethod (Method _ _ _ _ _ _) = True +isMethod other = False + +isMethodFor :: TcIdSet -> Inst -> Bool +isMethodFor ids (Method uniq id tys _ _ loc) = id `elemVarSet` ids +isMethodFor ids inst = False -isStdClassTyVarDict (Dict _ clas [ty] _ _) = isStandardClass clas && isTyVarTy ty -isStdClassTyVarDict other = False +isLinearInst :: Inst -> Bool +isLinearInst (Dict _ pred _) = isLinearPred pred +isLinearInst other = False + -- We never build Method Insts that have + -- linear implicit paramters in them. + -- Hence no need to look for Methods + -- See TcExpr.tcId + +linearInstType :: Inst -> TcType -- %x::t --> t +linearInstType (Dict _ (IParam _ ty) _) = ty + + +isStdClassTyVarDict (Dict _ pred _) = case getClassPredTys_maybe pred of + Just (clas, [ty]) -> isStandardClass clas && tcIsTyVarTy ty + other -> False \end{code} Two predicates which deal with the case where class constraints don't @@ -259,88 +188,159 @@ must be witnessed by an actual binding; the second tells whether an \begin{code} instBindingRequired :: Inst -> Bool -instBindingRequired (Dict _ clas _ _ _) = not (isNoDictClass clas) -instBindingRequired other = True +instBindingRequired (Dict _ (ClassP clas _) _) = not (isNoDictClass clas) +instBindingRequired other = True instCanBeGeneralised :: Inst -> Bool -instCanBeGeneralised (Dict _ clas _ _ _) = not (isCcallishClass clas) -instCanBeGeneralised other = True +instCanBeGeneralised (Dict _ (ClassP clas _) _) = not (isCcallishClass clas) +instCanBeGeneralised other = True \end{code} -Construction -~~~~~~~~~~~~ +%************************************************************************ +%* * +\subsection{Building dictionaries} +%* * +%************************************************************************ \begin{code} newDicts :: InstOrigin -> TcThetaType - -> NF_TcM s (LIE, [TcId]) + -> TcM [Inst] newDicts orig theta - = tcGetSrcLoc `thenNF_Tc` \ loc -> - newDictsAtLoc orig loc theta `thenNF_Tc` \ (dicts, ids) -> - returnNF_Tc (listToBag dicts, ids) + = getInstLoc orig `thenM` \ loc -> + newDictsAtLoc loc theta + +cloneDict :: Inst -> TcM Inst +cloneDict (Dict id ty loc) = newUnique `thenM` \ uniq -> + returnM (Dict (setIdUnique id uniq) ty loc) + +newDictsFromOld :: Inst -> TcThetaType -> TcM [Inst] +newDictsFromOld (Dict _ _ loc) theta = newDictsAtLoc loc theta -- Local function, similar to newDicts, -- but with slightly different interface -newDictsAtLoc :: InstOrigin - -> SrcLoc +newDictsAtLoc :: InstLoc -> TcThetaType - -> NF_TcM s ([Inst], [TcId]) -newDictsAtLoc orig loc theta = - tcGetUniques (length theta) `thenNF_Tc` \ new_uniqs -> - let - mk_dict u (clas, tys) = Dict u clas tys orig loc - dicts = zipWithEqual "newDictsAtLoc" mk_dict new_uniqs theta - in - returnNF_Tc (dicts, map instToId dicts) - -newDictFromOld :: Inst -> Class -> [TcType] -> NF_TcM s Inst -newDictFromOld (Dict _ _ _ orig loc) clas tys - = tcGetUnique `thenNF_Tc` \ uniq -> - returnNF_Tc (Dict uniq clas tys orig loc) - - -newMethod :: InstOrigin - -> TcId - -> [TcType] - -> NF_TcM s (LIE, TcId) -newMethod orig id tys - = -- Get the Id type and instantiate it at the specified types + -> TcM [Inst] +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 + 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 +-- But with splittable implicit parameters there may be many in +-- scope, so we make up a new name. +newIPDict :: InstOrigin -> IPName Name -> Type + -> TcM (IPName Id, Inst) +newIPDict orig ip_name ty + = getInstLoc orig `thenM` \ inst_loc@(InstLoc _ loc _) -> + newUnique `thenM` \ uniq -> let - (tyvars, rho) = splitForAllTys (idType id) - rho_ty = substTy (mkTyVarSubst tyvars tys) rho - (theta, tau) = splitRhoTy rho_ty + pred = IParam ip_name ty + id = mkLocalId (mkPredName uniq loc pred) (mkPredTy pred) in - newMethodWithGivenTy orig id tys theta tau `thenNF_Tc` \ meth_inst -> - returnNF_Tc (unitLIE meth_inst, instToId meth_inst) + returnM (mapIPName (\n -> id) ip_name, Dict id pred inst_loc) +\end{code} -instOverloadedFun orig (HsVar v) arg_tys theta tau - = newMethodWithGivenTy orig v arg_tys theta tau `thenNF_Tc` \ inst -> - returnNF_Tc (HsVar (instToId inst), unitLIE inst) -newMethodWithGivenTy orig id tys theta tau - = tcGetSrcLoc `thenNF_Tc` \ loc -> - tcGetUnique `thenNF_Tc` \ new_uniq -> + +%************************************************************************ +%* * +\subsection{Building methods (calls of overloaded functions)} +%* * +%************************************************************************ + + +\begin{code} +tcInstCall :: InstOrigin -> TcType -> TcM (TypecheckedHsExpr -> TypecheckedHsExpr, 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 -> + extendLIEs dicts `thenM_` + let + inst_fn e = mkHsDictApp (mkHsTyApp e (mkTyVarTys tyvars)) (map instToId dicts) + in + returnM (inst_fn, tau) + +tcInstDataCon :: InstOrigin -> DataCon + -> TcM ([TcType], -- Types to instantiate at + [Inst], -- Existential dictionaries to apply to + [TcType], -- Argument types of constructor + TcType, -- Result type + [TyVar]) -- Existential tyvars +tcInstDataCon orig data_con + = let + (tvs, stupid_theta, ex_tvs, ex_theta, arg_tys, tycon) = dataConSig data_con + -- We generate constraints for the stupid theta even when + -- pattern matching (as the Report requires) + in + tcInstTyVars VanillaTv (tvs ++ ex_tvs) `thenM` \ (all_tvs', ty_args', tenv) -> let - meth_inst = Method new_uniq id tys theta tau orig loc + stupid_theta' = substTheta tenv stupid_theta + ex_theta' = substTheta tenv ex_theta + arg_tys' = map (substTy tenv) arg_tys + + n_normal_tvs = length tvs + ex_tvs' = drop n_normal_tvs all_tvs' + result_ty = mkTyConApp tycon (take n_normal_tvs ty_args') in - returnNF_Tc meth_inst - -newMethodAtLoc :: InstOrigin -> SrcLoc - -> Id -> [TcType] - -> NF_TcM s (Inst, TcId) -newMethodAtLoc orig loc real_id tys -- Local function, similar to newMethod but with - -- slightly different interface - = -- Get the Id type and instantiate it at the specified types - tcGetUnique `thenNF_Tc` \ new_uniq -> + newDicts orig stupid_theta' `thenM` \ stupid_dicts -> + newDicts orig ex_theta' `thenM` \ ex_dicts -> + + -- Note that we return the stupid theta *only* in the LIE; + -- we don't otherwise use it at all + extendLIEs stupid_dicts `thenM_` + + 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 -> + -- Use tcLookupId not tcLookupGlobalId; the method is almost + -- 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. + 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 -> + newMethod loc id tys theta tau `thenM` \ inst -> + extendLIE inst `thenM_` + returnM (instToId inst) + +-------------------------------------------- +-- 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 + +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 - (tyvars,rho) = splitForAllTys (idType real_id) - rho_ty = ASSERT( length tyvars == length tys ) - substTy (mkTopTyVarSubst tyvars tys) rho - (theta, tau) = splitRhoTy rho_ty - meth_inst = Method new_uniq real_id tys theta tau orig loc + 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 - returnNF_Tc (meth_inst, instToId meth_inst) + returnM inst \end{code} In newOverloadedLit we convert directly to an Int or Integer if we @@ -350,78 +350,114 @@ cases (the rest are caught in lookupInst). \begin{code} newOverloadedLit :: InstOrigin - -> OverloadedLit + -> HsOverLit -> TcType - -> NF_TcM s (TcExpr, LIE) -newOverloadedLit orig (OverloadedIntegral i) ty - | isIntTy ty && inIntRange i -- Short cut for Int - = returnNF_Tc (int_lit, emptyLIE) - - | isIntegerTy ty -- Short cut for Integer - = returnNF_Tc (integer_lit, emptyLIE) - - where - intprim_lit = HsLitOut (HsIntPrim i) intPrimTy - integer_lit = HsLitOut (HsInt i) integerTy - int_lit = HsCon intDataCon [] [intprim_lit] - -newOverloadedLit orig lit ty -- The general case - = tcGetSrcLoc `thenNF_Tc` \ loc -> - tcGetUnique `thenNF_Tc` \ new_uniq -> + -> TcM TcExpr +newOverloadedLit orig lit@(HsIntegral i fi) expected_ty + | 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))) + + | Just expr <- shortCutIntLit i expected_ty + = returnM expr + + | otherwise + = newLitInst orig lit expected_ty + +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 -> + returnM (HsApp expr rat_lit) + + | Just expr <- shortCutFracLit r expected_ty + = returnM expr + + | otherwise + = newLitInst orig lit 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 new_uniq lit ty orig loc + lit_inst = LitInst lit_id lit expected_ty loc + lit_id = mkSysLocal FSLIT("lit") new_uniq expected_ty in - returnNF_Tc (HsVar (instToId lit_inst), unitLIE lit_inst) + extendLIE lit_inst `thenM_` + returnM (HsVar (instToId lit_inst)) + +shortCutIntLit :: Integer -> TcType -> Maybe TcExpr +shortCutIntLit i ty + | isIntTy ty && inIntRange i -- Short cut for Int + = Just (HsLit (HsInt i)) + | isIntegerTy ty -- Short cut for Integer + = Just (HsLit (HsInteger i)) + | otherwise = Nothing + +shortCutFracLit :: Rational -> TcType -> Maybe TcExpr +shortCutFracLit f ty + | isFloatTy ty + = Just (mkHsConApp floatDataCon [] [HsLit (HsFloatPrim f)]) + | isDoubleTy ty + = Just (mkHsConApp doubleDataCon [] [HsLit (HsDoublePrim f)]) + | otherwise = Nothing + +mkRatLit :: Rational -> TcM TcExpr +mkRatLit r + = tcLookupTyCon rationalTyConName `thenM` \ rat_tc -> + let + rational_ty = mkGenTyConApp rat_tc [] + in + returnM (HsLit (HsRat r rational_ty)) \end{code} -\begin{code} -instToId :: Inst -> TcId -instToId inst = instToIdBndr inst - -instToIdBndr :: Inst -> TcId -instToIdBndr (Dict u clas ty orig loc) - = mkUserLocal (mkDictOcc (getOccName clas)) u (mkDictTy clas ty) loc - -instToIdBndr (Method u id tys theta tau orig loc) - = mkUserLocal (mkMethodOcc (getOccName id)) u tau loc - -instToIdBndr (LitInst u list ty orig loc) - = mkSysLocal SLIT("lit") u ty -\end{code} - +%************************************************************************ +%* * +\subsection{Zonking} +%* * +%************************************************************************ -Zonking -~~~~~~~ Zonking makes sure that the instance types are fully zonked, -but doesn't do the same for the Id in a Method. There's no +but doesn't do the same for any of the Ids in an Inst. There's no need, and it's a lot of extra work. \begin{code} -zonkInst :: Inst -> NF_TcM s Inst -zonkInst (Dict u clas tys orig loc) - = zonkTcTypes tys `thenNF_Tc` \ new_tys -> - returnNF_Tc (Dict u clas new_tys orig loc) +zonkInst :: Inst -> TcM Inst +zonkInst (Dict id pred loc) + = zonkTcPredType pred `thenM` \ new_pred -> + returnM (Dict id new_pred loc) -zonkInst (Method u id tys theta tau orig loc) - = zonkId id `thenNF_Tc` \ new_id -> +zonkInst (Method m id tys theta tau loc) + = zonkId id `thenM` \ new_id -> -- Essential to zonk the id in case it's a local variable -- Can't use zonkIdOcc because the id might itself be -- an InstId, in which case it won't be in scope - zonkTcTypes tys `thenNF_Tc` \ new_tys -> - zonkTcThetaType theta `thenNF_Tc` \ new_theta -> - zonkTcType tau `thenNF_Tc` \ new_tau -> - returnNF_Tc (Method u new_id new_tys new_theta new_tau orig loc) + zonkTcTypes tys `thenM` \ new_tys -> + zonkTcThetaType theta `thenM` \ new_theta -> + zonkTcType tau `thenM` \ new_tau -> + returnM (Method m new_id new_tys new_theta new_tau loc) + +zonkInst (LitInst id lit ty loc) + = zonkTcType ty `thenM` \ new_ty -> + returnM (LitInst id lit new_ty loc) -zonkInst (LitInst u lit ty orig loc) - = zonkTcType ty `thenNF_Tc` \ new_ty -> - returnNF_Tc (LitInst u lit new_ty orig loc) +zonkInsts insts = mappM zonkInst insts \end{code} -Printing -~~~~~~~~ +%************************************************************************ +%* * +\subsection{Printing} +%* * +%************************************************************************ + ToDo: improve these pretty-printing things. The ``origin'' is really only relevant in error messages. @@ -429,289 +465,215 @@ relevant in error messages. instance Outputable Inst where ppr inst = pprInst inst -pprInst (LitInst u lit ty orig loc) - = hsep [case lit of - OverloadedIntegral i -> integer i - OverloadedFractional f -> rational f, - ptext SLIT("at"), - ppr ty, - show_uniq u] +pprInsts :: [Inst] -> SDoc +pprInsts insts = parens (sep (punctuate comma (map pprInst insts))) -pprInst (Dict u clas tys orig loc) = pprConstraint clas tys <+> show_uniq u +pprInstsInFull insts + = vcat (map go insts) + where + 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] + +pprInst (Dict u pred loc) = pprPred pred <+> show_uniq u -pprInst (Method u id tys _ _ orig loc) +pprInst m@(Method u id tys theta tau loc) = hsep [ppr id, ptext SLIT("at"), - brackets (interppSP tys), - show_uniq u] + brackets (sep (map pprParendType tys)) {- , + ptext SLIT("theta"), ppr theta, + ptext SLIT("tau"), ppr tau + show_uniq u, + ppr (instToId m) -}] -tidyInst :: TidyEnv -> Inst -> (TidyEnv, Inst) -tidyInst env (LitInst u lit ty orig loc) - = (env', LitInst u lit ty' orig loc) - where - (env', ty') = tidyOpenType env ty +show_uniq u = ifPprDebug (text "{-" <> ppr u <> text "-}") -tidyInst env (Dict u clas tys orig loc) - = (env', Dict u clas tys' orig loc) - where - (env', tys') = tidyOpenTypes env tys +tidyInst :: TidyEnv -> Inst -> Inst +tidyInst env (LitInst u lit ty loc) = LitInst u lit (tidyType env ty) loc +tidyInst env (Dict u pred loc) = Dict u (tidyPred env pred) loc +tidyInst env (Method u id tys theta tau loc) = Method u id (tidyTypes env tys) theta tau loc -tidyInst env (Method u id tys theta tau orig loc) - = (env', Method u id tys' theta tau orig loc) - -- Leave theta, tau alone cos we don't print them +tidyMoreInsts :: TidyEnv -> [Inst] -> (TidyEnv, [Inst]) +-- This function doesn't assume that the tyvars are in scope +-- so it works like tidyOpenType, returning a TidyEnv +tidyMoreInsts env insts + = (env', map (tidyInst env') insts) where - (env', tys') = tidyOpenTypes env tys - -tidyInsts env insts = mapAccumL tidyInst env insts + env' = tidyFreeTyVars env (tyVarsOfInsts insts) -show_uniq u = ifPprDebug (text "{-" <> ppr u <> text "-}") +tidyInsts :: [Inst] -> (TidyEnv, [Inst]) +tidyInsts insts = tidyMoreInsts emptyTidyEnv insts + +showLIE :: String -> TcM () -- Debugging +showLIE str + = do { lie_var <- getLIEVar ; + lie <- readMutVar lie_var ; + traceTc (text str <+> pprInstsInFull (lieToList lie)) } \end{code} %************************************************************************ %* * -\subsection[InstEnv-types]{Type declarations} +\subsection{Looking up Insts} %* * %************************************************************************ \begin{code} -type InstanceMapper = Class -> InstEnv -\end{code} - -A @ClassInstEnv@ lives inside a class, and identifies all the instances -of that class. The @Id@ inside a ClassInstEnv mapping is the dfun for -that instance. - -There is an important consistency constraint between the @MatchEnv@s -in and the dfun @Id@s inside them: the free type variables of the -@Type@ key in the @MatchEnv@ must be a subset of the universally-quantified -type variables of the dfun. Thus, the @ClassInstEnv@ for @Eq@ might -contain the following entry: -@ - [a] ===> dfun_Eq_List :: forall a. Eq a => Eq [a] -@ -The "a" in the pattern must be one of the forall'd variables in -the dfun type. - -\begin{code} data LookupInstResult s = NoInstance | SimpleInst TcExpr -- Just a variable, type application, or literal | GenInst [Inst] TcExpr -- The expression and its needed insts -lookupInst :: Inst - -> NF_TcM s (LookupInstResult s) +lookupInst :: Inst -> TcM (LookupInstResult s) +-- It's important that lookupInst does not put any new stuff into +-- the LIE. Instead, any Insts needed by the lookup are returned in +-- the LookupInstResult, where they can be further processed by tcSimplify --- Dictionaries -lookupInst dict@(Dict _ clas tys orig loc) - = case lookupInstEnv (ppr clas) (classInstEnv clas) tys of - - Just (tenv, dfun_id) - -> let - subst = mkSubst (tyVarsOfTypes tys) tenv - (tyvars, rho) = splitForAllTys (idType dfun_id) - ty_args = map subst_tv tyvars - dfun_rho = substTy subst rho - (theta, tau) = splitRhoTy dfun_rho - ty_app = mkHsTyApp (HsVar dfun_id) ty_args - subst_tv tv = case lookupSubstEnv tenv tv of - Just (DoneTy ty) -> ty - -- tenv should bind all the tyvars +-- Dictionaries +lookupInst dict@(Dict _ pred@(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. + getStage `thenM` \ use_stage -> + checkWellStaged (ptext SLIT("instance for") <+> quotes (ppr pred)) + (topIdLvl dfun_id) use_stage `thenM_` + traceTc (text "lookupInst" <+> ppr dfun_id <+> ppr (topIdLvl dfun_id) <+> ppr 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 - returnNF_Tc (SimpleInst ty_app) + returnM (SimpleInst ty_app) else - newDictsAtLoc orig loc theta `thenNF_Tc` \ (dicts, dict_ids) -> + newDictsAtLoc loc theta `thenM` \ dicts -> let - rhs = mkHsDictApp ty_app dict_ids + rhs = mkHsDictApp ty_app (map instToId dicts) in - returnNF_Tc (GenInst dicts rhs) - - Nothing -> returnNF_Tc NoInstance + returnM (GenInst dicts rhs) --- Methods + other -> returnM NoInstance -lookupInst inst@(Method _ id tys theta _ orig loc) - = newDictsAtLoc orig loc theta `thenNF_Tc` \ (dicts, dict_ids) -> - returnNF_Tc (GenInst dicts (mkHsDictApp (mkHsTyApp (HsVar id) tys) dict_ids)) +lookupInst (Dict _ _ _) = returnM NoInstance --- Literals - -lookupInst inst@(LitInst u (OverloadedIntegral i) ty orig loc) - | isIntTy ty && in_int_range -- Short cut for Int - = returnNF_Tc (GenInst [] int_lit) - -- GenInst, not SimpleInst, because int_lit is actually a constructor application - - | isIntegerTy ty -- Short cut for Integer - = returnNF_Tc (GenInst [] integer_lit) +-- Methods - | in_int_range -- It's overloaded but small enough to fit into an Int - = tcLookupValueByKey fromIntClassOpKey `thenNF_Tc` \ from_int -> - newMethodAtLoc orig loc from_int [ty] `thenNF_Tc` \ (method_inst, method_id) -> - returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) int_lit)) +lookupInst inst@(Method _ id tys theta _ loc) + = newDictsAtLoc loc theta `thenM` \ dicts -> + returnM (GenInst dicts (mkHsDictApp (mkHsTyApp (HsVar id) tys) (map instToId dicts))) - | otherwise -- Alas, it is overloaded and a big literal! - = tcLookupValueByKey fromIntegerClassOpKey `thenNF_Tc` \ from_integer -> - newMethodAtLoc orig loc from_integer [ty] `thenNF_Tc` \ (method_inst, method_id) -> - returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) integer_lit)) - where - in_int_range = inIntRange i - intprim_lit = HsLitOut (HsIntPrim i) intPrimTy - integer_lit = HsLitOut (HsInt i) integerTy - int_lit = HsCon intDataCon [] [intprim_lit] +-- Literals --- similar idea for overloaded floating point literals: if the literal is --- *definitely* a float or a double, generate the real thing here. +-- Look for short cuts first: if the literal is *definitely* a +-- int, integer, float or a double, generate the real thing here. -- This is essential (see nofib/spectral/nucleic). - -lookupInst inst@(LitInst u (OverloadedFractional f) ty orig loc) - | isFloatTy ty = returnNF_Tc (GenInst [] float_lit) - | isDoubleTy ty = returnNF_Tc (GenInst [] double_lit) - - | otherwise - = tcLookupValueByKey fromRationalClassOpKey `thenNF_Tc` \ from_rational -> - - -- The type Rational isn't wired in so we have to conjure it up - tcLookupTyConByKey rationalTyConKey `thenNF_Tc` \ rational_tycon -> - let - rational_ty = mkSynTy rational_tycon [] - rational_lit = HsLitOut (HsFrac f) rational_ty - in - newMethodAtLoc orig loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) -> - returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) rational_lit)) - - where - floatprim_lit = HsLitOut (HsFloatPrim f) floatPrimTy - float_lit = HsCon floatDataCon [] [floatprim_lit] - doubleprim_lit = HsLitOut (HsDoublePrim f) doublePrimTy - double_lit = HsCon doubleDataCon [] [doubleprim_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. - -\begin{code} -lookupSimpleInst :: InstEnv - -> Class - -> [Type] -- Look up (c,t) - -> NF_TcM s (Maybe ThetaType) -- Here are the needed (c,t)s - -lookupSimpleInst class_inst_env clas tys - = case lookupInstEnv (ppr clas) class_inst_env tys of - Nothing -> returnNF_Tc Nothing - - Just (tenv, dfun) - -> returnNF_Tc (Just (substTheta (mkSubst emptyInScopeSet tenv) theta)) - where - (_, theta, _) = splitSigmaTy (idType dfun) +-- [Same shortcut as in newOverloadedLit, but we +-- may have done some unification by now] + + +lookupInst inst@(LitInst u (HsIntegral i from_integer_name) ty loc) + | Just expr <- shortCutIntLit i ty + = returnM (GenInst [] expr) -- GenInst, not SimpleInst, because + -- expr may be a constructor application + | otherwise + = ASSERT( from_integer_name == fromIntegerName ) -- A LitInst invariant + tcLookupId fromIntegerName `thenM` \ from_integer -> + tcInstClassOp loc from_integer [ty] `thenM` \ method_inst -> + returnM (GenInst [method_inst] + (HsApp (HsVar (instToId method_inst)) (HsLit (HsInteger i)))) + + +lookupInst inst@(LitInst u (HsFractional f from_rat_name) ty loc) + | Just expr <- shortCutFracLit f ty + = returnM (GenInst [] expr) + + | otherwise + = ASSERT( from_rat_name == fromRationalName ) -- A LitInst invariant + tcLookupId fromRationalName `thenM` \ from_rational -> + 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} %************************************************************************ %* * -\subsection[Inst-origin]{The @InstOrigin@ type} + Re-mappable syntax %* * %************************************************************************ -The @InstOrigin@ type gives information about where a dictionary came from. -This is important for decent error message reporting because dictionaries -don't appear in the original source code. Doubtless this type will evolve... -\begin{code} -data InstOrigin - = OccurrenceOf TcId -- Occurrence of an overloaded identifier - | OccurrenceOfCon Id -- Occurrence of a data constructor - - | RecordUpdOrigin - - | DataDeclOrigin -- Typechecking a data declaration - - | InstanceDeclOrigin -- Typechecking an instance decl - - | LiteralOrigin HsLit -- Occurrence of a literal - - | PatOrigin RenamedPat - - | ArithSeqOrigin RenamedArithSeqInfo -- [x..], [x..y] etc - - | SignatureOrigin -- A dict created from a type signature - | Rank2Origin -- A dict created when typechecking the argument - -- of a rank-2 typed function - - | DoOrigin -- The monad for a do expression +Suppose we are doing the -fno-implicit-prelude thing, and we encounter +a do-expression. We have to find (>>) in the current environment, which is +done by the rename. Then we have to check that it has the same type as +Control.Monad.(>>). Or, more precisely, a compatible type. One 'customer' had +this: - | ClassDeclOrigin -- Manufactured during a class decl + (>>) :: HB m n mn => m a -> n b -> mn b - | InstanceSpecOrigin Class -- in a SPECIALIZE instance pragma - Type +So the idea is to generate a local binding for (>>), thus: - -- When specialising instances the instance info attached to - -- each class is not yet ready, so we record it inside the - -- origin information. This is a bit of a hack, but it works - -- fine. (Patrick is to blame [WDP].) + let then72 :: forall a b. m a -> m b -> m b + then72 = ...something involving the user's (>>)... + in + ...the do-expression... - | ValSpecOrigin Name -- in a SPECIALIZE pragma for a value +Now the do-expression can proceed using then72, which has exactly +the expected type. - -- Argument or result of a ccall - -- Dictionaries with this origin aren't actually mentioned in the - -- translated term, and so need not be bound. Nor should they - -- be abstracted over. - - | CCallOrigin String -- CCall label - (Maybe RenamedHsExpr) -- Nothing if it's the result - -- Just arg, for an argument - - | LitLitOrigin String -- the litlit - - | UnknownOrigin -- Help! I give up... -\end{code} +In fact tcSyntaxName just generates the RHS for then72, because we only +want an actual binding in the do-expression case. For literals, we can +just use the expression inline. \begin{code} -pprOrigin :: Inst -> SDoc -pprOrigin inst - = hsep [text "arising from", pp_orig orig, text "at", ppr locn] - where - (orig, locn) = case inst of - Dict _ _ _ orig loc -> (orig,loc) - Method _ _ _ _ _ orig loc -> (orig,loc) - LitInst _ _ _ orig loc -> (orig,loc) - - pp_orig (OccurrenceOf id) - = hsep [ptext SLIT("use of"), quotes (ppr id)] - pp_orig (OccurrenceOfCon id) - = hsep [ptext SLIT("use of"), quotes (ppr id)] - pp_orig (LiteralOrigin lit) - = hsep [ptext SLIT("the literal"), quotes (ppr lit)] - pp_orig (PatOrigin pat) - = hsep [ptext SLIT("the pattern"), quotes (ppr pat)] - pp_orig (InstanceDeclOrigin) - = ptext SLIT("an instance declaration") - pp_orig (ArithSeqOrigin seq) - = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)] - pp_orig (SignatureOrigin) - = ptext SLIT("a type signature") - pp_orig (Rank2Origin) - = ptext SLIT("a function with an overloaded argument type") - pp_orig (DoOrigin) - = ptext SLIT("a do statement") - pp_orig (ClassDeclOrigin) - = ptext SLIT("a class declaration") - pp_orig (InstanceSpecOrigin clas ty) - = hsep [text "a SPECIALIZE instance pragma; class", - quotes (ppr clas), text "type:", ppr ty] - pp_orig (ValSpecOrigin name) - = hsep [ptext SLIT("a SPECIALIZE user-pragma for"), quotes (ppr name)] - pp_orig (CCallOrigin clabel Nothing{-ccall result-}) - = hsep [ptext SLIT("the result of the _ccall_ to"), quotes (text clabel)] - pp_orig (CCallOrigin clabel (Just arg_expr)) - = hsep [ptext SLIT("an argument in the _ccall_ to"), quotes (text clabel) <> comma, - text "namely", quotes (ppr arg_expr)] - pp_orig (LitLitOrigin s) - = hsep [ptext SLIT("the ``literal-literal''"), quotes (text s)] - pp_orig (UnknownOrigin) - = ptext SLIT("...oops -- I don't know where the overloading came from!") +tcSyntaxName :: InstOrigin + -> TcType -- Type to instantiate it at + -> Name -> Name -- (Standard name, user name) + -> TcM (TcExpr, TcType) -- Suitable expression with its type + +-- 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 + | std_nm == user_nm + = newMethodFromName orig ty std_nm `thenM` \ id -> + returnM (HsVar id, idType id) + + | otherwise + = tcLookupId std_nm `thenM` \ std_id -> + let + -- C.f. newMethodAtLoc + ([tv], _, tau) = tcSplitSigmaTy (idType std_id) + tau1 = substTyWith [tv] [ty] tau + in + addErrCtxtM (syntaxNameCtxt user_nm orig tau1) $ + tcExpr (HsVar user_nm) tau1 `thenM` \ user_fn -> + returnM (user_fn, tau1) + +syntaxNameCtxt name orig ty tidy_env + = getInstLoc orig `thenM` \ inst_loc -> + let + msg = vcat [ptext SLIT("When checking that") <+> quotes (ppr name) <+> + ptext SLIT("(needed by a syntactic construct)"), + nest 2 (ptext SLIT("has the required type:") <+> ppr (tidyType tidy_env ty)), + nest 2 (pprInstLoc inst_loc)] + in + returnM (tidy_env, msg) \end{code}