X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FInst.lhs;h=09272ad88e1f6421a5b1ef5e896b21659e2e5204;hb=8655d6ca41df4aa77a559d4067ad3815797b9803;hp=e4a95844b28db6278d8ce2d359a3af471085e23b;hpb=7d61cb61daa5e433a0cb85b34b7f0c58b2f961ff;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/Inst.lhs b/ghc/compiler/typecheck/Inst.lhs index e4a9584..9f3c684 100644 --- a/ghc/compiler/typecheck/Inst.lhs +++ b/ghc/compiler/typecheck/Inst.lhs @@ -1,314 +1,188 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[Inst]{The @Inst@ type: dictionaries or method instances} \begin{code} -#include "HsVersions.h" - -module Inst ( - Inst(..), -- Visible only to TcSimplify +module Inst ( + LIE, emptyLIE, unitLIE, plusLIE, consLIE, + plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE, + showLIE, - InstOrigin(..), OverloadedLit(..), - LIE(..), emptyLIE, unitLIE, plusLIE, consLIE, zonkLIE, plusLIEs, + Inst, + pprInst, pprInsts, pprInstsInFull, tidyInsts, tidyMoreInsts, - InstanceMapper(..), + newDictsFromOld, newDicts, cloneDict, + newOverloadedLit, newIPDict, + newMethod, newMethodFromName, newMethodWithGivenTy, + tcInstClassOp, tcInstCall, tcInstDataCon, + tcSyntaxName, tcStdSyntaxName, - newDicts, newDictsAtLoc, newMethod, newMethodWithGivenTy, newOverloadedLit, + tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE, + ipNamesOfInst, ipNamesOfInsts, fdPredsOfInst, fdPredsOfInsts, + instLoc, getDictClassTys, dictPred, - instType, tyVarsOfInst, lookupInst, + lookupInst, LookupInstResult(..), - isDict, isTyVarDict, + isDict, isClassDict, isMethod, + isLinearInst, linearInstType, isIPDict, isInheritableInst, + isTyVarDict, isStdClassTyVarDict, isMethodFor, + instBindingRequired, instCanBeGeneralised, - zonkInst, instToId, - - matchesInst, - instBindingRequired, instCanBeGeneralised + zonkInst, zonkInsts, + instToId, instName, + InstOrigin(..), InstLoc(..), pprInstLoc ) where -import Ubiq - -import HsSyn ( HsLit(..), HsExpr(..), HsBinds, - InPat, OutPat, Stmt, Qual, Match, - ArithSeqInfo, PolyType, Fake ) -import RnHsSyn ( RenamedArithSeqInfo(..), RenamedHsExpr(..) ) -import TcHsSyn ( TcIdOcc(..), TcExpr(..), TcIdBndr(..), - mkHsTyApp, mkHsDictApp ) - -import TcMonad -import TcEnv ( tcLookupGlobalValueByKey ) -import TcType ( TcType(..), TcRhoType(..), TcMaybe, TcTyVarSet(..), - tcInstType, tcInstTcType, zonkTcType ) - -import Bag ( emptyBag, unitBag, unionBags, unionManyBags, listToBag, consBag ) -import Class ( Class(..), GenClass, ClassInstEnv(..), getClassInstEnv ) -import Id ( GenId, idType, mkInstId ) -import MatchEnv ( lookupMEnv, insertMEnv ) -import Name ( Name ) -import NameTypes( ShortName, mkShortName ) -import Outputable -import PprType ( GenClass, TyCon, GenType, GenTyVar ) -import PprStyle ( PprStyle(..) ) -import Pretty -import SpecEnv ( SpecEnv(..) ) -import SrcLoc ( SrcLoc, mkUnknownSrcLoc ) -import Type ( GenType, eqSimpleTy, - isTyVarTy, mkDictTy, splitForAllTy, splitSigmaTy, - splitRhoTy, matchTy, tyVarsOfType, tyVarsOfTypes ) -import TyVar ( GenTyVar ) -import TysPrim ( intPrimTy ) -import TysWiredIn ( intDataCon ) -import Unique ( Unique, showUnique, - fromRationalClassOpKey, fromIntClassOpKey, fromIntegerClassOpKey ) -import Util ( panic, zipEqual, zipWithEqual, assoc, assertPanic ) +#include "HsVersions.h" +import {-# SOURCE #-} TcExpr( tcCheckSigma ) + +import HsSyn ( HsLit(..), HsOverLit(..), HsExpr(..) ) +import TcHsSyn ( TcExpr, TcId, TcIdSet, + mkHsTyApp, mkHsDictApp, mkHsConApp, zonkId, + mkCoercion, ExprCoFn + ) +import TcRnMonad +import TcEnv ( tcGetInstEnv, tcLookupId, tcLookupTyCon, checkWellStaged, topIdLvl ) +import InstEnv ( InstLookupResult(..), lookupInstEnv ) +import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType, + zonkTcThetaType, tcInstTyVar, tcInstType, tcInstTyVars + ) +import TcType ( Type, TcType, TcThetaType, TcTyVarSet, + SourceType(..), PredType, TyVarDetails(VanillaTv), + tcSplitForAllTys, tcSplitForAllTys, mkTyConApp, + tcSplitPhiTy, mkGenTyConApp, + isIntTy,isFloatTy, isIntegerTy, isDoubleTy, + tcIsTyVarTy, mkPredTy, mkTyVarTy, mkTyVarTys, + tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tidyPred, + isClassPred, isTyVarClassPred, isLinearPred, + getClassPredTys, getClassPredTys_maybe, mkPredName, + isInheritablePred, isIPPred, + tidyType, tidyTypes, tidyFreeTyVars, tcSplitSigmaTy + ) +import CoreFVs ( idFreeTyVars ) +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 ( 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 s = Bag (Inst s) +instName :: Inst -> Name +instName inst = idName (instToId inst) -emptyLIE = emptyBag -unitLIE inst = unitBag inst -plusLIE lie1 lie2 = lie1 `unionBags` lie2 -consLIE inst lie = inst `consBag` lie -plusLIEs lies = unionManyBags lies +instToId :: Inst -> TcId +instToId (Dict id _ _) = id +instToId (Method id _ _ _ _ _) = id +instToId (LitInst id _ _ _) = id -zonkLIE :: LIE s -> NF_TcM s (LIE s) -zonkLIE lie = mapBagNF_Tc zonkInst lie -\end{code} +instLoc (Dict _ _ loc) = loc +instLoc (Method _ _ _ _ _ loc) = loc +instLoc (LitInst _ _ _ loc) = loc -%************************************************************************ -%* * -\subsection[Inst-types]{@Inst@ types} -%* * -%************************************************************************ +dictPred (Dict _ pred _ ) = pred +dictPred inst = pprPanic "dictPred" (ppr inst) -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 +getDictClassTys (Dict _ pred _) = getClassPredTys pred - Method 34 doubleId [Int] origin +-- fdPredsOfInst is used to get predicates that contain functional +-- 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 -\begin{code} -data Inst s - = Dict - Unique - Class -- The type of the dict is (c t), where - (TcType s) -- c is the class and t the type; - (InstOrigin s) - SrcLoc - - | Method - Unique - - (TcIdOcc s) -- 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 s] -- The types to which its polymorphic tyvars - -- should be instantiated. - -- These types must saturate the Id's foralls. - - (TcRhoType s) -- Cached: (type-of-id applied to inst_tys) - -- If this type is (theta => tau) then the type of the Method - -- is tau, and the method can be built by saying - -- id inst_tys dicts - -- where dicts are constructed from theta - - (InstOrigin s) - SrcLoc - - | LitInst - Unique - OverloadedLit - (TcType s) -- The type at which the literal is used - (InstOrigin s) -- Always a literal; but more convenient to carry this around - SrcLoc - -data OverloadedLit - = OverloadedIntegral Integer -- The number - | OverloadedFractional Rational -- The number - -getInstOrigin (Dict u clas ty origin loc) = origin -getInstOrigin (Method u clas ty rho origin loc) = origin -getInstOrigin (LitInst u lit ty origin loc) = origin -\end{code} +fdPredsOfInsts :: [Inst] -> [PredType] +fdPredsOfInsts insts = concatMap fdPredsOfInst insts -Construction -~~~~~~~~~~~~ +isInheritableInst (Dict _ pred _) = isInheritablePred pred +isInheritableInst (Method _ _ _ theta _ _) = all isInheritablePred theta +isInheritableInst other = True -\begin{code} -newDicts :: InstOrigin s - -> [(Class, TcType s)] - -> NF_TcM s (LIE s, [TcIdOcc s]) -newDicts orig theta - = tcGetSrcLoc `thenNF_Tc` \ loc -> - tcGetUniques (length theta) `thenNF_Tc` \ new_uniqs -> - let - mk_dict u (clas, ty) = Dict u clas ty orig loc - dicts = zipWithEqual mk_dict new_uniqs theta - in - returnNF_Tc (listToBag dicts, map instToId dicts) - -newDictsAtLoc orig loc theta -- Local function, similar to newDicts, - -- but with slightly different interface - = tcGetUniques (length theta) `thenNF_Tc` \ new_uniqs -> - let - mk_dict u (clas, ty) = Dict u clas ty orig loc - dicts = zipWithEqual mk_dict new_uniqs theta - in - returnNF_Tc (dicts, map instToId dicts) - -newMethod :: InstOrigin s - -> TcIdOcc s - -> [TcType s] - -> NF_TcM s (LIE s, TcIdOcc s) -newMethod orig id tys - = -- Get the Id type and instantiate it at the specified types - (case id of - RealId id -> let (tyvars, rho) = splitForAllTy (idType id) - in tcInstType (tyvars `zipEqual` tys) rho - TcId id -> let (tyvars, rho) = splitForAllTy (idType id) - in tcInstTcType (tyvars `zipEqual` tys) rho - ) `thenNF_Tc` \ rho_ty -> - - -- Our friend does the rest - newMethodWithGivenTy orig id tys rho_ty - - -newMethodWithGivenTy orig id tys rho_ty - = tcGetSrcLoc `thenNF_Tc` \ loc -> - tcGetUnique `thenNF_Tc` \ new_uniq -> - let - meth_inst = Method new_uniq id tys rho_ty orig loc - in - returnNF_Tc (unitLIE meth_inst, instToId meth_inst) - -newMethodAtLoc :: InstOrigin s -> SrcLoc -> Id -> [TcType s] -> NF_TcM s (Inst s, TcIdOcc s) -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 - let - (tyvars,rho) = splitForAllTy (idType real_id) - in - tcInstType (tyvars `zipEqual` tys) rho `thenNF_Tc` \ rho_ty -> - tcGetUnique `thenNF_Tc` \ new_uniq -> - let - meth_inst = Method new_uniq (RealId real_id) tys rho_ty orig loc - in - returnNF_Tc (meth_inst, instToId meth_inst) - -newOverloadedLit :: InstOrigin s - -> OverloadedLit - -> TcType s - -> NF_TcM s (LIE s, TcIdOcc s) -newOverloadedLit orig lit ty - = tcGetSrcLoc `thenNF_Tc` \ loc -> - tcGetUnique `thenNF_Tc` \ new_uniq -> - let - lit_inst = LitInst new_uniq lit ty orig loc - in - returnNF_Tc (unitLIE lit_inst, instToId lit_inst) -\end{code} +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] -\begin{code} -instToId :: Inst s -> TcIdOcc s -instToId (Dict uniq clas ty orig loc) - = TcId (mkInstId uniq (mkDictTy clas ty) (mkShortName SLIT("dict") loc)) -instToId (Method uniq id tys rho_ty orig loc) - = TcId (mkInstId uniq tau_ty (mkShortName (getOccurrenceName id) loc)) - where - (_, tau_ty) = splitRhoTy rho_ty -- NB The method Id has just the tau type -instToId (LitInst uniq list ty orig loc) - = TcId (mkInstId uniq ty (mkShortName SLIT("lit") loc)) -\end{code} - -\begin{code} -instType :: Inst s -> TcType s -instType (Dict _ clas ty _ _) = mkDictTy clas ty -instType (LitInst _ _ ty _ _) = ty -instType (Method _ id tys ty _ _) = ty -\end{code} +ipNamesOfInst (Dict _ (IParam n _) _) = [ipNameName n] +ipNamesOfInst (Method _ _ _ theta _ _) = [ipNameName n | IParam n _ <- theta] +ipNamesOfInst other = [] +tyVarsOfInst :: Inst -> TcTyVarSet +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 -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 -need, and it's a lot of extra work. -\begin{code} -zonkInst :: Inst s -> NF_TcM s (Inst s) -zonkInst (Dict uniq clas ty orig loc) - = zonkTcType ty `thenNF_Tc` \ new_ty -> - returnNF_Tc (Dict uniq clas new_ty orig loc) - -zonkInst (Method uniq id tys rho orig loc) -- Doesn't zonk the id! - = mapNF_Tc zonkTcType tys `thenNF_Tc` \ new_tys -> - zonkTcType rho `thenNF_Tc` \ new_rho -> - returnNF_Tc (Method uniq id new_tys new_rho orig loc) - -zonkInst (LitInst uniq lit ty orig loc) - = zonkTcType ty `thenNF_Tc` \ new_ty -> - returnNF_Tc (LitInst uniq lit new_ty orig loc) +tyVarsOfInsts insts = foldr (unionVarSet . tyVarsOfInst) emptyVarSet insts +tyVarsOfLIE lie = tyVarsOfInsts (lieToList lie) \end{code} - +Predicates +~~~~~~~~~~ \begin{code} -tyVarsOfInst :: Inst s -> TcTyVarSet s -tyVarsOfInst (Dict _ _ ty _ _) = tyVarsOfType ty -tyVarsOfInst (Method _ _ tys rho _ _) = tyVarsOfTypes tys -tyVarsOfInst (LitInst _ _ ty _ _) = tyVarsOfType ty -\end{code} +isDict :: Inst -> Bool +isDict (Dict _ _ _) = True +isDict other = False -@matchesInst@ checks when two @Inst@s are instances of the same -thing at the same type, even if their uniques differ. +isClassDict :: Inst -> Bool +isClassDict (Dict _ pred _) = isClassPred pred +isClassDict other = False -\begin{code} -matchesInst :: Inst s -> Inst s -> Bool +isTyVarDict :: Inst -> Bool +isTyVarDict (Dict _ pred _) = isTyVarClassPred pred +isTyVarDict other = False -matchesInst (Dict _ clas1 ty1 _ _) (Dict _ clas2 ty2 _ _) - = clas1 == clas2 && ty1 `eqSimpleTy` ty2 +isIPDict :: Inst -> Bool +isIPDict (Dict _ pred _) = isIPPred pred +isIPDict other = False -matchesInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) - = id1 == id2 - && and (zipWith eqSimpleTy tys1 tys2) - && length tys1 == length tys2 +isMethod :: Inst -> Bool +isMethod (Method _ _ _ _ _ _) = True +isMethod other = False -matchesInst (LitInst _ lit1 ty1 _ _) (LitInst _ lit2 ty2 _ _) - = lit1 `eq` lit2 && ty1 `eqSimpleTy` ty2 - where - (OverloadedIntegral i1) `eq` (OverloadedIntegral i2) = i1 == i2 - (OverloadedFractional f1) `eq` (OverloadedFractional f2) = f1 == f2 - _ `eq` _ = False +isMethodFor :: TcIdSet -> Inst -> Bool +isMethodFor ids (Method uniq id tys _ _ loc) = id `elemVarSet` ids +isMethodFor ids inst = False -matchesInst other1 other2 = False -\end{code} +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 -Predicates -~~~~~~~~~~ -\begin{code} -isDict :: Inst s -> Bool -isDict (Dict _ _ _ _ _) = True -isDict other = False -isTyVarDict :: Inst s -> Bool -isTyVarDict (Dict _ _ ty _ _) = isTyVarTy ty -isTyVarDict other = False +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 @@ -317,334 +191,500 @@ must be witnessed by an actual binding; the second tells whether an @Inst@ can be generalised over. \begin{code} -instBindingRequired :: Inst s -> Bool -instBindingRequired inst - = case getInstOrigin inst of - CCallOrigin _ _ -> False -- No binding required - LitLitOrigin _ -> False - OccurrenceOfCon _ -> False - other -> True - -instCanBeGeneralised :: Inst s -> Bool -instCanBeGeneralised inst - = case getInstOrigin inst of - CCallOrigin _ _ -> False -- Can't be generalised - LitLitOrigin _ -> False -- Can't be generalised - other -> True +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} -Printing -~~~~~~~~ -ToDo: improve these pretty-printing things. The ``origin'' is really only -relevant in error messages. +%************************************************************************ +%* * +\subsection{Building dictionaries} +%* * +%************************************************************************ \begin{code} -instance Outputable (Inst s) where - ppr sty (LitInst uniq lit ty orig loc) - = ppHang (ppSep [case lit of - OverloadedIntegral i -> ppInteger i - OverloadedFractional f -> ppRational f, - ppStr "at", - ppr sty ty, - show_uniq sty uniq - ]) - 4 (show_origin sty orig) - - ppr sty (Dict uniq clas ty orig loc) - = ppHang (ppSep [ppr sty clas, - ppStr "at", - ppr sty ty, - show_uniq sty uniq - ]) - 4 (show_origin sty orig) - - ppr sty (Method uniq id tys rho orig loc) - = ppHang (ppSep [ppr sty id, - ppStr "at", - ppr sty tys, - show_uniq sty uniq - ]) - 4 (show_origin sty orig) - -show_uniq PprDebug uniq = ppr PprDebug uniq -show_uniq sty uniq = ppNil - -show_origin sty orig = ppBesides [ppLparen, pprOrigin sty orig, ppRparen] +newDicts :: InstOrigin + -> TcThetaType + -> TcM [Inst] +newDicts orig theta + = 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 :: InstLoc + -> TcThetaType + -> 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 + pred = IParam ip_name ty + id = mkLocalId (mkPredName uniq loc pred) (mkPredTy pred) + in + returnM (mapIPName (\n -> id) ip_name, Dict id pred inst_loc) \end{code} -Printing in error messages -\begin{code} -noInstanceErr inst sty = ppHang (ppPStr SLIT("No instance for:")) 4 (ppr sty inst) -\end{code} %************************************************************************ %* * -\subsection[InstEnv-types]{Type declarations} +\subsection{Building methods (calls of overloaded functions)} %* * %************************************************************************ + \begin{code} -type InstanceMapper = Class -> (ClassInstEnv, ClassOp -> SpecEnv) +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 -> + extendLIEs dicts `thenM_` + let + inst_fn e = mkHsDictApp (mkHsTyApp e (mkTyVarTys tyvars)) (map instToId dicts) + in + returnM (mkCoercion 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 + 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 + 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 + 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 \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. +In newOverloadedLit we convert directly to an Int or Integer if we +know that's what we want. This may save some time, by not +temporarily generating overloaded literals, but it won't catch all +cases (the rest are caught in lookupInst). \begin{code} -lookupInst :: Inst s - -> TcM s ([Inst s], - (TcIdOcc s, TcExpr s)) -- The new binding +newOverloadedLit :: InstOrigin + -> HsOverLit + -> TcType + -> 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, HsVar 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, HsVar 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 -> + let + lit_inst = LitInst lit_id lit expected_ty loc + lit_id = mkSysLocal FSLIT("lit") new_uniq expected_ty + in + 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} --- Dictionaries -lookupInst dict@(Dict _ clas ty orig loc) - = case lookupMEnv matchTy (get_inst_env clas orig) ty of - Nothing -> failTc (noInstanceErr dict) +%************************************************************************ +%* * +\subsection{Zonking} +%* * +%************************************************************************ - Just (dfun_id, tenv) - -> let - (tyvars, rho) = splitForAllTy (idType dfun_id) - ty_args = map (assoc "lookupInst" tenv) tyvars - -- tenv should bind all the tyvars - in - tcInstType tenv rho `thenNF_Tc` \ dfun_rho -> - let - (theta, tau) = splitRhoTy dfun_rho - in - newDictsAtLoc orig loc theta `thenNF_Tc` \ (dicts, dict_ids) -> - let - rhs = mkHsDictApp (mkHsTyApp (HsVar (RealId dfun_id)) ty_args) dict_ids - in - returnTc (dicts, (instToId dict, rhs)) - +Zonking makes sure that the instance types are fully zonked, +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. --- Methods +\begin{code} +zonkInst :: Inst -> TcM Inst +zonkInst (Dict id pred loc) + = zonkTcPredType pred `thenM` \ new_pred -> + returnM (Dict id new_pred loc) + +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 `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) + +zonkInsts insts = mappM zonkInst insts +\end{code} -lookupInst inst@(Method _ id tys rho orig loc) - = newDictsAtLoc orig loc theta `thenNF_Tc` \ (dicts, dict_ids) -> - returnTc (dicts, (instToId inst, mkHsDictApp (mkHsTyApp (HsVar id) tys) dict_ids)) - where - (theta,_) = splitRhoTy rho --- Literals +%************************************************************************ +%* * +\subsection{Printing} +%* * +%************************************************************************ -lookupInst inst@(LitInst u (OverloadedIntegral i) ty orig loc) - | i >= toInteger minInt && i <= toInteger maxInt - = -- It's overloaded but small enough to fit into an Int - tcLookupGlobalValueByKey fromIntClassOpKey `thenNF_Tc` \ from_int -> - newMethodAtLoc orig loc from_int [ty] `thenNF_Tc` \ (method_inst, method_id) -> - returnTc ([method_inst], (instToId inst, HsApp (HsVar method_id) int_lit)) - - | otherwise - = -- Alas, it is overloaded and a big literal! - tcLookupGlobalValueByKey fromIntegerClassOpKey `thenNF_Tc` \ from_integer -> - newMethodAtLoc orig loc from_integer [ty] `thenNF_Tc` \ (method_inst, method_id) -> - returnTc ([method_inst], (instToId inst, HsApp (HsVar method_id) (HsLitOut (HsInt i) ty))) - where - intprim_lit = HsLitOut (HsIntPrim i) intPrimTy - int_lit = HsApp (HsVar (RealId intDataCon)) intprim_lit +ToDo: improve these pretty-printing things. The ``origin'' is really only +relevant in error messages. -lookupInst inst@(LitInst u (OverloadedFractional f) ty orig loc) - = tcLookupGlobalValueByKey fromRationalClassOpKey `thenNF_Tc` \ from_rational -> - newMethodAtLoc orig loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) -> - returnTc ([method_inst], (instToId inst, HsApp (HsVar method_id) (HsLitOut (HsFrac f) ty))) -\end{code} +\begin{code} +instance Outputable Inst where + ppr inst = pprInst inst -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. +pprInsts :: [Inst] -> SDoc +pprInsts insts = parens (sep (punctuate comma (map pprInst insts))) -\begin{code} -lookupClassInstAtSimpleType :: Class -> Type -> Maybe Id - -lookupClassInstAtSimpleType clas ty - = case (lookupMEnv matchTy (getClassInstEnv clas) ty) of - Nothing -> Nothing - Just (dfun,_) -> ASSERT( null tyvars && null theta ) - Just dfun - where - (tyvars, theta, _) = splitSigmaTy (idType dfun) -\end{code} +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] -@mkInstSpecEnv@ is used to construct the @SpecEnv@ for a dfun. -It does it by filtering the class's @InstEnv@. All pretty shady stuff. +pprInst (Dict u pred loc) = pprPred pred <+> show_uniq u -\begin{code} -mkInstSpecEnv clas inst_ty inst_tvs inst_theta = panic "mkInstSpecEnv" -\end{code} +pprInst m@(Method u id tys theta tau loc) + = hsep [ppr id, ptext SLIT("at"), + brackets (sep (map pprParendType tys)) {- , + ptext SLIT("theta"), ppr theta, + ptext SLIT("tau"), ppr tau + show_uniq u, + ppr (instToId m) -}] -\begin{pseudocode} -mkInstSpecEnv :: Class -- class - -> Type -- instance type - -> [TyVarTemplate] -- instance tyvars - -> ThetaType -- superclasses dicts - -> SpecEnv -- specenv for dfun of instance +show_uniq u = ifPprDebug (text "{-" <> ppr u <> text "-}") -mkInstSpecEnv clas inst_ty inst_tvs inst_theta - = mkSpecEnv (catMaybes (map maybe_spec_info matches)) - where - matches = matchMEnv matchTy (getClassInstEnv clas) inst_ty +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 - maybe_spec_info (_, match_info, MkInstTemplate dfun _ []) - = Just (SpecInfo (map (assocMaybe match_info) inst_tvs) (length inst_theta) dfun) - maybe_spec_info (_, match_info, _) - = Nothing -\end{pseudocode} +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' = tidyFreeTyVars env (tyVarsOfInsts insts) +tidyInsts :: [Inst] -> (TidyEnv, [Inst]) +tidyInsts insts = tidyMoreInsts emptyTidyEnv insts -\begin{code} -addClassInst - :: ClassInstEnv -- Incoming envt - -> Type -- The instance type: inst_ty - -> Id -- Dict fun id to apply. Free tyvars of inst_ty must - -- be the same as the forall'd tyvars of the dfun id. - -> MaybeErr - ClassInstEnv -- Success - (Type, Id) -- Offending overlap - -addClassInst inst_env inst_ty dfun_id = insertMEnv matchTy inst_env inst_ty dfun_id +showLIE :: SDoc -> TcM () -- Debugging +showLIE str + = do { lie_var <- getLIEVar ; + lie <- readMutVar lie_var ; + traceTc (str <+> pprInstsInFull (lieToList lie)) } \end{code} - %************************************************************************ %* * -\subsection[Inst-origin]{The @InstOrigin@ type} +\subsection{Looking up Insts} %* * %************************************************************************ -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 s - = OccurrenceOf (TcIdOcc s) -- Occurrence of an overloaded identifier - | OccurrenceOfCon Id -- Occurrence of a data constructor +data LookupInstResult s + = NoInstance + | SimpleInst TcExpr -- Just a variable, type application, or literal + | GenInst [Inst] TcExpr -- The expression and its needed insts - | InstanceDeclOrigin -- Typechecking an instance decl +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 - | LiteralOrigin HsLit -- Occurrence of a literal - | ArithSeqOrigin RenamedArithSeqInfo -- [x..], [x..y] etc +-- 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 + returnM (SimpleInst ty_app) + else + newDictsAtLoc loc theta `thenM` \ dicts -> + let + rhs = mkHsDictApp ty_app (map instToId dicts) + in + returnM (GenInst dicts rhs) - | SignatureOrigin -- A dict created from a type signature + other -> returnM NoInstance - | DoOrigin -- The monad for a do expression +lookupInst (Dict _ _ _) = returnM NoInstance - | ClassDeclOrigin -- Manufactured during a class decl +-- Methods - | DerivingOrigin InstanceMapper - Class - TyCon +lookupInst inst@(Method _ id tys theta _ loc) + = newDictsAtLoc loc theta `thenM` \ dicts -> + returnM (GenInst dicts (mkHsDictApp (mkHsTyApp (HsVar id) tys) (map instToId dicts))) - -- During "deriving" operations we have an ever changing - -- mapping of classes to instances, so we record it inside the - -- origin information. This is a bit of a hack, but it works - -- fine. (Simon is to blame [WDP].) +-- Literals - | InstanceSpecOrigin InstanceMapper - Class -- in a SPECIALIZE instance pragma - Type +-- 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). +-- [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} - -- 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].) - | DefaultDeclOrigin -- Related to a `default' declaration - | ValSpecOrigin Name -- in a SPECIALIZE pragma for a value +%************************************************************************ +%* * + Re-mappable syntax +%* * +%************************************************************************ - -- 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 +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: - | LitLitOrigin String -- the litlit + (>>) :: HB m n mn => m a -> n b -> mn b - | UnknownOrigin -- Help! I give up... -\end{code} +So the idea is to generate a local binding for (>>), thus: -\begin{code} --- During deriving and instance specialisation operations --- we can't get the instances of the class from inside the --- class, because the latter ain't ready yet. Instead we --- find a mapping from classes to envts inside the dict origin. - -get_inst_env :: Class -> InstOrigin s -> ClassInstEnv -get_inst_env clas (DerivingOrigin inst_mapper _ _) - = fst (inst_mapper clas) -get_inst_env clas (InstanceSpecOrigin inst_mapper _ _) - = fst (inst_mapper clas) -get_inst_env clas other_orig = getClassInstEnv clas - - -pprOrigin :: PprStyle -> InstOrigin s -> Pretty - -pprOrigin sty (OccurrenceOf id) - = ppBesides [ppPStr SLIT("at a use of an overloaded identifier: `"), - ppr sty id, ppChar '\''] -pprOrigin sty (OccurrenceOfCon id) - = ppBesides [ppPStr SLIT("at a use of an overloaded constructor: `"), - ppr sty id, ppChar '\''] -pprOrigin sty (InstanceDeclOrigin) - = ppStr "in an instance declaration" -pprOrigin sty (LiteralOrigin lit) - = ppCat [ppStr "at an overloaded literal:", ppr sty lit] -pprOrigin sty (ArithSeqOrigin seq) - = ppCat [ppStr "at an arithmetic sequence:", ppr sty seq] -pprOrigin sty (SignatureOrigin) - = ppStr "in a type signature" -pprOrigin sty (DoOrigin) - = ppStr "in a do statement" -pprOrigin sty (ClassDeclOrigin) - = ppStr "in a class declaration" -pprOrigin sty (DerivingOrigin _ clas tycon) - = ppBesides [ppStr "in a `deriving' clause; class `", - ppr sty clas, - ppStr "'; offending type `", - ppr sty tycon, - ppStr "'"] -pprOrigin sty (InstanceSpecOrigin _ clas ty) - = ppBesides [ppStr "in a SPECIALIZE instance pragma; class \"", - ppr sty clas, ppStr "\" type: ", ppr sty ty] -pprOrigin sty (DefaultDeclOrigin) - = ppStr "in a `default' declaration" -pprOrigin sty (ValSpecOrigin name) - = ppBesides [ppStr "in a SPECIALIZE user-pragma for `", - ppr sty name, ppStr "'"] -pprOrigin sty (CCallOrigin clabel Nothing{-ccall result-}) - = ppBesides [ppStr "in the result of the _ccall_ to `", - ppStr clabel, ppStr "'"] -pprOrigin sty (CCallOrigin clabel (Just arg_expr)) - = ppBesides [ppStr "in an argument in the _ccall_ to `", - ppStr clabel, ppStr "', namely: ", ppr sty arg_expr] -pprOrigin sty (LitLitOrigin s) - = ppBesides [ppStr "in this ``literal-literal'': ", ppStr s] -pprOrigin sty UnknownOrigin - = ppStr "in... oops -- I don't know where the overloading came from!" -\end{code} + let then72 :: forall a b. m a -> m b -> m b + then72 = ...something involving the user's (>>)... + in + ...the do-expression... +Now the do-expression can proceed using then72, which has exactly +the expected type. +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} +tcSyntaxName :: InstOrigin + -> TcType -- Type to instantiate it at + -> (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, HsVar user_nm) + | std_nm == user_nm + = tcStdSyntaxName orig ty std_nm + +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 = 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_expr orig tau1) $ + 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 -> + 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}