%
-% (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
@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}
projects / ghc-hetmet.git / blobdiff