%
-% (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
-
- InstOrigin(..), OverloadedLit(..),
- LIE(..), emptyLIE, unitLIE, plusLIE, consLIE, zonkLIE, plusLIEs,
+module Inst (
+ LIE, emptyLIE, unitLIE, plusLIE, consLIE, zonkLIE,
+ plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
- InstanceMapper(..),
+ Inst,
+ pprInst, pprInsts, pprInstsInFull, tidyInst, tidyInsts,
- newDicts, newDictsAtLoc, newMethod, newMethodWithGivenTy, newOverloadedLit,
+ newDictsFromOld, newDicts, newClassDicts,
+ newMethod, newMethodWithGivenTy, newOverloadedLit,
+ newIPDict, tcInstId,
- instType, tyVarsOfInst, lookupInst, lookupSimpleInst,
+ tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE, instLoc, getDictClassTys,
+ getIPs,
+ predsOfInsts,
- isDict, isTyVarDict,
+ lookupInst, lookupSimpleInst, LookupInstResult(..),
- zonkInst, instToId,
-
- matchesInst,
+ isDict, isClassDict, isMethod, instMentionsIPs,
+ isTyVarDict, isStdClassTyVarDict, isMethodFor,
instBindingRequired, instCanBeGeneralised,
-
- pprInst
- ) where
-IMP_Ubiq()
+ zonkInst, zonkInsts,
+ instToId,
-import HsSyn ( HsLit(..), HsExpr(..), HsBinds,
- InPat, OutPat, Stmt, Qualifier, Match,
- ArithSeqInfo, PolyType, Fake )
-import RnHsSyn ( RenamedArithSeqInfo(..), RenamedHsExpr(..) )
-import TcHsSyn ( TcIdOcc(..), TcExpr(..), TcIdBndr(..),
- mkHsTyApp, mkHsDictApp, tcIdTyVars )
+ InstOrigin(..), InstLoc, pprInstLoc
+ ) where
-import TcMonad hiding ( rnMtoTcM )
-import TcEnv ( tcLookupGlobalValueByKey, tcLookupTyConByKey )
-import TcType ( TcType(..), TcRhoType(..), TcMaybe, TcTyVarSet(..),
- tcInstType, zonkTcType )
+#include "HsVersions.h"
-import Bag ( emptyBag, unitBag, unionBags, unionManyBags, listToBag, consBag )
-import Class ( isCcallishClass, isNoDictClass, classInstEnv,
- SYN_IE(Class), GenClass, SYN_IE(ClassInstEnv)
+import CmdLineOpts ( opt_NoMethodSharing )
+import HsSyn ( HsLit(..), HsOverLit(..), HsExpr(..) )
+import TcHsSyn ( TcExpr, TcId,
+ mkHsTyApp, mkHsDictApp, mkHsConApp, zonkId
)
-import ErrUtils ( addErrLoc, SYN_IE(Error) )
-import Id ( GenId, idType, mkInstId )
-import MatchEnv ( lookupMEnv, insertMEnv )
-import Name ( mkLocalName, getLocalName, Name )
-import Outputable
-import PprType ( GenClass, TyCon, GenType, GenTyVar )
-import PprStyle ( PprStyle(..) )
-import Pretty
-import RnHsSyn ( RnName{-instance NamedThing-} )
-import SpecEnv ( SYN_IE(SpecEnv) )
-import SrcLoc ( SrcLoc, mkUnknownSrcLoc )
-import Type ( GenType, eqSimpleTy, instantiateTy,
- isTyVarTy, mkDictTy, splitForAllTy, splitSigmaTy,
- splitRhoTy, matchTy, tyVarsOfType, tyVarsOfTypes,
- mkSynTy
+import TcMonad
+import TcEnv ( TcIdSet, tcGetInstEnv, tcLookupSyntaxId )
+import InstEnv ( InstLookupResult(..), lookupInstEnv )
+import TcType ( TcThetaType, TcClassContext,
+ TcType, TcTauType, TcTyVarSet,
+ zonkTcType, zonkTcTypes,
+ zonkTcThetaType, tcInstTyVar, tcInstType
+ )
+import CoreFVs ( idFreeTyVars )
+import Class ( Class )
+import Id ( Id, idType, mkUserLocal, mkSysLocal, mkLocalId )
+import PrelInfo ( isStandardClass, isCcallishClass, isNoDictClass )
+import Name ( mkDictOcc, mkMethodOcc, getOccName, mkLocalName )
+import NameSet ( NameSet )
+import PprType ( pprPred )
+import Type ( Type, PredType(..),
+ isTyVarTy, mkPredTy, mkTyVarTy, mkTyVarTys,
+ splitForAllTys, splitSigmaTy, funArgTy,
+ splitMethodTy, splitRhoTy, classesOfPreds,
+ tyVarsOfType, tyVarsOfTypes, tyVarsOfPred,
+ tidyOpenType, tidyOpenTypes, predMentionsIPs
)
-import TyVar ( unionTyVarSets, GenTyVar )
-import TysPrim ( intPrimTy )
-import TysWiredIn ( intDataCon, integerTy )
-import Unique ( showUnique, fromRationalClassOpKey, rationalTyConKey,
- fromIntClassOpKey, fromIntegerClassOpKey, Unique
+import Subst ( emptyInScopeSet, mkSubst,
+ substTy, substClasses, mkTyVarSubst, mkTopTyVarSubst
)
-import Util ( panic, zipEqual, zipWithEqual, assoc, assertPanic, pprTrace{-ToDo:rm-} )
+import Literal ( inIntRange )
+import VarEnv ( TidyEnv, lookupSubstEnv, SubstResult(..) )
+import VarSet ( elemVarSet, emptyVarSet, unionVarSet )
+import TysWiredIn ( isIntTy,
+ floatDataCon, isFloatTy,
+ doubleDataCon, isDoubleTy,
+ isIntegerTy
+ )
+import PrelNames( fromIntegerName, fromRationalName )
+import Util ( thenCmp, zipWithEqual, mapAccumL )
+import Bag
+import Outputable
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-type LIE s = Bag (Inst s)
+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
+lieToList = bagToList
+listToLIE = listToBag
-zonkLIE :: LIE s -> NF_TcM s (LIE s)
+zonkLIE :: LIE -> NF_TcM LIE
zonkLIE lie = mapBagNF_Tc zonkInst lie
+
+pprInsts :: [Inst] -> SDoc
+pprInsts insts = parens (sep (punctuate comma (map pprInst insts)))
+
+
+pprInstsInFull insts
+ = vcat (map go insts)
+ where
+ go inst = quotes (ppr inst) <+> pprInstLoc (instLoc inst)
\end{code}
%************************************************************************
Method 34 doubleId [Int] origin
\begin{code}
-data Inst s
+data Inst
= 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
+ Id
+ TcPredType
+ InstLoc
| Method
- Unique
+ Id
- (TcIdOcc s) -- The overloaded function
+ 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 s] -- The types to which its polymorphic tyvars
+ [TcType] -- 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
+ TcThetaType -- The (types of the) dictionaries to which the function
+ -- must be applied to get the method
+
+ TcTauType -- The type of the method
+
+ InstLoc
- (InstOrigin s)
- SrcLoc
+ -- INVARIANT: in (Method u f tys theta tau loc)
+ -- type of (f tys dicts(from theta)) = tau
| 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
+ Id
+ HsOverLit -- The literal from the occurrence site
+ TcType -- The type at which the literal is used
+ InstLoc
\end{code}
-Construction
-~~~~~~~~~~~~
+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.
\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 "newDicts" mk_dict new_uniqs theta
- in
- returnNF_Tc (listToBag dicts, map instToId dicts)
+instance Ord Inst where
+ compare = cmpInst
-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 "newDictsAtLoc" 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
- (if length tyvars /= length tys then pprTrace "newMethod" (ppr PprDebug (idType id)) else \x->x) $
- tcInstType (zip{-Equal "newMethod"-} tyvars tys) rho
- TcId id -> let (tyvars, rho) = splitForAllTy (idType id)
- in returnNF_Tc (instantiateTy (zipEqual "newMethod(2)" tyvars 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 (zipEqual "newMethodAtLoc" tyvars 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}
+instance Eq Inst where
+ (==) i1 i2 = case i1 `cmpInst` i2 of
+ EQ -> True
+ other -> False
+cmpInst (Dict _ pred1 _) (Dict _ pred2 _) = (pred1 `compare` pred2)
+cmpInst (Dict _ _ _) other = LT
-\begin{code}
-instToId :: Inst s -> TcIdOcc s
-instToId (Dict u clas ty orig loc)
- = TcId (mkInstId u (mkDictTy clas ty) (mkLocalName u str False{-emph name-} loc))
- where
- str = SLIT("d.") _APPEND_ (getLocalName clas)
-instToId (Method u id tys rho_ty orig loc)
- = TcId (mkInstId u tau_ty (mkLocalName u str False{-emph name-} loc))
- where
- (_, tau_ty) = splitRhoTy rho_ty -- NB The method Id has just the tau type
- str = SLIT("m.") _APPEND_ (getLocalName id)
+cmpInst (Method _ _ _ _ _ _) (Dict _ _ _) = GT
+cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) = (id1 `compare` id2) `thenCmp` (tys1 `compare` tys2)
+cmpInst (Method _ _ _ _ _ _) other = LT
-instToId (LitInst u list ty orig loc)
- = TcId (mkInstId u ty (mkLocalName u SLIT("lit") True{-emph uniq-} loc))
-\end{code}
+cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `compare` lit2) `thenCmp` (ty1 `compare` ty2)
+cmpInst (LitInst _ _ _ _) other = GT
-\begin{code}
-instType :: Inst s -> TcType s
-instType (Dict _ clas ty _ _) = mkDictTy clas ty
-instType (LitInst _ _ ty _ _) = ty
-instType (Method _ id tys ty _ _) = ty
+-- and they can only have HsInt or HsFracs in them.
\end{code}
-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.
-
+Selection
+~~~~~~~~~
\begin{code}
-zonkInst :: Inst s -> NF_TcM s (Inst s)
-zonkInst (Dict u clas ty orig loc)
- = zonkTcType ty `thenNF_Tc` \ new_ty ->
- returnNF_Tc (Dict u clas new_ty orig loc)
+instToId :: Inst -> TcId
+instToId (Dict id _ _) = id
+instToId (Method id _ _ _ _ _) = id
+instToId (LitInst id _ _ _) = id
-zonkInst (Method u 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 u id new_tys new_rho orig loc)
+instLoc (Dict _ _ loc) = loc
+instLoc (Method _ _ _ _ _ loc) = loc
+instLoc (LitInst _ _ _ loc) = loc
-zonkInst (LitInst u lit ty orig loc)
- = zonkTcType ty `thenNF_Tc` \ new_ty ->
- returnNF_Tc (LitInst u lit new_ty orig loc)
-\end{code}
+getDictClassTys (Dict _ (Class clas tys) _) = (clas, tys)
+predsOfInsts :: [Inst] -> [PredType]
+predsOfInsts insts = concatMap predsOfInst insts
-\begin{code}
-tyVarsOfInst :: Inst s -> TcTyVarSet s
-tyVarsOfInst (Dict _ _ ty _ _) = tyVarsOfType ty
-tyVarsOfInst (Method _ id tys rho _ _) = tyVarsOfTypes tys `unionTyVarSets` tcIdTyVars id
- -- The id might not be a RealId; in the case of
- -- locally-overloaded class methods, for example
-tyVarsOfInst (LitInst _ _ ty _ _) = tyVarsOfType ty
-\end{code}
-
-@matchesInst@ checks when two @Inst@s are instances of the same
-thing at the same type, even if their uniques differ.
+predsOfInst (Dict _ pred _) = [pred]
+predsOfInst (Method _ _ _ theta _ _) = theta
+predsOfInst (LitInst _ _ _ _) = []
+ -- The last case is is really a big cheat
+ -- LitInsts to give rise to a (Num a) or (Fractional a) predicate
+ -- But Num and Fractional have only one parameter and no functional
+ -- dependencies, so I think no caller of predsOfInst will care.
-\begin{code}
-matchesInst :: Inst s -> Inst s -> Bool
+ipsOfPreds theta = [(n,ty) | IParam n ty <- theta]
-matchesInst (Dict _ clas1 ty1 _ _) (Dict _ clas2 ty2 _ _)
- = clas1 == clas2 && ty1 `eqSimpleTy` ty2
+getIPs inst = ipsOfPreds (predsOfInst inst)
-matchesInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _)
- = id1 == id2
- && and (zipWith eqSimpleTy tys1 tys2)
- && length tys1 == length tys2
-
-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
+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
-matchesInst other1 other2 = False
+tyVarsOfInsts insts = foldr (unionVarSet . tyVarsOfInst) emptyVarSet insts
+tyVarsOfLIE lie = tyVarsOfInsts (lieToList lie)
\end{code}
-
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
+isDict :: Inst -> Bool
+isDict (Dict _ _ _) = True
+isDict other = False
+
+isClassDict :: Inst -> Bool
+isClassDict (Dict _ (Class _ _) _) = True
+isClassDict 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
+
+instMentionsIPs :: Inst -> NameSet -> Bool
+ -- True if the Inst mentions any of the implicit
+ -- parameters in the supplied set of names
+instMentionsIPs (Dict _ pred _) ip_names = pred `predMentionsIPs` ip_names
+instMentionsIPs (Method _ _ _ theta _ _) ip_names = any (`predMentionsIPs` ip_names) theta
+instMentionsIPs other ip_names = False
+
+isTyVarDict :: Inst -> Bool
+isTyVarDict (Dict _ (Class _ tys) _) = all isTyVarTy tys
+isTyVarDict other = False
+
+isStdClassTyVarDict (Dict _ (Class clas [ty]) _)
+ = isStandardClass clas && isTyVarTy ty
+isStdClassTyVarDict 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 (Dict _ clas _ _ _) = not (isNoDictClass clas)
-instBindingRequired other = True
-
-instCanBeGeneralised :: Inst s -> Bool
-instCanBeGeneralised (Dict _ clas _ _ _) = not (isCcallishClass clas)
-instCanBeGeneralised other = True
+instBindingRequired :: Inst -> Bool
+instBindingRequired (Dict _ (Class clas _) _) = not (isNoDictClass clas)
+instBindingRequired (Dict _ (IParam _ _) _) = False
+instBindingRequired other = True
+
+instCanBeGeneralised :: Inst -> Bool
+instCanBeGeneralised (Dict _ (Class 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 inst = ppr_inst sty ppNil (\ o l -> ppNil) inst
-
-pprInst sty hdr inst = ppr_inst sty hdr (\ o l -> pprOrigin hdr o l sty) inst
-
-ppr_inst sty hdr ppr_orig (LitInst u lit ty orig loc)
- = ppHang (ppr_orig orig loc)
- 4 (ppCat [case lit of
- OverloadedIntegral i -> ppInteger i
- OverloadedFractional f -> ppRational f,
- ppStr "at",
- ppr sty ty,
- show_uniq sty u])
-
-ppr_inst sty hdr ppr_orig (Dict u clas ty orig loc)
- = ppHang (ppr_orig orig loc)
- 4 (ppCat [ppr sty clas, ppr sty ty, show_uniq sty u])
-
-ppr_inst sty hdr ppr_orig (Method u id tys rho orig loc)
- = ppHang (ppr_orig orig loc)
- 4 (ppCat [ppr sty id, ppStr "at", interppSP sty tys, show_uniq sty u])
-
-show_uniq PprDebug u = ppr PprDebug u
-show_uniq sty u = ppNil
-\end{code}
+newDicts :: InstOrigin
+ -> TcThetaType
+ -> NF_TcM [Inst]
+newDicts orig theta
+ = tcGetInstLoc orig `thenNF_Tc` \ loc ->
+ newDictsAtLoc loc theta
+
+newClassDicts :: InstOrigin
+ -> TcClassContext
+ -> NF_TcM [Inst]
+newClassDicts orig theta = newDicts orig (map (uncurry Class) theta)
+
+newDictsFromOld :: Inst -> TcClassContext -> NF_TcM [Inst]
+newDictsFromOld (Dict _ _ loc) theta = newDictsAtLoc loc (map (uncurry Class) theta)
+
+-- Local function, similar to newDicts,
+-- but with slightly different interface
+newDictsAtLoc :: InstLoc
+ -> TcThetaType
+ -> NF_TcM [Inst]
+newDictsAtLoc inst_loc@(_,loc,_) theta
+ = tcGetUniques (length theta) `thenNF_Tc` \ new_uniqs ->
+ returnNF_Tc (zipWithEqual "newDictsAtLoc" mk_dict new_uniqs theta)
+ where
+ mk_dict uniq pred = Dict (mkLocalId (mk_dict_name uniq pred) (mkPredTy pred)) pred inst_loc
-Printing in error messages
+ mk_dict_name uniq (Class cls tys) = mkLocalName uniq (mkDictOcc (getOccName cls)) loc
+ mk_dict_name uniq (IParam name ty) = name
-\begin{code}
-noInstanceErr inst sty = ppHang (ppPStr SLIT("No instance for:")) 4 (ppr sty inst)
+newIPDict orig name ty
+ = tcGetInstLoc orig `thenNF_Tc` \ inst_loc ->
+ returnNF_Tc (Dict (mkLocalId name ty) (IParam name ty) inst_loc)
\end{code}
+
%************************************************************************
%* *
-\subsection[InstEnv-types]{Type declarations}
+\subsection{Building methods (calls of overloaded functions)}
%* *
%************************************************************************
-\begin{code}
-type InstanceMapper = Class -> (ClassInstEnv, ClassOp -> SpecEnv)
-\end{code}
+tcInstId instantiates an occurrence of an Id.
+The instantiate_it loop runs round instantiating the Id.
+It has to be a loop because we are now prepared to entertain
+types like
+ f:: forall a. Eq a => forall b. Baz b => tau
+We want to instantiate this to
+ f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
+
+The -fno-method-sharing flag controls what happens so far as the LIE
+is concerned. The default case is that for an overloaded function we
+generate a "method" Id, and add the Method Inst to the LIE. So you get
+something like
+ f :: Num a => a -> a
+ f = /\a (d:Num a) -> let m = (+) a d in \ (x:a) -> m x x
+If you specify -fno-method-sharing, the dictionary application
+isn't shared, so we get
+ f :: Num a => a -> a
+ f = /\a (d:Num a) (x:a) -> (+) a d x x
+This gets a bit less sharing, but
+ a) it's better for RULEs involving overloaded functions
+ b) perhaps fewer separated lambdas
-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}
-lookupInst :: Inst s
- -> TcM s ([Inst s],
- (TcIdOcc s, TcExpr s)) -- The new binding
-
--- Dictionaries
+tcInstId :: Id -> NF_TcM (TcExpr, LIE, TcType)
+tcInstId fun
+ | opt_NoMethodSharing = loop_noshare (HsVar fun) (idType fun)
+ | otherwise = loop_share fun
+ where
+ orig = OccurrenceOf fun
+ loop_noshare fun fun_ty
+ = tcInstType fun_ty `thenNF_Tc` \ (tyvars, theta, tau) ->
+ let
+ ty_app = mkHsTyApp fun (mkTyVarTys tyvars)
+ in
+ if null theta then -- Is it overloaded?
+ returnNF_Tc (ty_app, emptyLIE, tau)
+ else
+ newDicts orig theta `thenNF_Tc` \ dicts ->
+ loop_noshare (mkHsDictApp ty_app (map instToId dicts)) tau `thenNF_Tc` \ (expr, lie, final_tau) ->
+ returnNF_Tc (expr, mkLIE dicts `plusLIE` lie, final_tau)
+
+ loop_share fun
+ = tcInstType (idType fun) `thenNF_Tc` \ (tyvars, theta, tau) ->
+ let
+ arg_tys = mkTyVarTys tyvars
+ in
+ if null theta then -- Is it overloaded?
+ returnNF_Tc (mkHsTyApp (HsVar fun) arg_tys, emptyLIE, tau)
+ else
+ -- Yes, it's overloaded
+ newMethodWithGivenTy orig fun arg_tys theta tau `thenNF_Tc` \ meth ->
+ loop_share (instToId meth) `thenNF_Tc` \ (expr, lie, final_tau) ->
+ returnNF_Tc (expr, unitLIE meth `plusLIE` lie, final_tau)
+
+
+newMethod :: InstOrigin
+ -> TcId
+ -> [TcType]
+ -> NF_TcM Inst
+newMethod orig id tys
+ = -- Get the Id type and instantiate it at the specified types
+ let
+ (tyvars, rho) = splitForAllTys (idType id)
+ rho_ty = substTy (mkTyVarSubst tyvars tys) rho
+ (pred, tau) = splitMethodTy rho_ty
+ in
+ newMethodWithGivenTy orig id tys [pred] tau
-lookupInst dict@(Dict _ clas ty orig loc)
- = case lookupMEnv matchTy (get_inst_env clas orig) ty of
- Nothing -> tcAddSrcLoc loc $
- tcAddErrCtxt (pprOrigin ""{-hdr-} orig loc) $
- failTc (noInstanceErr dict)
+newMethodWithGivenTy orig id tys theta tau
+ = tcGetInstLoc orig `thenNF_Tc` \ loc ->
+ newMethodWith loc id tys theta tau
- 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))
-
+newMethodWith inst_loc@(_,loc,_) id tys theta tau
+ = tcGetUnique `thenNF_Tc` \ new_uniq ->
+ let
+ meth_id = mkUserLocal (mkMethodOcc (getOccName id)) new_uniq tau loc
+ in
+ returnNF_Tc (Method meth_id id tys theta tau inst_loc)
--- Methods
+newMethodAtLoc :: InstLoc
+ -> Id -> [TcType]
+ -> NF_TcM (Inst, TcId)
+newMethodAtLoc inst_loc real_id tys
+ -- This actually builds the Inst
+ = -- Get the Id type and instantiate it at the specified types
+ let
+ (tyvars,rho) = splitForAllTys (idType real_id)
+ rho_ty = ASSERT( length tyvars == length tys )
+ substTy (mkTopTyVarSubst tyvars tys) rho
+ (theta, tau) = splitRhoTy rho_ty
+ in
+ newMethodWith inst_loc real_id tys theta tau `thenNF_Tc` \ meth_inst ->
+ returnNF_Tc (meth_inst, instToId meth_inst)
+\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
+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).
--- Literals
+\begin{code}
+newOverloadedLit :: InstOrigin
+ -> HsOverLit
+ -> TcType
+ -> NF_TcM (TcExpr, LIE)
+newOverloadedLit orig (HsIntegral i) ty
+ | isIntTy ty && inIntRange i -- Short cut for Int
+ = returnNF_Tc (int_lit, emptyLIE)
-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))
+ | isIntegerTy ty -- Short cut for Integer
+ = returnNF_Tc (integer_lit, emptyLIE)
- | 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) integerTy)))
where
- intprim_lit = HsLitOut (HsIntPrim i) intPrimTy
- int_lit = HsApp (HsVar (RealId intDataCon)) intprim_lit
+ int_lit = HsLit (HsInt i)
+ integer_lit = HsLit (HsInteger i)
-lookupInst inst@(LitInst u (OverloadedFractional f) ty orig loc)
- = tcLookupGlobalValueByKey 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 ->
+newOverloadedLit orig lit ty -- The general case
+ = tcGetInstLoc orig `thenNF_Tc` \ loc ->
+ tcGetUnique `thenNF_Tc` \ new_uniq ->
let
- rational_ty = mkSynTy rational_tycon []
- rational_lit = HsLitOut (HsFrac f) rational_ty
+ lit_inst = LitInst lit_id lit ty loc
+ lit_id = mkSysLocal SLIT("lit") new_uniq ty
in
- newMethodAtLoc orig loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) ->
- returnTc ([method_inst], (instToId inst, HsApp (HsVar method_id) rational_lit))
+ returnNF_Tc (HsVar (instToId lit_inst), unitLIE lit_inst)
\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.
+
+%************************************************************************
+%* *
+\subsection{Zonking}
+%* *
+%************************************************************************
+
+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.
\begin{code}
-lookupSimpleInst :: ClassInstEnv
- -> Class
- -> Type -- Look up (c,t)
- -> TcM s [(Class,Type)] -- Here are the needed (c,t)s
-
-lookupSimpleInst class_inst_env clas ty
- = case (lookupMEnv matchTy class_inst_env ty) of
- Nothing -> failTc (noSimpleInst clas ty)
- Just (dfun,tenv) -> returnTc [(c,instantiateTy tenv t) | (c,t) <- theta]
- where
- (_, theta, _) = splitSigmaTy (idType dfun)
-
-noSimpleInst clas ty sty
- = ppSep [ppStr "No instance for class", ppQuote (ppr sty clas),
- ppStr "at type", ppQuote (ppr sty ty)]
+zonkPred :: TcPredType -> NF_TcM TcPredType
+zonkPred (Class clas tys)
+ = zonkTcTypes tys `thenNF_Tc` \ new_tys ->
+ returnNF_Tc (Class clas new_tys)
+zonkPred (IParam n ty)
+ = zonkTcType ty `thenNF_Tc` \ new_ty ->
+ returnNF_Tc (IParam n new_ty)
+
+zonkInst :: Inst -> NF_TcM Inst
+zonkInst (Dict id pred loc)
+ = zonkPred pred `thenNF_Tc` \ new_pred ->
+ returnNF_Tc (Dict id new_pred loc)
+
+zonkInst (Method m id tys theta tau loc)
+ = zonkId id `thenNF_Tc` \ 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 m new_id new_tys new_theta new_tau loc)
+
+zonkInst (LitInst id lit ty loc)
+ = zonkTcType ty `thenNF_Tc` \ new_ty ->
+ returnNF_Tc (LitInst id lit new_ty loc)
+
+zonkInsts insts = mapNF_Tc zonkInst insts
\end{code}
-@mkInstSpecEnv@ is used to construct the @SpecEnv@ for a dfun.
-It does it by filtering the class's @InstEnv@. All pretty shady stuff.
+%************************************************************************
+%* *
+\subsection{Printing}
+%* *
+%************************************************************************
+
+ToDo: improve these pretty-printing things. The ``origin'' is really only
+relevant in error messages.
\begin{code}
-mkInstSpecEnv clas inst_ty inst_tvs inst_theta = panic "mkInstSpecEnv"
-\end{code}
+instance Outputable Inst where
+ ppr inst = pprInst 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
-\begin{pseudocode}
-mkInstSpecEnv :: Class -- class
- -> Type -- instance type
- -> [TyVarTemplate] -- instance tyvars
- -> ThetaType -- superclasses dicts
- -> SpecEnv -- specenv for dfun of instance
+pprInst m@(Method u id tys theta tau loc)
+ = hsep [ppr id, ptext SLIT("at"),
+ brackets (interppSP tys) {- ,
+ ptext SLIT("theta"), ppr theta,
+ ptext SLIT("tau"), ppr tau
+ show_uniq u,
+ ppr (instToId m) -}]
-mkInstSpecEnv clas inst_ty inst_tvs inst_theta
- = mkSpecEnv (catMaybes (map maybe_spec_info matches))
+tidyPred :: TidyEnv -> TcPredType -> (TidyEnv, TcPredType)
+tidyPred env (Class clas tys)
+ = (env', Class clas tys')
where
- matches = matchMEnv matchTy (classInstEnv clas) inst_ty
+ (env', tys') = tidyOpenTypes env tys
+tidyPred env (IParam n ty)
+ = (env', IParam n ty')
+ where
+ (env', ty') = tidyOpenType env ty
- 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}
+tidyInst :: TidyEnv -> Inst -> (TidyEnv, Inst)
+tidyInst env (LitInst u lit ty loc)
+ = (env', LitInst u lit ty' loc)
+ where
+ (env', ty') = tidyOpenType env ty
+tidyInst env (Dict u pred loc)
+ = (env', Dict u pred' loc)
+ where
+ (env', pred') = tidyPred env pred
-\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
-\end{code}
+tidyInst env (Method u id tys theta tau loc)
+ = (env', Method u id tys' theta tau loc)
+ -- Leave theta, tau alone cos we don't print them
+ where
+ (env', tys') = tidyOpenTypes env tys
+
+tidyInsts env insts = mapAccumL tidyInst env insts
+show_uniq u = ifPprDebug (text "{-" <> ppr u <> text "-}")
+\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
-
- | RecordUpdOrigin
+data LookupInstResult s
+ = NoInstance
+ | SimpleInst TcExpr -- Just a variable, type application, or literal
+ | GenInst [Inst] TcExpr -- The expression and its needed insts
- | DataDeclOrigin -- Typechecking a data declaration
+lookupInst :: Inst
+ -> NF_TcM (LookupInstResult s)
- | InstanceDeclOrigin -- Typechecking an instance decl
-
- | LiteralOrigin HsLit -- Occurrence of a literal
+-- Dictionaries
- | ArithSeqOrigin RenamedArithSeqInfo -- [x..], [x..y] etc
+lookupInst dict@(Dict _ (Class clas tys) loc)
+ = tcGetInstEnv `thenNF_Tc` \ inst_env ->
+ case lookupInstEnv inst_env clas tys of
- | SignatureOrigin -- A dict created from a type signature
+ FoundInst tenv dfun_id
+ -> let
+ (tyvars, rho) = splitForAllTys (idType dfun_id)
+ mk_ty_arg tv = case lookupSubstEnv tenv tv of
+ Just (DoneTy ty) -> returnNF_Tc ty
+ Nothing -> tcInstTyVar tv `thenNF_Tc` \ tc_tv ->
+ returnTc (mkTyVarTy tc_tv)
+ in
+ mapNF_Tc mk_ty_arg tyvars `thenNF_Tc` \ ty_args ->
+ let
+ subst = mkTyVarSubst tyvars ty_args
+ dfun_rho = substTy subst rho
+ (theta, _) = splitRhoTy dfun_rho
+ ty_app = mkHsTyApp (HsVar dfun_id) ty_args
+ in
+ if null theta then
+ returnNF_Tc (SimpleInst ty_app)
+ else
+ newDictsAtLoc loc theta `thenNF_Tc` \ dicts ->
+ let
+ rhs = mkHsDictApp ty_app (map instToId dicts)
+ in
+ returnNF_Tc (GenInst dicts rhs)
- | DoOrigin -- The monad for a do expression
+ other -> returnNF_Tc NoInstance
- | ClassDeclOrigin -- Manufactured during a class decl
+lookupInst dict@(Dict _ _ loc) = returnNF_Tc NoInstance
--- NO MORE!
--- | DerivingOrigin InstanceMapper
--- Class
--- TyCon
+-- Methods
- -- 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].)
+lookupInst inst@(Method _ id tys theta _ loc)
+ = newDictsAtLoc loc theta `thenNF_Tc` \ dicts ->
+ returnNF_Tc (GenInst dicts (mkHsDictApp (mkHsTyApp (HsVar id) tys) (map instToId dicts)))
- | InstanceSpecOrigin InstanceMapper
- Class -- in a SPECIALIZE instance pragma
- Type
+-- Literals
- -- 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].)
+lookupInst inst@(LitInst u (HsIntegral i) ty 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
--- | DefaultDeclOrigin -- Related to a `default' declaration
+ | isIntegerTy ty -- Short cut for Integer
+ = returnNF_Tc (GenInst [] integer_lit)
- | ValSpecOrigin Name -- in a SPECIALIZE pragma for a value
+ | otherwise -- Alas, it is overloaded and a big literal!
+ = tcLookupSyntaxId fromIntegerName `thenNF_Tc` \ from_integer ->
+ newMethodAtLoc 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
+ integer_lit = HsLit (HsInteger i)
+ int_lit = HsLit (HsInt i)
- -- 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.
+-- similar idea for overloaded floating point literals: if the literal is
+-- *definitely* a float or a double, generate the real thing here.
+-- This is essential (see nofib/spectral/nucleic).
- | CCallOrigin String -- CCall label
- (Maybe RenamedHsExpr) -- Nothing if it's the result
- -- Just arg, for an argument
+lookupInst inst@(LitInst u (HsFractional f) ty loc)
+ | isFloatTy ty = returnNF_Tc (GenInst [] float_lit)
+ | isDoubleTy ty = returnNF_Tc (GenInst [] double_lit)
- | LitLitOrigin String -- the litlit
+ | otherwise
+ = tcLookupSyntaxId fromRationalName `thenNF_Tc` \ from_rational ->
+ newMethodAtLoc loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) ->
+ let
+ rational_ty = funArgTy (idType method_id)
+ rational_lit = HsLit (HsRat f rational_ty)
+ in
+ returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) rational_lit))
- | UnknownOrigin -- Help! I give up...
+ where
+ floatprim_lit = HsLit (HsFloatPrim f)
+ float_lit = mkHsConApp floatDataCon [] [floatprim_lit]
+ doubleprim_lit = HsLit (HsDoublePrim f)
+ double_lit = mkHsConApp 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}
--- 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 = classInstEnv clas
-
-
-pprOrigin :: String -> InstOrigin s -> SrcLoc -> Error
-
-pprOrigin hdr orig locn
- = addErrLoc locn hdr $ \ sty ->
- case orig of
- OccurrenceOf id ->
- ppBesides [ppPStr SLIT("at a use of an overloaded identifier: `"),
- ppr sty id, ppChar '\'']
- OccurrenceOfCon id ->
- ppBesides [ppPStr SLIT("at a use of an overloaded constructor: `"),
- ppr sty id, ppChar '\'']
- InstanceDeclOrigin ->
- ppStr "in an instance declaration"
- LiteralOrigin lit ->
- ppCat [ppStr "at an overloaded literal:", ppr sty lit]
- ArithSeqOrigin seq ->
- ppCat [ppStr "at an arithmetic sequence:", ppr sty seq]
- SignatureOrigin ->
- ppStr "in a type signature"
- DoOrigin ->
- ppStr "in a do statement"
- ClassDeclOrigin ->
- ppStr "in a class declaration"
- InstanceSpecOrigin _ clas ty ->
- ppBesides [ppStr "in a SPECIALIZE instance pragma; class \"",
- ppr sty clas, ppStr "\" type: ", ppr sty ty]
- ValSpecOrigin name ->
- ppBesides [ppStr "in a SPECIALIZE user-pragma for `",
- ppr sty name, ppStr "'"]
- CCallOrigin clabel Nothing{-ccall result-} ->
- ppBesides [ppStr "in the result of the _ccall_ to `",
- ppStr clabel, ppStr "'"]
- CCallOrigin clabel (Just arg_expr) ->
- ppBesides [ppStr "in an argument in the _ccall_ to `",
- ppStr clabel, ppStr "', namely: ", ppr sty arg_expr]
- LitLitOrigin s ->
- ppBesides [ppStr "in this ``literal-literal'': ", ppStr s]
- UnknownOrigin ->
- ppStr "in... oops -- I don't know where the overloading came from!"
+lookupSimpleInst :: Class
+ -> [Type] -- Look up (c,t)
+ -> NF_TcM (Maybe [(Class,[Type])]) -- Here are the needed (c,t)s
+
+lookupSimpleInst clas tys
+ = tcGetInstEnv `thenNF_Tc` \ inst_env ->
+ case lookupInstEnv inst_env clas tys of
+ FoundInst tenv dfun
+ -> returnNF_Tc (Just (substClasses (mkSubst emptyInScopeSet tenv) theta'))
+ where
+ (_, theta, _) = splitSigmaTy (idType dfun)
+ theta' = classesOfPreds theta
+
+ other -> returnNF_Tc Nothing
\end{code}
+
+
projects / ghc-hetmet.git / blobdiff