\begin{code}
module Inst (
- LIE, emptyLIE, unitLIE, plusLIE, consLIE, zonkLIE,
- plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
+ Inst,
- Inst, OverloadedLit(..),
- pprInst, pprInsts, pprInstsInFull, tidyInst, tidyInsts,
+ pprDFuns, pprDictsTheta, pprDictsInFull, -- User error messages
+ showLIE, pprInst, pprInsts, pprInstInFull, -- Debugging messages
- InstanceMapper,
+ tidyInsts, tidyMoreInsts,
- newDictFromOld, newDicts, newClassDicts, newDictsAtLoc,
- newMethod, newMethodWithGivenTy, newOverloadedLit,
- newIPDict, instOverloadedFun,
- instantiateFdClassTys, instFunDeps, instFunDepsOfTheta,
- newFunDepFromDict,
+ newDicts, newDictAtLoc, newDictsAtLoc, cloneDict,
+ newOverloadedLit, newIPDict,
+ newMethod, newMethodFromName, newMethodWithGivenTy,
+ tcInstClassOp, tcInstCall, tcInstStupidTheta,
+ tcSyntaxName, tcStdSyntaxName,
- tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE, instLoc, getDictClassTys,
- getDictPred_maybe, getMethodTheta_maybe,
- getFunDeps, getFunDepsOfLIE,
- getIPs, getIPsOfLIE,
- getAllFunDeps, getAllFunDepsOfLIE,
+ tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE,
+ ipNamesOfInst, ipNamesOfInsts, fdPredsOfInst, fdPredsOfInsts,
+ instLoc, getDictClassTys, dictPred,
- lookupInst, lookupSimpleInst, LookupInstResult(..),
+ lookupInst, LookupInstResult(..), lookupPred,
+ tcExtendLocalInstEnv, tcGetInstEnvs,
- isDict, isClassDict, isMethod,
- isTyVarDict, isStdClassTyVarDict, isMethodFor, notFunDep,
- instBindingRequired, instCanBeGeneralised,
+ isDict, isClassDict, isMethod,
+ isLinearInst, linearInstType, isIPDict, isInheritableInst,
+ isTyVarDict, isStdClassTyVarDict, isMethodFor,
+ instBindingRequired,
- zonkInst, zonkInsts, zonkFunDeps, zonkTvFunDeps,
- instToId, instToIdBndr, ipToId,
+ zonkInst, zonkInsts,
+ instToId, instName,
- InstOrigin(..), InstLoc, pprInstLoc
+ InstOrigin(..), InstLoc(..), pprInstLoc
) where
#include "HsVersions.h"
-import HsSyn ( HsLit(..), HsExpr(..) )
-import RnHsSyn ( RenamedArithSeqInfo, RenamedHsExpr, RenamedPat )
-import TcHsSyn ( TcExpr, TcId,
- mkHsTyApp, mkHsDictApp, mkHsConApp, zonkId
- )
-import TcMonad
-import TcEnv ( TcIdSet, tcLookupValueByKey, tcLookupTyConByKey )
-import TcType ( TcThetaType,
- TcType, TcTauType, TcTyVarSet,
- zonkTcTyVars, zonkTcType, zonkTcTypes,
- zonkTcThetaType
+import {-# SOURCE #-} TcExpr( tcCheckSigma )
+import {-# SOURCE #-} TcUnify ( unifyTauTy ) -- Used in checkKind (sigh)
+
+import HsSyn ( HsLit(..), HsOverLit(..), HsExpr(..), LHsExpr, mkHsApp )
+import TcHsSyn ( TcId, TcIdSet,
+ mkHsTyApp, mkHsDictApp, mkHsConApp, zonkId,
+ mkCoercion, ExprCoFn
)
-import Bag
-import Class ( classInstEnv, Class, FunDep )
-import FunDeps ( instantiateFdClassTys )
-import Id ( Id, idFreeTyVars, idType, mkUserLocal, mkSysLocal )
-import PrelInfo ( isStandardClass, isCcallishClass, isNoDictClass )
-import Name ( OccName, Name, mkDictOcc, mkMethodOcc, mkIPOcc,
- getOccName, nameUnique )
-import PprType ( pprPred )
-import InstEnv ( InstEnv, lookupInstEnv, InstEnvResult(..) )
-import SrcLoc ( SrcLoc )
-import Type ( Type, PredType(..), ThetaType,
- mkTyVarTy, isTyVarTy, mkDictTy, mkPredTy,
- splitForAllTys, splitSigmaTy,
- splitRhoTy, tyVarsOfType, tyVarsOfTypes, tyVarsOfPred,
- mkSynTy, tidyOpenType, tidyOpenTypes
+import TcRnMonad
+import TcEnv ( tcLookupId, checkWellStaged, topIdLvl, tcMetaTy )
+import InstEnv ( DFunId, InstEnv, lookupInstEnv, checkFunDeps, extendInstEnv )
+import TcIface ( loadImportedInsts )
+import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType, zonkTcThetaType,
+ tcInstTyVar, tcInstType, tcSkolType
)
-import InstEnv ( InstEnv )
-import Subst ( emptyInScopeSet, mkSubst,
- substTy, substClasses, mkTyVarSubst, mkTopTyVarSubst
+import TcType ( Type, TcType, TcThetaType, TcTyVarSet, TcTyVar, TcPredType,
+ PredType(..), SkolemInfo(..), typeKind, mkSigmaTy,
+ tcSplitForAllTys, tcSplitForAllTys,
+ tcSplitPhiTy, tcIsTyVarTy, tcSplitDFunTy, tcSplitDFunHead,
+ 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,
+ pprPred, pprParendType, pprThetaArrow, pprTheta, pprClassPred
)
-import TyCon ( TyCon )
+import Type ( TvSubst, substTy, substTyVar, substTyWith, substTheta, zipTopTvSubst,
+ notElemTvSubst, extendTvSubstList )
+import Unify ( tcMatchTys )
+import Kind ( isSubKind )
+import Packages ( isHomeModule )
+import HscTypes ( ExternalPackageState(..) )
+import CoreFVs ( idFreeTyVars )
+import DataCon ( DataCon, dataConTyVars, dataConStupidTheta, dataConName )
+import Id ( Id, idName, idType, mkUserLocal, mkLocalId )
+import PrelInfo ( isStandardClass, isNoDictClass )
+import Name ( Name, mkMethodOcc, getOccName, getSrcLoc, nameModule,
+ isInternalName, setNameUnique, mkSystemVarNameEncoded )
+import NameSet ( addOneToNameSet )
import Literal ( inIntRange )
-import Var ( TyVar )
-import VarEnv ( lookupVarEnv, TidyEnv,
- lookupSubstEnv, SubstResult(..)
- )
-import VarSet ( elemVarSet, emptyVarSet, unionVarSet )
-import TysPrim ( intPrimTy, floatPrimTy, doublePrimTy )
-import TysWiredIn ( intDataCon, isIntTy,
- floatDataCon, isFloatTy,
- doubleDataCon, isDoubleTy,
- integerTy, isIntegerTy,
- voidTy
- )
-import Unique ( fromRationalClassOpKey, rationalTyConKey,
- fromIntClassOpKey, fromIntegerClassOpKey, Unique
- )
-import Maybes ( expectJust )
-import Maybe ( catMaybes )
-import Util ( thenCmp, zipWithEqual, mapAccumL )
+import Var ( TyVar, tyVarKind, setIdType )
+import VarEnv ( TidyEnv, emptyTidyEnv )
+import VarSet ( elemVarSet, emptyVarSet, unionVarSet, mkVarSet )
+import TysWiredIn ( floatDataCon, doubleDataCon )
+import PrelNames ( integerTyConName, fromIntegerName, fromRationalName, rationalTyConName )
+import BasicTypes( IPName(..), mapIPName, ipNameName )
+import UniqSupply( uniqsFromSupply )
+import SrcLoc ( mkSrcSpan, noLoc, unLoc, Located(..) )
+import CmdLineOpts( DynFlags )
+import Maybes ( isJust )
import Outputable
\end{code}
-%************************************************************************
-%* *
-\subsection[Inst-collections]{LIE: a collection of Insts}
-%* *
-%************************************************************************
-
-\begin{code}
-type LIE = Bag Inst
-
-isEmptyLIE = isEmptyBag
-emptyLIE = emptyBag
-unitLIE inst = unitBag inst
-mkLIE insts = listToBag insts
-plusLIE lie1 lie2 = lie1 `unionBags` lie2
-consLIE inst lie = inst `consBag` lie
-plusLIEs lies = unionManyBags lies
-lieToList = bagToList
-listToLIE = listToBag
-
-zonkLIE :: LIE -> NF_TcM s 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}
-
-%************************************************************************
-%* *
-\subsection[Inst-types]{@Inst@ types}
-%* *
-%************************************************************************
-
-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
-
- Method 34 doubleId [Int] origin
-
-\begin{code}
-data Inst
- = Dict
- Unique
- TcPredType
- InstLoc
-
- | Method
- Unique
-
- TcId -- The overloaded function
- -- This function will be a global, local, or ClassOpId;
- -- inside instance decls (only) it can also be an InstId!
- -- The id needn't be completely polymorphic.
- -- You'll probably find its name (for documentation purposes)
- -- inside the InstOrigin
-
- [TcType] -- The types to which its polymorphic tyvars
- -- should be instantiated.
- -- These types must saturate the Id's foralls.
-
- TcThetaType -- The (types of the) dictionaries to which the function
- -- must be applied to get the method
-
- TcTauType -- The type of the method
-
- InstLoc
-
- -- INVARIANT: in (Method u f tys theta tau loc)
- -- type of (f tys dicts(from theta)) = tau
-
- | LitInst
- Unique
- OverloadedLit
- TcType -- The type at which the literal is used
- InstLoc
-
- | FunDep
- Unique
- Class -- the class from which this arises
- [FunDep TcType]
- InstLoc
-
-data OverloadedLit
- = OverloadedIntegral Integer -- The number
- | OverloadedFractional Rational -- The number
-\end{code}
-
-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}
-instance Ord Inst where
- compare = cmpInst
-
-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
-
-cmpInst (Method _ _ _ _ _ _) (Dict _ _ _) = GT
-cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) = (id1 `compare` id2) `thenCmp` (tys1 `compare` tys2)
-cmpInst (Method _ _ _ _ _ _) other = LT
-
-cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `cmpOverLit` lit2) `thenCmp` (ty1 `compare` ty2)
-cmpInst (LitInst _ _ _ _) (FunDep _ _ _ _) = LT
-cmpInst (LitInst _ _ _ _) other = GT
-
-cmpInst (FunDep _ clas1 fds1 _) (FunDep _ clas2 fds2 _) = (clas1 `compare` clas2) `thenCmp` (fds1 `compare` fds2)
-cmpInst (FunDep _ _ _ _) other = GT
-
-cmpOverLit (OverloadedIntegral i1) (OverloadedIntegral i2) = i1 `compare` i2
-cmpOverLit (OverloadedFractional f1) (OverloadedFractional f2) = f1 `compare` f2
-cmpOverLit (OverloadedIntegral _) (OverloadedFractional _) = LT
-cmpOverLit (OverloadedFractional _) (OverloadedIntegral _) = GT
-\end{code}
-
Selection
~~~~~~~~~
\begin{code}
-instLoc (Dict u pred loc) = loc
-instLoc (Method u _ _ _ _ loc) = loc
-instLoc (LitInst u lit ty loc) = loc
-instLoc (FunDep _ _ _ loc) = loc
+instName :: Inst -> Name
+instName inst = idName (instToId inst)
-getDictPred_maybe (Dict _ p _) = Just p
-getDictPred_maybe _ = Nothing
+instToId :: Inst -> TcId
+instToId (LitInst nm _ ty _) = mkLocalId nm ty
+instToId (Dict nm pred _) = mkLocalId nm (mkPredTy pred)
+instToId (Method id _ _ _ _ _) = id
-getMethodTheta_maybe (Method _ _ _ theta _ _) = Just theta
-getMethodTheta_maybe _ = Nothing
+instLoc (Dict _ _ loc) = loc
+instLoc (Method _ _ _ _ _ loc) = loc
+instLoc (LitInst _ _ _ loc) = loc
-getDictClassTys (Dict u (Class clas tys) _) = (clas, tys)
+dictPred (Dict _ pred _ ) = pred
+dictPred inst = pprPanic "dictPred" (ppr inst)
-getFunDeps (FunDep _ clas fds _) = Just (clas, fds)
-getFunDeps _ = Nothing
+getDictClassTys (Dict _ pred _) = getClassPredTys pred
-getFunDepsOfLIE lie = catMaybes (map getFunDeps (lieToList lie))
+-- 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
-getIPsOfPred (IParam n ty) = [(n, ty)]
-getIPsOfPred _ = []
-getIPsOfTheta theta = concatMap getIPsOfPred theta
+fdPredsOfInsts :: [Inst] -> [PredType]
+fdPredsOfInsts insts = concatMap fdPredsOfInst insts
-getIPs (Dict u (IParam n ty) loc) = [(n, ty)]
-getIPs (Method u id _ theta t loc) = getIPsOfTheta theta
-getIPs _ = []
+isInheritableInst (Dict _ pred _) = isInheritablePred pred
+isInheritableInst (Method _ _ _ theta _ _) = all isInheritablePred theta
+isInheritableInst other = True
-getIPsOfLIE lie = concatMap getIPs (lieToList lie)
-getAllFunDeps (FunDep _ clas fds _) = fds
-getAllFunDeps inst = map (\(n,ty) -> ([], [ty])) (getIPs inst)
+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]
-getAllFunDepsOfLIE lie = concat (map getAllFunDeps (lieToList lie))
+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
-tyVarsOfInst (LitInst _ _ ty _) = tyVarsOfType ty
-tyVarsOfInst (FunDep _ _ fds _)
- = foldr unionVarSet emptyVarSet (map tyVarsOfFd fds)
- where tyVarsOfFd (ts1, ts2) =
- tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2
-tyVarsOfInsts insts
- = foldr unionVarSet emptyVarSet (map tyVarsOfInst insts)
-tyVarsOfLIE lie
- = foldr unionVarSet emptyVarSet (map tyVarsOfInst insts)
- where insts = lieToList lie
+tyVarsOfInsts insts = foldr (unionVarSet . tyVarsOfInst) emptyVarSet insts
+tyVarsOfLIE lie = tyVarsOfInsts (lieToList lie)
\end{code}
Predicates
isDict :: Inst -> Bool
isDict (Dict _ _ _) = True
isDict other = False
+
isClassDict :: Inst -> Bool
-isClassDict (Dict _ (Class _ _) _) = True
-isClassDict other = False
+isClassDict (Dict _ pred _) = isClassPred pred
+isClassDict other = False
+
+isTyVarDict :: Inst -> Bool
+isTyVarDict (Dict _ pred _) = isTyVarClassPred pred
+isTyVarDict other = False
+
+isIPDict :: Inst -> Bool
+isIPDict (Dict _ pred _) = isIPPred pred
+isIPDict other = False
isMethod :: Inst -> Bool
isMethod (Method _ _ _ _ _ _) = True
isMethod other = False
isMethodFor :: TcIdSet -> Inst -> Bool
-isMethodFor ids (Method uniq id tys _ _ loc)
- = id `elemVarSet` ids
-isMethodFor ids inst
- = False
+isMethodFor ids (Method uniq id tys _ _ loc) = id `elemVarSet` ids
+isMethodFor ids inst = False
-isTyVarDict :: Inst -> Bool
-isTyVarDict (Dict _ (Class _ tys) _) = all isTyVarTy tys
-isTyVarDict other = False
+isLinearInst :: Inst -> Bool
+isLinearInst (Dict _ pred _) = isLinearPred pred
+isLinearInst other = False
+ -- We never build Method Insts that have
+ -- linear implicit paramters in them.
+ -- Hence no need to look for Methods
+ -- See TcExpr.tcId
+
+linearInstType :: Inst -> TcType -- %x::t --> t
+linearInstType (Dict _ (IParam _ ty) _) = ty
-isStdClassTyVarDict (Dict _ (Class clas [ty]) _)
- = isStandardClass clas && isTyVarTy ty
-isStdClassTyVarDict other
- = False
-notFunDep :: Inst -> Bool
-notFunDep (FunDep _ _ _ _) = False
-notFunDep other = True
+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
\begin{code}
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
+instBindingRequired (Dict _ (ClassP clas _) _) = not (isNoDictClass clas)
+instBindingRequired other = True
\end{code}
-Construction
-~~~~~~~~~~~~
+%************************************************************************
+%* *
+\subsection{Building dictionaries}
+%* *
+%************************************************************************
\begin{code}
newDicts :: InstOrigin
-> TcThetaType
- -> NF_TcM s (LIE, [TcId])
+ -> TcM [Inst]
newDicts orig theta
- = tcGetInstLoc orig `thenNF_Tc` \ loc ->
- newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, ids) ->
- returnNF_Tc (listToBag dicts, ids)
-
-newClassDicts :: InstOrigin
- -> [(Class,[TcType])]
- -> NF_TcM s (LIE, [TcId])
-newClassDicts orig theta
- = newDicts orig (map (uncurry Class) theta)
-
--- Local function, similar to newDicts,
--- but with slightly different interface
-newDictsAtLoc :: InstLoc
- -> TcThetaType
- -> NF_TcM s ([Inst], [TcId])
-newDictsAtLoc loc theta =
- tcGetUniques (length theta) `thenNF_Tc` \ new_uniqs ->
- let
- mk_dict u pred = Dict u pred loc
- dicts = zipWithEqual "newDictsAtLoc" mk_dict new_uniqs theta
- in
- returnNF_Tc (dicts, map instToId dicts)
-
-newDictFromOld :: Inst -> Class -> [TcType] -> NF_TcM s Inst
-newDictFromOld (Dict _ _ loc) clas tys
- = tcGetUnique `thenNF_Tc` \ uniq ->
- returnNF_Tc (Dict uniq (Class clas tys) loc)
-
-
-newMethod :: InstOrigin
- -> TcId
- -> [TcType]
- -> NF_TcM s (LIE, TcId)
-newMethod orig id tys
- = -- Get the Id type and instantiate it at the specified types
+ = getInstLoc orig `thenM` \ loc ->
+ newDictsAtLoc loc theta
+
+cloneDict :: Inst -> TcM Inst
+cloneDict (Dict nm ty loc) = newUnique `thenM` \ uniq ->
+ returnM (Dict (setNameUnique nm uniq) ty loc)
+
+newDictAtLoc :: InstLoc -> TcPredType -> TcM Inst
+newDictAtLoc inst_loc pred
+ = do { uniq <- newUnique
+ ; return (mkDict inst_loc uniq pred) }
+
+newDictsAtLoc :: InstLoc -> TcThetaType -> TcM [Inst]
+newDictsAtLoc inst_loc theta
+ = newUniqueSupply `thenM` \ us ->
+ returnM (zipWith (mkDict inst_loc) (uniqsFromSupply us) theta)
+
+mkDict inst_loc uniq pred
+ = Dict name pred inst_loc
+ where
+ name = mkPredName uniq (instLocSrcLoc inst_loc) pred
+
+-- 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 ->
+ newUnique `thenM` \ uniq ->
let
- (tyvars, rho) = splitForAllTys (idType id)
- rho_ty = substTy (mkTyVarSubst tyvars tys) rho
- (theta, tau) = splitRhoTy rho_ty
+ pred = IParam ip_name ty
+ name = mkPredName uniq (instLocSrcLoc inst_loc) pred
+ dict = Dict name pred inst_loc
in
- newMethodWithGivenTy orig id tys theta tau `thenNF_Tc` \ meth_inst ->
- returnNF_Tc (unitLIE meth_inst, instToId meth_inst)
-
-instOverloadedFun orig v arg_tys theta tau
--- This is where we introduce new functional dependencies into the LIE
- = newMethodWithGivenTy orig v arg_tys theta tau `thenNF_Tc` \ inst ->
- instFunDeps orig theta `thenNF_Tc` \ fds ->
- returnNF_Tc (instToId inst, mkLIE (inst : fds))
-
-instFunDeps orig theta
- = tcGetUnique `thenNF_Tc` \ uniq ->
- tcGetInstLoc orig `thenNF_Tc` \ loc ->
- let ifd (Class clas tys) =
- let fds = instantiateFdClassTys clas tys in
- if null fds then Nothing else Just (FunDep uniq clas fds loc)
- ifd _ = Nothing
- in returnNF_Tc (catMaybes (map ifd theta))
-
-instFunDepsOfTheta theta
- = let ifd (Class clas tys) = instantiateFdClassTys clas tys
- ifd (IParam n ty) = [([], [ty])]
- in concat (map ifd theta)
+ returnM (mapIPName (\n -> instToId dict) ip_name, dict)
+\end{code}
+
+
+
+%************************************************************************
+%* *
+\subsection{Building methods (calls of overloaded functions)}
+%* *
+%************************************************************************
+
+
+\begin{code}
+tcInstCall :: InstOrigin -> TcType -> TcM (ExprCoFn, [TcTyVar], TcType)
+tcInstCall orig fun_ty -- fun_ty is usually a sigma-type
+ = do { (tyvars, theta, tau) <- tcInstType fun_ty
+ ; dicts <- newDicts orig theta
+ ; extendLIEs dicts
+ ; let inst_fn e = unLoc (mkHsDictApp (mkHsTyApp (noLoc e) (mkTyVarTys tyvars))
+ (map instToId dicts))
+ ; return (mkCoercion inst_fn, tyvars, tau) }
+
+tcInstStupidTheta :: DataCon -> [TcType] -> TcM ()
+-- Instantiate the "stupid theta" of the data con, and throw
+-- the constraints into the constraint set
+tcInstStupidTheta data_con inst_tys
+ | null stupid_theta
+ = return ()
+ | otherwise
+ = do { stupid_dicts <- newDicts (OccurrenceOf (dataConName data_con))
+ (substTheta tenv stupid_theta)
+ ; extendLIEs stupid_dicts }
+ where
+ stupid_theta = dataConStupidTheta data_con
+ tenv = zipTopTvSubst (dataConTyVars data_con) inst_tys
+
+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
- = tcGetInstLoc orig `thenNF_Tc` \ loc ->
- newMethodWith id tys theta tau loc
-
-newMethodWith id tys theta tau loc
- = tcGetUnique `thenNF_Tc` \ new_uniq ->
- returnNF_Tc (Method new_uniq id tys theta tau loc)
-
-newMethodAtLoc :: InstLoc
- -> Id -> [TcType]
- -> NF_TcM s (Inst, TcId)
-newMethodAtLoc loc real_id tys -- Local function, similar to newMethod but with
- -- slightly different interface
- = -- Get the Id type and instantiate it at the specified types
- tcGetUnique `thenNF_Tc` \ new_uniq ->
+ = 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
+
+-- NB: the kind of the type variable to be instantiated
+-- might be a sub-kind of the type to which it is applied,
+-- notably when the latter is a type variable of kind ??
+-- Hence the call to checkKind
+-- A worry: is this needed anywhere else?
+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
+ zipWithM_ checkKind tyvars tys `thenM_`
+ newMethod inst_loc sel_id tys preds tau
+
+checkKind :: TyVar -> TcType -> TcM ()
+-- Ensure that the type has a sub-kind of the tyvar
+checkKind tv ty
+ = do { ty1 <- zonkTcType ty
+ ; if typeKind ty1 `isSubKind` tyVarKind tv
+ then return ()
+ else do
+ { traceTc (text "checkKind: adding kind constraint" <+> ppr tv <+> ppr ty)
+ ; tv1 <- tcInstTyVar tv
+ ; unifyTauTy (mkTyVarTy tv1) ty1 }}
+
+
+---------------------------
+newMethod inst_loc id tys theta tau
+ = newUnique `thenM` \ new_uniq ->
let
- (tyvars,rho) = splitForAllTys (idType real_id)
- rho_ty = ASSERT( length tyvars == length tys )
- substTy (mkTopTyVarSubst tyvars tys) rho
- (theta, tau) = splitRhoTy rho_ty
- meth_inst = Method new_uniq real_id tys theta tau loc
+ meth_id = mkUserLocal (mkMethodOcc (getOccName id)) new_uniq tau loc
+ inst = Method meth_id id tys theta tau inst_loc
+ loc = instLocSrcLoc inst_loc
in
- returnNF_Tc (meth_inst, instToId meth_inst)
+ returnM inst
\end{code}
In newOverloadedLit we convert directly to an Int or Integer if we
\begin{code}
newOverloadedLit :: InstOrigin
- -> OverloadedLit
+ -> HsOverLit
-> TcType
- -> NF_TcM s (TcExpr, LIE)
-newOverloadedLit orig (OverloadedIntegral i) ty
- | isIntTy ty && inIntRange i -- Short cut for Int
- = returnNF_Tc (int_lit, emptyLIE)
-
- | isIntegerTy ty -- Short cut for Integer
- = returnNF_Tc (integer_lit, emptyLIE)
-
- where
- intprim_lit = HsLitOut (HsIntPrim i) intPrimTy
- integer_lit = HsLitOut (HsInt i) integerTy
- int_lit = mkHsConApp intDataCon [] [intprim_lit]
-
-newOverloadedLit orig lit ty -- The general case
- = tcGetInstLoc orig `thenNF_Tc` \ loc ->
- tcGetUnique `thenNF_Tc` \ new_uniq ->
+ -> TcM (LHsExpr TcId)
+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
+ -- ToDo: noLoc sadness
+ = tcSyntaxName orig expected_ty (fromIntegerName, HsVar fi) `thenM` \ (_,expr) ->
+ mkIntegerLit i `thenM` \ integer_lit ->
+ returnM (mkHsApp (noLoc expr) integer_lit)
+ -- The mkHsApp will get the loc from the literal
+ | 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 (mkHsApp (noLoc expr) rat_lit)
+ -- The mkHsApp will get the loc from the literal
+
+ | Just expr <- shortCutFracLit r expected_ty
+ = returnM expr
+
+ | otherwise
+ = newLitInst orig lit expected_ty
+
+newLitInst :: InstOrigin -> HsOverLit -> TcType -> TcM (LHsExpr TcId)
+newLitInst orig lit expected_ty
+ = getInstLoc orig `thenM` \ loc ->
+ newUnique `thenM` \ new_uniq ->
let
- lit_inst = LitInst new_uniq lit ty loc
- in
- returnNF_Tc (HsVar (instToId lit_inst), unitLIE lit_inst)
-\end{code}
-
-\begin{code}
-newFunDepFromDict dict
- = tcGetUnique `thenNF_Tc` \ uniq ->
- let (clas, tys) = getDictClassTys dict
- fds = instantiateFdClassTys clas tys
- inst = FunDep uniq clas fds (instLoc dict)
+ lit_nm = mkSystemVarNameEncoded new_uniq FSLIT("lit")
+ -- The "encoded" bit means that we don't need to z-encode
+ -- the string every time we call this!
+ lit_inst = LitInst lit_nm lit expected_ty loc
in
- if null fds then returnNF_Tc Nothing else returnNF_Tc (Just inst)
-\end{code}
+ extendLIE lit_inst `thenM_`
+ returnM (L (instLocSrcSpan loc) (HsVar (instToId lit_inst)))
-\begin{code}
-newIPDict name ty loc
- = tcGetUnique `thenNF_Tc` \ new_uniq ->
- let d = Dict new_uniq (IParam name ty) loc in
- returnNF_Tc d
+shortCutIntLit :: Integer -> TcType -> Maybe (LHsExpr TcId) -- Returns noLoc'd result :-)
+shortCutIntLit i ty
+ | isIntTy ty && inIntRange i -- Short cut for Int
+ = Just (noLoc (HsLit (HsInt i)))
+ | isIntegerTy ty -- Short cut for Integer
+ = Just (noLoc (HsLit (HsInteger i ty)))
+ | otherwise = Nothing
+
+shortCutFracLit :: Rational -> TcType -> Maybe (LHsExpr TcId) -- Returns noLoc'd result :-)
+shortCutFracLit f ty
+ | isFloatTy ty
+ = Just (mkHsConApp floatDataCon [] [HsLit (HsFloatPrim f)])
+ | isDoubleTy ty
+ = Just (mkHsConApp doubleDataCon [] [HsLit (HsDoublePrim f)])
+ | otherwise = Nothing
+
+mkIntegerLit :: Integer -> TcM (LHsExpr TcId)
+mkIntegerLit i
+ = tcMetaTy integerTyConName `thenM` \ integer_ty ->
+ getSrcSpanM `thenM` \ span ->
+ returnM (L span $ HsLit (HsInteger i integer_ty))
+
+mkRatLit :: Rational -> TcM (LHsExpr TcId)
+mkRatLit r
+ = tcMetaTy rationalTyConName `thenM` \ rat_ty ->
+ getSrcSpanM `thenM` \ span ->
+ returnM (L span $ HsLit (HsRat r rat_ty))
\end{code}
-\begin{code}
-instToId :: Inst -> TcId
-instToId inst = instToIdBndr inst
-
-instToIdBndr :: Inst -> TcId
-instToIdBndr (Dict u (Class clas tys) (_,loc,_))
- = mkUserLocal (mkDictOcc (getOccName clas)) u (mkDictTy clas tys) loc
-instToIdBndr (Dict u (IParam n ty) (_,loc,_))
- = ipToId n ty loc
-
-instToIdBndr (Method u id tys theta tau (_,loc,_))
- = mkUserLocal (mkMethodOcc (getOccName id)) u tau loc
-
-instToIdBndr (LitInst u list ty loc)
- = mkSysLocal SLIT("lit") u ty
-
-instToIdBndr (FunDep u clas fds _)
- = mkSysLocal SLIT("FunDep") u voidTy
-
-ipToId n ty loc
- = mkUserLocal (mkIPOcc (getOccName n)) (nameUnique n) (mkPredTy (IParam n ty)) loc
-\end{code}
+%************************************************************************
+%* *
+\subsection{Zonking}
+%* *
+%************************************************************************
-Zonking
-~~~~~~~
-Zonking makes sure that the instance types are fully zonked,
-but doesn't do the same for the Id in a Method. There's no
-need, and it's a lot of extra work.
+Zonking makes sure that the instance types are fully zonked.
\begin{code}
-zonkPred :: TcPredType -> NF_TcM s 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 s Inst
-zonkInst (Dict u pred loc)
- = zonkPred pred `thenNF_Tc` \ new_pred ->
- returnNF_Tc (Dict u new_pred loc)
-
-zonkInst (Method u id tys theta tau loc)
- = zonkId id `thenNF_Tc` \ new_id ->
+zonkInst :: Inst -> TcM Inst
+zonkInst (Dict name pred loc)
+ = zonkTcPredType pred `thenM` \ new_pred ->
+ returnM (Dict name 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 `thenNF_Tc` \ new_tys ->
- zonkTcThetaType theta `thenNF_Tc` \ new_theta ->
- zonkTcType tau `thenNF_Tc` \ new_tau ->
- returnNF_Tc (Method u new_id new_tys new_theta new_tau loc)
+ zonkTcTypes tys `thenM` \ new_tys ->
+ zonkTcThetaType theta `thenM` \ new_theta ->
+ zonkTcType tau `thenM` \ new_tau ->
+ returnM (Method m new_id new_tys new_theta new_tau loc)
-zonkInst (LitInst u lit ty loc)
- = zonkTcType ty `thenNF_Tc` \ new_ty ->
- returnNF_Tc (LitInst u lit new_ty loc)
+zonkInst (LitInst nm lit ty loc)
+ = zonkTcType ty `thenM` \ new_ty ->
+ returnM (LitInst nm lit new_ty loc)
-zonkInst (FunDep u clas fds loc)
- = zonkFunDeps fds `thenNF_Tc` \ fds' ->
- returnNF_Tc (FunDep u clas fds' loc)
-
-zonkPreds preds = mapNF_Tc zonkPred preds
-zonkInsts insts = mapNF_Tc zonkInst insts
-
-zonkFunDeps fds = mapNF_Tc zonkFd fds
- where
- zonkFd (ts1, ts2)
- = zonkTcTypes ts1 `thenNF_Tc` \ ts1' ->
- zonkTcTypes ts2 `thenNF_Tc` \ ts2' ->
- returnNF_Tc (ts1', ts2')
-
-zonkTvFunDeps fds = mapNF_Tc zonkFd fds
- where
- zonkFd (tvs1, tvs2)
- = zonkTcTyVars tvs1 `thenNF_Tc` \ tvs1' ->
- zonkTcTyVars tvs2 `thenNF_Tc` \ tvs2' ->
- returnNF_Tc (tvs1', tvs2')
+zonkInsts insts = mappM zonkInst insts
\end{code}
-Printing
-~~~~~~~~
+%************************************************************************
+%* *
+\subsection{Printing}
+%* *
+%************************************************************************
+
ToDo: improve these pretty-printing things. The ``origin'' is really only
relevant in error messages.
instance Outputable Inst where
ppr inst = pprInst inst
-pprInst (LitInst u lit ty loc)
- = hsep [case lit of
- OverloadedIntegral i -> integer i
- OverloadedFractional f -> rational f,
- ptext SLIT("at"),
- ppr ty,
- show_uniq u]
-
-pprInst (Dict u pred loc) = pprPred pred <+> show_uniq u
-
-pprInst m@(Method u id tys theta tau loc)
- = hsep [ppr id, ptext SLIT("at"),
- brackets (interppSP tys) {- ,
- ppr theta, ppr tau,
- show_uniq u,
- ppr (instToId m) -}]
-
-pprInst (FunDep _ clas fds loc)
- = hsep [ppr clas, ppr fds]
-
-tidyPred :: TidyEnv -> TcPredType -> (TidyEnv, TcPredType)
-tidyPred env (Class clas tys)
- = (env', Class clas tys')
- where
- (env', tys') = tidyOpenTypes env tys
-tidyPred env (IParam n ty)
- = (env', IParam n ty')
- where
- (env', ty') = tidyOpenType env ty
+pprDictsTheta :: [Inst] -> SDoc
+-- Print in type-like fashion (Eq a, Show b)
+pprDictsTheta dicts = pprTheta (map dictPred dicts)
-tidyInst :: TidyEnv -> Inst -> (TidyEnv, Inst)
-tidyInst env (LitInst u lit ty loc)
- = (env', LitInst u lit ty' loc)
+pprDictsInFull :: [Inst] -> SDoc
+-- Print in type-like fashion, but with source location
+pprDictsInFull dicts
+ = vcat (map go dicts)
where
- (env', ty') = tidyOpenType env ty
+ go dict = sep [quotes (ppr (dictPred dict)), nest 2 (pprInstLoc (instLoc dict))]
-tidyInst env (Dict u pred loc)
- = (env', Dict u pred' loc)
- where
- (env', pred') = tidyPred env pred
-
-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
+pprInsts :: [Inst] -> SDoc
+-- Debugging: print the evidence :: type
+pprInsts insts = brackets (interpp'SP insts)
+
+pprInst, pprInstInFull :: Inst -> SDoc
+-- Debugging: print the evidence :: type
+pprInst (LitInst nm lit ty loc) = ppr nm <+> dcolon <+> ppr ty
+pprInst (Dict nm pred loc) = ppr nm <+> dcolon <+> pprPred pred
+
+pprInst m@(Method inst_id id tys theta tau loc)
+ = ppr inst_id <+> dcolon <+>
+ braces (sep [ppr id <+> ptext SLIT("at"),
+ brackets (sep (map pprParendType tys))])
+
+pprInstInFull inst
+ = sep [quotes (pprInst inst), nest 2 (pprInstLoc (instLoc inst))]
+
+pprDFuns :: [DFunId] -> SDoc
+-- Prints the dfun as an instance declaration
+pprDFuns dfuns = vcat [ hang (ppr (getSrcLoc dfun) <> colon)
+ 2 (ptext SLIT("instance") <+> sep [pprThetaArrow theta,
+ pprClassPred clas tys])
+ | dfun <- dfuns
+ , let (_, theta, clas, tys) = tcSplitDFunTy (idType dfun) ]
+ -- Print without the for-all, which the programmer doesn't write
+
+tidyInst :: TidyEnv -> Inst -> Inst
+tidyInst env (LitInst nm lit ty loc) = LitInst nm lit (tidyType env ty) loc
+tidyInst env (Dict nm pred loc) = Dict nm (tidyPred env pred) loc
+tidyInst env (Method u id tys theta tau loc) = Method u id (tidyTypes env tys) theta tau loc
+
+tidyMoreInsts :: TidyEnv -> [Inst] -> (TidyEnv, [Inst])
+-- This function doesn't assume that the tyvars are in scope
+-- so it works like tidyOpenType, returning a TidyEnv
+tidyMoreInsts env insts
+ = (env', map (tidyInst env') insts)
where
- (env', tys') = tidyOpenTypes env tys
+ env' = tidyFreeTyVars env (tyVarsOfInsts insts)
--- this case shouldn't arise... (we never print fundeps)
-tidyInst env fd@(FunDep _ clas fds loc)
- = (env, fd)
+tidyInsts :: [Inst] -> (TidyEnv, [Inst])
+tidyInsts insts = tidyMoreInsts emptyTidyEnv insts
-tidyInsts env insts = mapAccumL tidyInst env insts
-
-show_uniq u = ifPprDebug (text "{-" <> ppr u <> text "-}")
+showLIE :: SDoc -> TcM () -- Debugging
+showLIE str
+ = do { lie_var <- getLIEVar ;
+ lie <- readMutVar lie_var ;
+ traceTc (str <+> vcat (map pprInstInFull (lieToList lie))) }
\end{code}
%************************************************************************
%* *
-\subsection[InstEnv-types]{Type declarations}
+ Extending the instance environment
%* *
%************************************************************************
\begin{code}
-type InstanceMapper = Class -> InstEnv
+tcExtendLocalInstEnv :: [DFunId] -> TcM a -> TcM a
+ -- Add new locally-defined instances
+tcExtendLocalInstEnv dfuns thing_inside
+ = do { traceDFuns dfuns
+ ; env <- getGblEnv
+ ; dflags <- getDOpts
+ ; inst_env' <- foldlM (addInst dflags) (tcg_inst_env env) dfuns
+ ; let env' = env { tcg_insts = dfuns ++ tcg_insts env,
+ tcg_inst_env = inst_env' }
+ ; setGblEnv env' thing_inside }
+
+addInst :: DynFlags -> InstEnv -> DFunId -> TcM InstEnv
+-- Check that the proposed new instance is OK,
+-- and then add it to the home inst env
+addInst dflags home_ie dfun
+ = do { -- Instantiate the dfun type so that we extend the instance
+ -- envt with completely fresh template variables
+ -- This is important because the template variables must
+ -- not overlap with anything in the things being looked up
+ -- (since we do unification).
+ -- We use tcSkolType because we don't want to allocate fresh
+ -- *meta* type variables.
+ (tvs', theta', tau') <- tcSkolType (InstSkol dfun) (idType dfun)
+ ; let (cls, tys') = tcSplitDFunHead tau'
+ dfun' = setIdType dfun (mkSigmaTy tvs' theta' tau')
+
+ -- Load imported instances, so that we report
+ -- duplicates correctly
+ ; pkg_ie <- loadImportedInsts cls tys'
+
+ -- Check functional dependencies
+ ; case checkFunDeps (pkg_ie, home_ie) dfun' of
+ Just dfuns -> funDepErr dfun dfuns
+ Nothing -> return ()
+
+ -- Check for duplicate instance decls
+ ; let { (matches, _) = lookupInstEnv dflags (pkg_ie, home_ie) cls tys'
+ ; dup_dfuns = [dup_dfun | (_, (_, dup_tys, dup_dfun)) <- matches,
+ isJust (tcMatchTys (mkVarSet tvs') tys' dup_tys)] }
+ -- Find memebers of the match list which
+ -- dfun itself matches. If the match is 2-way, it's a duplicate
+ ; case dup_dfuns of
+ dup_dfun : _ -> dupInstErr dfun dup_dfun
+ [] -> return ()
+
+ -- OK, now extend the envt
+ ; return (extendInstEnv home_ie dfun') }
+
+
+traceDFuns dfuns
+ = traceTc (text "Adding instances:" <+> vcat (map pp dfuns))
+ where
+ pp dfun = ppr dfun <+> dcolon <+> ppr (idType dfun)
+
+funDepErr dfun dfuns
+ = addDictLoc dfun $
+ addErr (hang (ptext SLIT("Functional dependencies conflict between instance declarations:"))
+ 2 (pprDFuns (dfun:dfuns)))
+dupInstErr dfun dup_dfun
+ = addDictLoc dfun $
+ addErr (hang (ptext SLIT("Duplicate instance declarations:"))
+ 2 (pprDFuns [dfun, dup_dfun]))
+
+addDictLoc dfun thing_inside
+ = setSrcSpan (mkSrcSpan loc loc) thing_inside
+ where
+ loc = getSrcLoc dfun
\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.
+%************************************************************************
+%* *
+\subsection{Looking up Insts}
+%* *
+%************************************************************************
\begin{code}
-data LookupInstResult s
+data LookupInstResult
= NoInstance
- | SimpleInst TcExpr -- Just a variable, type application, or literal
- | GenInst [Inst] TcExpr -- The expression and its needed insts
-
-lookupInst :: Inst
- -> NF_TcM s (LookupInstResult s)
+ | SimpleInst (LHsExpr TcId) -- Just a variable, type application, or literal
+ | GenInst [Inst] (LHsExpr TcId) -- The expression and its needed insts
--- Dictionaries
+lookupInst :: Inst -> TcM LookupInstResult
+-- 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
-lookupInst dict@(Dict _ (Class clas tys) loc)
- = case lookupInstEnv (classInstEnv clas) tys of
-
- FoundInst tenv dfun_id
- -> let
- subst = mkSubst (tyVarsOfTypes tys) tenv
- (tyvars, rho) = splitForAllTys (idType dfun_id)
- ty_args = map subst_tv tyvars
- dfun_rho = substTy subst rho
- (theta, tau) = splitRhoTy dfun_rho
- ty_app = mkHsTyApp (HsVar dfun_id) ty_args
- subst_tv tv = case lookupSubstEnv tenv tv of
- Just (DoneTy ty) -> ty
- -- tenv should bind all the tyvars
- in
- if null theta then
- returnNF_Tc (SimpleInst ty_app)
- else
- newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, dict_ids) ->
- let
- rhs = mkHsDictApp ty_app dict_ids
- in
- returnNF_Tc (GenInst dicts rhs)
-
- other -> returnNF_Tc NoInstance
-lookupInst dict@(Dict _ _ loc) = returnNF_Tc NoInstance
-- Methods
lookupInst inst@(Method _ id tys theta _ loc)
- = newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, dict_ids) ->
- returnNF_Tc (GenInst dicts (mkHsDictApp (mkHsTyApp (HsVar id) tys) dict_ids))
+ = newDictsAtLoc loc theta `thenM` \ dicts ->
+ returnM (GenInst dicts (mkHsDictApp (mkHsTyApp (L span (HsVar id)) tys) (map instToId dicts)))
+ where
+ span = instLocSrcSpan loc
-- Literals
-lookupInst inst@(LitInst u (OverloadedIntegral 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
+-- 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 _nm (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 ->
+ mkIntegerLit i `thenM` \ integer_lit ->
+ returnM (GenInst [method_inst]
+ (mkHsApp (L (instLocSrcSpan loc)
+ (HsVar (instToId method_inst))) integer_lit))
+
+lookupInst inst@(LitInst _nm (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] (mkHsApp (L (instLocSrcSpan loc)
+ (HsVar (instToId method_inst))) rat_lit))
- | isIntegerTy ty -- Short cut for Integer
- = returnNF_Tc (GenInst [] integer_lit)
+-- Dictionaries
+lookupInst (Dict _ pred loc)
+ = do { mb_result <- lookupPred pred
+ ; case mb_result of {
+ Nothing -> return NoInstance ;
+ Just (tenv, dfun_id) -> do
+
+ -- tenv is a substitution that instantiates the dfun_id
+ -- to match the requested result type.
+ --
+ -- We ASSUME that the dfun is quantified over the very same tyvars
+ -- that are bound by the tenv.
+ --
+ -- However, the dfun
+ -- might have some tyvars that *only* appear in arguments
+ -- dfun :: forall a b. C a b, Ord b => D [a]
+ -- We instantiate b to a flexi type variable -- it'll presumably
+ -- become fixed later via functional dependencies
+ { use_stage <- getStage
+ ; checkWellStaged (ptext SLIT("instance for") <+> quotes (ppr pred))
+ (topIdLvl dfun_id) use_stage
+
+ -- 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 open_tvs to instantiate any un-substituted tyvars.
+ ; let (tyvars, rho) = tcSplitForAllTys (idType dfun_id)
+ open_tvs = filter (`notElemTvSubst` tenv) tyvars
+ ; open_tvs' <- mappM tcInstTyVar open_tvs
+ ; let
+ tenv' = extendTvSubstList tenv open_tvs (mkTyVarTys open_tvs')
+ -- Since the open_tvs' are freshly made, they cannot possibly be captured by
+ -- any nested for-alls in rho. So the in-scope set is unchanged
+ dfun_rho = substTy tenv' rho
+ (theta, _) = tcSplitPhiTy dfun_rho
+ ty_app = mkHsTyApp (L (instLocSrcSpan loc) (HsVar dfun_id))
+ (map (substTyVar tenv') tyvars)
+ ; if null theta then
+ returnM (SimpleInst ty_app)
+ else do
+ { dicts <- newDictsAtLoc loc theta
+ ; let rhs = mkHsDictApp ty_app (map instToId dicts)
+ ; returnM (GenInst dicts rhs)
+ }}}}
+
+---------------
+lookupPred :: TcPredType -> TcM (Maybe (TvSubst, DFunId))
+-- Look up a class constraint in the instance environment
+lookupPred pred@(ClassP clas tys)
+ = do { pkg_ie <- loadImportedInsts clas tys
+ -- Suck in any instance decls that may be relevant
+ ; tcg_env <- getGblEnv
+ ; dflags <- getDOpts
+ ; case lookupInstEnv dflags (pkg_ie, tcg_inst_env tcg_env) clas tys of {
+ ([(tenv, (_,_,dfun_id))], [])
+ -> do { traceTc (text "lookupInst success" <+>
+ vcat [text "dict" <+> ppr pred,
+ text "witness" <+> ppr dfun_id
+ <+> ppr (idType dfun_id) ])
+ -- Record that this dfun is needed
+ ; record_dfun_usage dfun_id
+ ; return (Just (tenv, dfun_id)) } ;
+
+ (matches, unifs)
+ -> do { traceTc (text "lookupInst fail" <+>
+ vcat [text "dict" <+> ppr pred,
+ text "matches" <+> ppr matches,
+ text "unifs" <+> ppr unifs])
+ -- In the case of overlap (multiple matches) we report
+ -- NoInstance here. That has the effect of making the
+ -- context-simplifier return the dict as an irreducible one.
+ -- Then it'll be given to addNoInstanceErrs, which will do another
+ -- lookupInstEnv to get the detailed info about what went wrong.
+ ; return Nothing }
+ }}
+
+lookupPred ip_pred = return Nothing
+
+record_dfun_usage dfun_id
+ = do { dflags <- getDOpts
+ ; let dfun_name = idName dfun_id
+ dfun_mod = nameModule dfun_name
+ ; if isInternalName dfun_name || not (isHomeModule dflags dfun_mod)
+ then return () -- internal, or in another package
+ else do { tcg_env <- getGblEnv
+ ; updMutVar (tcg_inst_uses tcg_env)
+ (`addOneToNameSet` idName dfun_id) }}
+
+
+tcGetInstEnvs :: TcM (InstEnv, InstEnv)
+-- Gets both the external-package inst-env
+-- and the home-pkg inst env (includes module being compiled)
+tcGetInstEnvs = do { eps <- getEps; env <- getGblEnv;
+ return (eps_inst_env eps, tcg_inst_env env) }
+\end{code}
- | in_int_range -- It's overloaded but small enough to fit into an Int
- = tcLookupValueByKey fromIntClassOpKey `thenNF_Tc` \ from_int ->
- newMethodAtLoc loc from_int [ty] `thenNF_Tc` \ (method_inst, method_id) ->
- returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) int_lit))
- | otherwise -- Alas, it is overloaded and a big literal!
- = tcLookupValueByKey fromIntegerClassOpKey `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
- intprim_lit = HsLitOut (HsIntPrim i) intPrimTy
- integer_lit = HsLitOut (HsInt i) integerTy
- int_lit = mkHsConApp intDataCon [] [intprim_lit]
--- 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).
-
-lookupInst inst@(LitInst u (OverloadedFractional f) ty loc)
- | isFloatTy ty = returnNF_Tc (GenInst [] float_lit)
- | isDoubleTy ty = returnNF_Tc (GenInst [] double_lit)
+%************************************************************************
+%* *
+ Re-mappable syntax
+%* *
+%************************************************************************
- | otherwise
- = tcLookupValueByKey fromRationalClassOpKey `thenNF_Tc` \ from_rational ->
- -- The type Rational isn't wired in so we have to conjure it up
- tcLookupTyConByKey rationalTyConKey `thenNF_Tc` \ rational_tycon ->
- let
- rational_ty = mkSynTy rational_tycon []
- rational_lit = HsLitOut (HsFrac f) rational_ty
- in
- newMethodAtLoc loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) ->
- returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) rational_lit))
+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:
- where
- floatprim_lit = HsLitOut (HsFloatPrim f) floatPrimTy
- float_lit = mkHsConApp floatDataCon [] [floatprim_lit]
- doubleprim_lit = HsLitOut (HsDoublePrim f) doublePrimTy
- double_lit = mkHsConApp doubleDataCon [] [doubleprim_lit]
+ (>>) :: HB m n mn => m a -> n b -> mn b
--- there are no `instances' of functional dependencies or implicit params
+So the idea is to generate a local binding for (>>), thus:
-lookupInst _ = returnNF_Tc NoInstance
+ let then72 :: forall a b. m a -> m b -> m b
+ then72 = ...something involving the user's (>>)...
+ in
+ ...the do-expression...
-\end{code}
+Now the do-expression can proceed using then72, which has exactly
+the expected type.
-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.
+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}
-lookupSimpleInst :: InstEnv
- -> Class
- -> [Type] -- Look up (c,t)
- -> NF_TcM s (Maybe [(Class,[Type])]) -- Here are the needed (c,t)s
-
-lookupSimpleInst class_inst_env clas tys
- = case lookupInstEnv class_inst_env tys of
- FoundInst tenv dfun
- -> returnNF_Tc (Just (substClasses (mkSubst emptyInScopeSet tenv) theta'))
- where
- (_, theta, _) = splitSigmaTy (idType dfun)
- theta' = map (\(Class clas tys) -> (clas,tys)) theta
-
- other -> returnNF_Tc Nothing
+tcSyntaxName :: InstOrigin
+ -> TcType -- Type to instantiate it at
+ -> (Name, HsExpr Name) -- (Standard name, user name)
+ -> TcM (Name, HsExpr TcId) -- (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)
+ sigma1 = 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 sigma1) $
+
+ -- Check that the user-supplied thing has the
+ -- same type as the standard one.
+ -- Tiresome jiggling because tcCheckSigma takes a located expression
+ getSrcSpanM `thenM` \ span ->
+ tcCheckSigma (L span user_nm_expr) sigma1 `thenM` \ expr ->
+ returnM (std_nm, unLoc expr)
+
+tcStdSyntaxName :: InstOrigin
+ -> TcType -- Type to instantiate it at
+ -> Name -- Standard name
+ -> TcM (Name, HsExpr TcId) -- (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