\begin{code}
module Inst (
- LIE, emptyLIE, unitLIE, plusLIE, consLIE, zonkLIE,
- plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
-
Inst,
- pprInst, pprInsts, pprInstsInFull, tidyInsts, tidyMoreInsts,
- newDictsFromOld, newDicts, cloneDict,
- newMethod, newMethodWithGivenTy, newMethodAtLoc,
- newOverloadedLit, newIPDict, tcInstCall,
+ pprInstances, pprDictsTheta, pprDictsInFull, -- User error messages
+ showLIE, pprInst, pprInsts, pprInstInFull, -- Debugging messages
+
+ tidyInsts, tidyMoreInsts,
+
+ newDicts, newDictAtLoc, newDictsAtLoc, cloneDict,
+ shortCutFracLit, shortCutIntLit, newIPDict,
+ newMethod, newMethodFromName, newMethodWithGivenTy,
+ tcInstClassOp, tcInstStupidTheta,
+ tcSyntaxName, isHsVar,
tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE,
- ipNamesOfInst, ipNamesOfInsts, predsOfInst, predsOfInsts,
+ ipNamesOfInst, ipNamesOfInsts, fdPredsOfInst, fdPredsOfInsts,
instLoc, getDictClassTys, dictPred,
- lookupInst, lookupSimpleInst, LookupInstResult(..),
+ lookupInst, LookupInstResult(..), lookupPred,
+ tcExtendLocalInstEnv, tcGetInstEnvs, getOverlapFlag,
isDict, isClassDict, isMethod,
- isLinearInst, linearInstType,
- isTyVarDict, isStdClassTyVarDict, isMethodFor,
- instBindingRequired, instCanBeGeneralised,
+ isLinearInst, linearInstType, isIPDict, isInheritableInst,
+ isTyVarDict, isMethodFor,
zonkInst, zonkInsts,
instToId, instName,
- InstOrigin(..), InstLoc, pprInstLoc
+ InstOrigin(..), InstLoc(..), pprInstLoc
) where
#include "HsVersions.h"
-import HsSyn ( HsLit(..), HsOverLit(..), HsExpr(..) )
-import TcHsSyn ( TcExpr, TcId, TypecheckedHsExpr,
- mkHsTyApp, mkHsDictApp, mkHsConApp, zonkId
- )
-import TcMonad
-import TcEnv ( TcIdSet, tcGetInstEnv, tcLookupId )
-import InstEnv ( InstLookupResult(..), lookupInstEnv )
-import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType,
- zonkTcThetaType, tcInstTyVar, tcInstType,
+import {-# SOURCE #-} TcExpr( tcPolyExpr )
+
+import HsSyn ( HsLit(..), HsOverLit(..), HsExpr(..), LHsExpr, mkHsApp,
+ nlHsLit, nlHsVar )
+import TcHsSyn ( mkHsTyApp, mkHsDictApp, zonkId )
+import TcRnMonad
+import TcEnv ( tcLookupId, checkWellStaged, topIdLvl, tcMetaTy )
+import InstEnv ( DFunId, InstEnv, Instance(..), OverlapFlag(..),
+ lookupInstEnv, extendInstEnv, pprInstances,
+ instanceHead, instanceDFunId, setInstanceDFunId )
+import FunDeps ( checkFunDeps )
+import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType, zonkTcThetaType,
+ tcInstTyVar, tcInstSkolType
)
-import TcType ( Type, TcType, TcThetaType, TcPredType, TcTauType, TcTyVarSet,
- SourceType(..), PredType, ThetaType, TyVarDetails(VanillaTv),
- tcSplitForAllTys, tcSplitForAllTys,
- tcSplitMethodTy, tcSplitPhiTy, tcFunArgTy,
+import TcType ( Type, TcType, TcThetaType, TcTyVarSet, TcPredType,
+ BoxyRhoType,
+ PredType(..), SkolemInfo(..), typeKind, mkSigmaTy,
+ tcSplitForAllTys, applyTys,
+ tcSplitPhiTy, tcSplitDFunHead,
isIntTy,isFloatTy, isIntegerTy, isDoubleTy,
- tcIsTyVarTy, mkPredTy, mkTyVarTy, mkTyVarTys,
+ mkPredTy, mkTyVarTys,
tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tidyPred,
- isClassPred, isTyVarClassPred, isLinearPred,
- getClassPredTys, getClassPredTys_maybe, mkPredName,
- tidyType, tidyTypes, tidyFreeTyVars,
- tcCmpType, tcCmpTypes, tcCmpPred
+ isClassPred, isTyVarClassPred, isLinearPred,
+ getClassPredTys, mkPredName,
+ isInheritablePred, isIPPred,
+ tidyType, tidyTypes, tidyFreeTyVars, tcSplitSigmaTy,
+ pprPred, pprParendType, pprTheta
)
+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 Class ( Class )
-import Id ( Id, idName, idType, mkUserLocal, mkSysLocal, mkLocalId, setIdUnique )
-import PrelInfo ( isStandardClass, isCcallishClass, isNoDictClass )
-import Name ( Name, mkMethodOcc, getOccName )
-import PprType ( pprPred, pprParendType )
-import Subst ( emptyInScopeSet, mkSubst,
- substTy, substTyWith, substTheta, mkTyVarSubst, mkTopTyVarSubst
- )
+import DataCon ( DataCon, dataConTyVars, dataConStupidTheta, dataConName, dataConWrapId )
+import Id ( Id, idName, idType, mkUserLocal, mkLocalId )
+import Name ( Name, mkMethodOcc, getOccName, getSrcLoc, nameModule,
+ isInternalName, setNameUnique )
+import NameSet ( addOneToNameSet )
import Literal ( inIntRange )
-import VarEnv ( TidyEnv, lookupSubstEnv, SubstResult(..) )
-import VarSet ( elemVarSet, emptyVarSet, unionVarSet )
+import Var ( TyVar, tyVarKind, setIdType )
+import VarEnv ( TidyEnv, emptyTidyEnv )
+import VarSet ( elemVarSet, emptyVarSet, unionVarSet, mkVarSet )
import TysWiredIn ( floatDataCon, doubleDataCon )
-import PrelNames( fromIntegerName, fromRationalName )
-import Util ( thenCmp, equalLength )
+import PrelNames ( integerTyConName, fromIntegerName, fromRationalName, rationalTyConName )
import BasicTypes( IPName(..), mapIPName, ipNameName )
-
-import Bag
+import UniqSupply( uniqsFromSupply )
+import SrcLoc ( mkSrcSpan, noLoc, unLoc, Located(..) )
+import DynFlags ( DynFlag(..), dopt )
+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 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
- Id
- TcPredType
- InstLoc
-
- | Method
- Id
-
- 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
- Id
- HsOverLit -- The literal from the occurrence site
- TcType -- The type at which the literal is used
- InstLoc
-\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 `tcCmpPred` pred2
-cmpInst (Dict _ _ _) other = LT
-
-cmpInst (Method _ _ _ _ _ _) (Dict _ _ _) = GT
-cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) = (id1 `compare` id2) `thenCmp` (tys1 `tcCmpTypes` tys2)
-cmpInst (Method _ _ _ _ _ _) other = LT
-
-cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `compare` lit2) `thenCmp` (ty1 `tcCmpType` ty2)
-cmpInst (LitInst _ _ _ _) other = GT
-
--- and they can only have HsInt or HsFracs in them.
-\end{code}
-
Selection
~~~~~~~~~
instName inst = idName (instToId inst)
instToId :: Inst -> TcId
-instToId (Dict id _ _) = id
-instToId (Method id _ _ _ _ _) = id
-instToId (LitInst id _ _ _) = id
+instToId (LitInst nm _ ty _) = mkLocalId nm ty
+instToId (Dict nm pred _) = mkLocalId nm (mkPredTy pred)
+instToId (Method id _ _ _ _) = id
-instLoc (Dict _ _ loc) = loc
-instLoc (Method _ _ _ _ _ loc) = loc
-instLoc (LitInst _ _ _ loc) = loc
+instLoc (Dict _ _ loc) = loc
+instLoc (Method _ _ _ _ loc) = loc
+instLoc (LitInst _ _ _ loc) = loc
dictPred (Dict _ pred _ ) = pred
dictPred inst = pprPanic "dictPred" (ppr inst)
getDictClassTys (Dict _ pred _) = getClassPredTys pred
-predsOfInsts :: [Inst] -> [PredType]
-predsOfInsts insts = concatMap predsOfInst insts
+-- 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
+
+fdPredsOfInsts :: [Inst] -> [PredType]
+fdPredsOfInsts insts = concatMap fdPredsOfInst insts
+
+isInheritableInst (Dict _ pred _) = isInheritablePred pred
+isInheritableInst (Method _ _ _ theta _) = all isInheritablePred theta
+isInheritableInst other = True
-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.
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]
-ipNamesOfInst (Dict _ (IParam n _) _) = [ipNameName n]
-ipNamesOfInst (Method _ _ _ theta _ _) = [ipNameName n | IParam n _ <- theta]
-ipNamesOfInst other = []
+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
+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
+
tyVarsOfInsts insts = foldr (unionVarSet . tyVarsOfInst) emptyVarSet insts
tyVarsOfLIE lie = tyVarsOfInsts (lieToList lie)
\end{code}
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
+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
isLinearInst :: Inst -> Bool
isLinearInst (Dict _ pred _) = isLinearPred pred
linearInstType :: Inst -> TcType -- %x::t --> t
linearInstType (Dict _ (IParam _ ty) _) = ty
-
-
-isStdClassTyVarDict (Dict _ pred _) = case getClassPredTys_maybe pred of
- Just (clas, [ty]) -> isStandardClass clas && tcIsTyVarTy ty
- other -> False
\end{code}
-Two predicates which deal with the case where class constraints don't
-necessarily result in bindings. The first tells whether an @Inst@
-must be witnessed by an actual binding; the second tells whether an
-@Inst@ can be generalised over.
-
-\begin{code}
-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}
%************************************************************************
\begin{code}
newDicts :: InstOrigin
-> TcThetaType
- -> NF_TcM [Inst]
+ -> TcM [Inst]
newDicts orig theta
- = tcGetInstLoc orig `thenNF_Tc` \ loc ->
+ = getInstLoc orig `thenM` \ loc ->
newDictsAtLoc loc theta
-cloneDict :: Inst -> NF_TcM Inst
-cloneDict (Dict id ty loc) = tcGetUnique `thenNF_Tc` \ uniq ->
- returnNF_Tc (Dict (setIdUnique id uniq) ty loc)
-
-newDictsFromOld :: Inst -> TcThetaType -> NF_TcM [Inst]
-newDictsFromOld (Dict _ _ loc) theta = newDictsAtLoc loc theta
-
--- Local function, similar to newDicts,
--- but with slightly different interface
-newDictsAtLoc :: InstLoc
- -> TcThetaType
- -> NF_TcM [Inst]
-newDictsAtLoc inst_loc@(_,loc,_) theta
- = tcGetUniques `thenNF_Tc` \ new_uniqs ->
- returnNF_Tc (zipWith mk_dict new_uniqs 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
- mk_dict uniq pred = Dict (mkLocalId (mkPredName uniq loc pred) (mkPredTy pred)) pred inst_loc
+ 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
- -> NF_TcM (IPName Id, Inst)
+ -> TcM (IPName Id, Inst)
newIPDict orig ip_name ty
- = tcGetInstLoc orig `thenNF_Tc` \ inst_loc@(_,loc,_) ->
- tcGetUnique `thenNF_Tc` \ uniq ->
+ = getInstLoc orig `thenM` \ inst_loc ->
+ newUnique `thenM` \ uniq ->
let
pred = IParam ip_name ty
- id = mkLocalId (mkPredName uniq loc pred) (mkPredTy pred)
+ name = mkPredName uniq (instLocSrcLoc inst_loc) pred
+ dict = Dict name pred inst_loc
in
- returnNF_Tc (mapIPName (\n -> id) ip_name, Dict id pred inst_loc)
+ returnM (mapIPName (\n -> instToId dict) ip_name, dict)
\end{code}
+
%************************************************************************
%* *
\subsection{Building methods (calls of overloaded functions)}
\begin{code}
-tcInstCall :: InstOrigin -> TcType -> NF_TcM (TypecheckedHsExpr -> TypecheckedHsExpr, LIE, TcType)
-tcInstCall orig fun_ty -- fun_ty is usually a sigma-type
- = tcInstType VanillaTv fun_ty `thenNF_Tc` \ (tyvars, theta, tau) ->
- newDicts orig theta `thenNF_Tc` \ dicts ->
- let
- inst_fn e = mkHsDictApp (mkHsTyApp e (mkTyVarTys tyvars)) (map instToId dicts)
- in
- returnNF_Tc (inst_fn, mkLIE dicts, 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) = tcSplitForAllTys (idType id)
- rho_ty = substTyWith tyvars tys rho
- (pred, tau) = tcSplitMethodTy rho_ty
- in
- newMethodWithGivenTy orig id tys [pred] tau
-
-newMethodWithGivenTy orig id tys theta tau
- = tcGetInstLoc orig `thenNF_Tc` \ loc ->
- newMethodWith loc id tys theta tau
-
-newMethodWith inst_loc@(_,loc,_) id tys theta tau
- = tcGetUnique `thenNF_Tc` \ new_uniq ->
- let
- meth_id = mkUserLocal (mkMethodOcc (getOccName id)) new_uniq tau loc
+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 -> BoxyRhoType -> 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
+ = getInstLoc orig `thenM` \ loc ->
+ newMethod loc id tys `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)
in
- returnNF_Tc (Method meth_id id tys theta tau inst_loc)
-
-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
+ zipWithM_ checkKind tyvars tys `thenM_`
+ newMethod inst_loc sel_id tys
+
+checkKind :: TyVar -> TcType -> TcM ()
+-- Ensure that the type has a sub-kind of the tyvar
+checkKind tv ty
+ = do { let ty1 = ty
+ -- ty1 <- zonkTcType ty
+ ; if typeKind ty1 `isSubKind` tyVarKind tv
+ then return ()
+ else
+
+ pprPanic "checkKind: adding kind constraint"
+ (vcat [ppr tv <+> ppr (tyVarKind tv),
+ ppr ty <+> ppr ty1 <+> ppr (typeKind ty1)])
+ }
+-- do { tv1 <- tcInstTyVar tv
+-- ; unifyType ty1 (mkTyVarTy tv1) } }
+
+
+---------------------------
+newMethod inst_loc id tys
+ = newUnique `thenM` \ new_uniq ->
let
- (tyvars,rho) = tcSplitForAllTys (idType real_id)
- rho_ty = ASSERT( equalLength tyvars tys )
- substTy (mkTopTyVarSubst tyvars tys) rho
- (theta, tau) = tcSplitPhiTy rho_ty
+ (theta,tau) = tcSplitPhiTy (applyTys (idType id) tys)
+ meth_id = mkUserLocal (mkMethodOcc (getOccName id)) new_uniq tau loc
+ inst = Method meth_id id tys theta inst_loc
+ loc = instLocSrcLoc inst_loc
in
- newMethodWith inst_loc real_id tys theta tau `thenNF_Tc` \ meth_inst ->
- returnNF_Tc (meth_inst, instToId meth_inst)
+ returnM inst
\end{code}
-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}
-newOverloadedLit :: InstOrigin
- -> HsOverLit
- -> TcType
- -> NF_TcM (TcExpr, LIE)
-newOverloadedLit orig lit ty
- | Just expr <- shortCutLit lit ty
- = returnNF_Tc (expr, emptyLIE)
-
- | otherwise
- = tcGetInstLoc orig `thenNF_Tc` \ loc ->
- tcGetUnique `thenNF_Tc` \ new_uniq ->
- let
- lit_inst = LitInst lit_id lit ty loc
- lit_id = mkSysLocal FSLIT("lit") new_uniq ty
- in
- returnNF_Tc (HsVar (instToId lit_inst), unitLIE lit_inst)
-
-shortCutLit :: HsOverLit -> TcType -> Maybe TcExpr
-shortCutLit (HsIntegral i fi) ty
- | isIntTy ty && inIntRange i && fi == fromIntegerName -- Short cut for Int
+shortCutIntLit :: Integer -> TcType -> Maybe (HsExpr TcId)
+shortCutIntLit i ty
+ | isIntTy ty && inIntRange i -- Short cut for Int
= Just (HsLit (HsInt i))
- | isIntegerTy ty && fi == fromIntegerName -- Short cut for Integer
- = Just (HsLit (HsInteger i))
-
-shortCutLit (HsFractional f fr) ty
- | isFloatTy ty && fr == fromRationalName
- = Just (mkHsConApp floatDataCon [] [HsLit (HsFloatPrim f)])
- | isDoubleTy ty && fr == fromRationalName
- = Just (mkHsConApp doubleDataCon [] [HsLit (HsDoublePrim f)])
-
-shortCutLit lit ty
- = Nothing
+ | isIntegerTy ty -- Short cut for Integer
+ = Just (HsLit (HsInteger i ty))
+ | otherwise = Nothing
+
+shortCutFracLit :: Rational -> TcType -> Maybe (HsExpr TcId)
+shortCutFracLit f ty
+ | isFloatTy ty
+ = Just (mk_lit floatDataCon (HsFloatPrim f))
+ | isDoubleTy ty
+ = Just (mk_lit doubleDataCon (HsDoublePrim f))
+ | otherwise = Nothing
+ where
+ mk_lit con lit = HsApp (nlHsVar (dataConWrapId con)) (nlHsLit lit)
+
+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))
+
+isHsVar :: HsExpr Name -> Name -> Bool
+isHsVar (HsVar f) g = f==g
+isHsVar other g = False
\end{code}
%* *
%************************************************************************
-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.
+Zonking makes sure that the instance types are fully zonked.
\begin{code}
-zonkInst :: Inst -> NF_TcM Inst
-zonkInst (Dict id pred loc)
- = zonkTcPredType pred `thenNF_Tc` \ new_pred ->
- returnNF_Tc (Dict id new_pred loc)
+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 `thenNF_Tc` \ new_id ->
+zonkInst (Method m id tys theta 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 m new_id new_tys new_theta new_tau loc)
+ zonkTcTypes tys `thenM` \ new_tys ->
+ zonkTcThetaType theta `thenM` \ new_theta ->
+ returnM (Method m new_id new_tys new_theta loc)
-zonkInst (LitInst id lit ty loc)
- = zonkTcType ty `thenNF_Tc` \ new_ty ->
- returnNF_Tc (LitInst id lit new_ty loc)
+zonkInst (LitInst nm lit ty loc)
+ = zonkTcType ty `thenM` \ new_ty ->
+ returnM (LitInst nm lit new_ty loc)
-zonkInsts insts = mapNF_Tc zonkInst insts
+zonkInsts insts = mappM zonkInst insts
\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]
+pprDictsTheta :: [Inst] -> SDoc
+-- Print in type-like fashion (Eq a, Show b)
+pprDictsTheta dicts = pprTheta (map dictPred dicts)
+
+pprDictsInFull :: [Inst] -> SDoc
+-- Print in type-like fashion, but with source location
+pprDictsInFull dicts
+ = vcat (map go dicts)
+ where
+ go dict = sep [quotes (ppr (dictPred dict)), nest 2 (pprInstLoc (instLoc dict))]
+
+pprInsts :: [Inst] -> SDoc
+-- Debugging: print the evidence :: type
+pprInsts insts = brackets (interpp'SP insts)
-pprInst (Dict u pred loc) = pprPred pred <+> show_uniq u
+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 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) -}]
+pprInst m@(Method inst_id id tys theta loc)
+ = ppr inst_id <+> dcolon <+>
+ braces (sep [ppr id <+> ptext SLIT("at"),
+ brackets (sep (map pprParendType tys))])
-show_uniq u = ifPprDebug (text "{-" <> ppr u <> text "-}")
+pprInstInFull inst
+ = sep [quotes (pprInst inst), nest 2 (pprInstLoc (instLoc inst))]
tidyInst :: TidyEnv -> Inst -> Inst
-tidyInst env (LitInst u lit ty loc) = LitInst u lit (tidyType env ty) loc
-tidyInst env (Dict u pred loc) = Dict u (tidyPred env pred) loc
-tidyInst env (Method u id tys theta tau loc) = Method u id (tidyTypes env tys) theta tau loc
+tidyInst env (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 loc) = Method u id (tidyTypes env tys) theta loc
tidyMoreInsts :: TidyEnv -> [Inst] -> (TidyEnv, [Inst])
-- This function doesn't assume that the tyvars are in scope
tidyInsts :: [Inst] -> (TidyEnv, [Inst])
tidyInsts insts = tidyMoreInsts emptyTidyEnv insts
+
+showLIE :: SDoc -> TcM () -- Debugging
+showLIE str
+ = do { lie_var <- getLIEVar ;
+ lie <- readMutVar lie_var ;
+ traceTc (str <+> vcat (map pprInstInFull (lieToList lie))) }
\end{code}
%************************************************************************
%* *
+ Extending the instance environment
+%* *
+%************************************************************************
+
+\begin{code}
+tcExtendLocalInstEnv :: [Instance] -> TcM a -> TcM a
+ -- Add new locally-defined instances
+tcExtendLocalInstEnv dfuns thing_inside
+ = do { traceDFuns dfuns
+ ; env <- getGblEnv
+ ; inst_env' <- foldlM addLocalInst (tcg_inst_env env) dfuns
+ ; let env' = env { tcg_insts = dfuns ++ tcg_insts env,
+ tcg_inst_env = inst_env' }
+ ; setGblEnv env' thing_inside }
+
+addLocalInst :: InstEnv -> Instance -> TcM InstEnv
+-- Check that the proposed new instance is OK,
+-- and then add it to the home inst env
+addLocalInst home_ie ispec
+ = 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 tcInstSkolType because we don't want to allocate fresh
+ -- *meta* type variables.
+ let dfun = instanceDFunId ispec
+ ; (tvs', theta', tau') <- tcInstSkolType (InstSkol dfun) (idType dfun)
+ ; let (cls, tys') = tcSplitDFunHead tau'
+ dfun' = setIdType dfun (mkSigmaTy tvs' theta' tau')
+ ispec' = setInstanceDFunId ispec dfun'
+
+ -- Load imported instances, so that we report
+ -- duplicates correctly
+ ; eps <- getEps
+ ; let inst_envs = (eps_inst_env eps, home_ie)
+
+ -- Check functional dependencies
+ ; case checkFunDeps inst_envs ispec' of
+ Just specs -> funDepErr ispec' specs
+ Nothing -> return ()
+
+ -- Check for duplicate instance decls
+ ; let { (matches, _) = lookupInstEnv inst_envs cls tys'
+ ; dup_ispecs = [ dup_ispec
+ | (_, dup_ispec) <- matches
+ , let (_,_,_,dup_tys) = instanceHead dup_ispec
+ , isJust (tcMatchTys (mkVarSet tvs') tys' dup_tys)] }
+ -- Find memebers of the match list which ispec itself matches.
+ -- If the match is 2-way, it's a duplicate
+ ; case dup_ispecs of
+ dup_ispec : _ -> dupInstErr ispec' dup_ispec
+ [] -> return ()
+
+ -- OK, now extend the envt
+ ; return (extendInstEnv home_ie ispec') }
+
+getOverlapFlag :: TcM OverlapFlag
+getOverlapFlag
+ = do { dflags <- getDOpts
+ ; let overlap_ok = dopt Opt_AllowOverlappingInstances dflags
+ incoherent_ok = dopt Opt_AllowIncoherentInstances dflags
+ overlap_flag | incoherent_ok = Incoherent
+ | overlap_ok = OverlapOk
+ | otherwise = NoOverlap
+
+ ; return overlap_flag }
+
+traceDFuns ispecs
+ = traceTc (hang (text "Adding instances:") 2 (vcat (map pp ispecs)))
+ where
+ pp ispec = ppr (instanceDFunId ispec) <+> colon <+> ppr ispec
+ -- Print the dfun name itself too
+
+funDepErr ispec ispecs
+ = addDictLoc ispec $
+ addErr (hang (ptext SLIT("Functional dependencies conflict between instance declarations:"))
+ 2 (pprInstances (ispec:ispecs)))
+dupInstErr ispec dup_ispec
+ = addDictLoc ispec $
+ addErr (hang (ptext SLIT("Duplicate instance declarations:"))
+ 2 (pprInstances [ispec, dup_ispec]))
+
+addDictLoc ispec thing_inside
+ = setSrcSpan (mkSrcSpan loc loc) thing_inside
+ where
+ loc = getSrcLoc ispec
+\end{code}
+
+
+%************************************************************************
+%* *
\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
+ | SimpleInst (LHsExpr TcId) -- Just a variable, type application, or literal
+ | GenInst [Inst] (LHsExpr TcId) -- The expression and its needed insts
-lookupInst :: Inst
- -> NF_TcM (LookupInstResult s)
+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
--- Dictionaries
-
-lookupInst dict@(Dict _ (ClassP clas tys) loc)
- = getDOptsTc `thenNF_Tc` \ dflags ->
- tcGetInstEnv `thenNF_Tc` \ 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.
- let
- (tyvars, rho) = tcSplitForAllTys (idType dfun_id)
- mk_ty_arg tv = case lookupSubstEnv tenv tv of
- Just (DoneTy ty) -> returnNF_Tc ty
- Nothing -> tcInstTyVar VanillaTv tv `thenNF_Tc` \ tc_tv ->
- returnTc (mkTyVarTy tc_tv)
- in
- mapNF_Tc mk_ty_arg tyvars `thenNF_Tc` \ ty_args ->
- let
- dfun_rho = substTy (mkTyVarSubst tyvars ty_args) rho
- (theta, _) = tcSplitPhiTy dfun_rho
- ty_app = mkHsTyApp (HsVar dfun_id) ty_args
- in
- if null theta then
- returnNF_Tc (SimpleInst ty_app)
- else
- newDictsAtLoc loc theta `thenNF_Tc` \ dicts ->
- let
- rhs = mkHsDictApp ty_app (map instToId dicts)
- 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 ->
- returnNF_Tc (GenInst dicts (mkHsDictApp (mkHsTyApp (HsVar id) tys) (map instToId dicts)))
+lookupInst inst@(Method _ id tys theta loc)
+ = newDictsAtLoc loc theta `thenM` \ dicts ->
+ returnM (GenInst dicts (mkHsDictApp (mkHsTyApp (L span (HsVar id)) tys) (map instToId dicts)))
+ where
+ span = instLocSrcSpan loc
-- Literals
-- 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).
+-- 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 lit ty loc)
- | Just expr <- shortCutLit lit ty
- = returnNF_Tc (GenInst [] expr) -- GenInst, not SimpleInst, because
+lookupInst inst@(LitInst _nm (HsIntegral i from_integer_name) ty loc)
+ | Just expr <- shortCutIntLit i ty
+ = returnM (GenInst [] (noLoc expr)) -- GenInst, not SimpleInst, because
-- expr may be a constructor application
+ | otherwise
+ = ASSERT( from_integer_name `isHsVar` 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 [] (noLoc expr))
-lookupInst inst@(LitInst u (HsIntegral i from_integer_name) ty loc)
- = tcLookupId from_integer_name `thenNF_Tc` \ from_integer ->
- newMethodAtLoc loc from_integer [ty] `thenNF_Tc` \ (method_inst, method_id) ->
- returnNF_Tc (GenInst [method_inst]
- (HsApp (HsVar method_id) (HsLit (HsInteger i))))
-
+ | otherwise
+ = ASSERT( from_rat_name `isHsVar` 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))
-lookupInst inst@(LitInst u (HsFractional f from_rat_name) ty loc)
- = tcLookupId from_rat_name `thenNF_Tc` \ from_rational ->
- newMethodAtLoc loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) ->
- let
- rational_ty = tcFunArgTy (idType method_id)
- rational_lit = HsLit (HsRat f rational_ty)
- in
- returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) rational_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 { eps <- getEps
+ ; tcg_env <- getGblEnv
+ ; let inst_envs = (eps_inst_env eps, tcg_inst_env tcg_env)
+ ; case lookupInstEnv inst_envs clas tys of {
+ ([(tenv, ispec)], [])
+ -> do { let dfun_id = is_dfun ispec
+ ; 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 { gbl <- getGblEnv
+ ; let dfun_name = idName dfun_id
+ dfun_mod = nameModule dfun_name
+ ; if isInternalName dfun_name || -- Internal name => defined in this module
+ not (isHomeModule (tcg_home_mods gbl) 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}
-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.
+
+
+%************************************************************************
+%* *
+ Re-mappable syntax
+%* *
+%************************************************************************
+
+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:
+
+ (>>) :: HB m n mn => m a -> n b -> mn b
+
+So the idea is to generate a local binding for (>>), thus:
+
+ 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}
-lookupSimpleInst :: Class
- -> [Type] -- Look up (c,t)
- -> NF_TcM (Maybe ThetaType) -- Here are the needed (c,t)s
-
-lookupSimpleInst clas tys
- = getDOptsTc `thenNF_Tc` \ dflags ->
- tcGetInstEnv `thenNF_Tc` \ inst_env ->
- case lookupInstEnv dflags inst_env clas tys of
- FoundInst tenv dfun
- -> returnNF_Tc (Just (substTheta (mkSubst emptyInScopeSet tenv) theta))
- where
- (_, rho) = tcSplitForAllTys (idType dfun)
- (theta,_) = tcSplitPhiTy rho
-
- 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)
+-- *** NOW USED ONLY FOR CmdTop (sigh) ***
+-- 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
+ = newMethodFromName orig ty std_nm `thenM` \ id ->
+ returnM (std_nm, HsVar id)
+
+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 ->
+ tcPolyExpr (L span user_nm_expr) sigma1 `thenM` \ expr ->
+ returnM (std_nm, unLoc expr)
+
+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