The @Inst@ type: dictionaries or method instances
\begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
module Inst (
Inst,
lookupSimpleInst, LookupInstResult(..),
tcExtendLocalInstEnv, tcGetInstEnvs, getOverlapFlag,
+ isAbstractableInst, isEqInst,
isDict, isClassDict, isMethod, isImplicInst,
isIPDict, isInheritableInst, isMethodOrLit,
isTyVarDict, isMethodFor,
zonkInst, zonkInsts,
- instToId, instToVar, instName,
+ instToId, instToVar, instType, instName, instToDictBind,
+ addInstToDictBind,
+
+ InstOrigin(..), InstLoc, pprInstLoc,
- InstOrigin(..), InstLoc, pprInstLoc
+ mkWantedCo, mkGivenCo,
+ fromWantedCo, fromGivenCo,
+ eitherEqInst, mkEqInst, mkEqInsts, mkWantedEqInst,
+ finalizeEqInst, writeWantedCoercion,
+ eqInstType, updateEqInstCoercion,
+ eqInstCoercion, eqInstTys
) where
#include "HsVersions.h"
import {-# SOURCE #-} TcExpr( tcPolyExpr )
-import {-# SOURCE #-} TcUnify( unifyType )
+import {-# SOURCE #-} TcUnify( boxyUnify, unifyType )
-import FastString(FastString)
+import FastString
import HsSyn
import TcHsSyn
import TcRnMonad
import TcMType
import TcType
import Type
+import TypeRep
+import Class
import Unify
import Module
import Coercion
import BasicTypes
import SrcLoc
import DynFlags
+import Bag
import Maybes
import Util
+import Unique
import Outputable
-
import Data.List
+import TypeRep
+import Class
+
+import Control.Monad
\end{code}
~~~~~~~~~
\begin{code}
instName :: Inst -> Name
+instName (EqInst {tci_name = name}) = name
instName inst = Var.varName (instToVar inst)
instToId :: Inst -> TcId
-instToId inst = ASSERT2( isId id, ppr inst ) id
+instToId inst = WARN( not (isId id), ppr inst )
+ id
where
id = instToVar inst
instToVar (ImplicInst {tci_name = nm, tci_tyvars = tvs, tci_given = givens,
tci_wanted = wanteds})
= mkLocalId nm (mkImplicTy tvs givens wanteds)
+instToVar i@(EqInst {})
+ = eitherEqInst i id (\(TyVarTy covar) -> covar)
instType :: Inst -> Type
-instType (LitInst {tci_ty = ty}) = ty
-instType (Method {tci_id = id}) = idType id
+instType (LitInst {tci_ty = ty}) = ty
+instType (Method {tci_id = id}) = idType id
instType (Dict {tci_pred = pred}) = mkPredTy pred
instType imp@(ImplicInst {}) = mkImplicTy (tci_tyvars imp) (tci_given imp)
(tci_wanted imp)
+-- instType i@(EqInst {tci_co = co}) = eitherEqInst i TyVarTy id
+instType (EqInst {tci_left = ty1, tci_right = ty2}) = mkPredTy (EqPred ty1 ty2)
mkImplicTy tvs givens wanteds -- The type of an implication constraint
- = ASSERT( all isDict givens )
+ = ASSERT( all isAbstractableInst givens )
-- pprTrace "mkImplicTy" (ppr givens) $
- mkForAllTys tvs $
- mkPhiTy (map dictPred givens) $
- if isSingleton wanteds then
- instType (head wanteds)
- else
- mkTupleTy Boxed (length wanteds) (map instType wanteds)
+ -- See [Equational Constraints in Implication Constraints]
+ let dict_wanteds = filter (not . isEqInst) wanteds
+ in
+ mkForAllTys tvs $
+ mkPhiTy (map dictPred givens) $
+ if isSingleton dict_wanteds then
+ instType (head dict_wanteds)
+ else
+ mkTupleTy Boxed (length dict_wanteds) (map instType dict_wanteds)
dictPred (Dict {tci_pred = pred}) = pred
+dictPred (EqInst {tci_left=ty1,tci_right=ty2}) = EqPred ty1 ty2
dictPred inst = pprPanic "dictPred" (ppr inst)
getDictClassTys (Dict {tci_pred = pred}) = getClassPredTys pred
fdPredsOfInst (ImplicInst {tci_given = gs,
tci_wanted = ws}) = fdPredsOfInsts (gs ++ ws)
fdPredsOfInst (LitInst {}) = []
+fdPredsOfInst (EqInst {}) = []
fdPredsOfInsts :: [Inst] -> [PredType]
fdPredsOfInsts insts = concatMap fdPredsOfInst insts
`minusVarSet` mkVarSet tvs
`unionVarSet` unionVarSets (map varTypeTyVars tvs)
-- Remember the free tyvars of a coercion
+tyVarsOfInst (EqInst {tci_left = ty1, tci_right = ty2}) = tyVarsOfType ty1 `unionVarSet` tyVarsOfType ty2
tyVarsOfInsts insts = foldr (unionVarSet . tyVarsOfInst) emptyVarSet insts
tyVarsOfLIE lie = tyVarsOfInsts (lieToList lie)
+
+
+--------------------------
+instToDictBind :: Inst -> LHsExpr TcId -> TcDictBinds
+instToDictBind inst rhs
+ = unitBag (L (instSpan inst) (VarBind (instToId inst) rhs))
+
+addInstToDictBind :: TcDictBinds -> Inst -> LHsExpr TcId -> TcDictBinds
+addInstToDictBind binds inst rhs = binds `unionBags` instToDictBind inst rhs
\end{code}
Predicates
~~~~~~~~~~
\begin{code}
+
+isAbstractableInst :: Inst -> Bool
+isAbstractableInst inst = isDict inst || isEqInst inst
+
+isEqInst :: Inst -> Bool
+isEqInst (EqInst {}) = True
+isEqInst other = False
+
isDict :: Inst -> Bool
isDict (Dict {}) = True
isDict other = False
newDictBndrs inst_loc theta = mapM (newDictBndr inst_loc) theta
newDictBndr :: InstLoc -> TcPredType -> TcM Inst
+newDictBndr inst_loc pred@(EqPred ty1 ty2)
+ = do { uniq <- newUnique
+ ; let name = mkPredName uniq inst_loc pred
+ ; return (EqInst {tci_name = name,
+ tci_loc = inst_loc,
+ tci_left = ty1,
+ tci_right = ty2,
+ tci_co = mkGivenCo $ TyVarTy (Var.mkCoVar name (PredTy pred))})
+ }
newDictBndr inst_loc pred
= do { uniq <- newUnique
; let name = mkPredName uniq inst_loc pred
-- (instCall o tys theta)
-- (a) Makes fresh dictionaries as necessary for the constraints (theta)
-- (b) Throws these dictionaries into the LIE
--- (c) Eeturns an HsWrapper ([.] tys dicts)
+-- (c) Returns an HsWrapper ([.] tys dicts)
instCall orig tys theta
= do { loc <- getInstLoc orig
- ; (dicts, dict_app) <- instCallDicts loc theta
- ; extendLIEs dicts
+ ; dict_app <- instCallDicts loc theta
; return (dict_app <.> mkWpTyApps tys) }
----------------
-- Used exclusively for the 'stupid theta' of a data constructor
instStupidTheta orig theta
= do { loc <- getInstLoc orig
- ; (dicts, _) <- instCallDicts loc theta
- ; extendLIEs dicts }
+ ; _co <- instCallDicts loc theta -- Discard the coercion
+ ; return () }
----------------
-instCallDicts :: InstLoc -> TcThetaType -> TcM ([Inst], HsWrapper)
+instCallDicts :: InstLoc -> TcThetaType -> TcM HsWrapper
+-- Instantiates the TcTheta, puts all constraints thereby generated
+-- into the LIE, and returns a HsWrapper to enclose the call site.
-- This is the key place where equality predicates
-- are unleashed into the world
-instCallDicts loc [] = return ([], idHsWrapper)
+instCallDicts loc [] = return idHsWrapper
+
+-- instCallDicts loc (EqPred ty1 ty2 : preds)
+-- = do { unifyType ty1 ty2 -- For now, we insist that they unify right away
+-- -- Later on, when we do associated types,
+-- -- unifyType :: Type -> Type -> TcM ([Inst], Coercion)
+-- ; (dicts, co_fn) <- instCallDicts loc preds
+-- ; return (dicts, co_fn <.> WpTyApp ty1) }
+-- -- We use type application to apply the function to the
+-- -- coercion; here ty1 *is* the appropriate identity coercion
instCallDicts loc (EqPred ty1 ty2 : preds)
- = do { unifyType ty1 ty2 -- For now, we insist that they unify right away
- -- Later on, when we do associated types,
- -- unifyType :: Type -> Type -> TcM ([Inst], Coercion)
- ; (dicts, co_fn) <- instCallDicts loc preds
- ; return (dicts, co_fn <.> WpTyApp ty1) }
- -- We use type application to apply the function to the
- -- coercion; here ty1 *is* the appropriate identity coercion
+ = do { traceTc (text "instCallDicts" <+> ppr (EqPred ty1 ty2))
+ ; coi <- boxyUnify ty1 ty2
+-- ; coi <- unifyType ty1 ty2
+ ; let co = fromCoI coi ty1
+ ; co_fn <- instCallDicts loc preds
+ ; return (co_fn <.> WpTyApp co) }
instCallDicts loc (pred : preds)
= do { uniq <- newUnique
; let name = mkPredName uniq loc pred
dict = Dict {tci_name = name, tci_pred = pred, tci_loc = loc}
- ; (dicts, co_fn) <- instCallDicts loc preds
- ; return (dict:dicts, co_fn <.> WpApp (instToId dict)) }
+ ; extendLIE dict
+ ; co_fn <- instCallDicts loc preds
+ ; return (co_fn <.> WpApp (instToId dict)) }
-------------
cloneDict :: Inst -> TcM Inst
cloneDict dict@(Dict nm ty loc) = do { uniq <- newUnique
; return (dict {tci_name = setNameUnique nm uniq}) }
+cloneDict eq@(EqInst {}) = return eq
cloneDict other = pprPanic "cloneDict" (ppr other)
-- For vanilla implicit parameters, there is only one in scope
-- scope, so we make up a new namea.
newIPDict :: InstOrigin -> IPName Name -> Type
-> TcM (IPName Id, Inst)
-newIPDict orig ip_name ty
- = getInstLoc orig `thenM` \ inst_loc ->
- newUnique `thenM` \ uniq ->
+newIPDict orig ip_name ty = do
+ inst_loc <- getInstLoc orig
+ uniq <- newUnique
let
pred = IParam ip_name ty
name = mkPredName uniq inst_loc pred
dict = Dict {tci_name = name, tci_pred = pred, tci_loc = inst_loc}
- in
- returnM (mapIPName (\n -> instToId dict) ip_name, dict)
+
+ return (mapIPName (\n -> instToId dict) ip_name, dict)
\end{code}
\begin{code}
newMethodFromName :: InstOrigin -> BoxyRhoType -> Name -> TcM TcId
-newMethodFromName origin ty name
- = tcLookupId name `thenM` \ id ->
+newMethodFromName origin ty name = do
+ id <- tcLookupId name
-- 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)
+ loc <- getInstLoc origin
+ inst <- tcInstClassOp loc id [ty]
+ extendLIE inst
+ return (instToId inst)
-newMethodWithGivenTy orig id tys
- = getInstLoc orig `thenM` \ loc ->
- newMethod loc id tys `thenM` \ inst ->
- extendLIE inst `thenM_`
- returnM (instToId inst)
+newMethodWithGivenTy orig id tys = do
+ loc <- getInstLoc orig
+ inst <- newMethod loc id tys
+ extendLIE inst
+ return (instToId inst)
--------------------------------------------
-- tcInstClassOp, and newMethod do *not* drop the
-- 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
+tcInstClassOp inst_loc sel_id tys = do
+ let
(tyvars, _rho) = tcSplitForAllTys (idType sel_id)
- in
- zipWithM_ checkKind tyvars tys `thenM_`
+ zipWithM_ checkKind tyvars tys
newMethod inst_loc sel_id tys
checkKind :: TyVar -> TcType -> TcM ()
---------------------------
-newMethod inst_loc id tys
- = newUnique `thenM` \ new_uniq ->
+newMethod inst_loc id tys = do
+ new_uniq <- newUnique
let
(theta,tau) = tcSplitPhiTy (applyTys (idType id) tys)
meth_id = mkUserLocal (mkMethodOcc (getOccName id)) new_uniq tau loc
inst = Method {tci_id = meth_id, tci_oid = id, tci_tys = tys,
tci_theta = theta, tci_loc = inst_loc}
loc = instLocSpan inst_loc
- in
- returnM inst
+
+ return inst
\end{code}
\begin{code}
shortCutIntLit :: Integer -> TcType -> Maybe (HsExpr TcId)
shortCutIntLit i ty
- | isIntTy ty && inIntRange i -- Short cut for Int
- = Just (HsLit (HsInt i))
- | isIntegerTy ty -- Short cut for Integer
- = Just (HsLit (HsInteger i ty))
- | otherwise = Nothing
+ | isIntTy ty && inIntRange i = Just (HsLit (HsInt i))
+ | isIntegerTy ty = Just (HsLit (HsInteger i ty))
+ | otherwise = shortCutFracLit (fromInteger i) ty
+ -- The 'otherwise' case is important
+ -- Consider (3 :: Float). Syntactically it looks like an IntLit,
+ -- so we'll call shortCutIntLit, but of course it's a float
+ -- This can make a big difference for programs with a lot of
+ -- literals, compiled without -O
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
+ | 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)
| 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))
+mkIntegerLit i = do
+ integer_ty <- tcMetaTy integerTyConName
+ span <- getSrcSpanM
+ return (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))
+mkRatLit r = do
+ rat_ty <- tcMetaTy rationalTyConName
+ span <- getSrcSpanM
+ return (L span $ HsLit (HsRat r rat_ty))
mkStrLit :: FastString -> TcM (LHsExpr TcId)
-mkStrLit s
- = --tcMetaTy stringTyConName `thenM` \ string_ty ->
- getSrcSpanM `thenM` \ span ->
- returnM (L span $ HsLit (HsString s))
+mkStrLit s = do
+ --string_ty <- tcMetaTy stringTyConName
+ span <- getSrcSpanM
+ return (L span $ HsLit (HsString s))
isHsVar :: HsExpr Name -> Name -> Bool
isHsVar (HsVar f) g = f==g
\begin{code}
zonkInst :: Inst -> TcM Inst
-zonkInst dict@(Dict { tci_pred = pred})
- = zonkTcPredType pred `thenM` \ new_pred ->
- returnM (dict {tci_pred = new_pred})
+zonkInst dict@(Dict { tci_pred = pred}) = do
+ new_pred <- zonkTcPredType pred
+ return (dict {tci_pred = new_pred})
-zonkInst meth@(Method {tci_oid = id, tci_tys = tys, tci_theta = theta})
- = zonkId id `thenM` \ new_id ->
+zonkInst meth@(Method {tci_oid = id, tci_tys = tys, tci_theta = theta}) = do
+ new_id <- zonkId id
-- Essential to zonk the id in case it's a local variable
-- Can't use zonkIdOcc because the id might itself be
-- an InstId, in which case it won't be in scope
- zonkTcTypes tys `thenM` \ new_tys ->
- zonkTcThetaType theta `thenM` \ new_theta ->
- returnM (meth { tci_oid = new_id, tci_tys = new_tys, tci_theta = new_theta })
+ new_tys <- zonkTcTypes tys
+ new_theta <- zonkTcThetaType theta
+ return (meth { tci_oid = new_id, tci_tys = new_tys, tci_theta = new_theta })
-- No need to zonk the tci_id
-zonkInst lit@(LitInst {tci_ty = ty})
- = zonkTcType ty `thenM` \ new_ty ->
- returnM (lit {tci_ty = new_ty})
+zonkInst lit@(LitInst {tci_ty = ty}) = do
+ new_ty <- zonkTcType ty
+ return (lit {tci_ty = new_ty})
zonkInst implic@(ImplicInst {})
= ASSERT( all isImmutableTyVar (tci_tyvars implic) )
; wanteds' <- zonkInsts (tci_wanted implic)
; return (implic {tci_given = givens',tci_wanted = wanteds'}) }
-zonkInsts insts = mappM zonkInst insts
+zonkInst eqinst@(EqInst {tci_left = ty1, tci_right = ty2})
+ = do { co' <- eitherEqInst eqinst
+ (\covar -> return (mkWantedCo covar))
+ (\co -> liftM mkGivenCo $ zonkTcType co)
+ ; ty1' <- zonkTcType ty1
+ ; ty2' <- zonkTcType ty2
+ ; return (eqinst {tci_co = co', tci_left= ty1', tci_right = ty2' })
+ }
+
+zonkInsts insts = mapM zonkInst insts
\end{code}
pprInst, pprInstInFull :: Inst -> SDoc
-- Debugging: print the evidence :: type
-pprInst inst = ppr (instName inst) <+> dcolon
- <+> (braces (ppr (instType inst)) $$
- ifPprDebug implic_stuff)
+pprInst i@(EqInst {tci_left = ty1, tci_right = ty2, tci_co = co})
+ = eitherEqInst i
+ (\covar -> text "Wanted" <+> ppr (TyVarTy covar) <+> dcolon <+> ppr (EqPred ty1 ty2))
+ (\co -> text "Given" <+> ppr co <+> dcolon <+> ppr (EqPred ty1 ty2))
+pprInst inst = ppr name <> braces (pprUnique (getUnique name)) <+> dcolon
+ <+> braces (ppr (instType inst) <> implicWantedEqs)
where
- implic_stuff | isImplicInst inst = ppr (tci_reft inst)
- | otherwise = empty
+ name = instName inst
+ implicWantedEqs
+ | isImplicInst inst = text " &" <+>
+ ppr (filter isEqInst (tci_wanted inst))
+ | otherwise = empty
+pprInstInFull inst@(EqInst {}) = pprInst inst
pprInstInFull inst = sep [quotes (pprInst inst), nest 2 (pprInstArising inst)]
tidyInst :: TidyEnv -> Inst -> Inst
+tidyInst env eq@(EqInst {tci_left = lty, tci_right = rty, tci_co = co}) =
+ eq { tci_left = tidyType env lty
+ , tci_right = tidyType env rty
+ , tci_co = either Left (Right . tidyType env) co
+ }
tidyInst env lit@(LitInst {tci_ty = ty}) = lit {tci_ty = tidyType env ty}
tidyInst env dict@(Dict {tci_pred = pred}) = dict {tci_pred = tidyPred env pred}
tidyInst env meth@(Method {tci_tys = tys}) = meth {tci_tys = tidyTypes env tys}
getOverlapFlag :: TcM OverlapFlag
getOverlapFlag
= do { dflags <- getDOpts
- ; let overlap_ok = dopt Opt_AllowOverlappingInstances dflags
- incoherent_ok = dopt Opt_AllowIncoherentInstances dflags
+ ; let overlap_ok = dopt Opt_OverlappingInstances dflags
+ incoherent_ok = dopt Opt_IncoherentInstances dflags
overlap_flag | incoherent_ok = Incoherent
| overlap_ok = OverlapOk
| otherwise = NoOverlap
-- the LIE. Instead, any Insts needed by the lookup are returned in
-- the LookupInstResult, where they can be further processed by tcSimplify
+lookupSimpleInst (EqInst {}) = return NoInstance
+
--------------------- Implications ------------------------
lookupSimpleInst (ImplicInst {}) = return NoInstance
--------------------- Methods ------------------------
lookupSimpleInst (Method {tci_oid = id, tci_tys = tys, tci_theta = theta, tci_loc = loc})
- = do { (dicts, dict_app) <- instCallDicts loc theta
+ = do { (dict_app, dicts) <- getLIE $ instCallDicts loc theta
; let co_fn = dict_app <.> mkWpTyApps tys
; return (GenInst dicts (L span $ HsWrap co_fn (HsVar id))) }
where
-- [Same shortcut as in newOverloadedLit, but we
-- may have done some unification by now]
-lookupSimpleInst (LitInst {tci_lit = HsIntegral i from_integer_name, tci_ty = ty, tci_loc = loc})
+lookupSimpleInst (LitInst {tci_lit = HsIntegral i from_integer_name _, tci_ty = ty, tci_loc = loc})
| Just expr <- shortCutIntLit i ty
- = returnM (GenInst [] (noLoc expr))
+ = return (GenInst [] (noLoc expr))
| 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]
+ = ASSERT( from_integer_name `isHsVar` fromIntegerName ) do -- A LitInst invariant
+ from_integer <- tcLookupId fromIntegerName
+ method_inst <- tcInstClassOp loc from_integer [ty]
+ integer_lit <- mkIntegerLit i
+ return (GenInst [method_inst]
(mkHsApp (L (instLocSpan loc)
(HsVar (instToId method_inst))) integer_lit))
-lookupSimpleInst (LitInst {tci_lit = HsFractional f from_rat_name, tci_ty = ty, tci_loc = loc})
+lookupSimpleInst (LitInst {tci_lit = HsFractional f from_rat_name _, tci_ty = ty, tci_loc = loc})
| Just expr <- shortCutFracLit f ty
- = returnM (GenInst [] (noLoc expr))
+ = return (GenInst [] (noLoc expr))
| 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 (instLocSpan loc)
+ = ASSERT( from_rat_name `isHsVar` fromRationalName ) do -- A LitInst invariant
+ from_rational <- tcLookupId fromRationalName
+ method_inst <- tcInstClassOp loc from_rational [ty]
+ rat_lit <- mkRatLit f
+ return (GenInst [method_inst] (mkHsApp (L (instLocSpan loc)
(HsVar (instToId method_inst))) rat_lit))
-lookupSimpleInst (LitInst {tci_lit = HsIsString s from_string_name, tci_ty = ty, tci_loc = loc})
+lookupSimpleInst (LitInst {tci_lit = HsIsString s from_string_name _, tci_ty = ty, tci_loc = loc})
| Just expr <- shortCutStringLit s ty
- = returnM (GenInst [] (noLoc expr))
+ = return (GenInst [] (noLoc expr))
| otherwise
- = ASSERT( from_string_name `isHsVar` fromStringName ) -- A LitInst invariant
- tcLookupId fromStringName `thenM` \ from_string ->
- tcInstClassOp loc from_string [ty] `thenM` \ method_inst ->
- mkStrLit s `thenM` \ string_lit ->
- returnM (GenInst [method_inst]
+ = ASSERT( from_string_name `isHsVar` fromStringName ) do -- A LitInst invariant
+ from_string <- tcLookupId fromStringName
+ method_inst <- tcInstClassOp loc from_string [ty]
+ string_lit <- mkStrLit s
+ return (GenInst [method_inst]
(mkHsApp (L (instLocSpan loc)
(HsVar (instToId method_inst))) string_lit))
; let inst_tv (Left tv) = do { tv' <- tcInstTyVar tv; return (mkTyVarTy tv') }
inst_tv (Right ty) = return ty
- ; tys <- mappM inst_tv mb_inst_tys
+ ; tys <- mapM inst_tv mb_inst_tys
; let
(theta, _) = tcSplitPhiTy (applyTys (idType dfun_id) tys)
src_loc = instLocSpan loc
dfun = HsVar dfun_id
; if null theta then
- returnM (GenInst [] (L src_loc $ HsWrap (mkWpTyApps tys) dfun))
+ return (GenInst [] (L src_loc $ HsWrap (mkWpTyApps tys) dfun))
else do
- { (dicts, dict_app) <- instCallDicts loc theta
+ { (dict_app, dicts) <- getLIE $ instCallDicts loc theta -- !!!
; let co_fn = dict_app <.> mkWpTyApps tys
- ; returnM (GenInst dicts (L src_loc $ HsWrap co_fn dfun))
+ ; return (GenInst dicts (L src_loc $ HsWrap co_fn dfun))
}}}}
---------------
tcSyntaxName orig ty (std_nm, HsVar user_nm)
| std_nm == user_nm
- = newMethodFromName orig ty std_nm `thenM` \ id ->
- returnM (std_nm, HsVar id)
+ = do id <- newMethodFromName orig ty std_nm
+ return (std_nm, HsVar id)
-tcSyntaxName orig ty (std_nm, user_nm_expr)
- = tcLookupId std_nm `thenM` \ std_id ->
+tcSyntaxName orig ty (std_nm, user_nm_expr) = do
+ std_id <- tcLookupId std_nm
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) $
+
+ addErrCtxtM (syntaxNameCtxt user_nm_expr orig sigma1) $ do
-- 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)
+ span <- getSrcSpanM
+ expr <- tcPolyExpr (L span user_nm_expr) sigma1
+ return (std_nm, unLoc expr)
-syntaxNameCtxt name orig ty tidy_env
- = getInstLoc orig `thenM` \ inst_loc ->
+syntaxNameCtxt name orig ty tidy_env = do
+ inst_loc <- getInstLoc orig
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 (ptext SLIT("arising from") <+> pprInstLoc inst_loc)]
- in
- returnM (tidy_env, msg)
+
+ return (tidy_env, msg)
+\end{code}
+
+%************************************************************************
+%* *
+ EqInsts
+%* *
+%************************************************************************
+
+\begin{code}
+mkGivenCo :: Coercion -> Either TcTyVar Coercion
+mkGivenCo = Right
+
+mkWantedCo :: TcTyVar -> Either TcTyVar Coercion
+mkWantedCo = Left
+
+fromGivenCo :: Either TcTyVar Coercion -> Coercion
+fromGivenCo (Right co) = co
+fromGivenCo _ = panic "fromGivenCo: not a wanted coercion"
+
+fromWantedCo :: String -> Either TcTyVar Coercion -> TcTyVar
+fromWantedCo _ (Left covar) = covar
+fromWantedCo msg _ = panic ("fromWantedCo: not a wanted coercion: " ++ msg)
+
+eitherEqInst :: Inst -- given or wanted EqInst
+ -> (TcTyVar -> a) -- result if wanted
+ -> (Coercion -> a) -- result if given
+ -> a
+eitherEqInst (EqInst {tci_co = either_co}) withWanted withGiven
+ = case either_co of
+ Left covar -> withWanted covar
+ Right co -> withGiven co
+
+mkEqInsts :: [PredType] -> [Either TcTyVar Coercion] -> TcM [Inst]
+mkEqInsts preds cos = zipWithM mkEqInst preds cos
+
+mkEqInst :: PredType -> Either TcTyVar Coercion -> TcM Inst
+mkEqInst (EqPred ty1 ty2) co
+ = do { uniq <- newUnique
+ ; src_span <- getSrcSpanM
+ ; err_ctxt <- getErrCtxt
+ ; let loc = InstLoc EqOrigin src_span err_ctxt
+ name = mkName uniq src_span
+ inst = EqInst {tci_left = ty1, tci_right = ty2, tci_co = co, tci_loc = loc, tci_name = name}
+ ; return inst
+ }
+ where mkName uniq src_span = mkInternalName uniq (mkVarOcc "co") src_span
+
+mkWantedEqInst :: PredType -> TcM Inst
+mkWantedEqInst pred@(EqPred ty1 ty2)
+ = do { cotv <- newMetaCoVar ty1 ty2
+ ; mkEqInst pred (Left cotv)
+ }
+
+-- type inference:
+-- We want to promote the wanted EqInst to a given EqInst
+-- in the signature context.
+-- This means we have to give the coercion a name
+-- and fill it in as its own name.
+finalizeEqInst
+ :: Inst -- wanted
+ -> TcM Inst -- given
+finalizeEqInst wanted@(EqInst {tci_left = ty1, tci_right = ty2, tci_name = name})
+ = do { let var = Var.mkCoVar name (PredTy $ EqPred ty1 ty2)
+ ; writeWantedCoercion wanted (TyVarTy var)
+ ; let given = wanted { tci_co = mkGivenCo $ TyVarTy var }
+ ; return given
+ }
+
+writeWantedCoercion
+ :: Inst -- wanted EqInst
+ -> Coercion -- coercion to fill the hole with
+ -> TcM ()
+writeWantedCoercion wanted co
+ = do { let cotv = fromWantedCo "writeWantedCoercion" $ tci_co wanted
+ ; writeMetaTyVar cotv co
+ }
+
+eqInstType :: Inst -> TcType
+eqInstType inst = eitherEqInst inst mkTyVarTy id
+
+eqInstCoercion :: Inst -> Either TcTyVar Coercion
+eqInstCoercion = tci_co
+
+eqInstTys :: Inst -> (TcType, TcType)
+eqInstTys inst = (tci_left inst, tci_right inst)
+
+updateEqInstCoercion :: (Either TcTyVar Coercion -> Either TcTyVar Coercion) -> Inst -> Inst
+updateEqInstCoercion f inst = inst {tci_co = f $ tci_co inst}
\end{code}
projects / ghc-hetmet.git / blobdiff