%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcExpr]{Typecheck an expression}
#ifdef GHCI /* Only if bootstrapped */
import {-# SOURCE #-} TcSplice( tcSpliceExpr, tcBracket )
-import HsSyn ( nlHsVar )
-import Id ( Id )
-import Name ( isExternalName )
-import TcType ( isTauTy )
-import TcEnv ( checkWellStaged )
-import HsSyn ( nlHsApp )
import qualified DsMeta
#endif
-import HsSyn ( HsExpr(..), LHsExpr, ArithSeqInfo(..), recBindFields,
- HsMatchContext(..), HsRecordBinds, mkHsCoerce,
- mkHsApp )
-import TcHsSyn ( hsLitType )
+import HsSyn
+import TcHsSyn
import TcRnMonad
-import TcUnify ( tcInfer, tcSubExp, tcFunResTy, tcGen, boxyUnify, subFunTys, zapToMonotype, stripBoxyType,
- boxySplitListTy, boxySplitTyConApp, wrapFunResCoercion, preSubType,
- unBox )
-import BasicTypes ( Arity, isMarkedStrict )
-import Inst ( newMethodFromName, newIPDict, instCall,
- newMethodWithGivenTy, instStupidTheta )
-import TcBinds ( tcLocalBinds )
-import TcEnv ( tcLookup, tcLookupDataCon, tcLookupField )
-import TcArrows ( tcProc )
-import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts, tcBody,
- TcMatchCtxt(..) )
-import TcHsType ( tcHsSigType, UserTypeCtxt(..) )
-import TcPat ( tcOverloadedLit, addDataConStupidTheta, badFieldCon )
-import TcMType ( tcInstTyVars, newFlexiTyVarTy, newBoxyTyVars,
- readFilledBox, zonkTcTypes )
-import TcType ( TcType, TcSigmaType, TcRhoType, TvSubst,
- BoxySigmaType, BoxyRhoType, ThetaType,
- mkTyVarTys, mkFunTys,
- tcMultiSplitSigmaTy, tcSplitFunTysN,
- tcSplitTyConApp_maybe,
- isSigmaTy, mkFunTy, mkTyConApp, isLinearPred,
- exactTyVarsOfType, exactTyVarsOfTypes,
- zipTopTvSubst, zipOpenTvSubst, substTys, substTyVar
- )
-import {- Kind parts of -}
- Type ( argTypeKind )
-
-import Id ( Id, idType, recordSelectorFieldLabel,
- isRecordSelector, isNaughtyRecordSelector,
- isDataConId_maybe )
-import DataCon ( DataCon, dataConFieldLabels, dataConStrictMarks,
- dataConSourceArity,
- dataConWrapId, isVanillaDataCon, dataConUnivTyVars,
- dataConOrigArgTys )
-import Name ( Name )
-import TyCon ( FieldLabel, tyConStupidTheta, tyConDataCons,
- isEnumerationTyCon )
-import Type ( substTheta, substTy )
-import Var ( TyVar, tyVarKind )
-import VarSet ( emptyVarSet, elemVarSet, unionVarSet )
-import TysWiredIn ( boolTy, parrTyCon, tupleTyCon )
-import PrelNames ( enumFromName, enumFromThenName,
- enumFromToName, enumFromThenToName,
- enumFromToPName, enumFromThenToPName, negateName,
- hasKey
- )
-import PrimOp ( tagToEnumKey )
-
+import TcUnify
+import BasicTypes
+import Inst
+import TcBinds
+import TcEnv
+import TcArrows
+import TcMatches
+import TcHsType
+import TcPat
+import TcMType
+import TcType
+import Id
+import DataCon
+import Name
+import TyCon
+import Type
+import Var
+import VarSet
+import TysWiredIn
+import PrelNames
+import PrimOp
import DynFlags
-import StaticFlags ( opt_NoMethodSharing )
-import HscTypes ( TyThing(..) )
-import SrcLoc ( Located(..), unLoc, getLoc )
+import StaticFlags
+import HscTypes
+import SrcLoc
import Util
-import ListSetOps ( assocMaybe )
-import Maybes ( catMaybes )
+import ListSetOps
+import Maybes
import Outputable
import FastString
-
-#ifdef DEBUG
-import TyCon ( tyConArity )
-#endif
\end{code}
%************************************************************************
tcPolyExprNC expr res_ty
| isSigmaTy res_ty
- = do { (gen_fn, expr') <- tcGen res_ty emptyVarSet (tcPolyExprNC expr)
+ = do { (gen_fn, expr') <- tcGen res_ty emptyVarSet (\_ -> tcPolyExprNC expr)
-- Note the recursive call to tcPolyExpr, because the
-- type may have multiple layers of for-alls
- ; return (L (getLoc expr') (mkHsCoerce gen_fn (unLoc expr'))) }
+ -- E.g. forall a. Eq a => forall b. Ord b => ....
+ ; return (mkLHsWrap gen_fn expr') }
| otherwise
= tcMonoExpr expr res_ty
tcExpr (HsSCC lbl expr) res_ty = do { expr' <- tcMonoExpr expr res_ty
; returnM (HsSCC lbl expr') }
+tcExpr (HsTickPragma info expr) res_ty
+ = do { expr' <- tcMonoExpr expr res_ty
+ ; returnM (HsTickPragma info expr') }
tcExpr (HsCoreAnn lbl expr) res_ty -- hdaume: core annotation
= do { expr' <- tcMonoExpr expr res_ty
; co_fn <- tcSubExp ip_ty res_ty
; (ip', inst) <- newIPDict (IPOccOrigin ip) ip ip_ty
; extendLIE inst
- ; return (mkHsCoerce co_fn (HsIPVar ip')) }
+ ; return (mkHsWrap co_fn (HsIPVar ip')) }
tcExpr (HsApp e1 e2) res_ty
= go e1 [e2]
tcExpr (HsLam match) res_ty
= do { (co_fn, match') <- tcMatchLambda match res_ty
- ; return (mkHsCoerce co_fn (HsLam match')) }
+ ; return (mkHsWrap co_fn (HsLam match')) }
tcExpr in_expr@(ExprWithTySig expr sig_ty) res_ty
= do { sig_tc_ty <- tcHsSigType ExprSigCtxt sig_ty
- ; expr' <- tcPolyExpr expr sig_tc_ty
+
+ -- Remember to extend the lexical type-variable environment
+ ; (gen_fn, expr') <- tcGen sig_tc_ty emptyVarSet (\ skol_tvs res_ty ->
+ tcExtendTyVarEnv2 (hsExplicitTvs sig_ty `zip` mkTyVarTys skol_tvs) $
+ tcPolyExprNC expr res_ty)
+
; co_fn <- tcSubExp sig_tc_ty res_ty
- ; return (mkHsCoerce co_fn (ExprWithTySigOut expr' sig_ty)) }
+ ; return (mkHsWrap co_fn (ExprWithTySigOut (mkLHsWrap gen_fn expr') sig_ty)) }
tcExpr (HsType ty) res_ty
= failWithTc (text "Can't handle type argument:" <+> ppr ty)
tcExpr in_expr@(SectionR lop@(L loc op) arg2) res_ty
= do { (co_fn, (op', arg2')) <- subFunTys doc 1 res_ty $ \ [arg1_ty'] res_ty' ->
tcApp op 2 (tc_args arg1_ty') res_ty'
- ; return (mkHsCoerce co_fn (SectionR (L loc op') arg2')) }
+ ; return (mkHsWrap co_fn (SectionR (L loc op') arg2')) }
where
doc = ptext SLIT("The section") <+> quotes (ppr in_expr)
<+> ptext SLIT("takes one argument")
- tc_args arg1_ty' [arg1_ty, arg2_ty]
- = do { boxyUnify arg1_ty' arg1_ty
- ; tcArg lop (arg2, arg2_ty, 2) }
- tc_args arg1_ty' other = panic "tcExpr SectionR"
+ tc_args arg1_ty' qtvs qtys [arg1_ty, arg2_ty]
+ = do { boxyUnify arg1_ty' (substTyWith qtvs qtys arg1_ty)
+ ; arg2' <- tcArg lop 2 arg2 qtvs qtys arg2_ty
+ ; qtys' <- mapM refineBox qtys -- c.f. tcArgs
+ ; return (qtys', arg2') }
+ tc_args arg1_ty' _ _ _ = panic "tcExpr SectionR"
\end{code}
\begin{code}
; checkMissingFields data_con rbinds
; let arity = dataConSourceArity data_con
- check_fields arg_tys
- = do { rbinds' <- tcRecordBinds data_con arg_tys rbinds
- ; mapM unBox arg_tys
- ; return rbinds' }
- -- The unBox ensures that all the boxes in arg_tys are indeed
+ check_fields qtvs qtys arg_tys
+ = do { let arg_tys' = substTys (zipOpenTvSubst qtvs qtys) arg_tys
+ ; rbinds' <- tcRecordBinds data_con arg_tys' rbinds
+ ; qtys' <- mapM refineBoxToTau qtys
+ ; return (qtys', rbinds') }
+ -- The refineBoxToTau ensures that all the boxes in arg_tys are indeed
-- filled, which is the invariant expected by tcIdApp
+ -- How could this not be the case? Consider a record construction
+ -- that does not mention all the fields.
; (con_expr, rbinds') <- tcIdApp con_name arity check_fields res_ty
instStupidTheta RecordUpdOrigin theta' `thenM_`
-- Phew!
- returnM (mkHsCoerce co_fn (RecordUpd record_expr' rbinds' record_ty result_record_ty))
+ returnM (mkHsWrap co_fn (RecordUpd record_expr' rbinds' record_ty result_record_ty))
\end{code}
---------------------------
tcApp :: HsExpr Name -- Function
-> Arity -- Number of args reqd
- -> ([BoxySigmaType] -> TcM arg_results) -- Argument type-checker
+ -> ArgChecker results
-> BoxyRhoType -- Result type
- -> TcM (HsExpr TcId, arg_results)
+ -> TcM (HsExpr TcId, results)
-- (tcFun fun n_args arg_checker res_ty)
-- The argument type checker, arg_checker, will be passed exactly n_args types
= tcIdApp fun_name n_args arg_checker res_ty
tcApp fun n_args arg_checker res_ty -- The vanilla case (rula APP)
- = do { arg_boxes <- newBoxyTyVars (replicate n_args argTypeKind)
- ; fun' <- tcExpr fun (mkFunTys (mkTyVarTys arg_boxes) res_ty)
- ; arg_tys' <- mapM readFilledBox arg_boxes
- ; args' <- arg_checker arg_tys'
+ = do { arg_boxes <- newBoxyTyVars (replicate n_args argTypeKind)
+ ; fun' <- tcExpr fun (mkFunTys (mkTyVarTys arg_boxes) res_ty)
+ ; arg_tys' <- mapM readFilledBox arg_boxes
+ ; (_, args') <- arg_checker [] [] arg_tys' -- Yuk
; return (fun', args') }
---------------------------
tcIdApp :: Name -- Function
-> Arity -- Number of args reqd
- -> ([BoxySigmaType] -> TcM arg_results) -- Argument type-checker
- -- The arg-checker guarantees to fill all boxes in the arg types
+ -> ArgChecker results -- The arg-checker guarantees to fill all boxes in the arg types
-> BoxyRhoType -- Result type
- -> TcM (HsExpr TcId, arg_results)
+ -> TcM (HsExpr TcId, results)
-- Call (f e1 ... en) :: res_ty
-- Type f :: forall a b c. theta => fa_1 -> ... -> fa_k -> fres
; let extra_arg_tys' = mkTyVarTys extra_arg_boxes
res_ty' = mkFunTys extra_arg_tys' res_ty
; qtys' <- preSubType qtvs tau_qtvs fun_res_ty res_ty'
- ; let arg_subst = zipOpenTvSubst qtvs qtys'
- fun_arg_tys' = substTys arg_subst fun_arg_tys
-- Typecheck the arguments!
-- Doing so will fill arg_qtvs and extra_arg_tys'
- ; args' <- arg_checker (fun_arg_tys' ++ extra_arg_tys')
+ ; (qtys'', args') <- arg_checker qtvs qtys' (fun_arg_tys ++ extra_arg_tys')
-- Strip boxes from the qtvs that have been filled in by the arg checking
- -- AND any variables that are mentioned in neither arg nor result
- -- the latter are mentioned only in constraints; stripBoxyType will
- -- fill them with a monotype
- ; let strip qtv qty' | qtv `elemVarSet` arg_qtvs = stripBoxyType qty'
- | otherwise = return qty'
- ; qtys'' <- zipWithM strip qtvs qtys'
; extra_arg_tys'' <- mapM readFilledBox extra_arg_boxes
-- Result subsumption
+ -- This fills in res_qtvs
; let res_subst = zipOpenTvSubst qtvs qtys''
fun_res_ty'' = substTy res_subst fun_res_ty
res_ty'' = mkFunTys extra_arg_tys'' res_ty
-- By applying the coercion just to the *function* we can make
-- tcFun work nicely for OpApp and Sections too
; fun' <- instFun orig fun res_subst tv_theta_prs
- ; co_fn' <- wrapFunResCoercion fun_arg_tys' co_fn
- ; return (mkHsCoerce co_fn' fun', args') }
+ ; co_fn' <- wrapFunResCoercion (substTys res_subst fun_arg_tys) co_fn
+ ; return (mkHsWrap co_fn' fun', args') }
\end{code}
Note [Silly type synonyms in smart-app]
-- And pack up the results
; fun' <- instFun orig fun res_subst tv_theta_prs
- ; return (mkHsCoerce co_fn fun') }
+ ; return (mkHsWrap co_fn fun') }
-- Note [Push result type in]
--
= return fun -- Common short cut
instFun orig fun subst tv_theta_prs
- = do {-- !!!SPJ: -- Horrid check for tagToEnum; see Note [tagToEnum#]
- -- !!!SPJ: checkBadTagToEnumCall fun_id qtv_tys
-
- ; let ty_theta_prs' = map subst_pr tv_theta_prs
+ = do { let ty_theta_prs' = map subst_pr tv_theta_prs
- -- First, chuck in the constraints from
- -- the "stupid theta" of a data constructor (sigh)
- ; inst_stupid fun ty_theta_prs'
+ -- Make two ad-hoc checks
+ ; doStupidChecks fun ty_theta_prs'
-- Now do normal instantiation
; go True fun ty_theta_prs' }
where
subst_pr (tvs, theta)
- = (map (substTyVar subst) tvs, substTheta subst theta)
-
- inst_stupid (HsVar fun_id) ((tys,_):_)
- | Just con <- isDataConId_maybe fun_id
- = addDataConStupidTheta orig con tys
- inst_stupid _ _ = return ()
+ = (substTyVars subst tvs, substTheta subst theta)
go _ fun [] = return fun
go _ fun ((tys, theta) : prs)
= do { co_fn <- instCall orig tys theta
- ; go False (HsCoerce co_fn fun) prs }
+ ; go False (HsWrap co_fn fun) prs }
- -- Hack Alert (want_method_inst)!
-- See Note [No method sharing]
- -- If f :: (%x :: T) => Int -> Int
- -- Then if we have two separate calls, (f 3, f 4), we cannot
- -- make a method constraint that then gets shared, thus:
- -- let m = f %x in (m 3, m 4)
- -- because that loses the linearity of the constraint.
- -- The simplest thing to do is never to construct a method constraint
- -- in the first place that has a linear implicit parameter in it.
- want_method_inst theta = not (null theta) -- Overloaded
- && not (any isLinearPred theta) -- Not linear
+ want_method_inst theta = not (null theta) -- Overloaded
&& not opt_NoMethodSharing
- -- See Note [No method sharing] below
\end{code}
Note [Multiple instantiation]
a) it's better for RULEs involving overloaded functions
b) perhaps fewer separated lambdas
+Note [Left to right]
+~~~~~~~~~~~~~~~~~~~~
+tcArgs implements a left-to-right order, which goes beyond what is described in the
+impredicative type inference paper. In particular, it allows
+ runST $ foo
+where runST :: (forall s. ST s a) -> a
+When typechecking the application of ($)::(a->b) -> a -> b, we first check that
+runST has type (a->b), thereby filling in a=forall s. ST s a. Then we un-box this type
+before checking foo. The left-to-right order really helps here.
+
\begin{code}
tcArgs :: LHsExpr Name -- The function (for error messages)
- -> [LHsExpr Name] -> [TcSigmaType] -- Actual arguments and expected arg types
- -> TcM [LHsExpr TcId] -- Resulting args
+ -> [LHsExpr Name] -- Actual args
+ -> ArgChecker [LHsExpr TcId]
-tcArgs fun args expected_arg_tys
- = mapM (tcArg fun) (zip3 args expected_arg_tys [1..])
+type ArgChecker results
+ = [TyVar] -> [TcSigmaType] -- Current instantiation
+ -> [TcSigmaType] -- Expected arg types (**before** applying the instantiation)
+ -> TcM ([TcSigmaType], results) -- Resulting instaniation and args
-tcArg :: LHsExpr Name -- The function (for error messages)
- -> (LHsExpr Name, BoxySigmaType, Int) -- Actual argument and expected arg type
- -> TcM (LHsExpr TcId) -- Resulting argument
-tcArg fun (arg, ty, arg_no) = addErrCtxt (funAppCtxt fun arg arg_no) $
- tcPolyExprNC arg ty
+tcArgs fun args qtvs qtys arg_tys
+ = go 1 qtys args arg_tys
+ where
+ go n qtys [] [] = return (qtys, [])
+ go n qtys (arg:args) (arg_ty:arg_tys)
+ = do { arg' <- tcArg fun n arg qtvs qtys arg_ty
+ ; qtys' <- mapM refineBox qtys -- Exploit new info
+ ; (qtys'', args') <- go (n+1) qtys' args arg_tys
+ ; return (qtys'', arg':args') }
+
+tcArg :: LHsExpr Name -- The function
+ -> Int -- and arg number (for error messages)
+ -> LHsExpr Name
+ -> [TyVar] -> [TcSigmaType] -- Instantiate the arg type like this
+ -> BoxySigmaType
+ -> TcM (LHsExpr TcId) -- Resulting argument
+tcArg fun arg_no arg qtvs qtys ty
+ = addErrCtxt (funAppCtxt fun arg arg_no) $
+ tcPolyExprNC arg (substTyWith qtvs qtys ty)
\end{code}
\begin{code}
-checkBadTagToEnumCall :: Id -> [TcType] -> TcM ()
-checkBadTagToEnumCall fun_id tys
- | fun_id `hasKey` tagToEnumKey
+doStupidChecks :: HsExpr TcId
+ -> [([TcType], ThetaType)]
+ -> TcM ()
+-- Check two tiresome and ad-hoc cases
+-- (a) the "stupid theta" for a data con; add the constraints
+-- from the "stupid theta" of a data constructor (sigh)
+-- (b) deal with the tagToEnum# problem: see Note [tagToEnum#]
+
+doStupidChecks (HsVar fun_id) ((tys,_):_)
+ | Just con <- isDataConId_maybe fun_id -- (a)
+ = addDataConStupidTheta con tys
+
+ | fun_id `hasKey` tagToEnumKey -- (b)
= do { tys' <- zonkTcTypes tys
; checkTc (ok tys') (tagToEnumError tys')
}
- | otherwise -- Vastly common case
- = return ()
where
ok [] = False
ok (ty:tys) = case tcSplitTyConApp_maybe ty of
Just (tc,_) -> isEnumerationTyCon tc
Nothing -> False
+doStupidChecks fun tv_theta_prs
+ = return () -- The common case
+
+
tagToEnumError tys
= hang (ptext SLIT("Bad call to tagToEnum#") <+> at_type)
2 (vcat [ptext SLIT("Specify the type by giving a type signature"),
-> do { thLocalId orig id ty lvl
; case mb_co of
Nothing -> return (HsVar id, ty) -- Wobbly, or no free vars
- Just co -> return (mkHsCoerce co (HsVar id), ty) }
+ Just co -> return (mkHsWrap co (HsVar id), ty) }
other -> failWithTc (ppr other <+> ptext SLIT("used where a value identifer was expected"))
}
; case use_stage of
Brack use_lvl ps_var lie_var | use_lvl > th_bind_lvl
-> thBrackId orig id ps_var lie_var
- other -> checkWellStaged (quotes (ppr id)) th_bind_lvl use_stage
+ other -> do { checkWellStaged (quotes (ppr id)) th_bind_lvl use_stage
+ ; return id }
}
-thLocalId orig id_name id th_bind_lvl (Brack use_lvl ps_var lie_var)
- | use_lvl > th_bind_lvl
- = thBrackId
-thLocalId orig id_name id th_bind_lvl use_stage
- = do { checkWellStaged
- ; return id }
-
--------------------------------------
thBrackId orig id ps_var lie_var
| isExternalName id_name
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