- Glasgow-haskell-users

desugarModule
by Kazu Yamamoto 19 Sep '13

19 Sep '13

Hi, The document of GHC API says that "desugarModule" displays warnings of pattern matching even if HscNothing is specified: http://www.haskell.org/ghc/docs/latest/html/libraries/ghc/GHC.html#t:HscTar… Unfortunately, I cannot get warnings of pattern matching. To demonstrate this, I attached two files: - Main.hs -- using "desugarModule" - B.hs -- a target file: top level signature is missing, pattern is imcompleted When I run "Main.hs" with: % runghc -- -package --ghc-arg=ghc -Wall Main I only got: B.hs:6:1: Warning: Top-level binding with no type signature: main :: IO () Does anyone know how to display warnings of pattern matching with HscNothing? --Kazu <Main> -- runghc -- -package --ghc-arg=ghc A module Main where import GHC import GHC.Paths (libdir) import DynFlags main :: IO () main = defaultErrorHandler defaultFatalMessager defaultFlushOut $ runGhc (Just libdir) $ getWarings "B.hs" "B" getWarings :: String -> String -> Ghc () getWarings targetFile targetModule = do dflags <- getSessionDynFlags let dflags' = dflags { ghcLink = NoLink , hscTarget = HscNothing } dflags'' = foldl wopt_set dflags' [Opt_WarnMissingSigs,Opt_WarnIncompletePatterns] _ <- setSessionDynFlags dflags'' target <- guessTarget targetFile Nothing setTargets [target] _ <- load LoadAllTargets modSum <- getModSummary $ mkModuleName targetModule p <- parseModule modSum t <- typecheckModule p _ <- desugarModule t return () </Main> <B> module B where myHead :: [Int] -> Int myHead (x:_) = x main = do print $ myHead [1,2,3] </B>

1 0

7.8 Release Update
by Austin Seipp 16 Sep '13

16 Sep '13

Friends, After talking with SPJ, we've decided that the cutoff date for the 7.8 feature window will essentially start on Monday, the 16th. This is the beginning of the week before ICFP. This is a week from tomorrow. Afterwords, I suspect we will cut the 7.8 branch in early October (my notes tentatively say Oct. 9th.) This will give us a few weeks of straight bugfixing. Don't let this scare you too much. We're doing this at the beginning of the week so we have time to sort things out. Bug fixes will of course continuously be welcome until the 7.8 branch. However, for pending features, I'd like a status update. Everyone mentioned below, please reply to clarify anything: * Iavor Diatchki and SPJ are working together on the type-nats-simple branch. I believe this will hopefully land in time. Iavor, SPJ - can you comment here? * Trevor and Iavor are also working on kinds without data. Any word here? * Geoffrey is currently moving, but he says the SIMD work and new template-haskell work will land by the end of this week, which is great. * Patrick Palka has a few loose ends to tie off for the parallel compilation driver. I talked to him today, and after Andreas committed his bugfix to base, I believe everything is now working, with the deadlocks sorted out. Patrick, can you confirm? We can get this merged ASAP if so. * Pedro and Richard - what's the story on propositional equality, etc? This is mentioned on the status page[1] but I'm not sure what else needs to be done. I know Pedro committed the work to make manual Typeable instances an error, which is great. * Luite and Edsko will be talking about some final changes to the hooks patch, and afterwords it can hopefully be integrated. I'll keep up with them this week. * I am currently working on integrating the Applicative-Monad warning, but this requires some upstream patches for the build to work. However, we still need to sync several upstream libraries, and this will be happening over the next few weeks. Therefore, I may commit it, and incrementally fix validation errors as time goes on and me and Herbert sync upstreams. IMO, most of these look to be in good shape, I think. If you *do not think you'll make it by the 16th*, please let me know. We can possibly still land it the week of the 16th, provided I know ASAP. But we really really need to know, because many people will be gone the following week. In the following few days, I'm hoping going to finish off everything I can in the patch queue, and fix my remaining bugs, and investigate Dynamic GHCi in particular. Again, if you don't think you can make it on the 16th, but still within the week, we can of discuss it. -- Regards, Austin - PGP: 4096R/0x91384671

11 35

RE: Question about correct GHC-API use for type checking (or zonking, or tidying)
by p.k.f.holzenspies＠utwente.nl 11 Sep '13

11 Sep '13

Well, my tcLocalBinds seems to have a different type then yours (this is from my copy of 7.6.3 and it's the same in the HEAD that I just synced): tcLocalBinds :: HsLocalBinds Name -> TcM thing -> TcM (HsLocalBinds TcId, thing) If I want to get a GblEnv out, I can use getGblEnv, but doing this: mkId :: Maybe FreeVars -> LHsExpr Name -> Name -> TcM Id mkId fvs expr@(L l _) nm = do ((binds', gbl_env),lie) <- captureConstraints $ tcLocalBinds binds getGblEnv setGblEnv gbl_env (tcLookupId nm) where binds = HsValBinds $ ValBindsOut [(NonRecursive, unitBag fixbnd)] [] the_bind = mkTopFunBind (L l nm) [mkMatch [] expr emptyLocalBinds] fixbnd = L l $ maybe the_bind (\vs -> the_bind { bind_fvs = vs }) fvs fails on the tcLookupId with a GHC internal error complaining that my name is "not in scope during type checking, but it passed the renamer." Ph. From: Simon Peyton-Jones [mailto:simonpj@microsoft.com] Sent: dinsdag 10 september 2013 14:19 To: Holzenspies, P.K.F. (EWI) Cc: glasgow-haskell-users(a)haskell.org Subject: RE: Question about correct GHC-API use for type checking (or zonking, or tidying) What goes wrong if you follow my suggestion below? tcLocalBinds takes a set of bindings, such as x=e and returns a GblEnv whose type envt is extended with a binding for x with its generalised type. This type wil indeed be closed, unless the current environment (in which tcLocalBinds runs) has bindings with open types. Which in your case it probably doesn't. I feel that I am not being helpful but I'm not sure how to help more. S From: "Philip K.F. Hölzenspies" [mailto:p.k.f.holzenspies@utwente.nl] Sent: 04 September 2013 21:25 To: Simon Peyton-Jones Cc: glasgow-haskell-users(a)haskell.org<mailto:glasgow-haskell-users@haskell.org> Subject: Re: Question about correct GHC-API use for type checking (or zonking, or tidying) Ah, this is good to know. What I really would like is a function: mkId :: Name -> LHsExpr Name -> TcM Id where that Id is something I can store in my own monad (IA). The meaning of this, is indeed "let <name> = <expression>" as a top-level binding. The behaviour should actually be the same as that statement at the ghci-prompt. My IA monad implements liftTcM as something that invokes a TcM-monad, i.e. liftTcM :: TcM b -> IA b liftTcM thing_inside = do hsc_env <- getSession stored_ids <- getStoredIds :: IA [Id] -- this is the list of all Ids made through mkId mentioned above ioMsgMaybe . initTcPrintErrors hsc_env iNTERACTIVE $ setInteractiveContext hsc_env (hsc_IC hsc_env) $ tcExtendGlobalValEnv stored_ids $ -- or tcExtendIdEnv?? thing_inside In the example you give below, I'm curious which "thing_inside" you give to tcLocalBinds to get you the correct global environment. Also, if I do what you suggest, i.e. poly_id <- setGblEnv gbl_env (tcLookupId the_id_name) is that poly_id "self contained," in the sense that I can put it in a new instantiation as shown above? Regards, Philip [cid:image001.jpg@01CEAEDB.407DA510] Simon Peyton-Jones<mailto:simonpj@microsoft.com> September 4, 2013 6:00 PM The id you are getting is a monomorphic id, with a type like a->a, not the polymorphic forall a. a->a. You don't want to go round arbitrarily creating a new Id with the same unique but a different type. I have no idea what would happen then. It's hard for me to understand just what you code is trying to do. I think you are making bindig it = <some expr> and then you want the type of "it". Maybe something like (binds', gbl_env) <- tcLocalBinds (..your bindin..) poly_id <- setGblEnv gbl_env (tcLooupId the_id_name) But I'm not totally sure. S

1 0

Fedora ghc-7.7 repo
by Jens Petersen 08 Sep '13

08 Sep '13

I setup an experimental Fedora 20 repo for ghc-7.7 at http://repos.fedorapeople.org/repos/petersen/ghc-7.7 which currently has builds of ghc-7.7.20130828 for x86_64, i686, and armv7hl without profiling. Let me know if you notice any problems with it. Thanks, Jens

1 0

bundled libraries in ghc
by Jens Petersen 05 Sep '13

05 Sep '13

Hi, I have been doing some test builds of ghc-7.7 recently. Since ghc gets built now with dynamic linking by default, the bundled linked libraries that ghc does not ship are more visible now: this is not really a new problem per se just that now with shared libraries by default it is more obvious! The libraries in question here are haskeline, terminfo, and xhtml. Putting the technical issue of installing both these bundled shared libraries and their corresponding system packages aside for now, the situation is at best uncomfortable for distros like Fedora which do not allow bundled copies of libraries in packages. [1] So my suggestion would be actually to ship the 3 libraries in ghc-7.8. xhtml is of course already part of Haskell Platform but hopefully that need not be a big problem. Whether the other two should be formally added to HP or not may be an open question but I don't see that it need block their inclusion in ghc's manifest. Besides I am anyway not really sure how to handle having both those 3 shared libraries installed for runtime ghc along with the same versions of the corresponding packages? Jens ps BTW it is really nice to see that the bundled tarballs for Windows have been moved to a separate source tarball. :-) [1] https://fedoraproject.org/wiki/Packaging:No_Bundled_Libraries

2 3

Question about correct GHC-API use for type checking (or zonking, or tidying)
by p.k.f.holzenspies＠utwente.nl 04 Sep '13

04 Sep '13

Dear GHC-ers, I'm working on building an interactive environment around the composition of expressions. Users can type in (i.e. give strings of) expressions and can then use these expressions to produce other expressions. I'm close to having a working GHC-API binding for this. The resulting types, however, still contain some things I don't quite understand. Any help would be appreciated. Below, I've included the function exprFromString which should parse, rename and typecheck strings to Id-things and give their type (although, ideally, the idType of said Id-thing should be the same as the type returned). This function lives in the IA (InterActive) monad; a monad that is a GhcMonad and can lift monadic computations in TcM into itself using liftTcM (which uses the initTcPrintErrors and setInteractiveContext functions similarly to TcRnDriver.tcRnExpr). Near the end of the function, debugging output is produced. This output confuses me slightly. Here is the output for the three inputs "map (+1) [1..10]", "5" and "\\x -> x": map (+1) [1..10] pre-zonk: forall b. (GHC.Enum.Enum b_i, GHC.Num.Num b_i) => [b_i] post-zonk: forall b. (GHC.Enum.Enum b_i, GHC.Num.Num b_i) => [b_i] idType: [b_c] tidied: forall b. (GHC.Enum.Enum b_i, GHC.Num.Num b_i) => [b_i] 5 pre-zonk: forall a. GHC.Num.Num a_d => t_c post-zonk: forall a. GHC.Num.Num a_d => t_c idType: a_b tidied: forall a. GHC.Num.Num a_d => t_c \x -> x pre-zonk: forall t. t_e post-zonk: forall t. t_e idType: forall t. t -> t tidied: forall t. t_e The zonking and tidying part of the type-checking process are still a bit unclear to me and I suspect the problems arise there. It looks to me that the type variables in the quantifications are different ones from those in the pi/rho-types. I had expected the types to only contain the variables over which they are quantified, so e.g. in the map-example, I had expected "forall b . (GHC.Enum.Enum b, GHC.Num.Num b) => [b]" Can anyone explain what I'm missing? Regards, Philip exprFromString :: String -> IA (Id,Type) exprFromString str = do dfs <- getDynFlags let pp = showSDoc dfs . ppr pst <- mkPState dfs buf <$> newRealSrcLoc {- Parse -} (loc,rdr_expr) <- case unP parseStmt pst of PFailed span err -> throwOneError (mkPlainErrMsg dfs span err) POk pst' (Just (L l (ExprStmt rdr_expr _ _ _))) -> do logWarningsReportErrors (getMessages pst') return (l,rdr_expr) POk pst' thing -> throw $ maybe EmptyParse (const NonExpressionParse) thing liftTcM $ do fresh_it <- freshName loc str {- Rename -} (rn_expr, fvs) <- checkNoErrs $ rnLExpr rdr_expr {- Typecheck -} let binds = mkBinds fresh_it rn_expr fvs (((_bnds,((_tc_expr,res_ty),id)),untch),lie) <- captureConstraints . captureUntouchables $ tcLocalBinds binds ((,) <$> tcInferRho rn_expr <*> tcLookupId fresh_it) ((qtvs, dicts, _bool, _evbinds), lie_top) <- captureConstraints $ simplifyInfer True False [(fresh_it, res_ty)] (untch,lie) let all_expr_ty = mkForAllTys qtvs (mkPiTypes dicts res_ty) say str say $ " pre-zonk: " ++ pp all_expr_ty zonkTcType all_expr_ty say $ " post-zonk: " ++ pp all_expr_ty say $ " idType: " ++ pp (idType id) say $ " tidied: " ++ pp (tidyTopType all_expr_ty) return (id,all_expr_ty) where say = liftIO . putStrLn buf = stringToStringBuffer str freshName loc str = (\u -> mkInternalName u name loc) <$> newUnique where name = mkOccNameFS varName $ fsLit $ "it" ++ show (lineOf loc) isVarChar c = isAlphaNum c || c == '_' || c == '\'' lineOf (RealSrcSpan s) = srcSpanStartLine s lineOf _ = -1 mkBinds :: Name -> LHsExpr Name -> FreeVars -> HsLocalBinds Name mkBinds nm e@(L l _) fvs = HsValBinds $ ValBindsOut [(NonRecursive, unitBag the_bind)] [] where the_bind = L l (mkTopFunBind (L l nm) [mkMatch [] e emptyLocalBinds]) { bind_fvs = fvs }

2 5

32-bit libs required for 64-bit install
by Yitzchak Gale 28 Aug '13

28 Aug '13

I had trouble installing the generic 64-bit Linux tarball for 7.6.3. With some help from Ian, who pointed out that the problem was related to ld-linux.so, I finally figured out the root of the problem: the installation requires *both* the 64-bit and 32-bit versions of libc6 plus deps to be available. Once the installation was complete, I could then remove the 32-bit libs and ghc still seems to work. It appears that the 32-bit libs are only required for some of the auxiliary executables that come with the tarball, such as ghc-pwd. Is there any reason in principle that we only allow 64-bit GHC to be installed on multiarch Linux? That seems like a rather arbitrary restriction. In the meantime, something ought to be said about this on the download page. More details: the target system for the installation in my case was an up-to-date Ubuntu 12.04 LTS (precise) amd64 headless server running in a VMware containter. Thanks, Yitz

3 2

TypeHoles behaviour
by Andres Löh 28 Aug '13

28 Aug '13

Hi. I've just started playing with TypeHoles. (I'm writing some Haskell course materials and would like to use them from the very beginning once they become available.) However, I must say that I don't understand the current notion of "relevance" that seems to determine whether local bindings are included or not. The current rule seems to be that bindings are included only if the intersection between the type variables their types involve and the type variables in the whole is non-empty. However, I think this is confusing. Let's look at a number of examples: > f1 :: Int -> Int -> Int > f1 x y = _ Found hole ‛_’ with type: Int In the expression: _ In an equation for ‛f1’: f1 x y = _ No bindings are shown. > f2 :: a -> a -> a > f2 x y = _ Found hole ‛_’ with type: a Where: ‛a’ is a rigid type variable bound by the type signature for f2 :: a -> a -> a at List.hs:6:7 Relevant bindings include f2 :: a -> a -> a (bound at List.hs:7:1) x :: a (bound at List.hs:7:4) y :: a (bound at List.hs:7:6) In the expression: _ In an equation for ‛f2’: f2 x y = _ Both x and y (and f2) are shown. Why should this be treated differently from f1? > f3 :: Int -> (Int -> a) -> a > f3 x y = _ Found hole ‛_’ with type: a Where: ‛a’ is a rigid type variable bound by the type signature for f3 :: Int -> (Int -> a) -> a at List.hs:9:7 Relevant bindings include f3 :: Int -> (Int -> a) -> a (bound at List.hs:10:1) y :: Int -> a (bound at List.hs:10:6) In the expression: _ In an equation for ‛f3’: f3 x y = _ Here, y is shown, but x isn't, even though y has to be applied to an Int in order to produce an a. Of course, it's possible to obtain an Int from elsewhere ... f4 :: a -> (a -> b) -> b f4 x y = _ Found hole ‛_’ with type: b Where: ‛b’ is a rigid type variable bound by the type signature for f4 :: a -> (a -> b) -> b at List.hs:12:7 Relevant bindings include f4 :: a -> (a -> b) -> b (bound at List.hs:13:1) y :: a -> b (bound at List.hs:13:6) In the expression: _ In an equation for ‛f4’: f4 x y = _ Again, only y is shown, and x isn't. But here, the only sane way of filling the hole is by applying "y" to "x". Why is one more relevant than the other? f5 x y = _ Found hole ‛_’ with type: t2 Where: ‛t2’ is a rigid type variable bound by the inferred type of f5 :: t -> t1 -> t2 at List.hs:15:1 Relevant bindings include f5 :: t -> t1 -> t2 (bound at List.hs:15:1) In the expression: _ In an equation for ‛f5’: f5 x y = _ Neither x and y are included without a type signature. Even though all of the above types are admissible, which would convince GHC that one or even all may be relevant. IMHO, this isn't worth it. It's a confusing rule. Just include all local bindings in the output, always. That's potentially verbose, but easy to understand. It's also potentially really helpful, because it trains beginning programmers to see what types local variables get, and it's a way to obtain complex types of locally bound variables for expert programmers. It's also much easier to explain. It should be easier to implement, too :) Could we please change it? Cheers, Andres -- Andres Löh, Haskell Consultant Well-Typed LLP, http://www.well-typed.com

5 5

Fwd: New restrictions to open type families
by Akio Takano 23 Aug '13

23 Aug '13

(I forgot to send to the list, trying again) Thank you very much for your detailed explanation! On Fri, Aug 23, 2013 at 1:24 PM, Richard Eisenberg <eir(a)cis.upenn.edu>wrote: > This is a good question. Happily, there are at least two decent answers. > > 1) We're not sure that this problem cannot cause a segfault… it's just > that we've been unable to produce one when trying. Perhaps we haven't tried > hard enough. > I successfully constructed such an example. https://github.com/takano-akio/type-family-overlap - Akio

3 3

New restrictions to open type families
by Akio Takano 23 Aug '13

23 Aug '13

Hi, Looking at the ticket [1] and a draft paper linked there [2] , I learned that in GHC 7.8, two type family instances are considered overlapping if the argument lists unify in the presence of infinite types. My question is, why is this restriction necessary? A footnote in the paper states that it was not possible with GHC 7.6 to actually exploit the inconsistency. Would it be difficult to solve the problem by making this behaviour part of the specification, rather than accepting fewer programs? [1] http://ghc.haskell.org/trac/ghc/ticket/8154 [2] http://www.cis.upenn.edu/~eir/papers/2014/axioms/axioms-extended.pdf Regards, Takano Akio

3 2