June 2014 - ghc-tickets

[GHC] #8650: Unexpected behaviour of import ccall "header.h function"
by GHC 21 Dec '14

21 Dec '14

#8650: Unexpected behaviour of import ccall "header.h function" ------------------------------------+-------------------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Documentation bug Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+-------------------------------------- When I write {{{ foreign import ccall "myheader.h myfunction" function :: IO ... }}} Is GHC supposed to check the existence of the header file, or do anything with it? Because I can still write {{{"myheaderBLA.h myfunction"}}} and it doesn't care about the first word (no error, ever, not even in linking, executable builds all fine). ---- Relatedly, I can write {{{ foreign import ccall "some.rubbish" f :: IO ... }}} and as long as {{{"some.rubbish"}}} contains a dot, nothin in the system will ever complain. carter suggested that maybe names with a dot inside are ignored by a linker. This leads me to the question: In my example above, is {{{myheaderBLA.h}}} actually understood as some kind of file and ignored by e.g. GHC, or is it a garbled symbol name? In that case, why does http://www.haskell.org/onlinereport/haskell2010/haskellch8.html suggest {{{ccall "string.h strlen"}}}? In the other case, why would it suggest this if the {{{"string.h"}}} part is ignored? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8650> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8984: Improve output of failed GeneralizedNewtypeDeriving coercion due to type roles
by GHC 19 Dec '14

19 Dec '14

#8984: Improve output of failed GeneralizedNewtypeDeriving coercion due to type roles -------------------------------------------+------------------------------- Reporter: haasn | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type checker) | Version: 7.8.1 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------+------------------------------- When trying to build acme-schoenfinkel (as an example), I came across an error like this: {{{ Control/Category/Schoenfinkel.hs:66:48: Could not coerce from ‘cat (cat b c, b) c’ to ‘cat (WrappedSchoenfinkel cat b c, b) c’ because ‘cat (cat b c, b) c’ and ‘cat (WrappedSchoenfinkel cat b c, b) c’ are different types. arising from the coercion of the method ‘app’ from type ‘forall b c. cat (cat b c, b) c’ to type ‘forall b c. WrappedSchoenfinkel cat (WrappedSchoenfinkel cat b c, b) c’ Possible fix: use a standalone 'deriving instance' declaration, so you can specify the instance context yourself When deriving the instance for (ArrowApply (WrappedSchoenfinkel cat)) }}} It was not immediately clear to me as a user that this was caused due to it wanting GNT which was now being blocked by type roles (rightfully so, as this instance allows UnsafeCoerce!), and beyond that, what the specific rule that triggered this was. In this case the failure is due to ‘WrappedSchoenfinkel cat b c’ not being nominally equal to ‘cat b c’, in the type ‘(WrappedSchoenfinkel cat b c, b)’, which is required to be nominally equal to ‘(cat b c, b)’ because it's used as a parameter to the variable ‘cat’. Printing a location breakdown and context information similar to this to the user would help understanding and debugging roles a lot. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8984> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8749: Pattern synonyms crash GHCi
by GHC 18 Dec '14

18 Dec '14

#8749: Pattern synonyms crash GHCi ------------------------------------+------------------------------------- Reporter: monoidal | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- {{{ ghci -XPatternSynonyms > let pattern P x = x }}} causes a panic. I understand pattern synonyms are currently unsupported in GHCi, but we should give an error message, not a panic. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8749> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9040: HPC doesnt work as expected on mac
by GHC 17 Dec '14

17 Dec '14

#9040: HPC doesnt work as expected on mac ------------------------------------+--------------------------------- Reporter: carter | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+--------------------------------- on commit 716f3586e23faeb8a4a08e77ebdbfa645c15f9a8 of my in progress project git@github.com:wellposed/numerical-core.git , when i try test library coverage by the following command (asuming dependencies are installed) cabal clean ; cabal configure --enable-tests --enable-library-coverage; cabal build; cabal test i get the following output at the end Writing: numerical-core-0.1.0.0/Numerical.Nat.hs.html hpc: can not find numerical-core-0.1.0.0/Numerical.Array.Shape in ["./.hpc","./dist/hpc/mix/numerical-core-0.1.0.0","./dist/hpc/mix/spec- suite"] this apparently only happens on OS X. here are the build logs from my run https://gist.github.com/cartazio/11312249 (i'll amend that to link to a cleaner output later) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9040> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8525: lib/integer/integerConstantFolding fails with -DDEBUG
by GHC 17 Dec '14

17 Dec '14

#8525: lib/integer/integerConstantFolding fails with -DDEBUG -------------------------------+------------------------------------------- Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Test Suite | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: integerConstantFolding Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | -------------------------------+------------------------------------------- Hi, with `-DDEBUG` in `GhcStage2HcOpts`, the test integerConstantFolding fails: {{{ =====> integerConstantFolding(normal) 1103 of 3814 [0, 1, 0] cd ./lib/integer && $MAKE -s --no-print-directory integerConstantFolding </dev/null >integerConstantFolding.run.stdout 2>integerConstantFolding.run.stderr Actual stderr output differs from expected: --- /dev/null 2013-11-12 10:54:14.804286745 +0100 +++ ./lib/integer/integerConstantFolding.run.stderr 2013-11-12 15:33:12.384669953 +0100 @@ -0,0 +1,62 @@ +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl{v r3Ok} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl4{v r3Oo} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl8{v r3Os} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl12{v r3Ow} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + ww1{v r3OO} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl48{v r3P7} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl52{v r3Pb} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl56{v r3Pf} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl60{v r3Pj} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl64{v r3Pn} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl68{v r3Pr} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + ww2{v r3Pv} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + ww3{v r3Pw} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + ww4{v r3PG} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + ww5{v r3PH} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl90{v r3PR} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl94{v r3PV} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl98{v r3PZ} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl102{v r3Q3} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl106{v r3Q7} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl110{v r3Qb} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl134{v r3Qz} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl138{v r3QD} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl142{v r3QH} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl146{v r3QL} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl153{v r3QS} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl161{v r3R0} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl165{v r3R4} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl169{v r3R8} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl173{v r3Rc} [gid] True False +WARNING: file compiler/stgSyn/CoreToStg.lhs, line 269 + lvl177{v r3Rg} [gid] True False *** unexpected failure for integerConstantFolding(normal) }}} The warning is in `consistentCafInfo` source:compiler/stgSyn/CoreToStg.lhs and was was last touched by SPJ in [fdf86568], and originally introduced by simmonmar in 2e6d322e130a8c37807a14699bbcbf9eb08fc970. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8525> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8584: Pattern synonym type signatures
by GHC 17 Dec '14

17 Dec '14

#8584: Pattern synonym type signatures ------------------------------------+------------------------------------- Reporter: cactus | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: 5144 | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Currently, the only way to specify a type signature for a pattern synonym is by adding type annotations to the right-hand side, like this: {{{ {-# LANGUAGE PatternSynonyms, ScopedTypeVariables #-} pattern Single x = ([x] :: [Int]) }}} Bespoke syntax for adding type signatures for pattern synonyms would probably be useful. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8584> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8968: Pattern synonyms and GADTs
by GHC 17 Dec '14

17 Dec '14

#8968: Pattern synonyms and GADTs -------------------------------------+------------------------------------- Reporter: kosmikus | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.1-rc2 checker) | Operating System: Unknown/Multiple Keywords: | Type of failure: GHC rejects Architecture: Unknown/Multiple | valid program Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- I think this one is different from #8966, but feel free to close one as duplicate if it turns out to be the same problem. The following program (using GADTs and pattern synonyms, but not kind polymorphism or data kinds) fails to check with ghc-7.8.1-rc2, but I think it should: {{{ {-# LANGUAGE GADTs, KindSignatures, PatternSynonyms #-} data X :: (* -> *) -> * -> * where Y :: f Int -> X f Int pattern C x = Y (Just x) }}} The error I get is the following: {{{ PatKind.hs:6:18: Couldn't match type ‘t’ with ‘Maybe’ ‘t’ is untouchable inside the constraints (t1 ~ Int) bound by a pattern with constructor Y :: forall (f :: * -> *). f Int -> X f Int, in a pattern synonym declaration at PatKind.hs:6:15-24 ‘t’ is a rigid type variable bound by the inferred type of C :: X t t1 x :: Int at PatKind.hs:1:1 Expected type: t Int Actual type: Maybe Int In the pattern: Just x In the pattern: Y (Just x) PatKind.hs:6:18: Could not deduce (t ~ Maybe) from the context (t1 ~ Int) bound by the type signature for (Main.$WC) :: t1 ~ Int => Int -> X t t1 at PatKind.hs:6:9 ‘t’ is a rigid type variable bound by the type signature for (Main.$WC) :: t1 ~ Int => Int -> X t t1 at PatKind.hs:1:1 Expected type: t Int Actual type: Maybe Int Relevant bindings include ($WC) :: Int -> X t t1 (bound at PatKind.hs:6:9) In the first argument of ‘Y’, namely ‘(Just x)’ In the expression: Y (Just x) }}} Note that I'd be perfectly happy to provide a type signature for the pattern synonym, but I don't know of any syntax I could use. The Wiki page at https://ghc.haskell.org/trac/ghc/wiki/PatternSynonyms mentions I might be able to write {{{ pattern C :: Int -> X Maybe Int }}} but this triggers a parse error. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8968> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9161: Pattern synonyms interact badly with data kinds
by GHC 17 Dec '14

17 Dec '14

#9161: Pattern synonyms interact badly with data kinds -------------------------------------------------+------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler | Version: Keywords: renamer, pattern synonyms, | 7.8.2 data kinds | Operating System: Architecture: Unknown/Multiple | Linux Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------------+------------------------- If we define a pattern `A` and use it as a type: {{{ {-# LANGUAGE PatternSynonyms, DataKinds #-} pattern A = () b :: A b = undefined }}} we get the following error: {{{ Prelude> :load tmp.XDGqzccOAV.hs [1 of 1] Compiling Main ( /tmp/tmp.XDGqzccOAV.hs, interpreted ) /tmp/tmp.XDGqzccOAV.hs:5:9: GHC internal error: ‘A’ is not in scope during type checking, but it passed the renamer tcl_env of environment: [] In the type signature for ‘blah’: blah :: A Failed, modules loaded: none. }}} Also occurs with different arities of `A` (the arity of the pattern and type can differ) and defining it as an operator (enabling the `TypeOperators` pragma). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9161> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9226: Internal error when using equality constraint in pattern synonyms
by GHC 17 Dec '14

17 Dec '14

#9226: Internal error when using equality constraint in pattern synonyms -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 7.8.2 Keywords: renamer, pattern | Operating System: Linux synonyms, GADTs | Type of failure: GHC rejects Architecture: x86 | valid program Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- While going through [http://www.andres-loeh.de/dgp2005.pdf Extensible datatypes] I had the following code: {{{ {-# LANGUAGE GADTs, PatternSynonyms, ScopedTypeVariables, Rank2Types #-} data Rep a where RUnit :: Rep () RInt :: Rep Int RChar :: Rep Char REither :: Rep a -> Rep b -> Rep (Either a b) RPair :: Rep a -> Rep b -> Rep (a, b) foo :: (Rep a, a) -> Bool foo (RUnit, ()) = True }}} And I wanted to make a pattern synonyms matching `(RUnit, ())` in `foo`, my initial attempt was: {{{ pattern PUnit1 = (RUnit, ()) }}} gives the error (`punit1.log`) while writing {{{ pattern PUnit2 = (RUnit, ()) :: (Rep (), ()) }}} compiles but can't be used in `foo`. Trying: {{{ pattern PUnit3 = (RUnit, ()) :: (a ~ ()) => (Rep a, a) }}} gives a ''GHC internal error'' (`punit3.log`). I tried various other patterns such as: {{{ pattern PUnit4 <- (RUnit, ()) pattern PUnit5 <- (RUnit, ()) :: (Rep (), ()) pattern PUnit6 <- (RUnit, ()) :: (a ~ ()) => (Rep a, a) pattern PUnit7 = (RUnit, ()) :: forall a. (a ~ ()) => (Rep a, a) pattern PUnit8 <- (RUnit, ()) :: forall a. (a ~ ()) => (Rep a, a) ... }}} None of which work. The final goal was to rewrite: {{{ eq :: Rep a -> a -> a -> Bool eq rep a b = case (rep, a, b) of (RUnit, (), ()) -> True (RInt, n1, n2) -> n1 == n2 (RChar, c1, c2) -> c1 == c2 (REither l r, Left a, Left b) -> eq l a b (REither l r, Right a, Right b) -> eq r a b (REither{}, _, _) -> False (RPair l r, (a1, a2), (b1, b2)) -> eq l a1 b1 && eq r a2 b2 }}} as something like {{{ pattern PUnit = (RUnit, ()) -- (a ~ ()) => (Rep a, a) pattern PInt n = (RInt, n) -- (a ~ Int) => (Rep a, a) -- ... eq :: Rep a -> a -> a -> Bool eq rep a b = case ((rep, a), (rep, b)) of (PUnit, PUnit) -> True (PInt n1, PInt n2) -> n1 == n2 (PChar c1, PChar c2) -> c1 == c2 (PLeft l l1, PLeft l l2) -> eq l l1 l2 (PRight r r1, PRight r r2) -> eq r r1 r2 ((REither{}, _), _) -> False (PFst l (a1, b1), PSnd r (a2, b2)) -> eq l a1 b1 && eq r a2 b2 }}} where one can avoid pattern matching against the `Rep` constructor directly. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9226> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9132: takeWhile&C. still not fusible
by GHC 15 Dec '14

15 Dec '14

#9132: takeWhile&C. still not fusible -------------------------------------+------------------------------------- Reporter: Blaisorblade | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.8.2 Keywords: fusion | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Runtime Difficulty: Moderate (less | performance bug than a day) | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- takeWhile is not still fusible, 2 1/2 years after this report: http://www.haskell.org/pipermail/glasgow-haskell- users/2011-December/021299.html The discussion suggests making takeWhile a good producer/consumer with foldr/build fusion: takeWhile' :: (a -> Bool) -> [a] -> [a] takeWhile' p xs = build $ \c n -> foldr (takeWhileF p c n) n xs {-# INLINE takeWhile' #-} takeWhileF p c n x xs = if p x then x `c` xs else n Furthermore, the discussion suggests having rewrite rules to go to this version and then rewrite back (if fusion fails). The report also mentions concatMap (which is a separate known problem). It also mentions drop and dropWhile, but I don't see when they perform allocations, so I think that's an erroneous request. I experienced the bug on GHC 7.6.3, but it seems still there in base-4.7.0.0, judging from the source: http://hackage.haskell.org/package/base-4.7.0.0/docs/src/GHC- List.html#takeWhile -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9132> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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