February 2017 - ghc-tickets

[GHC] #12967: GHC 8.0.1 Panic for current Aeson 1.0.2.1
by GHC 04 Apr '17

04 Apr '17

#12967: GHC 8.0.1 Panic for current Aeson 1.0.2.1 -------------------------------------+------------------------------------- Reporter: bitemyapp | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ [1 of 1] Compiling Main ( Dates.hs, .stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/aeson-benchmark-dates/aeson- benchmark-dates-tmp/Main.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): Simplifier ticks exhausted When trying UnfoldingDone $s>$< To increase the limit, use -fsimpl-tick-factor=N (default 100) If you need to do this, let GHC HQ know, and what factor you needed To see detailed counts use -ddump-simpl-stats Total ticks: 153200 }}} I am not certain if this is a duplicate of: - https://ghc.haskell.org/trac/ghc/ticket/10083 - https://ghc.haskell.org/trac/ghc/ticket/12789 - https://ghc.haskell.org/trac/ghc/ticket/11263 - https://ghc.haskell.org/trac/ghc/ticket/5539 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12967> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12650: Too many warnigns about consistentCafInfo
by GHC 04 Apr '17

04 Apr '17

#12650: Too many warnigns about consistentCafInfo -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Building GHC with debug on yiedls in many (97!) warnings of the form {{{ WARNING: file compiler/stgSyn/CoreToStg.hs, line 252 $fFunctorIOEnv True False }}} The code in question is {{{ -- Assertion helper: this checks that the CafInfo on the Id matches -- what CoreToStg has figured out about the binding's SRT. The -- CafInfo will be exact in all cases except when CorePrep has -- floated out a binding, in which case it will be approximate. consistentCafInfo :: Id -> GenStgBinding Var Id -> Bool consistentCafInfo id bind = WARN( not (exact || is_sat_thing) , ppr id <+> ppr id_marked_caffy <+> ppr binding_is_caffy ) safe where safe = id_marked_caffy || not binding_is_caffy exact = id_marked_caffy == binding_is_caffy id_marked_caffy = mayHaveCafRefs (idCafInfo id) binding_is_caffy = topStgBindHasCafRefs bind is_sat_thing = occNameFS (nameOccName (idName id)) == fsLit "sat" }}} It would be nice to have less warnings, to make them more useful. I don’t know if the warning is not right, or if there is something that can be fixed about the thing it is warning about. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12650> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12461: Document -O3
by GHC 04 Apr '17

04 Apr '17

#12461: Document -O3 -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Documentation Unknown/Multiple | bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC accepts the flag -O3, but I can't find any documentation on it. What does it do? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12461> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9596: Create monoidal category framework for arrow desugarer
by GHC 03 Apr '17

03 Apr '17

#9596: Create monoidal category framework for arrow desugarer -------------------------------------+------------------------------------- Reporter: spacekitteh | Owner: Type: task | spacekitteh Priority: normal | Status: new Component: GHC API | Milestone: 7.10.1 Keywords: | Version: Architecture: Unknown/Multiple | Operating System: Difficulty: Project (more | Unknown/Multiple than a week) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- I'm going to put it into a GHC namespace (GHC.Arrows.Experimental, perhaps) and put instances for Arrow and such in there as well. In a later ticket I'll work on the desugarer, converting erverything into SMC combinators rather than Arrow combinators. The basic design is [blog.spacekitteh.moe/posts/new-monoidal-cats.html here] -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9596> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13332: Report unrecognized pragmas earlier
by GHC 03 Apr '17

03 Apr '17

#13332: Report unrecognized pragmas earlier -------------------------------------+------------------------------------- Reporter: crockeea | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In the following example, I have a typo in the `UndecidableInstances` pragma (`LANGUAGE` is misspelled), however, GHC ''only'' reports that `UndecidableInstances` is required. This is very confusing, since it appears that I have enabled that pragma. {{{ {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE FlexibleInstances #-} {-# LANUGAGE UndecidableInstances #-} instance (Num [a]) => Num a }}} Only when I comment out the instance does GHC report that there is an unrecognized pragma, at which point it became obvious that there was a typo. It would be very helpful if GHC reported the warning about the unrecognized pragma before or at the same time as the error about needing `UndecidableInstances`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13332> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10976: Applicative Comprehensions
by GHC 02 Apr '17

02 Apr '17

#10976: Applicative Comprehensions -------------------------------------+------------------------------------- Reporter: davidar | Owner: Type: feature | Status: new request | Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: 8914 | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- As discussed on `ghc-devs`, when both the `MonadComprehensions` and `ApplicativeDo` language extensions are enabled, it should be possible to use comprehension-notation (in addition to do-notation) for `Applicative`s. This would allow, for example, an expression like {{{#!hs (\x y -> x + 2*y) <$> ZipList [1..10] <*> ZipList [10,20..100] }}} to also be written as {{{#!hs [ x + 2*y | x <- ZipList [1..10], y <- ZipList [10,20..100] ] }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10976> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12490: ApplicativeDo and RebindableSyntax do not desugar as expected
by GHC 02 Apr '17

02 Apr '17

#12490: ApplicativeDo and RebindableSyntax do not desugar as expected -------------------------------------+------------------------------------- Reporter: AaronFriel | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In a module with -XApplicativeDo, -XRebindableSyntax, and local definitions for everything in the Functor-Applicative-Monad hierarchy, do- notation always desugars to "join (... (return ...))" (or /s/return/pure/). This forces the result to have at least the constraints of join, which in my case is "IxMonad m". {{{#!hs {-# LANGUAGE RebindableSyntax, ApplicativeDo #-} module My where -- straightforward definitions of fmap, pure, (<*>), join, return, (>>=), (>>) and fail in terms of IxFunctor, IxPointed, IxApplicative, IxMonad fPure m = do a <- m b <- m pure (a, b) fReturn m = do a <- m b <- m return (a, b) }}} According to -ddump-ds, these desugar to: {{{#!hs fPure :: IxMonad m => m k1 k1 a -> m k1 k1 (a, a) fPure m = My.join ( My.(<*>) (My.fmap (\a b -> My.pure (a, b)) m) m ) fReturn :: IxMonad m => m k1 k1 a -> m k1 k1 (a, a) fReturn m = My.join ( My.(<*>) (My.fmap (\a b -> My.return (a, b)) m) m ) }}} But I would expect: {{{#!hs fPure m = My.(<*>) (My.fmap (\a b -> (a, b)) m) m fReturn m = -- same }}} It appears that when "return" is not from base, ApplicativeDo only partially desugars to the specification. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12490> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11612: Bug in ApplicativeDo
by GHC 02 Apr '17

02 Apr '17

#11612: Bug in ApplicativeDo -------------------------------------+------------------------------------- Reporter: simonmar | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I discovered a bug in `ApplicativeDo`. Fix coming shortly. The problem is illustrated by this test case, which I will add to `ado001.hs` in the testsuite: {{{ test11 :: M () test11 = do x1 <- a let x2 = x1 x3 <- b let x4 = c x5 = x4 return (const () (x1,x2,x3,x4)) }}} Which should give `(a | b)`, but gives `(a ; b)` in 8.0.1 RC. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11612> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13328: Foldable, Functor, and Traversable deriving handle phantom types badly
by GHC 30 Mar '17

30 Mar '17

#13328: Foldable, Functor, and Traversable deriving handle phantom types badly -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.1 Keywords: deriving-perf | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Suppose we have {{{#!hs data Phantom a = Z | S (Phantom a) }}} We'd like to get something like {{{#!hs foldMap _ _ = mempty fmap = coerce traverse _ m = pure (coerce m) }}} But instead we actually pattern match all the way down! Basically, we want to treat "has a phantom role" and "does not occur" similarly. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13328> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8501: Improve error message when using rec/mdo keyword without RecursiveDo extention.
by GHC 29 Mar '17

29 Mar '17

#8501: Improve error message when using rec/mdo keyword without RecursiveDo extention. -------------------------------------+------------------------------------- Reporter: shelarcy | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Parser) | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #3968 | -------------------------------------+------------------------------------- GHC shows unhelpful error message when using rec keyword and/or mdo keyword without RecursiveDo extention. {{{ module NoRecursiveDo where foo = do rec str <- return "foo" putStrLn str }}} {{{ $ ghc -c NoRecursiveDo.hs NoRecursiveDo1.hs:4:5: Parse error in pattern: rec }}} {{{ module NoRecursiveDo2 where bar = mdo str <- return "bar" putStrLn str }}} {{{ $ ghc -c NoRecursiveDo2.hs NoRecursiveDo2.hs:4:9: parse error on input `<-' }}} {{{ module NoRecursiveDo3 where baz = mdo putStrLn "baz" }}} {{{ $ ghc -c NoRecursiveDo3.hs NoRecursiveDo3.hs:3:7: Not in scope: `mdo' Perhaps you meant `mod' (imported from Prelude) }}} I think that GHC should suggest to use RecursiveDo extention when using mdo/rec keyword. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8501> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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