May 2014 - ghc-tickets

Re: [GHC] #4836: literate markdown not handled correctly by unlit
by GHC 19 May '14

19 May '14

#4836: literate markdown not handled correctly by unlit ----------------------------------------------+---------------------------- Reporter: guest | Owner: Type: bug | Status: new Priority: low | Milestone: 7.6.2 Component: Compiler | Version: 7.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects valid program | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: #7120 ----------------------------------------------+---------------------------- Changes (by bjp): * cc: bjp@… (added) * difficulty: => Unknown -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4836#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9035: ghci sometimes displays Word32 as Word64
by GHC 19 May '14

19 May '14

#9035: ghci sometimes displays Word32 as Word64 --------------------------+------------------------------------------------ Reporter: | Owner: MikeIzbicki | Status: new Type: bug | Milestone: Priority: normal | Version: 7.8.2 Component: GHCi | Operating System: Linux Keywords: | Type of failure: Incorrect result at runtime Architecture: x86_64 | Test Case: (amd64) | Blocking: Difficulty: | Unknown | Blocked By: | Related Tickets: | --------------------------+------------------------------------------------ Given this code: {{{ module Main where import Data.Word import Unsafe.Coerce import System.IO nanFloat :: Float nanFloat = unsafeCoerce (maxBound :: Word32) float2word32 :: Float -> Word32 float2word32 = unsafeCoerce nanDouble :: Double nanDouble = unsafeCoerce (maxBound :: Word64) double2word64 :: Double -> Word64 double2word64 = unsafeCoerce main = do putStrLn $ "nanFloat = " ++ show (float2word32 nanFloat) putStrLn $ "nanFloat = " ++ show (float2word32 $ nanFloat + 1) putStrLn $ "nanDouble = " ++ show (double2word64 nanDouble) putStrLn $ "nanDouble = " ++ show (double2word64 $ nanDouble + 1) }}} If we compile with GHC and run, we correctly output: {{{ nanFloat = 4294967295 nanFloat = 4294967295 nanDouble = 18446744073709551615 nanDouble = 18446744073709551615 }}} But if we instead load in ghci, we get the following output: {{{ nanFloat = 4294967295 nanFloat = 140247862083583 nanDouble = 18446744073709551615 nanDouble = 18446744073709551615 }}} For some reason, ghci is displaying (nanFloat+1) as having significantly more digits than can possibly stored in a Word32 value. Test system: Intel Core 2 Duo running Debian with GHC 7.8.2 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9035> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7730: :info and polykinds
by GHC 19 May '14

19 May '14

#7730: :info and polykinds --------------------------------------------+------------------------------ Reporter: monoidal | Owner: archblob Type: bug | Status: patch Priority: normal | Milestone: 7.10.1 Component: Compiler (Type checker) | Version: 7.6.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: #8776 --------------------------------------------+------------------------------ Changes (by archblob): * status: new => patch -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7730#comment:43> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7730: :info and polykinds
by GHC 19 May '14

19 May '14

#7730: :info and polykinds --------------------------------------------+------------------------------ Reporter: monoidal | Owner: archblob Type: bug | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler (Type checker) | Version: 7.6.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: #8776 --------------------------------------------+------------------------------ Comment (by archblob): I have added a working, validated patch. It can be reviewed and I'll make the necessary modification if all is not well. Otherwise I think it can be merged and I've also added tests. It does not include the fix for {{{:kind}}} because I thought it would be best to separate them. I will include another patch for that after we are done with this one. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7730#comment:42> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8673: GHC could generate GADT record selectors in more cases
by GHC 17 May '14

17 May '14

#8673: GHC could generate GADT record selectors in more cases ------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | 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: | ------------------------------------+------------------------------------- Philip Holzenspies writes (in email to ghc-users): I was playing around with GADT-records again and ran into behaviour that I'm not sure is intentional. Given this program: {{{ {-#LANGUAGE GADTs #-} data FooBar x a where Foo :: { fooBar :: a } -> FooBar Char a Bar :: { fooBar :: a } -> FooBar Bool a }}} GHC tells me this: {{{ foo.hs:3:1: Constructors Foo and Bar have a common field `fooBar', but have different result types In the data declaration for `FooBar' Failed, modules loaded: none. }}} The user guide does say (section 7.4.7): "However, for GADTs there is the following additional constraint: every constructor that has a field f must have the same result type (modulo alpha conversion)." So this behaviour is documented in the user guide. However, it seems reasonable that in the case above, where all the relevant variables are exposed in the result type of both constructors, this should be perfectly typeable. In other words, shouldn't GHC be able to derive a type that is simply: {{{ fooBar :: FooBar x a -> a }}} ? Is this something that was simply never implemented, but could be, or is this not decidable or prohibitively computationally complex? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8673> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9108: GADTs and pattern type annotations?
by GHC 17 May '14

17 May '14

#9108: GADTs and pattern type annotations? ------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Consider {{{ {-# LANGUAGE TypeOperators #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE ScopedTypeVariables #-} import Data.Tagged data Sing (xs :: [k]) where SNil :: Sing '[] SCons :: SingI xs => Sing (x ': xs) class SingI (a :: [k]) where sing :: Sing a instance SingI '[] where sing = SNil instance SingI xs => SingI (x ': xs) where sing = SCons lengthSing :: forall (xs :: [k]). SingI xs => Tagged xs Int lengthSing = case sing :: Sing xs of SNil -> Tagged 0 (SCons :: Sing (x ': xs')) -> Tagged (1 + untag (lengthSing :: Tagged xs' Int)) }}} This gives a type error: {{{ Could not deduce (xs ~ (x : xs')) from the context (SingI xs) bound by the type signature for lengthSing :: SingI xs => Tagged xs Int at Bug.hs:23:15-59 ‘xs’ is a rigid type variable bound by the type signature for lengthSing :: SingI xs => Tagged xs Int at Bug.hs:23:22 Expected type: Sing xs Actual type: Sing (x : xs') }}} But once we pattern match on the `SCons` we know that `xs ~ x ': xs'` for some `x`, `xs'`, and we should be able to bring them into scope. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9108> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1600: Optimisation: CPR the results of IO
by GHC 17 May '14

17 May '14

#1600: Optimisation: CPR the results of IO -------------------------------------+------------------------------------- Reporter: simonmar | Owner: nomeata Type: task | Status: new Priority: lowest | Milestone: 7.6.2 Component: Compiler | Version: 6.6.1 Resolution: | Keywords: 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: #8598 -------------------------------------+------------------------------------- Changes (by maoe): * cc: maoe@… (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1600#comment:41> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3693: Show stack traces
by GHC 17 May '14

17 May '14

#3693: Show stack traces -------------------------------------+------------------------------------ Reporter: jpet | Owner: Tarrasch Type: feature request | Status: new Priority: normal | Milestone: 7.10.1 Component: Runtime System | Version: 6.10.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Changes (by maoe): * cc: maoe@… (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3693#comment:70> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1475: Adding imports and exports with Template Haskell
by GHC 15 May '14

15 May '14

#1475: Adding imports and exports with Template Haskell -------------------------------------+------------------------------------ Reporter: igloo | Owner: Type: feature request | Status: new Priority: normal | Milestone: ⊥ Component: Template Haskell | Version: 6.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Changes (by yokto): * cc: silvio.frischi@… (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1475#comment:17> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6018: Injective type families
by GHC 15 May '14

15 May '14

#6018: Injective type families -------------------------------+------------------------------------------- Reporter: lunaris | Owner: simonpj Type: feature | Status: new request | Milestone: 7.10.1 Priority: normal | Version: 7.4.1 Component: Compiler | Keywords: TypeFamilies, Injective Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: #4259 None/Unknown | Test Case: | Blocking: | -------------------------------+------------------------------------------- Comment (by spacekitteh): Here's another real world use case. Given {{{ class Manifold' a where type Field a type Base a type Tangent a type TangentBundle a type Dimension a∷ Nat type UsesMetric a∷ Symbol project ∷ a → Base a unproject ∷ Base a→ a tangent ∷ a → TangentBundle a cotangent ∷ a → (TangentBundle a→ Field a) }}} then this works: {{{ id' ∷ ∀ a. ( Manifold' a) ⇒ Base a → Base a id' input= project out where out∷a out = unproject input }}} whereas this requires injective type families: {{{ id' ∷ ∀ a. ( Manifold' a) ⇒ Base a → Base a id' = project ∘ unproject }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6018#comment:26> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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