May 2016 - ghc-tickets

[GHC] #8865: Cannot derive well-kinded instance of form ‘Category
by GHC 03 May '16

03 May '16

#8865: Cannot derive well-kinded instance of form ‘Category ----------------------------+---------------------------------------------- Reporter: | Owner: adinapoli | Status: new Type: bug | Milestone: 7.8.1 Priority: normal | Version: 7.8.1-rc2 Component: Compiler | Operating System: MacOS X Keywords: | Type of failure: GHC rejects valid program Architecture: x86_64 | Test Case: (amd64) | Blocking: Difficulty: Unknown | Blocked By: | Related Tickets: | ----------------------------+---------------------------------------------- Hello everyone, sorry if this was already reported somewhere. I'm playing with GHC 7.8.1 RC2 and I'm updating hsenv to support GHC 7.8. This is a real code snippet, which was compiling fine in GHC 7.6.x {{{ newtype ArgArrow a b = ArgArrow (StaticArrowT KnownArgs (Kleisli (ReaderT Args IO)) a b) deriving (Category, Arrow, ArrowChoice) }}} but that yields the following in GHC 7.8.1-RC2 {{{ Cannot derive well-kinded instance of form ‘Category (ArgArrow ...)’ Class ‘Category’ expects an argument of kind ‘k -> k -> *’ In the newtype declaration for ‘ArgArrow’ }}} This might be related to the new feature of GHC 7.8, namely "kind variables" (you get the idea, even if the name is not 100% accurate). To make the code compile I had to enable {{{ StandaloneDeriving }}} and write the following: {{{ newtype ArgArrow a b = ArgArrow (StaticArrowT KnownArgs (Kleisli (ReaderT Args IO)) a b) deriving (Arrow, ArrowChoice) deriving instance Category ArgArrow }}} Is this by design or is a genuine bug? Thanks! Alfredo -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8865> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10266: Split base for Backpack
by GHC 03 May '16

03 May '16

#10266: Split base for Backpack -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: task | Status: new Priority: normal | Milestone: Component: | Version: 7.11 libraries/base | Operating System: Unknown/Multiple Keywords: backpack | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Let's resurrect #1338 and #1580. Our new concrete goal is to have users be able to replace 'base' with 'base-sig', which is some signature representing the modules from 'base' which we depend on. Since 'base' is a big, complicated package, the ability to specify subsets of 'base' is very useful: it can be used to define things like Haskell'98 base, base without any unsafe operations, etc. Right now, all wired in things live in ghc-prim (I believe). This is good, since we can't reasonably abstract wired in things away with a signature: GHC will always put them in some well-known place. However, this is not enough: there are many known-key/Rdr things the compiler knows about too, which need to be placed in specific package + module locations for GHC to be able to reference them; e.g. when deriving instances, etc. At the moment, most of these identifiers live in 'base', which is no good. So, here's the proposal: all non-rebindable GHC-known identifiers (as per PrelNames) should be moved to ghc-prim (or perhaps a new package? I don't really care either way) and reexported from the old packages which they were available from base. I'll try to work out in detail what moves, how to avoid orphan instances, etc. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10266> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11985: Core lint error on record syntax update/pattern synonym
by GHC 02 May '16

02 May '16

#11985: Core lint error on record syntax update/pattern synonym -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While on a flight I discovered some errors, if you load a file using record syntax for pattern synonyms: {{{#!hs module Foo where pattern Pair{x, y} = (x, y) }}} and load it with `-dcore-lint`: {{{ $ ghci -dcore-lint -ignore-dot-ghci -XPatternSynonyms /tmp/Foo.hs GHCi, version 8.1.20160419: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Foo ( /tmp/Foo.hs, interpreted ) Ok, modules loaded: Foo. *Foo> (1, 2) { x = 10 } *** Core Lint errors : in result of desugar expression *** [...] }}} full error message attached. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11985> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11983: Can't use IntPtr or WordPtr in a foreign import
by GHC 02 May '16

02 May '16

#11983: Can't use IntPtr or WordPtr in a foreign import -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: RyanGlScott Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 (FFI) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: #3008, #5529 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Despite the [http://hackage.haskell.org/package/base-4.8.2.0/docs/Foreign- Ptr.html#t:IntPtr docs claiming] that you can use `IntPtr` and `WordPtr` to convert to and from `intptr_t` and `uintptr_t`, you can't actually do so in a `foreign import` as of GHC 7.6. Here's a minimal example: {{{#!hs -- Example.hs {-# LANGUAGE ForeignFunctionInterface #-} module Example where {-# INCLUDE example.h #-} import Foreign.Ptr foreign import ccall "intptr_example" intPtrExample :: IntPtr -> IO () foreign import ccall "uintptr_example" wordPtrExample :: WordPtr -> IO () }}} {{{#!c // example.h #ifndef EXAMPLE_H #define EXAMPLE_H #include <stdint.h> void intptr_example(intptr_t); void uintptr_example(uintptr_t); #endif // EXAMPLE_H }}} {{{#!c // example.c #include <stdint.h> #include "example.h" void intptr_example(intptr_t i) {} void uintptr_example(uintptr_t u) {} }}} This appears to be a consequence of #3008, which prevents `newtype`s from being used as FFI types unless their constructors are exported. #5529 fixed this problem for the datatypes in `Foreign.C.Types` and `System.Posix.Types` by simply exporting their constructors, so I think all that's needed to fix this particular example is to export the constructors for `IntPtr` and `WordPtr`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11983> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5850: Greater customization of GHCi prompt
by GHC 02 May '16

02 May '16

#5850: Greater customization of GHCi prompt -------------------------------------+------------------------------------- Reporter: JamesFisher | Owner: niksaz Type: feature request | Status: closed Priority: normal | Milestone: 8.2.1 Component: GHCi | Version: 7.4.1 Resolution: fixed | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #9994 | Differential Rev(s): Phab:D2084 Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * status: new => closed * resolution: => fixed * milestone: => 8.2.1 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5850#comment:19> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11965: USE_PTHREAD_FOR_ITIMER causes unnecessary wake-ups
by GHC 02 May '16

02 May '16

#11965: USE_PTHREAD_FOR_ITIMER causes unnecessary wake-ups -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Runtime | Version: 7.10.3 System | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: #1623 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The `USE_PTHREAD_FOR_ITIMER` path appears to regress #1623 as it has no ability to disarm the timer when the ticker is in the `STOPPED` state. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11965> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10520: RecordWildCards causes “is not a (visible) field of constructor” in ghci
by GHC 02 May '16

02 May '16

#10520: RecordWildCards causes “is not a (visible) field of constructor” in ghci -------------------------------------+------------------------------------- Reporter: ion1 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.10.1 Keywords: | Operating System: Linux RecordWildCards | Type of failure: GHC rejects Architecture: x86_64 | valid program (amd64) | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- {{{ % ghc -ignore-dot-ghci -e 'data Foo = Bar { baz :: Integer } deriving Show' -e 'Bar 42' -e '(Bar 42){ baz = 43 }' -e 'Bar { baz = 42 }' Bar {baz = 42} Bar {baz = 43} Bar {baz = 42} }}} {{{ % ghc -ignore-dot-ghci -XRecordWildCards -e 'data Foo = Bar { baz :: Integer } deriving Show' -e 'Bar 42' -e '(Bar 42){ baz = 43 }' -e 'Bar { baz = 42 }' Bar {baz = 42} Bar {baz = 43} <interactive>:1:7: ‘baz’ is not a (visible) field of constructor ‘Bar’ }}} {{{ % ghc --version The Glorious Glasgow Haskell Compilation System, version 7.10.1 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10520> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4012: Compilation results are not deterministic
by GHC 02 May '16

02 May '16

#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: 11362 | Blocking: Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, | Phab:D1268, Phab:D1360, Phab:D1373, Wiki Page: | Phab:D1396, Phab:D1457, Phab:D1468, DeterministicBuilds | Phab:D1487, Phab:D1504, Phab:D1508 -------------------------------------+------------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"ea34f565d370404f9ea5f8bcf6a8380ffa842c49/ghc" ea34f565/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="ea34f565d370404f9ea5f8bcf6a8380ffa842c49" Remove unused equivClassesByUniq It uses `eltsUFM` so it can introduce nondeterminism, but it isn't used so we can delete it. Test Plan: it builds Reviewers: simonpj, goldfire, simonmar, austin, bgamari Reviewed By: austin, bgamari Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2161 GHC Trac Issues: #4012 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:157> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5529: Newtypes with hidden constructors cannot be passed as FFI arguments
by GHC 02 May '16

02 May '16

#5529: Newtypes with hidden constructors cannot be passed as FFI arguments ---------------------------------------+--------------------------------- Reporter: mikhail.vorozhtsov | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: ---------------------------------------+--------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"a28611b14930c9fd73b0028857e1ea8c0e64a38a/ghc" a28611b/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="a28611b14930c9fd73b0028857e1ea8c0e64a38a" Export constructors for IntPtr and WordPtr This finishes what #5529 started by exporting the constructors for `IntPtr` and `WordPtr` from `Foreign.Ptr`, allowing them to be used in `foreign` declarations. Fixes #11983. Test Plan: `make TEST=T11983` Reviewers: simonpj, hvr, bgamari, austin Reviewed By: simonpj Subscribers: simonpj, thomie Differential Revision: https://phabricator.haskell.org/D2142 GHC Trac Issues: #11983 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5529#comment:16> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11747: `Strict` causes core lint error
by GHC 02 May '16

02 May '16

#11747: `Strict` causes core lint error -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: Strict | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ $ ghci -dcore-lint -XStrict -XGADTs -XRankNTypes -XTypeApplications -XScopedTypeVariables -ignore-dot-ghci GHCi, version 8.1.20160117: http://www.haskell.org/ghc/ :? for help Prelude> import Data.Typeable Prelude Data.Typeable> let zero :: forall x. Typeable x => Maybe x; zero = do Refl <- eqT @Int @x; pure 0 Prelude Data.Typeable> zero *** Core Lint errors : in result of desugar expression *** <no location info>: warning: In the expression: ds_d1t9 @ x_a1sx $dTypeable_a1sC @ x_a1sx $dTypeable_a1sz $dTypeable_a1sz :: Typeable x_a1sx [LclId, Str=DmdType] is out of scope *** Offending Program *** let { $dTypeable_a1sS :: Typeable () [LclId, Str=DmdType] $dTypeable_a1sS = D:Typeable @ * @ () (let { ds_d1tb :: TypeRep [LclId, Str=DmdType] ds_d1tb = mkPolyTyConApp $tc() ([] @ TypeRep) ([] @ TypeRep) } in \ (wild_00 :: Proxy# ()) -> ds_d1tb) } in let { $dShow_a1sU :: Show () [LclId, Str=DmdType] $dShow_a1sU = $fShow() } in let { $dShow_a1sP :: Show (Maybe ()) [LclId, Str=DmdType] $dShow_a1sP = $fShowMaybe @ () $dShow_a1sU } in letrec { ds_d1t9 :: forall x_a1sx. Typeable x_a1sx => forall x_a11P. Typeable x_a11P => Maybe x_a11P [LclId, Str=DmdType] ds_d1t9 = \ (@ x_a1sx) ($dTypeable_a1sC :: Typeable x_a1sx) -> let { $dTypeable_a1sz :: Typeable x_a1sx [LclId, Str=DmdType] $dTypeable_a1sz = $dTypeable_a1sC } in letrec { it_a1sw :: forall x_a11P. Typeable x_a11P => Maybe x_a11P [LclId, Str=DmdType] it_a1sw = zero; } in it_a1sw; it_a1dz :: forall x_a1sx. Typeable x_a1sx => Maybe x_a1sx [LclId, Str=DmdType] it_a1dz = \ (@ x_a1sx) ($dTypeable_a1sC :: Typeable x_a1sx) -> ds_d1t9 @ x_a1sx $dTypeable_a1sC @ x_a1sx $dTypeable_a1sz; } in case it_a1dz of it_a1dz { __DEFAULT -> thenIO @ () @ [()] (print @ (Maybe ()) $dShow_a1sP (it_a1dz @ () $dTypeable_a1sS)) (returnIO @ [()] (: @ () (unsafeCoerce# @ 'Lifted @ 'Lifted @ (forall x_a1sx. Typeable x_a1sx => Maybe x_a1sx) @ () it_a1dz) ([] @ ()))) } *** End of Offense *** <no location info>: error: Compilation had errors *** Exception: ExitFailure 1 Prelude Data.Typeable> }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11747> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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