February 2017 - ghc-tickets

[GHC] #13154: Standalone-derived anyclass instances aren't as permissive as empty instances
by GHC 11 Jun '18

11 Jun '18

#13154: Standalone-derived anyclass instances aren't as permissive as empty instances -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: RyanGlScott Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Note that these are accepted: {{{#!hs class Foo (a :: TYPE ('TupleRep '[])) instance Foo (a :: TYPE ('TupleRep '[])) instance Foo (##) }}} But if you try to write these same instances using `DeriveAnyClass` and `StandaloneDeriving`, they'll be rejected for no good reason: {{{#!hs deriving instance Foo (a :: TYPE ('TupleRep '[])) {- • Can't make a derived instance of ‘Foo a’: The last argument of the instance must be a data or newtype application -} deriving instance Foo (##) {- • Can't make a derived instance of ‘Foo (# #)’: The last argument of the instance cannot be an unboxed tuple -} }}} The latter error is a vestige of #12512, and should be easy enough to rectify. The former error is a bit tricker to fix, since much of the code in `TcDeriv`/`TcDerivInfer` assumes that the type to which the class is applied to in the instead head is a datatype or newtype `TyCon`. It's apparent that this doesn't hold true in the presence of `DeriveAnyClass`, however, so that code should be refactored to reflect this. For practical reasons, however, it might be best to wait until after #12144 is fixed to tackle this one, since that splits out some logic in `TcDerivInfer` for `DeriveAnyClass` so as to make it no longer rely on the aforementioned `TyCon` invariant. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13154> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11798: Recompiling with -fhpc flag added does nothing
by GHC 10 Jun '18

10 Jun '18

#11798: Recompiling with -fhpc flag added does nothing -------------------------------------+------------------------------------- Reporter: drathier | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: None/Unknown (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When you recompile without modifiying any source code, nothing happens, as expected. The file is already compiled, after all. If you then add the -fhpc flag, it still doesn't recompile, even though it now should generate .tix files. These files are now unexpectedly missing, until the source files are modified or the .o and .hi files are deleted, and the code is recompiled again with the -fhpc flag. reproduce: 1. compile program 2. compile program with -fhpc note: missing .tix file 3. delete .hi and .o files 4. compile program with -fhpc 5. success; .tix file is generated -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11798> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11376: Inconsistent specified type variables among functions and datatypes/classes when using -XTypeApplications
by GHC 08 Jun '18

08 Jun '18

#11376: Inconsistent specified type variables among functions and datatypes/classes when using -XTypeApplications -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: TypeInType | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Originally reported [https://mail.haskell.org/pipermail/ghc- devs/2016-January/010915.html here]. When applying types via `-XTypeApplications`, the type/kind that gets instantiated seems to be different depending on whether you're using functions, datatypes, or typeclasses. Here's an example contrasting functions and datatypes: {{{ $ /opt/ghc/head/bin/ghci GHCi, version 8.1.20160106: http://www.haskell.org/ghc/ :? for help λ> :set -fprint-explicit-kinds -XTypeApplications -XTypeInType λ> data Prox a = Prox λ> prox :: Prox a; prox = Prox λ> :t prox prox :: forall k (a :: k). Prox k a λ> :t prox @Int prox @Int :: Prox * Int λ> :t Prox Prox :: forall k (a :: k). Prox k a λ> :t Prox @Int Prox @Int :: Prox Int a }}} This is the core of the problem: with a function, `Int` seems to be applied to type variable `a`, whereas with data types, `Int` appears to be applied to the kind variable `k`. This confuses me, since `k` wasn't specified anywhere in the definition of `Prox`. Andres Löh also [https://mail.haskell.org/pipermail/ghc- devs/2016-January/010916.html observed] a similar discrepancy between functions and typeclasses: {{{ λ> :set -XScopedTypeVariables λ> class C a where c :: () λ> d :: forall a. C a => (); d = c @_ @a λ> :t d d :: forall k (a :: k). C k a => () λ> :t d @Int d @Int :: C * Int => () λ> :t c c :: forall k (a :: k). C k a => () λ> :t c @Int c @Int :: C Int a => () λ> :t c @_ @Int c @_ @Int :: C * Int => () }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11376> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12023: Problems getting information and kind from GHC.Prim ~#, ~R#, ...
by GHC 07 Jun '18

07 Jun '18

#12023: Problems getting information and kind from GHC.Prim ~#, ~R#, ... -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | 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: -------------------------------------+------------------------------------- {{{ >>> import GHC.Prim >>> :bro GHC.Prim [...] type role (~#) nominal nominal data (~#) (t3 :: a) (t4 :: b) type role ~P# phantom phantom data ~P# (t3 :: a) (t4 :: b) type role (~R#) representational representational data (~R#) (t3 :: a) (t4 :: b) }}} getting the kind of `~`, `~#`, `~~` works fine: {{{ >>> import GHC.Prim >>> import GHC.Types >>> :kind (~) (~) :: k -> k -> Constraint >>> :kind (~#) (~#) :: a -> b -> TYPE 'VoidRep >>> :kind (~~) (~~) :: j -> k -> Constraint }}} but `#` gets incorrectly treated as an operator in `~R#` and `~P#`: {{{ >>> :kind (~R#) <interactive>:1:3: error: Illegal operator ‘#’ in type ‘~R #’ Use TypeOperators to allow operators in types <interactive>:1:3: error: Operator applied to too few arguments: ~R # <interactive>:1:4: error: Not in scope: type constructor or class ‘R’ }}} Furthermore while running `:info` on `~~` and `~#` works fine {{{ >>> :info (~~) class a ~# b => (~~) (a :: j) (b :: k) -- Defined in ‘GHC.Types’ >>> :info (~#) type role (~#) nominal nominal data (~#) (t3 :: a) (t4 :: b) -- Defined in ‘GHC.Prim’ }}} the others don't parse {{{ >>> :info (~) <interactive>:1:2: error: parse error on input ‘~’ >>> :info (~R#) <interactive>:1:2: error: parse error on input ‘~’ >>> :info (~P#) <interactive>:1:2: error: parse error on input ‘~’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12023> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12075: Fails to build on powerpcspe because of inline assembly
by GHC 05 Jun '18

05 Jun '18

#12075: Fails to build on powerpcspe because of inline assembly --------------------------------+---------------------------------------- Reporter: glaubitz | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: powerpc | Type of failure: Building GHC failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------+---------------------------------------- Hello! I'm currently bootstrapping GHC on powerpcspe (e500v2) which is a PowerPC architecture without an FPU but with signal processing extensions (hence SPE). When building GHC on this architecture, it detects the host architecture as powerpc-linux-gnuspe or short "powerpc" which works most of the time. However, GHC contains some inline assembly in rts/StgCRunAsm.s which uses FPU instructions not available on e500v2 CPUs resulting in assembler error, here with GHC 7.10.3: {{{ "inplace/bin/ghc-stage1" -optc-fno-stack-protector -optc-Wall -optc-Wextra -optc-Wstrict-prototypes -optc-Wmissing-prototypes -optc-Wmissing- declarations -optc-Winline -optc-Waggregate-return -optc-Wpointer-arith -optc-Wmissing-noreturn -optc-Wnested-externs -optc-Wredundant-decls -optc-Iincludes -optc-Iincludes/dist -optc-Iincludes/dist- derivedconstants/header -optc-Iincludes/dist-ghcconstants/header -optc- Irts -optc-Irts/dist/build -optc-DCOMPILING_RTS -optc- DUSE_LIBFFI_FOR_ADJUSTORS -optc-fno-strict-aliasing -optc-fno-common -optc-Irts/dist/build/autogen -optc-O2 -optc-fomit-frame-pointer -optc-g -optc-DRtsWay=\"rts_v\" -optc-w -static -H32m -O -lffi -optl-pthread -lffi -optl-pthread -Iincludes -Iincludes/dist -Iincludes/dist- derivedconstants/header -Iincludes/dist-ghcconstants/header -Irts -Irts/dist/build -DCOMPILING_RTS -this-package-key rts -dcmm-lint -i -irts -irts/dist/build -irts/dist/build/autogen -Irts/dist/build -Irts/dist/build/autogen -O2 -c rts/StgCRun.c -o rts/dist/build/StgCRun.o /bin/bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8) /bin/bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8) /tmp/ghcf20d_0/ghc_1.s: Assembler messages: /tmp/ghcf20d_0/ghc_1.s:24:0: Error: unrecognized opcode: `stfd' (...) /tmp/ghcf20d_0/ghc_1.s:67:0: Error: unrecognized opcode: `lfd' /tmp/ghcf20d_0/ghc_1.s:68:0: Error: unrecognized opcode: `lfd' /tmp/ghcf20d_0/ghc_1.s:69:0: Error: unrecognized opcode: `lfd' rts/ghc.mk:236: recipe for target 'rts/dist/build/StgCRun.o' failed make[3]: *** [rts/dist/build/StgCRun.o] Error 1 Makefile:71: recipe for target 'all' failed make[2]: *** [all] Error 2 make[2]: Leaving directory '/usr/src/ghc-7.10.3' dh_auto_build: make -j1 returned exit code 2 debian/rules:109: recipe for target 'override_dh_auto_build' failed make[1]: *** [override_dh_auto_build] Error 2 make[1]: Leaving directory '/usr/src/ghc-7.10.3' debian/rules:47: recipe for target 'binary-arch' failed make: *** [binary-arch] Error 2 (sid2-powerpcspe-sbuild)root@atlantis:/usr/src/ghc-7.10.3# }}} This can be verified by commenting out the assembly which will make the above compile command execute without any problems. Trying to continue compiling GHC will still fail with: {{{ "inplace/bin/ghc-stage1" -static -H32m -O -lffi -optl-pthread -lffi -optl-pthread -Iincludes -Iincludes/dist -Iincludes/dist- derivedconstants/header -Iincludes/dist-ghcconstants/header -Irts -Irts/dist/build -DCOMPILING_RTS -this-package-key rts -dcmm-lint -i -irts -irts/dist/build -irts/dist/build/autogen -Irts/dist/build -Irts/dist/build/autogen -O2 -c rts/HeapStackCheck.cmm -o rts/dist/build/HeapStackCheck.o /bin/bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8) /bin/bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8) /tmp/ghcca51_0/ghc_3.s: Assembler messages: /tmp/ghcca51_0/ghc_3.s:525:0: Error: unrecognized opcode: `lfs' /tmp/ghcca51_0/ghc_3.s:538:0: Error: unrecognized opcode: `lfd' /tmp/ghcca51_0/ghc_3.s:592:0: Error: unrecognized opcode: `stfs' /tmp/ghcca51_0/ghc_3.s:604:0: Error: unrecognized opcode: `stfd' rts/ghc.mk:236: recipe for target 'rts/dist/build/HeapStackCheck.o' failed make[3]: *** [rts/dist/build/HeapStackCheck.o] Error 1 Makefile:71: recipe for target 'all' failed make[2]: *** [all] Error 2 make[2]: Leaving directory '/usr/src/ghc-7.10.3' dh_auto_build: make -j1 returned exit code 2 debian/rules:109: recipe for target 'override_dh_auto_build' failed make[1]: *** [override_dh_auto_build] Error 2 make[1]: Leaving directory '/usr/src/ghc-7.10.3' debian/rules:47: recipe for target 'binary-arch' failed make: *** [binary-arch] Error 2 (sid2-powerpcspe-sbuild)root@atlantis:/usr/src/ghc-7.10.3# }}} So, there is obviously more assembly code that needs to be disabled on powerpcspe. For that, I suggest testing whether the compiler sets __NO_FPRS__which is only set on powerpc hosts without FP registers: {{{ root@atlantis:~# echo | gcc -E -dM -|grep -i FP #define __NO_FPRS__ 1 root@atlantis:~# dpkg --print-architecture powerpcspe root@atlantis:~# uname -m ppc root@atlantis:~# }}} For reference, on a real powerpc host, the output is as follows: {{{ (sid_powerpc-dchroot)glaubitz@partch:~$ echo | gcc -E -dM -|grep -i FP #define __FP_FAST_FMAF 1 #define __FP_FAST_FMA 1 (sid_powerpc-dchroot)glaubitz@partch:~$ dpkg --print-architecture powerpc (sid_powerpc-dchroot)glaubitz@partch:~$ uname -m ppc (sid_powerpc-dchroot)glaubitz@partch:~$ }}} If you need any more input, please let me know. Adrian -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12075> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8516: Add (->) representation and the Invariant class to GHC.Generics
by GHC 04 Jun '18

04 Jun '18

#8516: Add (->) representation and the Invariant class to GHC.Generics ----------------------------------------------+---------------------------- Reporter: nfrisby | Owner: Type: feature request | Status: new Priority: low | Milestone: Component: Compiler (Type checker) | Version: 7.7 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Moderate (less than a day) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: ----------------------------------------------+---------------------------- We currently disallow any use of the parameter in the domain of (->). {{{ newtype F a = F ((a -> Int) -> Int) deriving Generic1 <interactive>:4:38: Can't make a derived instance of `Generic1 (F g)': Constructor `F' must use the last type parameter only as the last argument of a data type, newtype, or (->) In the data declaration for `F' }}} !DeriveFunctor succeeds for this F. I'd like to add this representation type to GHC.Generics and !DeriveGeneric. {{{ newtype (f :->: g) a = FArrow1 (f a -> g a) }}} We could then represent the first example above. We could also derive the more interesting Generic1 (F g). {{{ newtype F g a = F (g a -> Int) deriving Generic1 type instance Rep1 (F g) = Rec1 g :->: Rec0 Int instance Generic1 (F g) where to x = F $ unRec0 . unArrow1 x . Rec1 from (F x) = FArrow1 $ Rec0 . x . unRec1 }}} Admittedly, there's not many generic definitions impeded by not having (:->:). Contra- and in-variant types are uncommon. I'm suggesting this feature without strong motivating examples because I think this would streamline the implementation of -XDeriveGenerics in some ways while also making it more general — assuming that we added the Invariant class to base or ghc-prim. {{{ class Invariant t where invmap :: (a -> b) -> (b -> a) -> t a -> t b invmap_covariant :: Functor t => (a -> b) -> (b -> a) -> t a -> t b invmap_covariant f _ = fmap f instance (Invariant f,Invariant g) => Invariant (FArrow f g) where invmap co contra (FArrow h) = FArrow $ invmap co contra . h . invmap contra co }}} (Of course, Invariant should be a super class of Functor. :/ ) Now we can handle quite involved examples: {{{ newtype F g h a = F (g (h a)) deriving Generic1 instance Invariant g => Generic1 (F g h) where to x = invmap unRec1 Rec1 $ unComp1 x from (F x) = Comp1 $ invmap Rec1 unRec1 }}} All of that said, I'm mostly opening this ticket so I can get feedback on difficulties I might not be anticipating and have a place to reference from the compiler source code comments. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8516> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12152: panic: Loading temp shared object failed
by GHC 03 Jun '18

03 Jun '18

#12152: panic: Loading temp shared object failed -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 (Linking) | Keywords: | Operating System: Linux Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I've attached a no-Haskell-code project that fails when I run `cabal repl` with the following: {{{ ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-unknown-linux): Loading temp shared object failed: /tmp/ghc60744_0/libghc_1.so: undefined symbol: _ZN2Zq1qE }}} Building the project works fine, so the problem seems to be (only) with dynamic linking. The issue can be resolved by swapping the order of the .cpp files in the cabal file. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12152> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9247: Document -XDatatypeContexts in flag reference
by GHC 03 Jun '18

03 Jun '18

#9247: Document -XDatatypeContexts in flag reference ------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: low | Milestone: Component: Documentation | 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: | ------------------------------------+------------------------------------- It may be a deprecated feature, but it still exists and should be listed. I can do this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9247> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11066: Inacessible branch should be warning - otherwise breaks type soundness?
by GHC 03 Jun '18

03 Jun '18

#11066: Inacessible branch should be warning - otherwise breaks type soundness? -------------------------------------+------------------------------------- Reporter: rrnewton | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC 7.10.2 reports inaccessible branches as a type error, and I think this is really a bug. First, the implicit thinking seems to be "why would a user want to write inaccessible cases, they'd be crazy!". But that only applies to human-written code. Program generators can have a great deal of trouble avoiding this error, unless they replicate the GHC type checker to predict the problem and prune branches. (That's why we are hitting this error and are stuck.) Second, it seems like this is a problem for type soundness. See the attached program where "step1" typechecks but "step2" does not. And yet, the operational semantics should allow step1 to reduce to step2. Indeed, in the "GADTs meet their match" paper it seems like the intent was to warn for these inaccessible cases, not error. For example, the paper contains the language: "If we warn that a right-hand side of a non-redundant clause is inaccessible," -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11066> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12939: ghc-8.0.1.20161117 did not install ghc.1 manpage
by GHC 02 Jun '18

02 Jun '18

#12939: ghc-8.0.1.20161117 did not install ghc.1 manpage ----------------------------------------+--------------------------------- Reporter: juhpetersen | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.2 Component: Build System | Version: 8.0.2-rc1 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------------- This seems to be a build regression from ghc-8.0.1. The ghc.1 manpage was not installed for the 8.0.2 RC1 build. I reported this in mail earlier and unfortunately in the meantime lost the buildlogs on Fedora Copr, but since the upstream binary tarballs for Linux also don't seem to contain ghc.1 either it should not be too hard to reproduce. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12939> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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