August 2016 - ghc-tickets

[GHC] #12170: Add flag to control whether out of scope variables should be deferred with -fdefer-typed-holes
by GHC 01 Sep '16

01 Sep '16

#12170: Add flag to control whether out of scope variables should be deferred with -fdefer-typed-holes -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: newcomer | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #10569 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- As a result of #10569, out of scope variables are turned into special type holes so that type information of the variable can be attached to the error message. However, this causes problems when used with `-fdefer-typed-holes` as scope errors have been turned into type errors and are now deferred when using this flag. Richard sums up the situation, "Even if someone is deferring type errors, I imagine most people don't want to defer scope errors". It would be good to add a flag which controls whether out of scope variables are also deferrable when used with existing deferral flags. Goal: Add a flag ` -fdefer-out-of-scope-variables` which controls whether out of scope variables are deferred when using `-fdefer-typed-holes`. It should be turned off by default. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12170> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12491: ghc-iserv pattern match failure
by GHC 01 Sep '16

01 Sep '16

#12491: ghc-iserv pattern match failure -------------------------------------+------------------------------------- Reporter: erikd | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.1 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: -------------------------------------+------------------------------------- While trying to debug the issue in https://ghc.haskell.org/trac/ghc/ticket/11981#comment:10 I found that that `ghc-iserv` executable run without any arguments fails with a pattern match failure: {{{ $ inplace/lib/bin/ghc-iserv ghc-iserv: user error (Pattern match failure in do expression at iserv/src/Main.hs:28:3-18) }}} Would be far nicer if it printed out an error message saying what arguments it expected, or how to run it to avoid this pattern match failure. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12491> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12040: Code that builds on 7.8.4 and 7.10.3 but fails with requiring UndecidableInstances on 8.0.1-rc4
by GHC 31 Aug '16

31 Aug '16

#12040: Code that builds on 7.8.4 and 7.10.3 but fails with requiring UndecidableInstances on 8.0.1-rc4 -------------------------------------+------------------------------------- Reporter: dmcclean | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- (I am not sure if this is an issue with the release candidate or with my code. I'm sorry, I've tried hard to investigate that but not come to a firm conclusion. I'm reporting it on the chance that it might be an issue with the release candidate.) The code at https://github.com/bjornbm/dimensional/tree/c5b41bbcecb710d566f8af6e561dcaf… builds and passes tests on 7.8.4 and 7.10.3. The same code fails under 8.0.1-rc4 with the following message: {{{ src/Numeric/Units/Dimensional/Dynamic.hs:79:10: error: • The constraint ‘KnownDimension d’ is no smaller than the instance head (Use UndecidableInstances to permit this) • In the instance declaration for ‘Demotable (Quantity d)’ }}} I'm not sure if the relationship here between `Demotable`, `KnownDimension`, `HasDimension`, and `HasDynamicDimension` in fact requires undecidable instances (in which case 7.8.4 and 7.10.3 are either allowing it in error? or helpfully allowing it even though they aren't obligated to?) or if it does not in fact require undecidable instances (in which case 8.0.1-rc4 is disallowing it in error). Making things even more interesting, a new feature branch of the same project doesn't appear to change any of the things that should be relevant to this error message, but compiles and tests without the error on 8.0.1-rc4 as well as the earlier compiler versions. That one's at https://github.com/dmcclean/dimensional/tree/9f3b0a207258851964defd90ce497e…. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12040> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12358: Read1/Read2 don't have methods defined in terms of ReadPrec
by GHC 31 Aug '16

31 Aug '16

#12358: Read1/Read2 don't have methods defined in terms of ReadPrec -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: feature | Status: new request | Priority: normal | Milestone: 8.2.1 Component: | Version: 8.0.1 libraries/base | 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: -------------------------------------+------------------------------------- Original Haskell libraries mailing list discussion: https://mail.haskell.org/pipermail/libraries/2016-June/027102.html > GHC 8.0 added the [http://hackage.haskell.org/package/base-4.9.0.0/docs /Data-Functor-Classes.html Data.Functor.Classes] module to `base`, and with it the `Read1` and `Read2` typeclasses. The current definition of `Read1` is this: > > {{{#!hs > class Read1 f where > liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (f a) > liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [f a] > }}} > > There's a pretty big problem with this definition: it uses `ReadS` (a synonym for `String -> [(a, String)]`). This sort of parser is very slow (the docs even [http://hackage.haskell.org/package/base-4.9.0.0/docs/Text- ParserCombinators-ReadP.html#t:ReadS admit as such]), and moreover, the actual `Read` typeclass on which Read1 is based tries to avoid using it whenever possible. > > The `Read` typeclass has this definition currently: > > {{{#!hs > class Read a where > readsPrec :: Int -> ReadS a > readList :: ReadS [a] > readPrec :: ReadPrec a > readListPrec :: ReadPrec [a] > }}} > > Where `ReadPrec` is a much more efficient parser datatype. When deriving `Read` instances, GHC defines them in terms of `readPrec`, and gives the other methods default definitions that leverage `readPrec`. > > For the sake of consistency, I propose adding analogous methods to `Read1` and `Read2` that use the `ReadPrec` datatype. For example, here is how I would change `Read1`: > > {{{#!hs > class Read1 f where > liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (f a) > liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [f a] > liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (f a) > liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [f a] > }}} > > And similarly for `Read2`. Here is a [https://gist.github.com/RyanGlScott/7cdd11d6aa878e4229acf1a682beb1fc full gist] with a sketch of what the new `Read1`/`Read2` definitions would look like, including what the default definitions of the other methods would be. Diff coming soon. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12358> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7259: Eta expansion of products in System FC
by GHC 30 Aug '16

30 Aug '16

#7259: Eta expansion of products in System FC -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by Iceland_jack): * cc: Iceland_jack (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7259#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12460: Solaris linker does not recognize option --gc-sections
by GHC 30 Aug '16

30 Aug '16

#12460: Solaris linker does not recognize option --gc-sections ------------------------------------------+---------------------------- Reporter: herzen | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Linking) | Version: 8.0.1 Keywords: | Operating System: Solaris Architecture: Unknown/Multiple | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ------------------------------------------+---------------------------- Linking helloworld.hs fails with the error ld: fatal: unrecognized option '--' If gcc is called by hand to link with "-Wl,--gc-sections" removed, the link succeeds. $ ghc --version The Glorious Glasgow Haskell Compilation System, version 8.0.1 $ uname -a SunOS diotima 5.11 11.3 i86pc i386 i86pc $ gcc --version gcc (GCC) 4.9.3 $ cat helloworld.hs main = putStrLn "hello, world" $ ghc -c helloworld.hs $ ghc -v -keep-tmp-files -o helloworld helloworld.o Glasgow Haskell Compiler, Version 8.0.1, stage 2 booted by GHC version 7.10.1 Using binary package database: /usr/lib/ghc-8.0.1/package.conf.d/package.cache loading package database /usr/lib/ghc-8.0.1/package.conf.d wired-in package ghc-prim mapped to ghc-prim-0.5.0.0 wired-in package integer-gmp mapped to integer-gmp-1.0.0.1 wired-in package base mapped to base-4.9.0.0 wired-in package rts mapped to rts wired-in package template-haskell mapped to template-haskell-2.11.0.0 wired-in package ghc mapped to ghc-8.0.1 wired-in package dph-seq not found. wired-in package dph-par not found. Hsc static flags: Created temporary directory: /tmp/ghc5103_0 *** C Compiler: gcc -U__i686 -fno-stack-protector -DTABLES_NEXT_TO_CODE -c /tmp/ghc5103_0/ghc_1.c -o /tmp/ghc5103_0/ghc_2.o -I/usr/lib/ghc-8.0.1/include *** Linker: gcc -U__i686 -fno-stack-protector -DTABLES_NEXT_TO_CODE -o helloworld -Wl ,--gc-sections helloworld.o -L/usr/lib/ghc-8.0.1/base-4.9.0.0 -L/usr/lib/ghc-8.0.1/integer-gmp-1.0.0.1 -L/usr/lib/ -L/usr/lib/ghc-8.0.1 /ghc-prim-0.5.0.0 -L/usr/lib/ghc-8.0.1/rts /tmp/ghc5103_0/ghc_2.o -Wl,-u,ghczmprim_GHCziTypes_Izh_static_info -Wl,-u,ghczmprim_GHCziTypes_Czh_static_info -Wl,-u,ghczmprim_GHCziTypes_Fzh_static_info -Wl,-u,ghczmprim_GHCziTypes_Dzh_static_info -Wl,-u,base_GHCziPtr_Ptr_static_info -Wl,-u,ghczmprim_GHCziTypes_Wzh_static_info -Wl,-u,base_GHCziInt_I8zh_static_info -Wl,-u,base_GHCziInt_I16zh_static_info -Wl,-u,base_GHCziInt_I32zh_static_info -Wl,-u,base_GHCziInt_I64zh_static_info -Wl,-u,base_GHCziWord_W8zh_static_info -Wl,-u,base_GHCziWord_W16zh_static_info -Wl,-u,base_GHCziWord_W32zh_static_info -Wl,-u,base_GHCziWord_W64zh_static_info -Wl,-u,base_GHCziStable_StablePtr_static_info -Wl,-u,ghczmprim_GHCziTypes_Izh_con_info -Wl,-u,ghczmprim_GHCziTypes_Czh_con_info -Wl,-u,ghczmprim_GHCziTypes_Fzh_con_info -Wl,-u,ghczmprim_GHCziTypes_Dzh_con_info -Wl,-u,base_GHCziPtr_Ptr_con_info -Wl,-u,base_GHCziPtr_FunPtr_con_info -Wl,-u,base_GHCziStable_StablePtr_con_info -Wl,-u,ghczmprim_GHCziTypes_False_closure -Wl,-u,ghczmprim_GHCziTypes_True_closure -Wl,-u,base_GHCziPack_unpackCString_closure -Wl,-u,base_GHCziIOziException_stackOverflow_closure -Wl,-u,base_GHCziIOziException_heapOverflow_closure -Wl,-u,base_ControlziExceptionziBase_nonTermination_closure -Wl,-u,base_GHCziIOziException_blockedIndefinitelyOnMVar_closure -Wl,-u,base_GHCziIOziException_blockedIndefinitelyOnSTM_closure -Wl,-u,base_GHCziIOziException_allocationLimitExceeded_closure -Wl,-u,base_ControlziExceptionziBase_nestedAtomically_closure -Wl,-u,base_GHCziEventziThread_blockedOnBadFD_closure -Wl,-u,base_GHCziWeak_runFinalizzerBatch_closure -Wl,-u,base_GHCziTopHandler_flushStdHandles_closure -Wl,-u,base_GHCziTopHandler_runIO_closure -Wl,-u,base_GHCziTopHandler_runNonIO_closure -Wl,-u,base_GHCziConcziIO_ensureIOManagerIsRunning_closure -Wl,-u,base_GHCziConcziIO_ioManagerCapabilitiesChanged_closure -Wl,-u,base_GHCziConcziSync_runSparks_closure -Wl,-u,base_GHCziConcziSignal_runHandlersPtr_closure -lHSbase-4.9.0.0 -lHSinteger-gmp-1.0.0.1 -lHSghc-prim-0.5.0.0 -lHSrts -lCffi -lgmp -lm -lrt -ldl ld: fatal: unrecognized option '--' ld: fatal: use the '-z help' option for usage information collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) $ gcc -U__i686 -fno-stack-protector -DTABLES_NEXT_TO_CODE -o helloworld helloworld.o -L/usr/lib/ghc-8.0.1/base-4.9.0.0 -L/usr/lib/ghc-8.0.1 /integer-gmp-1.0.0.1 -L/usr/lib/ -L/usr/lib/ghc-8.0.1/ghc-prim-0.5.0.0 -L/usr/lib/ghc-8.0.1/rts /tmp/ghc5103_0/ghc_2.o -Wl,-u,ghczmprim_GHCziTypes_Izh_static_info -Wl,-u,ghczmprim_GHCziTypes_Czh_static_info -Wl,-u,ghczmprim_GHCziTypes_Fzh_static_info -Wl,-u,ghczmprim_GHCziTypes_Dzh_static_info -Wl,-u,base_GHCziPtr_Ptr_static_info -Wl,-u,ghczmprim_GHCziTypes_Wzh_static_info -Wl,-u,base_GHCziInt_I8zh_static_info -Wl,-u,base_GHCziInt_I16zh_static_info -Wl,-u,base_GHCziInt_I32zh_static_info -Wl,-u,base_GHCziInt_I64zh_static_info -Wl,-u,base_GHCziWord_W8zh_static_info -Wl,-u,base_GHCziWord_W16zh_static_info -Wl,-u,base_GHCziWord_W32zh_static_info -Wl,-u,base_GHCziWord_W64zh_static_info -Wl,-u,base_GHCziStable_StablePtr_static_info -Wl,-u,ghczmprim_GHCziTypes_Izh_con_info -Wl,-u,ghczmprim_GHCziTypes_Czh_con_info -Wl,-u,ghczmprim_GHCziTypes_Fzh_con_info -Wl,-u,ghczmprim_GHCziTypes_Dzh_con_info -Wl,-u,base_GHCziPtr_Ptr_con_info -Wl,-u,base_GHCziPtr_FunPtr_con_info -Wl,-u,base_GHCziStable_StablePtr_con_info -Wl,-u,ghczmprim_GHCziTypes_False_closure -Wl,-u,ghczmprim_GHCziTypes_True_closure -Wl,-u,base_GHCziPack_unpackCString_closure -Wl,-u,base_GHCziIOziException_stackOverflow_closure -Wl,-u,base_GHCziIOziException_heapOverflow_closure -Wl,-u,base_ControlziExceptionziBase_nonTermination_closure -Wl,-u,base_GHCziIOziException_blockedIndefinitelyOnMVar_closure -Wl,-u,base_GHCziIOziException_blockedIndefinitelyOnSTM_closure -Wl,-u,base_GHCziIOziException_allocationLimitExceeded_closure -Wl,-u,base_ControlziExceptionziBase_nestedAtomically_closure -Wl,-u,base_GHCziEventziThread_blockedOnBadFD_closure -Wl,-u,base_GHCziWeak_runFinalizzerBatch_closure -Wl,-u,base_GHCziTopHandler_flushStdHandles_closure -Wl,-u,base_GHCziTopHandler_runIO_closure -Wl,-u,base_GHCziTopHandler_runNonIO_closure -Wl,-u,base_GHCziConcziIO_ensureIOManagerIsRunning_closure -Wl,-u,base_GHCziConcziIO_ioManagerCapabilitiesChanged_closure -Wl,-u,base_GHCziConcziSync_runSparks_closure -Wl,-u,base_GHCziConcziSignal_runHandlersPtr_closure -lHSbase-4.9.0.0 -lHSinteger-gmp-1.0.0.1 -lHSghc-prim-0.5.0.0 -lHSrts -lCffi -lgmp -lm -lrt -ldl $ ./helloworld hello, world -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12460> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12552: Merge OpenBSD linking fix
by GHC 30 Aug '16

30 Aug '16

#12552: Merge OpenBSD linking fix -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: task | Status: new Priority: normal | Milestone: 8.2.1 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: -------------------------------------+------------------------------------- Merge f9aa996f0af59f32dc7b1528ff78be41413a9c27 to `ghc-8.0`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12552> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12531: Holes should be kind-polymorphic
by GHC 30 Aug '16

30 Aug '16

#12531: Holes should be kind-polymorphic -------------------------------------+------------------------------------- Reporter: mniip | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I often use holes while writing long expressions out in GHCi in order to let the typechecker assist me with type inference. Sometimes though I find myself in a situation where I want to use holes near unlifted types and results in kind check messages obscuring the holes or having hole errors not show up at all: {{{#!hs > I# (_ +# 1#) <interactive>:5:5: error: • Couldn't match a lifted type with an unlifted type When matching the kind of ‘Int#’ • In the first argument of ‘(+#)’, namely ‘_’ In the first argument of ‘I#’, namely ‘(_ +# 1#)’ In the expression: I# (_ +# 1#) <interactive>:5:5: error: • Found hole: _ :: Int# • In the first argument of ‘(+#)’, namely ‘_’ In the first argument of ‘I#’, namely ‘(_ +# 1#)’ In the expression: I# (_ +# 1#) • Relevant bindings include it :: Int (bound at <interactive>:5:1) }}} (Don't be deceived, the type of `_` there is actually `Int# |> (TYPE U(hole:{a1qG}, 'IntRep, 'PtrRepLifted)_N)_N`) Perhaps the type of `_` should be `forall r (a :: TYPE r). a` or even `forall k (a :: k). a` instead? This might lead to issues with `-fdefer-typed-holes` but maybe we could at first disallow deferred unlifted-kinded holes? But in theory a hole is just a call to `error` which is representation-polymorphic already. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12531> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12458: Segfault in GHCi runtime type reconstruction
by GHC 30 Aug '16

30 Aug '16

#12458: Segfault in GHCi runtime type reconstruction -------------------------------------+------------------------------------- Reporter: mniip | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHCi crash Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help Prelude> data D a = D Prelude> d = D Prelude> :print d d = (_t1::D a) Prelude> d `seq` () () Segmentation fault (core dumped) }}} This is unrelated to #12449 because we're evaluating `d` which has a proper type and not `_t1`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12458> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12177: Relevant bindings includes shadowed bindings
by GHC 30 Aug '16

30 Aug '16

#12177: Relevant bindings includes shadowed bindings -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | 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: -------------------------------------+------------------------------------- {{{ ezyang@sabre:~$ ghc-8.0 --interactive GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help Prelude> \x -> \x -> _ <interactive>:1:13: error: • Found hole: _ :: t2 Where: ‘t2’ is a rigid type variable bound by the inferred type of it :: t -> t1 -> t2 at <interactive>:1:1 • In the expression: _ In the expression: \ x -> _ In the expression: \ x -> \ x -> _ • Relevant bindings include x :: t1 (bound at <interactive>:1:8) x :: t (bound at <interactive>:1:2) it :: t -> t1 -> t2 (bound at <interactive>:1:1) }}} GHC should not report bindings which are shadowed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12177> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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