November 2017 - ghc-tickets

[GHC] #14349: Semigroup/Monoid instances for System.Exit.ExitCode
by GHC 11 Nov '17

11 Nov '17

#14349: Semigroup/Monoid instances for System.Exit.ExitCode -------------------------------------+------------------------------------- Reporter: neil.mayhew | Owner: (none) Type: feature | Status: new request | Priority: low | Milestone: Component: | Version: 8.2.1 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: -------------------------------------+------------------------------------- Please add instances for ExitCode along the following lines: {{{#!hs instance Monoid ExitCode where mempty = ExitSuccess mappend ExitSuccess b = b mappend a _ = a }}} This allows the summary result of multiple child processes to be computed naturally. For example: {{{#!hs mconcat <$> mapM system commands }}} The result is `ExitSuccess` if they all succeeded, and the leftmost failure otherwise -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14349> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9420: Impredicative type instantiation without -XImpredicativeTypes
by GHC 11 Nov '17

11 Nov '17

#9420: Impredicative type instantiation without -XImpredicativeTypes -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Consider this module: {{{ {-# LANGUAGE RankNTypes #-} module Bug where rank2 :: ((forall a. a -> a) -> b) -> () rank2 _ = () foo :: () -> () foo x = x quux :: (forall a. a -> a) -> Int quux _ = 5 bar = foo . rank2 $ quux }}} The `(.)` in the definition of `bar` requires an impredicative instantiation -- that is, one of its type variables is instantiated to a forall-type. Yet, the module compiles without `-XImpredicativeTypes`. To confirm this behavior, the following is an excerpt from `-ddump-simpl`: {{{ Bug.bar = break<7>() (break<6>() GHC.Base.. @ () @ () @ ((forall a_a1Tj. a_a1Tj -> a_a1Tj) -> GHC.Types.Int) Bug.foo (Bug.rank2 @ GHC.Types.Int)) Bug.quux }}} Note the third type argument to `(.)`. Fixing this would be a breaking change that could affect users. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9420> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14453: CircleCI builds on Linux spuriously fail
by GHC 11 Nov '17

11 Nov '17

#14453: CircleCI builds on Linux spuriously fail -------------------------------------+------------------------------------- Reporter: bgamari | Owner: bgamari Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Continuous | Version: 8.2.1 Integration | 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: -------------------------------------+------------------------------------- See, for instance, [[https://circleci.com/api/v1.1/project/github/ghc/ghc/256/output/107/0?file=… #256]]. This build seemed to be chugging along quite nicely when at minute 30 it failed with, {{{ "inplace/bin/ghc-stage1" -hisuf p_hi -osuf p_o -hcsuf p_hc -static -prof -eventlog -H32m -O -Wall -Iincludes -Iincludes/dist -Iincludes/dist- derivedconstants/header -Iincludes/dist-ghcconstants/header -this-unit- id ghc-8.3 -hide-all-packages -i -icompiler/backpack -icompiler/basicTypes -icompiler/cmm -icompiler/codeGen -icompiler/coreSyn -icompiler/deSugar -icompiler/ghci -icompiler/hsSyn -icompiler/iface -icompiler/llvmGen -icompiler/main -icompiler/nativeGen -icompiler/parser -icompiler/prelude -icompiler/profiling -icompiler/rename -icompiler/simplCore -icompiler/simplStg -icompiler/specialise -icompiler/stgSyn -icompiler/stranal -icompiler/typecheck -icompiler/types -icompiler/utils -icompiler/vectorise -icompiler/stage2/build -Icompiler/stage2/build -icompiler/stage2/build/./autogen -Icompiler/stage2/build/./autogen -Icompiler/. -Icompiler/parser -Icompiler/utils -Icompiler/../rts/dist/build -Icompiler/stage2 -optP-DGHCI -optP-include -optPcompiler/stage2/build/./autogen/cabal_macros.h -package-id base-4.11.0.0 -package-id deepseq-1.4.3.0 -package-id directory-1.3.1.5 -package-id process-1.6.1.0 -package-id bytestring-0.10.8.2 -package-id binary-0.8.5.1 -package-id time-1.8.0.2 -package-id containers-0.5.10.2 -package-id array-0.5.2.0 -package-id filepath-1.4.1.2 -package-id template-haskell-2.13.0.0 -package-id hpc-0.6.0.3 -package-id transformers-0.5.4.0 -package-id ghc-boot-8.3 -package-id ghc-boot-th-8.3 -package-id ghci-8.3 -package-id unix-2.7.2.2 -package-id terminfo-0.4.1.0 -Wall -Wno-name-shadowing -Wnoncanonical-monad-instances -Wnoncanonical- monadfail-instances -Wnoncanonical-monoid-instances -this-unit-id ghc -XHaskell2010 -XNoImplicitPrelude -optc-DTHREADED_RTS -DGHCI_TABLES_NEXT_TO_CODE -DSTAGE=2 -Rghc-timing -O2 -Wcpp-undef -no- user-package-db -rtsopts -Wnoncanonical-monad-instances -odir compiler/stage2/build -hidir compiler/stage2/build -stubdir compiler/stage2/build -c compiler/hsSyn/HsDecls.hs -o compiler/stage2/build/HsDecls.p_o -dyno compiler/stage2/build/HsDecls.dyn_o ... compiler/ghc.mk:447: recipe for target 'compiler/stage2/build/HsDecls.p_o' failed make[1]: *** [compiler/stage2/build/HsDecls.p_o] Killed }}} Why was it killed? No one knows. I suspect it ran out of memory since it appears that there was at least seven other GHC processes running concurrently on a machine with only 4 gigabytes of memory. However, seeing as there's no way to tell whether the OOM killer was invoked it's hard to know for certain. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14453> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #450: "class A where a :: A -> Int" panics GHC 6.4
by GHC 11 Nov '17

11 Nov '17

#450: "class A where a :: A -> Int" panics GHC 6.4 --------------------------------+-------------------- Reporter: carlossch | Owner: nobody Type: bug | Status: closed Priority: normal | Milestone: Component: None | Version: None Resolution: Duplicate | Keywords: Type of failure: None/Unknown | --------------------------------+-------------------- Changes (by Ben Gamari <ben@…>): * failure: => None/Unknown Comment: In [changeset:"5229c43ccf77bcbffeced01dccb27398d017fa34/ghc" 5229c43c/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="5229c43ccf77bcbffeced01dccb27398d017fa34" Squashed 'hadrian/' changes from 438dc576e7..5ebb69ae1e 5ebb69ae1e Drop GccLtXX flags, require GCC > 4.7 and up (#450) git-subtree-dir: hadrian git-subtree-split: 5ebb69ae1eb063f25c59383bffb3b5449015c6f9 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/450#comment:3> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14432: Outdated comment in GHC.Real
by GHC 11 Nov '17

11 Nov '17

#14432: Outdated comment in GHC.Real -------------------------------------+------------------------------------- Reporter: Bodigrim | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Documentation | Version: 8.2.1 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.Real` (lines 518-534) says: {{{ {- Rules for powers with known small exponent ... It might be desirable to have corresponding rules also for exponents of other types, in particular Word, but we can't have those rules here (importing GHC.Word or GHC.Int would create a cyclic module dependency), and it's doubtful they would fire, since the exponents of other types tend to get floated out before the rule has a chance to fire. }}} The remark about cyclic module dependency seems to be outdated: nowadays `GHC.Real` certainly has `Word` in scope. My proposal is to exclude this remark and change the paragraph to {{{ It might be desirable to have corresponding rules also for exponents of other types (e. g., Word), but it's doubtful they would fire, since the exponents of other types tend to get floated out before the rule has a chance to fire. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14432> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2431: Allow empty case analysis
by GHC 11 Nov '17

11 Nov '17

#2431: Allow empty case analysis -----------------------------+--------------------------------------------- Reporter: | Owner: (none) RalfHinze | Type: feature | Status: closed request | Priority: low | Milestone: ⊥ Component: Compiler | Version: 6.8.3 Resolution: fixed | Keywords: empty case analysis Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Type of failure: | Test Case: deSugar/should_compile/T2431 None/Unknown | Blocked By: | Blocking: Related Tickets: | -----------------------------+--------------------------------------------- Changes (by Smartmiltoys): * Attachment "bilets-2018-1.jpg" added. annabelle dollhouses find by [http://smartmiltoys.com/kidkraft-dollhouse /kidkraft-annabelle-dollhouse-65079/ click] this link -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2431> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9642: LANGUAGE pragma synonyms
by GHC 11 Nov '17

11 Nov '17

#9642: LANGUAGE pragma synonyms -------------------------------------+------------------------------------- Reporter: dreixel | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Here are the first 20 lines of a typical Haskell file of mine: {{{ {-# LANGUAGE EmptyDataDecls #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE LiberalTypeSynonyms #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE StandaloneDeriving #-} {-# LANGUAGE AutoDeriveTypeable #-} {-# LANGUAGE DeriveDataTypeable #-} {-# LANGUAGE DeriveGeneric #-} {-# LANGUAGE DefaultSignatures #-} {-# LANGUAGE OverlappingInstances #-} {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE ConstraintKinds #-} }}} Over a couple of modules in a small package, I find myself copy-pasting these 20 lines, as either I will use these extensions, or they won't really cause any harm to the code I'm writing. As a way to simplify this, and reduce code duplication, I propose introducing LANGUAGE pragma synonyms: {{{ {-# LANGUAGE PedrosHaskell = EmptyDataDecls, FlexibleContexts, FlexibleInstances , LiberalTypeSynonyms, ScopedTypeVariables , RankNTypes, StandaloneDeriving, AutoDeriveTypeable , DeriveDataTypeable, DeriveGeneric, DefaultSignatures , OverlappingInstances, UndecidableInstances , MultiParamTypeClasses, TypeOperators, TypeFamilies , GADTs, DataKinds, PolyKinds, ConstraintKinds #-} }}} After writing this, in that same module or any module that imports it, I could just write: {{{ {-# LANGUAGE PedrosHaskell #-} }}} And all the pragmas above would be enabled. Besides making my life easier, I suspect this will also help increase modularity of certain packages. For example, packages could define a package-specific language pragma that should be enabled in order to use that package. Then, if the package maintainer upgrades one datatype to become a GADT, the pragma would be updated to include `GADTs`, and user code (that could now be requiring that pragma) would automatically enable `GADTs` too. Furthermore, it can also make the language standardisation process simpler. After all, {{{ {-# LANGUAGE Haskell2010 = PatternGuards, NoNPlusKPatterns, RelaxedPolyRec , EmptyDataDecls, ForeignFunctionInterface #-} }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9642> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12623: Make Harbormaster less terrible in the face of submodule updates
by GHC 10 Nov '17

10 Nov '17

#12623: Make Harbormaster less terrible in the face of submodule updates -------------------------------------+------------------------------------- Reporter: bgamari | Owner: bgamarii Type: task | Status: new Priority: highest | 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: -------------------------------------+------------------------------------- Currently submodule updates appear to break Harbormaster builds. This is bad. Fix it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12623> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13122: Investigate reporting build errors with harbormaster.sendmessage
by GHC 10 Nov '17

10 Nov '17

#13122: Investigate reporting build errors with harbormaster.sendmessage -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 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: -------------------------------------+------------------------------------- The phabricator API provides a method `harbormaster.sendmessage` which allows builds to report information back so that it is displayed on the interface. The goal is to avoid having to delve into the build logs in order to investigate failures. Information about the API method can be found in [https://phabricator.haskell.org/conduit/method/harbormaster.sendmessage/ conduit]. The API provides a rich set of options to report different information about a build. Some ideas: * Reporting the precise location of all terminal build errors * Reporting the outcome of all tests (this might be quite noisy but the only way to see is to try!) I don't know whether this is a good idea or how it works precisely but integrating harbourmaster with differential would be an efficiency gain. This is potentially related to #8809. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13122> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13121: Investigate whether uploading build artifacts from harbormaster would be usful
by GHC 10 Nov '17

10 Nov '17

#13121: Investigate whether uploading build artifacts from harbormaster would be usful -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: Keywords: newcomer | 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 harbormaster it is possible to upload build artifacts and associate them with each build, for example we could upload the user manual for each build or even binaries. I am not sure what would be useful. One use case might be checking the rendering of the user guide when it is modified. The idea is to write a small utility program which uploads suitable artifacts and then add an extra build step to the relevant build plans which calls this program. The utility doesn't have to be in-tree as it can be installed in the environment. Some more information: * There are some bindings to the phabricator API in [https://github.com /haskell-infra/arc-lite arc-lite] * The relevant API methods are `file.allocate`, `file.upload` and `harbormaster.createartifact` * `file.allocate` allows you to specify a time to delete a file, this would be good to avoid consuming lots of storage for builds. * Artifacts appear in the "artifacts" tab [https://phabricator.haskell.org/harbormaster/build/18367/ here] -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13121> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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