April 2018 - ghc-tickets

[GHC] #8494: Warn if a pattern guard obviates all others
by GHC 03 May '18

03 May '18

#8494: Warn if a pattern guard obviates all others -------------------------+------------------------------------------------- Reporter: | Owner: JohnWiegley | Status: new Type: | Milestone: feature request | Version: 7.6.3 Priority: | Operating System: Unknown/Multiple normal | Type of failure: Incorrect warning at Component: | compile-time Compiler | Test Case: Keywords: | Blocking: Architecture: | Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- The following code, when compiled with `-Wall`, gives no warnings: {{{ module Main where main :: IO () main = print $ foo (10 :: Int) where foo x | True = (20 :: Int) | x == 10 = (30 :: Int) }}} I would expect that since the pattern guard `| True` obviates the following guards, that it would warn about unreachable code. There was a bug in my code today which I tracked down to a code transposition that would have been easily spotted with such a warning. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8494> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9951: OverloadedLists breaks exhaustiveness check
by GHC 03 May '18

03 May '18

#9951: OverloadedLists breaks exhaustiveness check -------------------------------------+------------------------------------- Reporter: Feuerbach | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE OverloadedLists #-} module Bug where f :: [a] -> () f x = case x of [] -> () (_:_) -> () }}} GHC reports: {{{ bug.hs:6:7: Warning: Pattern match(es) are non-exhaustive In a case alternative: Patterns not matched: [] }}} This is reproducible with 7.8 and 7.10rc1. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9951> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10116: Closed type families: Warn if it doesn't handle all cases
by GHC 03 May '18

03 May '18

#10116: Closed type families: Warn if it doesn't handle all cases -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Right now, I can do the following: data Foo = A | B type family Bar (n :: 'Foo) where Bar 'A = Int I would like to be warned if I write a partial type function like this because partial functions are almost always a mistake. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10116> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10393: Bogus warning with OverloadedLists
by GHC 03 May '18

03 May '18

#10393: Bogus warning with OverloadedLists -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- When I say {{{ {-# LANGUAGE OverloadedLists #-} lgo :: [a] -> () lgo [] = () lgo (_:_) = () }}} I get {{{ /Users/rae/temp/Bug.hs:4:1: Warning: Pattern match(es) are non-exhaustive In an equation for ‘lgo’: Patterns not matched: [] }}} I don't know !OverloadedLists deeply, but that warning surely is confusing! Happens on both 7.8.3 and 7.10.1. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10393> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15090: Do more coercion optimisation on the fly
by GHC 03 May '18

03 May '18

#15090: Do more coercion optimisation on the fly -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.2.2 Keywords: Coercions | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When studying #15019, I looked at `CoreOpt.pushCoValArg`. I saw lots of attempted decompositions in `pushCoValArg`, which were trying to do `decomposeFunCo` on {{{ C @g1 ; sym (C @g2) where axiom C a = a -> a }}} But the smart `mkNthCo` can't make progress on this, so we get {{{ Nth:2 (C @g1 ; sym (C @g2)) }}} and these things stack up if there is a chain of applications in `Simplify.simplCast`. The coercion optimiser will optimise this coercion to {{{ (g1 ; sym g2) -> (g1 ; sym g2) }}} and now the smart `mkNthCo` in `decomposeFunCo` will succeed. Possible idea: make this optimization part of `mkTransCo` so that it happens on the fly. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15090> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13091: Build broken on amd64 solaris 11
by GHC 02 May '18

02 May '18

#13091: Build broken on amd64 solaris 11 -------------------------------------+------------------------------------- Reporter: kgardas | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: 8.0.2 Keywords: | Operating System: Solaris Architecture: x86_64 | Type of failure: Building GHC (amd64) | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ ===--- building phase 1 gmake --no-print-directory -f ghc.mk phase=1 phase_1_builds libraries/hpc/ghc.mk:3: libraries/hpc/dist-boot/build/.depend-v.haskell: No such file or directory compiler/ghc.mk:584: compiler/stage1/build/.depend-v.haskell: No such file or directory "/opt/ghc-7.10.2-amd64/bin/ghc" -hisuf hi -osuf o -hcsuf hc -static -H32m -O -Wall -package-db libraries/bootstrapping.conf -hide-all- packages -i -iutils/hsc2hs/. -iutils/hsc2hs/dist/build -iutils/hsc2hs/dist/build/autogen -Iutils/hsc2hs/dist/build -Iutils/hsc2hs/dist/build/autogen -optP-include -optPutils/hsc2hs/dist/build/autogen/cabal_macros.h -package-id base-4.8.1.0-bcc57434d4c4ded429bd4c7561dc7931 -package-id containers-0.5.6.2-3bd9811190df2d727713a53a0942b5c9 -package-id directory-1.2.2.0-17006ecadb146c26f40f44f8704a6547 -package-id filepath-1.4.0.0-8fee9c13b5e42926cc01f6aa7c403c4b -package-id process-1.2.3.0-47082ea082854427d5ceb7c692692d3c -XHaskell2010 -no-user- package-db -rtsopts -odir utils/hsc2hs/dist/build -hidir utils/hsc2hs/dist/build -stubdir utils/hsc2hs/dist/build -c utils/hsc2hs/./Main.hs -o utils/hsc2hs/dist/build/Main.o "/opt/ghc-7.10.2-amd64/bin/ghc" -o utils/hsc2hs/dist/build/tmp/hsc2hs -hisuf hi -osuf o -hcsuf hc -static -H32m -O -Wall -package-db libraries/bootstrapping.conf -hide-all-packages -i -iutils/hsc2hs/. -iutils/hsc2hs/dist/build -iutils/hsc2hs/dist/build/autogen -Iutils/hsc2hs/dist/build -Iutils/hsc2hs/dist/build/autogen -optP- include -optPutils/hsc2hs/dist/build/autogen/cabal_macros.h -package-id base-4.8.1.0-bcc57434d4c4ded429bd4c7561dc7931 -package-id containers-0.5.6.2-3bd9811190df2d727713a53a0942b5c9 -package-id directory-1.2.2.0-17006ecadb146c26f40f44f8704a6547 -package-id filepath-1.4.0.0-8fee9c13b5e42926cc01f6aa7c403c4b -package-id process-1.2.3.0-47082ea082854427d5ceb7c692692d3c -XHaskell2010 -no-user- package-db -rtsopts -odir utils/hsc2hs/dist/build -hidir utils/hsc2hs/dist/build -stubdir utils/hsc2hs/dist/build -optl-optl- Wl,-m64 -static -H32m -O -Wall -package-db libraries/bootstrapping.conf -hide-all-packages -i -iutils/hsc2hs/. -iutils/hsc2hs/dist/build -iutils/hsc2hs/dist/build/autogen -Iutils/hsc2hs/dist/build -Iutils/hsc2hs/dist/build/autogen -optP-include -optPutils/hsc2hs/dist/build/autogen/cabal_macros.h -package-id base-4.8.1.0-bcc57434d4c4ded429bd4c7561dc7931 -package-id containers-0.5.6.2-3bd9811190df2d727713a53a0942b5c9 -package-id directory-1.2.2.0-17006ecadb146c26f40f44f8704a6547 -package-id filepath-1.4.0.0-8fee9c13b5e42926cc01f6aa7c403c4b -package-id process-1.2.3.0-47082ea082854427d5ceb7c692692d3c -XHaskell2010 -no-user- package-db -rtsopts utils/hsc2hs/dist/build/Main.o utils/hsc2hs/dist/build/C.o utils/hsc2hs/dist/build/Common.o utils/hsc2hs/dist/build/CrossCodegen.o utils/hsc2hs/dist/build/DirectCodegen.o utils/hsc2hs/dist/build/Flags.o utils/hsc2hs/dist/build/HSCParser.o utils/hsc2hs/dist/build/UtilsCodegen.o utils/hsc2hs/dist/build/Paths_hsc2hs.o ld: fatal: option '-optl-Wl,-m64' and option '-outils/hsc2hs/dist/build/tmp/hsc2hs' are multiple definitions collect2: error: ld returned 1 exit status gmake[1]: *** [utils/hsc2hs/dist/build/tmp/hsc2hs] Error 1 gmake: *** [all] Error 2 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13091> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11352: Allow applying type to label
by GHC 02 May '18

02 May '18

#11352: Allow applying type to label -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | 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: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE TypeApplications #-} {-# LANGUAGE OverloadedLabels #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE DataKinds #-} import GHC.TypeLits import GHC.OverloadedLabels instance IsLabel "answer" Int where fromLabel _ = 42 answer :: IsLabel "answer" a => a answer = #answer }}} The follow works: {{{#!hs >>> answer @Int 42 }}} but fails with a label: {{{#!hs >>> #answer @Int <interactive>:...:1: error: • Cannot not apply expression of type ‘t0’ to a visible type argument ‘Int’ • In the expression: #answer @Int In an equation for ‘it’: it = #answer @Int }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11352> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15094: unknown symbol `___divmoddi4' error with clock on 32-bit windows
by GHC 02 May '18

02 May '18

#15094: unknown symbol `___divmoddi4' error with clock on 32-bit windows --------------------------------+--------------------------------- Reporter: simonmic | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.2 Keywords: | Operating System: Windows Architecture: x86 | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------+--------------------------------- I got this error when building with 32-bit ghc 8.4.2 on appveyor: {{{ -- While building custom Setup.hs for package hledger-lib-1.9.99 using: C:\sr\setup-exe-cache\i386-windows\Cabal- simple_Z6RU0evB_2.2.0.1_ghc-8.4.2.exe --builddir=.stack-work\dist\ba067387 build lib:hledger-lib --ghc-options " -ddump-hi -ddump-to-file" Process exited with code: ExitFailure 1 Logs have been written to: C:\pr\.stack-work\logs\hledger- lib-1.9.99.log Configuring hledger-lib-1.9.99... Preprocessing library for hledger-lib-1.9.99.. Building library for hledger-lib-1.9.99.. [ 1 of 48] Compiling Hledger.Utils.Color ( Hledger\Utils\Color.hs, .stack-work\dist\ba067387\build\Hledger\Utils\Color.o ) [ 2 of 48] Compiling Hledger.Utils.Test ( Hledger\Utils\Test.hs, .stack-work\dist\ba067387\build\Hledger\Utils\Test.o ) [ 3 of 48] Compiling Hledger.Utils.UTF8IOCompat ( Hledger\Utils\UTF8IOCompat.hs, .stack- work\dist\ba067387\build\Hledger\Utils\UTF8IOCompat.o ) [ 4 of 48] Compiling Hledger.Utils.Regex ( Hledger\Utils\Regex.hs, .stack-work\dist\ba067387\build\Hledger\Utils\Regex.o ) [ 5 of 48] Compiling Hledger.Utils.Tree ( Hledger\Utils\Tree.hs, .stack-work\dist\ba067387\build\Hledger\Utils\Tree.o ) [ 6 of 48] Compiling Hledger.Data.Types ( Hledger\Data\Types.hs, .stack-work\dist\ba067387\build\Hledger\Data\Types.o ) ghc.EXE: unable to load package `clock-0.7.2' ghc.EXE: | C:\sr\snapshots\673e3da0\lib\i386-windows- ghc-8.4.2\clock-0.7.2-Cf9UTsaN2AjEpBnoMpmgkU\HSclock-0.7.2-Cf9UTsaN2AjEpBnoMpmgkU.o: unknown symbol `___divmoddi4' Command exited with code 1 APPVEYOR_SAVE_CACHE_ON_ERROR is set to 'true' - cache will be updated }}} https://ci.appveyor.com/project/simonmichael/hledger/build/master-404 We think this is related: https://github.com/zfsonlinux/zfs/issues/6417 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15094> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14970: GHC.Err.errorWithoutStackTrace produces stack trace when profiling enabled
by GHC 02 May '18

02 May '18

#14970: GHC.Err.errorWithoutStackTrace produces stack trace when profiling enabled -------------------------------------+------------------------------------- Reporter: rotaerk | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 8.2.2 libraries/base | Keywords: | Operating System: Linux Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When you run 'error', it shows the usual stack trace. When you enable profiling with the -prof flag to ghc, and you run 'error', it shows the usual stack trace plus an additional prof-specific stack trace. When you run 'errorWithoutStackTrace' with profiling enabled, it strips the usual stack trace of 'error', but still displays the prof-specific stack trace. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14970> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15102: GHC panic when compiling gi-pango-1.0.15
by GHC 01 May '18

01 May '18

#15102: GHC panic when compiling gi-pango-1.0.15 -------------------------------------+------------------------------------- Reporter: PaulJohnson | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Linux Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I got the following error message: {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.2.2 for x86_64-unknown-linux): tcIfaceGlobal (local): not found You are in a maze of twisty little passages, all alike. While forcing the thunk for TyThing Layout which was lazily initialized by initIfaceCheck typecheckLoop, I tried to tie the knot, but I couldn't find Layout in the current type environment. If you are developing GHC, please read Note [Tying the knot] and Note [Type-checking inside the knot]. Consider rebuilding GHC with profiling for a better stack trace. Contents of current type environment: [] Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1133:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in ghc:Outputable pprPanic, called at compiler/iface/TcIface.hs:1696:23 in ghc:TcIface }}} A self-contained Stack project that demonstrates the problem is attached. I'm using Stack Version 1.6.3 x86_64 hpack-0.20.0 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15102> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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