May 2018 - ghc-tickets

Re: [GHC] #4139: Spurious non-exhaustive pattern match warnings are given using GADTs
by GHC 03 May '18

03 May '18

#4139: Spurious non-exhaustive pattern match warnings are given using GADTs -------------------------------------+------------------------------------- Reporter: blarsen | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.4.1 Resolution: duplicate | Keywords: GADTs, | warnings, pattern matching, | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: #3927 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: GADTs, warnings, pattern matching => GADTs, warnings, pattern matching, PatternMatchWarnings -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4139#comment:11> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5762: GHC gives incorrect warnings with simple applications of the view patterns extension
by GHC 03 May '18

03 May '18

#5762: GHC gives incorrect warnings with simple applications of the view patterns extension -------------------------------------+------------------------------------- Reporter: jmg | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: ⊥ Component: Compiler | Version: 7.3 Resolution: duplicate | Keywords: | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: => PatternMatchWarnings -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5762#comment:4> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5724: Confusing warning message for incomplete patterns
by GHC 03 May '18

03 May '18

#5724: Confusing warning message for incomplete patterns -------------------------------------+------------------------------------- Reporter: AntoineLatter | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: 7.6.2 Component: Compiler | Version: 7.3 Resolution: duplicate | Keywords: | PatternMatchWarnings 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 simonpj): * keywords: => PatternMatchWarnings -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5724#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3927: Incomplete/overlapped pattern warnings + GADTs = inadequate
by GHC 03 May '18

03 May '18

#3927: Incomplete/overlapped pattern warnings + GADTs = inadequate -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: closed Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 6.12.1 Resolution: duplicate | Keywords: | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #4139 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: => PatternMatchWarnings -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3927#comment:45> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5728: Warnings from -fwarn-incomplete-record-updates even with all constructors matched
by GHC 03 May '18

03 May '18

#5728: Warnings from -fwarn-incomplete-record-updates even with all constructors matched -------------------------------------+------------------------------------- Reporter: mjo | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: ⊥ Component: Compiler | Version: 7.4.1 Resolution: duplicate | Keywords: warnings, | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: warnings => warnings, PatternMatchWarnings -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5728#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #595: Overhaul GHC's overlapping/non-exhaustive pattern checking
by GHC 03 May '18

03 May '18

#595: Overhaul GHC's overlapping/non-exhaustive pattern checking -------------------------------------+------------------------------------- Reporter: simonmar | Owner: (none) Type: task | Status: closed Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: None Resolution: fixed | Keywords: warnings, | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: N/A Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: warnings => warnings, PatternMatchWarnings -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/595#comment:30> 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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