May 2018 - ghc-tickets

[GHC] #15114: ghc 8.4.1 optimizes True to False
by GHC 03 May '18

03 May '18

#15114: ghc 8.4.1 optimizes True to False -------------------------------------+------------------------------------- Reporter: elaforge | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.1 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: -------------------------------------+------------------------------------- Ok, here's a short module: {{{#!hs import qualified Control.Exception as Exception main :: IO () main = do unserialize putStrLn "all is well" unserialize :: IO Char unserialize = if definitelyTrue then do return 'a' else do Exception.evaluate (error "wrong place") {-# NOINLINE definitelyTrue #-} definitelyTrue :: Bool definitelyTrue = True }}} When compiled with -O on 8.4.1, this should print "wrong place". Without -O, or with 8.4.2, or if True can be inlined, or without evaluate, all is well. I can reproduce this on OS X 10.13.4. This could be related to a known bug with Exception.evaluate in 8.4.1: #3930 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15114> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4121: Refactor the plumbing of CafInfo to make it more robust
by GHC 03 May '18

03 May '18

#4121: Refactor the plumbing of CafInfo to make it more robust -------------------------------------+------------------------------------- Reporter: dterei | Owner: (none) Type: task | Status: new Priority: low | Milestone: Component: Compiler | Version: 6.12.2 Resolution: | Keywords: CodeGen, CAFs 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: CodeGen => CodeGen, CAFs -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4121#comment:15> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2204: Improve 'patterns not matched' warnings
by GHC 03 May '18

03 May '18

#2204: Improve 'patterns not matched' warnings -------------------------------------+------------------------------------- Reporter: Deewiant | Owner: (none) Type: feature request | Status: closed Priority: low | Milestone: ⊥ Component: Compiler | Version: 6.8.2 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/2204#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9113: Template Haskell should warn about non-exhaustive pattern matches
by GHC 03 May '18

03 May '18

#9113: Template Haskell should warn about non-exhaustive pattern matches -------------------------+------------------------------------------------- Reporter: tvh | Owner: Type: bug | Status: new Priority: | Milestone: normal | Version: 7.8.2 Component: | Operating System: Unknown/Multiple Template Haskell | Type of failure: Incorrect warning at Keywords: | compile-time Architecture: | Test Case: Unknown/Multiple | Blocking: Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- When using Typed Template Haskell, There are no warings for non-exhaustive patterns inside the quote. {{{ {-# LANGUAGE TemplateHaskell #-} module Foo where import Language.Haskell.TH.Lib foo :: Maybe Int -> TExpQ Bool foo x = [||case x of Nothing -> False||] }}} Instead the warnings appear where the code is spliced. {{{ {-# LANGUAGE TemplateHaskell #-} module Bar where import Foo x = $$(foo (Just 1)) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9113> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8970: Non-exhaustive pattern match warning with DataKinds and TypeFamilies
by GHC 03 May '18

03 May '18

#8970: Non-exhaustive pattern match warning with DataKinds and TypeFamilies ------------------------------------+------------------------------------- Reporter: tensor5 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- The code is: {{{ data K = Foo | Bar data D1 :: K -> * where F1 :: D1 Foo B1 :: D1 Bar class C (a :: K -> *) where data D2 a :: K -> * foo :: a k -> D2 a k -> Bool instance C D1 where data D2 D1 k where F2 :: D2 D1 Foo B2 :: D2 D1 Bar foo F1 F2 = True foo B1 B2 = True }}} With -Wall it gives the warning: {{{ Test.hs:23:5: Warning: Pattern match(es) are non-exhaustive In an equation for `foo': Patterns not matched: F1 B2 B1 F2 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8970> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8853: Alarming looking warning about non-exhaustive pattern
by GHC 03 May '18

03 May '18

#8853: Alarming looking warning about non-exhaustive pattern -------------------------+------------------------------------------------- Reporter: | Owner: MikolajKonarski | Status: new Type: bug | Milestone: Priority: | Version: 7.8.1-rc2 normal | Operating System: Linux Component: | Type of failure: Incorrect warning at Compiler | compile-time Keywords: | Test Case: Architecture: | Blocking: x86_64 (amd64) | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- The attached code produces this alarming warning: ~/waste$ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.8.0.20140228 ~/waste$ ghc -Wall --make AlarmingPattern.hs -fforce-recomp [1 of 1] Compiling Main ( AlarmingPattern.hs, AlarmingPattern.o ) AlarmingPattern.hs:6:7: Warning: Pattern match(es) are non-exhaustive In an equation for ‘takeFromInv’: Patterns not matched: (GHC.Types.I# _) (GHC.Types.I# (#x)) with #x `notElem` [0#] Linking AlarmingPattern ... ~/waste$ ./AlarmingPattern AlarmingPattern: AlarmingPattern.hs:(6,7)-(7,26): Non-exhaustive patterns in function takeFromInv -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8853> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[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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Re: [GHC] #8016: case expression with mixed use of Num instances cause spurious overlap warning
by GHC 03 May '18

03 May '18

#8016: case expression with mixed use of Num instances cause spurious overlap warning -------------------------------------+------------------------------------- Reporter: bscarlet | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Resolution: duplicate | Keywords: case overlap, | 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: case overlap => case overlap, PatternMatchWarnings -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8016#comment:2> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #322: fromInteger-related pattern match overlap warnings
by GHC 03 May '18

03 May '18

#322: fromInteger-related pattern match overlap warnings -------------------------------------+------------------------------------- Reporter: ashley-y | Owner: simonpj Type: bug | Status: closed Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.4 Resolution: duplicate | Keywords: warnings | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: ds060 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/322#comment:13> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6124: Spurious non-exhaustive warning with GADT and newtypes
by GHC 03 May '18

03 May '18

#6124: Spurious non-exhaustive warning with GADT and newtypes -------------------------------------+------------------------------------- Reporter: joeyadams | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: 8.0.1 Component: Compiler (Type | Version: 7.4.1 checker) | Keywords: Resolution: duplicate | 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/6124#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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