[GHC] #7669: Empty case causes warning
#7669: Empty case causes warning ----------------------------------------------+----------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.7 | Keywords: EmptyCase Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Blockedby: Blocking: | Related: ----------------------------------------------+----------------------------- The following code {{{ {-# LANGUAGE EmptyCase #-} {-# OPTIONS_GHC -fwarn-incomplete-patterns #-} data Void foo :: Void -> () foo x = case x of {} }}} causes this warning {{{ /Users/rae/temp/Scratch.hs:6:9: Warning: Pattern match(es) are non-exhaustive In a case alternative: Patterns not matched: Ok, modules loaded: Main. }}} -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7669 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#7669: Empty case causes warning
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Reporter: goldfire | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.7 | Keywords: EmptyCase
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Incorrect warning at compile-time | Blockedby:
Blocking: | Related:
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Comment(by simonpj@…):
commit 9162d159a62d19d4b371b7348eb1b524001fddcd
{{{
Author: Simon Peyton Jones
#7669: Empty case causes warning ------------------------------------------------+--------------------------- Reporter: goldfire | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: fixed | Keywords: EmptyCase Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Difficulty: Unknown Testcase: deSugar/should_compile/T7669 | Blockedby: Blocking: | Related: ------------------------------------------------+--------------------------- Changes (by simonpj): * status: new => closed * difficulty: => Unknown * resolution: => fixed * testcase: => deSugar/should_compile/T7669 Comment: Thanks. Turns out I could cure this ''and'' make the code simpler! Simon -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7669#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#7669: Empty case causes warning ------------------------------------------------+--------------------------- Reporter: goldfire | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: fixed | Keywords: EmptyCase Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Difficulty: Unknown Testcase: deSugar/should_compile/T7669 | Blockedby: Blocking: | Related: ------------------------------------------------+--------------------------- Comment(by monoidal): However, previously empty case always gave a warning; now it never does. {{{ f :: Bool -> a f x = case x of { } }}} -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7669#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#7669: Empty case causes warning ------------------------------------------------+--------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: EmptyCase Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Difficulty: Unknown Testcase: deSugar/should_compile/T7669 | Blockedby: Blocking: | Related: ------------------------------------------------+--------------------------- Changes (by simonpj): * status: closed => new * resolution: fixed => Comment: Very true. Would anyone like to look at the overlapping-pattern warnings? It's a well-defined problem, restricted to a single module in GHC (`deSugar/Check.lhs`). We have a bunch of tickets about it: at least #595, #5728, #3927, #5724, #5762, #4139, #6124. A lovely project awaits! Meanwhile I think I'll leave the code in its simplified state. Simon -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7669#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#7669: Empty case causes warning ------------------------------------------------+--------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: 7.7 Resolution: | Keywords: EmptyCase Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Difficulty: Unknown Testcase: deSugar/should_compile/T7669 | Blockedby: Blocking: | Related: ------------------------------------------------+--------------------------- Changes (by igloo): * milestone: => 7.8.1 -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7669#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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