#4139: Spurious non-exhaustive pattern match warnings are given using GADTs
---------------------------+------------------------------------------------
Reporter: blarsen | Owner: simonpj
Type: bug | Status: closed
Priority: normal | Milestone: 7.0.1
Component: Compiler | Version: 6.12.3
Resolution: invalid | Keywords: GADTs, warnings, pattern matching
Testcase: | Blockedby:
Difficulty: | Os: Unknown/Multiple
Blocking: | Architecture: Unknown/Multiple
Failure: None/Unknown |
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Changes (by simonpj):
* status: new => closed
* resolution: => invalid
Comment:
Now I look at your example, I see that your claim isn't true! Consider
{{{
evalFst (Const (undefined :: Const (Int,Int))
}}}
That will hit the allegedly impossible alternative.
So in this case GHC is quite right. (The pattern match warnings are not
all correct, but this one is, I think.)
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4139#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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