[Haskell-cafe] view patterns

[Dan Licata]

Hi everyone,

Yes, the current overlap checker thinks all view patterns are
overlapped.  The pattern overlap/exhaustiveness checker needs to be
rewritten to account for GADTs and view patterns.

You can use -fno-warn-overlapping-patterns to suppress these warning
(along with any actual overlaps, though, unfortunately).

-Dan

On Nov05, Cale Gibbard wrote:
> 2008/11/5 Cetin Sert <cetin.sert at gmail.com>:
> > <interactive>:1:4:
> >     Warning: Pattern match(es) are overlapped
> >              In the definition of `emp':
> >                  emp ((has -> True)) = ...
> >                  emp ((has -> False)) = ...
> >
> > Why do I get this error in ghc or when I try to compile a file with view
> > patterns?
> > (using -fglasgow-exts  and -XViewPatterns, ghc 6.10.1)
> 
> This is a bug which appears to be known about:
> http://hackage.haskell.org/trac/ghc/ticket/2395
> 
>  - Cale
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