#5762: GHC gives incorrect warnings with simple applications of the view
patterns
extension
-----------------------------------------------+----------------------------
Reporter: jmg | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.3 | Keywords:
Os: Unknown/Multiple | Architecture:
Unknown/Multiple
Failure: Incorrect warning at compile-time | Testcase:
Blockedby: | Blocking:
Related: |
-----------------------------------------------+----------------------------
GHC is not able to infer exhaustivity of f1 in the following example
{{{
{-# LANGUAGE ViewPatterns #-}
{-# OPTIONS_GHC -fwarn-incomplete-patterns #-}
module VP where
f1, f2 :: Either Int Int -> Either Int Int
f1 (id -> Left _ ) = undefined
f1 (id -> Right _ ) = undefined
f2 (Left _ ) = undefined
f2 (Right _ ) = undefined
f (id -> _) = undefined
}}}
GHC outputs:
{{{
[1 of 1] Compiling VP ( VP.hs, interpreted )
VP.hs:8:1:
Warning: Pattern match(es) are non-exhaustive
In an equation for `f1': Patterns not matched: _
Ok, modules loaded: VP.
}}}
I've tested this with GHC 7.0.4, 7.2.2, and 7.4.1-rc1 on Mac OS X.
BTW: There is neither a version entry for 7.2.2 nor for 7.4.1-rc1 in Trac.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5762>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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