#8016: case expression with mixed use of Num instances cause spurious overlap
warning
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Reporter: bscarlet | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.6.3 | Keywords: case overlap
Os: Unknown/Multiple | Architecture:
Unknown/Multiple
Failure: Incorrect warning at compile-time | Blockedby:
Blocking: | Related:
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{{{
newtype Whomp = Whomp Int
deriving (Eq)
instance Num Whomp where
Whomp a + Whomp b = Whomp (a+b)
Whomp a * Whomp b = Whomp (a*b)
abs (Whomp a) = Whomp (abs a)
signum (Whomp a) = Whomp (signum a)
fromInteger = Whomp . fromInteger
foo :: Whomp -> String
foo cc = case cc of
Whomp 0 -> "zero"
10 -> "ten"
}}}
produces
{{{
Foo.hs:12:10: Warning:
Pattern match(es) are overlapped
In a case alternative: Whomp 0 -> ...
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/8016>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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