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The following code

{-# OPTIONS_GHC -Wall #-}

import Data.Word

f :: Word8 -> Bool
f 0 = True
f 1 = False
f 2 = True

Produces the warning

7:1:
    Warning: Pattern match(es) are non-exhaustive
             In an equation for `f':
                 Patterns not matched: #x with #x `notElem` [0#, 1#, 2#]

While accurate, this is not exactly user friendly.

Found in GHC 7.4.1 RC 1

Trac metadata

Trac field	Value
Version	7.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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