[Haskell-cafe] Non-exhaustive pattern match warning (incorrect?)

[Antoine Latter]

On Mon, Dec 26, 2011 at 1:21 PM, Michael Orlitzky <michael at orlitzky.com> wrote:
> I'm cleaning up some old projects, and hit this:
>
>  src/Octet.hs:47:27:
>    Warning: Pattern match(es) are non-exhaustive
>    In a record-update construct: Patterns not matched: Octet.None
>
> But in the source, I've checked for that case:
>
>  class Maskable a where
>    apply_mask :: a -> Maskbits -> Bit -> a
>
>  instance Maskable Octet where
>    apply_mask _ Maskbits.None _ = Octet.None
>    apply_mask Octet.None _ _    = Octet.None
>    apply_mask oct mask bit
>        | mask == Eight = oct
>        | mask == Seven = oct { b8 = bit } -- Line 47
>        ...
>        | otherwise = Octet.None
>
>
> Am I overlooking something, or did I already match Octet.None?
>

What is your definition of the 'Octet' type?

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