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I load the following code into GHCi with warnings enabled (-Wall)

{-# LANGUAGE EmptyDataDecls #-}

data Empty

data EitherStrict a b = LeftStrict !a | RightStrict !b

test :: Char
test =
   case undefined :: EitherStrict Empty Char of
--      LeftStrict _ -> undefined
      RightStrict b -> b

I get the warning:

CaseOfEmptyData.hs:9:3:
    Warning: Pattern match(es) are non-exhaustive
             In a case alternative: Patterns not matched: LeftStrict _

I think this warning is wrong, since the LeftStrict case cannot happen. Am I right?

This may be related to #2431 (closed).

This problem is of minor priority for me. I found that in the original problem EmptyDataDecls would not helped me at all, and I found a better solution in this particular case.

Trac metadata

Trac field	Value
Version	6.12.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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