Warnings from -fwarn-incomplete-record-updates even with all constructors matched

I don't think that the following should be considered an incomplete record update, since I match on the other constructor before the record update:

data Foo = None | Bar { baz :: Int }

quux :: Foo -> Foo
quux None = None
quux x = x { baz = 2 }

main :: IO ()
main = return ()

But it still throws a warning:

$ ghc -fwarn-incomplete-record-updates test.hs
[1 of 1] Compiling Main             ( test.hs, test.o )

test.hs:6:10:
    Warning: Pattern match(es) are non-exhaustive
             In a record-update construct: Patterns not matched: None
Linking test ...

Trac metadata

Trac field	Value
Version	7.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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