Compiling this code:

{-# LANGUAGE Strict #-}

data Lazy a = Lazy ~a

main :: IO ()
main = case Lazy undefined of
            Lazy _ -> putStrLn "Lazy"

fails with the following error:

$ .\inplace\bin\ghc-stage2.exe ../Lazy.hs
[1 of 1] Compiling Main             ( ..\Lazy.hs, ..\Lazy.o )

..\Lazy.hs:3:15: error:
    * Lazy annotation (~) without StrictData
        on the first argument of `Lazy'
    * In the definition of data constructor `Lazy'
      In the data type declaration for `Lazy'

I was under the impression that -XStrict implied -XStrictData. Is this not the case?