OI in 7.10.1

[Sergei Meshveliani]

Please, what is wrong here?

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module OI where
class Foo a where foo :: a -> Bool

instance Foo Bool where foo _ = True

data C a = C a

instance {-# OVERLAPPING #-} Foo a => Foo (C a) where foo (C a) = foo a
instance {-# OVERLAPPING #-} Foo (C Bool)       where foo _ = False
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By this I intended to test the overlapping instance control. 
I set the pragma as it is shown in the User guide.
And
    ghc-7.10.1  -c -XFlexibleInstances OI.hs

reports  "Unrecognised pragma".

Please, advise,

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Sergei