testsuite/tests/parser/should_fail/readFail039.stderr


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readFail039.hs:9:14: error:
    • Can't make a derived instance of ‘C Foo’:
        ‘C’ is not a stock derivable class (Eq, Show, etc.)
        Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
    • In the newtype declaration for ‘Foo’