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klapaucius/gist:3357481

Created August 15, 2012 07:59
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Typeable
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gistfile1.hs
GHCi, version 7.4.1: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> import Control.Exception
Prelude Control.Exception> import Data.Typeable
Prelude Control.Exception Data.Typeable>
newtype Foo = Foo (() -> IO ())
Prelude Control.Exception Data.Typeable> :set -XSafe
Prelude Control.Exception Data.Typeable>
instance Typeable Foo where
typeOf _ = typeOf (undefined :: ErrorCall)
<interactive>:15:10:
Can't create hand written instances of Typeable in Safe Haskell! Can only derive them
Prelude Control.Exception Data.Typeable>
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