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{-# LANGUAGE RankNTypes #-}
module ShouldCompile where
type Generic i o = forall x. i x -> o x
type Id x = x
foo :: Generic Id Id
foo = error "urk"
-- The point here is that we instantiate "i" and "o"
-- with a partially applied type synonym. This is
-- OK in GHC because we check type validity only *after*
-- expanding type synonyms.
--
-- However, a bug in GHC 5.03-Feb02 made this break a
-- type invariant (see Type.mkAppTy)
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