Re: [Haskell-cafe] Why were datatype contexts removed instead of "fixing them"?

Kim-Ee Yeoh writes:

data Foo a where   Foo :: Eq a => a -> Foo a

is equivalent to

data Foo a = Eq a => Foo a

but is different from

data Eq a => Foo a = Foo a

... and nothing in GADTs does what one would naively expect the last declaration to do.