I'm not sure. Once you have GADTs, ExistentialQuantification is just syntax. So from one angle, maybe it doesn't matter too much. On the other hand, that syntax, whole traditional, is not the clearest in the world. One could easily imagine a Haskell implementation that chooses only to support GADT syntax for existentials. So maybe it is a bug.

On Aug 26, 2018 9:43 PM, "Cosmia Fu" <cosmiafu@gmail.com> wrote:

Hey everyone,

I found that it seems that GADTs implies ExistentialQuantification, but not mentioned in the manual. Is it a bug?
https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html#extension-GADTs

GHCi, version 8.4.3: http://www.haskell.org/ghc/ :? for help
Prelude> :set -XGADTs -XExplicitForAll
Prelude> data Q = forall a. Q a
Prelude>

----

Cosmia Fu
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