This implements GHC proposal 35 (https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0035-forall-arrow.rst) by adding the ability to write kinds with visible dependent quantification (VDQ). Most of the work for supporting VDQ was actually done _before_ this...
Why is nobody talking about visible dependent (kind) quantification in 8.10?: https://gitlab.haskell.org/ghc/ghc/commit/c26d299dc422f43b8c37da4b26da2067eedcbae8
With StandaloneKindSignatures, this is going to make dependent kinds much nicer
E.g.
Guess people are not using it much :)