On Mar 8, 2016, at 7:17 PM, Evan Austin <e.c.austin@gmail.com> wrote:

The wiki page for Phase I of Dependent Haskell describes an approach to constrained type families:
https://ghc.haskell.org/trac/ghc/wiki/DependentHaskell/Phase1#Typefamilyequationscanbeconstrained

Did that land in GHC 8.0 and, if so, is the updated syntax documented somewhere?

No, it didn't make it. The motivating test case seemed contrived and so we punted on this one.

Do you have a use case that really needs this feature? That would help to motivate it for 8.2 or beyond.