T12845.hs:18:70: warning: [-Wpartial-type-signatures (in -Wdefault)]
    • Found type wildcard ‘_’ standing for ‘()’
    • In the type signature:
        broken :: forall r r' rngs.
                  ('(r, r') ~ Head rngs, Bar r r' ~ 'True, _) =>
                  Foo r -> Proxy rngs -> ()