#12422: Add decidable equality class -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Core Libraries | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): Replying to [comment:3 goldfire]:
Yes, this is a higher-rank kind! Yikes! :)
1. Making `:~:` heterogeneous would likely break client code.
2. We should have `:~~:` in the standard library. But I was too exhausted from implementing `TypeInType` to start this debate on the
Figured as much. Is there any way to combine visible kind application (#12045) and unifying different type applications (#11385), let's say if I want to write something like {{{#!hs -- (:~~:) :: forall k1 k2. k1 -> k2 -> Type type (:~:) = (:~~:) @k @k :: k -> k -> Type -- using your syntax (visible kind abstraction?) type (:~:) = \@k -> (:~~:) @k @k }}} libraries mailing list. We should really put it in for 8.2. Should I add it to `Data.Type.Equality` on Phab? ---- Should we rewrite `Const :: Type -> k -> Type` to have the kind ...? {{{#!hs data Const :: Type -> forall k. k -> Type where Const :: { getConst :: a } -> Const a b }}} Is there any way to define an `HTestEquality (Const e)` instance? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12422#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler