#14292: Coercing between constraints of newtypes -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Roles 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): I started a [https://www.reddit.com/r/haskell/comments/72zdwm/use_cases_for_type_classes_... reddit discussion]. * `type role Coercible representational representational` is an example of a "type class" with representational roles. * [http://www.well-typed.com/blog/2015/07/checked-exceptions/ Well-Typed] has a `representational` example that could be `phantom` (`class Throws e`). * [https://www.reddit.com/r/haskell/comments/2iqrr5/video_simon_peyton_jones_ze... Sjoerd Visscher] wants this as early as 2 years ago. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14292#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler