#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: 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 simonpj): I think the right thing to do here is to use a different flag for the "allow a representational role annotation on a class", or better yet to make it a per-role-annotation flag. Using `IncoherentInstances` for ''both'' that ''and'' the old meaning is asking for trouble. I think we could make this change without hurting anyone much, because I bet that almost no one uses a representational role annotation on a class! (One other thought. Allowing per-decl things like `{-# OVERLAPS #-}` means you can't look at the top of the file and see what extensions it uses. Really we should have a language extensions `{-# LANGUAGE OverlapsAllowed #-}` or something, which enables the per-decl pragmas. Doing that ''would'' have a bigger impact!) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14292#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler