#14363: :type hangs on coerce -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | 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 goldfire): Yes, `anyRewritableTyVar` needs to become role-aware. It should pass a role to the predicate function, I think. But I'm not sure why the "occurs check" failure in the original post is correct. IIUC, we're trying to check `coerce :: (a -> b) -> (f a -> f b)`. In other words, we want to prove `Coercible (a -> b) (f a -> f b)`, which decomposes to `Coercible a (f a)` and `Coercible b (f b)`. These aren't insoluble, and I don't think we should report an occurs-check problem. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14363#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler