#14366: Type family equation refuses to unify wildcard type patterns -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.2.1 checker) | Keywords: TypeFamilies, Resolution: | TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): I could go either way on this one. (Where I'm choosing between "that's correct behavior" and "that's a bug".) I interpret `_` in a type family equation to mean the same as a fresh type variable. And I also think that `Cast a b Refl x = x` is suspect. On the other hand, this is a bit silly of GHC not to unify. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14366#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler