#12680: Permit type equality instances in signatures -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: feature request | Status: new Priority: low | Milestone: Component: Compiler (Type | Version: 8.1 checker) | Resolution: | Keywords: backpack 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): This idea seems reasonable... but your example does not, I'm afraid. If `T` and `S` are datatypes, then how could they be equal? And your `F Int ~ S` seems like it could just be an instance of the type family. On the other hand {{{ data T data S type family F a type family G a instance F T ~ G S }}} seems more realistic. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12680#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler