#11207: GHC cannot infer injectivity on type family operating on GHC.TypeLits' Nat, but can for equivalent type family operating on user-defined Nat kind -------------------------------------+------------------------------------- Reporter: duairc | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 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 duairc): You're right, they are subtley different. But I can't "pattern-match" on (n + 1) on the LHS with GHC's TypeLits, because + is a type family and not a constructor. If there was some other way I could accomplish this then I would be satisfied with that for now. But obviously if we could get generalised injectivity that we be awesome. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11207#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler