I don't know how to do this either. Luckily, we can reject E2 on a first

#6018: Injective type families -------------------------------------+------------------------------------- Reporter: lunaris | Owner: jstolarek Type: feature | Status: new request | Milestone: 7.10.1 Priority: normal | Version: 7.4.1 Component: Compiler | Keywords: TypeFamilies, Resolution: | Injective Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: | Blocked By: None/Unknown | Related Tickets: #4259 Test Case: | Blocking: | Differential Revisions: Phab:D202 | -------------------------------------+------------------------------------- Comment (by jstolarek): pass. Yes, I believe that's what we should do. If we ever have analysis of unreachable equations for type families then we can use it to deal with `E2` but until then we should simply reject it. As for answers to 1-5 I'll read some more and get back if that doesn't help. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/6018#comment:88 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler