#9223: Type equality makes type variable untouchable -------------------------------------+------------------------------------- Reporter: Feuerbach | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 (Type checker) | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by tvynr): I'm glad the example is at least somewhat useful. :) I'm unfamiliar enough with the mechanics involved that I don't know if this is related. Should I open another ticket instead or just leave this stuff here? The thing that seems especially peculiar to me is that, in the example above, GHC 7.6.3 can infer the type just fine. This suggests that the GHC 7.8.3 inference algorithm has been made more conservative in some way. I'm guessing that this difference is related to fixing a bug of some kind but, as you say, this case only seems to have the one type which could be inferred. In the meanwhile, I suppose we'll just use the workaround of an explicit unwrapper function if we need to move to GHC 7.8. Thanks! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9223#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler