#9443: Regression from 7.6.3 to 7.8.3: could not coerce because argument "has role Nominal" -------------------------------------+------------------------------------- Reporter: bernalex | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: wontfix | Keywords: Operating System: | Architecture: x86_64 (amd64) Unknown/Multiple | Difficulty: Unknown Type of failure: GHC | Blocked By: rejects valid program | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Changes (by goldfire): * status: new => closed * resolution: => wontfix Comment: The way to handle the original case is to detect the redundant constraint and eliminate it, before doing any other processing. However, GHC does not do this currently, and the choice would have runtime consequences I think -- it would speed programs up, which now have fewer dictionaries to pass. I'm not inclined to make this change: perhaps the user has good reasons for the redundancy. Short of that, I don't see a way to fix this without contortions. Given the comments above, I'm closing as wontfix. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9443#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler