#15696: Derived Ord instance for enumerations with more than 8 elements seems to be incorrect -------------------------------------+------------------------------------- Reporter: mrkkrp | Owner: (none) Type: bug | Status: patch Priority: highest | Milestone: 8.6.2 Component: Compiler | Version: 8.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5196 Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): Aha! Actually, I believe even one fall-back should be able to use tag bits, as long as they're greater than 1. So: === When the type is recognized as having a small number of constructors Check the tag bits. If they '''are 0''', enter the closure. Otherwise, subtract 1 to get the tag. === When the type is unknown Check the tag bits. If they '''are less than or equal to 1''', enter the closure. Otherwise, subtract 1 to get the tag. === When the type has too many constructors Enter the closure. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15696#comment:27 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler