#15696: Derived Ord instance for enumerations with more than 8 elements seems to be incorrect -------------------------------------+------------------------------------- Reporter: mrkkrp | Owner: osa1 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: #14677, #15155 | Differential Rev(s): Phab:D5196, Wiki Page: | Phab:D5201 -------------------------------------+------------------------------------- Comment (by simonpj):
What's wrong with seeing a literal when floating stuff inwards? Why not just introduce case/let around it?
Because the float-in pass floats bindings inwards ''towards their use sites''. If there is no use of the variable bound by a floating binding, then we should not be floating that binding into that part of the code. Literals are an extreme case.
There should be some code somewhere that's supposed to ensure that this assertion is not triggered, but I can't find it.
It's `FloatIn.sepBindsByDropPoint`.
Why did simplifier not remove this case expression?
That is indeed a mystery. Is the code you are showing the output of the simplifier? Can you give instructions to reproduce (maybe make a `wip/` branch)? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15696#comment:71 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler