#15351: QuantifiedConstraints ignore FunctionalDependencies -------------------------------------+------------------------------------- Reporter: aaronvargo | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.5 checker) | Keywords: Resolution: | QuantifiedConstraints Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by aaronvargo): Replying to [comment:6 simonpj]:
Would anyone like to fix this?
How difficult would it be? I might like to try, but I've never contributed to GHC before. I could see it being pretty simple since most of the logic should already exist for top-level instances, but I wouldn't know. And I might need some hand-holding...
It's intriguing -- I never expected people to explore the outer limits of quantified constraints so rapidly.
I would guess this is partly because we could already (somewhat painfully) manually represent such constraints with `Dict`s, so we already had some idea of what they might be useful for, and want them to be able to do everything we can do with `Dict`s (though that turns out to be unreasonable). I came across this particular issue while trying to work around #15347, but I'll write more about that on that ticket (at some point. Maybe after I can get my stupid example to work). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15351#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler