#10635: -fwarn-redundant-constraints should not be part of -Wall -------------------------------------+------------------------------------- Reporter: Lemming | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.11 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: #9939, #9973, | Differential Rev(s): #10100, #10183, #11370 | Wiki Page: | -------------------------------------+------------------------------------- Comment (by mboes): Replying to [comment:15 acfoltzer]:
I also wonder if it might make sense to distinguish between certain types of redundancy: for example, in our code a redundancy arising from a superclass relationship (e.g., `(Functor f, Applicative f)`) is almost always something we want to fix, but unused classes are almost always an API design choice rather than a bug we wish to avoid.
Our particular bug (and I think there are many situations like it), fell in the latter category (it was a mistakenly unused constraint). If only the former category is included in -Wall, then -Wall will be useless to us and others to catch similar bugs in the future. We'll have to remember to `-Wall -Wsome-other-warning-flag` in all projects. I think what would be nice though is if there existed a pragma to mark a constraint as explicitly redundant, for those who want that. In general, it's nicer to be able to specify things at fine granularity - disabling redundant constraint checking at the module level is too coarse a granularity. Probably a matter for a separate ticket. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10635#comment:17 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler