#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 acfoltzer): Replying to [comment:19 simonpj]: I would be happy with this proposal, but given the difficulty of (b) I wonder if it's realistic in the short term. A `-Wtype-overly-specific` that only checks for unused constraints would be quite confusing. A pairing of `-Wredundant-constraints` as described in Richard's proposal, and a more narrowly-scoped `-Wunused-constraints` would be more straightforward to implement, but the hair-splitting between "redundant" and "unused" might be a bit much for someone who's not in the weeds already. Replying to [comment:17 mboes]:
Our particular bug (and I think there are many situations like it), fell in the latter category (it was a mistakenly unused constraint).
Could you say a bit more about what this case looks like? I can't recall ever hitting something like it, but it's sounding like I probably have and just haven't noticed.
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.
+1; this would be valuable even if `-Wunused-constraints` gets lifted out of `-Wall`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10635#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler