Hi Ben, > What you are seeing isn't a warning, it's an error. > 8.4.1 throws errors for Monoids missing Semigroup instances not because > of -Wsemigroup but rather because Semigroup is now a superclass of > Monoid. > > -Wsemigroup will likely be deprecated in a future release now since > we've reached phase 2 of the Semigroup/Monoid proposal.
Thank you for your explanation. It's now clear to me! >> GHC 8.4.1rc does not find Monad data types which define "fail" even >> with -Wcompat. Now I understand that >> -Wnoncanonical-monadfail-instances is necessary. Why doesn't -Wcampat >> include -Wnoncanonical-monadfail-instances? > > My understanding is that the MonadFail proposal is in a bit of a state > of limbo, so its preparatory warning flag hasn't yet been added to > -Wcompat. OK. I hope the proposal Wiki documents will be updated anyway. --Kazu _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
