Remove noncanonical definitions #206
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This appeases the -Wnoncanonical-monoid-instances and -Wnoncanonical-monad-instances warnings. These warnings exist because a future GHC release may treat noncanonical definitions as errors. See also: https://gitlab.haskell.org/ghc/ghc/-/wikis/proposal/monad-of-no-return https://gitlab.haskell.org/ghc/ghc/-/wikis/proposal/semigroup-monoid
phadej
reviewed
Feb 23, 2025
| @@ -35,7 +35,6 @@ instance (Zip f, Semigroup a) => Semigroup (Zippy f a) where | |||
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| instance (Repeat f, Monoid a) => Monoid (Zippy f a) where | |||
| mempty = Zippy $ repeat mempty | |||
| mappend (Zippy x) (Zippy y) = Zippy $ zipWith mappend x y | |||
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this change is potentially changing behavior, so no, I won't do these. Until GHC starts to treat them as errors, I won't cleanup these warnings.
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There seems to be some confusion elsewhere about the reasoning here. @phadej's argument seems to be (please correct me if I misunderstood it) that defining |
Yes. |
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This appeases the -Wnoncanonical-monoid-instances and -Wnoncanonical-monad-instances warnings. These warnings exist because a future GHC release may treat noncanonical definitions as errors.
See also:
https://gitlab.haskell.org/ghc/ghc/-/wikis/proposal/monad-of-no-return
https://gitlab.haskell.org/ghc/ghc/-/wikis/proposal/semigroup-monoid