Fix Monoid instances for ForeignLib & Executable #9555
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@alt-romes: apparently the |
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Hmm, something is still borked. |
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The Semigroup and Monoid instances for ForeignLib were completely broken: for the `foreignLibVersionInfo` and `foreignLibVersionInfo`, we essentially had the following: mempty :: Maybe XYZ mempty = Nothing (<>) :: Maybe XYZ -> Maybe XYZ -> Maybe XYZ _ <> b = b which is obviously not a valid Monoid, as `Just x <> Nothing = Nothing`, violating the identity law. The Semigroup instance for Executable was also deeply suspicious, as it combined the module paths, which makes no sense. Now we instead error if the two module paths are different (and both nonempty).
The
SemigroupandMonoidinstances forForeignLibwere completely broken: for theforeignLibVersionInfoandforeignLibVersionInfo, we essentially had the following:which is obviously not a valid
Monoid, asJust x <> Nothing = Nothing, violating the identity law.The
Semigroupinstance forExecutablewas also deeply suspicious, as it combined the module paths, which makes no sense. Now we instead error if the two module paths are different (and both nonempty).