Adjust implicit priorities in OneAnd.#538
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scala> implicitly[Functor[NonEmptyList]] <console>:27: error: ambiguous implicit values: both method oneAndFunctor in trait OneAndInstances ... and method oneAndMonad in trait OneAndInstances ... match expected type cats.Functor[cats.data.NonEmptyList] There were two bugs: one is that the Monad implicit conflicts with the Functor implicit. The other is that this construction doesn't work: object OneAnd extends OneAndInstances with OneAndLowPriority If it DID work, this ordering would give priority to the implicits found in OneAndLowPriority, so it's reversed - but more to the point, implicit priority isn't based on linearization. One of the traits has to be a subtrait of the other to have higher priority, and as written they had no relationship.
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👍 once Travis is green |
Current coverage is
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👍 Great catch, thanks Paul! |
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Adjust implicit priorities in OneAnd.
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There were two bugs: one is that the Monad implicit
conflicts with the Functor implicit. The other is that
this construction doesn't work:
object OneAnd extends OneAndInstances with OneAndLowPriorityIf it DID work, this ordering would give priority to the
implicits found in OneAndLowPriority, so it's reversed - but
more to the point, implicit priority isn't based on linearization.
One of the traits has to be a subtrait of the other to have
higher priority, and as written they had no relationship.