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It seems leftWiden is not available for EitherT with type Nothing as the error.
A proposal was to add leftWiden directly into EitherT instead of having it be implicit
type arguments [String] do not conform to method leftWiden's type parameter bounds [AA >: A]
val res7 = EitherT(cats.effect.IO(Either.right[Nothing, Int](1))).leftWiden[String]
The text was updated successfully, but these errors were encountered:
Adriani-Furtado
changed the title
EitherT leftWiden no available for Nothing error type
EitherT leftWiden not available for Nothing error type
Apr 26, 2020
I'm 👍 for having that in EitherT, but the problem touches all types with polymorphic errors. If I'm not too mistaken, it should be possible to special-case Nothing and add another implicit extension that only works if the error is of type Nothing.
But that's a very general problem with scalac and implicits not resolving for Nothing.
The question is if Cats should add specialized instances for Nothing.
I couldn't find any precedent for that.
It seems
leftWiden
is not available forEitherT
with typeNothing
as the error.A proposal was to add
leftWiden
directly intoEitherT
instead of having it beimplicit
results in the following message:
The text was updated successfully, but these errors were encountered: