RestoreTo[F[_], G[_]] extends Lift[G[_], F[_]].
#122
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oskin1
requested review from
danslapman,
eld0727,
Odomontois and
Z1kkurat
as code owners
| private[this] implicit val containsInstanceAny: Contains[Nothing, Any] = | ||
| new Contains[Nothing, Any] { | ||
| def set(s: Nothing, b: Any): Nothing = s | ||
| def extract(s: Nothing): Any = s.asInstanceOf[Any] |
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asInstanceOf is redundant
Also, may be this instance should be somewhere in optics module?
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Maybe, but I haven't found more suitable place for such dummy instance.
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I think such instance can be abstracted to smth like:
def subtype[A, B >: A]: Contains[A, B] = PContains[A, B](identity)((x, _) => x)and moved to tofu.optics.functions.
@Odomontois, what do you think?
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I agree with moving, but I like the current non-allocating version more.
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Also, I believe such an instance would break Lens laws in general.
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Yep, sorry, my mistake.
Counterexample: for Contains[Boolean, Boolean] such instance, we have: extract(set(true, false)) = true
| @@ -78,10 +79,12 @@ object ZioTofuInstance { | |||
| } | |||
| } | |||
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| class ZioTofuErrorsToInstance[R, E, E1] extends ErrorsTo[ZIO[R, E, *], ZIO[R, E1, *], E] { | |||
| class ZioTofuErrorsToInstance[R, E, E1](implicit lens: Contains[E1, E]) | |||
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It looks we need only Extract instance here
| def extract(s: Nothing): Any = s | ||
| } | ||
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| private[this] def zioErrorsToInstanceAny: ZioTofuErrorsToInstance[Any, Any, Nothing] = new ZioTofuErrorsToInstance[Any, Any, Nothing] | ||
| final def zioTofuErrorsToInstance[R, E, E1]: ZioTofuErrorsToInstance[R, E, E1] = |
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This instance is not sound anymore.
You can not transform ZIO[R, E1, A] to ZIO[R, E, A] without any prior knowledge about how to map E1 to E
I'm afraid trying to cast arbitrary E1 to Nothing would bring ClassCastException
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I suppose best we can do here is a change E1 to Nothing explicitly for that instance.
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@Odomontois, you mean final def zioTofuErrorsToInstance[R, E]: ZioTofuErrorsToInstance[R, E, Nothing]?
| @@ -78,10 +79,12 @@ object ZioTofuInstance { | |||
| } | |||
| } | |||
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| class ZioTofuErrorsToInstance[R, E, E1] extends ErrorsTo[ZIO[R, E, *], ZIO[R, E1, *], E] { | |||
| class ZioTofuErrorsToInstance[R, E, E1](implicit lens: Extract[E1, E]) | |||
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So now the only use of the lens parameter is to Extract something from Nothing
This is perfectly legit and could not touch performance (since mapError is never applied).
But it looks like we need at least one additional instance , e.g.
final def zioTofuExtractErrorsInstance[R, E, E1: * Extract E1]: ZioTofuErrorsToInstance[R, E, E1] =
new ZioTofuErrorsToInstanceTo justify this encoding.
| @@ -56,4 +56,6 @@ object functions { | |||
| def some[A]: Subset[Option[A], A] = Subset[Option[A]](identity)(Some(_)) | |||
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| def none[A]: Subset[Option[A], Unit] = Subset[Option[A]](_ => Some(()))(_ => None) | |||
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| def extractAnyFromNothing: Extract[Nothing, Any] = (s: Nothing) => s | |||
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Well, Extract[A, B] unlike Lens[A, B] is perfectly legal for any A <: B, so it would be better to see more general case here.
Close #117