Currently learning about Scala 3 implicits but I'm having a hard time grasping what the ​as and with keywords do in a definition like this: given listOrdering[A](using ord: Ordering[A]) as Ordering...

Suppose that I have some typeclass trait FooBar[X] and an instance of FooBar[Int]: given intIsFooBar: FooBar[Int] = new FooBar {} Now, suppose that I have an interface Intf that has some member t...

I'm trying to migrate a library from Scala 2.13 to Scala 3, but the existing code does not compile. Here is a snippet trait Identity trait Authenticator trait Env { type I <: Identity type A ...

If I have an arbitrary type union in Scala 3, is it possible to write a method that "removes" one type from the union? Similar to shapeless.ops.coproduct.Remove, but for native Scala 3. F...

This is both a question and a poll. Considering the following case: trait Mat[+T] implicitly[Mat[Product] =:= Mat[_ <: Product]] /* Compiler error: : Cannot prove that com.tribbloids.spike.d...

I am coding using scala3, leveraging programmatic structural types. The structural types happen to mimic existing case classes: their definition is pure boiler plate, hence the temptation to craft ...

Scala 3.3.0-RC2 has added MacroAnnotation but it has a ton of caveats. The main on is that "new definitions will not be visible from outside the macro expansion". There are a lot of examp...

Here is a short example in Scala 3: type Ext[S <: Seq[_]] = S match { case Seq[t] => t } trait XX[A, B <: Seq[A]] trait XX1[B <: Seq[_]] extends XX[Ext[B], B] So far it appears t...

how to generate a private parameterless constructor on a class (at compile time) when it annotated with @entity annotation - in scala 3 macros class entity extends scala.annotation.StaticAnnotation...

The following is a quote from Macros: the Plan for Scala 3 from more than 3 years ago: For instance, one will be able to define a macro annotation @json that adds a JSON serializer to a type. Any...

How can I impletement type-level operations (addition in this case) in Scala 3 ? Here is what I would like to do (this does not compile) : case class foo[S <: Int & Singleton](value: Double)...

What means this exception and how can I fix it? scalac: Token not found: /Users/mpa/Library/Caches/JetBrains/IntelliJIdea2021.3/compile-server/tokens/54149 I have a Scala 3 project in IntelliJ 202...

Scala3 has support for "kind polymorphism". Docs also mention AnyKind type: AnyKind plays a special role in Scala's subtype system: It is a supertype of all other types no matter what th...

Learning Scala 3. how can i make this code type-match and compile? trait Key { type Value } object Name extends Key { type Value = String } object Age extends Key { type Value = Int } type D...

I'm trying to take an arbitrary tuple of Futures and return a tuple of the completed future's values, while providing a time limit for the completion of the futures. I'm trying to use Tuple's provi...

Here is a simple example: object MatchErasedType { trait Supe { self: Singleton => type T1 lazy val default: T1 def process(v: Any): T1 = { v match { case vv: T1 => vv case _ =&gt...

Trying to grasp Scala 3 type system. Question: Is it possible to write a single universal def curry(f: ???) = ... function that accepts f of any arity and returns a curried fn? No compiler plugins...

I'm trying to zip tuples together and use match types to get the exact type of the resulting zip. I have a match type and the function: type Z[A <: Tuple, B <: Tuple] <: Tuple = (A, B) ma...

(This question is under a permanent bounty of 1000 points, once proven/refuted, it will be retrospectively set up and awarded) (Possible duplicate: https://math.stackexchange.com/questions/4232108/...

This code does not compile in Scala 3 since type projection on an abstract type is now invalid: trait Entity: type Key type Dictionary[T <: Entity] = Map[T#Key, T] The compiler complains tha...

In this article, it is explained that each generic type argument in Scala 3 code is perceived as a dependent type to be conform with the DOT logic: https://dotty.epfl.ch/docs/internals/higher-kinde...

This is a followup on Shapeless and annotations. The original question was asked in the context of Scala 2 and Shapeless2. Some features from Shapeless2 were migrated to Shapeless3, such as annotat...

In Scala 3 I can define a functor for state using type lambda: given stateFunctor[S]: Functor[[A] =>> State[S, A]] with override def map[A, B](a: State[S, A])(fx: A => B): State[S, B] = ...

I'm trying to run an example from the Spark book Spark: The Definitive Guide build.sbt ThisBuild / scalaVersion := "3.2.1" libraryDependencies ++= Seq( ("org.apache.spark" %% ...

I'm pretty new to Scala programming. I pulled a code from GIT into IntelliJ. However, I'm getting the below error while compiling. I have installed latest Scala version (3.2.0) on to my mac (JDK18 ...