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Questions tagged [scala-3]

Scala 3.0 is a general-purpose language that makes use of the functional and object-oriented paradigms. It consolidates language constructs to improve the language’s consistency, safety, ergonomics, and performance.

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What exactly is Dotty?

I am reading about Scala 3 and discovered dotty. I am trying to understand what it is. Somewhere I read "It is new compiler", somewhere I read "It is part of Scala 3", and somewhere I read "Dotty is new Scala 3". Can somebody please explain to me…
nomadSK25
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Add Scala 3.0 SDK to IntelliJ

Currently, the dotty compiler released its first Release Candidate and will be released in the next few months. I updated the IntelliJ scala plugin to EarlyAccess to make it working with Scala 3.0, its problem with syntax highlighting resolved, but…
Nik Kashi
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1 answer

Extracting and accessing fields at compile time in Scala 3

Extracting names and types of elements of a case class at compile time in Scala 3 has been already explained well in this blog: https://blog.philipp-martini.de/blog/magic-mirror-scala3/ However, the same blog uses productElement to get the values…
Koosha
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What does ?=> mean in Scala?

I have seen the ?=> symbol appear in Scala code and in some discussion posts about Scala 3, so I am assuming that it is a Scala 3+ symbol. Nothing appears when searching through documentation or Google, but it looks like the syntactic sugar for the…
Ian
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What is the meaning of "?=>" in Scala 3?

I cannot find explanation of the following syntax rule: FunType ::= FunTypeArgs (‘=>’ | ‘?=>’) Type
user3514920
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1 answer

scala 3 macro how to implement generic trait

I want to implement a proxy of some trait A (e.g. delegates method call to some rpc call), like this def clientProxy[A](using Type[A], Quotes): Expr[A] = { import quotes.reflect._ val defTrees: List[Tree] =…
jilen
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How to generate a class in Dotty with macro?

Is it possible to generate a new class with macro in Dotty, Scala 3 ? Zlaja
zlaja
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9
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How to get Scala annotations that are given to an argument of a method

Consider the following annotation: // ok to have more meta @field @param @compileTimeOnly("Only for code generation") case class Annot(value: String) extends ConstantAnnotation Now three uses: case class A(x: Int, @Annot("z") y: String) object A: …
Koosha
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9
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3 answers

How to create a general method for Scala 3 enums

I want to have a simple enumDescr function for any Scala 3 enum. Example: @description(enumDescr(InvoiceCategory)) enum InvoiceCategory: case `Travel Expenses` case Misc case `Software License Costs` In Scala 2 this is simple…
pme
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1 answer

Parsing scala 3 code from a String into Scala 3 AST at runtime

My goal is to get Scala 3 code as a String and to parse it into Abstract Syntax Tree for Scala 3 at runtime. In the process if the code has compilation errors, I should get that as part of some exception. The larger goal is to end up with Expr[T] if…
arinray
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Use case of kind polymorphism with AnyKind

Given trait Int // proper type trait List[A] // 1st-order-kinded type constructor trait Functor[F[_]] // higher-order-kinded type constructor taking type constructor trait I[H[F[_]]] // higher-order-kinded…
Mario Galic
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In multi-stage compilation, should we use a standard serialisation method to ship objects through stages?

This question is formulated in Scala 3/Dotty but should be generalised to any language NOT in MetaML family. The Scala 3 macro tutorial: https://docs.scala-lang.org/scala3/reference/metaprogramming/macros.html Starts with the The Phase Consistency…
tribbloid
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Scala 3 Explicit Nulls flag makes String operations quite unusable

When using the new Scala 3's flag -Yexplicit-nulls, every Java code which doesn't have explicit non-null annotations is treated as nullable, thus every Java method not returning a primitive type T effectively returns T | Null. Problem: In Scala,…
Ota Hauptmann
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2 answers

How to use akka in Scala 3?

How to use akka in Scala 3 ? I can't find akka dependencies while using scala 3 sbt errors : [error] not found: /Users/admin/.ivy2/localcom.typesafe.akka/akka-actor-typed_3/2.6.15/ivys/ivy.xml [error] not found:…
Ji Shuai
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2 answers

Difference between Scala 2 implicits and Scala 3 given/using

What is the difference between the implicit keyword in Scala 2 and given+using in Scala 3? Is it just that implicit has been split up into two keywords, or are the semantics also different, and if so, how?
user
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