● This change is about the syntax for type lambdas (type-level functions) in the kind-projector compiler plugin.

  What It Means

  Original Code (with ?)

  implicit def zioSync[R]: Sync[RIO[R, ?]] = new Sync[RIO[R, ?]] {

  Updated Code (with *)

  implicit def zioSync[R]: Sync[RIO[R, *]] = new Sync[RIO[R, *]] {

  Explanation

  The Problem Being Solved

  Sync is a type class that expects a type constructor with one type parameter (like F[_]), but RIO has two type parameters: RIO[R, A].

  To make RIO fit, you need to "partially apply" it - fix the first parameter R and leave the second parameter A as a hole.

  What RIO[R, ?] / RIO[R, *] Means

  Both syntaxes mean: "A type constructor that takes one type parameter and produces RIO[R, <that parameter>]"

  For example:
  - RIO[R, *] applied to String = RIO[R, String]
  - RIO[R, *] applied to Int = RIO[R, Int]

  This is equivalent to writing:
  // Without kind-projector (verbose):
  type RIOPartiallyApplied[A] = RIO[R, A]
  implicit def zioSync[R]: Sync[RIOPartiallyApplied] = ...

  // With kind-projector (concise):
  implicit def zioSync[R]: Sync[RIO[R, *]] = ...

  Why Did It Change?

  kind-projector Version History

  - 0.10.x and earlier: Used ? syntax
  - 0.11.0+: Introduced * syntax (kept ? for compatibility)
  - 0.13.0+: * is preferred to align with Scala 3's native type lambda syntax