https://github.com/scala/scala3/pull/21362

B.java

package x;

class A {
  public int a() { return 2; }
}

public class B extends A{}

build.sbt

scalaVersion := "3.5.1-RC2"

run / fork := true

log.txt

[info] running (fork) y.Main 
[error] Exception in thread "main" java.lang.IllegalAccessError: failed to access class x.A from class y.C (x.A and y.C are in unnamed module of loader 'app')
[error] 	at y.C.c(Main.scala:4)
[error] 	at y.Main$.main(Main.scala:9)
[error] 	at y.Main.main(Main.scala)
[error] Nonzero exit code returned from runner: 1
[error] (Compile / run) Nonzero exit code returned from runner: 1

Main.scala

package y;

class C extends x.B {
  def c: Int = super.a
}

object Main {
  def main(args: Array[String]): Unit = {
    println((new C).c)
  }
}