Lazy vals annotated with `@threadUnsafe` ignore `@transient` annotation

[kyri-petrou]

Compiler version

3.3.6, 3.7.1

Minimized code

Lazy vals annotated with @threadUnsafe do not honour the @transient annotation:

case class Bar() {
  @transient @threadUnsafe
  lazy val value: Long = System.nanoTime()
}

While examining the compiler output should suffice to identify the issue, here's also a reproducer of this behaviour:

//> using scala 3.7.1

import java.io.*
import scala.annotation.threadUnsafe

// Serialize any object to a byte array
def serialize[T <: Serializable](obj: T): Array[Byte] = {
  val byteArrayOutputStream = new ByteArrayOutputStream()
  val objectOutputStream    = new ObjectOutputStream(byteArrayOutputStream)

  try {
    objectOutputStream.writeObject(obj)
    byteArrayOutputStream.toByteArray
  } finally {
    objectOutputStream.close()
    byteArrayOutputStream.close()
  }
}

// Deserialize from a byte array back to an object
def deserialize[T](bytes: Array[Byte]): T = {
  val byteArrayInputStream = new ByteArrayInputStream(bytes)
  val objectInputStream    = new ObjectInputStream(byteArrayInputStream)

  try {
    objectInputStream.readObject().asInstanceOf[T]
  } finally {
    objectInputStream.close()
    byteArrayInputStream.close()
  }
}

case class Foo() {
  @transient
  lazy val value: Long = System.nanoTime()
}

case class Bar() {
  @transient @threadUnsafe
  lazy val value: Long = System.nanoTime()
}

@main def main() = {
  val foo1 = Foo()
  foo1.value // init lazy val
  val foo2 = deserialize[Foo](serialize(foo1))
  assert(foo1.value != foo2.value, "Foo#value is not transient")

  val bar1 = Bar()
  bar1.value // init lazy val
  val bar2 = deserialize[Bar](serialize(bar1))
  assert(bar1.value != bar2.value, "Bar#value is not transient")
}

Output

Exception in thread "main" java.lang.AssertionError: assertion failed: Bar#value is not transient
	at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
	at Foo$package$.main(Foo.scala:50)
	at main.main(Foo.scala:41)

Expectation

I expect that lazy vals annotated with both @threadUnsafe and @transient honour the annotation, or if that's not possible (for some reason) a compiler warning should be raised for illegal combination of annotations