Scala2 and Scala3 type projections test

typeprojection.scala

trait Logger {
  protected def formatMessage(message: String): String

  def log(message: String): Unit = {
    println(formatMessage(message))  
  }

  // Nested case class inside the trait
  case class LogEntry(timestamp: Long, content: String)
}

object Logger {
  def apply(): Logger = new Logger {
    override protected def formatMessage(message: String): String = 
      s"${System.currentTimeMillis()}: $message"
  }

  // Create a LogEntry instance using the nested case class in the trait
  def createLogEntry(logger: Logger, content: String): logger.LogEntry = 
    logger.LogEntry(System.currentTimeMillis(), content)

  // Process a LogEntry instance
  def processLogEntry(entry: Logger#LogEntry): Unit = 
    println(s"Processing log entry: Timestamp = ${entry.timestamp}, Content = ${entry.content}")
}

// Usage
val logger = Logger()
val entry = Logger.createLogEntry(logger, "This is a log entry.")
Logger.processLogEntry(entry)

Dropped general type projection in Scala 3: https://docs.scala-lang.org/scala3/reference/dropped-features/type-projection.html

See: https://blog.rockthejvm.com/scala-3-type-projections/