Simple Macro example, allows you to have a string which shows when last compiled. Remember that your main has to be in a different project to the macro (for the moment)

TimestampMacro.scala

package com.felstar.macros.timestamp

import scala.reflect.macros.blackbox.Context
import scala.language.experimental.macros

object TimestampMacro {
 def timestampString: String = macro timestampMacro

  def timestampMacro(c: Context): c.Tree = {
    import c.universe._

    val now = new java.util.Date().toString

    q"$now"
 }
}

TimestampMain.scala

object TimestampMain extends App {
 
  val timestamp=com.felstar.macros.timestamp.TimestampMacro.timestampString
  
  println(s"This was compiled at ${timestamp}")
}