val behavior in scala REPL and Intellij

Question

as expected reassignment is giving error like below in REPL

scala> val a=1
a: Int = 1

scala> a=2
:12: error: reassignment to val
       a=2
         


        

Answer 1

The REPL is intended for rapid friction-less experimentation. It would be very annoying if you had to restart from scratch just because you accidentally mistyped val a = 32 when you meant val a = 23.

Therefore, the REPL is designed in such a way that it gives the appearance of breaking the rules of Scala, although it actually doesn't. The code that gets actually compiled corresponding to the code you entered looks a little bit like this:

object line$1 {
  val a=1
}

object line$2 {
  import line$1._
  val a=2
}