Scala: “In-place” the trait Inheriting without “new” keyword

Question

I can't understand why a syntax error occurs in this code:

"T.scala" file :

trait T

"A.scala" file :

class A

object A {
  def apply() = new A()
}

"other.scala" file :

val a = new A() with T  // ok
val b = A() with T  // syntax error ';' or newline expected

Can I create a new class instance with inheriting without using the new keyword?

I've not found anything about it.

Answer 1

A() translates to A.apply() which is a method that returns a new object and is not the same as new A() .

You are essentially trying to do this (which will not work):

val b = A.apply()
val c = b with T

You can't use with on an object that has already been created.