Named arguments reorder effects

def foo(bar: Int, bat: Int) = 1
def p(x: Int) = { println(x); x }

Scala 2.12:

scala> foo(bat = p(1), bar = p(2)) 
1
2

Dotty:

scala> foo(bat = p(1), bar = p(2)) 
2
1

[nicolasstucki]

Here is a nice test case that includes default parameters.

object Test {
  def p(x: Int) = { println(x); x }
  def foo(x1: Int, x2: Int, , x3: Int, x4: Int = p(4), x5: Int = p(5)) = 1
  def main(args: Array[String]) = {
    foo(p(1), p(2), p(3)) // 1 2 3 4 5
    foo(p(1), x2 = p(2), x3 = p(3)) // 1 2 3 4 5
    foo(p(1), x3 = p(3), x2 = p(3)) // 1 3 2 4 5
    foo(p(1), x3 = p(3), x5 = p(5), x2 = p(2)) // 1 3 5 2 4
    foo(p(1), x3 = p(3), x4 = p(4), x2 = p(2)) // 1 3 4 2 5
  }
}

[nicolasstucki]

I will have a look.