Effects in arguments of functions

[jad-hamza]

This example should go through but doesn't:

object ArgumentsEffects {

  def f(x1: Int, x2: Int, x3: Int): Unit = {
    require(x1 == 1)
    require(x2 == 1)
    require(x3 == 3)
  }

  def test: Unit = {
    var x = 0
    f({x += 1; x}, x, {x+= 2; x })
  }

}

// Before ImperativeCodeElimination
[ Debug  ] def test$0: Unit = {
[ Debug  ]   var (x$220: Int) @var = 0
[ Debug  ]   f$75({
[ Debug  ]     x$220 = (x$220 + 1)
[ Debug  ]     x$220
[ Debug  ]   }, x$220, {
[ Debug  ]     x$220 = (x$220 + 2)
[ Debug  ]     x$220
[ Debug  ]   })
[ Debug  ] }

// After ImperativeCodeElimination
[ Debug  ] def test$0: Unit = {
[ Debug  ]   val (x$221: Int) @var = 0
[ Debug  ]   val (x$223: Int) @var = x$221 + 1
[ Debug  ]   val tmp$15: Unit = ()
[ Debug  ]   val (x$222: Int) @var = x$223 + 2
[ Debug  ]   val tmp$14: Unit = ()
[ Debug  ]   f$75(x$223, x$222, x$222)
[ Debug  ] }

[vkuncak]

Note that this works.

  def test: Unit = {
    var x = 0
    val xx1 = {x += 1; x}
    val xx2 = x
    val xx3 = {x+= 2; x }
    f(xx1, xx2, xx3)
  }

I wonder if we should not just first introduce variables for block arguments and then transform?

[samarion]

Yes, great point. I was making a similar reflection in the review of #1252 because this issue is more general than function arguments.