Handle expression syntax

[chtenb]

pub effect yield<a>
  ctl yield(elem : a) : ()
  
pub fun fin/take(it : () -> <yield<a>|e> (), n : int) : <yield<a>|e> ()
  var count := 0
  override handle it
    ctl yield(elem)
      if count < n then
        yield(elem) // Forward the yield to our new yield function
        count := count + 1
        resume(())
      else
        ()

According to the compiler, this syntax is invalid

repro.kk(7, 3): parse error: invalid syntax
  unexpected "override"
  expecting ";", "inline", "noinline", "tail", "fip", "fbip", "fun", "val", "var", "with", (basic) expression, "return" or "}"

But if I'm not mistaken, the syntax spec in the book says this should work: https://koka-lang.github.io/koka/doc/book.html#sec-handler-expressions
Which of the two is right?

[TimWhiting]

According to the grammer you need parenthesis around it. But even that does not work so that is an issue.

You can use the following desugaring though:

pub fun fin/take(it : () -> <yield<a>|e> (), n : int) : <yield<a>|e> ()
  var count := 0
  handle({mask behind<yield>{it()}})
    ctl yield(elem)
      if count < n then
        yield(elem) // Forward the yield to our new yield function
        count := count + 1
        resume(())
      else
        ()