Scala: fix parsing of optional semicolon in for loops

[greg-at-moderne]

What's changed?

Fix parsing of optional semicolon in for loops. And the variant of it without a semicolon, but a newline in between, e.g.

                  for {
                    _ <- Some(1)
                    field <- Some(2)
                  }

What's your motivation?

They suffer from idempotency issues.