I'm looking at a completion issue in the IDE that is due to a Tree having a transparent position, when an opaque one is expected.

I'll use the following code for describing the issue:

object A {
  def apply(a: Int) = a
  A(
}

Notice the missing closing parens, so there is a syntax error. Nonetheless, if you explicitly type A.apply(, completion works as expected (hence,
I expect this should work similarly when the synthetic apply is injected by scalac).

I had a look at the tree, and my belief is that the positions assigned when expanding A(null) (this is the Tree after parser) into A.apply(null)
(this is the tree I see in typer, while debugging) are incorrect, because the qualifier A in the latter Tree ( A.apply(null)) has a transparent position,
instead of an opaque one. The fact that the qualifier has a transparent position messes up completion, as we need to retrieve the qualifier to look at its members.

Jason correctly suggested to look into insertApply in Typers, and specifically this expression:

       typedPos(tree.pos, mode, pt) {
          Select(qual setPos tree.pos.makeTransparent, nme.apply)
       }

Indeed, changing the above into

       typedPos(tree.pos.makeTransparent, mode, pt) {
          Select(qual setPos tree.pos, nme.apply)
       }

fixes the issue. Will issue a PR soon.