Fix #9295: Avoid recursive Dynamics conversion

[nicolasstucki]

Avoid trying to apply Dynamic transformation on apply with a qualifier that already has
a been handled by the Dynamic transformation.

[liufengyun]

The following code compiles before, but fails to compile after the changes:

import scala.language.dynamics

class Foo extends Dynamic {
  def applyDynamic(name: String): Bar = ???
}

class Bar extends Dynamic {
  def applyDynamic(name: String)(x: Int): Qux = ???
}

class Qux extends Dynamic {
  def applyDynamic(name: String)(x: Int) = ???
}


var foo = new Foo
def baz = foo.blah(42).blah(45)

[nicolasstucki]

That is intended, as in Scala 2.
https://scastie.scala-lang.org/gsxJ9jifRQyc5jLTbrmYSQ

[liufengyun]

The only worry I have is about using positions for semantics (though we have precedent for that when dealing with contextual functions), as positions are very weak invariants.

If there are no better alternatives, maybe we add the example as a neg test?

[nicolasstucki]

Indeed. I will try to find another way to identify the application

[nicolasstucki]

Now I handle properly contextual functions, but we still need to check the positions.

[liufengyun]

LGTM