Captures of curried function are incorrectly dropped

[odersky]

Compiler version

3.6.0

Minimized example

class C
def test(x: C^) =
  val f = () =>
    def foo() =
      x
      ()
    println(s"hey: $x")
    () => foo()
  val _: () -> () ->{x} Unit = f  // should be error, but compiles
  ()

Output

compiles

Expectation

An error, since the outer lambda also captures x in its println statement.