private fields don't work

[iliabylich]

class Test {
  public a: number = 1
  private b: number = 2
}

const t = new Test()
oc(t).a
oc(t).b(0)

gives:

Property 'b' does not exist on type 'TSOCType<Test>'.

8 oc(t).b(0)
          ~