Notes from the March, 2018 meeting:

CWG affirmed the earlier direction and felt that there should be an implicit object expression assumed for these cases.

Notes from the December, 2016 teleconference:

The consensus favored accepting f and g while rejecting h.

The rules in 11.8.5 [class.protected] assume an object expression, perhaps implicit, that can be used to determine whether access to protected members is permitted or not. It is not clear how that applies to aggregates and constructors. For example:

  struct A {
  protected:
    A();
  };
  struct B : A {
    friend B f();
    friend B g();
    friend B h();
  };
  B f() { return {}; }     // ok? 
  B g() { return {{}}; }   // ok? 
  B h() { return {A{}}; }  // ok?