struct Foo {
  static Foo opCall() {
    return Foo.init;
  }
}

void main() {
  auto foo = cast(immutable(Foo)) Foo.init;
}

// test.d(8): Error: function test.Foo.opCall () is not callable using argument types (Foo)
// test.d(8): Error: expected 0 arguments, not 1 for non-variadic function type Foo()

---

I don't know how DMD could possibly try to call a function inside the cast() type parameter, but it seems like it does. const() instead of immutable() produces the error as well, just cast(Foo) works.