If I try to call the protected method of a superclass from inside the body of a delegate, the compiler won't allow it.

void layoutTransaction(Control c, void delegate() action) {
  // do stuff
  action();
  // do more stuff
}

class Control {
  protected void onTextChanged() {}
}

class Label : Control {
  protected override void onTextChanged() {
    layoutTransaction(this, {
      super.onTextChanged(); // <--- Error here
      changeSize();
    });
  }
  private void changeSize() {}
}

Output: class Control member onTextChanged is not accessible.

How is it possible that "onTextChanged" isn't accessible but the private method "changeSize" *is*?

On Friday, 23 September 2016 at 07:54:15 UTC, John C wrote:
> How is it possible that "onTextChanged" isn't accessible but the private method "changeSize" *is*?

Smells like an oversight. I guess the compiler doesn't see the delegate as a member of a Control subclass, so it can't access protected members. Private works because private in D means module private.

Please file an issue. As a workaround you can try to take the address of the method in the closure (untested):

void delegate() foo()
{
  auto func = &super.someProtectedFunc;

  return () => func(); // I think this will work
}

On Friday, 23 September 2016 at 07:54:15 UTC, John C wrote:
> If I try to call the protected method of a superclass from inside the body of a delegate, the compiler won't allow it.
>
> void layoutTransaction(Control c, void delegate() action) {
>   // do stuff
>   action();
>   // do more stuff
> }
>
> class Control {
>   protected void onTextChanged() {}
> }
>
> class Label : Control {
>   protected override void onTextChanged() {
>     layoutTransaction(this, {
>       super.onTextChanged(); // <--- Error here
>       changeSize();
>     });
>   }
>   private void changeSize() {}
> }
>
> Output: class Control member onTextChanged is not accessible.
>
> How is it possible that "onTextChanged" isn't accessible but the private method "changeSize" *is*?

Please file a bug report issues.dlang.org, shouldn't be difficult to fix.

On Friday, 23 September 2016 at 18:20:24 UTC, Martin Nowak wrote:
> Please file a bug report issues.dlang.org, shouldn't be difficult to fix.

Done: https://issues.dlang.org/show_bug.cgi?id=16531

On Friday, 23 September 2016 at 15:29:43 UTC, Rene Zwanenburg wrote:
> On Friday, 23 September 2016 at 07:54:15 UTC, John C wrote:
>> How is it possible that "onTextChanged" isn't accessible but the private method "changeSize" *is*?
>
> Smells like an oversight. I guess the compiler doesn't see the delegate as a member of a Control subclass, so it can't access protected members. Private works because private in D means module private.
>
> Please file an issue. As a workaround you can try to take the address of the method in the closure (untested):
>
> void delegate() foo()
> {
>   auto func = &super.someProtectedFunc;
>
>   return () => func(); // I think this will work
> }

Quoting the document: "protected only applies inside classes (and templates as they can be mixed in) and means that a symbol can only be seen by members of the same module, or by a derived class."

So protected also means module visibility.