Without this patch, trying to build latte-dock with clang 9.0 results in:
../app/settings/delegates/persistentmenu.cpp:23:41: error: addition of default argument on redeclaration makes this constructor a default constructor
PersistentMenu::PersistentMenu(QWidget *parent = 0)
^ ~
../app/settings/delegates/persistentmenu.h:31:3: note: previous declaration is here
PersistentMenu(QWidget *parent);
^
1 error generated.