Macro ferro_impl_classes 

macro_rules! ferro_impl_classes {
    ($name:ty : $($trait_:path),+ $(,)?) => { ... };
}

Implements class Impl traits with no overrides.

ferro_impl_classes!(Border: FerroObjectImpl, StyledElementImpl, VisualImpl);

Unlike impl VisualImpl for Border {}, which means the same, this form states that nothing is overridden, and the table of the class is built from that: every slot of the members of these traits is the slot of the base class, so a call reaches the implementation without passing through a forwarding function of this class.