class T::Props::Private::ApplyEmptyArrayDefault

‘some_empty_array.dup`
faster than falling back to ApplyComplexDefault or even calling
Special case since it’s so common, and a literal ‘[]` is meaningfully

def default 

def default
  []
end

def set_default(instance) 

def set_default(instance)
  instance.instance_variable_set(@accessor_key, [])
end