gistfile1.txt

             
                var selectionRule: (TrashEditSelectionRule & TrashEditSelectionRuleProtocol)? = nil

                if let selectionRuleString = editFormula?.editSelectionRuleClass
                {
                    if let selectionRuleClass = NSClassFromString(selectionRuleString) {
                        // Commenting out this line allows compilation to succeed:
                        selectionRule = selectionRuleClass.init() as? (TrashEditSelectionRule & TrashEditSelectionRuleProtocol)
                    }
                }
                else {
                    selectionRule = TrashEditSelectionRuleLeastSimilar()
                }