An example of bridging, and mutable/immutable class sets.

bridging.swift

public struct AContext: ReferenceConvertible, Equatable, Hashable {
    internal var _handle: SEGMutableContext
  
    public typealias ReferenceType = SEGContext
    public typealias _ObjectiveCType = SEGContext
  
    public static func _getObjectiveCType() -> Any.Type {
        return SEGContext.self
    }
  
    public var debugDescription: String = "dookie"
    public var description: String = "poop"
  
    init(analytics: SEGAnalytics) {
        _handle = SEGMutableContext(analytics: analytics)
    }
    
    init(_ context: SEGContext) {
        _handle = context.mutableCopy()
    }

    fileprivate init(_bridge context: SEGContext) {
        _handle = context.mutableCopy()
    }
    
    @_semantics("convertToObjectiveC")
    public func _bridgeToObjectiveC() -> SEGContext {
        return _handle as SEGContext
    }

    public static func _forceBridgeFromObjectiveC(_ source: SEGContext, result: inout AContext?) {
        result = AContext(_bridge: source)
    }

    public static func _conditionallyBridgeFromObjectiveC(_ source: SEGContext, result: inout AContext?) -> Bool {
        result = AContext(_bridge: source)
        return true
    }

    public static func _unconditionallyBridgeFromObjectiveC(_ source: SEGContext?) -> AContext {
        var result: AContext? = nil
        _forceBridgeFromObjectiveC(source!, result: &result)
        return result!
    }

    public var debug: Bool {
        get {
            return _handle.debug
        }
        set {
            _handle.debug = newValue
        }
    }
}


let mutable = AContext(context)
mutable.debug = true // COMPILER ERROR.  GOOD!

//----------

var mutable = AContext(context)
mutable.debug = true // WORKS!

//----------

var mutable = SEGContext(analytics: analytics) as AContext
mutable.debug = true // WORKS!