RxSwift: error when compiling with RxSwift - '_lock' is inaccessible due to 'private' protection level in DisposeBag

Short description of the issue:

Since few days, I add RxSwift with cocoapods in my iOS project. when i build it, i have this error :

Pods/RxSwift/RxSwift/Disposables/DisposeBag.swift:107:31: '_lock' is inaccessible due to 'private' protection level

Expected outcome:

My project builds

What actually happens:

I have a problem with the declaration in disposebag private var _lock = SpinLock()

/// Convenience function allows an array of disposables to be gathered for disposal.
   public func insert(_ disposables: [Disposable]) {
       _lock.lock(); defer { _lock.unlock() }
       if _isDisposed {
           disposables.forEach { $0.dispose() }
       } else {
           _disposables += disposables
       }
   }

i have this error '_lock' is inaccessible due to 'private' protection level at the line _lock.lock(); defer { _lock.unlock() }

Self contained code example that reproduces the issue:

RxSwift/RxCocoa/RxBlocking/RxTest version/commit

RxSwift 4.3.0 RxCocoa 4.3.0

Platform/Environment

• iOS
• macOS
• tvOS
• watchOS
• playgrounds

How easy is to reproduce? (chances of successful reproduce after running the self contained code)

• easy, 100% repro
• sometimes, 10%-100%
• hard, 2% - 10%
• extremely hard, %0 - 2%

Xcode version:

  Xcode 9.4.1 

⚠️ Fields below are optional for general issues or in case those questions aren’t related to your issue, but filling them out will increase the chances of getting your issue resolved. ⚠️

Installation method:

• CocoaPods
• Carthage
• Git submodules

I have multiple versions of Xcode installed: (so we can know if this is a potential cause of your issue)

• yes (which ones)
• no

Level of RxSwift knowledge: (this is so we can understand your level of knowledge and formulate the response in an appropriate manner)

• just starting
• I have a small code base
• I have a significant code base