5  

Looking at the open-source implementation of UIKit, there seems to be no difference:

看看UIKit的开源实现,似乎没有区别:

extension UIImage : _ImageLiteralConvertible {
  private convenience init!(failableImageLiteral name: String) {
    self.init(named: name)
  }

  public required convenience init(imageLiteralResourceName name: String) {
    self.init(failableImageLiteral: name)
  }
}

public typealias _ImageLiteralType = UIImage

All it does is force-unwrap the result of init(named:).

它只是强制解包init(名为:)的结果。

It seems like it's just an implementation of the _ImageLiteralConvertible protocol found in CompilerProtocols.swift :

看起来它只是CompilerProtocols.swift中的_ImageLiteralConvertible协议的一个实现:

public protocol _ImageLiteralConvertible {
  init(imageLiteralResourceName path: String)
}

AppKit also has a similar implementation:

AppKit也有类似的实现:

extension NSImage : _ImageLiteralConvertible {
  private convenience init!(failableImageLiteral name: String) {
    self.init(named: name)
  }

  public required convenience init(imageLiteralResourceName name: String) {
    self.init(failableImageLiteral: name)
  }
}

public typealias _ImageLiteralType = NSImage

This might have to do with the new image literal functionality added to Xcode 8.

这可能与添加到Xcode 8的新图像文字功能有关。