A new beta means a new compiler. Check out the official release notes for more information.

Swift 2.2

• Lots of compiler crashes have been fixed.
• You can use #if swift(>=x.y) checks to gate the use of compiler features. This should finally make it possible to have a single branch support multiple versions of Swift simultaneously (though only going forward)
• The associatedtype keyword replaces typealias for associated types. It was always strange to me that the keyword was overloaded for entirely different purposes so this is a very welcome change. The use of typealias for associated types will be removed in Swift 3.
  • This is supposed to apply to adopters of protocols where they want or need to specify the associated type, but currently does not.
• You can get a reference to a function by providing the name including argument labels.The syntax is someFunc(_:label1:label2:). The underscore is a consequence of the rule that un-labelled parameters are specified with an underscore and the first parameter usually doesn't carry a label. This can be useful when there are overloads and it is easier to specify which overload via the labels rather than having to provide a type signature.It is absolutely required when the overloads have the same type signature and only differ by label.
• The C-style macro-ish __FILE__, __LINE__, __COLUMN__, and __FUNCTION__ symbols have been replaced by #file, #line, #column, and #function. This is definitely more consistent with general Swift style and the general principle when you see # some compile-time magic is happening.

Objective-C Selectors

• You can get a selector for an Objective-C method with #selector. No more stringly-typed selectors!
• The old behavior has been deprecated and the compiler will offer fix-its for it.
• There is one caveat: Currently it isn't possible to use this support for property getters so you can construct those using strings.
• If you are thinking the compiler will be really annoying and offer fix-its for cases you can't fix I have good news: Swift parses selector strings and validates that there is in fact an Objective-C selector visible matching the string.