Even though Swift 3 provides great Generics features, it is not complete. According to the Generics Manifesto, there are a number of Generics features the standard library requires to fully realize its vision, including "recursive protocol constraints, and the ability to make a constrained extension conform to a new protocol" (that is, an array of Equatable elements is Equatable). Swift 3.0 should provide those Generics features needed by the standard library, because they affect the standard library's application binary interface (ABI).

An ABI is the interface between two program modules, at the level of machine code. An ABI determines how functions are called and in which binary format information should be passed from one program component to the next.

The Generics Manifesto, which is accessible via https://github.com/apple/swift/blob/master/docs/GenericsManifesto.md, and the Swift ABI Stability Manifesto, which is accessible via https://github.com/apple/swift/blob/master/docs/ABIStabilityManifesto.md, are great reads for the curious.