Adding to the list of missing documentation:
^ This quote is from a recent thread on protocol self-conformance.
The differences between dynamic and static things (type, dispatch, member lookup, etc) are very important for users to understand (I myself don't understand them well), in order to have a good grasp on the language. However, they're largely missing from the Swift Programming Language book. A lot of this kind of things are documented in the git repository, but most Swift users don't come to the forums or dig through the repository for answers. Some might not even know that a repository exists. The language book is the only official resource for many users, and it would be good to have all the important information included directly in it.