Welcome

This manual describes the syntax and semantics of Swift unambiguously and in technical detail.

Caveat: it is incomplet, incorrekt, and under heavy development.

It is intended to provide:

A central home for captured knowledge.
A complete programming model that programmers can use to reason about the meaning of programs, without reference to details of Swift’s implementation.
A platform of shared understanding that the Swift evolution community can use to discuss language changes and their implications.
A means of objectively evaluating the cost of any proposed change in terms complexity of the programming model.
A basis for deciding whether a behavior constitutes a bug in the reference implementation.

Motivation

The Swift community needs a single document to which it can turn to for a detailed technical understanding of how the language is supposed to work. That information has not always been available, and when available has historically been scattered across a great many resources. The Swift Programming Language is a great book, but as a formal reference manual it fails to describe many of the details needed to use the language effectively. As a consequence, a full understanding of language semantics often involves a dive into implementation details that should never be part of a user’s programming model. A proper language reference manual prioritizes precision and completeness over friendly narrative, but also describes the language at a level that can be understood without reading the language’s source code.

Scope

This effort is focused on the Swift’s core language. The documentation of the Swift standard library is generally complete enough that its intent and details of its behavior can be understood without an additional reference manual. Therefore, this reference will only discuss standard library components to the degree needed to describe the core language. So for example, while Swift.UnsafePointer will surely be mentioned, types such as Swift.Set may not be.

Resources

The source for this document is developed in the SwiftRef project.