Preface
"The code is more what you'd call guidelines than actual rules." – Hector Barbossa
In the crowded landscape of modern programming languages, Rust is different. Rust offers the speed of a compiled language, the efficiency of a non-garbage-collected language, and the type safety of a functional language—as well as a unique solution to memory safety problems. As a result, Rust regularly polls as the most loved programming language.
The strength and consistency of Rust's type system means that if a Rust program compiles, there is already a decent chance that it will work—a phenomenon previously observed only with more academic, less accessible languages such as Haskell. If a Rust program compiles, it will also work safely.
This safety—both type safety and memory safety—does come with a cost, though. Despite the quality of the basic documentation, Rust has a reputation for having a steep on-ramp, where newcomers have to go through the initiation rituals of fighting the borrow checker, redesigning their data structures, and being befuddled by lifetimes. A Rust program that compiles may have a good chance of working the first time, but the struggle to get it to compile is real—even with the Rust compiler's remarkably helpful error diagnostics.
Who This Book Is For
This book tries to help with these areas where programmers struggle, even if they already have experience with an existing compiled language like C++. As such—and in common with other Effective <Language> books—this book is intended to be the second book that a newcomer to Rust might need, after they have already encountered the basics elsewhere—for example, in The Rust Programming Language (Steve Klabnik and Carol Nichols, No Starch Press) or Programming Rust (Jim Blandy et al., O'Reilly).
However, Rust's safety leads to a slightly different slant to the Items here, particularly when compared to Scott Meyers's original Effective C++ series. The C++ language was (and is) full of footguns, so Effective C++ focused on a collection of advice for avoiding those footguns, based on real-world experience creating software in C++. Significantly, it contained guidelines not rules, because guidelines have exceptions—providing the detailed rationale for a guideline allows readers to decide for themselves whether their particular scenario warranted breaking the rule.
The general style of giving advice together with the reasons for that advice is preserved here. However, since Rust is remarkably free of footguns, the Items here concentrate more on the concepts that Rust introduces. Many Items have titles like "Understand…" and "Familiarize yourself with…", and help on the journey toward writing fluent, idiomatic Rust.
Rust's safety also leads to a complete absence of Items titled "Never…". If you really should never do something, the compiler will generally prevent you from doing it.
Rust Version
The text is written for the 2018 edition of Rust, using the stable toolchain. Rust's back-compatibility promises mean that any later edition of Rust, including the 2021 edition, will still support code written for the 2018 edition, even if that later edition introduces breaking changes. Rust is now also stable enough that the differences between the 2018 and 2021 editions are minor; none of the code in the book needs altering to be 2021-edition compliant (but Item 19 includes one exception in which a later version of Rust allows new behavior that wasn't previously possible).
The Items here do not cover any aspects of Rust's async functionality, as
this involves more advanced concepts and less stable toolchain support—there's already enough ground to cover
with synchronous Rust. Perhaps an Effective Async Rust will emerge in the future…
The specific rustc version used for code fragments and error messages is 1.70. The code fragments are
unlikely to need changes for later versions, but the error messages may vary with your particular compiler version.
The error messages included in the text have also been manually edited to fit within the width constraints of the book
but are otherwise as produced by the compiler.
The text has a number of references to and comparisons with other statically typed languages, such as Java, Go, and C++, to help readers with experience in those languages orient themselves. (C++ is probably the closest equivalent language, particularly when C++11's move semantics come into play.)
Navigating This Book
The Items that make up the book are divided into six chapters:
- Chapter 1 — Types: Suggestions that revolve around Rust's core type system
- Chapter 2 — Traits: Suggestions for working with Rust's traits
- Chapter 3 — Concepts: Core ideas that form the design of Rust
- Chapter 4 — Dependencies: Advice for working with Rust's package ecosystem
- Chapter 5 — Tooling: Suggestions for improving your codebase by going beyond just the Rust compiler
- Chapter 6 — Beyond Standard Rust: Suggestions for when you have to work beyond Rust's standard, safe environment
Although the "Concepts" chapter is arguably more fundamental than the "Types" and "Traits" chapters, it is deliberately placed later in the book so that readers who are reading from beginning to end can build up some confidence first.
Conventions Used in This Book
The following typographical conventions are used in this book:
- Italic: Indicates new terms, URLs, email addresses, filenames, and file extensions.
Constant width: Used for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords.
The following markers are used to identify code that isn't right in some way.
| Marker | Meaning |
|---|---|
 | This code does not compile! |
 | This code does not produce the desired behavior. |
Acknowledgments
My thanks go to the people who helped make this book possible:
- The technical reviewers who gave expert and detailed feedback on all aspects of the text: Pietro Albini, Jess Males, Mike Capp, and especially Carol Nichols.
- My editors at O'Reilly: Jeff Bleiel, Brian Guerin, and Katie Tozer.
- Tiziano Santoro, from whom I originally learned many things about Rust.
- Danny Elfanbaum, who provided vital technical assistance for dealing with the AsciiDoc formatting of the book.
- Diligent readers of the original web version of the book, in particular:
- Julian Rosse, who spotted dozens of typos and other errors in the online text.
- Martin Disch, who pointed out potential improvements and inaccuracies in several Items.
- Chris Fleetwood, Sergey Kaunov, Clifford Matthews, Remo Senekowitsch, Kirill Zaborsky, and an anonymous Proton Mail user, who pointed out mistakes in the text.
- My family, who coped with many weekends when I was distracted by writing.
