Everything You Need To Know About Rust Macros

Everything You Need To Know About Rust Macros

Rust has two types of macros: Declarative macros, Procedural macros. In this tutorial, we’ll cover everything you need to know about Rust macros, including an introduction to macros in Rust and a demonstration of how to use Rust macros with examples.

In this tutorial, we’ll cover everything you need to know about Rust macros, including an introduction to macros in Rust and a demonstration of how to use Rust macros with examples.

We’ll cover the following:

  • What are Rust macros?
  • Types of macros in Rust
  • Declarative macros in Rust
    • Creating declarative macros
    • Advanced parsing in Rust with declarative macros
    • Parsing the name and field of a struct
    • Parsing metadata from the struct
    • Limitations of declarative macros
  • Procedural macros in Rust
    • Attribute-like macros
    • Custom derive macros
    • Function-like macros

What are Rust macros?

Rust has excellent support for macros. Macros enable you to write code that writes other code, which is known as metaprogramming.

Macros provide functionality similar to functions but without the runtime cost. There is some compile-time cost, however, since macros are expanded during compile time.

Rust macros are very different from macros in C. Rust macros are applied to the token tree whereas C macros are text substitution.

Types of macros in Rust

Rust has two types of macros:

  1. Declarative macros enable you to write something similar to a match expression that operates on the Rust code you provide as arguments. It uses the code you provide to generate code that replaces the macro invocation
  2. Procedural macros allow you to operate on the abstract syntax tree (AST) of the Rust code it is given. A proc macro is a function from a TokenStream (or two) to another TokenStream, where the output replaces the macro invocation

Let’s zoom in on both declarative and procedural macros and explore some examples of how to use macros in Rust.

rust programming developer

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