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If this is your first time working with procedural macros, I would recommend starting with the derive(Builder) project. This will get you comfortable with traversing syntax trees and constructing output source code. These are the two fundamental components of a procedural macro.

Derive macro: derive(Builder)

This macro generates the boilerplate code involved in implementing the builder pattern in Rust. Builders are a mechanism for instantiating structs, especially structs with many fields, and especially if many of those fields are optional or the set of fields may need to grow backward compatibly over time.

There are a few different possibilities for expressing builders in Rust. Unless you have a strong pre-existing preference, to keep things simple for this project I would recommend following the example of the standard library's std::process::Command builder in which the setter methods each receive and return &mut self to allow chained method calls. Callers will invoke the macro as follows.

This project covers:

• traversing syntax trees;

• constructing output source code;

• processing helper attributes to customize the generated code.

Project skeleton is located under the builder directory.

01 the DeriveInput

DeriveInput in syn - Rust

Data structure sent to a `proc_macro_derive` macro.

https://docs.rs/syn/2.0.72/syn/struct.DeriveInput.html

Struct syn::Attribute

• Outer attributes like #[repr(transparent)]. These appear outside or in front of the item they describe.

• Inner attributes like #![feature(proc_macro)]. These appear inside of the item they describe, usually a module.

• Outer one-line doc comments like /// Example.

• Inner one-line doc comments like //! Please file an issue.

• Outer documentation blocks /** Example */.

• Inner documentation blocks /*! Please file an issue */.

Enum syn::AttrStyle

• #[repr(transparent)]

• /// # Example

• /** Please file an issue */

• #![feature(proc_macro)]

• //! # Example

• /*! Please file an issue */

Struct syn::token::Pound

Enum syn::Meta

02-create-builder

Ident in syn - Rust

A word of Rust code, which may be a keyword or legal variable name.

https://docs.rs/syn/2.0/syn/struct.Ident.html