1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97
//! [![github]](https://github.com/dtolnay/readonly) [![crates-io]](https://crates.io/crates/readonly) [![docs-rs]](https://docs.rs/readonly) //! //! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github //! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust //! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,PHN2ZyByb2xlPSJpbWciIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgdmlld0JveD0iMCAwIDUxMiA1MTIiPjxwYXRoIGZpbGw9IiNmNWY1ZjUiIGQ9Ik00ODguNiAyNTAuMkwzOTIgMjE0VjEwNS41YzAtMTUtOS4zLTI4LjQtMjMuNC0zMy43bC0xMDAtMzcuNWMtOC4xLTMuMS0xNy4xLTMuMS0yNS4zIDBsLTEwMCAzNy41Yy0xNC4xIDUuMy0yMy40IDE4LjctMjMuNCAzMy43VjIxNGwtOTYuNiAzNi4yQzkuMyAyNTUuNSAwIDI2OC45IDAgMjgzLjlWMzk0YzAgMTMuNiA3LjcgMjYuMSAxOS45IDMyLjJsMTAwIDUwYzEwLjEgNS4xIDIyLjEgNS4xIDMyLjIgMGwxMDMuOS01MiAxMDMuOSA1MmMxMC4xIDUuMSAyMi4xIDUuMSAzMi4yIDBsMTAwLTUwYzEyLjItNi4xIDE5LjktMTguNiAxOS45LTMyLjJWMjgzLjljMC0xNS05LjMtMjguNC0yMy40LTMzLjd6TTM1OCAyMTQuOGwtODUgMzEuOXYtNjguMmw4NS0zN3Y3My4zek0xNTQgMTA0LjFsMTAyLTM4LjIgMTAyIDM4LjJ2LjZsLTEwMiA0MS40LTEwMi00MS40di0uNnptODQgMjkxLjFsLTg1IDQyLjV2LTc5LjFsODUtMzguOHY3NS40em0wLTExMmwtMTAyIDQxLjQtMTAyLTQxLjR2LS42bDEwMi0zOC4yIDEwMiAzOC4ydi42em0yNDAgMTEybC04NSA0Mi41di03OS4xbDg1LTM4Ljh2NzUuNHptMC0xMTJsLTEwMiA0MS40LTEwMi00MS40di0uNmwxMDItMzguMiAxMDIgMzguMnYuNnoiPjwvcGF0aD48L3N2Zz4K //! //! <br> //! //! Struct fields that can be read and written from within the same module, but //! from outside the module can only be read. //! //! # Syntax //! //! Place `#[readonly::make]` on a braced struct or tuple struct. This will make //! all fields of the struct publicly readable according to their individual //! visibility specifiers, but not writable from other modules. //! //! ``` //! mod m { //! #[readonly::make] //! pub struct S { //! pub n: i32, //! } //! //! impl S { //! pub fn demo(&mut self) { //! // Can read and write from inside the same module. //! println!("{}", self.n); //! self.n += 1; //! } //! } //! } //! //! fn demo(s: &mut m::S) { //! // From outside the module, can only read. //! println!("{}", s.n); //! //! // Does not compile: //! //s.n += 1; //! } //! ``` //! //! The error appears as follows. //! //! ```console //! error[E0594]: cannot assign to data in a dereference of `m::S` //! --> readme.rs:21:5 //! | //! 21 | s.n += 1; //! | ^^^^^^^^ cannot assign //! ``` //! //! Optionally, place `#[readonly]` on individual struct fields to make just //! those fields publicly readable, without affecting other fields of the //! struct. //! //! ``` //! # mod m { //! #[readonly::make] //! pub struct S { //! // This field can be read (but not written) by super. //! #[readonly] //! pub(super) readable: i32, //! //! // This field can be neither read nor written by other modules. //! private: i32, //! } //! # } //! ``` extern crate proc_macro; mod args; mod expand; use crate::args::Args; use proc_macro::TokenStream; use quote::quote; use syn::{parse_macro_input, DeriveInput}; #[proc_macro_attribute] pub fn make(args: TokenStream, tokens: TokenStream) -> TokenStream { let original = tokens.clone(); let args = parse_macro_input!(args as Args); let input = parse_macro_input!(tokens as DeriveInput); expand::readonly(args, input) .unwrap_or_else(|e| { let original = proc_macro2::TokenStream::from(original); let compile_error = e.to_compile_error(); quote! { #original #compile_error } }) .into() }