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//! Centralized logic for parsing and attributes.
//!
//! ## Architecture
//! This crate is part of a series of crates that handle attribute processing.
//! - [rustc_attr_data_structures](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_attr_data_structures/index.html): Defines the data structures that store parsed attributes
//! - [rustc_attr_parsing](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_attr_parsing/index.html): This crate, handles the parsing of attributes
//! - (planned) rustc_attr_validation: Will handle attribute validation
//!
//! The separation between data structures and parsing follows the principle of separation of concerns.
//! Data structures (`rustc_attr_data_structures`) define what attributes look like after parsing.
//! This crate (`rustc_attr_parsing`) handles how to convert raw tokens into those structures.
//! This split allows other parts of the compiler to use the data structures without needing
//! the parsing logic, making the codebase more modular and maintainable.
//!
//! ## Background
//! Previously, the compiler had a single attribute definition (`ast::Attribute`) with parsing and
//! validation scattered throughout the codebase. This was reorganized for better maintainability
//! (see [#131229](https://github.com/rust-lang/rust/issues/131229)).
//!
//! ## Types of Attributes
//! In Rust, attributes are markers that can be attached to items. They come in two main categories.
//!
//! ### 1. Active Attributes
//! These are attribute-like proc-macros that expand into other Rust code.
//! They can be either user-defined or compiler-provided. Examples of compiler-provided active attributes:
//! - `#[derive(...)]`: Expands into trait implementations
//! - `#[cfg()]`: Expands based on configuration
//! - `#[cfg_attr()]`: Conditional attribute application
//!
//! ### 2. Inert Attributes
//! These are pure markers that don't expand into other code. They guide the compilation process.
//! They can be user-defined (in proc-macro helpers) or built-in. Examples of built-in inert attributes:
//! - `#[stable()]`: Marks stable API items
//! - `#[inline()]`: Suggests function inlining
//! - `#[repr()]`: Controls type representation
//!
//! ```text
//! Active Inert
//! ┌──────────────────────┬──────────────────────┐
//! │ (mostly in) │ these are parsed │
//! │ rustc_builtin_macros │ here! │
//! │ │ │
//! │ #[derive(...)] │ #[stable()] │
//! Built-in │ #[cfg()] │ #[inline()] │
//! │ #[cfg_attr()] │ #[repr()] │
//! │ │ │
//! ├──────────────────────┼──────────────────────┤
//! │ │ │
//! │ │ `b` in │
//! │ │ #[proc_macro_derive( │
//! User created │ #[proc_macro_attr()] │ a, │
//! │ │ attributes(b) │
//! │ │ ] │
//! └──────────────────────┴──────────────────────┘
//! ```
//!
//! ## How This Crate Works
//! In this crate, syntactical attributes (sequences of tokens that look like
//! `#[something(something else)]`) are parsed into more semantic attributes, markers on items.
//! Multiple syntactic attributes might influence a single semantic attribute. For example,
//! `#[stable(...)]` and `#[unstable()]` cannot occur together, and both semantically define
//! a "stability" of an item. So, the stability attribute has an
//! [`AttributeParser`](attributes::AttributeParser) that recognizes both the `#[stable()]`
//! and `#[unstable()]` syntactic attributes, and at the end produce a single
//! [`AttributeKind::Stability`](rustc_attr_data_structures::AttributeKind::Stability).
//!
//! When multiple instances of the same attribute are allowed, they're combined into a single
//! semantic attribute. For example:
//!
//! ```rust
//! #[repr(C)]
//! #[repr(packed)]
//! struct Meow {}
//! ```
//!
//! This is equivalent to `#[repr(C, packed)]` and results in a single `AttributeKind::Repr`
//! containing both `C` and `packed` annotations.
// tidy-alphabetical-start
#![allow(internal_features)]
#![doc(rust_logo)]
#![feature(rustdoc_internals)]
#![recursion_limit = "256"]
// tidy-alphabetical-end
#[macro_use]
mod attributes;
pub(crate) mod context;
mod lints;
pub mod parser;
mod session_diagnostics;
pub use attributes::cfg::{CFG_TEMPLATE, EvalConfigResult, eval_config_entry, parse_cfg_attr};
pub use attributes::cfg_old::*;
pub use attributes::util::{
find_crate_name, is_builtin_attr, is_doc_alias_attrs_contain_symbol, parse_version,
};
pub use context::{AttributeParser, Early, Late, OmitDoc, ShouldEmit};
pub use lints::emit_attribute_lint;
rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
|
