// Copyright 2018 Syn Developers
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Syn is a parsing library for parsing a stream of Rust tokens into a syntax
//! tree of Rust source code.
//!
//! Currently this library is geared toward the [custom derive] use case but
//! contains some APIs that may be useful for Rust procedural macros more
//! generally.
//!
//! [custom derive]: https://github.com/rust-lang/rfcs/blob/master/text/1681-macros-1.1.md
//!
//! - **Data structures** — Syn provides a complete syntax tree that can
//! represent any valid Rust source code. The syntax tree is rooted at
//! [`syn::File`] which represents a full source file, but there are other
//! entry points that may be useful to procedural macros including
//! [`syn::Item`], [`syn::Expr`] and [`syn::Type`].
//!
//! - **Custom derives** — Of particular interest to custom derives is
//! [`syn::DeriveInput`] which is any of the three legal input items to a
//! derive macro. An example below shows using this type in a library that can
//! derive implementations of a trait of your own.
//!
//! - **Parser combinators** — Parsing in Syn is built on a suite of public
//! parser combinator macros that you can use for parsing any token-based
//! syntax you dream up within a `functionlike!(...)` procedural macro. Every
//! syntax tree node defined by Syn is individually parsable and may be used
//! as a building block for custom syntaxes, or you may do it all yourself
//! working from the most primitive tokens.
//!
//! - **Location information** — Every token parsed by Syn is associated with a
//! `Span` that tracks line and column information back to the source of that
//! token. These spans allow a procedural macro to display detailed error
//! messages pointing to all the right places in the user's code. There is an
//! example of this below.
//!
//! - **Feature flags** — Functionality is aggressively feature gated so your
//! procedural macros enable only what they need, and do not pay in compile
//! time for all the rest.
//!
//! [`syn::File`]: struct.File.html
//! [`syn::Item`]: enum.Item.html
//! [`syn::Expr`]: enum.Expr.html
//! [`syn::Type`]: enum.Type.html
//! [`syn::DeriveInput`]: struct.DeriveInput.html
//!
//! *Version requirement: Syn supports any compiler version back to Rust's very
//! first support for procedural macros in Rust 1.15.0. Some features especially
//! around error reporting are only available in newer compilers or on the
//! nightly channel.*
//!
//! ## Example of a custom derive
//!
//! The canonical custom derive using Syn looks like this. We write an ordinary
//! Rust function tagged with a `proc_macro_derive` attribute and the name of
//! the trait we are deriving. Any time that derive appears in the user's code,
//! the Rust compiler passes their data structure as tokens into our macro. We
//! get to execute arbitrary Rust code to figure out what to do with those
//! tokens, then hand some tokens back to the compiler to compile into the
//! user's crate.
//!
//! [`TokenStream`]: https://doc.rust-lang.org/proc_macro/struct.TokenStream.html
//!
//! ```toml
//! [dependencies]
//! syn = "0.12"
//! quote = "0.4"
//!
//! [lib]
//! proc-macro = true
//! ```
//!
//! ```rust
//! extern crate proc_macro;
//! extern crate syn;
//!
//! #[macro_use]
//! extern crate quote;
//!
//! use proc_macro::TokenStream;
//! use syn::DeriveInput;
//!
//! # const IGNORE_TOKENS: &str = stringify! {
//! #[proc_macro_derive(MyMacro)]
//! # };
//! pub fn my_macro(input: TokenStream) -> TokenStream {
//! // Parse the input tokens into a syntax tree
//! let input: DeriveInput = syn::parse(input).unwrap();
//!
//! // Build the output, possibly using quasi-quotation
//! let expanded = quote! {
//! // ...
//! };
//!
//! // Hand the output tokens back to the compiler
//! expanded.into()
//! }
//! #
//! # fn main() {}
//! ```
//!
//! The [`heapsize`] example directory shows a complete working Macros 1.1
//! implementation of a custom derive. It works on any Rust compiler \>=1.15.0.
//! The example derives a `HeapSize` trait which computes an estimate of the
//! amount of heap memory owned by a value.
//!
//! [`heapsize`]: https://github.com/dtolnay/syn/tree/master/examples/heapsize
//!
//! ```rust
//! pub trait HeapSize {
//! /// Total number of bytes of heap memory owned by `self`.
//! fn heap_size_of_children(&self) -> usize;
//! }
//! ```
//!
//! The custom derive allows users to write `#[derive(HeapSize)]` on data
//! structures in their program.
//!
//! ```rust
//! # const IGNORE_TOKENS: &str = stringify! {
//! #[derive(HeapSize)]
//! # };
//! struct Demo<'a, T: ?Sized> {
//! a: Box<T>,
//! b: u8,
//! c: &'a str,
//! d: String,
//! }
//! ```
//!
//! ## Spans and error reporting
//!
//! The [`heapsize2`] example directory is an extension of the `heapsize`
//! example that demonstrates some of the hygiene and error reporting properties
//! of Macros 2.0. This example currently requires a nightly Rust compiler
//! \>=1.24.0-nightly but we are working to stabilize all of the APIs involved.
//!
//! [`heapsize2`]: https://github.com/dtolnay/syn/tree/master/examples/heapsize2
//!
//! The token-based procedural macro API provides great control over where the
//! compiler's error messages are displayed in user code. Consider the error the
//! user sees if one of their field types does not implement `HeapSize`.
//!
//! ```rust
//! # const IGNORE_TOKENS: &str = stringify! {
//! #[derive(HeapSize)]
//! # };
//! struct Broken {
//! ok: String,
//! bad: std::thread::Thread,
//! }
//! ```
//!
//! In the Macros 1.1 string-based procedural macro world, the resulting error
//! would point unhelpfully to the invocation of the derive macro and not to the
//! actual problematic field.
//!
//! ```text
//! error[E0599]: no method named `heap_size_of_children` found for type `std::thread::Thread` in the current scope
//! --> src/main.rs:4:10
//! |
//! 4 | #[derive(HeapSize)]
//! | ^^^^^^^^
//! ```
//!
//! By tracking span information all the way through the expansion of a
//! procedural macro as shown in the `heapsize2` example, token-based macros in
//! Syn are able to trigger errors that directly pinpoint the source of the
//! problem.
//!
//! ```text
//! error[E0277]: the trait bound `std::thread::Thread: HeapSize` is not satisfied
//! --> src/main.rs:7:5
//! |
//! 7 | bad: std::thread::Thread,
//! | ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `HeapSize` is not implemented for `Thread`
//! ```
//!
//! ## Parsing a custom syntax using combinators
//!
//! The [`lazy-static`] example directory shows the implementation of a
//! `functionlike!(...)` procedural macro in which the input tokens are parsed
//! using [`nom`]-style parser combinators.
//!
//! [`lazy-static`]: https://github.com/dtolnay/syn/tree/master/examples/lazy-static
//! [`nom`]: https://github.com/Geal/nom
//!
//! The example reimplements the popular `lazy_static` crate from crates.io as a
//! procedural macro.
//!
//! ```
//! # macro_rules! lazy_static {
//! # ($($tt:tt)*) => {}
//! # }
//! #
//! lazy_static! {
//! static ref USERNAME: Regex = Regex::new("^[a-z0-9_-]{3,16}$").unwrap();
//! }
//! ```
//!
//! The implementation shows how to trigger custom warnings and error messages
//! on the macro input.
//!
//! ```text
//! warning: come on, pick a more creative name
//! --> src/main.rs:10:16
//! |
//! 10 | static ref FOO: String = "lazy_static".to_owned();
//! | ^^^
//! ```
//!
//! ## Debugging
//!
//! When developing a procedural macro it can be helpful to look at what the
//! generated code looks like. Use `cargo rustc -- -Zunstable-options
//! --pretty=expanded` or the [`cargo expand`] subcommand.
//!
//! [`cargo expand`]: https://github.com/dtolnay/cargo-expand
//!
//! To show the expanded code for some crate that uses your procedural macro,
//! run `cargo expand` from that crate. To show the expanded code for one of
//! your own test cases, run `cargo expand --test the_test_case` where the last
//! argument is the name of the test file without the `.rs` extension.
//!
//! This write-up by Brandon W Maister discusses debugging in more detail:
//! [Debugging Rust's new Custom Derive system][debugging].
//!
//! [debugging]: https://quodlibetor.github.io/posts/debugging-rusts-new-custom-derive-system/
//!
//! ## Optional features
//!
//! Syn puts a lot of functionality behind optional features in order to
//! optimize compile time for the most common use cases. The following features
//! are available.
//!
//! - **`derive`** *(enabled by default)* — Data structures for representing the
//! possible input to a custom derive, including structs and enums and types.
//! - **`full`** — Data structures for representing the syntax tree of all valid
//! Rust source code, including items and expressions.
//! - **`parsing`** *(enabled by default)* — Ability to parse input tokens into
//! a syntax tree node of a chosen type.
//! - **`printing`** *(enabled by default)* — Ability to print a syntax tree
//! node as tokens of Rust source code.
//! - **`visit`** — Trait for traversing a syntax tree.
//! - **`visit-mut`** — Trait for traversing and mutating in place a syntax
//! tree.
//! - **`fold`** — Trait for transforming an owned syntax tree.
//! - **`clone-impls`** *(enabled by default)* — Clone impls for all syntax tree
//! types.
//! - **`extra-traits`** — Debug, Eq, PartialEq, Hash impls for all syntax tree
//! types.
// Syn types in rustdoc of other crates get linked to here.
extern crate proc_macro2;
extern crate proc_macro;
extern crate unicode_xid;
extern crate quote;
pub use ;
pub use ;
pub use ;
pub use ;
pub use ;
pub use ;
pub use Ident;
pub use ;
pub use File;
pub use Lifetime;
pub use ;
pub use ;
pub use ;
pub use ;
pub use ;
pub use ;
pub use PathTokens;
// Not public API except the `parse_quote!` macro.
pub use *;
////////////////////////////////////////////////////////////////////////////////
use ;
use ParseError;
// Not public API.
pub use parse_error;
/// Parse tokens of source code into the chosen syntax tree node.
///
/// This is preferred over parsing a string because tokens are able to preserve
/// information about where in the user's code they were originally written (the
/// "span" of the token), possibly allowing the compiler to produce better error
/// messages.
///
/// This function parses a `proc_macro::TokenStream` which is the type used for
/// interop with the compiler in a procedural macro. To parse a
/// `proc_macro2::TokenStream`, use [`syn::parse2`] instead.
///
/// [`syn::parse2`]: fn.parse2.html
///
/// *This function is available if Syn is built with the `"parsing"` feature.*
///
/// # Examples
///
/// ```rust
/// extern crate proc_macro;
/// use proc_macro::TokenStream;
///
/// extern crate syn;
///
/// #[macro_use]
/// extern crate quote;
///
/// use syn::DeriveInput;
///
/// # const IGNORE_TOKENS: &str = stringify! {
/// #[proc_macro_derive(MyMacro)]
/// # };
/// pub fn my_macro(input: TokenStream) -> TokenStream {
/// // Parse the tokens into a syntax tree
/// let ast: DeriveInput = syn::parse(input).unwrap();
///
/// // Build the output, possibly using quasi-quotation
/// let expanded = quote! {
/// /* ... */
/// };
///
/// // Convert into a token stream and return it
/// expanded.into()
/// }
/// #
/// # fn main() {}
/// ```
/// Parse a proc-macro2 token stream into the chosen syntax tree node.
///
/// This function parses a `proc_macro2::TokenStream` which is commonly useful
/// when the input comes from a node of the Syn syntax tree, for example the tts
/// of a [`Macro`] node. When in a procedural macro parsing the
/// `proc_macro::TokenStream` provided by the compiler, use [`syn::parse`]
/// instead.
///
/// [`Macro`]: struct.Macro.html
/// [`syn::parse`]: fn.parse.html
///
/// *This function is available if Syn is built with the `"parsing"` feature.*
/// Parse a string of Rust code into the chosen syntax tree node.
///
/// *This function is available if Syn is built with the `"parsing"` feature.*
///
/// # Hygiene
///
/// Every span in the resulting syntax tree will be set to resolve at the macro
/// call site.
///
/// # Examples
///
/// ```rust
/// extern crate syn;
/// #
/// #
/// # type Result<T> = std::result::Result<T, Box<std::error::Error>>;
///
/// use syn::Expr;
///
/// fn run() -> Result<()> {
/// let code = "assert_eq!(u8::max_value(), 255)";
/// let expr = syn::parse_str::<Expr>(code)?;
/// println!("{:#?}", expr);
/// Ok(())
/// }
/// #
/// # fn main() { run().unwrap() }
/// ```
// FIXME the name parse_file makes it sound like you might pass in a path to a
// file, rather than the content.
/// Parse the content of a file of Rust code.
///
/// This is different from `syn::parse_str::<File>(content)` in two ways:
///
/// - It discards a leading byte order mark `\u{FEFF}` if the file has one.
/// - It preserves the shebang line of the file, such as `#!/usr/bin/env rustx`.
///
/// If present, either of these would be an error using `from_str`.
///
/// *This function is available if Syn is built with the `"parsing"` feature.*
///
/// # Examples
///
/// ```rust,no_run
/// extern crate syn;
/// #
/// #
/// # type Result<T> = std::result::Result<T, Box<std::error::Error>>;
///
/// use std::fs::File;
/// use std::io::Read;
///
/// fn run() -> Result<()> {
/// let mut file = File::open("path/to/code.rs")?;
/// let mut content = String::new();
/// file.read_to_string(&mut content)?;
///
/// let ast = syn::parse_file(&content)?;
/// if let Some(shebang) = ast.shebang {
/// println!("{}", shebang);
/// }
/// println!("{} items", ast.items.len());
///
/// Ok(())
/// }
/// #
/// # fn main() { run().unwrap() }
/// ```
;