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// 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 = "0.14" //! quote = "0.6" //! //! [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. //! - **`proc-macro`** *(enabled by default)* — Runtime dependency on the //! dynamic library libproc_macro from rustc toolchain. // Syn types in rustdoc of other crates get linked to here. #![doc(html_root_url = "https://docs.rs/syn/0.14.9")] #![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))] // Ignored clippy lints. #![cfg_attr( feature = "cargo-clippy", allow( const_static_lifetime, doc_markdown, large_enum_variant, match_bool, redundant_closure, needless_pass_by_value, redundant_field_names, trivially_copy_pass_by_ref ) )] // Ignored clippy_pedantic lints. #![cfg_attr( feature = "cargo-clippy", allow( cast_possible_truncation, cast_possible_wrap, if_not_else, indexing_slicing, items_after_statements, shadow_unrelated, similar_names, single_match_else, stutter, unseparated_literal_suffix, use_self, used_underscore_binding ) )] #[cfg(all( not(all(target_arch = "wasm32", target_os = "unknown")), feature = "proc-macro" ))] extern crate proc_macro; extern crate proc_macro2; extern crate unicode_xid; #[cfg(feature = "printing")] extern crate quote; #[cfg(feature = "parsing")] #[macro_use] #[doc(hidden)] pub mod parsers; #[macro_use] mod macros; #[macro_use] pub mod token; pub use proc_macro2::Ident; #[cfg(any(feature = "full", feature = "derive"))] mod attr; #[cfg(any(feature = "full", feature = "derive"))] pub use attr::{AttrStyle, Attribute, Meta, MetaList, MetaNameValue, NestedMeta}; #[cfg(any(feature = "full", feature = "derive"))] mod data; #[cfg(any(feature = "full", feature = "derive"))] pub use data::{ Field, Fields, FieldsNamed, FieldsUnnamed, Variant, VisCrate, VisPublic, VisRestricted, Visibility, }; #[cfg(any(feature = "full", feature = "derive"))] mod expr; #[cfg(any(feature = "full", feature = "derive"))] pub use expr::{ Expr, ExprArray, ExprAssign, ExprAssignOp, ExprBinary, ExprBlock, ExprBox, ExprBreak, ExprCall, ExprCast, ExprCatch, ExprClosure, ExprContinue, ExprField, ExprForLoop, ExprGroup, ExprIf, ExprIfLet, ExprInPlace, ExprIndex, ExprLit, ExprLoop, ExprMacro, ExprMatch, ExprMethodCall, ExprParen, ExprPath, ExprRange, ExprReference, ExprRepeat, ExprReturn, ExprStruct, ExprTry, ExprTuple, ExprType, ExprUnary, ExprUnsafe, ExprVerbatim, ExprWhile, ExprWhileLet, ExprYield, Index, Member, }; #[cfg(feature = "full")] pub use expr::{ Arm, Block, FieldPat, FieldValue, GenericMethodArgument, Label, Local, MethodTurbofish, Pat, PatBox, PatIdent, PatLit, PatMacro, PatPath, PatRange, PatRef, PatSlice, PatStruct, PatTuple, PatTupleStruct, PatVerbatim, PatWild, RangeLimits, Stmt, }; #[cfg(any(feature = "full", feature = "derive"))] mod generics; #[cfg(any(feature = "full", feature = "derive"))] pub use generics::{ BoundLifetimes, ConstParam, GenericParam, Generics, LifetimeDef, PredicateEq, PredicateLifetime, PredicateType, TraitBound, TraitBoundModifier, TypeParam, TypeParamBound, WhereClause, WherePredicate, }; #[cfg(all( any(feature = "full", feature = "derive"), feature = "printing" ))] pub use generics::{ImplGenerics, Turbofish, TypeGenerics}; #[cfg(feature = "full")] mod item; #[cfg(feature = "full")] pub use item::{ ArgCaptured, ArgSelf, ArgSelfRef, FnArg, FnDecl, ForeignItem, ForeignItemFn, ForeignItemStatic, ForeignItemType, ForeignItemVerbatim, ImplItem, ImplItemConst, ImplItemMacro, ImplItemMethod, ImplItemType, ImplItemVerbatim, Item, ItemConst, ItemEnum, ItemExternCrate, ItemFn, ItemForeignMod, ItemImpl, ItemMacro, ItemMacro2, ItemMod, ItemStatic, ItemStruct, ItemTrait, ItemType, ItemUnion, ItemUse, ItemVerbatim, MethodSig, TraitItem, TraitItemConst, TraitItemMacro, TraitItemMethod, TraitItemType, TraitItemVerbatim, UseGlob, UseGroup, UseName, UsePath, UseRename, UseTree, }; #[cfg(feature = "full")] mod file; #[cfg(feature = "full")] pub use file::File; #[cfg(any(feature = "full", feature = "derive"))] mod lifetime; #[cfg(any(feature = "full", feature = "derive"))] pub use lifetime::Lifetime; #[cfg(any(feature = "full", feature = "derive"))] mod lit; #[cfg(any(feature = "full", feature = "derive"))] pub use lit::{ FloatSuffix, IntSuffix, Lit, LitBool, LitByte, LitByteStr, LitChar, LitFloat, LitInt, LitStr, LitVerbatim, StrStyle, }; #[cfg(any(feature = "full", feature = "derive"))] mod mac; #[cfg(any(feature = "full", feature = "derive"))] pub use mac::{Macro, MacroDelimiter}; #[cfg(any(feature = "full", feature = "derive"))] mod derive; #[cfg(feature = "derive")] pub use derive::{Data, DataEnum, DataStruct, DataUnion, DeriveInput}; #[cfg(any(feature = "full", feature = "derive"))] mod op; #[cfg(any(feature = "full", feature = "derive"))] pub use op::{BinOp, UnOp}; #[cfg(any(feature = "full", feature = "derive"))] mod ty; #[cfg(any(feature = "full", feature = "derive"))] pub use ty::{ Abi, BareFnArg, BareFnArgName, ReturnType, Type, TypeArray, TypeBareFn, TypeGroup, TypeImplTrait, TypeInfer, TypeMacro, TypeNever, TypeParen, TypePath, TypePtr, TypeReference, TypeSlice, TypeTraitObject, TypeTuple, TypeVerbatim, }; #[cfg(any(feature = "full", feature = "derive"))] mod path; #[cfg(all( any(feature = "full", feature = "derive"), feature = "printing" ))] pub use path::PathTokens; #[cfg(any(feature = "full", feature = "derive"))] pub use path::{ AngleBracketedGenericArguments, Binding, GenericArgument, ParenthesizedGenericArguments, Path, PathArguments, PathSegment, QSelf, }; #[cfg(feature = "parsing")] pub mod buffer; pub mod punctuated; #[cfg(feature = "parsing")] pub mod synom; #[cfg(any(feature = "full", feature = "derive"))] mod tt; // Not public API except the `parse_quote!` macro. #[cfg(feature = "parsing")] #[doc(hidden)] pub mod parse_quote; #[cfg(all(feature = "parsing", feature = "printing"))] pub mod spanned; #[cfg(all(feature = "parsing", feature = "full"))] mod verbatim; mod gen { /// Syntax tree traversal to walk a shared borrow of a syntax tree. /// /// Each method of the [`Visit`] trait is a hook that can be overridden to /// customize the behavior when visiting the corresponding type of node. By /// default, every method recursively visits the substructure of the input /// by invoking the right visitor method of each of its fields. /// /// [`Visit`]: trait.Visit.html /// /// ```rust /// # use syn::{Attribute, BinOp, Expr, ExprBinary}; /// # /// pub trait Visit<'ast> { /// /* ... */ /// /// fn visit_expr_binary(&mut self, node: &'ast ExprBinary) { /// for attr in &node.attrs { /// self.visit_attribute(attr); /// } /// self.visit_expr(&*node.left); /// self.visit_bin_op(&node.op); /// self.visit_expr(&*node.right); /// } /// /// /* ... */ /// # fn visit_attribute(&mut self, node: &'ast Attribute); /// # fn visit_expr(&mut self, node: &'ast Expr); /// # fn visit_bin_op(&mut self, node: &'ast BinOp); /// } /// ``` /// /// *This module is available if Syn is built with the `"visit"` feature.* #[cfg(feature = "visit")] pub mod visit; /// Syntax tree traversal to mutate an exclusive borrow of a syntax tree in /// place. /// /// Each method of the [`VisitMut`] trait is a hook that can be overridden /// to customize the behavior when mutating the corresponding type of node. /// By default, every method recursively visits the substructure of the /// input by invoking the right visitor method of each of its fields. /// /// [`VisitMut`]: trait.VisitMut.html /// /// ```rust /// # use syn::{Attribute, BinOp, Expr, ExprBinary}; /// # /// pub trait VisitMut { /// /* ... */ /// /// fn visit_expr_binary_mut(&mut self, node: &mut ExprBinary) { /// for attr in &mut node.attrs { /// self.visit_attribute_mut(attr); /// } /// self.visit_expr_mut(&mut *node.left); /// self.visit_bin_op_mut(&mut node.op); /// self.visit_expr_mut(&mut *node.right); /// } /// /// /* ... */ /// # fn visit_attribute_mut(&mut self, node: &mut Attribute); /// # fn visit_expr_mut(&mut self, node: &mut Expr); /// # fn visit_bin_op_mut(&mut self, node: &mut BinOp); /// } /// ``` /// /// *This module is available if Syn is built with the `"visit-mut"` /// feature.* #[cfg(feature = "visit-mut")] pub mod visit_mut; /// Syntax tree traversal to transform the nodes of an owned syntax tree. /// /// Each method of the [`Fold`] trait is a hook that can be overridden to /// customize the behavior when transforming the corresponding type of node. /// By default, every method recursively visits the substructure of the /// input by invoking the right visitor method of each of its fields. /// /// [`Fold`]: trait.Fold.html /// /// ```rust /// # use syn::{Attribute, BinOp, Expr, ExprBinary}; /// # /// pub trait Fold { /// /* ... */ /// /// fn fold_expr_binary(&mut self, node: ExprBinary) -> ExprBinary { /// ExprBinary { /// attrs: node.attrs /// .into_iter() /// .map(|attr| self.fold_attribute(attr)) /// .collect(), /// left: Box::new(self.fold_expr(*node.left)), /// op: self.fold_bin_op(node.op), /// right: Box::new(self.fold_expr(*node.right)), /// } /// } /// /// /* ... */ /// # fn fold_attribute(&mut self, node: Attribute) -> Attribute; /// # fn fold_expr(&mut self, node: Expr) -> Expr; /// # fn fold_bin_op(&mut self, node: BinOp) -> BinOp; /// } /// ``` /// /// *This module is available if Syn is built with the `"fold"` feature.* #[cfg(feature = "fold")] pub mod fold; #[cfg(any(feature = "full", feature = "derive"))] #[path = "../gen_helper.rs"] mod helper; } pub use gen::*; //////////////////////////////////////////////////////////////////////////////// #[cfg(feature = "parsing")] use synom::{Parser, Synom}; #[cfg(feature = "parsing")] mod error; #[cfg(feature = "parsing")] use error::ParseError; // Not public API. #[cfg(feature = "parsing")] #[doc(hidden)] pub use error::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 both the `"parsing"` and /// `"proc-macro"` features.* /// /// # 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() {} /// ``` #[cfg(all( not(all(target_arch = "wasm32", target_os = "unknown")), feature = "parsing", feature = "proc-macro" ))] pub fn parse<T>(tokens: proc_macro::TokenStream) -> Result<T, ParseError> where T: Synom, { parse2(tokens.into()) } /// 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.* #[cfg(feature = "parsing")] pub fn parse2<T>(tokens: proc_macro2::TokenStream) -> Result<T, ParseError> where T: Synom, { let parser = T::parse; parser.parse2(tokens).map_err(|err| match T::description() { Some(s) => ParseError::new(format!("failed to parse {}: {}", s, err)), None => err, }) } /// 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() } /// ``` #[cfg(feature = "parsing")] pub fn parse_str<T: Synom>(s: &str) -> Result<T, ParseError> { match s.parse() { Ok(tts) => parse2(tts), Err(_) => Err(ParseError::new("error while lexing input string")), } } // 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"` and `"full"` features.* /// /// # 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() } /// ``` #[cfg(all(feature = "parsing", feature = "full"))] pub fn parse_file(mut content: &str) -> Result<File, ParseError> { // Strip the BOM if it is present const BOM: &'static str = "\u{feff}"; if content.starts_with(BOM) { content = &content[BOM.len()..]; } let mut shebang = None; if content.starts_with("#!") && !content.starts_with("#![") { if let Some(idx) = content.find('\n') { shebang = Some(content[..idx].to_string()); content = &content[idx..]; } else { shebang = Some(content.to_string()); content = ""; } } let mut file: File = parse_str(content)?; file.shebang = shebang; Ok(file) } #[cfg(all( any(feature = "full", feature = "derive"), feature = "printing" ))] struct TokensOrDefault<'a, T: 'a>(&'a Option<T>); #[cfg(all( any(feature = "full", feature = "derive"), feature = "printing" ))] impl<'a, T> quote::ToTokens for TokensOrDefault<'a, T> where T: quote::ToTokens + Default, { fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) { match *self.0 { Some(ref t) => t.to_tokens(tokens), None => T::default().to_tokens(tokens), } } }