blob: 17396aac979c5bd605d84358b1810c9c5826ada5 [file] [log] [blame]
// 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 use in Rust procedural macros, but
//! contains some APIs that may be useful more generally.
//!
//! - **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.
//!
//! - **Parsing** — Parsing in Syn is built around [parser functions] with the
//! signature `fn(ParseStream) -> Result<T>`. Every syntax tree node defined
//! by Syn is individually parsable and may be used as a building block for
//! custom syntaxes, or you may dream up your own brand new syntax without
//! involving any of our syntax tree types.
//!
//! - **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
//! [parser functions]: parse/index.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 = "0.15"
//! quote = "0.6"
//!
//! [lib]
//! proc-macro = true
//! ```
//!
//! ```rust
//! #[macro_use]
//! extern crate quote;
//! #[macro_use]
//! extern crate syn;
//!
//! extern crate proc_macro;
//!
//! 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 = parse_macro_input!(input as DeriveInput);
//!
//! // Build the output, possibly using quasi-quotation
//! let expanded = quote! {
//! // ...
//! };
//!
//! // Hand the output tokens back to the compiler
//! TokenStream::from(expanded)
//! }
//! #
//! # 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+.
//! 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 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,
//! }
//! ```
//!
//! By tracking span information all the way through the expansion of a
//! procedural macro as shown in the `heapsize` 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
//!
//! The [`lazy-static`] example directory shows the implementation of a
//! `functionlike!(...)` procedural macro in which the input tokens are parsed
//! using Syn's parsing API.
//!
//! [`lazy-static`]: https://github.com/dtolnay/syn/tree/master/examples/lazy-static
//!
//! 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/0.15.21")]
#![cfg_attr(feature = "cargo-clippy", allow(renamed_and_removed_lints))]
#![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
// Ignored clippy lints.
#![cfg_attr(
feature = "cargo-clippy",
allow(
block_in_if_condition_stmt,
const_static_lifetime,
cyclomatic_complexity,
deprecated_cfg_attr,
doc_markdown,
eval_order_dependence,
large_enum_variant,
match_bool,
needless_pass_by_value,
never_loop,
redundant_closure,
redundant_field_names,
too_many_arguments,
trivially_copy_pass_by_ref,
)
)]
// Ignored clippy_pedantic lints.
#![cfg_attr(
feature = "cargo-clippy",
allow(
cast_possible_truncation,
cast_possible_wrap,
empty_enum,
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;
#[macro_use]
mod macros;
// Not public API.
#[cfg(feature = "parsing")]
#[doc(hidden)]
#[macro_use]
pub mod group;
#[macro_use]
pub mod token;
mod ident;
pub use ident::Ident;
#[cfg(any(feature = "full", feature = "derive"))]
mod attr;
#[cfg(any(feature = "full", feature = "derive"))]
pub use attr::{AttrStyle, Attribute, AttributeArgs, 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, ExprAsync, ExprBinary, ExprBlock, ExprBox,
ExprBreak, ExprCall, ExprCast, ExprClosure, ExprContinue, ExprField, ExprForLoop, ExprGroup,
ExprIf, ExprInPlace, ExprIndex, ExprLet, ExprLit, ExprLoop, ExprMacro, ExprMatch,
ExprMethodCall, ExprParen, ExprPath, ExprRange, ExprReference, ExprRepeat, ExprReturn,
ExprStruct, ExprTry, ExprTryBlock, ExprTuple, ExprType, ExprUnary, ExprUnsafe, ExprVerbatim,
ExprWhile, 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, ForeignItemMacro,
ForeignItemStatic, ForeignItemType, ForeignItemVerbatim, ImplItem, ImplItemConst,
ImplItemExistential, ImplItemMacro, ImplItemMethod, ImplItemType, ImplItemVerbatim, Item,
ItemConst, ItemEnum, ItemExistential, ItemExternCrate, ItemFn, ItemForeignMod, ItemImpl,
ItemMacro, ItemMacro2, ItemMod, ItemStatic, ItemStruct, ItemTrait, ItemTraitAlias, 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;
mod lifetime;
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(any(feature = "full", feature = "derive"))]
pub use path::{
AngleBracketedGenericArguments, Binding, Constraint, GenericArgument,
ParenthesizedGenericArguments, Path, PathArguments, PathSegment, QSelf,
};
#[cfg(feature = "parsing")]
pub mod buffer;
#[cfg(feature = "parsing")]
pub mod ext;
pub mod punctuated;
#[cfg(all(any(feature = "full", feature = "derive"), feature = "extra-traits"))]
mod tt;
// Not public API except the `parse_quote!` macro.
#[cfg(feature = "parsing")]
#[doc(hidden)]
pub mod parse_quote;
// Not public API except the `parse_macro_input!` macro.
#[cfg(all(
not(all(target_arch = "wasm32", target_os = "unknown")),
feature = "parsing",
feature = "proc-macro"
))]
#[doc(hidden)]
pub mod parse_macro_input;
#[cfg(all(feature = "parsing", feature = "printing"))]
pub mod spanned;
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::*;
// Not public API.
#[doc(hidden)]
pub mod export;
mod keyword;
#[cfg(feature = "parsing")]
mod lookahead;
#[cfg(feature = "parsing")]
pub mod parse;
mod span;
#[cfg(all(any(feature = "full", feature = "derive"), feature = "printing"))]
mod print;
#[cfg(feature = "parsing")]
mod thread;
////////////////////////////////////////////////////////////////////////////////
#[cfg(any(feature = "parsing", feature = "full", feature = "derive"))]
#[allow(non_camel_case_types)]
struct private;
////////////////////////////////////////////////////////////////////////////////
#[cfg(feature = "parsing")]
mod error;
#[cfg(feature = "parsing")]
use error::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
/// #[macro_use]
/// extern crate quote;
///
/// extern crate proc_macro;
/// extern crate syn;
///
/// 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 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: parse::Parse>(tokens: proc_macro::TokenStream) -> Result<T, Error> {
parse::Parser::parse(T::parse, tokens)
}
/// 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: parse::Parse>(tokens: proc_macro2::TokenStream) -> Result<T, Error> {
parse::Parser::parse2(T::parse, tokens)
}
/// 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;
/// #
/// use syn::Expr;
/// use syn::parse::Result;
///
/// 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: parse::Parse>(s: &str) -> Result<T, Error> {
parse::Parser::parse_str(T::parse, s)
}
// 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;
/// #
/// use std::error::Error;
/// use std::fs::File;
/// use std::io::Read;
///
/// fn run() -> Result<(), Box<Error>> {
/// 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, Error> {
// 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)
}