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diff --git a/syn/src/lib.rs b/syn/src/lib.rs new file mode 100644 index 0000000..0f71014 --- /dev/null +++ b/syn/src/lib.rs @@ -0,0 +1,947 @@ +//! 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`]. +//! +//! - **Derives** — Of particular interest to derive macros 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 user-defined trait. +//! +//! - **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 +//! +//! <br> +//! +//! # Example of a derive macro +//! +//! The canonical derive macro 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 = "1.0" +//! quote = "1.0" +//! +//! [lib] +//! proc-macro = true +//! ``` +//! +//! ``` +//! extern crate proc_macro; +//! +//! use proc_macro::TokenStream; +//! use quote::quote; +//! use syn::{parse_macro_input, 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) +//! } +//! ``` +//! +//! The [`heapsize`] example directory shows a complete working implementation +//! of a derive macro. It works on any Rust compiler 1.31+. 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 +//! +//! ``` +//! pub trait HeapSize { +//! /// Total number of bytes of heap memory owned by `self`. +//! fn heap_size_of_children(&self) -> usize; +//! } +//! ``` +//! +//! The derive macro allows users to write `#[derive(HeapSize)]` on data +//! structures in their program. +//! +//! ``` +//! # const IGNORE_TOKENS: &str = stringify! { +//! #[derive(HeapSize)] +//! # }; +//! struct Demo<'a, T: ?Sized> { +//! a: Box<T>, +//! b: u8, +//! c: &'a str, +//! d: String, +//! } +//! ``` +//! +//! <p><br></p> +//! +//! # 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`. +//! +//! ``` +//! # 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` +//! ``` +//! +//! <br> +//! +//! # 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(); +//! | ^^^ +//! ``` +//! +//! <br> +//! +//! # Testing +//! +//! When testing macros, we often care not just that the macro can be used +//! successfully but also that when the macro is provided with invalid input it +//! produces maximally helpful error messages. Consider using the [`trybuild`] +//! crate to write tests for errors that are emitted by your macro or errors +//! detected by the Rust compiler in the expanded code following misuse of the +//! macro. Such tests help avoid regressions from later refactors that +//! mistakenly make an error no longer trigger or be less helpful than it used +//! to be. +//! +//! [`trybuild`]: https://github.com/dtolnay/trybuild +//! +//! <br> +//! +//! # 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/ +//! +//! <br> +//! +//! # 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 derive macro, 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/1.0.12")] +#![deny(clippy::all, clippy::pedantic)] +// Ignored clippy lints. +#![allow( + clippy::block_in_if_condition_stmt, + clippy::cognitive_complexity, + clippy::doc_markdown, + clippy::eval_order_dependence, + clippy::inherent_to_string, + clippy::large_enum_variant, + clippy::needless_doctest_main, + clippy::needless_pass_by_value, + clippy::never_loop, + clippy::suspicious_op_assign_impl, + clippy::too_many_arguments, + clippy::trivially_copy_pass_by_ref +)] +// Ignored clippy_pedantic lints. +#![allow( + clippy::cast_possible_truncation, + clippy::empty_enum, + clippy::if_not_else, + clippy::items_after_statements, + clippy::missing_errors_doc, + clippy::module_name_repetitions, + clippy::must_use_candidate, + clippy::shadow_unrelated, + clippy::similar_names, + clippy::single_match_else, + clippy::too_many_lines, + clippy::unseparated_literal_suffix, + clippy::use_self, + clippy::used_underscore_binding +)] + +#[cfg(all( + not(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "wasi"))), + feature = "proc-macro" +))] +extern crate proc_macro; +extern crate proc_macro2; +extern crate unicode_xid; + +#[cfg(feature = "printing")] +extern crate quote; + +#[cfg(any(feature = "full", feature = "derive"))] +#[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 crate::ident::Ident; + +#[cfg(any(feature = "full", feature = "derive"))] +mod attr; +#[cfg(any(feature = "full", feature = "derive"))] +pub use crate::attr::{ + AttrStyle, Attribute, AttributeArgs, Meta, MetaList, MetaNameValue, NestedMeta, +}; + +#[cfg(any(feature = "full", feature = "derive"))] +mod bigint; + +#[cfg(any(feature = "full", feature = "derive"))] +mod data; +#[cfg(any(feature = "full", feature = "derive"))] +pub use crate::data::{ + Field, Fields, FieldsNamed, FieldsUnnamed, Variant, VisCrate, VisPublic, VisRestricted, + Visibility, +}; + +#[cfg(any(feature = "full", feature = "derive"))] +mod expr; +#[cfg(feature = "full")] +pub use crate::expr::{ + Arm, FieldValue, GenericMethodArgument, Label, MethodTurbofish, RangeLimits, +}; +#[cfg(any(feature = "full", feature = "derive"))] +pub use crate::expr::{ + Expr, ExprArray, ExprAssign, ExprAssignOp, ExprAsync, ExprAwait, ExprBinary, ExprBlock, + ExprBox, ExprBreak, ExprCall, ExprCast, ExprClosure, ExprContinue, ExprField, ExprForLoop, + ExprGroup, ExprIf, ExprIndex, ExprLet, ExprLit, ExprLoop, ExprMacro, ExprMatch, ExprMethodCall, + ExprParen, ExprPath, ExprRange, ExprReference, ExprRepeat, ExprReturn, ExprStruct, ExprTry, + ExprTryBlock, ExprTuple, ExprType, ExprUnary, ExprUnsafe, ExprWhile, ExprYield, Index, Member, +}; + +#[cfg(any(feature = "full", feature = "derive"))] +mod generics; +#[cfg(any(feature = "full", feature = "derive"))] +pub use crate::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 crate::generics::{ImplGenerics, Turbofish, TypeGenerics}; + +#[cfg(feature = "full")] +mod item; +#[cfg(feature = "full")] +pub use crate::item::{ + FnArg, ForeignItem, ForeignItemFn, ForeignItemMacro, ForeignItemStatic, ForeignItemType, + ImplItem, ImplItemConst, ImplItemMacro, ImplItemMethod, ImplItemType, Item, ItemConst, + ItemEnum, ItemExternCrate, ItemFn, ItemForeignMod, ItemImpl, ItemMacro, ItemMacro2, ItemMod, + ItemStatic, ItemStruct, ItemTrait, ItemTraitAlias, ItemType, ItemUnion, ItemUse, Receiver, + Signature, TraitItem, TraitItemConst, TraitItemMacro, TraitItemMethod, TraitItemType, UseGlob, + UseGroup, UseName, UsePath, UseRename, UseTree, +}; + +#[cfg(feature = "full")] +mod file; +#[cfg(feature = "full")] +pub use crate::file::File; + +mod lifetime; +pub use crate::lifetime::Lifetime; + +#[cfg(any(feature = "full", feature = "derive"))] +mod lit; +#[cfg(any(feature = "full", feature = "derive"))] +pub use crate::lit::{ + Lit, LitBool, LitByte, LitByteStr, LitChar, LitFloat, LitInt, LitStr, StrStyle, +}; + +#[cfg(any(feature = "full", feature = "derive"))] +mod mac; +#[cfg(any(feature = "full", feature = "derive"))] +pub use crate::mac::{Macro, MacroDelimiter}; + +#[cfg(any(feature = "full", feature = "derive"))] +mod derive; +#[cfg(feature = "derive")] +pub use crate::derive::{Data, DataEnum, DataStruct, DataUnion, DeriveInput}; + +#[cfg(any(feature = "full", feature = "derive"))] +mod op; +#[cfg(any(feature = "full", feature = "derive"))] +pub use crate::op::{BinOp, UnOp}; + +#[cfg(feature = "full")] +mod stmt; +#[cfg(feature = "full")] +pub use crate::stmt::{Block, Local, Stmt}; + +#[cfg(any(feature = "full", feature = "derive"))] +mod ty; +#[cfg(any(feature = "full", feature = "derive"))] +pub use crate::ty::{ + Abi, BareFnArg, ReturnType, Type, TypeArray, TypeBareFn, TypeGroup, TypeImplTrait, TypeInfer, + TypeMacro, TypeNever, TypeParen, TypePath, TypePtr, TypeReference, TypeSlice, TypeTraitObject, + TypeTuple, Variadic, +}; + +#[cfg(feature = "full")] +mod pat; +#[cfg(feature = "full")] +pub use crate::pat::{ + FieldPat, Pat, PatBox, PatIdent, PatLit, PatMacro, PatOr, PatPath, PatRange, PatReference, + PatRest, PatSlice, PatStruct, PatTuple, PatTupleStruct, PatType, PatWild, +}; + +#[cfg(any(feature = "full", feature = "derive"))] +mod path; +#[cfg(any(feature = "full", feature = "derive"))] +pub use crate::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", any(target_os = "unknown", target_os = "wasi"))), + 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`]: visit::Visit + /// + /// ``` + /// # use syn::{Attribute, BinOp, Expr, ExprBinary}; + /// # + /// pub trait Visit<'ast> { + /// /* ... */ + /// + /// fn visit_expr_binary(&mut self, node: &'ast ExprBinary) { + /// visit_expr_binary(self, node); + /// } + /// + /// /* ... */ + /// # 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); + /// } + /// + /// pub fn visit_expr_binary<'ast, V>(v: &mut V, node: &'ast ExprBinary) + /// where + /// V: Visit<'ast> + ?Sized, + /// { + /// for attr in &node.attrs { + /// v.visit_attribute(attr); + /// } + /// v.visit_expr(&*node.left); + /// v.visit_bin_op(&node.op); + /// v.visit_expr(&*node.right); + /// } + /// + /// /* ... */ + /// ``` + /// + /// *This module is available if Syn is built with the `"visit"` feature.* + /// + /// <br> + /// + /// # Example + /// + /// This visitor will print the name of every freestanding function in the + /// syntax tree, including nested functions. + /// + /// ``` + /// // [dependencies] + /// // quote = "1.0" + /// // syn = { version = "1.0", features = ["full", "visit"] } + /// + /// use quote::quote; + /// use syn::visit::{self, Visit}; + /// use syn::{File, ItemFn}; + /// + /// struct FnVisitor; + /// + /// impl<'ast> Visit<'ast> for FnVisitor { + /// fn visit_item_fn(&mut self, node: &'ast ItemFn) { + /// println!("Function with name={}", node.sig.ident); + /// + /// // Delegate to the default impl to visit any nested functions. + /// visit::visit_item_fn(self, node); + /// } + /// } + /// + /// fn main() { + /// let code = quote! { + /// pub fn f() { + /// fn g() {} + /// } + /// }; + /// + /// let syntax_tree: File = syn::parse2(code).unwrap(); + /// FnVisitor.visit_file(&syntax_tree); + /// } + /// ``` + /// + /// The `'ast` lifetime on the input references means that the syntax tree + /// outlives the complete recursive visit call, so the visitor is allowed to + /// hold on to references into the syntax tree. + /// + /// ``` + /// use quote::quote; + /// use syn::visit::{self, Visit}; + /// use syn::{File, ItemFn}; + /// + /// struct FnVisitor<'ast> { + /// functions: Vec<&'ast ItemFn>, + /// } + /// + /// impl<'ast> Visit<'ast> for FnVisitor<'ast> { + /// fn visit_item_fn(&mut self, node: &'ast ItemFn) { + /// self.functions.push(node); + /// visit::visit_item_fn(self, node); + /// } + /// } + /// + /// fn main() { + /// let code = quote! { + /// pub fn f() { + /// fn g() {} + /// } + /// }; + /// + /// let syntax_tree: File = syn::parse2(code).unwrap(); + /// let mut visitor = FnVisitor { functions: Vec::new() }; + /// visitor.visit_file(&syntax_tree); + /// for f in visitor.functions { + /// println!("Function with name={}", f.sig.ident); + /// } + /// } + /// ``` + #[cfg(feature = "visit")] + #[rustfmt::skip] + 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`]: visit_mut::VisitMut + /// + /// ``` + /// # use syn::{Attribute, BinOp, Expr, ExprBinary}; + /// # + /// pub trait VisitMut { + /// /* ... */ + /// + /// fn visit_expr_binary_mut(&mut self, node: &mut ExprBinary) { + /// visit_expr_binary_mut(self, node); + /// } + /// + /// /* ... */ + /// # 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); + /// } + /// + /// pub fn visit_expr_binary_mut<V>(v: &mut V, node: &mut ExprBinary) + /// where + /// V: VisitMut + ?Sized, + /// { + /// for attr in &mut node.attrs { + /// v.visit_attribute_mut(attr); + /// } + /// v.visit_expr_mut(&mut *node.left); + /// v.visit_bin_op_mut(&mut node.op); + /// v.visit_expr_mut(&mut *node.right); + /// } + /// + /// /* ... */ + /// ``` + /// + /// *This module is available if Syn is built with the `"visit-mut"` + /// feature.* + /// + /// <br> + /// + /// # Example + /// + /// This mut visitor replace occurrences of u256 suffixed integer literals + /// like `999u256` with a macro invocation `bigint::u256!(999)`. + /// + /// ``` + /// // [dependencies] + /// // quote = "1.0" + /// // syn = { version = "1.0", features = ["full", "visit-mut"] } + /// + /// use quote::quote; + /// use syn::visit_mut::{self, VisitMut}; + /// use syn::{parse_quote, Expr, File, Lit, LitInt}; + /// + /// struct BigintReplace; + /// + /// impl VisitMut for BigintReplace { + /// fn visit_expr_mut(&mut self, node: &mut Expr) { + /// if let Expr::Lit(expr) = &node { + /// if let Lit::Int(int) = &expr.lit { + /// if int.suffix() == "u256" { + /// let digits = int.base10_digits(); + /// let unsuffixed: LitInt = syn::parse_str(digits).unwrap(); + /// *node = parse_quote!(bigint::u256!(#unsuffixed)); + /// return; + /// } + /// } + /// } + /// + /// // Delegate to the default impl to visit nested expressions. + /// visit_mut::visit_expr_mut(self, node); + /// } + /// } + /// + /// fn main() { + /// let code = quote! { + /// fn main() { + /// let _ = 999u256; + /// } + /// }; + /// + /// let mut syntax_tree: File = syn::parse2(code).unwrap(); + /// BigintReplace.visit_file_mut(&mut syntax_tree); + /// println!("{}", quote!(#syntax_tree)); + /// } + /// ``` + #[cfg(feature = "visit-mut")] + #[rustfmt::skip] + 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`]: fold::Fold + /// + /// ``` + /// # use syn::{Attribute, BinOp, Expr, ExprBinary}; + /// # + /// pub trait Fold { + /// /* ... */ + /// + /// fn fold_expr_binary(&mut self, node: ExprBinary) -> ExprBinary { + /// fold_expr_binary(self, node) + /// } + /// + /// /* ... */ + /// # 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; + /// } + /// + /// pub fn fold_expr_binary<V>(v: &mut V, node: ExprBinary) -> ExprBinary + /// where + /// V: Fold + ?Sized, + /// { + /// ExprBinary { + /// attrs: node + /// .attrs + /// .into_iter() + /// .map(|attr| v.fold_attribute(attr)) + /// .collect(), + /// left: Box::new(v.fold_expr(*node.left)), + /// op: v.fold_bin_op(node.op), + /// right: Box::new(v.fold_expr(*node.right)), + /// } + /// } + /// + /// /* ... */ + /// ``` + /// + /// *This module is available if Syn is built with the `"fold"` feature.* + /// + /// <br> + /// + /// # Example + /// + /// This fold inserts parentheses to fully parenthesizes any expression. + /// + /// ``` + /// // [dependencies] + /// // quote = "1.0" + /// // syn = { version = "1.0", features = ["fold", "full"] } + /// + /// use quote::quote; + /// use syn::fold::{fold_expr, Fold}; + /// use syn::{token, Expr, ExprParen}; + /// + /// struct ParenthesizeEveryExpr; + /// + /// impl Fold for ParenthesizeEveryExpr { + /// fn fold_expr(&mut self, expr: Expr) -> Expr { + /// Expr::Paren(ExprParen { + /// attrs: Vec::new(), + /// expr: Box::new(fold_expr(self, expr)), + /// paren_token: token::Paren::default(), + /// }) + /// } + /// } + /// + /// fn main() { + /// let code = quote! { a() + b(1) * c.d }; + /// let expr: Expr = syn::parse2(code).unwrap(); + /// let parenthesized = ParenthesizeEveryExpr.fold_expr(expr); + /// println!("{}", quote!(#parenthesized)); + /// + /// // Output: (((a)()) + (((b)((1))) * ((c).d))) + /// } + /// ``` + #[cfg(feature = "fold")] + #[rustfmt::skip] + pub mod fold; + + #[cfg(any(feature = "full", feature = "derive"))] + #[path = "../gen_helper.rs"] + mod helper; +} +pub use crate::gen::*; + +// Not public API. +#[doc(hidden)] +pub mod export; + +mod custom_keyword; +mod custom_punctuation; +mod sealed; + +#[cfg(feature = "parsing")] +mod lookahead; + +#[cfg(feature = "parsing")] +pub mod parse; + +mod span; + +#[cfg(all(any(feature = "full", feature = "derive"), feature = "printing"))] +mod print; + +mod thread; + +//////////////////////////////////////////////////////////////////////////////// + +#[allow(dead_code, non_camel_case_types)] +struct private; + +// https://github.com/rust-lang/rust/issues/62830 +#[cfg(feature = "parsing")] +mod rustdoc_workaround { + pub use crate::parse::{self as parse_module}; +} + +//////////////////////////////////////////////////////////////////////////////// + +mod error; +pub use crate::error::{Error, Result}; + +/// 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`]: parse2 +/// +/// *This function is available if Syn is built with both the `"parsing"` and +/// `"proc-macro"` features.* +/// +/// # Examples +/// +/// ``` +/// extern crate proc_macro; +/// +/// use proc_macro::TokenStream; +/// use quote::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() +/// } +/// ``` +#[cfg(all( + not(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "wasi"))), + feature = "parsing", + feature = "proc-macro" +))] +pub fn parse<T: parse::Parse>(tokens: proc_macro::TokenStream) -> Result<T> { + 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 +/// body tokens of a [`Macro`] node. When in a procedural macro parsing the +/// `proc_macro::TokenStream` provided by the compiler, use [`syn::parse`] +/// instead. +/// +/// [`syn::parse`]: parse() +/// +/// *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> { + 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 +/// +/// ``` +/// use syn::{Expr, Result}; +/// +/// fn run() -> Result<()> { +/// let code = "assert_eq!(u8::max_value(), 255)"; +/// let expr = syn::parse_str::<Expr>(code)?; +/// println!("{:#?}", expr); +/// Ok(()) +/// } +/// # +/// # run().unwrap(); +/// ``` +#[cfg(feature = "parsing")] +pub fn parse_str<T: parse::Parse>(s: &str) -> Result<T> { + 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 +/// +/// ```no_run +/// 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(()) +/// } +/// # +/// # run().unwrap(); +/// ``` +#[cfg(all(feature = "parsing", feature = "full"))] +pub fn parse_file(mut content: &str) -> Result<File> { + // Strip the BOM if it is present + const BOM: &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) +} |