Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 1013 insertions, 0 deletions

diff --git a/rust/syn/lib.rs b/rust/syn/lib.rs
new file mode 100644
index 000000000..b0006fd30
--- /dev/null
+++ b/rust/syn/lib.rs
@@ -0,0 +1,1013 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! [![github]](https://github.com/dtolnay/syn) [![crates-io]](https://crates.io/crates/syn) [![docs-rs]](crate)
+//!
+//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
+//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
+//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
+//!
+//! <br>
+//!
+//! 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`]: File
+//! [`syn::Item`]: Item
+//! [`syn::Expr`]: Expr
+//! [`syn::Type`]: Type
+//! [`syn::DeriveInput`]: DeriveInput
+//! [parser functions]: mod@parse
+//!
+//! <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`]: proc_macro::TokenStream
+//!
+//! ```toml
+//! [dependencies]
+//! syn = "2.0"
+//! 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. 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/2.0.106")]
+#![cfg_attr(docsrs, feature(doc_cfg))]
+#![deny(unsafe_op_in_unsafe_fn)]
+#![allow(non_camel_case_types)]
+#![cfg_attr(not(check_cfg), allow(unexpected_cfgs))]
+#![allow(
+    clippy::bool_to_int_with_if,
+    clippy::cast_lossless,
+    clippy::cast_possible_truncation,
+    clippy::cast_possible_wrap,
+    clippy::cast_ptr_alignment,
+    clippy::default_trait_access,
+    clippy::derivable_impls,
+    clippy::diverging_sub_expression,
+    clippy::doc_markdown,
+    clippy::elidable_lifetime_names,
+    clippy::enum_glob_use,
+    clippy::expl_impl_clone_on_copy,
+    clippy::explicit_auto_deref,
+    clippy::fn_params_excessive_bools,
+    clippy::if_not_else,
+    clippy::inherent_to_string,
+    clippy::into_iter_without_iter,
+    clippy::items_after_statements,
+    clippy::large_enum_variant,
+    clippy::let_underscore_untyped, // https://github.com/rust-lang/rust-clippy/issues/10410
+    clippy::manual_assert,
+    clippy::manual_let_else,
+    clippy::manual_map,
+    clippy::match_like_matches_macro,
+    clippy::match_same_arms,
+    clippy::match_wildcard_for_single_variants, // clippy bug: https://github.com/rust-lang/rust-clippy/issues/6984
+    clippy::missing_errors_doc,
+    clippy::missing_panics_doc,
+    clippy::module_name_repetitions,
+    clippy::must_use_candidate,
+    clippy::needless_doctest_main,
+    clippy::needless_lifetimes,
+    clippy::needless_pass_by_value,
+    clippy::needless_update,
+    clippy::never_loop,
+    clippy::range_plus_one,
+    clippy::redundant_else,
+    clippy::ref_option,
+    clippy::return_self_not_must_use,
+    clippy::similar_names,
+    clippy::single_match_else,
+    clippy::struct_excessive_bools,
+    clippy::too_many_arguments,
+    clippy::too_many_lines,
+    clippy::trivially_copy_pass_by_ref,
+    clippy::unconditional_recursion, // https://github.com/rust-lang/rust-clippy/issues/12133
+    clippy::uninhabited_references,
+    clippy::uninlined_format_args,
+    clippy::unnecessary_box_returns,
+    clippy::unnecessary_unwrap,
+    clippy::used_underscore_binding,
+    clippy::wildcard_imports,
+)]
+#![allow(unknown_lints, mismatched_lifetime_syntaxes)]
+
+extern crate self as syn;
+
+#[cfg(feature = "proc-macro")]
+extern crate proc_macro;
+
+#[macro_use]
+mod macros;
+
+#[cfg(feature = "parsing")]
+#[macro_use]
+mod group;
+
+#[macro_use]
+pub mod token;
+
+#[cfg(any(feature = "full", feature = "derive"))]
+mod attr;
+#[cfg(any(feature = "full", feature = "derive"))]
+#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+pub use crate::attr::{AttrStyle, Attribute, Meta, MetaList, MetaNameValue};
+
+mod bigint;
+
+#[cfg(feature = "parsing")]
+#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+pub mod buffer;
+
+#[cfg(any(
+    all(feature = "parsing", feature = "full"),
+    all(feature = "printing", any(feature = "full", feature = "derive")),
+))]
+mod classify;
+
+mod custom_keyword;
+
+mod custom_punctuation;
+
+#[cfg(any(feature = "full", feature = "derive"))]
+mod data;
+#[cfg(any(feature = "full", feature = "derive"))]
+#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+pub use crate::data::{Field, Fields, FieldsNamed, FieldsUnnamed, Variant};
+
+#[cfg(any(feature = "full", feature = "derive"))]
+mod derive;
+#[cfg(feature = "derive")]
+#[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
+pub use crate::derive::{Data, DataEnum, DataStruct, DataUnion, DeriveInput};
+
+mod drops;
+
+mod error;
+pub use crate::error::{Error, Result};
+
+#[cfg(any(feature = "full", feature = "derive"))]
+mod expr;
+#[cfg(feature = "full")]
+#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+pub use crate::expr::{Arm, Label, PointerMutability, RangeLimits};
+#[cfg(any(feature = "full", feature = "derive"))]
+#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+pub use crate::expr::{
+    Expr, ExprBinary, ExprCall, ExprCast, ExprField, ExprIndex, ExprLit, ExprMacro, ExprMethodCall,
+    ExprParen, ExprPath, ExprReference, ExprStruct, ExprUnary, FieldValue, Index, Member,
+};
+#[cfg(any(feature = "full", feature = "derive"))]
+#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+pub use crate::expr::{
+    ExprArray, ExprAssign, ExprAsync, ExprAwait, ExprBlock, ExprBreak, ExprClosure, ExprConst,
+    ExprContinue, ExprForLoop, ExprGroup, ExprIf, ExprInfer, ExprLet, ExprLoop, ExprMatch,
+    ExprRange, ExprRawAddr, ExprRepeat, ExprReturn, ExprTry, ExprTryBlock, ExprTuple, ExprUnsafe,
+    ExprWhile, ExprYield,
+};
+
+#[cfg(feature = "parsing")]
+#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+pub mod ext;
+
+#[cfg(feature = "full")]
+mod file;
+#[cfg(feature = "full")]
+#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+pub use crate::file::File;
+
+#[cfg(all(any(feature = "full", feature = "derive"), feature = "printing"))]
+mod fixup;
+
+#[cfg(any(feature = "full", feature = "derive"))]
+mod generics;
+#[cfg(any(feature = "full", feature = "derive"))]
+#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+pub use crate::generics::{
+    BoundLifetimes, ConstParam, GenericParam, Generics, LifetimeParam, PredicateLifetime,
+    PredicateType, TraitBound, TraitBoundModifier, TypeParam, TypeParamBound, WhereClause,
+    WherePredicate,
+};
+#[cfg(feature = "full")]
+#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+pub use crate::generics::{CapturedParam, PreciseCapture};
+#[cfg(all(any(feature = "full", feature = "derive"), feature = "printing"))]
+#[cfg_attr(
+    docsrs,
+    doc(cfg(all(any(feature = "full", feature = "derive"), feature = "printing")))
+)]
+pub use crate::generics::{ImplGenerics, Turbofish, TypeGenerics};
+
+mod ident;
+#[doc(inline)]
+pub use crate::ident::Ident;
+
+#[cfg(feature = "full")]
+mod item;
+#[cfg(feature = "full")]
+#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+pub use crate::item::{
+    FnArg, ForeignItem, ForeignItemFn, ForeignItemMacro, ForeignItemStatic, ForeignItemType,
+    ImplItem, ImplItemConst, ImplItemFn, ImplItemMacro, ImplItemType, ImplRestriction, Item,
+    ItemConst, ItemEnum, ItemExternCrate, ItemFn, ItemForeignMod, ItemImpl, ItemMacro, ItemMod,
+    ItemStatic, ItemStruct, ItemTrait, ItemTraitAlias, ItemType, ItemUnion, ItemUse, Receiver,
+    Signature, StaticMutability, TraitItem, TraitItemConst, TraitItemFn, TraitItemMacro,
+    TraitItemType, UseGlob, UseGroup, UseName, UsePath, UseRename, UseTree, Variadic,
+};
+
+mod lifetime;
+#[doc(inline)]
+pub use crate::lifetime::Lifetime;
+
+mod lit;
+#[doc(hidden)] // https://github.com/dtolnay/syn/issues/1566
+pub use crate::lit::StrStyle;
+#[doc(inline)]
+pub use crate::lit::{
+    Lit, LitBool, LitByte, LitByteStr, LitCStr, LitChar, LitFloat, LitInt, LitStr,
+};
+
+#[cfg(feature = "parsing")]
+mod lookahead;
+
+#[cfg(any(feature = "full", feature = "derive"))]
+mod mac;
+#[cfg(any(feature = "full", feature = "derive"))]
+#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+pub use crate::mac::{Macro, MacroDelimiter};
+
+#[cfg(all(feature = "parsing", any(feature = "full", feature = "derive")))]
+#[cfg_attr(
+    docsrs,
+    doc(cfg(all(feature = "parsing", any(feature = "full", feature = "derive"))))
+)]
+pub mod meta;
+
+#[cfg(any(feature = "full", feature = "derive"))]
+mod op;
+#[cfg(any(feature = "full", feature = "derive"))]
+#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+pub use crate::op::{BinOp, UnOp};
+
+#[cfg(feature = "parsing")]
+#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+pub mod parse;
+
+#[cfg(all(feature = "parsing", feature = "proc-macro"))]
+mod parse_macro_input;
+
+#[cfg(all(feature = "parsing", feature = "printing"))]
+mod parse_quote;
+
+#[cfg(feature = "full")]
+mod pat;
+#[cfg(feature = "full")]
+#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+pub use crate::pat::{
+    FieldPat, Pat, PatConst, PatIdent, PatLit, PatMacro, PatOr, PatParen, PatPath, PatRange,
+    PatReference, PatRest, PatSlice, PatStruct, PatTuple, PatTupleStruct, PatType, PatWild,
+};
+
+#[cfg(any(feature = "full", feature = "derive"))]
+mod path;
+#[cfg(any(feature = "full", feature = "derive"))]
+#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+pub use crate::path::{
+    AngleBracketedGenericArguments, AssocConst, AssocType, Constraint, GenericArgument,
+    ParenthesizedGenericArguments, Path, PathArguments, PathSegment, QSelf,
+};
+
+#[cfg(all(
+    any(feature = "full", feature = "derive"),
+    any(feature = "parsing", feature = "printing")
+))]
+mod precedence;
+
+#[cfg(all(any(feature = "full", feature = "derive"), feature = "printing"))]
+mod print;
+
+pub mod punctuated;
+
+#[cfg(any(feature = "full", feature = "derive"))]
+mod restriction;
+#[cfg(any(feature = "full", feature = "derive"))]
+#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+pub use crate::restriction::{FieldMutability, VisRestricted, Visibility};
+
+mod sealed;
+
+#[cfg(all(feature = "parsing", feature = "derive", not(feature = "full")))]
+mod scan_expr;
+
+mod span;
+
+#[cfg(all(feature = "parsing", feature = "printing"))]
+#[cfg_attr(docsrs, doc(cfg(all(feature = "parsing", feature = "printing"))))]
+pub mod spanned;
+
+#[cfg(feature = "full")]
+mod stmt;
+#[cfg(feature = "full")]
+#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+pub use crate::stmt::{Block, Local, LocalInit, Stmt, StmtMacro};
+
+mod thread;
+
+#[cfg(all(any(feature = "full", feature = "derive"), feature = "extra-traits"))]
+mod tt;
+
+#[cfg(any(feature = "full", feature = "derive"))]
+mod ty;
+#[cfg(any(feature = "full", feature = "derive"))]
+#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+pub use crate::ty::{
+    Abi, BareFnArg, BareVariadic, ReturnType, Type, TypeArray, TypeBareFn, TypeGroup,
+    TypeImplTrait, TypeInfer, TypeMacro, TypeNever, TypeParen, TypePath, TypePtr, TypeReference,
+    TypeSlice, TypeTraitObject, TypeTuple,
+};
+
+#[cfg(all(any(feature = "full", feature = "derive"), feature = "parsing"))]
+mod verbatim;
+
+#[cfg(all(feature = "parsing", feature = "full"))]
+mod whitespace;
+
+#[rustfmt::skip] // https://github.com/rust-lang/rustfmt/issues/6176
+mod gen {
+    /// 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)),
+    ///     }
+    /// }
+    ///
+    /// /* ... */
+    /// ```
+    ///
+    /// <br>
+    ///
+    /// # Example
+    ///
+    /// This fold inserts parentheses to fully parenthesizes any expression.
+    ///
+    /// ```
+    /// // [dependencies]
+    /// // quote = "1.0"
+    /// // syn = { version = "2.0", 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")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "fold")))]
+    #[rustfmt::skip]
+    pub mod fold;
+
+    /// 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);
+    /// }
+    ///
+    /// /* ... */
+    /// ```
+    ///
+    /// <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 = "2.0", 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")]
+    #[cfg_attr(docsrs, doc(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);
+    /// }
+    ///
+    /// /* ... */
+    /// ```
+    ///
+    /// <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 = "2.0", 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")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "visit-mut")))]
+    #[rustfmt::skip]
+    pub mod visit_mut;
+
+    #[cfg(feature = "clone-impls")]
+    #[rustfmt::skip]
+    mod clone;
+
+    #[cfg(feature = "extra-traits")]
+    #[rustfmt::skip]
+    mod debug;
+
+    #[cfg(feature = "extra-traits")]
+    #[rustfmt::skip]
+    mod eq;
+
+    #[cfg(feature = "extra-traits")]
+    #[rustfmt::skip]
+    mod hash;
+}
+
+#[cfg(feature = "fold")]
+#[cfg_attr(docsrs, doc(cfg(feature = "fold")))]
+pub use crate::gen::fold;
+
+#[cfg(feature = "visit")]
+#[cfg_attr(docsrs, doc(cfg(feature = "visit")))]
+pub use crate::gen::visit;
+
+#[cfg(feature = "visit-mut")]
+#[cfg_attr(docsrs, doc(cfg(feature = "visit-mut")))]
+pub use crate::gen::visit_mut;
+
+// Not public API.
+#[doc(hidden)]
+#[path = "export.rs"]
+pub mod __private;
+
+/// 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 enforces that the input is fully parsed. If there are any
+/// unparsed tokens at the end of the stream, an error is returned.
+#[cfg(all(feature = "parsing", feature = "proc-macro"))]
+#[cfg_attr(docsrs, doc(cfg(all(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 enforces that the input is fully parsed. If there are any
+/// unparsed tokens at the end of the stream, an error is returned.
+#[cfg(feature = "parsing")]
+#[cfg_attr(docsrs, doc(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 enforces that the input is fully parsed. If there are any
+/// unparsed tokens at the end of the stream, an error is returned.
+///
+/// # 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")]
+#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+pub fn parse_str<T: parse::Parse>(s: &str) -> Result<T> {
+    parse::Parser::parse_str(T::parse, s)
+}
+
+/// 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`.
+///
+/// # Examples
+///
+/// ```no_run
+/// use std::error::Error;
+/// use std::fs;
+/// use std::io::Read;
+///
+/// fn run() -> Result<(), Box<dyn Error>> {
+///     let content = fs::read_to_string("path/to/code.rs")?;
+///     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"))]
+#[cfg_attr(docsrs, doc(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("#!") {
+        let rest = whitespace::skip(&content[2..]);
+        if !rest.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)
+}