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, 1098 insertions, 0 deletions

diff --git a/rust/syn/token.rs b/rust/syn/token.rs
new file mode 100644
index 000000000..18345cc58
--- /dev/null
+++ b/rust/syn/token.rs
@@ -0,0 +1,1098 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! Tokens representing Rust punctuation, keywords, and delimiters.
+//!
+//! The type names in this module can be difficult to keep straight, so we
+//! prefer to use the [`Token!`] macro instead. This is a type-macro that
+//! expands to the token type of the given token.
+//!
+//! [`Token!`]: crate::Token
+//!
+//! # Example
+//!
+//! The [`ItemStatic`] syntax tree node is defined like this.
+//!
+//! [`ItemStatic`]: crate::ItemStatic
+//!
+//! ```
+//! # use syn::{Attribute, Expr, Ident, Token, Type, Visibility};
+//! #
+//! pub struct ItemStatic {
+//!     pub attrs: Vec<Attribute>,
+//!     pub vis: Visibility,
+//!     pub static_token: Token![static],
+//!     pub mutability: Option<Token![mut]>,
+//!     pub ident: Ident,
+//!     pub colon_token: Token![:],
+//!     pub ty: Box<Type>,
+//!     pub eq_token: Token![=],
+//!     pub expr: Box<Expr>,
+//!     pub semi_token: Token![;],
+//! }
+//! ```
+//!
+//! # Parsing
+//!
+//! Keywords and punctuation can be parsed through the [`ParseStream::parse`]
+//! method. Delimiter tokens are parsed using the [`parenthesized!`],
+//! [`bracketed!`] and [`braced!`] macros.
+//!
+//! [`ParseStream::parse`]: crate::parse::ParseBuffer::parse()
+//! [`parenthesized!`]: crate::parenthesized!
+//! [`bracketed!`]: crate::bracketed!
+//! [`braced!`]: crate::braced!
+//!
+//! ```
+//! use syn::{Attribute, Result};
+//! use syn::parse::{Parse, ParseStream};
+//! #
+//! # enum ItemStatic {}
+//!
+//! // Parse the ItemStatic struct shown above.
+//! impl Parse for ItemStatic {
+//!     fn parse(input: ParseStream) -> Result<Self> {
+//!         # use syn::ItemStatic;
+//!         # fn parse(input: ParseStream) -> Result<ItemStatic> {
+//!         Ok(ItemStatic {
+//!             attrs: input.call(Attribute::parse_outer)?,
+//!             vis: input.parse()?,
+//!             static_token: input.parse()?,
+//!             mutability: input.parse()?,
+//!             ident: input.parse()?,
+//!             colon_token: input.parse()?,
+//!             ty: input.parse()?,
+//!             eq_token: input.parse()?,
+//!             expr: input.parse()?,
+//!             semi_token: input.parse()?,
+//!         })
+//!         # }
+//!         # unimplemented!()
+//!     }
+//! }
+//! ```
+//!
+//! # Other operations
+//!
+//! Every keyword and punctuation token supports the following operations.
+//!
+//! - [Peeking] — `input.peek(Token![...])`
+//!
+//! - [Parsing] — `input.parse::<Token![...]>()?`
+//!
+//! - [Printing] — `quote!( ... #the_token ... )`
+//!
+//! - Construction from a [`Span`] — `let the_token = Token![...](sp)`
+//!
+//! - Field access to its span — `let sp = the_token.span`
+//!
+//! [Peeking]: crate::parse::ParseBuffer::peek()
+//! [Parsing]: crate::parse::ParseBuffer::parse()
+//! [Printing]: https://docs.rs/quote/1.0/quote/trait.ToTokens.html
+//! [`Span`]: https://docs.rs/proc-macro2/1.0/proc_macro2/struct.Span.html
+
+#[cfg(feature = "parsing")]
+pub(crate) use self::private::CustomToken;
+use self::private::WithSpan;
+#[cfg(feature = "parsing")]
+use crate::buffer::Cursor;
+#[cfg(feature = "parsing")]
+use crate::error::Result;
+#[cfg(feature = "parsing")]
+use crate::lifetime::Lifetime;
+#[cfg(feature = "parsing")]
+use crate::parse::{Parse, ParseStream};
+use crate::span::IntoSpans;
+use proc_macro2::extra::DelimSpan;
+use proc_macro2::Span;
+#[cfg(feature = "printing")]
+use proc_macro2::TokenStream;
+#[cfg(any(feature = "parsing", feature = "printing"))]
+use proc_macro2::{Delimiter, Ident};
+#[cfg(feature = "parsing")]
+use proc_macro2::{Literal, Punct, TokenTree};
+#[cfg(feature = "printing")]
+use quote::{ToTokens, TokenStreamExt};
+#[cfg(feature = "extra-traits")]
+use std::cmp;
+#[cfg(feature = "extra-traits")]
+use std::fmt::{self, Debug};
+#[cfg(feature = "extra-traits")]
+use std::hash::{Hash, Hasher};
+use std::ops::{Deref, DerefMut};
+
+/// Marker trait for types that represent single tokens.
+///
+/// This trait is sealed and cannot be implemented for types outside of Syn.
+#[cfg(feature = "parsing")]
+pub trait Token: private::Sealed {
+    // Not public API.
+    #[doc(hidden)]
+    fn peek(cursor: Cursor) -> bool;
+
+    // Not public API.
+    #[doc(hidden)]
+    fn display() -> &'static str;
+}
+
+pub(crate) mod private {
+    #[cfg(feature = "parsing")]
+    use crate::buffer::Cursor;
+    use proc_macro2::Span;
+
+    #[cfg(feature = "parsing")]
+    pub trait Sealed {}
+
+    /// Support writing `token.span` rather than `token.spans[0]` on tokens that
+    /// hold a single span.
+    #[repr(transparent)]
+    #[allow(unknown_lints, repr_transparent_external_private_fields)] // False positive: https://github.com/rust-lang/rust/issues/78586#issuecomment-1722680482
+    pub struct WithSpan {
+        pub span: Span,
+    }
+
+    // Not public API.
+    #[doc(hidden)]
+    #[cfg(feature = "parsing")]
+    pub trait CustomToken {
+        fn peek(cursor: Cursor) -> bool;
+        fn display() -> &'static str;
+    }
+}
+
+#[cfg(feature = "parsing")]
+impl private::Sealed for Ident {}
+
+macro_rules! impl_low_level_token {
+    ($display:literal $($path:ident)::+ $get:ident) => {
+        #[cfg(feature = "parsing")]
+        impl Token for $($path)::+ {
+            fn peek(cursor: Cursor) -> bool {
+                cursor.$get().is_some()
+            }
+
+            fn display() -> &'static str {
+                $display
+            }
+        }
+
+        #[cfg(feature = "parsing")]
+        impl private::Sealed for $($path)::+ {}
+    };
+}
+
+impl_low_level_token!("punctuation token" Punct punct);
+impl_low_level_token!("literal" Literal literal);
+impl_low_level_token!("token" TokenTree token_tree);
+impl_low_level_token!("group token" proc_macro2::Group any_group);
+impl_low_level_token!("lifetime" Lifetime lifetime);
+
+#[cfg(feature = "parsing")]
+impl<T: CustomToken> private::Sealed for T {}
+
+#[cfg(feature = "parsing")]
+impl<T: CustomToken> Token for T {
+    fn peek(cursor: Cursor) -> bool {
+        <Self as CustomToken>::peek(cursor)
+    }
+
+    fn display() -> &'static str {
+        <Self as CustomToken>::display()
+    }
+}
+
+macro_rules! define_keywords {
+    ($($token:literal pub struct $name:ident)*) => {
+        $(
+            #[doc = concat!('`', $token, '`')]
+            ///
+            /// Don't try to remember the name of this type &mdash; use the
+            /// [`Token!`] macro instead.
+            ///
+            /// [`Token!`]: crate::token
+            pub struct $name {
+                pub span: Span,
+            }
+
+            #[doc(hidden)]
+            #[allow(non_snake_case)]
+            pub fn $name<S: IntoSpans<Span>>(span: S) -> $name {
+                $name {
+                    span: span.into_spans(),
+                }
+            }
+
+            impl std::default::Default for $name {
+                fn default() -> Self {
+                    $name {
+                        span: Span::call_site(),
+                    }
+                }
+            }
+
+            #[cfg(feature = "clone-impls")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "clone-impls")))]
+            impl Copy for $name {}
+
+            #[cfg(feature = "clone-impls")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "clone-impls")))]
+            impl Clone for $name {
+                fn clone(&self) -> Self {
+                    *self
+                }
+            }
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl Debug for $name {
+                fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                    f.write_str(stringify!($name))
+                }
+            }
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl cmp::Eq for $name {}
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl PartialEq for $name {
+                fn eq(&self, _other: &$name) -> bool {
+                    true
+                }
+            }
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl Hash for $name {
+                fn hash<H: Hasher>(&self, _state: &mut H) {}
+            }
+
+            #[cfg(feature = "printing")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+            impl ToTokens for $name {
+                fn to_tokens(&self, tokens: &mut TokenStream) {
+                    printing::keyword($token, self.span, tokens);
+                }
+            }
+
+            #[cfg(feature = "parsing")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+            impl Parse for $name {
+                fn parse(input: ParseStream) -> Result<Self> {
+                    Ok($name {
+                        span: parsing::keyword(input, $token)?,
+                    })
+                }
+            }
+
+            #[cfg(feature = "parsing")]
+            impl Token for $name {
+                fn peek(cursor: Cursor) -> bool {
+                    parsing::peek_keyword(cursor, $token)
+                }
+
+                fn display() -> &'static str {
+                    concat!("`", $token, "`")
+                }
+            }
+
+            #[cfg(feature = "parsing")]
+            impl private::Sealed for $name {}
+        )*
+    };
+}
+
+macro_rules! impl_deref_if_len_is_1 {
+    ($name:ident/1) => {
+        impl Deref for $name {
+            type Target = WithSpan;
+
+            fn deref(&self) -> &Self::Target {
+                unsafe { &*(self as *const Self).cast::<WithSpan>() }
+            }
+        }
+
+        impl DerefMut for $name {
+            fn deref_mut(&mut self) -> &mut Self::Target {
+                unsafe { &mut *(self as *mut Self).cast::<WithSpan>() }
+            }
+        }
+    };
+
+    ($name:ident/$len:literal) => {};
+}
+
+macro_rules! define_punctuation_structs {
+    ($($token:literal pub struct $name:ident/$len:tt #[doc = $usage:literal])*) => {
+        $(
+            #[cfg_attr(not(doc), repr(transparent))]
+            #[allow(unknown_lints, repr_transparent_external_private_fields)] // False positive: https://github.com/rust-lang/rust/issues/78586#issuecomment-1722680482
+            #[doc = concat!('`', $token, '`')]
+            ///
+            /// Usage:
+            #[doc = concat!($usage, '.')]
+            ///
+            /// Don't try to remember the name of this type &mdash; use the
+            /// [`Token!`] macro instead.
+            ///
+            /// [`Token!`]: crate::token
+            pub struct $name {
+                pub spans: [Span; $len],
+            }
+
+            #[doc(hidden)]
+            #[allow(non_snake_case)]
+            pub fn $name<S: IntoSpans<[Span; $len]>>(spans: S) -> $name {
+                $name {
+                    spans: spans.into_spans(),
+                }
+            }
+
+            impl std::default::Default for $name {
+                fn default() -> Self {
+                    $name {
+                        spans: [Span::call_site(); $len],
+                    }
+                }
+            }
+
+            #[cfg(feature = "clone-impls")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "clone-impls")))]
+            impl Copy for $name {}
+
+            #[cfg(feature = "clone-impls")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "clone-impls")))]
+            impl Clone for $name {
+                fn clone(&self) -> Self {
+                    *self
+                }
+            }
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl Debug for $name {
+                fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                    f.write_str(stringify!($name))
+                }
+            }
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl cmp::Eq for $name {}
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl PartialEq for $name {
+                fn eq(&self, _other: &$name) -> bool {
+                    true
+                }
+            }
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl Hash for $name {
+                fn hash<H: Hasher>(&self, _state: &mut H) {}
+            }
+
+            impl_deref_if_len_is_1!($name/$len);
+        )*
+    };
+}
+
+macro_rules! define_punctuation {
+    ($($token:literal pub struct $name:ident/$len:tt #[doc = $usage:literal])*) => {
+        $(
+            define_punctuation_structs! {
+                $token pub struct $name/$len #[doc = $usage]
+            }
+
+            #[cfg(feature = "printing")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+            impl ToTokens for $name {
+                fn to_tokens(&self, tokens: &mut TokenStream) {
+                    printing::punct($token, &self.spans, tokens);
+                }
+            }
+
+            #[cfg(feature = "parsing")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+            impl Parse for $name {
+                fn parse(input: ParseStream) -> Result<Self> {
+                    Ok($name {
+                        spans: parsing::punct(input, $token)?,
+                    })
+                }
+            }
+
+            #[cfg(feature = "parsing")]
+            impl Token for $name {
+                fn peek(cursor: Cursor) -> bool {
+                    parsing::peek_punct(cursor, $token)
+                }
+
+                fn display() -> &'static str {
+                    concat!("`", $token, "`")
+                }
+            }
+
+            #[cfg(feature = "parsing")]
+            impl private::Sealed for $name {}
+        )*
+    };
+}
+
+macro_rules! define_delimiters {
+    ($($delim:ident pub struct $name:ident #[$doc:meta])*) => {
+        $(
+            #[$doc]
+            pub struct $name {
+                pub span: DelimSpan,
+            }
+
+            #[doc(hidden)]
+            #[allow(non_snake_case)]
+            pub fn $name<S: IntoSpans<DelimSpan>>(span: S) -> $name {
+                $name {
+                    span: span.into_spans(),
+                }
+            }
+
+            impl std::default::Default for $name {
+                fn default() -> Self {
+                    $name(Span::call_site())
+                }
+            }
+
+            #[cfg(feature = "clone-impls")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "clone-impls")))]
+            impl Copy for $name {}
+
+            #[cfg(feature = "clone-impls")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "clone-impls")))]
+            impl Clone for $name {
+                fn clone(&self) -> Self {
+                    *self
+                }
+            }
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl Debug for $name {
+                fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                    f.write_str(stringify!($name))
+                }
+            }
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl cmp::Eq for $name {}
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl PartialEq for $name {
+                fn eq(&self, _other: &$name) -> bool {
+                    true
+                }
+            }
+
+            #[cfg(feature = "extra-traits")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+            impl Hash for $name {
+                fn hash<H: Hasher>(&self, _state: &mut H) {}
+            }
+
+            impl $name {
+                #[cfg(feature = "printing")]
+                #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+                pub fn surround<F>(&self, tokens: &mut TokenStream, f: F)
+                where
+                    F: FnOnce(&mut TokenStream),
+                {
+                    let mut inner = TokenStream::new();
+                    f(&mut inner);
+                    printing::delim(Delimiter::$delim, self.span.join(), tokens, inner);
+                }
+            }
+
+            #[cfg(feature = "parsing")]
+            impl private::Sealed for $name {}
+        )*
+    };
+}
+
+define_punctuation_structs! {
+    "_" pub struct Underscore/1 /// wildcard patterns, inferred types, unnamed items in constants, extern crates, use declarations, and destructuring assignment
+}
+
+#[cfg(feature = "printing")]
+#[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+impl ToTokens for Underscore {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Ident::new("_", self.span));
+    }
+}
+
+#[cfg(feature = "parsing")]
+#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+impl Parse for Underscore {
+    fn parse(input: ParseStream) -> Result<Self> {
+        input.step(|cursor| {
+            if let Some((ident, rest)) = cursor.ident() {
+                if ident == "_" {
+                    return Ok((Underscore(ident.span()), rest));
+                }
+            }
+            if let Some((punct, rest)) = cursor.punct() {
+                if punct.as_char() == '_' {
+                    return Ok((Underscore(punct.span()), rest));
+                }
+            }
+            Err(cursor.error("expected `_`"))
+        })
+    }
+}
+
+#[cfg(feature = "parsing")]
+impl Token for Underscore {
+    fn peek(cursor: Cursor) -> bool {
+        if let Some((ident, _rest)) = cursor.ident() {
+            return ident == "_";
+        }
+        if let Some((punct, _rest)) = cursor.punct() {
+            return punct.as_char() == '_';
+        }
+        false
+    }
+
+    fn display() -> &'static str {
+        "`_`"
+    }
+}
+
+#[cfg(feature = "parsing")]
+impl private::Sealed for Underscore {}
+
+/// None-delimited group
+pub struct Group {
+    pub span: Span,
+}
+
+#[doc(hidden)]
+#[allow(non_snake_case)]
+pub fn Group<S: IntoSpans<Span>>(span: S) -> Group {
+    Group {
+        span: span.into_spans(),
+    }
+}
+
+impl std::default::Default for Group {
+    fn default() -> Self {
+        Group {
+            span: Span::call_site(),
+        }
+    }
+}
+
+#[cfg(feature = "clone-impls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "clone-impls")))]
+impl Copy for Group {}
+
+#[cfg(feature = "clone-impls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "clone-impls")))]
+impl Clone for Group {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+#[cfg(feature = "extra-traits")]
+#[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+impl Debug for Group {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str("Group")
+    }
+}
+
+#[cfg(feature = "extra-traits")]
+#[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+impl cmp::Eq for Group {}
+
+#[cfg(feature = "extra-traits")]
+#[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+impl PartialEq for Group {
+    fn eq(&self, _other: &Group) -> bool {
+        true
+    }
+}
+
+#[cfg(feature = "extra-traits")]
+#[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+impl Hash for Group {
+    fn hash<H: Hasher>(&self, _state: &mut H) {}
+}
+
+impl Group {
+    #[cfg(feature = "printing")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    pub fn surround<F>(&self, tokens: &mut TokenStream, f: F)
+    where
+        F: FnOnce(&mut TokenStream),
+    {
+        let mut inner = TokenStream::new();
+        f(&mut inner);
+        printing::delim(Delimiter::None, self.span, tokens, inner);
+    }
+}
+
+#[cfg(feature = "parsing")]
+impl private::Sealed for Group {}
+
+#[cfg(feature = "parsing")]
+impl Token for Paren {
+    fn peek(cursor: Cursor) -> bool {
+        cursor.group(Delimiter::Parenthesis).is_some()
+    }
+
+    fn display() -> &'static str {
+        "parentheses"
+    }
+}
+
+#[cfg(feature = "parsing")]
+impl Token for Brace {
+    fn peek(cursor: Cursor) -> bool {
+        cursor.group(Delimiter::Brace).is_some()
+    }
+
+    fn display() -> &'static str {
+        "curly braces"
+    }
+}
+
+#[cfg(feature = "parsing")]
+impl Token for Bracket {
+    fn peek(cursor: Cursor) -> bool {
+        cursor.group(Delimiter::Bracket).is_some()
+    }
+
+    fn display() -> &'static str {
+        "square brackets"
+    }
+}
+
+#[cfg(feature = "parsing")]
+impl Token for Group {
+    fn peek(cursor: Cursor) -> bool {
+        cursor.group(Delimiter::None).is_some()
+    }
+
+    fn display() -> &'static str {
+        "invisible group"
+    }
+}
+
+define_keywords! {
+    "abstract"    pub struct Abstract
+    "as"          pub struct As
+    "async"       pub struct Async
+    "auto"        pub struct Auto
+    "await"       pub struct Await
+    "become"      pub struct Become
+    "box"         pub struct Box
+    "break"       pub struct Break
+    "const"       pub struct Const
+    "continue"    pub struct Continue
+    "crate"       pub struct Crate
+    "default"     pub struct Default
+    "do"          pub struct Do
+    "dyn"         pub struct Dyn
+    "else"        pub struct Else
+    "enum"        pub struct Enum
+    "extern"      pub struct Extern
+    "final"       pub struct Final
+    "fn"          pub struct Fn
+    "for"         pub struct For
+    "if"          pub struct If
+    "impl"        pub struct Impl
+    "in"          pub struct In
+    "let"         pub struct Let
+    "loop"        pub struct Loop
+    "macro"       pub struct Macro
+    "match"       pub struct Match
+    "mod"         pub struct Mod
+    "move"        pub struct Move
+    "mut"         pub struct Mut
+    "override"    pub struct Override
+    "priv"        pub struct Priv
+    "pub"         pub struct Pub
+    "raw"         pub struct Raw
+    "ref"         pub struct Ref
+    "return"      pub struct Return
+    "Self"        pub struct SelfType
+    "self"        pub struct SelfValue
+    "static"      pub struct Static
+    "struct"      pub struct Struct
+    "super"       pub struct Super
+    "trait"       pub struct Trait
+    "try"         pub struct Try
+    "type"        pub struct Type
+    "typeof"      pub struct Typeof
+    "union"       pub struct Union
+    "unsafe"      pub struct Unsafe
+    "unsized"     pub struct Unsized
+    "use"         pub struct Use
+    "virtual"     pub struct Virtual
+    "where"       pub struct Where
+    "while"       pub struct While
+    "yield"       pub struct Yield
+}
+
+define_punctuation! {
+    "&"           pub struct And/1        /// bitwise and logical AND, borrow, references, reference patterns
+    "&&"          pub struct AndAnd/2     /// lazy AND, borrow, references, reference patterns
+    "&="          pub struct AndEq/2      /// bitwise AND assignment
+    "@"           pub struct At/1         /// subpattern binding
+    "^"           pub struct Caret/1      /// bitwise and logical XOR
+    "^="          pub struct CaretEq/2    /// bitwise XOR assignment
+    ":"           pub struct Colon/1      /// various separators
+    ","           pub struct Comma/1      /// various separators
+    "$"           pub struct Dollar/1     /// macros
+    "."           pub struct Dot/1        /// field access, tuple index
+    ".."          pub struct DotDot/2     /// range, struct expressions, patterns, range patterns
+    "..."         pub struct DotDotDot/3  /// variadic functions, range patterns
+    "..="         pub struct DotDotEq/3   /// inclusive range, range patterns
+    "="           pub struct Eq/1         /// assignment, attributes, various type definitions
+    "=="          pub struct EqEq/2       /// equal
+    "=>"          pub struct FatArrow/2   /// match arms, macros
+    ">="          pub struct Ge/2         /// greater than or equal to, generics
+    ">"           pub struct Gt/1         /// greater than, generics, paths
+    "<-"          pub struct LArrow/2     /// unused
+    "<="          pub struct Le/2         /// less than or equal to
+    "<"           pub struct Lt/1         /// less than, generics, paths
+    "-"           pub struct Minus/1      /// subtraction, negation
+    "-="          pub struct MinusEq/2    /// subtraction assignment
+    "!="          pub struct Ne/2         /// not equal
+    "!"           pub struct Not/1        /// bitwise and logical NOT, macro calls, inner attributes, never type, negative impls
+    "|"           pub struct Or/1         /// bitwise and logical OR, closures, patterns in match, if let, and while let
+    "|="          pub struct OrEq/2       /// bitwise OR assignment
+    "||"          pub struct OrOr/2       /// lazy OR, closures
+    "::"          pub struct PathSep/2    /// path separator
+    "%"           pub struct Percent/1    /// remainder
+    "%="          pub struct PercentEq/2  /// remainder assignment
+    "+"           pub struct Plus/1       /// addition, trait bounds, macro Kleene matcher
+    "+="          pub struct PlusEq/2     /// addition assignment
+    "#"           pub struct Pound/1      /// attributes
+    "?"           pub struct Question/1   /// question mark operator, questionably sized, macro Kleene matcher
+    "->"          pub struct RArrow/2     /// function return type, closure return type, function pointer type
+    ";"           pub struct Semi/1       /// terminator for various items and statements, array types
+    "<<"          pub struct Shl/2        /// shift left, nested generics
+    "<<="         pub struct ShlEq/3      /// shift left assignment
+    ">>"          pub struct Shr/2        /// shift right, nested generics
+    ">>="         pub struct ShrEq/3      /// shift right assignment, nested generics
+    "/"           pub struct Slash/1      /// division
+    "/="          pub struct SlashEq/2    /// division assignment
+    "*"           pub struct Star/1       /// multiplication, dereference, raw pointers, macro Kleene matcher, use wildcards
+    "*="          pub struct StarEq/2     /// multiplication assignment
+    "~"           pub struct Tilde/1      /// unused since before Rust 1.0
+}
+
+define_delimiters! {
+    Brace         pub struct Brace        /// `{`&hellip;`}`
+    Bracket       pub struct Bracket      /// `[`&hellip;`]`
+    Parenthesis   pub struct Paren        /// `(`&hellip;`)`
+}
+
+/// A type-macro that expands to the name of the Rust type representation of a
+/// given token.
+///
+/// As a type, `Token!` is commonly used in the type of struct fields, the type
+/// of a `let` statement, or in turbofish for a `parse` function.
+///
+/// ```
+/// use syn::{Ident, Token};
+/// use syn::parse::{Parse, ParseStream, Result};
+///
+/// // `struct Foo;`
+/// pub struct UnitStruct {
+///     struct_token: Token![struct],
+///     ident: Ident,
+///     semi_token: Token![;],
+/// }
+///
+/// impl Parse for UnitStruct {
+///     fn parse(input: ParseStream) -> Result<Self> {
+///         let struct_token: Token![struct] = input.parse()?;
+///         let ident: Ident = input.parse()?;
+///         let semi_token = input.parse::<Token![;]>()?;
+///         Ok(UnitStruct { struct_token, ident, semi_token })
+///     }
+/// }
+/// ```
+///
+/// As an expression, `Token!` is used for peeking tokens or instantiating
+/// tokens from a span.
+///
+/// ```
+/// # use syn::{Ident, Token};
+/// # use syn::parse::{Parse, ParseStream, Result};
+/// #
+/// # struct UnitStruct {
+/// #     struct_token: Token![struct],
+/// #     ident: Ident,
+/// #     semi_token: Token![;],
+/// # }
+/// #
+/// # impl Parse for UnitStruct {
+/// #     fn parse(input: ParseStream) -> Result<Self> {
+/// #         unimplemented!()
+/// #     }
+/// # }
+/// #
+/// fn make_unit_struct(name: Ident) -> UnitStruct {
+///     let span = name.span();
+///     UnitStruct {
+///         struct_token: Token![struct](span),
+///         ident: name,
+///         semi_token: Token![;](span),
+///     }
+/// }
+///
+/// # fn parse(input: ParseStream) -> Result<()> {
+/// if input.peek(Token![struct]) {
+///     let unit_struct: UnitStruct = input.parse()?;
+///     /* ... */
+/// }
+/// # Ok(())
+/// # }
+/// ```
+///
+/// See the [token module] documentation for details and examples.
+///
+/// [token module]: crate::token
+#[macro_export]
+macro_rules! Token {
+    [abstract]    => { $crate::token::Abstract };
+    [as]          => { $crate::token::As };
+    [async]       => { $crate::token::Async };
+    [auto]        => { $crate::token::Auto };
+    [await]       => { $crate::token::Await };
+    [become]      => { $crate::token::Become };
+    [box]         => { $crate::token::Box };
+    [break]       => { $crate::token::Break };
+    [const]       => { $crate::token::Const };
+    [continue]    => { $crate::token::Continue };
+    [crate]       => { $crate::token::Crate };
+    [default]     => { $crate::token::Default };
+    [do]          => { $crate::token::Do };
+    [dyn]         => { $crate::token::Dyn };
+    [else]        => { $crate::token::Else };
+    [enum]        => { $crate::token::Enum };
+    [extern]      => { $crate::token::Extern };
+    [final]       => { $crate::token::Final };
+    [fn]          => { $crate::token::Fn };
+    [for]         => { $crate::token::For };
+    [if]          => { $crate::token::If };
+    [impl]        => { $crate::token::Impl };
+    [in]          => { $crate::token::In };
+    [let]         => { $crate::token::Let };
+    [loop]        => { $crate::token::Loop };
+    [macro]       => { $crate::token::Macro };
+    [match]       => { $crate::token::Match };
+    [mod]         => { $crate::token::Mod };
+    [move]        => { $crate::token::Move };
+    [mut]         => { $crate::token::Mut };
+    [override]    => { $crate::token::Override };
+    [priv]        => { $crate::token::Priv };
+    [pub]         => { $crate::token::Pub };
+    [raw]         => { $crate::token::Raw };
+    [ref]         => { $crate::token::Ref };
+    [return]      => { $crate::token::Return };
+    [Self]        => { $crate::token::SelfType };
+    [self]        => { $crate::token::SelfValue };
+    [static]      => { $crate::token::Static };
+    [struct]      => { $crate::token::Struct };
+    [super]       => { $crate::token::Super };
+    [trait]       => { $crate::token::Trait };
+    [try]         => { $crate::token::Try };
+    [type]        => { $crate::token::Type };
+    [typeof]      => { $crate::token::Typeof };
+    [union]       => { $crate::token::Union };
+    [unsafe]      => { $crate::token::Unsafe };
+    [unsized]     => { $crate::token::Unsized };
+    [use]         => { $crate::token::Use };
+    [virtual]     => { $crate::token::Virtual };
+    [where]       => { $crate::token::Where };
+    [while]       => { $crate::token::While };
+    [yield]       => { $crate::token::Yield };
+    [&]           => { $crate::token::And };
+    [&&]          => { $crate::token::AndAnd };
+    [&=]          => { $crate::token::AndEq };
+    [@]           => { $crate::token::At };
+    [^]           => { $crate::token::Caret };
+    [^=]          => { $crate::token::CaretEq };
+    [:]           => { $crate::token::Colon };
+    [,]           => { $crate::token::Comma };
+    [$]           => { $crate::token::Dollar };
+    [.]           => { $crate::token::Dot };
+    [..]          => { $crate::token::DotDot };
+    [...]         => { $crate::token::DotDotDot };
+    [..=]         => { $crate::token::DotDotEq };
+    [=]           => { $crate::token::Eq };
+    [==]          => { $crate::token::EqEq };
+    [=>]          => { $crate::token::FatArrow };
+    [>=]          => { $crate::token::Ge };
+    [>]           => { $crate::token::Gt };
+    [<-]          => { $crate::token::LArrow };
+    [<=]          => { $crate::token::Le };
+    [<]           => { $crate::token::Lt };
+    [-]           => { $crate::token::Minus };
+    [-=]          => { $crate::token::MinusEq };
+    [!=]          => { $crate::token::Ne };
+    [!]           => { $crate::token::Not };
+    [|]           => { $crate::token::Or };
+    [|=]          => { $crate::token::OrEq };
+    [||]          => { $crate::token::OrOr };
+    [::]          => { $crate::token::PathSep };
+    [%]           => { $crate::token::Percent };
+    [%=]          => { $crate::token::PercentEq };
+    [+]           => { $crate::token::Plus };
+    [+=]          => { $crate::token::PlusEq };
+    [#]           => { $crate::token::Pound };
+    [?]           => { $crate::token::Question };
+    [->]          => { $crate::token::RArrow };
+    [;]           => { $crate::token::Semi };
+    [<<]          => { $crate::token::Shl };
+    [<<=]         => { $crate::token::ShlEq };
+    [>>]          => { $crate::token::Shr };
+    [>>=]         => { $crate::token::ShrEq };
+    [/]           => { $crate::token::Slash };
+    [/=]          => { $crate::token::SlashEq };
+    [*]           => { $crate::token::Star };
+    [*=]          => { $crate::token::StarEq };
+    [~]           => { $crate::token::Tilde };
+    [_]           => { $crate::token::Underscore };
+}
+
+// Not public API.
+#[doc(hidden)]
+#[cfg(feature = "parsing")]
+pub(crate) mod parsing {
+    use crate::buffer::Cursor;
+    use crate::error::{Error, Result};
+    use crate::parse::ParseStream;
+    use proc_macro2::{Spacing, Span};
+
+    pub(crate) fn keyword(input: ParseStream, token: &str) -> Result<Span> {
+        input.step(|cursor| {
+            if let Some((ident, rest)) = cursor.ident() {
+                if ident == token {
+                    return Ok((ident.span(), rest));
+                }
+            }
+            Err(cursor.error(format!("expected `{}`", token)))
+        })
+    }
+
+    pub(crate) fn peek_keyword(cursor: Cursor, token: &str) -> bool {
+        if let Some((ident, _rest)) = cursor.ident() {
+            ident == token
+        } else {
+            false
+        }
+    }
+
+    #[doc(hidden)]
+    pub fn punct<const N: usize>(input: ParseStream, token: &str) -> Result<[Span; N]> {
+        let mut spans = [input.span(); N];
+        punct_helper(input, token, &mut spans)?;
+        Ok(spans)
+    }
+
+    fn punct_helper(input: ParseStream, token: &str, spans: &mut [Span]) -> Result<()> {
+        input.step(|cursor| {
+            let mut cursor = *cursor;
+            assert_eq!(token.len(), spans.len());
+
+            for (i, ch) in token.chars().enumerate() {
+                match cursor.punct() {
+                    Some((punct, rest)) => {
+                        spans[i] = punct.span();
+                        if punct.as_char() != ch {
+                            break;
+                        } else if i == token.len() - 1 {
+                            return Ok(((), rest));
+                        } else if punct.spacing() != Spacing::Joint {
+                            break;
+                        }
+                        cursor = rest;
+                    }
+                    None => break,
+                }
+            }
+
+            Err(Error::new(spans[0], format!("expected `{}`", token)))
+        })
+    }
+
+    #[doc(hidden)]
+    pub fn peek_punct(mut cursor: Cursor, token: &str) -> bool {
+        for (i, ch) in token.chars().enumerate() {
+            match cursor.punct() {
+                Some((punct, rest)) => {
+                    if punct.as_char() != ch {
+                        break;
+                    } else if i == token.len() - 1 {
+                        return true;
+                    } else if punct.spacing() != Spacing::Joint {
+                        break;
+                    }
+                    cursor = rest;
+                }
+                None => break,
+            }
+        }
+        false
+    }
+}
+
+// Not public API.
+#[doc(hidden)]
+#[cfg(feature = "printing")]
+pub(crate) mod printing {
+    use proc_macro2::{Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream};
+    use quote::TokenStreamExt;
+
+    #[doc(hidden)]
+    pub fn punct(s: &str, spans: &[Span], tokens: &mut TokenStream) {
+        assert_eq!(s.len(), spans.len());
+
+        let mut chars = s.chars();
+        let mut spans = spans.iter();
+        let ch = chars.next_back().unwrap();
+        let span = spans.next_back().unwrap();
+        for (ch, span) in chars.zip(spans) {
+            let mut op = Punct::new(ch, Spacing::Joint);
+            op.set_span(*span);
+            tokens.append(op);
+        }
+
+        let mut op = Punct::new(ch, Spacing::Alone);
+        op.set_span(*span);
+        tokens.append(op);
+    }
+
+    pub(crate) fn keyword(s: &str, span: Span, tokens: &mut TokenStream) {
+        tokens.append(Ident::new(s, span));
+    }
+
+    pub(crate) fn delim(
+        delim: Delimiter,
+        span: Span,
+        tokens: &mut TokenStream,
+        inner: TokenStream,
+    ) {
+        let mut g = Group::new(delim, inner);
+        g.set_span(span);
+        tokens.append(g);
+    }
+}