Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1328 insertions, 0 deletions

diff --git a/third_party/rust/proc-macro2/src/lib.rs b/third_party/rust/proc-macro2/src/lib.rs
new file mode 100644
index 0000000000..643ffdcb2c
--- /dev/null
+++ b/third_party/rust/proc-macro2/src/lib.rs
@@ -0,0 +1,1328 @@
+//! [![github]](https://github.com/dtolnay/proc-macro2) [![crates-io]](https://crates.io/crates/proc-macro2) [![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>
+//!
+//! A wrapper around the procedural macro API of the compiler's [`proc_macro`]
+//! crate. This library serves two purposes:
+//!
+//! [`proc_macro`]: https://doc.rust-lang.org/proc_macro/
+//!
+//! - **Bring proc-macro-like functionality to other contexts like build.rs and
+//!   main.rs.** Types from `proc_macro` are entirely specific to procedural
+//!   macros and cannot ever exist in code outside of a procedural macro.
+//!   Meanwhile `proc_macro2` types may exist anywhere including non-macro code.
+//!   By developing foundational libraries like [syn] and [quote] against
+//!   `proc_macro2` rather than `proc_macro`, the procedural macro ecosystem
+//!   becomes easily applicable to many other use cases and we avoid
+//!   reimplementing non-macro equivalents of those libraries.
+//!
+//! - **Make procedural macros unit testable.** As a consequence of being
+//!   specific to procedural macros, nothing that uses `proc_macro` can be
+//!   executed from a unit test. In order for helper libraries or components of
+//!   a macro to be testable in isolation, they must be implemented using
+//!   `proc_macro2`.
+//!
+//! [syn]: https://github.com/dtolnay/syn
+//! [quote]: https://github.com/dtolnay/quote
+//!
+//! # Usage
+//!
+//! The skeleton of a typical procedural macro typically looks like this:
+//!
+//! ```
+//! extern crate proc_macro;
+//!
+//! # const IGNORE: &str = stringify! {
+//! #[proc_macro_derive(MyDerive)]
+//! # };
+//! # #[cfg(wrap_proc_macro)]
+//! pub fn my_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+//!     let input = proc_macro2::TokenStream::from(input);
+//!
+//!     let output: proc_macro2::TokenStream = {
+//!         /* transform input */
+//!         # input
+//!     };
+//!
+//!     proc_macro::TokenStream::from(output)
+//! }
+//! ```
+//!
+//! If parsing with [Syn], you'll use [`parse_macro_input!`] instead to
+//! propagate parse errors correctly back to the compiler when parsing fails.
+//!
+//! [`parse_macro_input!`]: https://docs.rs/syn/2.0/syn/macro.parse_macro_input.html
+//!
+//! # Unstable features
+//!
+//! The default feature set of proc-macro2 tracks the most recent stable
+//! compiler API. Functionality in `proc_macro` that is not yet stable is not
+//! exposed by proc-macro2 by default.
+//!
+//! To opt into the additional APIs available in the most recent nightly
+//! compiler, the `procmacro2_semver_exempt` config flag must be passed to
+//! rustc. We will polyfill those nightly-only APIs back to Rust 1.56.0. As
+//! these are unstable APIs that track the nightly compiler, minor versions of
+//! proc-macro2 may make breaking changes to them at any time.
+//!
+//! ```sh
+//! RUSTFLAGS='--cfg procmacro2_semver_exempt' cargo build
+//! ```
+//!
+//! Note that this must not only be done for your crate, but for any crate that
+//! depends on your crate. This infectious nature is intentional, as it serves
+//! as a reminder that you are outside of the normal semver guarantees.
+//!
+//! Semver exempt methods are marked as such in the proc-macro2 documentation.
+//!
+//! # Thread-Safety
+//!
+//! Most types in this crate are `!Sync` because the underlying compiler
+//! types make use of thread-local memory, meaning they cannot be accessed from
+//! a different thread.
+
+// Proc-macro2 types in rustdoc of other crates get linked to here.
+#![doc(html_root_url = "https://docs.rs/proc-macro2/1.0.74")]
+#![cfg_attr(any(proc_macro_span, super_unstable), feature(proc_macro_span))]
+#![cfg_attr(super_unstable, feature(proc_macro_def_site))]
+#![cfg_attr(doc_cfg, feature(doc_cfg))]
+#![deny(unsafe_op_in_unsafe_fn)]
+#![allow(
+    clippy::cast_lossless,
+    clippy::cast_possible_truncation,
+    clippy::checked_conversions,
+    clippy::doc_markdown,
+    clippy::items_after_statements,
+    clippy::iter_without_into_iter,
+    clippy::let_underscore_untyped,
+    clippy::manual_assert,
+    clippy::manual_range_contains,
+    clippy::missing_safety_doc,
+    clippy::must_use_candidate,
+    clippy::needless_doctest_main,
+    clippy::new_without_default,
+    clippy::return_self_not_must_use,
+    clippy::shadow_unrelated,
+    clippy::trivially_copy_pass_by_ref,
+    clippy::unnecessary_wraps,
+    clippy::unused_self,
+    clippy::used_underscore_binding,
+    clippy::vec_init_then_push
+)]
+
+#[cfg(all(procmacro2_semver_exempt, wrap_proc_macro, not(super_unstable)))]
+compile_error! {"\
+    Something is not right. If you've tried to turn on \
+    procmacro2_semver_exempt, you need to ensure that it \
+    is turned on for the compilation of the proc-macro2 \
+    build script as well.
+"}
+
+#[cfg(all(
+    procmacro2_nightly_testing,
+    feature = "proc-macro",
+    not(proc_macro_span)
+))]
+compile_error! {"\
+    Build script probe failed to compile.
+"}
+
+extern crate alloc;
+
+#[cfg(feature = "proc-macro")]
+extern crate proc_macro;
+
+mod marker;
+mod parse;
+mod rcvec;
+
+#[cfg(wrap_proc_macro)]
+mod detection;
+
+// Public for proc_macro2::fallback::force() and unforce(), but those are quite
+// a niche use case so we omit it from rustdoc.
+#[doc(hidden)]
+pub mod fallback;
+
+pub mod extra;
+
+#[cfg(not(wrap_proc_macro))]
+use crate::fallback as imp;
+#[path = "wrapper.rs"]
+#[cfg(wrap_proc_macro)]
+mod imp;
+
+#[cfg(span_locations)]
+mod location;
+
+use crate::extra::DelimSpan;
+use crate::marker::Marker;
+use core::cmp::Ordering;
+use core::fmt::{self, Debug, Display};
+use core::hash::{Hash, Hasher};
+use core::ops::RangeBounds;
+use core::str::FromStr;
+use std::error::Error;
+#[cfg(procmacro2_semver_exempt)]
+use std::path::PathBuf;
+
+#[cfg(span_locations)]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "span-locations")))]
+pub use crate::location::LineColumn;
+
+/// An abstract stream of tokens, or more concretely a sequence of token trees.
+///
+/// This type provides interfaces for iterating over token trees and for
+/// collecting token trees into one stream.
+///
+/// Token stream is both the input and output of `#[proc_macro]`,
+/// `#[proc_macro_attribute]` and `#[proc_macro_derive]` definitions.
+#[derive(Clone)]
+pub struct TokenStream {
+    inner: imp::TokenStream,
+    _marker: Marker,
+}
+
+/// Error returned from `TokenStream::from_str`.
+pub struct LexError {
+    inner: imp::LexError,
+    _marker: Marker,
+}
+
+impl TokenStream {
+    fn _new(inner: imp::TokenStream) -> Self {
+        TokenStream {
+            inner,
+            _marker: Marker,
+        }
+    }
+
+    fn _new_fallback(inner: fallback::TokenStream) -> Self {
+        TokenStream {
+            inner: inner.into(),
+            _marker: Marker,
+        }
+    }
+
+    /// Returns an empty `TokenStream` containing no token trees.
+    pub fn new() -> Self {
+        TokenStream::_new(imp::TokenStream::new())
+    }
+
+    /// Checks if this `TokenStream` is empty.
+    pub fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+}
+
+/// `TokenStream::default()` returns an empty stream,
+/// i.e. this is equivalent with `TokenStream::new()`.
+impl Default for TokenStream {
+    fn default() -> Self {
+        TokenStream::new()
+    }
+}
+
+/// Attempts to break the string into tokens and parse those tokens into a token
+/// stream.
+///
+/// May fail for a number of reasons, for example, if the string contains
+/// unbalanced delimiters or characters not existing in the language.
+///
+/// NOTE: Some errors may cause panics instead of returning `LexError`. We
+/// reserve the right to change these errors into `LexError`s later.
+impl FromStr for TokenStream {
+    type Err = LexError;
+
+    fn from_str(src: &str) -> Result<TokenStream, LexError> {
+        let e = src.parse().map_err(|e| LexError {
+            inner: e,
+            _marker: Marker,
+        })?;
+        Ok(TokenStream::_new(e))
+    }
+}
+
+#[cfg(feature = "proc-macro")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "proc-macro")))]
+impl From<proc_macro::TokenStream> for TokenStream {
+    fn from(inner: proc_macro::TokenStream) -> Self {
+        TokenStream::_new(inner.into())
+    }
+}
+
+#[cfg(feature = "proc-macro")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "proc-macro")))]
+impl From<TokenStream> for proc_macro::TokenStream {
+    fn from(inner: TokenStream) -> Self {
+        inner.inner.into()
+    }
+}
+
+impl From<TokenTree> for TokenStream {
+    fn from(token: TokenTree) -> Self {
+        TokenStream::_new(imp::TokenStream::from(token))
+    }
+}
+
+impl Extend<TokenTree> for TokenStream {
+    fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, streams: I) {
+        self.inner.extend(streams);
+    }
+}
+
+impl Extend<TokenStream> for TokenStream {
+    fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I) {
+        self.inner
+            .extend(streams.into_iter().map(|stream| stream.inner));
+    }
+}
+
+/// Collects a number of token trees into a single stream.
+impl FromIterator<TokenTree> for TokenStream {
+    fn from_iter<I: IntoIterator<Item = TokenTree>>(streams: I) -> Self {
+        TokenStream::_new(streams.into_iter().collect())
+    }
+}
+impl FromIterator<TokenStream> for TokenStream {
+    fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self {
+        TokenStream::_new(streams.into_iter().map(|i| i.inner).collect())
+    }
+}
+
+/// Prints the token stream as a string that is supposed to be losslessly
+/// convertible back into the same token stream (modulo spans), except for
+/// possibly `TokenTree::Group`s with `Delimiter::None` delimiters and negative
+/// numeric literals.
+impl Display for TokenStream {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Display::fmt(&self.inner, f)
+    }
+}
+
+/// Prints token in a form convenient for debugging.
+impl Debug for TokenStream {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Debug::fmt(&self.inner, f)
+    }
+}
+
+impl LexError {
+    pub fn span(&self) -> Span {
+        Span::_new(self.inner.span())
+    }
+}
+
+impl Debug for LexError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Debug::fmt(&self.inner, f)
+    }
+}
+
+impl Display for LexError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Display::fmt(&self.inner, f)
+    }
+}
+
+impl Error for LexError {}
+
+/// The source file of a given `Span`.
+///
+/// This type is semver exempt and not exposed by default.
+#[cfg(all(procmacro2_semver_exempt, any(not(wrap_proc_macro), super_unstable)))]
+#[cfg_attr(doc_cfg, doc(cfg(procmacro2_semver_exempt)))]
+#[derive(Clone, PartialEq, Eq)]
+pub struct SourceFile {
+    inner: imp::SourceFile,
+    _marker: Marker,
+}
+
+#[cfg(all(procmacro2_semver_exempt, any(not(wrap_proc_macro), super_unstable)))]
+impl SourceFile {
+    fn _new(inner: imp::SourceFile) -> Self {
+        SourceFile {
+            inner,
+            _marker: Marker,
+        }
+    }
+
+    /// Get the path to this source file.
+    ///
+    /// ### Note
+    ///
+    /// If the code span associated with this `SourceFile` was generated by an
+    /// external macro, this may not be an actual path on the filesystem. Use
+    /// [`is_real`] to check.
+    ///
+    /// Also note that even if `is_real` returns `true`, if
+    /// `--remap-path-prefix` was passed on the command line, the path as given
+    /// may not actually be valid.
+    ///
+    /// [`is_real`]: #method.is_real
+    pub fn path(&self) -> PathBuf {
+        self.inner.path()
+    }
+
+    /// Returns `true` if this source file is a real source file, and not
+    /// generated by an external macro's expansion.
+    pub fn is_real(&self) -> bool {
+        self.inner.is_real()
+    }
+}
+
+#[cfg(all(procmacro2_semver_exempt, any(not(wrap_proc_macro), super_unstable)))]
+impl Debug for SourceFile {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Debug::fmt(&self.inner, f)
+    }
+}
+
+/// A region of source code, along with macro expansion information.
+#[derive(Copy, Clone)]
+pub struct Span {
+    inner: imp::Span,
+    _marker: Marker,
+}
+
+impl Span {
+    fn _new(inner: imp::Span) -> Self {
+        Span {
+            inner,
+            _marker: Marker,
+        }
+    }
+
+    fn _new_fallback(inner: fallback::Span) -> Self {
+        Span {
+            inner: inner.into(),
+            _marker: Marker,
+        }
+    }
+
+    /// The span of the invocation of the current procedural macro.
+    ///
+    /// Identifiers created with this span will be resolved as if they were
+    /// written directly at the macro call location (call-site hygiene) and
+    /// other code at the macro call site will be able to refer to them as well.
+    pub fn call_site() -> Self {
+        Span::_new(imp::Span::call_site())
+    }
+
+    /// The span located at the invocation of the procedural macro, but with
+    /// local variables, labels, and `$crate` resolved at the definition site
+    /// of the macro. This is the same hygiene behavior as `macro_rules`.
+    pub fn mixed_site() -> Self {
+        Span::_new(imp::Span::mixed_site())
+    }
+
+    /// A span that resolves at the macro definition site.
+    ///
+    /// This method is semver exempt and not exposed by default.
+    #[cfg(procmacro2_semver_exempt)]
+    #[cfg_attr(doc_cfg, doc(cfg(procmacro2_semver_exempt)))]
+    pub fn def_site() -> Self {
+        Span::_new(imp::Span::def_site())
+    }
+
+    /// Creates a new span with the same line/column information as `self` but
+    /// that resolves symbols as though it were at `other`.
+    pub fn resolved_at(&self, other: Span) -> Span {
+        Span::_new(self.inner.resolved_at(other.inner))
+    }
+
+    /// Creates a new span with the same name resolution behavior as `self` but
+    /// with the line/column information of `other`.
+    pub fn located_at(&self, other: Span) -> Span {
+        Span::_new(self.inner.located_at(other.inner))
+    }
+
+    /// Convert `proc_macro2::Span` to `proc_macro::Span`.
+    ///
+    /// This method is available when building with a nightly compiler, or when
+    /// building with rustc 1.29+ *without* semver exempt features.
+    ///
+    /// # Panics
+    ///
+    /// Panics if called from outside of a procedural macro. Unlike
+    /// `proc_macro2::Span`, the `proc_macro::Span` type can only exist within
+    /// the context of a procedural macro invocation.
+    #[cfg(wrap_proc_macro)]
+    pub fn unwrap(self) -> proc_macro::Span {
+        self.inner.unwrap()
+    }
+
+    // Soft deprecated. Please use Span::unwrap.
+    #[cfg(wrap_proc_macro)]
+    #[doc(hidden)]
+    pub fn unstable(self) -> proc_macro::Span {
+        self.unwrap()
+    }
+
+    /// The original source file into which this span points.
+    ///
+    /// This method is semver exempt and not exposed by default.
+    #[cfg(all(procmacro2_semver_exempt, any(not(wrap_proc_macro), super_unstable)))]
+    #[cfg_attr(doc_cfg, doc(cfg(procmacro2_semver_exempt)))]
+    pub fn source_file(&self) -> SourceFile {
+        SourceFile::_new(self.inner.source_file())
+    }
+
+    /// Get the starting line/column in the source file for this span.
+    ///
+    /// This method requires the `"span-locations"` feature to be enabled.
+    ///
+    /// When executing in a procedural macro context, the returned line/column
+    /// are only meaningful if compiled with a nightly toolchain. The stable
+    /// toolchain does not have this information available. When executing
+    /// outside of a procedural macro, such as main.rs or build.rs, the
+    /// line/column are always meaningful regardless of toolchain.
+    #[cfg(span_locations)]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "span-locations")))]
+    pub fn start(&self) -> LineColumn {
+        self.inner.start()
+    }
+
+    /// Get the ending line/column in the source file for this span.
+    ///
+    /// This method requires the `"span-locations"` feature to be enabled.
+    ///
+    /// When executing in a procedural macro context, the returned line/column
+    /// are only meaningful if compiled with a nightly toolchain. The stable
+    /// toolchain does not have this information available. When executing
+    /// outside of a procedural macro, such as main.rs or build.rs, the
+    /// line/column are always meaningful regardless of toolchain.
+    #[cfg(span_locations)]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "span-locations")))]
+    pub fn end(&self) -> LineColumn {
+        self.inner.end()
+    }
+
+    /// Create a new span encompassing `self` and `other`.
+    ///
+    /// Returns `None` if `self` and `other` are from different files.
+    ///
+    /// Warning: the underlying [`proc_macro::Span::join`] method is
+    /// nightly-only. When called from within a procedural macro not using a
+    /// nightly compiler, this method will always return `None`.
+    ///
+    /// [`proc_macro::Span::join`]: https://doc.rust-lang.org/proc_macro/struct.Span.html#method.join
+    pub fn join(&self, other: Span) -> Option<Span> {
+        self.inner.join(other.inner).map(Span::_new)
+    }
+
+    /// Compares two spans to see if they're equal.
+    ///
+    /// This method is semver exempt and not exposed by default.
+    #[cfg(procmacro2_semver_exempt)]
+    #[cfg_attr(doc_cfg, doc(cfg(procmacro2_semver_exempt)))]
+    pub fn eq(&self, other: &Span) -> bool {
+        self.inner.eq(&other.inner)
+    }
+
+    /// Returns the source text behind a span. This preserves the original
+    /// source code, including spaces and comments. It only returns a result if
+    /// the span corresponds to real source code.
+    ///
+    /// Note: The observable result of a macro should only rely on the tokens
+    /// and not on this source text. The result of this function is a best
+    /// effort to be used for diagnostics only.
+    pub fn source_text(&self) -> Option<String> {
+        self.inner.source_text()
+    }
+}
+
+/// Prints a span in a form convenient for debugging.
+impl Debug for Span {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Debug::fmt(&self.inner, f)
+    }
+}
+
+/// A single token or a delimited sequence of token trees (e.g. `[1, (), ..]`).
+#[derive(Clone)]
+pub enum TokenTree {
+    /// A token stream surrounded by bracket delimiters.
+    Group(Group),
+    /// An identifier.
+    Ident(Ident),
+    /// A single punctuation character (`+`, `,`, `$`, etc.).
+    Punct(Punct),
+    /// A literal character (`'a'`), string (`"hello"`), number (`2.3`), etc.
+    Literal(Literal),
+}
+
+impl TokenTree {
+    /// Returns the span of this tree, delegating to the `span` method of
+    /// the contained token or a delimited stream.
+    pub fn span(&self) -> Span {
+        match self {
+            TokenTree::Group(t) => t.span(),
+            TokenTree::Ident(t) => t.span(),
+            TokenTree::Punct(t) => t.span(),
+            TokenTree::Literal(t) => t.span(),
+        }
+    }
+
+    /// Configures the span for *only this token*.
+    ///
+    /// Note that if this token is a `Group` then this method will not configure
+    /// the span of each of the internal tokens, this will simply delegate to
+    /// the `set_span` method of each variant.
+    pub fn set_span(&mut self, span: Span) {
+        match self {
+            TokenTree::Group(t) => t.set_span(span),
+            TokenTree::Ident(t) => t.set_span(span),
+            TokenTree::Punct(t) => t.set_span(span),
+            TokenTree::Literal(t) => t.set_span(span),
+        }
+    }
+}
+
+impl From<Group> for TokenTree {
+    fn from(g: Group) -> Self {
+        TokenTree::Group(g)
+    }
+}
+
+impl From<Ident> for TokenTree {
+    fn from(g: Ident) -> Self {
+        TokenTree::Ident(g)
+    }
+}
+
+impl From<Punct> for TokenTree {
+    fn from(g: Punct) -> Self {
+        TokenTree::Punct(g)
+    }
+}
+
+impl From<Literal> for TokenTree {
+    fn from(g: Literal) -> Self {
+        TokenTree::Literal(g)
+    }
+}
+
+/// Prints the token tree as a string that is supposed to be losslessly
+/// convertible back into the same token tree (modulo spans), except for
+/// possibly `TokenTree::Group`s with `Delimiter::None` delimiters and negative
+/// numeric literals.
+impl Display for TokenTree {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            TokenTree::Group(t) => Display::fmt(t, f),
+            TokenTree::Ident(t) => Display::fmt(t, f),
+            TokenTree::Punct(t) => Display::fmt(t, f),
+            TokenTree::Literal(t) => Display::fmt(t, f),
+        }
+    }
+}
+
+/// Prints token tree in a form convenient for debugging.
+impl Debug for TokenTree {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        // Each of these has the name in the struct type in the derived debug,
+        // so don't bother with an extra layer of indirection
+        match self {
+            TokenTree::Group(t) => Debug::fmt(t, f),
+            TokenTree::Ident(t) => {
+                let mut debug = f.debug_struct("Ident");
+                debug.field("sym", &format_args!("{}", t));
+                imp::debug_span_field_if_nontrivial(&mut debug, t.span().inner);
+                debug.finish()
+            }
+            TokenTree::Punct(t) => Debug::fmt(t, f),
+            TokenTree::Literal(t) => Debug::fmt(t, f),
+        }
+    }
+}
+
+/// A delimited token stream.
+///
+/// A `Group` internally contains a `TokenStream` which is surrounded by
+/// `Delimiter`s.
+#[derive(Clone)]
+pub struct Group {
+    inner: imp::Group,
+}
+
+/// Describes how a sequence of token trees is delimited.
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum Delimiter {
+    /// `( ... )`
+    Parenthesis,
+    /// `{ ... }`
+    Brace,
+    /// `[ ... ]`
+    Bracket,
+    /// `Ø ... Ø`
+    ///
+    /// An implicit delimiter, that may, for example, appear around tokens
+    /// coming from a "macro variable" `$var`. It is important to preserve
+    /// operator priorities in cases like `$var * 3` where `$var` is `1 + 2`.
+    /// Implicit delimiters may not survive roundtrip of a token stream through
+    /// a string.
+    None,
+}
+
+impl Group {
+    fn _new(inner: imp::Group) -> Self {
+        Group { inner }
+    }
+
+    fn _new_fallback(inner: fallback::Group) -> Self {
+        Group {
+            inner: inner.into(),
+        }
+    }
+
+    /// Creates a new `Group` with the given delimiter and token stream.
+    ///
+    /// This constructor will set the span for this group to
+    /// `Span::call_site()`. To change the span you can use the `set_span`
+    /// method below.
+    pub fn new(delimiter: Delimiter, stream: TokenStream) -> Self {
+        Group {
+            inner: imp::Group::new(delimiter, stream.inner),
+        }
+    }
+
+    /// Returns the punctuation used as the delimiter for this group: a set of
+    /// parentheses, square brackets, or curly braces.
+    pub fn delimiter(&self) -> Delimiter {
+        self.inner.delimiter()
+    }
+
+    /// Returns the `TokenStream` of tokens that are delimited in this `Group`.
+    ///
+    /// Note that the returned token stream does not include the delimiter
+    /// returned above.
+    pub fn stream(&self) -> TokenStream {
+        TokenStream::_new(self.inner.stream())
+    }
+
+    /// Returns the span for the delimiters of this token stream, spanning the
+    /// entire `Group`.
+    ///
+    /// ```text
+    /// pub fn span(&self) -> Span {
+    ///            ^^^^^^^
+    /// ```
+    pub fn span(&self) -> Span {
+        Span::_new(self.inner.span())
+    }
+
+    /// Returns the span pointing to the opening delimiter of this group.
+    ///
+    /// ```text
+    /// pub fn span_open(&self) -> Span {
+    ///                 ^
+    /// ```
+    pub fn span_open(&self) -> Span {
+        Span::_new(self.inner.span_open())
+    }
+
+    /// Returns the span pointing to the closing delimiter of this group.
+    ///
+    /// ```text
+    /// pub fn span_close(&self) -> Span {
+    ///                        ^
+    /// ```
+    pub fn span_close(&self) -> Span {
+        Span::_new(self.inner.span_close())
+    }
+
+    /// Returns an object that holds this group's `span_open()` and
+    /// `span_close()` together (in a more compact representation than holding
+    /// those 2 spans individually).
+    pub fn delim_span(&self) -> DelimSpan {
+        DelimSpan::new(&self.inner)
+    }
+
+    /// Configures the span for this `Group`'s delimiters, but not its internal
+    /// tokens.
+    ///
+    /// This method will **not** set the span of all the internal tokens spanned
+    /// by this group, but rather it will only set the span of the delimiter
+    /// tokens at the level of the `Group`.
+    pub fn set_span(&mut self, span: Span) {
+        self.inner.set_span(span.inner);
+    }
+}
+
+/// Prints the group as a string that should be losslessly convertible back
+/// into the same group (modulo spans), except for possibly `TokenTree::Group`s
+/// with `Delimiter::None` delimiters.
+impl Display for Group {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        Display::fmt(&self.inner, formatter)
+    }
+}
+
+impl Debug for Group {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        Debug::fmt(&self.inner, formatter)
+    }
+}
+
+/// A `Punct` is a single punctuation character like `+`, `-` or `#`.
+///
+/// Multicharacter operators like `+=` are represented as two instances of
+/// `Punct` with different forms of `Spacing` returned.
+#[derive(Clone)]
+pub struct Punct {
+    ch: char,
+    spacing: Spacing,
+    span: Span,
+}
+
+/// Whether a `Punct` is followed immediately by another `Punct` or followed by
+/// another token or whitespace.
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum Spacing {
+    /// E.g. `+` is `Alone` in `+ =`, `+ident` or `+()`.
+    Alone,
+    /// E.g. `+` is `Joint` in `+=` or `'` is `Joint` in `'#`.
+    ///
+    /// Additionally, single quote `'` can join with identifiers to form
+    /// lifetimes `'ident`.
+    Joint,
+}
+
+impl Punct {
+    /// Creates a new `Punct` from the given character and spacing.
+    ///
+    /// The `ch` argument must be a valid punctuation character permitted by the
+    /// language, otherwise the function will panic.
+    ///
+    /// The returned `Punct` will have the default span of `Span::call_site()`
+    /// which can be further configured with the `set_span` method below.
+    pub fn new(ch: char, spacing: Spacing) -> Self {
+        Punct {
+            ch,
+            spacing,
+            span: Span::call_site(),
+        }
+    }
+
+    /// Returns the value of this punctuation character as `char`.
+    pub fn as_char(&self) -> char {
+        self.ch
+    }
+
+    /// Returns the spacing of this punctuation character, indicating whether
+    /// it's immediately followed by another `Punct` in the token stream, so
+    /// they can potentially be combined into a multicharacter operator
+    /// (`Joint`), or it's followed by some other token or whitespace (`Alone`)
+    /// so the operator has certainly ended.
+    pub fn spacing(&self) -> Spacing {
+        self.spacing
+    }
+
+    /// Returns the span for this punctuation character.
+    pub fn span(&self) -> Span {
+        self.span
+    }
+
+    /// Configure the span for this punctuation character.
+    pub fn set_span(&mut self, span: Span) {
+        self.span = span;
+    }
+}
+
+/// Prints the punctuation character as a string that should be losslessly
+/// convertible back into the same character.
+impl Display for Punct {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Display::fmt(&self.ch, f)
+    }
+}
+
+impl Debug for Punct {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        let mut debug = fmt.debug_struct("Punct");
+        debug.field("char", &self.ch);
+        debug.field("spacing", &self.spacing);
+        imp::debug_span_field_if_nontrivial(&mut debug, self.span.inner);
+        debug.finish()
+    }
+}
+
+/// A word of Rust code, which may be a keyword or legal variable name.
+///
+/// An identifier consists of at least one Unicode code point, the first of
+/// which has the XID_Start property and the rest of which have the XID_Continue
+/// property.
+///
+/// - The empty string is not an identifier. Use `Option<Ident>`.
+/// - A lifetime is not an identifier. Use `syn::Lifetime` instead.
+///
+/// An identifier constructed with `Ident::new` is permitted to be a Rust
+/// keyword, though parsing one through its [`Parse`] implementation rejects
+/// Rust keywords. Use `input.call(Ident::parse_any)` when parsing to match the
+/// behaviour of `Ident::new`.
+///
+/// [`Parse`]: https://docs.rs/syn/2.0/syn/parse/trait.Parse.html
+///
+/// # Examples
+///
+/// A new ident can be created from a string using the `Ident::new` function.
+/// A span must be provided explicitly which governs the name resolution
+/// behavior of the resulting identifier.
+///
+/// ```
+/// use proc_macro2::{Ident, Span};
+///
+/// fn main() {
+///     let call_ident = Ident::new("calligraphy", Span::call_site());
+///
+///     println!("{}", call_ident);
+/// }
+/// ```
+///
+/// An ident can be interpolated into a token stream using the `quote!` macro.
+///
+/// ```
+/// use proc_macro2::{Ident, Span};
+/// use quote::quote;
+///
+/// fn main() {
+///     let ident = Ident::new("demo", Span::call_site());
+///
+///     // Create a variable binding whose name is this ident.
+///     let expanded = quote! { let #ident = 10; };
+///
+///     // Create a variable binding with a slightly different name.
+///     let temp_ident = Ident::new(&format!("new_{}", ident), Span::call_site());
+///     let expanded = quote! { let #temp_ident = 10; };
+/// }
+/// ```
+///
+/// A string representation of the ident is available through the `to_string()`
+/// method.
+///
+/// ```
+/// # use proc_macro2::{Ident, Span};
+/// #
+/// # let ident = Ident::new("another_identifier", Span::call_site());
+/// #
+/// // Examine the ident as a string.
+/// let ident_string = ident.to_string();
+/// if ident_string.len() > 60 {
+///     println!("Very long identifier: {}", ident_string)
+/// }
+/// ```
+#[derive(Clone)]
+pub struct Ident {
+    inner: imp::Ident,
+    _marker: Marker,
+}
+
+impl Ident {
+    fn _new(inner: imp::Ident) -> Self {
+        Ident {
+            inner,
+            _marker: Marker,
+        }
+    }
+
+    /// Creates a new `Ident` with the given `string` as well as the specified
+    /// `span`.
+    ///
+    /// The `string` argument must be a valid identifier permitted by the
+    /// language, otherwise the function will panic.
+    ///
+    /// Note that `span`, currently in rustc, configures the hygiene information
+    /// for this identifier.
+    ///
+    /// As of this time `Span::call_site()` explicitly opts-in to "call-site"
+    /// hygiene meaning that identifiers created with this span will be resolved
+    /// as if they were written directly at the location of the macro call, and
+    /// other code at the macro call site will be able to refer to them as well.
+    ///
+    /// Later spans like `Span::def_site()` will allow to opt-in to
+    /// "definition-site" hygiene meaning that identifiers created with this
+    /// span will be resolved at the location of the macro definition and other
+    /// code at the macro call site will not be able to refer to them.
+    ///
+    /// Due to the current importance of hygiene this constructor, unlike other
+    /// tokens, requires a `Span` to be specified at construction.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the input string is neither a keyword nor a legal variable
+    /// name. If you are not sure whether the string contains an identifier and
+    /// need to handle an error case, use
+    /// <a href="https://docs.rs/syn/2.0/syn/fn.parse_str.html"><code
+    ///   style="padding-right:0;">syn::parse_str</code></a><code
+    ///   style="padding-left:0;">::&lt;Ident&gt;</code>
+    /// rather than `Ident::new`.
+    #[track_caller]
+    pub fn new(string: &str, span: Span) -> Self {
+        Ident::_new(imp::Ident::new_checked(string, span.inner))
+    }
+
+    /// Same as `Ident::new`, but creates a raw identifier (`r#ident`). The
+    /// `string` argument must be a valid identifier permitted by the language
+    /// (including keywords, e.g. `fn`). Keywords which are usable in path
+    /// segments (e.g. `self`, `super`) are not supported, and will cause a
+    /// panic.
+    #[track_caller]
+    pub fn new_raw(string: &str, span: Span) -> Self {
+        Ident::_new(imp::Ident::new_raw_checked(string, span.inner))
+    }
+
+    /// Returns the span of this `Ident`.
+    pub fn span(&self) -> Span {
+        Span::_new(self.inner.span())
+    }
+
+    /// Configures the span of this `Ident`, possibly changing its hygiene
+    /// context.
+    pub fn set_span(&mut self, span: Span) {
+        self.inner.set_span(span.inner);
+    }
+}
+
+impl PartialEq for Ident {
+    fn eq(&self, other: &Ident) -> bool {
+        self.inner == other.inner
+    }
+}
+
+impl<T> PartialEq<T> for Ident
+where
+    T: ?Sized + AsRef<str>,
+{
+    fn eq(&self, other: &T) -> bool {
+        self.inner == other
+    }
+}
+
+impl Eq for Ident {}
+
+impl PartialOrd for Ident {
+    fn partial_cmp(&self, other: &Ident) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for Ident {
+    fn cmp(&self, other: &Ident) -> Ordering {
+        self.to_string().cmp(&other.to_string())
+    }
+}
+
+impl Hash for Ident {
+    fn hash<H: Hasher>(&self, hasher: &mut H) {
+        self.to_string().hash(hasher);
+    }
+}
+
+/// Prints the identifier as a string that should be losslessly convertible back
+/// into the same identifier.
+impl Display for Ident {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Display::fmt(&self.inner, f)
+    }
+}
+
+impl Debug for Ident {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Debug::fmt(&self.inner, f)
+    }
+}
+
+/// A literal string (`"hello"`), byte string (`b"hello"`), character (`'a'`),
+/// byte character (`b'a'`), an integer or floating point number with or without
+/// a suffix (`1`, `1u8`, `2.3`, `2.3f32`).
+///
+/// Boolean literals like `true` and `false` do not belong here, they are
+/// `Ident`s.
+#[derive(Clone)]
+pub struct Literal {
+    inner: imp::Literal,
+    _marker: Marker,
+}
+
+macro_rules! suffixed_int_literals {
+    ($($name:ident => $kind:ident,)*) => ($(
+        /// Creates a new suffixed integer literal with the specified value.
+        ///
+        /// This function will create an integer like `1u32` where the integer
+        /// value specified is the first part of the token and the integral is
+        /// also suffixed at the end. Literals created from negative numbers may
+        /// not survive roundtrips through `TokenStream` or strings and may be
+        /// broken into two tokens (`-` and positive literal).
+        ///
+        /// Literals created through this method have the `Span::call_site()`
+        /// span by default, which can be configured with the `set_span` method
+        /// below.
+        pub fn $name(n: $kind) -> Literal {
+            Literal::_new(imp::Literal::$name(n))
+        }
+    )*)
+}
+
+macro_rules! unsuffixed_int_literals {
+    ($($name:ident => $kind:ident,)*) => ($(
+        /// Creates a new unsuffixed integer literal with the specified value.
+        ///
+        /// This function will create an integer like `1` where the integer
+        /// value specified is the first part of the token. No suffix is
+        /// specified on this token, meaning that invocations like
+        /// `Literal::i8_unsuffixed(1)` are equivalent to
+        /// `Literal::u32_unsuffixed(1)`. Literals created from negative numbers
+        /// may not survive roundtrips through `TokenStream` or strings and may
+        /// be broken into two tokens (`-` and positive literal).
+        ///
+        /// Literals created through this method have the `Span::call_site()`
+        /// span by default, which can be configured with the `set_span` method
+        /// below.
+        pub fn $name(n: $kind) -> Literal {
+            Literal::_new(imp::Literal::$name(n))
+        }
+    )*)
+}
+
+impl Literal {
+    fn _new(inner: imp::Literal) -> Self {
+        Literal {
+            inner,
+            _marker: Marker,
+        }
+    }
+
+    fn _new_fallback(inner: fallback::Literal) -> Self {
+        Literal {
+            inner: inner.into(),
+            _marker: Marker,
+        }
+    }
+
+    suffixed_int_literals! {
+        u8_suffixed => u8,
+        u16_suffixed => u16,
+        u32_suffixed => u32,
+        u64_suffixed => u64,
+        u128_suffixed => u128,
+        usize_suffixed => usize,
+        i8_suffixed => i8,
+        i16_suffixed => i16,
+        i32_suffixed => i32,
+        i64_suffixed => i64,
+        i128_suffixed => i128,
+        isize_suffixed => isize,
+    }
+
+    unsuffixed_int_literals! {
+        u8_unsuffixed => u8,
+        u16_unsuffixed => u16,
+        u32_unsuffixed => u32,
+        u64_unsuffixed => u64,
+        u128_unsuffixed => u128,
+        usize_unsuffixed => usize,
+        i8_unsuffixed => i8,
+        i16_unsuffixed => i16,
+        i32_unsuffixed => i32,
+        i64_unsuffixed => i64,
+        i128_unsuffixed => i128,
+        isize_unsuffixed => isize,
+    }
+
+    /// Creates a new unsuffixed floating-point literal.
+    ///
+    /// This constructor is similar to those like `Literal::i8_unsuffixed` where
+    /// the float's value is emitted directly into the token but no suffix is
+    /// used, so it may be inferred to be a `f64` later in the compiler.
+    /// Literals created from negative numbers may not survive round-trips
+    /// through `TokenStream` or strings and may be broken into two tokens (`-`
+    /// and positive literal).
+    ///
+    /// # Panics
+    ///
+    /// This function requires that the specified float is finite, for example
+    /// if it is infinity or NaN this function will panic.
+    pub fn f64_unsuffixed(f: f64) -> Literal {
+        assert!(f.is_finite());
+        Literal::_new(imp::Literal::f64_unsuffixed(f))
+    }
+
+    /// Creates a new suffixed floating-point literal.
+    ///
+    /// This constructor will create a literal like `1.0f64` where the value
+    /// specified is the preceding part of the token and `f64` is the suffix of
+    /// the token. This token will always be inferred to be an `f64` in the
+    /// compiler. Literals created from negative numbers may not survive
+    /// round-trips through `TokenStream` or strings and may be broken into two
+    /// tokens (`-` and positive literal).
+    ///
+    /// # Panics
+    ///
+    /// This function requires that the specified float is finite, for example
+    /// if it is infinity or NaN this function will panic.
+    pub fn f64_suffixed(f: f64) -> Literal {
+        assert!(f.is_finite());
+        Literal::_new(imp::Literal::f64_suffixed(f))
+    }
+
+    /// Creates a new unsuffixed floating-point literal.
+    ///
+    /// This constructor is similar to those like `Literal::i8_unsuffixed` where
+    /// the float's value is emitted directly into the token but no suffix is
+    /// used, so it may be inferred to be a `f64` later in the compiler.
+    /// Literals created from negative numbers may not survive round-trips
+    /// through `TokenStream` or strings and may be broken into two tokens (`-`
+    /// and positive literal).
+    ///
+    /// # Panics
+    ///
+    /// This function requires that the specified float is finite, for example
+    /// if it is infinity or NaN this function will panic.
+    pub fn f32_unsuffixed(f: f32) -> Literal {
+        assert!(f.is_finite());
+        Literal::_new(imp::Literal::f32_unsuffixed(f))
+    }
+
+    /// Creates a new suffixed floating-point literal.
+    ///
+    /// This constructor will create a literal like `1.0f32` where the value
+    /// specified is the preceding part of the token and `f32` is the suffix of
+    /// the token. This token will always be inferred to be an `f32` in the
+    /// compiler. Literals created from negative numbers may not survive
+    /// round-trips through `TokenStream` or strings and may be broken into two
+    /// tokens (`-` and positive literal).
+    ///
+    /// # Panics
+    ///
+    /// This function requires that the specified float is finite, for example
+    /// if it is infinity or NaN this function will panic.
+    pub fn f32_suffixed(f: f32) -> Literal {
+        assert!(f.is_finite());
+        Literal::_new(imp::Literal::f32_suffixed(f))
+    }
+
+    /// String literal.
+    pub fn string(string: &str) -> Literal {
+        Literal::_new(imp::Literal::string(string))
+    }
+
+    /// Character literal.
+    pub fn character(ch: char) -> Literal {
+        Literal::_new(imp::Literal::character(ch))
+    }
+
+    /// Byte string literal.
+    pub fn byte_string(s: &[u8]) -> Literal {
+        Literal::_new(imp::Literal::byte_string(s))
+    }
+
+    /// Returns the span encompassing this literal.
+    pub fn span(&self) -> Span {
+        Span::_new(self.inner.span())
+    }
+
+    /// Configures the span associated for this literal.
+    pub fn set_span(&mut self, span: Span) {
+        self.inner.set_span(span.inner);
+    }
+
+    /// Returns a `Span` that is a subset of `self.span()` containing only
+    /// the source bytes in range `range`. Returns `None` if the would-be
+    /// trimmed span is outside the bounds of `self`.
+    ///
+    /// Warning: the underlying [`proc_macro::Literal::subspan`] method is
+    /// nightly-only. When called from within a procedural macro not using a
+    /// nightly compiler, this method will always return `None`.
+    ///
+    /// [`proc_macro::Literal::subspan`]: https://doc.rust-lang.org/proc_macro/struct.Literal.html#method.subspan
+    pub fn subspan<R: RangeBounds<usize>>(&self, range: R) -> Option<Span> {
+        self.inner.subspan(range).map(Span::_new)
+    }
+
+    // Intended for the `quote!` macro to use when constructing a proc-macro2
+    // token out of a macro_rules $:literal token, which is already known to be
+    // a valid literal. This avoids reparsing/validating the literal's string
+    // representation. This is not public API other than for quote.
+    #[doc(hidden)]
+    pub unsafe fn from_str_unchecked(repr: &str) -> Self {
+        Literal::_new(unsafe { imp::Literal::from_str_unchecked(repr) })
+    }
+}
+
+impl FromStr for Literal {
+    type Err = LexError;
+
+    fn from_str(repr: &str) -> Result<Self, LexError> {
+        repr.parse().map(Literal::_new).map_err(|inner| LexError {
+            inner,
+            _marker: Marker,
+        })
+    }
+}
+
+impl Debug for Literal {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Debug::fmt(&self.inner, f)
+    }
+}
+
+impl Display for Literal {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Display::fmt(&self.inner, f)
+    }
+}
+
+/// Public implementation details for the `TokenStream` type, such as iterators.
+pub mod token_stream {
+    use crate::marker::Marker;
+    use crate::{imp, TokenTree};
+    use core::fmt::{self, Debug};
+
+    pub use crate::TokenStream;
+
+    /// An iterator over `TokenStream`'s `TokenTree`s.
+    ///
+    /// The iteration is "shallow", e.g. the iterator doesn't recurse into
+    /// delimited groups, and returns whole groups as token trees.
+    #[derive(Clone)]
+    pub struct IntoIter {
+        inner: imp::TokenTreeIter,
+        _marker: Marker,
+    }
+
+    impl Iterator for IntoIter {
+        type Item = TokenTree;
+
+        fn next(&mut self) -> Option<TokenTree> {
+            self.inner.next()
+        }
+
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            self.inner.size_hint()
+        }
+    }
+
+    impl Debug for IntoIter {
+        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+            f.write_str("TokenStream ")?;
+            f.debug_list().entries(self.clone()).finish()
+        }
+    }
+
+    impl IntoIterator for TokenStream {
+        type Item = TokenTree;
+        type IntoIter = IntoIter;
+
+        fn into_iter(self) -> IntoIter {
+            IntoIter {
+                inner: self.inner.into_iter(),
+                _marker: Marker,
+            }
+        }
+    }
+}