Deleted vendor folder

1 files changed, 0 insertions, 1386 deletions

diff --git a/vendor/syn/src/parse.rs b/vendor/syn/src/parse.rs
deleted file mode 100644
index 13f488d..0000000
--- a/vendor/syn/src/parse.rs
+++ /dev/null
@@ -1,1386 +0,0 @@
-//! Parsing interface for parsing a token stream into a syntax tree node.
-//!
-//! Parsing in Syn is built on parser functions that take in a [`ParseStream`]
-//! and produce a [`Result<T>`] where `T` is some syntax tree node. Underlying
-//! these parser functions is a lower level mechanism built around the
-//! [`Cursor`] type. `Cursor` is a cheaply copyable cursor over a range of
-//! tokens in a token stream.
-//!
-//! [`Result<T>`]: Result
-//! [`Cursor`]: crate::buffer::Cursor
-//!
-//! # Example
-//!
-//! Here is a snippet of parsing code to get a feel for the style of the
-//! library. We define data structures for a subset of Rust syntax including
-//! enums (not shown) and structs, then provide implementations of the [`Parse`]
-//! trait to parse these syntax tree data structures from a token stream.
-//!
-//! Once `Parse` impls have been defined, they can be called conveniently from a
-//! procedural macro through [`parse_macro_input!`] as shown at the bottom of
-//! the snippet. If the caller provides syntactically invalid input to the
-//! procedural macro, they will receive a helpful compiler error message
-//! pointing out the exact token that triggered the failure to parse.
-//!
-//! [`parse_macro_input!`]: crate::parse_macro_input!
-//!
-//! ```
-//! # extern crate proc_macro;
-//! #
-//! use proc_macro::TokenStream;
-//! use syn::{braced, parse_macro_input, token, Field, Ident, Result, Token};
-//! use syn::parse::{Parse, ParseStream};
-//! use syn::punctuated::Punctuated;
-//!
-//! enum Item {
-//!     Struct(ItemStruct),
-//!     Enum(ItemEnum),
-//! }
-//!
-//! struct ItemStruct {
-//!     struct_token: Token![struct],
-//!     ident: Ident,
-//!     brace_token: token::Brace,
-//!     fields: Punctuated<Field, Token![,]>,
-//! }
-//! #
-//! # enum ItemEnum {}
-//!
-//! impl Parse for Item {
-//!     fn parse(input: ParseStream) -> Result<Self> {
-//!         let lookahead = input.lookahead1();
-//!         if lookahead.peek(Token![struct]) {
-//!             input.parse().map(Item::Struct)
-//!         } else if lookahead.peek(Token![enum]) {
-//!             input.parse().map(Item::Enum)
-//!         } else {
-//!             Err(lookahead.error())
-//!         }
-//!     }
-//! }
-//!
-//! impl Parse for ItemStruct {
-//!     fn parse(input: ParseStream) -> Result<Self> {
-//!         let content;
-//!         Ok(ItemStruct {
-//!             struct_token: input.parse()?,
-//!             ident: input.parse()?,
-//!             brace_token: braced!(content in input),
-//!             fields: content.parse_terminated(Field::parse_named, Token![,])?,
-//!         })
-//!     }
-//! }
-//! #
-//! # impl Parse for ItemEnum {
-//! #     fn parse(input: ParseStream) -> Result<Self> {
-//! #         unimplemented!()
-//! #     }
-//! # }
-//!
-//! # const IGNORE: &str = stringify! {
-//! #[proc_macro]
-//! # };
-//! pub fn my_macro(tokens: TokenStream) -> TokenStream {
-//!     let input = parse_macro_input!(tokens as Item);
-//!
-//!     /* ... */
-//! #   TokenStream::new()
-//! }
-//! ```
-//!
-//! # The `syn::parse*` functions
-//!
-//! The [`syn::parse`], [`syn::parse2`], and [`syn::parse_str`] functions serve
-//! as an entry point for parsing syntax tree nodes that can be parsed in an
-//! obvious default way. These functions can return any syntax tree node that
-//! implements the [`Parse`] trait, which includes most types in Syn.
-//!
-//! [`syn::parse`]: crate::parse()
-//! [`syn::parse2`]: crate::parse2()
-//! [`syn::parse_str`]: crate::parse_str()
-//!
-//! ```
-//! use syn::Type;
-//!
-//! # fn run_parser() -> syn::Result<()> {
-//! let t: Type = syn::parse_str("std::collections::HashMap<String, Value>")?;
-//! #     Ok(())
-//! # }
-//! #
-//! # run_parser().unwrap();
-//! ```
-//!
-//! The [`parse_quote!`] macro also uses this approach.
-//!
-//! [`parse_quote!`]: crate::parse_quote!
-//!
-//! # The `Parser` trait
-//!
-//! Some types can be parsed in several ways depending on context. For example
-//! an [`Attribute`] can be either "outer" like `#[...]` or "inner" like
-//! `#![...]` and parsing the wrong one would be a bug. Similarly [`Punctuated`]
-//! may or may not allow trailing punctuation, and parsing it the wrong way
-//! would either reject valid input or accept invalid input.
-//!
-//! [`Attribute`]: crate::Attribute
-//! [`Punctuated`]: crate::punctuated
-//!
-//! The `Parse` trait is not implemented in these cases because there is no good
-//! behavior to consider the default.
-//!
-//! ```compile_fail
-//! # extern crate proc_macro;
-//! #
-//! # use syn::punctuated::Punctuated;
-//! # use syn::{PathSegment, Result, Token};
-//! #
-//! # fn f(tokens: proc_macro::TokenStream) -> Result<()> {
-//! #
-//! // Can't parse `Punctuated` without knowing whether trailing punctuation
-//! // should be allowed in this context.
-//! let path: Punctuated<PathSegment, Token![::]> = syn::parse(tokens)?;
-//! #
-//! #     Ok(())
-//! # }
-//! ```
-//!
-//! In these cases the types provide a choice of parser functions rather than a
-//! single `Parse` implementation, and those parser functions can be invoked
-//! through the [`Parser`] trait.
-//!
-//!
-//! ```
-//! # extern crate proc_macro;
-//! #
-//! use proc_macro::TokenStream;
-//! use syn::parse::Parser;
-//! use syn::punctuated::Punctuated;
-//! use syn::{Attribute, Expr, PathSegment, Result, Token};
-//!
-//! fn call_some_parser_methods(input: TokenStream) -> Result<()> {
-//!     // Parse a nonempty sequence of path segments separated by `::` punctuation
-//!     // with no trailing punctuation.
-//!     let tokens = input.clone();
-//!     let parser = Punctuated::<PathSegment, Token![::]>::parse_separated_nonempty;
-//!     let _path = parser.parse(tokens)?;
-//!
-//!     // Parse a possibly empty sequence of expressions terminated by commas with
-//!     // an optional trailing punctuation.
-//!     let tokens = input.clone();
-//!     let parser = Punctuated::<Expr, Token![,]>::parse_terminated;
-//!     let _args = parser.parse(tokens)?;
-//!
-//!     // Parse zero or more outer attributes but not inner attributes.
-//!     let tokens = input.clone();
-//!     let parser = Attribute::parse_outer;
-//!     let _attrs = parser.parse(tokens)?;
-//!
-//!     Ok(())
-//! }
-//! ```
-
-#[path = "discouraged.rs"]
-pub mod discouraged;
-
-use crate::buffer::{Cursor, TokenBuffer};
-use crate::error;
-use crate::lookahead;
-#[cfg(feature = "proc-macro")]
-use crate::proc_macro;
-use crate::punctuated::Punctuated;
-use crate::token::Token;
-use proc_macro2::{self, Delimiter, Group, Literal, Punct, Span, TokenStream, TokenTree};
-use std::cell::Cell;
-use std::fmt::{self, Debug, Display};
-#[cfg(feature = "extra-traits")]
-use std::hash::{Hash, Hasher};
-use std::marker::PhantomData;
-use std::mem;
-use std::ops::Deref;
-use std::rc::Rc;
-use std::str::FromStr;
-
-pub use crate::error::{Error, Result};
-pub use crate::lookahead::{Lookahead1, Peek};
-
-/// Parsing interface implemented by all types that can be parsed in a default
-/// way from a token stream.
-///
-/// Refer to the [module documentation] for details about implementing and using
-/// the `Parse` trait.
-///
-/// [module documentation]: self
-pub trait Parse: Sized {
-    fn parse(input: ParseStream) -> Result<Self>;
-}
-
-/// Input to a Syn parser function.
-///
-/// See the methods of this type under the documentation of [`ParseBuffer`]. For
-/// an overview of parsing in Syn, refer to the [module documentation].
-///
-/// [module documentation]: self
-pub type ParseStream<'a> = &'a ParseBuffer<'a>;
-
-/// Cursor position within a buffered token stream.
-///
-/// This type is more commonly used through the type alias [`ParseStream`] which
-/// is an alias for `&ParseBuffer`.
-///
-/// `ParseStream` is the input type for all parser functions in Syn. They have
-/// the signature `fn(ParseStream) -> Result<T>`.
-///
-/// ## Calling a parser function
-///
-/// There is no public way to construct a `ParseBuffer`. Instead, if you are
-/// looking to invoke a parser function that requires `ParseStream` as input,
-/// you will need to go through one of the public parsing entry points.
-///
-/// - The [`parse_macro_input!`] macro if parsing input of a procedural macro;
-/// - One of [the `syn::parse*` functions][syn-parse]; or
-/// - A method of the [`Parser`] trait.
-///
-/// [`parse_macro_input!`]: crate::parse_macro_input!
-/// [syn-parse]: self#the-synparse-functions
-pub struct ParseBuffer<'a> {
-    scope: Span,
-    // Instead of Cell<Cursor<'a>> so that ParseBuffer<'a> is covariant in 'a.
-    // The rest of the code in this module needs to be careful that only a
-    // cursor derived from this `cell` is ever assigned to this `cell`.
-    //
-    // Cell<Cursor<'a>> cannot be covariant in 'a because then we could take a
-    // ParseBuffer<'a>, upcast to ParseBuffer<'short> for some lifetime shorter
-    // than 'a, and then assign a Cursor<'short> into the Cell.
-    //
-    // By extension, it would not be safe to expose an API that accepts a
-    // Cursor<'a> and trusts that it lives as long as the cursor currently in
-    // the cell.
-    cell: Cell<Cursor<'static>>,
-    marker: PhantomData<Cursor<'a>>,
-    unexpected: Cell<Option<Rc<Cell<Unexpected>>>>,
-}
-
-impl<'a> Drop for ParseBuffer<'a> {
-    fn drop(&mut self) {
-        if let Some(unexpected_span) = span_of_unexpected_ignoring_nones(self.cursor()) {
-            let (inner, old_span) = inner_unexpected(self);
-            if old_span.is_none() {
-                inner.set(Unexpected::Some(unexpected_span));
-            }
-        }
-    }
-}
-
-impl<'a> Display for ParseBuffer<'a> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        Display::fmt(&self.cursor().token_stream(), f)
-    }
-}
-
-impl<'a> Debug for ParseBuffer<'a> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        Debug::fmt(&self.cursor().token_stream(), f)
-    }
-}
-
-/// Cursor state associated with speculative parsing.
-///
-/// This type is the input of the closure provided to [`ParseStream::step`].
-///
-/// [`ParseStream::step`]: ParseBuffer::step
-///
-/// # Example
-///
-/// ```
-/// use proc_macro2::TokenTree;
-/// use syn::Result;
-/// use syn::parse::ParseStream;
-///
-/// // This function advances the stream past the next occurrence of `@`. If
-/// // no `@` is present in the stream, the stream position is unchanged and
-/// // an error is returned.
-/// fn skip_past_next_at(input: ParseStream) -> Result<()> {
-///     input.step(|cursor| {
-///         let mut rest = *cursor;
-///         while let Some((tt, next)) = rest.token_tree() {
-///             match &tt {
-///                 TokenTree::Punct(punct) if punct.as_char() == '@' => {
-///                     return Ok(((), next));
-///                 }
-///                 _ => rest = next,
-///             }
-///         }
-///         Err(cursor.error("no `@` was found after this point"))
-///     })
-/// }
-/// #
-/// # fn remainder_after_skipping_past_next_at(
-/// #     input: ParseStream,
-/// # ) -> Result<proc_macro2::TokenStream> {
-/// #     skip_past_next_at(input)?;
-/// #     input.parse()
-/// # }
-/// #
-/// # use syn::parse::Parser;
-/// # let remainder = remainder_after_skipping_past_next_at
-/// #     .parse_str("a @ b c")
-/// #     .unwrap();
-/// # assert_eq!(remainder.to_string(), "b c");
-/// ```
-pub struct StepCursor<'c, 'a> {
-    scope: Span,
-    // This field is covariant in 'c.
-    cursor: Cursor<'c>,
-    // This field is contravariant in 'c. Together these make StepCursor
-    // invariant in 'c. Also covariant in 'a. The user cannot cast 'c to a
-    // different lifetime but can upcast into a StepCursor with a shorter
-    // lifetime 'a.
-    //
-    // As long as we only ever construct a StepCursor for which 'c outlives 'a,
-    // this means if ever a StepCursor<'c, 'a> exists we are guaranteed that 'c
-    // outlives 'a.
-    marker: PhantomData<fn(Cursor<'c>) -> Cursor<'a>>,
-}
-
-impl<'c, 'a> Deref for StepCursor<'c, 'a> {
-    type Target = Cursor<'c>;
-
-    fn deref(&self) -> &Self::Target {
-        &self.cursor
-    }
-}
-
-impl<'c, 'a> Copy for StepCursor<'c, 'a> {}
-
-impl<'c, 'a> Clone for StepCursor<'c, 'a> {
-    fn clone(&self) -> Self {
-        *self
-    }
-}
-
-impl<'c, 'a> StepCursor<'c, 'a> {
-    /// Triggers an error at the current position of the parse stream.
-    ///
-    /// The `ParseStream::step` invocation will return this same error without
-    /// advancing the stream state.
-    pub fn error<T: Display>(self, message: T) -> Error {
-        error::new_at(self.scope, self.cursor, message)
-    }
-}
-
-pub(crate) fn advance_step_cursor<'c, 'a>(proof: StepCursor<'c, 'a>, to: Cursor<'c>) -> Cursor<'a> {
-    // Refer to the comments within the StepCursor definition. We use the
-    // fact that a StepCursor<'c, 'a> exists as proof that 'c outlives 'a.
-    // Cursor is covariant in its lifetime parameter so we can cast a
-    // Cursor<'c> to one with the shorter lifetime Cursor<'a>.
-    let _ = proof;
-    unsafe { mem::transmute::<Cursor<'c>, Cursor<'a>>(to) }
-}
-
-pub(crate) fn new_parse_buffer(
-    scope: Span,
-    cursor: Cursor,
-    unexpected: Rc<Cell<Unexpected>>,
-) -> ParseBuffer {
-    ParseBuffer {
-        scope,
-        // See comment on `cell` in the struct definition.
-        cell: Cell::new(unsafe { mem::transmute::<Cursor, Cursor<'static>>(cursor) }),
-        marker: PhantomData,
-        unexpected: Cell::new(Some(unexpected)),
-    }
-}
-
-pub(crate) enum Unexpected {
-    None,
-    Some(Span),
-    Chain(Rc<Cell<Unexpected>>),
-}
-
-impl Default for Unexpected {
-    fn default() -> Self {
-        Unexpected::None
-    }
-}
-
-impl Clone for Unexpected {
-    fn clone(&self) -> Self {
-        match self {
-            Unexpected::None => Unexpected::None,
-            Unexpected::Some(span) => Unexpected::Some(*span),
-            Unexpected::Chain(next) => Unexpected::Chain(next.clone()),
-        }
-    }
-}
-
-// We call this on Cell<Unexpected> and Cell<Option<T>> where temporarily
-// swapping in a None is cheap.
-fn cell_clone<T: Default + Clone>(cell: &Cell<T>) -> T {
-    let prev = cell.take();
-    let ret = prev.clone();
-    cell.set(prev);
-    ret
-}
-
-fn inner_unexpected(buffer: &ParseBuffer) -> (Rc<Cell<Unexpected>>, Option<Span>) {
-    let mut unexpected = get_unexpected(buffer);
-    loop {
-        match cell_clone(&unexpected) {
-            Unexpected::None => return (unexpected, None),
-            Unexpected::Some(span) => return (unexpected, Some(span)),
-            Unexpected::Chain(next) => unexpected = next,
-        }
-    }
-}
-
-pub(crate) fn get_unexpected(buffer: &ParseBuffer) -> Rc<Cell<Unexpected>> {
-    cell_clone(&buffer.unexpected).unwrap()
-}
-
-fn span_of_unexpected_ignoring_nones(mut cursor: Cursor) -> Option<Span> {
-    if cursor.eof() {
-        return None;
-    }
-    while let Some((inner, _span, rest)) = cursor.group(Delimiter::None) {
-        if let Some(unexpected) = span_of_unexpected_ignoring_nones(inner) {
-            return Some(unexpected);
-        }
-        cursor = rest;
-    }
-    if cursor.eof() {
-        None
-    } else {
-        Some(cursor.span())
-    }
-}
-
-impl<'a> ParseBuffer<'a> {
-    /// Parses a syntax tree node of type `T`, advancing the position of our
-    /// parse stream past it.
-    pub fn parse<T: Parse>(&self) -> Result<T> {
-        T::parse(self)
-    }
-
-    /// Calls the given parser function to parse a syntax tree node of type `T`
-    /// from this stream.
-    ///
-    /// # Example
-    ///
-    /// The parser below invokes [`Attribute::parse_outer`] to parse a vector of
-    /// zero or more outer attributes.
-    ///
-    /// [`Attribute::parse_outer`]: crate::Attribute::parse_outer
-    ///
-    /// ```
-    /// use syn::{Attribute, Ident, Result, Token};
-    /// use syn::parse::{Parse, ParseStream};
-    ///
-    /// // Parses a unit struct with attributes.
-    /// //
-    /// //     #[path = "s.tmpl"]
-    /// //     struct S;
-    /// struct UnitStruct {
-    ///     attrs: Vec<Attribute>,
-    ///     struct_token: Token![struct],
-    ///     name: Ident,
-    ///     semi_token: Token![;],
-    /// }
-    ///
-    /// impl Parse for UnitStruct {
-    ///     fn parse(input: ParseStream) -> Result<Self> {
-    ///         Ok(UnitStruct {
-    ///             attrs: input.call(Attribute::parse_outer)?,
-    ///             struct_token: input.parse()?,
-    ///             name: input.parse()?,
-    ///             semi_token: input.parse()?,
-    ///         })
-    ///     }
-    /// }
-    /// ```
-    pub fn call<T>(&self, function: fn(ParseStream) -> Result<T>) -> Result<T> {
-        function(self)
-    }
-
-    /// Looks at the next token in the parse stream to determine whether it
-    /// matches the requested type of token.
-    ///
-    /// Does not advance the position of the parse stream.
-    ///
-    /// # Syntax
-    ///
-    /// Note that this method does not use turbofish syntax. Pass the peek type
-    /// inside of parentheses.
-    ///
-    /// - `input.peek(Token![struct])`
-    /// - `input.peek(Token![==])`
-    /// - `input.peek(syn::Ident)`&emsp;*(does not accept keywords)*
-    /// - `input.peek(syn::Ident::peek_any)`
-    /// - `input.peek(Lifetime)`
-    /// - `input.peek(token::Brace)`
-    ///
-    /// # Example
-    ///
-    /// In this example we finish parsing the list of supertraits when the next
-    /// token in the input is either `where` or an opening curly brace.
-    ///
-    /// ```
-    /// use syn::{braced, token, Generics, Ident, Result, Token, TypeParamBound};
-    /// use syn::parse::{Parse, ParseStream};
-    /// use syn::punctuated::Punctuated;
-    ///
-    /// // Parses a trait definition containing no associated items.
-    /// //
-    /// //     trait Marker<'de, T>: A + B<'de> where Box<T>: Clone {}
-    /// struct MarkerTrait {
-    ///     trait_token: Token![trait],
-    ///     ident: Ident,
-    ///     generics: Generics,
-    ///     colon_token: Option<Token![:]>,
-    ///     supertraits: Punctuated<TypeParamBound, Token![+]>,
-    ///     brace_token: token::Brace,
-    /// }
-    ///
-    /// impl Parse for MarkerTrait {
-    ///     fn parse(input: ParseStream) -> Result<Self> {
-    ///         let trait_token: Token![trait] = input.parse()?;
-    ///         let ident: Ident = input.parse()?;
-    ///         let mut generics: Generics = input.parse()?;
-    ///         let colon_token: Option<Token![:]> = input.parse()?;
-    ///
-    ///         let mut supertraits = Punctuated::new();
-    ///         if colon_token.is_some() {
-    ///             loop {
-    ///                 supertraits.push_value(input.parse()?);
-    ///                 if input.peek(Token![where]) || input.peek(token::Brace) {
-    ///                     break;
-    ///                 }
-    ///                 supertraits.push_punct(input.parse()?);
-    ///             }
-    ///         }
-    ///
-    ///         generics.where_clause = input.parse()?;
-    ///         let content;
-    ///         let empty_brace_token = braced!(content in input);
-    ///
-    ///         Ok(MarkerTrait {
-    ///             trait_token,
-    ///             ident,
-    ///             generics,
-    ///             colon_token,
-    ///             supertraits,
-    ///             brace_token: empty_brace_token,
-    ///         })
-    ///     }
-    /// }
-    /// ```
-    pub fn peek<T: Peek>(&self, token: T) -> bool {
-        let _ = token;
-        T::Token::peek(self.cursor())
-    }
-
-    /// Looks at the second-next token in the parse stream.
-    ///
-    /// This is commonly useful as a way to implement contextual keywords.
-    ///
-    /// # Example
-    ///
-    /// This example needs to use `peek2` because the symbol `union` is not a
-    /// keyword in Rust. We can't use just `peek` and decide to parse a union if
-    /// the very next token is `union`, because someone is free to write a `mod
-    /// union` and a macro invocation that looks like `union::some_macro! { ...
-    /// }`. In other words `union` is a contextual keyword.
-    ///
-    /// ```
-    /// use syn::{Ident, ItemUnion, Macro, Result, Token};
-    /// use syn::parse::{Parse, ParseStream};
-    ///
-    /// // Parses either a union or a macro invocation.
-    /// enum UnionOrMacro {
-    ///     // union MaybeUninit<T> { uninit: (), value: T }
-    ///     Union(ItemUnion),
-    ///     // lazy_static! { ... }
-    ///     Macro(Macro),
-    /// }
-    ///
-    /// impl Parse for UnionOrMacro {
-    ///     fn parse(input: ParseStream) -> Result<Self> {
-    ///         if input.peek(Token![union]) && input.peek2(Ident) {
-    ///             input.parse().map(UnionOrMacro::Union)
-    ///         } else {
-    ///             input.parse().map(UnionOrMacro::Macro)
-    ///         }
-    ///     }
-    /// }
-    /// ```
-    pub fn peek2<T: Peek>(&self, token: T) -> bool {
-        fn peek2(buffer: &ParseBuffer, peek: fn(Cursor) -> bool) -> bool {
-            if let Some(group) = buffer.cursor().group(Delimiter::None) {
-                if group.0.skip().map_or(false, peek) {
-                    return true;
-                }
-            }
-            buffer.cursor().skip().map_or(false, peek)
-        }
-
-        let _ = token;
-        peek2(self, T::Token::peek)
-    }
-
-    /// Looks at the third-next token in the parse stream.
-    pub fn peek3<T: Peek>(&self, token: T) -> bool {
-        fn peek3(buffer: &ParseBuffer, peek: fn(Cursor) -> bool) -> bool {
-            if let Some(group) = buffer.cursor().group(Delimiter::None) {
-                if group.0.skip().and_then(Cursor::skip).map_or(false, peek) {
-                    return true;
-                }
-            }
-            buffer
-                .cursor()
-                .skip()
-                .and_then(Cursor::skip)
-                .map_or(false, peek)
-        }
-
-        let _ = token;
-        peek3(self, T::Token::peek)
-    }
-
-    /// Parses zero or more occurrences of `T` separated by punctuation of type
-    /// `P`, with optional trailing punctuation.
-    ///
-    /// Parsing continues until the end of this parse stream. The entire content
-    /// of this parse stream must consist of `T` and `P`.
-    ///
-    /// # Example
-    ///
-    /// ```
-    /// # use quote::quote;
-    /// #
-    /// use syn::{parenthesized, token, Ident, Result, Token, Type};
-    /// use syn::parse::{Parse, ParseStream};
-    /// use syn::punctuated::Punctuated;
-    ///
-    /// // Parse a simplified tuple struct syntax like:
-    /// //
-    /// //     struct S(A, B);
-    /// struct TupleStruct {
-    ///     struct_token: Token![struct],
-    ///     ident: Ident,
-    ///     paren_token: token::Paren,
-    ///     fields: Punctuated<Type, Token![,]>,
-    ///     semi_token: Token![;],
-    /// }
-    ///
-    /// impl Parse for TupleStruct {
-    ///     fn parse(input: ParseStream) -> Result<Self> {
-    ///         let content;
-    ///         Ok(TupleStruct {
-    ///             struct_token: input.parse()?,
-    ///             ident: input.parse()?,
-    ///             paren_token: parenthesized!(content in input),
-    ///             fields: content.parse_terminated(Type::parse, Token![,])?,
-    ///             semi_token: input.parse()?,
-    ///         })
-    ///     }
-    /// }
-    /// #
-    /// # let input = quote! {
-    /// #     struct S(A, B);
-    /// # };
-    /// # syn::parse2::<TupleStruct>(input).unwrap();
-    /// ```
-    ///
-    /// # See also
-    ///
-    /// If your separator is anything more complicated than an invocation of the
-    /// `Token!` macro, this method won't be applicable and you can instead
-    /// directly use `Punctuated`'s parser functions: [`parse_terminated`],
-    /// [`parse_separated_nonempty`] etc.
-    ///
-    /// [`parse_terminated`]: Punctuated::parse_terminated
-    /// [`parse_separated_nonempty`]: Punctuated::parse_separated_nonempty
-    ///
-    /// ```
-    /// use syn::{custom_keyword, Expr, Result, Token};
-    /// use syn::parse::{Parse, ParseStream};
-    /// use syn::punctuated::Punctuated;
-    ///
-    /// mod kw {
-    ///     syn::custom_keyword!(fin);
-    /// }
-    ///
-    /// struct Fin(kw::fin, Token![;]);
-    ///
-    /// impl Parse for Fin {
-    ///     fn parse(input: ParseStream) -> Result<Self> {
-    ///         Ok(Self(input.parse()?, input.parse()?))
-    ///     }
-    /// }
-    ///
-    /// struct Thing {
-    ///     steps: Punctuated<Expr, Fin>,
-    /// }
-    ///
-    /// impl Parse for Thing {
-    ///     fn parse(input: ParseStream) -> Result<Self> {
-    /// # if true {
-    ///         Ok(Thing {
-    ///             steps: Punctuated::parse_terminated(input)?,
-    ///         })
-    /// # } else {
-    ///         // or equivalently, this means the same thing:
-    /// #       Ok(Thing {
-    ///             steps: input.call(Punctuated::parse_terminated)?,
-    /// #       })
-    /// # }
-    ///     }
-    /// }
-    /// ```
-    pub fn parse_terminated<T, P>(
-        &self,
-        parser: fn(ParseStream) -> Result<T>,
-        separator: P,
-    ) -> Result<Punctuated<T, P::Token>>
-    where
-        P: Peek,
-        P::Token: Parse,
-    {
-        let _ = separator;
-        Punctuated::parse_terminated_with(self, parser)
-    }
-
-    /// Returns whether there are tokens remaining in this stream.
-    ///
-    /// This method returns true at the end of the content of a set of
-    /// delimiters, as well as at the very end of the complete macro input.
-    ///
-    /// # Example
-    ///
-    /// ```
-    /// use syn::{braced, token, Ident, Item, Result, Token};
-    /// use syn::parse::{Parse, ParseStream};
-    ///
-    /// // Parses a Rust `mod m { ... }` containing zero or more items.
-    /// struct Mod {
-    ///     mod_token: Token![mod],
-    ///     name: Ident,
-    ///     brace_token: token::Brace,
-    ///     items: Vec<Item>,
-    /// }
-    ///
-    /// impl Parse for Mod {
-    ///     fn parse(input: ParseStream) -> Result<Self> {
-    ///         let content;
-    ///         Ok(Mod {
-    ///             mod_token: input.parse()?,
-    ///             name: input.parse()?,
-    ///             brace_token: braced!(content in input),
-    ///             items: {
-    ///                 let mut items = Vec::new();
-    ///                 while !content.is_empty() {
-    ///                     items.push(content.parse()?);
-    ///                 }
-    ///                 items
-    ///             },
-    ///         })
-    ///     }
-    /// }
-    /// ```
-    pub fn is_empty(&self) -> bool {
-        self.cursor().eof()
-    }
-
-    /// Constructs a helper for peeking at the next token in this stream and
-    /// building an error message if it is not one of a set of expected tokens.
-    ///
-    /// # Example
-    ///
-    /// ```
-    /// use syn::{ConstParam, Ident, Lifetime, LifetimeParam, Result, Token, TypeParam};
-    /// use syn::parse::{Parse, ParseStream};
-    ///
-    /// // A generic parameter, a single one of the comma-separated elements inside
-    /// // angle brackets in:
-    /// //
-    /// //     fn f<T: Clone, 'a, 'b: 'a, const N: usize>() { ... }
-    /// //
-    /// // On invalid input, lookahead gives us a reasonable error message.
-    /// //
-    /// //     error: expected one of: identifier, lifetime, `const`
-    /// //       |
-    /// //     5 |     fn f<!Sized>() {}
-    /// //       |          ^
-    /// enum GenericParam {
-    ///     Type(TypeParam),
-    ///     Lifetime(LifetimeParam),
-    ///     Const(ConstParam),
-    /// }
-    ///
-    /// impl Parse for GenericParam {
-    ///     fn parse(input: ParseStream) -> Result<Self> {
-    ///         let lookahead = input.lookahead1();
-    ///         if lookahead.peek(Ident) {
-    ///             input.parse().map(GenericParam::Type)
-    ///         } else if lookahead.peek(Lifetime) {
-    ///             input.parse().map(GenericParam::Lifetime)
-    ///         } else if lookahead.peek(Token![const]) {
-    ///             input.parse().map(GenericParam::Const)
-    ///         } else {
-    ///             Err(lookahead.error())
-    ///         }
-    ///     }
-    /// }
-    /// ```
-    pub fn lookahead1(&self) -> Lookahead1<'a> {
-        lookahead::new(self.scope, self.cursor())
-    }
-
-    /// Forks a parse stream so that parsing tokens out of either the original
-    /// or the fork does not advance the position of the other.
-    ///
-    /// # Performance
-    ///
-    /// Forking a parse stream is a cheap fixed amount of work and does not
-    /// involve copying token buffers. Where you might hit performance problems
-    /// is if your macro ends up parsing a large amount of content more than
-    /// once.
-    ///
-    /// ```
-    /// # use syn::{Expr, Result};
-    /// # use syn::parse::ParseStream;
-    /// #
-    /// # fn bad(input: ParseStream) -> Result<Expr> {
-    /// // Do not do this.
-    /// if input.fork().parse::<Expr>().is_ok() {
-    ///     return input.parse::<Expr>();
-    /// }
-    /// # unimplemented!()
-    /// # }
-    /// ```
-    ///
-    /// As a rule, avoid parsing an unbounded amount of tokens out of a forked
-    /// parse stream. Only use a fork when the amount of work performed against
-    /// the fork is small and bounded.
-    ///
-    /// When complex speculative parsing against the forked stream is
-    /// unavoidable, use [`parse::discouraged::Speculative`] to advance the
-    /// original stream once the fork's parse is determined to have been
-    /// successful.
-    ///
-    /// For a lower level way to perform speculative parsing at the token level,
-    /// consider using [`ParseStream::step`] instead.
-    ///
-    /// [`parse::discouraged::Speculative`]: discouraged::Speculative
-    /// [`ParseStream::step`]: ParseBuffer::step
-    ///
-    /// # Example
-    ///
-    /// The parse implementation shown here parses possibly restricted `pub`
-    /// visibilities.
-    ///
-    /// - `pub`
-    /// - `pub(crate)`
-    /// - `pub(self)`
-    /// - `pub(super)`
-    /// - `pub(in some::path)`
-    ///
-    /// To handle the case of visibilities inside of tuple structs, the parser
-    /// needs to distinguish parentheses that specify visibility restrictions
-    /// from parentheses that form part of a tuple type.
-    ///
-    /// ```
-    /// # struct A;
-    /// # struct B;
-    /// # struct C;
-    /// #
-    /// struct S(pub(crate) A, pub (B, C));
-    /// ```
-    ///
-    /// In this example input the first tuple struct element of `S` has
-    /// `pub(crate)` visibility while the second tuple struct element has `pub`
-    /// visibility; the parentheses around `(B, C)` are part of the type rather
-    /// than part of a visibility restriction.
-    ///
-    /// The parser uses a forked parse stream to check the first token inside of
-    /// parentheses after the `pub` keyword. This is a small bounded amount of
-    /// work performed against the forked parse stream.
-    ///
-    /// ```
-    /// use syn::{parenthesized, token, Ident, Path, Result, Token};
-    /// use syn::ext::IdentExt;
-    /// use syn::parse::{Parse, ParseStream};
-    ///
-    /// struct PubVisibility {
-    ///     pub_token: Token![pub],
-    ///     restricted: Option<Restricted>,
-    /// }
-    ///
-    /// struct Restricted {
-    ///     paren_token: token::Paren,
-    ///     in_token: Option<Token![in]>,
-    ///     path: Path,
-    /// }
-    ///
-    /// impl Parse for PubVisibility {
-    ///     fn parse(input: ParseStream) -> Result<Self> {
-    ///         let pub_token: Token![pub] = input.parse()?;
-    ///
-    ///         if input.peek(token::Paren) {
-    ///             let ahead = input.fork();
-    ///             let mut content;
-    ///             parenthesized!(content in ahead);
-    ///
-    ///             if content.peek(Token![crate])
-    ///                 || content.peek(Token![self])
-    ///                 || content.peek(Token![super])
-    ///             {
-    ///                 return Ok(PubVisibility {
-    ///                     pub_token,
-    ///                     restricted: Some(Restricted {
-    ///                         paren_token: parenthesized!(content in input),
-    ///                         in_token: None,
-    ///                         path: Path::from(content.call(Ident::parse_any)?),
-    ///                     }),
-    ///                 });
-    ///             } else if content.peek(Token![in]) {
-    ///                 return Ok(PubVisibility {
-    ///                     pub_token,
-    ///                     restricted: Some(Restricted {
-    ///                         paren_token: parenthesized!(content in input),
-    ///                         in_token: Some(content.parse()?),
-    ///                         path: content.call(Path::parse_mod_style)?,
-    ///                     }),
-    ///                 });
-    ///             }
-    ///         }
-    ///
-    ///         Ok(PubVisibility {
-    ///             pub_token,
-    ///             restricted: None,
-    ///         })
-    ///     }
-    /// }
-    /// ```
-    pub fn fork(&self) -> Self {
-        ParseBuffer {
-            scope: self.scope,
-            cell: self.cell.clone(),
-            marker: PhantomData,
-            // Not the parent's unexpected. Nothing cares whether the clone
-            // parses all the way unless we `advance_to`.
-            unexpected: Cell::new(Some(Rc::new(Cell::new(Unexpected::None)))),
-        }
-    }
-
-    /// Triggers an error at the current position of the parse stream.
-    ///
-    /// # Example
-    ///
-    /// ```
-    /// use syn::{Expr, Result, Token};
-    /// use syn::parse::{Parse, ParseStream};
-    ///
-    /// // Some kind of loop: `while` or `for` or `loop`.
-    /// struct Loop {
-    ///     expr: Expr,
-    /// }
-    ///
-    /// impl Parse for Loop {
-    ///     fn parse(input: ParseStream) -> Result<Self> {
-    ///         if input.peek(Token![while])
-    ///             || input.peek(Token![for])
-    ///             || input.peek(Token![loop])
-    ///         {
-    ///             Ok(Loop {
-    ///                 expr: input.parse()?,
-    ///             })
-    ///         } else {
-    ///             Err(input.error("expected some kind of loop"))
-    ///         }
-    ///     }
-    /// }
-    /// ```
-    pub fn error<T: Display>(&self, message: T) -> Error {
-        error::new_at(self.scope, self.cursor(), message)
-    }
-
-    /// Speculatively parses tokens from this parse stream, advancing the
-    /// position of this stream only if parsing succeeds.
-    ///
-    /// This is a powerful low-level API used for defining the `Parse` impls of
-    /// the basic built-in token types. It is not something that will be used
-    /// widely outside of the Syn codebase.
-    ///
-    /// # Example
-    ///
-    /// ```
-    /// use proc_macro2::TokenTree;
-    /// use syn::Result;
-    /// use syn::parse::ParseStream;
-    ///
-    /// // This function advances the stream past the next occurrence of `@`. If
-    /// // no `@` is present in the stream, the stream position is unchanged and
-    /// // an error is returned.
-    /// fn skip_past_next_at(input: ParseStream) -> Result<()> {
-    ///     input.step(|cursor| {
-    ///         let mut rest = *cursor;
-    ///         while let Some((tt, next)) = rest.token_tree() {
-    ///             match &tt {
-    ///                 TokenTree::Punct(punct) if punct.as_char() == '@' => {
-    ///                     return Ok(((), next));
-    ///                 }
-    ///                 _ => rest = next,
-    ///             }
-    ///         }
-    ///         Err(cursor.error("no `@` was found after this point"))
-    ///     })
-    /// }
-    /// #
-    /// # fn remainder_after_skipping_past_next_at(
-    /// #     input: ParseStream,
-    /// # ) -> Result<proc_macro2::TokenStream> {
-    /// #     skip_past_next_at(input)?;
-    /// #     input.parse()
-    /// # }
-    /// #
-    /// # use syn::parse::Parser;
-    /// # let remainder = remainder_after_skipping_past_next_at
-    /// #     .parse_str("a @ b c")
-    /// #     .unwrap();
-    /// # assert_eq!(remainder.to_string(), "b c");
-    /// ```
-    pub fn step<F, R>(&self, function: F) -> Result<R>
-    where
-        F: for<'c> FnOnce(StepCursor<'c, 'a>) -> Result<(R, Cursor<'c>)>,
-    {
-        // Since the user's function is required to work for any 'c, we know
-        // that the Cursor<'c> they return is either derived from the input
-        // StepCursor<'c, 'a> or from a Cursor<'static>.
-        //
-        // It would not be legal to write this function without the invariant
-        // lifetime 'c in StepCursor<'c, 'a>. If this function were written only
-        // in terms of 'a, the user could take our ParseBuffer<'a>, upcast it to
-        // a ParseBuffer<'short> which some shorter lifetime than 'a, invoke
-        // `step` on their ParseBuffer<'short> with a closure that returns
-        // Cursor<'short>, and we would wrongly write that Cursor<'short> into
-        // the Cell intended to hold Cursor<'a>.
-        //
-        // In some cases it may be necessary for R to contain a Cursor<'a>.
-        // Within Syn we solve this using `advance_step_cursor` which uses the
-        // existence of a StepCursor<'c, 'a> as proof that it is safe to cast
-        // from Cursor<'c> to Cursor<'a>. If needed outside of Syn, it would be
-        // safe to expose that API as a method on StepCursor.
-        let (node, rest) = function(StepCursor {
-            scope: self.scope,
-            cursor: self.cell.get(),
-            marker: PhantomData,
-        })?;
-        self.cell.set(rest);
-        Ok(node)
-    }
-
-    /// Returns the `Span` of the next token in the parse stream, or
-    /// `Span::call_site()` if this parse stream has completely exhausted its
-    /// input `TokenStream`.
-    pub fn span(&self) -> Span {
-        let cursor = self.cursor();
-        if cursor.eof() {
-            self.scope
-        } else {
-            crate::buffer::open_span_of_group(cursor)
-        }
-    }
-
-    /// Provides low-level access to the token representation underlying this
-    /// parse stream.
-    ///
-    /// Cursors are immutable so no operations you perform against the cursor
-    /// will affect the state of this parse stream.
-    ///
-    /// # Example
-    ///
-    /// ```
-    /// use proc_macro2::TokenStream;
-    /// use syn::buffer::Cursor;
-    /// use syn::parse::{ParseStream, Result};
-    ///
-    /// // Run a parser that returns T, but get its output as TokenStream instead of T.
-    /// // This works without T needing to implement ToTokens.
-    /// fn recognize_token_stream<T>(
-    ///     recognizer: fn(ParseStream) -> Result<T>,
-    /// ) -> impl Fn(ParseStream) -> Result<TokenStream> {
-    ///     move |input| {
-    ///         let begin = input.cursor();
-    ///         recognizer(input)?;
-    ///         let end = input.cursor();
-    ///         Ok(tokens_between(begin, end))
-    ///     }
-    /// }
-    ///
-    /// // Collect tokens between two cursors as a TokenStream.
-    /// fn tokens_between(begin: Cursor, end: Cursor) -> TokenStream {
-    ///     assert!(begin <= end);
-    ///
-    ///     let mut cursor = begin;
-    ///     let mut tokens = TokenStream::new();
-    ///     while cursor < end {
-    ///         let (token, next) = cursor.token_tree().unwrap();
-    ///         tokens.extend(std::iter::once(token));
-    ///         cursor = next;
-    ///     }
-    ///     tokens
-    /// }
-    ///
-    /// fn main() {
-    ///     use quote::quote;
-    ///     use syn::parse::{Parse, Parser};
-    ///     use syn::Token;
-    ///
-    ///     // Parse syn::Type as a TokenStream, surrounded by angle brackets.
-    ///     fn example(input: ParseStream) -> Result<TokenStream> {
-    ///         let _langle: Token![<] = input.parse()?;
-    ///         let ty = recognize_token_stream(syn::Type::parse)(input)?;
-    ///         let _rangle: Token![>] = input.parse()?;
-    ///         Ok(ty)
-    ///     }
-    ///
-    ///     let tokens = quote! { <fn() -> u8> };
-    ///     println!("{}", example.parse2(tokens).unwrap());
-    /// }
-    /// ```
-    pub fn cursor(&self) -> Cursor<'a> {
-        self.cell.get()
-    }
-
-    fn check_unexpected(&self) -> Result<()> {
-        match inner_unexpected(self).1 {
-            Some(span) => Err(Error::new(span, "unexpected token")),
-            None => Ok(()),
-        }
-    }
-}
-
-#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
-impl<T: Parse> Parse for Box<T> {
-    fn parse(input: ParseStream) -> Result<Self> {
-        input.parse().map(Box::new)
-    }
-}
-
-#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
-impl<T: Parse + Token> Parse for Option<T> {
-    fn parse(input: ParseStream) -> Result<Self> {
-        if T::peek(input.cursor()) {
-            Ok(Some(input.parse()?))
-        } else {
-            Ok(None)
-        }
-    }
-}
-
-#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
-impl Parse for TokenStream {
-    fn parse(input: ParseStream) -> Result<Self> {
-        input.step(|cursor| Ok((cursor.token_stream(), Cursor::empty())))
-    }
-}
-
-#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
-impl Parse for TokenTree {
-    fn parse(input: ParseStream) -> Result<Self> {
-        input.step(|cursor| match cursor.token_tree() {
-            Some((tt, rest)) => Ok((tt, rest)),
-            None => Err(cursor.error("expected token tree")),
-        })
-    }
-}
-
-#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
-impl Parse for Group {
-    fn parse(input: ParseStream) -> Result<Self> {
-        input.step(|cursor| {
-            if let Some((group, rest)) = cursor.any_group_token() {
-                if group.delimiter() != Delimiter::None {
-                    return Ok((group, rest));
-                }
-            }
-            Err(cursor.error("expected group token"))
-        })
-    }
-}
-
-#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
-impl Parse for Punct {
-    fn parse(input: ParseStream) -> Result<Self> {
-        input.step(|cursor| match cursor.punct() {
-            Some((punct, rest)) => Ok((punct, rest)),
-            None => Err(cursor.error("expected punctuation token")),
-        })
-    }
-}
-
-#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
-impl Parse for Literal {
-    fn parse(input: ParseStream) -> Result<Self> {
-        input.step(|cursor| match cursor.literal() {
-            Some((literal, rest)) => Ok((literal, rest)),
-            None => Err(cursor.error("expected literal token")),
-        })
-    }
-}
-
-/// Parser that can parse Rust tokens into a particular syntax tree node.
-///
-/// Refer to the [module documentation] for details about parsing in Syn.
-///
-/// [module documentation]: self
-pub trait Parser: Sized {
-    type Output;
-
-    /// Parse a proc-macro2 token stream into the chosen syntax tree node.
-    ///
-    /// This function will check that the input is fully parsed. If there are
-    /// any unparsed tokens at the end of the stream, an error is returned.
-    fn parse2(self, tokens: TokenStream) -> Result<Self::Output>;
-
-    /// Parse tokens of source code into the chosen syntax tree node.
-    ///
-    /// This function will check that the input is fully parsed. If there are
-    /// any unparsed tokens at the end of the stream, an error is returned.
-    #[cfg(feature = "proc-macro")]
-    #[cfg_attr(doc_cfg, doc(cfg(feature = "proc-macro")))]
-    fn parse(self, tokens: proc_macro::TokenStream) -> Result<Self::Output> {
-        self.parse2(proc_macro2::TokenStream::from(tokens))
-    }
-
-    /// Parse a string of Rust code into the chosen syntax tree node.
-    ///
-    /// This function will check that the input is fully parsed. If there are
-    /// any unparsed tokens at the end of the string, an error is returned.
-    ///
-    /// # Hygiene
-    ///
-    /// Every span in the resulting syntax tree will be set to resolve at the
-    /// macro call site.
-    fn parse_str(self, s: &str) -> Result<Self::Output> {
-        self.parse2(proc_macro2::TokenStream::from_str(s)?)
-    }
-
-    // Not public API.
-    #[doc(hidden)]
-    #[cfg(any(feature = "full", feature = "derive"))]
-    fn __parse_scoped(self, scope: Span, tokens: TokenStream) -> Result<Self::Output> {
-        let _ = scope;
-        self.parse2(tokens)
-    }
-}
-
-fn tokens_to_parse_buffer(tokens: &TokenBuffer) -> ParseBuffer {
-    let scope = Span::call_site();
-    let cursor = tokens.begin();
-    let unexpected = Rc::new(Cell::new(Unexpected::None));
-    new_parse_buffer(scope, cursor, unexpected)
-}
-
-impl<F, T> Parser for F
-where
-    F: FnOnce(ParseStream) -> Result<T>,
-{
-    type Output = T;
-
-    fn parse2(self, tokens: TokenStream) -> Result<T> {
-        let buf = TokenBuffer::new2(tokens);
-        let state = tokens_to_parse_buffer(&buf);
-        let node = self(&state)?;
-        state.check_unexpected()?;
-        if let Some(unexpected_span) = span_of_unexpected_ignoring_nones(state.cursor()) {
-            Err(Error::new(unexpected_span, "unexpected token"))
-        } else {
-            Ok(node)
-        }
-    }
-
-    #[cfg(any(feature = "full", feature = "derive"))]
-    fn __parse_scoped(self, scope: Span, tokens: TokenStream) -> Result<Self::Output> {
-        let buf = TokenBuffer::new2(tokens);
-        let cursor = buf.begin();
-        let unexpected = Rc::new(Cell::new(Unexpected::None));
-        let state = new_parse_buffer(scope, cursor, unexpected);
-        let node = self(&state)?;
-        state.check_unexpected()?;
-        if let Some(unexpected_span) = span_of_unexpected_ignoring_nones(state.cursor()) {
-            Err(Error::new(unexpected_span, "unexpected token"))
-        } else {
-            Ok(node)
-        }
-    }
-}
-
-#[cfg(any(feature = "full", feature = "derive"))]
-pub(crate) fn parse_scoped<F: Parser>(f: F, scope: Span, tokens: TokenStream) -> Result<F::Output> {
-    f.__parse_scoped(scope, tokens)
-}
-
-/// An empty syntax tree node that consumes no tokens when parsed.
-///
-/// This is useful for attribute macros that want to ensure they are not
-/// provided any attribute args.
-///
-/// ```
-/// # extern crate proc_macro;
-/// #
-/// use proc_macro::TokenStream;
-/// use syn::parse_macro_input;
-/// use syn::parse::Nothing;
-///
-/// # const IGNORE: &str = stringify! {
-/// #[proc_macro_attribute]
-/// # };
-/// pub fn my_attr(args: TokenStream, input: TokenStream) -> TokenStream {
-///     parse_macro_input!(args as Nothing);
-///
-///     /* ... */
-/// #   TokenStream::new()
-/// }
-/// ```
-///
-/// ```text
-/// error: unexpected token
-///  --> src/main.rs:3:19
-///   |
-/// 3 | #[my_attr(asdf)]
-///   |           ^^^^
-/// ```
-pub struct Nothing;
-
-impl Parse for Nothing {
-    fn parse(_input: ParseStream) -> Result<Self> {
-        Ok(Nothing)
-    }
-}
-
-#[cfg(feature = "extra-traits")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
-impl Debug for Nothing {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.write_str("Nothing")
-    }
-}
-
-#[cfg(feature = "extra-traits")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
-impl Eq for Nothing {}
-
-#[cfg(feature = "extra-traits")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
-impl PartialEq for Nothing {
-    fn eq(&self, _other: &Self) -> bool {
-        true
-    }
-}
-
-#[cfg(feature = "extra-traits")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
-impl Hash for Nothing {
-    fn hash<H: Hasher>(&self, _state: &mut H) {}
-}