Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

1 files changed, 776 insertions, 0 deletions

diff --git a/vendor/syn/src/attr.rs b/vendor/syn/src/attr.rs
new file mode 100644
index 0000000..b6c4675
--- /dev/null
+++ b/vendor/syn/src/attr.rs
@@ -0,0 +1,776 @@
+use super::*;
+use proc_macro2::TokenStream;
+use std::iter;
+use std::slice;
+
+#[cfg(feature = "parsing")]
+use crate::meta::{self, ParseNestedMeta};
+#[cfg(feature = "parsing")]
+use crate::parse::{Parse, ParseStream, Parser, Result};
+
+ast_struct! {
+    /// An attribute, like `#[repr(transparent)]`.
+    ///
+    /// <br>
+    ///
+    /// # Syntax
+    ///
+    /// Rust has six types of attributes.
+    ///
+    /// - Outer attributes like `#[repr(transparent)]`. These appear outside or
+    ///   in front of the item they describe.
+    ///
+    /// - Inner attributes like `#![feature(proc_macro)]`. These appear inside
+    ///   of the item they describe, usually a module.
+    ///
+    /// - Outer one-line doc comments like `/// Example`.
+    ///
+    /// - Inner one-line doc comments like `//! Please file an issue`.
+    ///
+    /// - Outer documentation blocks `/** Example */`.
+    ///
+    /// - Inner documentation blocks `/*! Please file an issue */`.
+    ///
+    /// The `style` field of type `AttrStyle` distinguishes whether an attribute
+    /// is outer or inner.
+    ///
+    /// Every attribute has a `path` that indicates the intended interpretation
+    /// of the rest of the attribute's contents. The path and the optional
+    /// additional contents are represented together in the `meta` field of the
+    /// attribute in three possible varieties:
+    ///
+    /// - Meta::Path &mdash; attributes whose information content conveys just a
+    ///   path, for example the `#[test]` attribute.
+    ///
+    /// - Meta::List &mdash; attributes that carry arbitrary tokens after the
+    ///   path, surrounded by a delimiter (parenthesis, bracket, or brace). For
+    ///   example `#[derive(Copy)]` or `#[precondition(x < 5)]`.
+    ///
+    /// - Meta::NameValue &mdash; attributes with an `=` sign after the path,
+    ///   followed by a Rust expression. For example `#[path =
+    ///   "sys/windows.rs"]`.
+    ///
+    /// All doc comments are represented in the NameValue style with a path of
+    /// "doc", as this is how they are processed by the compiler and by
+    /// `macro_rules!` macros.
+    ///
+    /// ```text
+    /// #[derive(Copy, Clone)]
+    ///   ~~~~~~Path
+    ///   ^^^^^^^^^^^^^^^^^^^Meta::List
+    ///
+    /// #[path = "sys/windows.rs"]
+    ///   ~~~~Path
+    ///   ^^^^^^^^^^^^^^^^^^^^^^^Meta::NameValue
+    ///
+    /// #[test]
+    ///   ^^^^Meta::Path
+    /// ```
+    ///
+    /// <br>
+    ///
+    /// # Parsing from tokens to Attribute
+    ///
+    /// This type does not implement the [`Parse`] trait and thus cannot be
+    /// parsed directly by [`ParseStream::parse`]. Instead use
+    /// [`ParseStream::call`] with one of the two parser functions
+    /// [`Attribute::parse_outer`] or [`Attribute::parse_inner`] depending on
+    /// which you intend to parse.
+    ///
+    /// [`Parse`]: parse::Parse
+    /// [`ParseStream::parse`]: parse::ParseBuffer::parse
+    /// [`ParseStream::call`]: parse::ParseBuffer::call
+    ///
+    /// ```
+    /// 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()?,
+    ///         })
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// <p><br></p>
+    ///
+    /// # Parsing from Attribute to structured arguments
+    ///
+    /// The grammar of attributes in Rust is very flexible, which makes the
+    /// syntax tree not that useful on its own. In particular, arguments of the
+    /// `Meta::List` variety of attribute are held in an arbitrary `tokens:
+    /// TokenStream`. Macros are expected to check the `path` of the attribute,
+    /// decide whether they recognize it, and then parse the remaining tokens
+    /// according to whatever grammar they wish to require for that kind of
+    /// attribute. Use [`parse_args()`] to parse those tokens into the expected
+    /// data structure.
+    ///
+    /// [`parse_args()`]: Attribute::parse_args
+    ///
+    /// <p><br></p>
+    ///
+    /// # Doc comments
+    ///
+    /// The compiler transforms doc comments, such as `/// comment` and `/*!
+    /// comment */`, into attributes before macros are expanded. Each comment is
+    /// expanded into an attribute of the form `#[doc = r"comment"]`.
+    ///
+    /// As an example, the following `mod` items are expanded identically:
+    ///
+    /// ```
+    /// # use syn::{ItemMod, parse_quote};
+    /// let doc: ItemMod = parse_quote! {
+    ///     /// Single line doc comments
+    ///     /// We write so many!
+    ///     /**
+    ///      * Multi-line comments...
+    ///      * May span many lines
+    ///      */
+    ///     mod example {
+    ///         //! Of course, they can be inner too
+    ///         /*! And fit in a single line */
+    ///     }
+    /// };
+    /// let attr: ItemMod = parse_quote! {
+    ///     #[doc = r" Single line doc comments"]
+    ///     #[doc = r" We write so many!"]
+    ///     #[doc = r"
+    ///      * Multi-line comments...
+    ///      * May span many lines
+    ///      "]
+    ///     mod example {
+    ///         #![doc = r" Of course, they can be inner too"]
+    ///         #![doc = r" And fit in a single line "]
+    ///     }
+    /// };
+    /// assert_eq!(doc, attr);
+    /// ```
+    #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
+    pub struct Attribute {
+        pub pound_token: Token![#],
+        pub style: AttrStyle,
+        pub bracket_token: token::Bracket,
+        pub meta: Meta,
+    }
+}
+
+impl Attribute {
+    /// Returns the path that identifies the interpretation of this attribute.
+    ///
+    /// For example this would return the `test` in `#[test]`, the `derive` in
+    /// `#[derive(Copy)]`, and the `path` in `#[path = "sys/windows.rs"]`.
+    pub fn path(&self) -> &Path {
+        self.meta.path()
+    }
+
+    /// Parse the arguments to the attribute as a syntax tree.
+    ///
+    /// This is similar to pulling out the `TokenStream` from `Meta::List` and
+    /// doing `syn::parse2::<T>(meta_list.tokens)`, except that using
+    /// `parse_args` the error message has a more useful span when `tokens` is
+    /// empty.
+    ///
+    /// The surrounding delimiters are *not* included in the input to the
+    /// parser.
+    ///
+    /// ```text
+    /// #[my_attr(value < 5)]
+    ///           ^^^^^^^^^ what gets parsed
+    /// ```
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use syn::{parse_quote, Attribute, Expr};
+    ///
+    /// let attr: Attribute = parse_quote! {
+    ///     #[precondition(value < 5)]
+    /// };
+    ///
+    /// if attr.path().is_ident("precondition") {
+    ///     let precondition: Expr = attr.parse_args()?;
+    ///     // ...
+    /// }
+    /// # anyhow::Ok(())
+    /// ```
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn parse_args<T: Parse>(&self) -> Result<T> {
+        self.parse_args_with(T::parse)
+    }
+
+    /// Parse the arguments to the attribute using the given parser.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use syn::{parse_quote, Attribute};
+    ///
+    /// let attr: Attribute = parse_quote! {
+    ///     #[inception { #[brrrrrrraaaaawwwwrwrrrmrmrmmrmrmmmmm] }]
+    /// };
+    ///
+    /// let bwom = attr.parse_args_with(Attribute::parse_outer)?;
+    ///
+    /// // Attribute does not have a Parse impl, so we couldn't directly do:
+    /// // let bwom: Attribute = attr.parse_args()?;
+    /// # anyhow::Ok(())
+    /// ```
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn parse_args_with<F: Parser>(&self, parser: F) -> Result<F::Output> {
+        match &self.meta {
+            Meta::Path(path) => Err(crate::error::new2(
+                path.segments.first().unwrap().ident.span(),
+                path.segments.last().unwrap().ident.span(),
+                format!(
+                    "expected attribute arguments in parentheses: {}[{}(...)]",
+                    parsing::DisplayAttrStyle(&self.style),
+                    parsing::DisplayPath(path),
+                ),
+            )),
+            Meta::NameValue(meta) => Err(Error::new(
+                meta.eq_token.span,
+                format_args!(
+                    "expected parentheses: {}[{}(...)]",
+                    parsing::DisplayAttrStyle(&self.style),
+                    parsing::DisplayPath(&meta.path),
+                ),
+            )),
+            Meta::List(meta) => meta.parse_args_with(parser),
+        }
+    }
+
+    /// Parse the arguments to the attribute, expecting it to follow the
+    /// conventional structure used by most of Rust's built-in attributes.
+    ///
+    /// The [*Meta Item Attribute Syntax*][syntax] section in the Rust reference
+    /// explains the convention in more detail. Not all attributes follow this
+    /// convention, so [`parse_args()`][Self::parse_args] is available if you
+    /// need to parse arbitrarily goofy attribute syntax.
+    ///
+    /// [syntax]: https://doc.rust-lang.org/reference/attributes.html#meta-item-attribute-syntax
+    ///
+    /// # Example
+    ///
+    /// We'll parse a struct, and then parse some of Rust's `#[repr]` attribute
+    /// syntax.
+    ///
+    /// ```
+    /// use syn::{parenthesized, parse_quote, token, ItemStruct, LitInt};
+    ///
+    /// let input: ItemStruct = parse_quote! {
+    ///     #[repr(C, align(4))]
+    ///     pub struct MyStruct(u16, u32);
+    /// };
+    ///
+    /// let mut repr_c = false;
+    /// let mut repr_transparent = false;
+    /// let mut repr_align = None::<usize>;
+    /// let mut repr_packed = None::<usize>;
+    /// for attr in &input.attrs {
+    ///     if attr.path().is_ident("repr") {
+    ///         attr.parse_nested_meta(|meta| {
+    ///             // #[repr(C)]
+    ///             if meta.path.is_ident("C") {
+    ///                 repr_c = true;
+    ///                 return Ok(());
+    ///             }
+    ///
+    ///             // #[repr(transparent)]
+    ///             if meta.path.is_ident("transparent") {
+    ///                 repr_transparent = true;
+    ///                 return Ok(());
+    ///             }
+    ///
+    ///             // #[repr(align(N))]
+    ///             if meta.path.is_ident("align") {
+    ///                 let content;
+    ///                 parenthesized!(content in meta.input);
+    ///                 let lit: LitInt = content.parse()?;
+    ///                 let n: usize = lit.base10_parse()?;
+    ///                 repr_align = Some(n);
+    ///                 return Ok(());
+    ///             }
+    ///
+    ///             // #[repr(packed)] or #[repr(packed(N))], omitted N means 1
+    ///             if meta.path.is_ident("packed") {
+    ///                 if meta.input.peek(token::Paren) {
+    ///                     let content;
+    ///                     parenthesized!(content in meta.input);
+    ///                     let lit: LitInt = content.parse()?;
+    ///                     let n: usize = lit.base10_parse()?;
+    ///                     repr_packed = Some(n);
+    ///                 } else {
+    ///                     repr_packed = Some(1);
+    ///                 }
+    ///                 return Ok(());
+    ///             }
+    ///
+    ///             Err(meta.error("unrecognized repr"))
+    ///         })?;
+    ///     }
+    /// }
+    /// # anyhow::Ok(())
+    /// ```
+    ///
+    /// # Alternatives
+    ///
+    /// In some cases, for attributes which have nested layers of structured
+    /// content, the following less flexible approach might be more convenient:
+    ///
+    /// ```
+    /// # use syn::{parse_quote, ItemStruct};
+    /// #
+    /// # let input: ItemStruct = parse_quote! {
+    /// #     #[repr(C, align(4))]
+    /// #     pub struct MyStruct(u16, u32);
+    /// # };
+    /// #
+    /// use syn::punctuated::Punctuated;
+    /// use syn::{parenthesized, token, Error, LitInt, Meta, Token};
+    ///
+    /// let mut repr_c = false;
+    /// let mut repr_transparent = false;
+    /// let mut repr_align = None::<usize>;
+    /// let mut repr_packed = None::<usize>;
+    /// for attr in &input.attrs {
+    ///     if attr.path().is_ident("repr") {
+    ///         let nested = attr.parse_args_with(Punctuated::<Meta, Token![,]>::parse_terminated)?;
+    ///         for meta in nested {
+    ///             match meta {
+    ///                 // #[repr(C)]
+    ///                 Meta::Path(path) if path.is_ident("C") => {
+    ///                     repr_c = true;
+    ///                 }
+    ///
+    ///                 // #[repr(align(N))]
+    ///                 Meta::List(meta) if meta.path.is_ident("align") => {
+    ///                     let lit: LitInt = meta.parse_args()?;
+    ///                     let n: usize = lit.base10_parse()?;
+    ///                     repr_align = Some(n);
+    ///                 }
+    ///
+    ///                 /* ... */
+    ///
+    ///                 _ => {
+    ///                     return Err(Error::new_spanned(meta, "unrecognized repr"));
+    ///                 }
+    ///             }
+    ///         }
+    ///     }
+    /// }
+    /// # Ok(())
+    /// ```
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn parse_nested_meta(
+        &self,
+        logic: impl FnMut(ParseNestedMeta) -> Result<()>,
+    ) -> Result<()> {
+        self.parse_args_with(meta::parser(logic))
+    }
+
+    /// Parses zero or more outer attributes from the stream.
+    ///
+    /// # Example
+    ///
+    /// See
+    /// [*Parsing from tokens to Attribute*](#parsing-from-tokens-to-attribute).
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn parse_outer(input: ParseStream) -> Result<Vec<Self>> {
+        let mut attrs = Vec::new();
+        while input.peek(Token![#]) {
+            attrs.push(input.call(parsing::single_parse_outer)?);
+        }
+        Ok(attrs)
+    }
+
+    /// Parses zero or more inner attributes from the stream.
+    ///
+    /// # Example
+    ///
+    /// See
+    /// [*Parsing from tokens to Attribute*](#parsing-from-tokens-to-attribute).
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn parse_inner(input: ParseStream) -> Result<Vec<Self>> {
+        let mut attrs = Vec::new();
+        parsing::parse_inner(input, &mut attrs)?;
+        Ok(attrs)
+    }
+}
+
+ast_enum! {
+    /// Distinguishes between attributes that decorate an item and attributes
+    /// that are contained within an item.
+    ///
+    /// # Outer attributes
+    ///
+    /// - `#[repr(transparent)]`
+    /// - `/// # Example`
+    /// - `/** Please file an issue */`
+    ///
+    /// # Inner attributes
+    ///
+    /// - `#![feature(proc_macro)]`
+    /// - `//! # Example`
+    /// - `/*! Please file an issue */`
+    #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
+    pub enum AttrStyle {
+        Outer,
+        Inner(Token![!]),
+    }
+}
+
+ast_enum_of_structs! {
+    /// Content of a compile-time structured attribute.
+    ///
+    /// ## Path
+    ///
+    /// A meta path is like the `test` in `#[test]`.
+    ///
+    /// ## List
+    ///
+    /// A meta list is like the `derive(Copy)` in `#[derive(Copy)]`.
+    ///
+    /// ## NameValue
+    ///
+    /// A name-value meta is like the `path = "..."` in `#[path =
+    /// "sys/windows.rs"]`.
+    ///
+    /// # Syntax tree enum
+    ///
+    /// This type is a [syntax tree enum].
+    ///
+    /// [syntax tree enum]: Expr#syntax-tree-enums
+    #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
+    pub enum Meta {
+        Path(Path),
+
+        /// A structured list within an attribute, like `derive(Copy, Clone)`.
+        List(MetaList),
+
+        /// A name-value pair within an attribute, like `feature = "nightly"`.
+        NameValue(MetaNameValue),
+    }
+}
+
+ast_struct! {
+    /// A structured list within an attribute, like `derive(Copy, Clone)`.
+    #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
+    pub struct MetaList {
+        pub path: Path,
+        pub delimiter: MacroDelimiter,
+        pub tokens: TokenStream,
+    }
+}
+
+ast_struct! {
+    /// A name-value pair within an attribute, like `feature = "nightly"`.
+    #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
+    pub struct MetaNameValue {
+        pub path: Path,
+        pub eq_token: Token![=],
+        pub value: Expr,
+    }
+}
+
+impl Meta {
+    /// Returns the path that begins this structured meta item.
+    ///
+    /// For example this would return the `test` in `#[test]`, the `derive` in
+    /// `#[derive(Copy)]`, and the `path` in `#[path = "sys/windows.rs"]`.
+    pub fn path(&self) -> &Path {
+        match self {
+            Meta::Path(path) => path,
+            Meta::List(meta) => &meta.path,
+            Meta::NameValue(meta) => &meta.path,
+        }
+    }
+
+    /// Error if this is a `Meta::List` or `Meta::NameValue`.
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn require_path_only(&self) -> Result<&Path> {
+        let error_span = match self {
+            Meta::Path(path) => return Ok(path),
+            Meta::List(meta) => meta.delimiter.span().open(),
+            Meta::NameValue(meta) => meta.eq_token.span,
+        };
+        Err(Error::new(error_span, "unexpected token in attribute"))
+    }
+
+    /// Error if this is a `Meta::Path` or `Meta::NameValue`.
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn require_list(&self) -> Result<&MetaList> {
+        match self {
+            Meta::List(meta) => Ok(meta),
+            Meta::Path(path) => Err(crate::error::new2(
+                path.segments.first().unwrap().ident.span(),
+                path.segments.last().unwrap().ident.span(),
+                format!(
+                    "expected attribute arguments in parentheses: `{}(...)`",
+                    parsing::DisplayPath(path),
+                ),
+            )),
+            Meta::NameValue(meta) => Err(Error::new(meta.eq_token.span, "expected `(`")),
+        }
+    }
+
+    /// Error if this is a `Meta::Path` or `Meta::List`.
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn require_name_value(&self) -> Result<&MetaNameValue> {
+        match self {
+            Meta::NameValue(meta) => Ok(meta),
+            Meta::Path(path) => Err(crate::error::new2(
+                path.segments.first().unwrap().ident.span(),
+                path.segments.last().unwrap().ident.span(),
+                format!(
+                    "expected a value for this attribute: `{} = ...`",
+                    parsing::DisplayPath(path),
+                ),
+            )),
+            Meta::List(meta) => Err(Error::new(meta.delimiter.span().open(), "expected `=`")),
+        }
+    }
+}
+
+impl MetaList {
+    /// See [`Attribute::parse_args`].
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn parse_args<T: Parse>(&self) -> Result<T> {
+        self.parse_args_with(T::parse)
+    }
+
+    /// See [`Attribute::parse_args_with`].
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn parse_args_with<F: Parser>(&self, parser: F) -> Result<F::Output> {
+        let scope = self.delimiter.span().close();
+        crate::parse::parse_scoped(parser, scope, self.tokens.clone())
+    }
+
+    /// See [`Attribute::parse_nested_meta`].
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    pub fn parse_nested_meta(
+        &self,
+        logic: impl FnMut(ParseNestedMeta) -> Result<()>,
+    ) -> Result<()> {
+        self.parse_args_with(meta::parser(logic))
+    }
+}
+
+pub(crate) trait FilterAttrs<'a> {
+    type Ret: Iterator<Item = &'a Attribute>;
+
+    fn outer(self) -> Self::Ret;
+    fn inner(self) -> Self::Ret;
+}
+
+impl<'a> FilterAttrs<'a> for &'a [Attribute] {
+    type Ret = iter::Filter<slice::Iter<'a, Attribute>, fn(&&Attribute) -> bool>;
+
+    fn outer(self) -> Self::Ret {
+        fn is_outer(attr: &&Attribute) -> bool {
+            match attr.style {
+                AttrStyle::Outer => true,
+                AttrStyle::Inner(_) => false,
+            }
+        }
+        self.iter().filter(is_outer)
+    }
+
+    fn inner(self) -> Self::Ret {
+        fn is_inner(attr: &&Attribute) -> bool {
+            match attr.style {
+                AttrStyle::Inner(_) => true,
+                AttrStyle::Outer => false,
+            }
+        }
+        self.iter().filter(is_inner)
+    }
+}
+
+#[cfg(feature = "parsing")]
+pub(crate) mod parsing {
+    use super::*;
+    use crate::parse::discouraged::Speculative as _;
+    use crate::parse::{Parse, ParseStream, Result};
+    use std::fmt::{self, Display};
+
+    pub(crate) fn parse_inner(input: ParseStream, attrs: &mut Vec<Attribute>) -> Result<()> {
+        while input.peek(Token![#]) && input.peek2(Token![!]) {
+            attrs.push(input.call(parsing::single_parse_inner)?);
+        }
+        Ok(())
+    }
+
+    pub(crate) fn single_parse_inner(input: ParseStream) -> Result<Attribute> {
+        let content;
+        Ok(Attribute {
+            pound_token: input.parse()?,
+            style: AttrStyle::Inner(input.parse()?),
+            bracket_token: bracketed!(content in input),
+            meta: content.parse()?,
+        })
+    }
+
+    pub(crate) fn single_parse_outer(input: ParseStream) -> Result<Attribute> {
+        let content;
+        Ok(Attribute {
+            pound_token: input.parse()?,
+            style: AttrStyle::Outer,
+            bracket_token: bracketed!(content in input),
+            meta: content.parse()?,
+        })
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    impl Parse for Meta {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let path = input.call(Path::parse_mod_style)?;
+            parse_meta_after_path(path, input)
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    impl Parse for MetaList {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let path = input.call(Path::parse_mod_style)?;
+            parse_meta_list_after_path(path, input)
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    impl Parse for MetaNameValue {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let path = input.call(Path::parse_mod_style)?;
+            parse_meta_name_value_after_path(path, input)
+        }
+    }
+
+    pub(crate) fn parse_meta_after_path(path: Path, input: ParseStream) -> Result<Meta> {
+        if input.peek(token::Paren) || input.peek(token::Bracket) || input.peek(token::Brace) {
+            parse_meta_list_after_path(path, input).map(Meta::List)
+        } else if input.peek(Token![=]) {
+            parse_meta_name_value_after_path(path, input).map(Meta::NameValue)
+        } else {
+            Ok(Meta::Path(path))
+        }
+    }
+
+    fn parse_meta_list_after_path(path: Path, input: ParseStream) -> Result<MetaList> {
+        let (delimiter, tokens) = mac::parse_delimiter(input)?;
+        Ok(MetaList {
+            path,
+            delimiter,
+            tokens,
+        })
+    }
+
+    fn parse_meta_name_value_after_path(path: Path, input: ParseStream) -> Result<MetaNameValue> {
+        let eq_token: Token![=] = input.parse()?;
+        let ahead = input.fork();
+        let lit: Option<Lit> = ahead.parse()?;
+        let value = if let (Some(lit), true) = (lit, ahead.is_empty()) {
+            input.advance_to(&ahead);
+            Expr::Lit(ExprLit {
+                attrs: Vec::new(),
+                lit,
+            })
+        } else if input.peek(Token![#]) && input.peek2(token::Bracket) {
+            return Err(input.error("unexpected attribute inside of attribute"));
+        } else {
+            input.parse()?
+        };
+        Ok(MetaNameValue {
+            path,
+            eq_token,
+            value,
+        })
+    }
+
+    pub(super) struct DisplayAttrStyle<'a>(pub &'a AttrStyle);
+
+    impl<'a> Display for DisplayAttrStyle<'a> {
+        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+            formatter.write_str(match self.0 {
+                AttrStyle::Outer => "#",
+                AttrStyle::Inner(_) => "#!",
+            })
+        }
+    }
+
+    pub(super) struct DisplayPath<'a>(pub &'a Path);
+
+    impl<'a> Display for DisplayPath<'a> {
+        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+            for (i, segment) in self.0.segments.iter().enumerate() {
+                if i > 0 || self.0.leading_colon.is_some() {
+                    formatter.write_str("::")?;
+                }
+                write!(formatter, "{}", segment.ident)?;
+            }
+            Ok(())
+        }
+    }
+}
+
+#[cfg(feature = "printing")]
+mod printing {
+    use super::*;
+    use proc_macro2::TokenStream;
+    use quote::ToTokens;
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for Attribute {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.pound_token.to_tokens(tokens);
+            if let AttrStyle::Inner(b) = &self.style {
+                b.to_tokens(tokens);
+            }
+            self.bracket_token.surround(tokens, |tokens| {
+                self.meta.to_tokens(tokens);
+            });
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for MetaList {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.path.to_tokens(tokens);
+            self.delimiter.surround(tokens, self.tokens.clone());
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for MetaNameValue {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.path.to_tokens(tokens);
+            self.eq_token.to_tokens(tokens);
+            self.value.to_tokens(tokens);
+        }
+    }
+}