src/path.rs - platform/external/rust/crates/syn - Gitiles

 // Copyright 2018 Syn Developers
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.

 use super::*;
 use punctuated::Punctuated;

 ast_struct! {
     /// A path at which a named item is exported: `std::collections::HashMap`.
     ///
     /// *This type is available if Syn is built with the `"derive"` or `"full"`
     /// feature.*
     pub struct Path {
         pub leading_colon: Option<Token![::]>,
         pub segments: Punctuated<PathSegment, Token![::]>,
     }
 }

 impl Path {
     pub fn global(&self) -> bool {
         self.leading_colon.is_some()
     }
 }

 /// A helper for printing a self-type qualified path as tokens.
 ///
 /// ```rust
 /// extern crate syn;
 /// extern crate quote;
 /// extern crate proc_macro2;
 ///
 /// use syn::{QSelf, Path, PathTokens};
 /// use proc_macro2::TokenStream;
 /// use quote::ToTokens;
 ///
 /// struct MyNode {
 ///     qself: Option<QSelf>,
 ///     path: Path,
 /// }
 ///
 /// impl ToTokens for MyNode {
 ///     fn to_tokens(&self, tokens: &mut TokenStream) {
 ///         PathTokens(&self.qself, &self.path).to_tokens(tokens);
 ///     }
 /// }
 /// #
 /// # fn main() {}
 /// ```
 ///
 /// *This type is available if Syn is built with the `"derive"` or `"full"`
 /// feature and the `"printing"` feature.*
 #[cfg(feature = "printing")]
 #[cfg_attr(feature = "extra-traits", derive(Debug, Eq, PartialEq, Hash))]
 #[cfg_attr(feature = "clone-impls", derive(Clone))]
 pub struct PathTokens<'a>(pub &'a Option<QSelf>, pub &'a Path);

 impl<T> From<T> for Path
 where
     T: Into<PathSegment>,
 {
     fn from(segment: T) -> Self {
         let mut path = Path {
             leading_colon: None,
             segments: Punctuated::new(),
         };
         path.segments.push_value(segment.into());
         path
     }
 }

 ast_struct! {
     /// A segment of a path together with any path arguments on that segment.
     ///
     /// *This type is available if Syn is built with the `"derive"` or `"full"`
     /// feature.*
     pub struct PathSegment {
         pub ident: Ident,
         pub arguments: PathArguments,
     }
 }

 impl<T> From<T> for PathSegment
 where
     T: Into<Ident>,
 {
     fn from(ident: T) -> Self {
         PathSegment {
             ident: ident.into(),
             arguments: PathArguments::None,
         }
     }
 }

 ast_enum! {
     /// Angle bracketed or parenthesized arguments of a path segment.
     ///
     /// *This type is available if Syn is built with the `"derive"` or `"full"`
     /// feature.*
     ///
     /// ## Angle bracketed
     ///
     /// The `<'a, T>` in `std::slice::iter<'a, T>`.
     ///
     /// ## Parenthesized
     ///
     /// The `(A, B) -> C` in `Fn(A, B) -> C`.
     pub enum PathArguments {
         None,
         /// The `<'a, T>` in `std::slice::iter<'a, T>`.
         AngleBracketed(AngleBracketedGenericArguments),
         /// The `(A, B) -> C` in `Fn(A, B) -> C`.
         Parenthesized(ParenthesizedGenericArguments),
     }
 }

 impl Default for PathArguments {
     fn default() -> Self {
         PathArguments::None
     }
 }

 impl PathArguments {
     pub fn is_empty(&self) -> bool {
         match *self {
             PathArguments::None => true,
             PathArguments::AngleBracketed(ref bracketed) => bracketed.args.is_empty(),
             PathArguments::Parenthesized(_) => false,
         }
     }
 }

 ast_enum! {
     /// An individual generic argument, like `'a`, `T`, or `Item = T`.
     ///
     /// *This type is available if Syn is built with the `"derive"` or `"full"`
     /// feature.*
     pub enum GenericArgument {
         /// A lifetime argument.
         Lifetime(Lifetime),
         /// A type argument.
         Type(Type),
         /// A binding (equality constraint) on an associated type: the `Item =
         /// u8` in `Iterator<Item = u8>`.
         Binding(Binding),
         /// A const expression. Must be inside of a block.
         ///
         /// NOTE: Identity expressions are represented as Type arguments, as
         /// they are indistinguishable syntactically.
         Const(Expr),
     }
 }

 ast_struct! {
     /// Angle bracketed arguments of a path segment: the `<K, V>` in `HashMap<K,
     /// V>`.
     ///
     /// *This type is available if Syn is built with the `"derive"` or `"full"`
     /// feature.*
     pub struct AngleBracketedGenericArguments {
         pub colon2_token: Option<Token![::]>,
         pub lt_token: Token![<],
         pub args: Punctuated<GenericArgument, Token![,]>,
         pub gt_token: Token![>],
     }
 }

 ast_struct! {
     /// A binding (equality constraint) on an associated type: `Item = u8`.
     ///
     /// *This type is available if Syn is built with the `"derive"` or `"full"`
     /// feature.*
     pub struct Binding {
         pub ident: Ident,
         pub eq_token: Token![=],
         pub ty: Type,
     }
 }

 ast_struct! {
     /// Arguments of a function path segment: the `(A, B) -> C` in `Fn(A,B) ->
     /// C`.
     ///
     /// *This type is available if Syn is built with the `"derive"` or `"full"`
     /// feature.*
     pub struct ParenthesizedGenericArguments {
         pub paren_token: token::Paren,
         /// `(A, B)`
         pub inputs: Punctuated<Type, Token![,]>,
         /// `C`
         pub output: ReturnType,
     }
 }

 ast_struct! {
     /// The explicit Self type in a qualified path: the `T` in `<T as
     /// Display>::fmt`.
     ///
     /// The actual path, including the trait and the associated item, is stored
     /// separately. The `position` field represents the index of the associated
     /// item qualified with this Self type.
     ///
     /// ```text
     /// <Vec<T> as a::b::Trait>::AssociatedItem
     ///  ^~~~~~    ~~~~~~~~~~~~~~^
     ///  ty        position = 3
     ///
     /// <Vec<T>>::AssociatedItem
     ///  ^~~~~~   ^
     ///  ty       position = 0
     /// ```
     ///
     /// *This type is available if Syn is built with the `"derive"` or `"full"`
     /// feature.*
     pub struct QSelf {
         pub lt_token: Token![<],
         pub ty: Box<Type>,
         pub position: usize,
         pub as_token: Option<Token![as]>,
         pub gt_token: Token![>],
     }
 }

 #[cfg(feature = "parsing")]
 pub mod parsing {
     use super::*;
     use parse::{Parse, ParseStream, Result};
     use synom::ext::IdentExt;
     #[cfg(feature = "full")]
     use expr;

     impl Parse for Path {
         fn parse(input: ParseStream) -> Result<Self> {
             Self::parse_helper(input, false)
         }
     }

     impl Parse for GenericArgument {
         fn parse(input: ParseStream) -> Result<Self> {
             if input.peek(Lifetime) && !input.peek3(Token![+]) {
                 return Ok(GenericArgument::Lifetime(input.parse()?));
             }

             if input.peek(Ident) && input.peek2(Token![=]) {
                 return Ok(GenericArgument::Binding(input.parse()?));
             }

             #[cfg(feature = "full")]
             {
                 if input.peek(Lit) {
                     let lit = input.call(expr::parsing::expr_lit)?;
                     return Ok(GenericArgument::Const(Expr::Lit(lit)));
                 }

                 if input.peek(token::Brace) {
                     let block = input.call(expr::parsing::expr_block)?;
                     return Ok(GenericArgument::Const(Expr::Block(block)));
                 }
             }

             input.parse().map(GenericArgument::Type)
         }
     }

     impl Parse for AngleBracketedGenericArguments {
         fn parse(input: ParseStream) -> Result<Self> {
             Ok(AngleBracketedGenericArguments {
                 colon2_token: input.parse()?,
                 lt_token: input.parse()?,
                 args: {
                     let mut args = Punctuated::new();
                     loop {
                         if input.peek(Token![>]) {
                             break;
                         }
                         let value = input.parse()?;
                         args.push_value(value);
                         if input.peek(Token![>]) {
                             break;
                         }
                         let punct = input.parse()?;
                         args.push_punct(punct);
                     }
                     args
                 },
                 gt_token: input.parse()?,
             })
         }
     }

     impl Parse for ParenthesizedGenericArguments {
         fn parse(input: ParseStream) -> Result<Self> {
             let content;
             Ok(ParenthesizedGenericArguments {
                 paren_token: parenthesized!(content in input),
                 inputs: content.parse_synom(Punctuated::parse_terminated)?,
                 output: input.call(ReturnType::without_plus)?,
             })
         }
     }

     impl Parse for PathSegment {
         fn parse(input: ParseStream) -> Result<Self> {
             Self::parse_helper(input, false)
         }
     }

     impl PathSegment {
         fn parse_helper(input: ParseStream, expr_style: bool) -> Result<Self> {
             if input.peek(Token![super])
                 || input.peek(Token![self])
                 || input.peek(Token![Self])
                 || input.peek(Token![crate])
                 || input.peek(Token![extern])
             {
                 let ident = input.parse_synom(Ident::parse_any)?;
                 return Ok(PathSegment::from(ident));
             }

             let ident = input.parse()?;
             if !expr_style && input.peek(Token![<]) && !input.peek(Token![<=])
                 || input.peek(Token![::]) && input.peek3(Token![<])
             {
                 Ok(PathSegment {
                     ident: ident,
                     arguments: PathArguments::AngleBracketed(input.parse()?),
                 })
             } else {
                 Ok(PathSegment::from(ident))
             }
         }
     }

     impl Parse for Binding {
         fn parse(input: ParseStream) -> Result<Self> {
             Ok(Binding {
                 ident: input.parse()?,
                 eq_token: input.parse()?,
                 ty: input.parse()?,
             })
         }
     }

     impl Path {
         pub fn parse_mod_style(input: ParseStream) -> Result<Self> {
             Ok(Path {
                 leading_colon: input.parse()?,
                 segments: {
                     let mut segments = Punctuated::new();
                     loop {
                         if !input.peek(Ident)
                             && !input.peek(Token![super])
                             && !input.peek(Token![self])
                             && !input.peek(Token![Self])
                             && !input.peek(Token![crate])
                             && !input.peek(Token![extern])
                         {
                             break;
                         }
                         let ident = Ident::parse_any2(input)?;
                         segments.push_value(PathSegment::from(ident));
                         if !input.peek(Token![::]) {
                             break;
                         }
                         let punct = input.parse()?;
                         segments.push_punct(punct);
                     }
                     if segments.is_empty() {
                         return Err(input.error("expected path"));
                     } else if segments.trailing_punct() {
                         return Err(input.error("expected path segment"));
                     }
                     segments
                 },
             })
         }

         fn parse_helper(input: ParseStream, expr_style: bool) -> Result<Self> {
             if input.peek(Token![dyn]) {
                 return Err(input.error("expected path"));
             }

             Ok(Path {
                 leading_colon: input.parse()?,
                 segments: {
                     let mut segments = Punctuated::new();
                     let value = PathSegment::parse_helper(input, expr_style)?;
                     segments.push_value(value);
                     while input.peek(Token![::]) {
                         let punct: Token![::] = input.parse()?;
                         segments.push_punct(punct);
                         let value = PathSegment::parse_helper(input, expr_style)?;
                         segments.push_value(value);
                     }
                     segments
                 },
             })
         }
     }

     pub fn qpath(input: ParseStream, expr_style: bool) -> Result<(Option<QSelf>, Path)> {
         if input.peek(Token![<]) {
             let lt_token: Token![<] = input.parse()?;
             let this: Type = input.parse()?;
             let path = if input.peek(Token![as]) {
                 let as_token: Token![as] = input.parse()?;
                 let path: Path = input.parse()?;
                 Some((as_token, path))
             } else {
                 None
             };
             let gt_token: Token![>] = input.parse()?;
             let colon2_token: Token![::] = input.parse()?;
             let mut rest = Punctuated::new();
             loop {
                 let path = PathSegment::parse_helper(input, expr_style)?;
                 rest.push_value(path);
                 if !input.peek(Token![::]) {
                     break;
                 }
                 let punct: Token![::] = input.parse()?;
                 rest.push_punct(punct);
             }
             let (position, as_token, path) = match path {
                 Some((as_token, mut path)) => {
                     let pos = path.segments.len();
                     path.segments.push_punct(colon2_token);
                     path.segments.extend(rest.into_pairs());
                     (pos, Some(as_token), path)
                 }
                 None => {
                     let path = Path {
                         leading_colon: Some(colon2_token),
                         segments: rest,
                     };
                     (0, None, path)
                 }
             };
             let qself = QSelf {
                 lt_token: lt_token,
                 ty: Box::new(this),
                 position: position,
                 as_token: as_token,
                 gt_token: gt_token,
             };
             Ok((Some(qself), path))
         } else {
             let path = Path::parse_helper(input, expr_style)?;
             Ok((None, path))
         }
     }
 }

 #[cfg(feature = "printing")]
 mod printing {
     use super::*;
     use proc_macro2::TokenStream;
     use quote::ToTokens;

     impl ToTokens for Path {
         fn to_tokens(&self, tokens: &mut TokenStream) {
             self.leading_colon.to_tokens(tokens);
             self.segments.to_tokens(tokens);
         }
     }

     impl ToTokens for PathSegment {
         fn to_tokens(&self, tokens: &mut TokenStream) {
             self.ident.to_tokens(tokens);
             self.arguments.to_tokens(tokens);
         }
     }

     impl ToTokens for PathArguments {
         fn to_tokens(&self, tokens: &mut TokenStream) {
             match *self {
                 PathArguments::None => {}
                 PathArguments::AngleBracketed(ref arguments) => {
                     arguments.to_tokens(tokens);
                 }
                 PathArguments::Parenthesized(ref arguments) => {
                     arguments.to_tokens(tokens);
                 }
             }
         }
     }

     impl ToTokens for GenericArgument {
         #[cfg_attr(feature = "cargo-clippy", allow(match_same_arms))]
         fn to_tokens(&self, tokens: &mut TokenStream) {
             match *self {
                 GenericArgument::Lifetime(ref lt) => lt.to_tokens(tokens),
                 GenericArgument::Type(ref ty) => ty.to_tokens(tokens),
                 GenericArgument::Binding(ref tb) => tb.to_tokens(tokens),
                 GenericArgument::Const(ref e) => match *e {
                     Expr::Lit(_) => e.to_tokens(tokens),

                     // NOTE: We should probably support parsing blocks with only
                     // expressions in them without the full feature for const
                     // generics.
                     #[cfg(feature = "full")]
                     Expr::Block(_) => e.to_tokens(tokens),

                     // ERROR CORRECTION: Add braces to make sure that the
                     // generated code is valid.
                     _ => token::Brace::default().surround(tokens, |tokens| {
                         e.to_tokens(tokens);
                     }),
                 },
             }
         }
     }

     impl ToTokens for AngleBracketedGenericArguments {
         fn to_tokens(&self, tokens: &mut TokenStream) {
             self.colon2_token.to_tokens(tokens);
             self.lt_token.to_tokens(tokens);

             // Print lifetimes before types and consts, all before bindings,
             // regardless of their order in self.args.
             //
             // TODO: ordering rules for const arguments vs type arguments have
             // not been settled yet. https://github.com/rust-lang/rust/issues/44580
             let mut trailing_or_empty = true;
             for param in self.args.pairs() {
                 if let GenericArgument::Lifetime(_) = **param.value() {
                     param.to_tokens(tokens);
                     trailing_or_empty = param.punct().is_some();
                 }
             }
             for param in self.args.pairs() {
                 match **param.value() {
                     GenericArgument::Type(_) | GenericArgument::Const(_) => {
                         if !trailing_or_empty {
                             <Token![,]>::default().to_tokens(tokens);
                         }
                         param.to_tokens(tokens);
                         trailing_or_empty = param.punct().is_some();
                     }
                     GenericArgument::Lifetime(_) | GenericArgument::Binding(_) => {}
                 }
             }
             for param in self.args.pairs() {
                 if let GenericArgument::Binding(_) = **param.value() {
                     if !trailing_or_empty {
                         <Token![,]>::default().to_tokens(tokens);
                         trailing_or_empty = true;
                     }
                     param.to_tokens(tokens);
                 }
             }

             self.gt_token.to_tokens(tokens);
         }
     }

     impl ToTokens for Binding {
         fn to_tokens(&self, tokens: &mut TokenStream) {
             self.ident.to_tokens(tokens);
             self.eq_token.to_tokens(tokens);
             self.ty.to_tokens(tokens);
         }
     }

     impl ToTokens for ParenthesizedGenericArguments {
         fn to_tokens(&self, tokens: &mut TokenStream) {
             self.paren_token.surround(tokens, |tokens| {
                 self.inputs.to_tokens(tokens);
             });
             self.output.to_tokens(tokens);
         }
     }

     impl<'a> ToTokens for PathTokens<'a> {
         fn to_tokens(&self, tokens: &mut TokenStream) {
             let qself = match *self.0 {
                 Some(ref qself) => qself,
                 None => return self.1.to_tokens(tokens),
             };
             qself.lt_token.to_tokens(tokens);
             qself.ty.to_tokens(tokens);

             // XXX: Gross.
             let pos = if qself.position > 0 && qself.position >= self.1.segments.len() {
                 self.1.segments.len() - 1
             } else {
                 qself.position
             };
             let mut segments = self.1.segments.pairs();
             if pos > 0 {
                 TokensOrDefault(&qself.as_token).to_tokens(tokens);
                 self.1.leading_colon.to_tokens(tokens);
                 for (i, segment) in segments.by_ref().take(pos).enumerate() {
                     if i + 1 == pos {
                         segment.value().to_tokens(tokens);
                         qself.gt_token.to_tokens(tokens);
                         segment.punct().to_tokens(tokens);
                     } else {
                         segment.to_tokens(tokens);
                     }
                 }
             } else {
                 qself.gt_token.to_tokens(tokens);
                 self.1.leading_colon.to_tokens(tokens);
             }
             for segment in segments {
                 segment.to_tokens(tokens);
             }
         }
     }
 }
	// Copyright 2018 Syn Developers
	//
	// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
	// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
	// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
	// option. This file may not be copied, modified, or distributed
	// except according to those terms.

	use super::*;
	use punctuated::Punctuated;

	ast_struct! {
	/// A path at which a named item is exported: `std::collections::HashMap`.
	///
	/// *This type is available if Syn is built with the `"derive"` or `"full"`
	/// feature.*
	pub struct Path {
	pub leading_colon: Option<Token![::]>,
	pub segments: Punctuated<PathSegment, Token![::]>,
	}
	}

	impl Path {
	pub fn global(&self) -> bool {
	self.leading_colon.is_some()
	}
	}

	/// A helper for printing a self-type qualified path as tokens.
	///
	/// ```rust
	/// extern crate syn;
	/// extern crate quote;
	/// extern crate proc_macro2;
	///
	/// use syn::{QSelf, Path, PathTokens};
	/// use proc_macro2::TokenStream;
	/// use quote::ToTokens;
	///
	/// struct MyNode {
	/// qself: Option<QSelf>,
	/// path: Path,
	/// }
	///
	/// impl ToTokens for MyNode {
	/// fn to_tokens(&self, tokens: &mut TokenStream) {
	/// PathTokens(&self.qself, &self.path).to_tokens(tokens);
	/// }
	/// }
	/// #
	/// # fn main() {}
	/// ```
	///
	/// *This type is available if Syn is built with the `"derive"` or `"full"`
	/// feature and the `"printing"` feature.*
	#[cfg(feature = "printing")]
	#[cfg_attr(feature = "extra-traits", derive(Debug, Eq, PartialEq, Hash))]
	#[cfg_attr(feature = "clone-impls", derive(Clone))]
	pub struct PathTokens<'a>(pub &'a Option<QSelf>, pub &'a Path);

	impl<T> From<T> for Path
	where
	T: Into<PathSegment>,
	{
	fn from(segment: T) -> Self {
	let mut path = Path {
	leading_colon: None,
	segments: Punctuated::new(),
	};
	path.segments.push_value(segment.into());
	path
	}
	}

	ast_struct! {
	/// A segment of a path together with any path arguments on that segment.
	///
	/// *This type is available if Syn is built with the `"derive"` or `"full"`
	/// feature.*
	pub struct PathSegment {
	pub ident: Ident,
	pub arguments: PathArguments,
	}
	}

	impl<T> From<T> for PathSegment
	where
	T: Into<Ident>,
	{
	fn from(ident: T) -> Self {
	PathSegment {
	ident: ident.into(),
	arguments: PathArguments::None,
	}
	}
	}

	ast_enum! {
	/// Angle bracketed or parenthesized arguments of a path segment.
	///
	/// *This type is available if Syn is built with the `"derive"` or `"full"`
	/// feature.*
	///
	/// ## Angle bracketed
	///
	/// The `<'a, T>` in `std::slice::iter<'a, T>`.
	///
	/// ## Parenthesized
	///
	/// The `(A, B) -> C` in `Fn(A, B) -> C`.
	pub enum PathArguments {
	None,
	/// The `<'a, T>` in `std::slice::iter<'a, T>`.
	AngleBracketed(AngleBracketedGenericArguments),
	/// The `(A, B) -> C` in `Fn(A, B) -> C`.
	Parenthesized(ParenthesizedGenericArguments),
	}
	}

	impl Default for PathArguments {
	fn default() -> Self {
	PathArguments::None
	}
	}

	impl PathArguments {
	pub fn is_empty(&self) -> bool {
	match *self {
	PathArguments::None => true,
	PathArguments::AngleBracketed(ref bracketed) => bracketed.args.is_empty(),
	PathArguments::Parenthesized(_) => false,
	}
	}
	}

	ast_enum! {
	/// An individual generic argument, like `'a`, `T`, or `Item = T`.
	///
	/// *This type is available if Syn is built with the `"derive"` or `"full"`
	/// feature.*
	pub enum GenericArgument {
	/// A lifetime argument.
	Lifetime(Lifetime),
	/// A type argument.
	Type(Type),
	/// A binding (equality constraint) on an associated type: the `Item =
	/// u8` in `Iterator<Item = u8>`.
	Binding(Binding),
	/// A const expression. Must be inside of a block.
	///
	/// NOTE: Identity expressions are represented as Type arguments, as
	/// they are indistinguishable syntactically.
	Const(Expr),
	}
	}

	ast_struct! {
	/// Angle bracketed arguments of a path segment: the `<K, V>` in `HashMap<K,
	/// V>`.
	///
	/// *This type is available if Syn is built with the `"derive"` or `"full"`
	/// feature.*
	pub struct AngleBracketedGenericArguments {
	pub colon2_token: Option<Token![::]>,
	pub lt_token: Token![<],
	pub args: Punctuated<GenericArgument, Token![,]>,
	pub gt_token: Token![>],
	}
	}

	ast_struct! {
	/// A binding (equality constraint) on an associated type: `Item = u8`.
	///
	/// *This type is available if Syn is built with the `"derive"` or `"full"`
	/// feature.*
	pub struct Binding {
	pub ident: Ident,
	pub eq_token: Token![=],
	pub ty: Type,
	}
	}

	ast_struct! {
	/// Arguments of a function path segment: the `(A, B) -> C` in `Fn(A,B) ->
	/// C`.
	///
	/// *This type is available if Syn is built with the `"derive"` or `"full"`
	/// feature.*
	pub struct ParenthesizedGenericArguments {
	pub paren_token: token::Paren,
	/// `(A, B)`
	pub inputs: Punctuated<Type, Token![,]>,
	/// `C`
	pub output: ReturnType,
	}
	}

	ast_struct! {
	/// The explicit Self type in a qualified path: the `T` in `<T as
	/// Display>::fmt`.
	///
	/// The actual path, including the trait and the associated item, is stored
	/// separately. The `position` field represents the index of the associated
	/// item qualified with this Self type.
	///
	/// ```text
	/// <Vec<T> as a::b::Trait>::AssociatedItem
	/// ^~~~~~ ~~~~~~~~~~~~~~^
	/// ty position = 3
	///
	/// <Vec<T>>::AssociatedItem
	/// ^~~~~~ ^
	/// ty position = 0
	/// ```
	///
	/// *This type is available if Syn is built with the `"derive"` or `"full"`
	/// feature.*
	pub struct QSelf {
	pub lt_token: Token![<],
	pub ty: Box<Type>,
	pub position: usize,
	pub as_token: Option<Token![as]>,
	pub gt_token: Token![>],
	}
	}

	#[cfg(feature = "parsing")]
	pub mod parsing {
	use super::*;
	use parse::{Parse, ParseStream, Result};
	use synom::ext::IdentExt;
	#[cfg(feature = "full")]
	use expr;

	impl Parse for Path {
	fn parse(input: ParseStream) -> Result<Self> {
	Self::parse_helper(input, false)
	}
	}

	impl Parse for GenericArgument {
	fn parse(input: ParseStream) -> Result<Self> {
	if input.peek(Lifetime) && !input.peek3(Token![+]) {
	return Ok(GenericArgument::Lifetime(input.parse()?));
	}

	if input.peek(Ident) && input.peek2(Token![=]) {
	return Ok(GenericArgument::Binding(input.parse()?));
	}

	#[cfg(feature = "full")]
	{
	if input.peek(Lit) {
	let lit = input.call(expr::parsing::expr_lit)?;
	return Ok(GenericArgument::Const(Expr::Lit(lit)));
	}

	if input.peek(token::Brace) {
	let block = input.call(expr::parsing::expr_block)?;
	return Ok(GenericArgument::Const(Expr::Block(block)));
	}
	}

	input.parse().map(GenericArgument::Type)
	}
	}

	impl Parse for AngleBracketedGenericArguments {
	fn parse(input: ParseStream) -> Result<Self> {
	Ok(AngleBracketedGenericArguments {
	colon2_token: input.parse()?,
	lt_token: input.parse()?,
	args: {
	let mut args = Punctuated::new();
	loop {
	if input.peek(Token![>]) {
	break;
	}
	let value = input.parse()?;
	args.push_value(value);
	if input.peek(Token![>]) {
	break;
	}
	let punct = input.parse()?;
	args.push_punct(punct);
	}
	args
	},
	gt_token: input.parse()?,
	})
	}
	}

	impl Parse for ParenthesizedGenericArguments {
	fn parse(input: ParseStream) -> Result<Self> {
	let content;
	Ok(ParenthesizedGenericArguments {
	paren_token: parenthesized!(content in input),
	inputs: content.parse_synom(Punctuated::parse_terminated)?,
	output: input.call(ReturnType::without_plus)?,
	})
	}
	}

	impl Parse for PathSegment {
	fn parse(input: ParseStream) -> Result<Self> {
	Self::parse_helper(input, false)
	}
	}

	impl PathSegment {
	fn parse_helper(input: ParseStream, expr_style: bool) -> Result<Self> {
	if input.peek(Token![super])
	\|\| input.peek(Token![self])
	\|\| input.peek(Token![Self])
	\|\| input.peek(Token![crate])
	\|\| input.peek(Token![extern])
	{
	let ident = input.parse_synom(Ident::parse_any)?;
	return Ok(PathSegment::from(ident));
	}

	let ident = input.parse()?;
	if !expr_style && input.peek(Token![<]) && !input.peek(Token![<=])
	\|\| input.peek(Token![::]) && input.peek3(Token![<])
	{
	Ok(PathSegment {
	ident: ident,
	arguments: PathArguments::AngleBracketed(input.parse()?),
	})
	} else {
	Ok(PathSegment::from(ident))
	}
	}
	}

	impl Parse for Binding {
	fn parse(input: ParseStream) -> Result<Self> {
	Ok(Binding {
	ident: input.parse()?,
	eq_token: input.parse()?,
	ty: input.parse()?,
	})
	}
	}

	impl Path {
	pub fn parse_mod_style(input: ParseStream) -> Result<Self> {
	Ok(Path {
	leading_colon: input.parse()?,
	segments: {
	let mut segments = Punctuated::new();
	loop {
	if !input.peek(Ident)
	&& !input.peek(Token![super])
	&& !input.peek(Token![self])
	&& !input.peek(Token![Self])
	&& !input.peek(Token![crate])
	&& !input.peek(Token![extern])
	{
	break;
	}
	let ident = Ident::parse_any2(input)?;
	segments.push_value(PathSegment::from(ident));
	if !input.peek(Token![::]) {
	break;
	}
	let punct = input.parse()?;
	segments.push_punct(punct);
	}
	if segments.is_empty() {
	return Err(input.error("expected path"));
	} else if segments.trailing_punct() {
	return Err(input.error("expected path segment"));
	}
	segments
	},
	})
	}

	fn parse_helper(input: ParseStream, expr_style: bool) -> Result<Self> {
	if input.peek(Token![dyn]) {
	return Err(input.error("expected path"));
	}

	Ok(Path {
	leading_colon: input.parse()?,
	segments: {
	let mut segments = Punctuated::new();
	let value = PathSegment::parse_helper(input, expr_style)?;
	segments.push_value(value);
	while input.peek(Token![::]) {
	let punct: Token![::] = input.parse()?;
	segments.push_punct(punct);
	let value = PathSegment::parse_helper(input, expr_style)?;
	segments.push_value(value);
	}
	segments
	},
	})
	}
	}

	pub fn qpath(input: ParseStream, expr_style: bool) -> Result<(Option<QSelf>, Path)> {
	if input.peek(Token![<]) {
	let lt_token: Token![<] = input.parse()?;
	let this: Type = input.parse()?;
	let path = if input.peek(Token![as]) {
	let as_token: Token![as] = input.parse()?;
	let path: Path = input.parse()?;
	Some((as_token, path))
	} else {
	None
	};
	let gt_token: Token![>] = input.parse()?;
	let colon2_token: Token![::] = input.parse()?;
	let mut rest = Punctuated::new();
	loop {
	let path = PathSegment::parse_helper(input, expr_style)?;
	rest.push_value(path);
	if !input.peek(Token![::]) {
	break;
	}
	let punct: Token![::] = input.parse()?;
	rest.push_punct(punct);
	}
	let (position, as_token, path) = match path {
	Some((as_token, mut path)) => {
	let pos = path.segments.len();
	path.segments.push_punct(colon2_token);
	path.segments.extend(rest.into_pairs());
	(pos, Some(as_token), path)
	}
	None => {
	let path = Path {
	leading_colon: Some(colon2_token),
	segments: rest,
	};
	(0, None, path)
	}
	};
	let qself = QSelf {
	lt_token: lt_token,
	ty: Box::new(this),
	position: position,
	as_token: as_token,
	gt_token: gt_token,
	};
	Ok((Some(qself), path))
	} else {
	let path = Path::parse_helper(input, expr_style)?;
	Ok((None, path))
	}
	}
	}

	#[cfg(feature = "printing")]
	mod printing {
	use super::*;
	use proc_macro2::TokenStream;
	use quote::ToTokens;

	impl ToTokens for Path {
	fn to_tokens(&self, tokens: &mut TokenStream) {
	self.leading_colon.to_tokens(tokens);
	self.segments.to_tokens(tokens);
	}
	}

	impl ToTokens for PathSegment {
	fn to_tokens(&self, tokens: &mut TokenStream) {
	self.ident.to_tokens(tokens);
	self.arguments.to_tokens(tokens);
	}
	}

	impl ToTokens for PathArguments {
	fn to_tokens(&self, tokens: &mut TokenStream) {
	match *self {
	PathArguments::None => {}
	PathArguments::AngleBracketed(ref arguments) => {
	arguments.to_tokens(tokens);
	}
	PathArguments::Parenthesized(ref arguments) => {
	arguments.to_tokens(tokens);
	}
	}
	}
	}

	impl ToTokens for GenericArgument {
	#[cfg_attr(feature = "cargo-clippy", allow(match_same_arms))]
	fn to_tokens(&self, tokens: &mut TokenStream) {
	match *self {
	GenericArgument::Lifetime(ref lt) => lt.to_tokens(tokens),
	GenericArgument::Type(ref ty) => ty.to_tokens(tokens),
	GenericArgument::Binding(ref tb) => tb.to_tokens(tokens),
	GenericArgument::Const(ref e) => match *e {
	Expr::Lit(_) => e.to_tokens(tokens),

	// NOTE: We should probably support parsing blocks with only
	// expressions in them without the full feature for const
	// generics.
	#[cfg(feature = "full")]
	Expr::Block(_) => e.to_tokens(tokens),

	// ERROR CORRECTION: Add braces to make sure that the
	// generated code is valid.
	_ => token::Brace::default().surround(tokens, \|tokens\| {
	e.to_tokens(tokens);
	}),
	},
	}
	}
	}

	impl ToTokens for AngleBracketedGenericArguments {
	fn to_tokens(&self, tokens: &mut TokenStream) {
	self.colon2_token.to_tokens(tokens);
	self.lt_token.to_tokens(tokens);

	// Print lifetimes before types and consts, all before bindings,
	// regardless of their order in self.args.
	//
	// TODO: ordering rules for const arguments vs type arguments have
	// not been settled yet. https://github.com/rust-lang/rust/issues/44580
	let mut trailing_or_empty = true;
	for param in self.args.pairs() {
	if let GenericArgument::Lifetime(_) = **param.value() {
	param.to_tokens(tokens);
	trailing_or_empty = param.punct().is_some();
	}
	}
	for param in self.args.pairs() {
	match **param.value() {
	GenericArgument::Type(_) \| GenericArgument::Const(_) => {
	if !trailing_or_empty {
	<Token![,]>::default().to_tokens(tokens);
	}
	param.to_tokens(tokens);
	trailing_or_empty = param.punct().is_some();
	}
	GenericArgument::Lifetime(_) \| GenericArgument::Binding(_) => {}
	}
	}
	for param in self.args.pairs() {
	if let GenericArgument::Binding(_) = **param.value() {
	if !trailing_or_empty {
	<Token![,]>::default().to_tokens(tokens);
	trailing_or_empty = true;
	}
	param.to_tokens(tokens);
	}
	}

	self.gt_token.to_tokens(tokens);
	}
	}

	impl ToTokens for Binding {
	fn to_tokens(&self, tokens: &mut TokenStream) {
	self.ident.to_tokens(tokens);
	self.eq_token.to_tokens(tokens);
	self.ty.to_tokens(tokens);
	}
	}

	impl ToTokens for ParenthesizedGenericArguments {
	fn to_tokens(&self, tokens: &mut TokenStream) {
	self.paren_token.surround(tokens, \|tokens\| {
	self.inputs.to_tokens(tokens);
	});
	self.output.to_tokens(tokens);
	}
	}

	impl<'a> ToTokens for PathTokens<'a> {
	fn to_tokens(&self, tokens: &mut TokenStream) {
	let qself = match *self.0 {
	Some(ref qself) => qself,
	None => return self.1.to_tokens(tokens),
	};
	qself.lt_token.to_tokens(tokens);
	qself.ty.to_tokens(tokens);

	// XXX: Gross.
	let pos = if qself.position > 0 && qself.position >= self.1.segments.len() {
	self.1.segments.len() - 1
	} else {
	qself.position
	};
	let mut segments = self.1.segments.pairs();
	if pos > 0 {
	TokensOrDefault(&qself.as_token).to_tokens(tokens);
	self.1.leading_colon.to_tokens(tokens);
	for (i, segment) in segments.by_ref().take(pos).enumerate() {
	if i + 1 == pos {
	segment.value().to_tokens(tokens);
	qself.gt_token.to_tokens(tokens);
	segment.punct().to_tokens(tokens);
	} else {
	segment.to_tokens(tokens);
	}
	}
	} else {
	qself.gt_token.to_tokens(tokens);
	self.1.leading_colon.to_tokens(tokens);
	}
	for segment in segments {
	segment.to_tokens(tokens);
	}
	}
	}
	}