compiler/rustc_ast/src/tokenstream.rs - third_party/rust - Git at Google

 //! # Token Streams
 //!
 //! `TokenStream`s represent syntactic objects before they are converted into ASTs.
 //! A `TokenStream` is, roughly speaking, a sequence of [`TokenTree`]s,
 //! which are themselves a single [`Token`] or a `Delimited` subsequence of tokens.
 //!
 //! ## Ownership
 //!
 //! `TokenStream`s are persistent data structures constructed as ropes with reference
 //! counted-children. In general, this means that calling an operation on a `TokenStream`
 //! (such as `slice`) produces an entirely new `TokenStream` from the borrowed reference to
 //! the original. This essentially coerces `TokenStream`s into "views" of their subparts,
 //! and a borrowed `TokenStream` is sufficient to build an owned `TokenStream` without taking
 //! ownership of the original.

 use crate::ast::StmtKind;
 use crate::ast_traits::{HasAttrs, HasSpan, HasTokens};
 use crate::token::{self, Delimiter, Nonterminal, Token, TokenKind};
 use crate::AttrVec;

 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::{self, Lrc};
 use rustc_macros::HashStable_Generic;
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_span::{Span, DUMMY_SP};
 use smallvec::{smallvec, SmallVec};

 use std::{fmt, iter};

 /// When the main Rust parser encounters a syntax-extension invocation, it
 /// parses the arguments to the invocation as a token tree. This is a very
 /// loose structure, such that all sorts of different AST fragments can
 /// be passed to syntax extensions using a uniform type.
 ///
 /// If the syntax extension is an MBE macro, it will attempt to match its
 /// LHS token tree against the provided token tree, and if it finds a
 /// match, will transcribe the RHS token tree, splicing in any captured
 /// `macro_parser::matched_nonterminals` into the `SubstNt`s it finds.
 ///
 /// The RHS of an MBE macro is the only place `SubstNt`s are substituted.
 /// Nothing special happens to misnamed or misplaced `SubstNt`s.
 #[derive(Debug, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
 pub enum TokenTree {
     /// A single token. Should never be `OpenDelim` or `CloseDelim`, because
     /// delimiters are implicitly represented by `Delimited`.
     Token(Token, Spacing),
     /// A delimited sequence of token trees.
     Delimited(DelimSpan, Delimiter, TokenStream),
 }

 // Ensure all fields of `TokenTree` is `Send` and `Sync`.
 #[cfg(parallel_compiler)]
 fn _dummy()
 where
     Token: Send + Sync,
     DelimSpan: Send + Sync,
     Delimiter: Send + Sync,
     TokenStream: Send + Sync,
 {
 }

 impl TokenTree {
     /// Checks if this `TokenTree` is equal to the other, regardless of span information.
     pub fn eq_unspanned(&self, other: &TokenTree) -> bool {
         match (self, other) {
             (TokenTree::Token(token, _), TokenTree::Token(token2, _)) => token.kind == token2.kind,
             (TokenTree::Delimited(_, delim, tts), TokenTree::Delimited(_, delim2, tts2)) => {
                 delim == delim2 && tts.eq_unspanned(tts2)
             }
             _ => false,
         }
     }

     /// Retrieves the `TokenTree`'s span.
     pub fn span(&self) -> Span {
         match self {
             TokenTree::Token(token, _) => token.span,
             TokenTree::Delimited(sp, ..) => sp.entire(),
         }
     }

     /// Modify the `TokenTree`'s span in-place.
     pub fn set_span(&mut self, span: Span) {
         match self {
             TokenTree::Token(token, _) => token.span = span,
             TokenTree::Delimited(dspan, ..) => *dspan = DelimSpan::from_single(span),
         }
     }

     /// Create a `TokenTree::Token` with alone spacing.
     pub fn token_alone(kind: TokenKind, span: Span) -> TokenTree {
         TokenTree::Token(Token::new(kind, span), Spacing::Alone)
     }

     /// Create a `TokenTree::Token` with joint spacing.
     pub fn token_joint(kind: TokenKind, span: Span) -> TokenTree {
         TokenTree::Token(Token::new(kind, span), Spacing::Joint)
     }

     pub fn uninterpolate(self) -> TokenTree {
         match self {
             TokenTree::Token(token, spacing) => {
                 TokenTree::Token(token.uninterpolate().into_owned(), spacing)
             }
             tt => tt,
         }
     }
 }

 impl<CTX> HashStable<CTX> for TokenStream
 where
     CTX: crate::HashStableContext,
 {
     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
         for sub_tt in self.trees() {
             sub_tt.hash_stable(hcx, hasher);
         }
     }
 }

 pub trait ToAttrTokenStream: sync::Send + sync::Sync {
     fn to_attr_token_stream(&self) -> AttrTokenStream;
 }

 impl ToAttrTokenStream for AttrTokenStream {
     fn to_attr_token_stream(&self) -> AttrTokenStream {
         self.clone()
     }
 }

 /// A lazy version of [`TokenStream`], which defers creation
 /// of an actual `TokenStream` until it is needed.
 /// `Box` is here only to reduce the structure size.
 #[derive(Clone)]
 pub struct LazyAttrTokenStream(Lrc<Box<dyn ToAttrTokenStream>>);

 impl LazyAttrTokenStream {
     pub fn new(inner: impl ToAttrTokenStream + 'static) -> LazyAttrTokenStream {
         LazyAttrTokenStream(Lrc::new(Box::new(inner)))
     }

     pub fn to_attr_token_stream(&self) -> AttrTokenStream {
         self.0.to_attr_token_stream()
     }
 }

 impl fmt::Debug for LazyAttrTokenStream {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "LazyAttrTokenStream({:?})", self.to_attr_token_stream())
     }
 }

 impl<S: Encoder> Encodable<S> for LazyAttrTokenStream {
     fn encode(&self, s: &mut S) {
         // Used by AST json printing.
         Encodable::encode(&self.to_attr_token_stream(), s);
     }
 }

 impl<D: Decoder> Decodable<D> for LazyAttrTokenStream {
     fn decode(_d: &mut D) -> Self {
         panic!("Attempted to decode LazyAttrTokenStream");
     }
 }

 impl<CTX> HashStable<CTX> for LazyAttrTokenStream {
     fn hash_stable(&self, _hcx: &mut CTX, _hasher: &mut StableHasher) {
         panic!("Attempted to compute stable hash for LazyAttrTokenStream");
     }
 }

 /// An `AttrTokenStream` is similar to a `TokenStream`, but with extra
 /// information about the tokens for attribute targets. This is used
 /// during expansion to perform early cfg-expansion, and to process attributes
 /// during proc-macro invocations.
 #[derive(Clone, Debug, Default, Encodable, Decodable)]
 pub struct AttrTokenStream(pub Lrc<Vec<AttrTokenTree>>);

 /// Like `TokenTree`, but for `AttrTokenStream`.
 #[derive(Clone, Debug, Encodable, Decodable)]
 pub enum AttrTokenTree {
     Token(Token, Spacing),
     Delimited(DelimSpan, Delimiter, AttrTokenStream),
     /// Stores the attributes for an attribute target,
     /// along with the tokens for that attribute target.
     /// See `AttributesData` for more information
     Attributes(AttributesData),
 }

 impl AttrTokenStream {
     pub fn new(tokens: Vec<AttrTokenTree>) -> AttrTokenStream {
         AttrTokenStream(Lrc::new(tokens))
     }

     /// Converts this `AttrTokenStream` to a plain `TokenStream`.
     /// During conversion, `AttrTokenTree::Attributes` get 'flattened'
     /// back to a `TokenStream` of the form `outer_attr attr_target`.
     /// If there are inner attributes, they are inserted into the proper
     /// place in the attribute target tokens.
     pub fn to_tokenstream(&self) -> TokenStream {
         let trees: Vec<_> = self
             .0
             .iter()
             .flat_map(|tree| match &tree {
                 AttrTokenTree::Token(inner, spacing) => {
                     smallvec![TokenTree::Token(inner.clone(), *spacing)].into_iter()
                 }
                 AttrTokenTree::Delimited(span, delim, stream) => {
                     smallvec![TokenTree::Delimited(*span, *delim, stream.to_tokenstream()),]
                         .into_iter()
                 }
                 AttrTokenTree::Attributes(data) => {
                     let mut outer_attrs = Vec::new();
                     let mut inner_attrs = Vec::new();
                     for attr in &data.attrs {
                         match attr.style {
                             crate::AttrStyle::Outer => outer_attrs.push(attr),
                             crate::AttrStyle::Inner => inner_attrs.push(attr),
                         }
                     }

                     let mut target_tokens: Vec<_> = data
                         .tokens
                         .to_attr_token_stream()
                         .to_tokenstream()
                         .0
                         .iter()
                         .cloned()
                         .collect();
                     if !inner_attrs.is_empty() {
                         let mut found = false;
                         // Check the last two trees (to account for a trailing semi)
                         for tree in target_tokens.iter_mut().rev().take(2) {
                             if let TokenTree::Delimited(span, delim, delim_tokens) = tree {
                                 // Inner attributes are only supported on extern blocks, functions,
                                 // impls, and modules. All of these have their inner attributes
                                 // placed at the beginning of the rightmost outermost braced group:
                                 // e.g. fn foo() { #![my_attr} }
                                 //
                                 // Therefore, we can insert them back into the right location
                                 // without needing to do any extra position tracking.
                                 //
                                 // Note: Outline modules are an exception - they can
                                 // have attributes like `#![my_attr]` at the start of a file.
                                 // Support for custom attributes in this position is not
                                 // properly implemented - we always synthesize fake tokens,
                                 // so we never reach this code.

                                 let mut stream = TokenStream::default();
                                 for inner_attr in inner_attrs {
                                     stream.push_stream(inner_attr.tokens());
                                 }
                                 stream.push_stream(delim_tokens.clone());
                                 *tree = TokenTree::Delimited(*span, *delim, stream);
                                 found = true;
                                 break;
                             }
                         }

                         assert!(
                             found,
                             "Failed to find trailing delimited group in: {target_tokens:?}"
                         );
                     }
                     let mut flat: SmallVec<[_; 1]> = SmallVec::new();
                     for attr in outer_attrs {
                         // FIXME: Make this more efficient
                         flat.extend(attr.tokens().0.clone().iter().cloned());
                     }
                     flat.extend(target_tokens);
                     flat.into_iter()
                 }
             })
             .collect();
         TokenStream::new(trees)
     }
 }

 /// Stores the tokens for an attribute target, along
 /// with its attributes.
 ///
 /// This is constructed during parsing when we need to capture
 /// tokens.
 ///
 /// For example, `#[cfg(FALSE)] struct Foo {}` would
 /// have an `attrs` field containing the `#[cfg(FALSE)]` attr,
 /// and a `tokens` field storing the (unparsed) tokens `struct Foo {}`
 #[derive(Clone, Debug, Encodable, Decodable)]
 pub struct AttributesData {
     /// Attributes, both outer and inner.
     /// These are stored in the original order that they were parsed in.
     pub attrs: AttrVec,
     /// The underlying tokens for the attribute target that `attrs`
     /// are applied to
     pub tokens: LazyAttrTokenStream,
 }

 /// A `TokenStream` is an abstract sequence of tokens, organized into [`TokenTree`]s.
 ///
 /// The goal is for procedural macros to work with `TokenStream`s and `TokenTree`s
 /// instead of a representation of the abstract syntax tree.
 /// Today's `TokenTree`s can still contain AST via `token::Interpolated` for
 /// backwards compatibility.
 #[derive(Clone, Debug, Default, Encodable, Decodable)]
 pub struct TokenStream(pub(crate) Lrc<Vec<TokenTree>>);

 /// Similar to `proc_macro::Spacing`, but for tokens.
 ///
 /// Note that all `ast::TokenTree::Token` instances have a `Spacing`, but when
 /// we convert to `proc_macro::TokenTree` for proc macros only `Punct`
 /// `TokenTree`s have a `proc_macro::Spacing`.
 #[derive(Clone, Copy, Debug, PartialEq, Encodable, Decodable, HashStable_Generic)]
 pub enum Spacing {
     /// The token is not immediately followed by an operator token (as
     /// determined by `Token::is_op`). E.g. a `+` token is `Alone` in `+ =`,
     /// `+/*foo*/=`, `+ident`, and `+()`.
     Alone,

     /// The token is immediately followed by an operator token. E.g. a `+`
     /// token is `Joint` in `+=` and `++`.
     Joint,
 }

 impl TokenStream {
     /// Given a `TokenStream` with a `Stream` of only two arguments, return a new `TokenStream`
     /// separating the two arguments with a comma for diagnostic suggestions.
     pub fn add_comma(&self) -> Option<(TokenStream, Span)> {
         // Used to suggest if a user writes `foo!(a b);`
         let mut suggestion = None;
         let mut iter = self.0.iter().enumerate().peekable();
         while let Some((pos, ts)) = iter.next() {
             if let Some((_, next)) = iter.peek() {
                 let sp = match (&ts, &next) {
                     (_, TokenTree::Token(Token { kind: token::Comma, .. }, _)) => continue,
                     (
                         TokenTree::Token(token_left, Spacing::Alone),
                         TokenTree::Token(token_right, _),
                     ) if ((token_left.is_ident() && !token_left.is_reserved_ident())
                         || token_left.is_lit())
                         && ((token_right.is_ident() && !token_right.is_reserved_ident())
                             || token_right.is_lit()) =>
                     {
                         token_left.span
                     }
                     (TokenTree::Delimited(sp, ..), _) => sp.entire(),
                     _ => continue,
                 };
                 let sp = sp.shrink_to_hi();
                 let comma = TokenTree::token_alone(token::Comma, sp);
                 suggestion = Some((pos, comma, sp));
             }
         }
         if let Some((pos, comma, sp)) = suggestion {
             let mut new_stream = Vec::with_capacity(self.0.len() + 1);
             let parts = self.0.split_at(pos + 1);
             new_stream.extend_from_slice(parts.0);
             new_stream.push(comma);
             new_stream.extend_from_slice(parts.1);
             return Some((TokenStream::new(new_stream), sp));
         }
         None
     }
 }

 impl FromIterator<TokenTree> for TokenStream {
     fn from_iter<I: IntoIterator<Item = TokenTree>>(iter: I) -> Self {
         TokenStream::new(iter.into_iter().collect::<Vec<TokenTree>>())
     }
 }

 impl Eq for TokenStream {}

 impl PartialEq<TokenStream> for TokenStream {
     fn eq(&self, other: &TokenStream) -> bool {
         self.trees().eq(other.trees())
     }
 }

 impl TokenStream {
     pub fn new(streams: Vec<TokenTree>) -> TokenStream {
         TokenStream(Lrc::new(streams))
     }

     pub fn is_empty(&self) -> bool {
         self.0.is_empty()
     }

     pub fn len(&self) -> usize {
         self.0.len()
     }

     pub fn trees(&self) -> RefTokenTreeCursor<'_> {
         RefTokenTreeCursor::new(self)
     }

     pub fn into_trees(self) -> TokenTreeCursor {
         TokenTreeCursor::new(self)
     }

     /// Compares two `TokenStream`s, checking equality without regarding span information.
     pub fn eq_unspanned(&self, other: &TokenStream) -> bool {
         let mut t1 = self.trees();
         let mut t2 = other.trees();
         for (t1, t2) in iter::zip(&mut t1, &mut t2) {
             if !t1.eq_unspanned(t2) {
                 return false;
             }
         }
         t1.next().is_none() && t2.next().is_none()
     }

     pub fn map_enumerated<F: FnMut(usize, &TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream {
         TokenStream(Lrc::new(self.0.iter().enumerate().map(|(i, tree)| f(i, tree)).collect()))
     }

     /// Create a token stream containing a single token with alone spacing.
     pub fn token_alone(kind: TokenKind, span: Span) -> TokenStream {
         TokenStream::new(vec![TokenTree::token_alone(kind, span)])
     }

     /// Create a token stream containing a single token with joint spacing.
     pub fn token_joint(kind: TokenKind, span: Span) -> TokenStream {
         TokenStream::new(vec![TokenTree::token_joint(kind, span)])
     }

     /// Create a token stream containing a single `Delimited`.
     pub fn delimited(span: DelimSpan, delim: Delimiter, tts: TokenStream) -> TokenStream {
         TokenStream::new(vec![TokenTree::Delimited(span, delim, tts)])
     }

     pub fn from_ast(node: &(impl HasAttrs + HasSpan + HasTokens + fmt::Debug)) -> TokenStream {
         let Some(tokens) = node.tokens() else {
             panic!("missing tokens for node at {:?}: {:?}", node.span(), node);
         };
         let attrs = node.attrs();
         let attr_stream = if attrs.is_empty() {
             tokens.to_attr_token_stream()
         } else {
             let attr_data =
                 AttributesData { attrs: attrs.iter().cloned().collect(), tokens: tokens.clone() };
             AttrTokenStream::new(vec![AttrTokenTree::Attributes(attr_data)])
         };
         attr_stream.to_tokenstream()
     }

     pub fn from_nonterminal_ast(nt: &Nonterminal) -> TokenStream {
         match nt {
             Nonterminal::NtIdent(ident, is_raw) => {
                 TokenStream::token_alone(token::Ident(ident.name, *is_raw), ident.span)
             }
             Nonterminal::NtLifetime(ident) => {
                 TokenStream::token_alone(token::Lifetime(ident.name), ident.span)
             }
             Nonterminal::NtItem(item) => TokenStream::from_ast(item),
             Nonterminal::NtBlock(block) => TokenStream::from_ast(block),
             Nonterminal::NtStmt(stmt) if let StmtKind::Empty = stmt.kind => {
                 // FIXME: Properly collect tokens for empty statements.
                 TokenStream::token_alone(token::Semi, stmt.span)
             }
             Nonterminal::NtStmt(stmt) => TokenStream::from_ast(stmt),
             Nonterminal::NtPat(pat) => TokenStream::from_ast(pat),
             Nonterminal::NtTy(ty) => TokenStream::from_ast(ty),
             Nonterminal::NtMeta(attr) => TokenStream::from_ast(attr),
             Nonterminal::NtPath(path) => TokenStream::from_ast(path),
             Nonterminal::NtVis(vis) => TokenStream::from_ast(vis),
             Nonterminal::NtExpr(expr) | Nonterminal::NtLiteral(expr) => TokenStream::from_ast(expr),
         }
     }

     fn flatten_token(token: &Token, spacing: Spacing) -> TokenTree {
         match &token.kind {
             token::Interpolated(nt) if let token::NtIdent(ident, is_raw) = **nt => {
                 TokenTree::Token(Token::new(token::Ident(ident.name, is_raw), ident.span), spacing)
             }
             token::Interpolated(nt) => TokenTree::Delimited(
                 DelimSpan::from_single(token.span),
                 Delimiter::Invisible,
                 TokenStream::from_nonterminal_ast(nt).flattened(),
             ),
             _ => TokenTree::Token(token.clone(), spacing),
         }
     }

     fn flatten_token_tree(tree: &TokenTree) -> TokenTree {
         match tree {
             TokenTree::Token(token, spacing) => TokenStream::flatten_token(token, *spacing),
             TokenTree::Delimited(span, delim, tts) => {
                 TokenTree::Delimited(*span, *delim, tts.flattened())
             }
         }
     }

     #[must_use]
     pub fn flattened(&self) -> TokenStream {
         fn can_skip(stream: &TokenStream) -> bool {
             stream.trees().all(|tree| match tree {
                 TokenTree::Token(token, _) => !matches!(token.kind, token::Interpolated(_)),
                 TokenTree::Delimited(_, _, inner) => can_skip(inner),
             })
         }

         if can_skip(self) {
             return self.clone();
         }

         self.trees().map(|tree| TokenStream::flatten_token_tree(tree)).collect()
     }

     // If `vec` is not empty, try to glue `tt` onto its last token. The return
     // value indicates if gluing took place.
     fn try_glue_to_last(vec: &mut Vec<TokenTree>, tt: &TokenTree) -> bool {
         if let Some(TokenTree::Token(last_tok, Spacing::Joint)) = vec.last()
             && let TokenTree::Token(tok, spacing) = tt
             && let Some(glued_tok) = last_tok.glue(tok)
         {
             // ...then overwrite the last token tree in `vec` with the
             // glued token, and skip the first token tree from `stream`.
             *vec.last_mut().unwrap() = TokenTree::Token(glued_tok, *spacing);
             true
         } else {
             false
         }
     }

     /// Push `tt` onto the end of the stream, possibly gluing it to the last
     /// token. Uses `make_mut` to maximize efficiency.
     pub fn push_tree(&mut self, tt: TokenTree) {
         let vec_mut = Lrc::make_mut(&mut self.0);

         if Self::try_glue_to_last(vec_mut, &tt) {
             // nothing else to do
         } else {
             vec_mut.push(tt);
         }
     }

     /// Push `stream` onto the end of the stream, possibly gluing the first
     /// token tree to the last token. (No other token trees will be glued.)
     /// Uses `make_mut` to maximize efficiency.
     pub fn push_stream(&mut self, stream: TokenStream) {
         let vec_mut = Lrc::make_mut(&mut self.0);

         let stream_iter = stream.0.iter().cloned();

         if let Some(first) = stream.0.first() && Self::try_glue_to_last(vec_mut, first) {
             // Now skip the first token tree from `stream`.
             vec_mut.extend(stream_iter.skip(1));
         } else {
             // Append all of `stream`.
             vec_mut.extend(stream_iter);
         }
     }
 }

 /// By-reference iterator over a [`TokenStream`], that produces `&TokenTree`
 /// items.
 #[derive(Clone)]
 pub struct RefTokenTreeCursor<'t> {
     stream: &'t TokenStream,
     index: usize,
 }

 impl<'t> RefTokenTreeCursor<'t> {
     fn new(stream: &'t TokenStream) -> Self {
         RefTokenTreeCursor { stream, index: 0 }
     }

     pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
         self.stream.0.get(self.index + n)
     }
 }

 impl<'t> Iterator for RefTokenTreeCursor<'t> {
     type Item = &'t TokenTree;

     fn next(&mut self) -> Option<&'t TokenTree> {
         self.stream.0.get(self.index).map(|tree| {
             self.index += 1;
             tree
         })
     }
 }

 /// Owning by-value iterator over a [`TokenStream`], that produces `TokenTree`
 /// items.
 // FIXME: Many uses of this can be replaced with by-reference iterator to avoid clones.
 #[derive(Clone)]
 pub struct TokenTreeCursor {
     pub stream: TokenStream,
     index: usize,
 }

 impl Iterator for TokenTreeCursor {
     type Item = TokenTree;

     fn next(&mut self) -> Option<TokenTree> {
         self.stream.0.get(self.index).map(|tree| {
             self.index += 1;
             tree.clone()
         })
     }
 }

 impl TokenTreeCursor {
     fn new(stream: TokenStream) -> Self {
         TokenTreeCursor { stream, index: 0 }
     }

     #[inline]
     pub fn next_ref(&mut self) -> Option<&TokenTree> {
         self.stream.0.get(self.index).map(|tree| {
             self.index += 1;
             tree
         })
     }

     pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
         self.stream.0.get(self.index + n)
     }

     // Replace the previously obtained token tree with `tts`, and rewind to
     // just before them.
     pub fn replace_prev_and_rewind(&mut self, tts: Vec<TokenTree>) {
         assert!(self.index > 0);
         self.index -= 1;
         let stream = Lrc::make_mut(&mut self.stream.0);
         stream.splice(self.index..self.index + 1, tts);
     }
 }

 #[derive(Debug, Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
 pub struct DelimSpan {
     pub open: Span,
     pub close: Span,
 }

 impl DelimSpan {
     pub fn from_single(sp: Span) -> Self {
         DelimSpan { open: sp, close: sp }
     }

     pub fn from_pair(open: Span, close: Span) -> Self {
         DelimSpan { open, close }
     }

     pub fn dummy() -> Self {
         Self::from_single(DUMMY_SP)
     }

     pub fn entire(self) -> Span {
         self.open.with_hi(self.close.hi())
     }
 }

 // Some types are used a lot. Make sure they don't unintentionally get bigger.
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 mod size_asserts {
     use super::*;
     use rustc_data_structures::static_assert_size;
     // tidy-alphabetical-start
     static_assert_size!(AttrTokenStream, 8);
     static_assert_size!(AttrTokenTree, 32);
     static_assert_size!(LazyAttrTokenStream, 8);
     static_assert_size!(TokenStream, 8);
     static_assert_size!(TokenTree, 32);
     // tidy-alphabetical-end
 }
	//! # Token Streams
	//!
	//! `TokenStream`s represent syntactic objects before they are converted into ASTs.
	//! A `TokenStream` is, roughly speaking, a sequence of [`TokenTree`]s,
	//! which are themselves a single [`Token`] or a `Delimited` subsequence of tokens.
	//!
	//! ## Ownership
	//!
	//! `TokenStream`s are persistent data structures constructed as ropes with reference
	//! counted-children. In general, this means that calling an operation on a `TokenStream`
	//! (such as `slice`) produces an entirely new `TokenStream` from the borrowed reference to
	//! the original. This essentially coerces `TokenStream`s into "views" of their subparts,
	//! and a borrowed `TokenStream` is sufficient to build an owned `TokenStream` without taking
	//! ownership of the original.

	use crate::ast::StmtKind;
	use crate::ast_traits::{HasAttrs, HasSpan, HasTokens};
	use crate::token::{self, Delimiter, Nonterminal, Token, TokenKind};
	use crate::AttrVec;

	use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
	use rustc_data_structures::sync::{self, Lrc};
	use rustc_macros::HashStable_Generic;
	use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
	use rustc_span::{Span, DUMMY_SP};
	use smallvec::{smallvec, SmallVec};

	use std::{fmt, iter};

	/// When the main Rust parser encounters a syntax-extension invocation, it
	/// parses the arguments to the invocation as a token tree. This is a very
	/// loose structure, such that all sorts of different AST fragments can
	/// be passed to syntax extensions using a uniform type.
	///
	/// If the syntax extension is an MBE macro, it will attempt to match its
	/// LHS token tree against the provided token tree, and if it finds a
	/// match, will transcribe the RHS token tree, splicing in any captured
	/// `macro_parser::matched_nonterminals` into the `SubstNt`s it finds.
	///
	/// The RHS of an MBE macro is the only place `SubstNt`s are substituted.
	/// Nothing special happens to misnamed or misplaced `SubstNt`s.
	#[derive(Debug, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
	pub enum TokenTree {
	/// A single token. Should never be `OpenDelim` or `CloseDelim`, because
	/// delimiters are implicitly represented by `Delimited`.
	Token(Token, Spacing),
	/// A delimited sequence of token trees.
	Delimited(DelimSpan, Delimiter, TokenStream),
	}

	// Ensure all fields of `TokenTree` is `Send` and `Sync`.
	#[cfg(parallel_compiler)]
	fn _dummy()
	where
	Token: Send + Sync,
	DelimSpan: Send + Sync,
	Delimiter: Send + Sync,
	TokenStream: Send + Sync,
	{
	}

	impl TokenTree {
	/// Checks if this `TokenTree` is equal to the other, regardless of span information.
	pub fn eq_unspanned(&self, other: &TokenTree) -> bool {
	match (self, other) {
	(TokenTree::Token(token, _), TokenTree::Token(token2, _)) => token.kind == token2.kind,
	(TokenTree::Delimited(_, delim, tts), TokenTree::Delimited(_, delim2, tts2)) => {
	delim == delim2 && tts.eq_unspanned(tts2)
	}
	_ => false,
	}
	}

	/// Retrieves the `TokenTree`'s span.
	pub fn span(&self) -> Span {
	match self {
	TokenTree::Token(token, _) => token.span,
	TokenTree::Delimited(sp, ..) => sp.entire(),
	}
	}

	/// Modify the `TokenTree`'s span in-place.
	pub fn set_span(&mut self, span: Span) {
	match self {
	TokenTree::Token(token, _) => token.span = span,
	TokenTree::Delimited(dspan, ..) => *dspan = DelimSpan::from_single(span),
	}
	}

	/// Create a `TokenTree::Token` with alone spacing.
	pub fn token_alone(kind: TokenKind, span: Span) -> TokenTree {
	TokenTree::Token(Token::new(kind, span), Spacing::Alone)
	}

	/// Create a `TokenTree::Token` with joint spacing.
	pub fn token_joint(kind: TokenKind, span: Span) -> TokenTree {
	TokenTree::Token(Token::new(kind, span), Spacing::Joint)
	}

	pub fn uninterpolate(self) -> TokenTree {
	match self {
	TokenTree::Token(token, spacing) => {
	TokenTree::Token(token.uninterpolate().into_owned(), spacing)
	}
	tt => tt,
	}
	}
	}

	impl<CTX> HashStable<CTX> for TokenStream
	where
	CTX: crate::HashStableContext,
	{
	fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
	for sub_tt in self.trees() {
	sub_tt.hash_stable(hcx, hasher);
	}
	}
	}

	pub trait ToAttrTokenStream: sync::Send + sync::Sync {
	fn to_attr_token_stream(&self) -> AttrTokenStream;
	}

	impl ToAttrTokenStream for AttrTokenStream {
	fn to_attr_token_stream(&self) -> AttrTokenStream {
	self.clone()
	}
	}

	/// A lazy version of [`TokenStream`], which defers creation
	/// of an actual `TokenStream` until it is needed.
	/// `Box` is here only to reduce the structure size.
	#[derive(Clone)]
	pub struct LazyAttrTokenStream(Lrc<Box<dyn ToAttrTokenStream>>);

	impl LazyAttrTokenStream {
	pub fn new(inner: impl ToAttrTokenStream + 'static) -> LazyAttrTokenStream {
	LazyAttrTokenStream(Lrc::new(Box::new(inner)))
	}

	pub fn to_attr_token_stream(&self) -> AttrTokenStream {
	self.0.to_attr_token_stream()
	}
	}

	impl fmt::Debug for LazyAttrTokenStream {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	write!(f, "LazyAttrTokenStream({:?})", self.to_attr_token_stream())
	}
	}

	impl<S: Encoder> Encodable<S> for LazyAttrTokenStream {
	fn encode(&self, s: &mut S) {
	// Used by AST json printing.
	Encodable::encode(&self.to_attr_token_stream(), s);
	}
	}

	impl<D: Decoder> Decodable<D> for LazyAttrTokenStream {
	fn decode(_d: &mut D) -> Self {
	panic!("Attempted to decode LazyAttrTokenStream");
	}
	}

	impl<CTX> HashStable<CTX> for LazyAttrTokenStream {
	fn hash_stable(&self, _hcx: &mut CTX, _hasher: &mut StableHasher) {
	panic!("Attempted to compute stable hash for LazyAttrTokenStream");
	}
	}

	/// An `AttrTokenStream` is similar to a `TokenStream`, but with extra
	/// information about the tokens for attribute targets. This is used
	/// during expansion to perform early cfg-expansion, and to process attributes
	/// during proc-macro invocations.
	#[derive(Clone, Debug, Default, Encodable, Decodable)]
	pub struct AttrTokenStream(pub Lrc<Vec<AttrTokenTree>>);

	/// Like `TokenTree`, but for `AttrTokenStream`.
	#[derive(Clone, Debug, Encodable, Decodable)]
	pub enum AttrTokenTree {
	Token(Token, Spacing),
	Delimited(DelimSpan, Delimiter, AttrTokenStream),
	/// Stores the attributes for an attribute target,
	/// along with the tokens for that attribute target.
	/// See `AttributesData` for more information
	Attributes(AttributesData),
	}

	impl AttrTokenStream {
	pub fn new(tokens: Vec<AttrTokenTree>) -> AttrTokenStream {
	AttrTokenStream(Lrc::new(tokens))
	}

	/// Converts this `AttrTokenStream` to a plain `TokenStream`.
	/// During conversion, `AttrTokenTree::Attributes` get 'flattened'
	/// back to a `TokenStream` of the form `outer_attr attr_target`.
	/// If there are inner attributes, they are inserted into the proper
	/// place in the attribute target tokens.
	pub fn to_tokenstream(&self) -> TokenStream {
	let trees: Vec<_> = self
	.0
	.iter()
	.flat_map(\|tree\| match &tree {
	AttrTokenTree::Token(inner, spacing) => {
	smallvec![TokenTree::Token(inner.clone(), *spacing)].into_iter()
	}
	AttrTokenTree::Delimited(span, delim, stream) => {
	smallvec![TokenTree::Delimited(span, delim, stream.to_tokenstream()),]
	.into_iter()
	}
	AttrTokenTree::Attributes(data) => {
	let mut outer_attrs = Vec::new();
	let mut inner_attrs = Vec::new();
	for attr in &data.attrs {
	match attr.style {
	crate::AttrStyle::Outer => outer_attrs.push(attr),
	crate::AttrStyle::Inner => inner_attrs.push(attr),
	}
	}

	let mut target_tokens: Vec<_> = data
	.tokens
	.to_attr_token_stream()
	.to_tokenstream()
	.0
	.iter()
	.cloned()
	.collect();
	if !inner_attrs.is_empty() {
	let mut found = false;
	// Check the last two trees (to account for a trailing semi)
	for tree in target_tokens.iter_mut().rev().take(2) {
	if let TokenTree::Delimited(span, delim, delim_tokens) = tree {
	// Inner attributes are only supported on extern blocks, functions,
	// impls, and modules. All of these have their inner attributes
	// placed at the beginning of the rightmost outermost braced group:
	// e.g. fn foo() { #![my_attr} }
	//
	// Therefore, we can insert them back into the right location
	// without needing to do any extra position tracking.
	//
	// Note: Outline modules are an exception - they can
	// have attributes like `#![my_attr]` at the start of a file.
	// Support for custom attributes in this position is not
	// properly implemented - we always synthesize fake tokens,
	// so we never reach this code.

	let mut stream = TokenStream::default();
	for inner_attr in inner_attrs {
	stream.push_stream(inner_attr.tokens());
	}
	stream.push_stream(delim_tokens.clone());
	tree = TokenTree::Delimited(span, *delim, stream);
	found = true;
	break;
	}
	}

	assert!(
	found,
	"Failed to find trailing delimited group in: {target_tokens:?}"
	);
	}
	let mut flat: SmallVec<[_; 1]> = SmallVec::new();
	for attr in outer_attrs {
	// FIXME: Make this more efficient
	flat.extend(attr.tokens().0.clone().iter().cloned());
	}
	flat.extend(target_tokens);
	flat.into_iter()
	}
	})
	.collect();
	TokenStream::new(trees)
	}
	}

	/// Stores the tokens for an attribute target, along
	/// with its attributes.
	///
	/// This is constructed during parsing when we need to capture
	/// tokens.
	///
	/// For example, `#[cfg(FALSE)] struct Foo {}` would
	/// have an `attrs` field containing the `#[cfg(FALSE)]` attr,
	/// and a `tokens` field storing the (unparsed) tokens `struct Foo {}`
	#[derive(Clone, Debug, Encodable, Decodable)]
	pub struct AttributesData {
	/// Attributes, both outer and inner.
	/// These are stored in the original order that they were parsed in.
	pub attrs: AttrVec,
	/// The underlying tokens for the attribute target that `attrs`
	/// are applied to
	pub tokens: LazyAttrTokenStream,
	}

	/// A `TokenStream` is an abstract sequence of tokens, organized into [`TokenTree`]s.
	///
	/// The goal is for procedural macros to work with `TokenStream`s and `TokenTree`s
	/// instead of a representation of the abstract syntax tree.
	/// Today's `TokenTree`s can still contain AST via `token::Interpolated` for
	/// backwards compatibility.
	#[derive(Clone, Debug, Default, Encodable, Decodable)]
	pub struct TokenStream(pub(crate) Lrc<Vec<TokenTree>>);

	/// Similar to `proc_macro::Spacing`, but for tokens.
	///
	/// Note that all `ast::TokenTree::Token` instances have a `Spacing`, but when
	/// we convert to `proc_macro::TokenTree` for proc macros only `Punct`
	/// `TokenTree`s have a `proc_macro::Spacing`.
	#[derive(Clone, Copy, Debug, PartialEq, Encodable, Decodable, HashStable_Generic)]
	pub enum Spacing {
	/// The token is not immediately followed by an operator token (as
	/// determined by `Token::is_op`). E.g. a `+` token is `Alone` in `+ =`,
	/// `+/foo/=`, `+ident`, and `+()`.
	Alone,

	/// The token is immediately followed by an operator token. E.g. a `+`
	/// token is `Joint` in `+=` and `++`.
	Joint,
	}

	impl TokenStream {
	/// Given a `TokenStream` with a `Stream` of only two arguments, return a new `TokenStream`
	/// separating the two arguments with a comma for diagnostic suggestions.
	pub fn add_comma(&self) -> Option<(TokenStream, Span)> {
	// Used to suggest if a user writes `foo!(a b);`
	let mut suggestion = None;
	let mut iter = self.0.iter().enumerate().peekable();
	while let Some((pos, ts)) = iter.next() {
	if let Some((_, next)) = iter.peek() {
	let sp = match (&ts, &next) {
	(_, TokenTree::Token(Token { kind: token::Comma, .. }, _)) => continue,
	(
	TokenTree::Token(token_left, Spacing::Alone),
	TokenTree::Token(token_right, _),
	) if ((token_left.is_ident() && !token_left.is_reserved_ident())
	\|\| token_left.is_lit())
	&& ((token_right.is_ident() && !token_right.is_reserved_ident())
	\|\| token_right.is_lit()) =>
	{
	token_left.span
	}
	(TokenTree::Delimited(sp, ..), _) => sp.entire(),
	_ => continue,
	};
	let sp = sp.shrink_to_hi();
	let comma = TokenTree::token_alone(token::Comma, sp);
	suggestion = Some((pos, comma, sp));
	}
	}
	if let Some((pos, comma, sp)) = suggestion {
	let mut new_stream = Vec::with_capacity(self.0.len() + 1);
	let parts = self.0.split_at(pos + 1);
	new_stream.extend_from_slice(parts.0);
	new_stream.push(comma);
	new_stream.extend_from_slice(parts.1);
	return Some((TokenStream::new(new_stream), sp));
	}
	None
	}
	}

	impl FromIterator<TokenTree> for TokenStream {
	fn from_iter<I: IntoIterator<Item = TokenTree>>(iter: I) -> Self {
	TokenStream::new(iter.into_iter().collect::<Vec<TokenTree>>())
	}
	}

	impl Eq for TokenStream {}

	impl PartialEq<TokenStream> for TokenStream {
	fn eq(&self, other: &TokenStream) -> bool {
	self.trees().eq(other.trees())
	}
	}

	impl TokenStream {
	pub fn new(streams: Vec<TokenTree>) -> TokenStream {
	TokenStream(Lrc::new(streams))
	}

	pub fn is_empty(&self) -> bool {
	self.0.is_empty()
	}

	pub fn len(&self) -> usize {
	self.0.len()
	}

	pub fn trees(&self) -> RefTokenTreeCursor<'_> {
	RefTokenTreeCursor::new(self)
	}

	pub fn into_trees(self) -> TokenTreeCursor {
	TokenTreeCursor::new(self)
	}

	/// Compares two `TokenStream`s, checking equality without regarding span information.
	pub fn eq_unspanned(&self, other: &TokenStream) -> bool {
	let mut t1 = self.trees();
	let mut t2 = other.trees();
	for (t1, t2) in iter::zip(&mut t1, &mut t2) {
	if !t1.eq_unspanned(t2) {
	return false;
	}
	}
	t1.next().is_none() && t2.next().is_none()
	}

	pub fn map_enumerated<F: FnMut(usize, &TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream {
	TokenStream(Lrc::new(self.0.iter().enumerate().map(\|(i, tree)\| f(i, tree)).collect()))
	}

	/// Create a token stream containing a single token with alone spacing.
	pub fn token_alone(kind: TokenKind, span: Span) -> TokenStream {
	TokenStream::new(vec![TokenTree::token_alone(kind, span)])
	}

	/// Create a token stream containing a single token with joint spacing.
	pub fn token_joint(kind: TokenKind, span: Span) -> TokenStream {
	TokenStream::new(vec![TokenTree::token_joint(kind, span)])
	}

	/// Create a token stream containing a single `Delimited`.
	pub fn delimited(span: DelimSpan, delim: Delimiter, tts: TokenStream) -> TokenStream {
	TokenStream::new(vec![TokenTree::Delimited(span, delim, tts)])
	}

	pub fn from_ast(node: &(impl HasAttrs + HasSpan + HasTokens + fmt::Debug)) -> TokenStream {
	let Some(tokens) = node.tokens() else {
	panic!("missing tokens for node at {:?}: {:?}", node.span(), node);
	};
	let attrs = node.attrs();
	let attr_stream = if attrs.is_empty() {
	tokens.to_attr_token_stream()
	} else {
	let attr_data =
	AttributesData { attrs: attrs.iter().cloned().collect(), tokens: tokens.clone() };
	AttrTokenStream::new(vec![AttrTokenTree::Attributes(attr_data)])
	};
	attr_stream.to_tokenstream()
	}

	pub fn from_nonterminal_ast(nt: &Nonterminal) -> TokenStream {
	match nt {
	Nonterminal::NtIdent(ident, is_raw) => {
	TokenStream::token_alone(token::Ident(ident.name, *is_raw), ident.span)
	}
	Nonterminal::NtLifetime(ident) => {
	TokenStream::token_alone(token::Lifetime(ident.name), ident.span)
	}
	Nonterminal::NtItem(item) => TokenStream::from_ast(item),
	Nonterminal::NtBlock(block) => TokenStream::from_ast(block),
	Nonterminal::NtStmt(stmt) if let StmtKind::Empty = stmt.kind => {
	// FIXME: Properly collect tokens for empty statements.
	TokenStream::token_alone(token::Semi, stmt.span)
	}
	Nonterminal::NtStmt(stmt) => TokenStream::from_ast(stmt),
	Nonterminal::NtPat(pat) => TokenStream::from_ast(pat),
	Nonterminal::NtTy(ty) => TokenStream::from_ast(ty),
	Nonterminal::NtMeta(attr) => TokenStream::from_ast(attr),
	Nonterminal::NtPath(path) => TokenStream::from_ast(path),
	Nonterminal::NtVis(vis) => TokenStream::from_ast(vis),
	Nonterminal::NtExpr(expr) \| Nonterminal::NtLiteral(expr) => TokenStream::from_ast(expr),
	}
	}

	fn flatten_token(token: &Token, spacing: Spacing) -> TokenTree {
	match &token.kind {
	token::Interpolated(nt) if let token::NtIdent(ident, is_raw) = **nt => {
	TokenTree::Token(Token::new(token::Ident(ident.name, is_raw), ident.span), spacing)
	}
	token::Interpolated(nt) => TokenTree::Delimited(
	DelimSpan::from_single(token.span),
	Delimiter::Invisible,
	TokenStream::from_nonterminal_ast(nt).flattened(),
	),
	_ => TokenTree::Token(token.clone(), spacing),
	}
	}

	fn flatten_token_tree(tree: &TokenTree) -> TokenTree {
	match tree {
	TokenTree::Token(token, spacing) => TokenStream::flatten_token(token, *spacing),
	TokenTree::Delimited(span, delim, tts) => {
	TokenTree::Delimited(span, delim, tts.flattened())
	}
	}
	}

	#[must_use]
	pub fn flattened(&self) -> TokenStream {
	fn can_skip(stream: &TokenStream) -> bool {
	stream.trees().all(\|tree\| match tree {
	TokenTree::Token(token, _) => !matches!(token.kind, token::Interpolated(_)),
	TokenTree::Delimited(_, _, inner) => can_skip(inner),
	})
	}

	if can_skip(self) {
	return self.clone();
	}

	self.trees().map(\|tree\| TokenStream::flatten_token_tree(tree)).collect()
	}

	// If `vec` is not empty, try to glue `tt` onto its last token. The return
	// value indicates if gluing took place.
	fn try_glue_to_last(vec: &mut Vec<TokenTree>, tt: &TokenTree) -> bool {
	if let Some(TokenTree::Token(last_tok, Spacing::Joint)) = vec.last()
	&& let TokenTree::Token(tok, spacing) = tt
	&& let Some(glued_tok) = last_tok.glue(tok)
	{
	// ...then overwrite the last token tree in `vec` with the
	// glued token, and skip the first token tree from `stream`.
	vec.last_mut().unwrap() = TokenTree::Token(glued_tok, spacing);
	true
	} else {
	false
	}
	}

	/// Push `tt` onto the end of the stream, possibly gluing it to the last
	/// token. Uses `make_mut` to maximize efficiency.
	pub fn push_tree(&mut self, tt: TokenTree) {
	let vec_mut = Lrc::make_mut(&mut self.0);

	if Self::try_glue_to_last(vec_mut, &tt) {
	// nothing else to do
	} else {
	vec_mut.push(tt);
	}
	}

	/// Push `stream` onto the end of the stream, possibly gluing the first
	/// token tree to the last token. (No other token trees will be glued.)
	/// Uses `make_mut` to maximize efficiency.
	pub fn push_stream(&mut self, stream: TokenStream) {
	let vec_mut = Lrc::make_mut(&mut self.0);

	let stream_iter = stream.0.iter().cloned();

	if let Some(first) = stream.0.first() && Self::try_glue_to_last(vec_mut, first) {
	// Now skip the first token tree from `stream`.
	vec_mut.extend(stream_iter.skip(1));
	} else {
	// Append all of `stream`.
	vec_mut.extend(stream_iter);
	}
	}
	}

	/// By-reference iterator over a [`TokenStream`], that produces `&TokenTree`
	/// items.
	#[derive(Clone)]
	pub struct RefTokenTreeCursor<'t> {
	stream: &'t TokenStream,
	index: usize,
	}

	impl<'t> RefTokenTreeCursor<'t> {
	fn new(stream: &'t TokenStream) -> Self {
	RefTokenTreeCursor { stream, index: 0 }
	}

	pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
	self.stream.0.get(self.index + n)
	}
	}

	impl<'t> Iterator for RefTokenTreeCursor<'t> {
	type Item = &'t TokenTree;

	fn next(&mut self) -> Option<&'t TokenTree> {
	self.stream.0.get(self.index).map(\|tree\| {
	self.index += 1;
	tree
	})
	}
	}

	/// Owning by-value iterator over a [`TokenStream`], that produces `TokenTree`
	/// items.
	// FIXME: Many uses of this can be replaced with by-reference iterator to avoid clones.
	#[derive(Clone)]
	pub struct TokenTreeCursor {
	pub stream: TokenStream,
	index: usize,
	}

	impl Iterator for TokenTreeCursor {
	type Item = TokenTree;

	fn next(&mut self) -> Option<TokenTree> {
	self.stream.0.get(self.index).map(\|tree\| {
	self.index += 1;
	tree.clone()
	})
	}
	}

	impl TokenTreeCursor {
	fn new(stream: TokenStream) -> Self {
	TokenTreeCursor { stream, index: 0 }
	}

	#[inline]
	pub fn next_ref(&mut self) -> Option<&TokenTree> {
	self.stream.0.get(self.index).map(\|tree\| {
	self.index += 1;
	tree
	})
	}

	pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
	self.stream.0.get(self.index + n)
	}

	// Replace the previously obtained token tree with `tts`, and rewind to
	// just before them.
	pub fn replace_prev_and_rewind(&mut self, tts: Vec<TokenTree>) {
	assert!(self.index > 0);
	self.index -= 1;
	let stream = Lrc::make_mut(&mut self.stream.0);
	stream.splice(self.index..self.index + 1, tts);
	}
	}

	#[derive(Debug, Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
	pub struct DelimSpan {
	pub open: Span,
	pub close: Span,
	}

	impl DelimSpan {
	pub fn from_single(sp: Span) -> Self {
	DelimSpan { open: sp, close: sp }
	}

	pub fn from_pair(open: Span, close: Span) -> Self {
	DelimSpan { open, close }
	}

	pub fn dummy() -> Self {
	Self::from_single(DUMMY_SP)
	}

	pub fn entire(self) -> Span {
	self.open.with_hi(self.close.hi())
	}
	}

	// Some types are used a lot. Make sure they don't unintentionally get bigger.
	#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
	mod size_asserts {
	use super::*;
	use rustc_data_structures::static_assert_size;
	// tidy-alphabetical-start
	static_assert_size!(AttrTokenStream, 8);
	static_assert_size!(AttrTokenTree, 32);
	static_assert_size!(LazyAttrTokenStream, 8);
	static_assert_size!(TokenStream, 8);
	static_assert_size!(TokenTree, 32);
	// tidy-alphabetical-end
	}