1 //! Rustc proc-macro server implementation with tt
3 //! Based on idea from <https://github.com/fedochet/rust-proc-macro-expander>
4 //! The lib-proc-macro server backend is `TokenStream`-agnostic, such that
5 //! we could provide any TokenStream implementation.
6 //! The original idea from fedochet is using proc-macro2 as backend,
7 //! we use tt instead for better integration with RA.
9 //! FIXME: No span and source file information is implemented yet
11 use crate::proc_macro::bridge::{self, server};
13 use std::collections::HashMap;
15 use std::iter::FromIterator;
17 use std::{ascii, vec::IntoIter};
19 type Group = tt::Subtree;
20 type TokenTree = tt::TokenTree;
21 type Punct = tt::Punct;
22 type Spacing = tt::Spacing;
23 type Literal = tt::Literal;
24 type Span = tt::TokenId;
26 #[derive(Debug, Clone)]
27 pub struct TokenStream {
28 pub token_trees: Vec<TokenTree>,
32 pub fn new() -> Self {
33 TokenStream { token_trees: Default::default() }
36 pub fn with_subtree(subtree: tt::Subtree) -> Self {
37 if subtree.delimiter.is_some() {
38 TokenStream { token_trees: vec![TokenTree::Subtree(subtree)] }
40 TokenStream { token_trees: subtree.token_trees }
44 pub fn into_subtree(self) -> tt::Subtree {
45 tt::Subtree { delimiter: None, token_trees: self.token_trees }
48 pub fn is_empty(&self) -> bool {
49 self.token_trees.is_empty()
53 /// Creates a token stream containing a single token tree.
54 impl From<TokenTree> for TokenStream {
55 fn from(tree: TokenTree) -> TokenStream {
56 TokenStream { token_trees: vec![tree] }
60 /// Collects a number of token trees into a single stream.
61 impl FromIterator<TokenTree> for TokenStream {
62 fn from_iter<I: IntoIterator<Item = TokenTree>>(trees: I) -> Self {
63 trees.into_iter().map(TokenStream::from).collect()
67 /// A "flattening" operation on token streams, collects token trees
68 /// from multiple token streams into a single stream.
69 impl FromIterator<TokenStream> for TokenStream {
70 fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self {
71 let mut builder = TokenStreamBuilder::new();
72 streams.into_iter().for_each(|stream| builder.push(stream));
77 impl Extend<TokenTree> for TokenStream {
78 fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, trees: I) {
79 self.extend(trees.into_iter().map(TokenStream::from));
83 impl Extend<TokenStream> for TokenStream {
84 fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I) {
88 tt::TokenTree::Subtree(subtree) if subtree.delimiter.is_none() => {
89 self.token_trees.extend(subtree.token_trees);
92 self.token_trees.push(tkn);
100 type Level = crate::proc_macro::Level;
101 type LineColumn = crate::proc_macro::LineColumn;
102 type SourceFile = crate::proc_macro::SourceFile;
104 /// A structure representing a diagnostic message and associated children
106 #[derive(Clone, Debug)]
107 pub struct Diagnostic {
111 children: Vec<Diagnostic>,
115 /// Creates a new diagnostic with the given `level` and `message`.
116 pub fn new<T: Into<String>>(level: Level, message: T) -> Diagnostic {
117 Diagnostic { level, message: message.into(), spans: vec![], children: vec![] }
121 // Rustc Server Ident has to be `Copyable`
122 // We use a stub here for bypassing
123 #[derive(Hash, Eq, PartialEq, Copy, Clone)]
124 pub struct IdentId(u32);
126 #[derive(Clone, Hash, Eq, PartialEq)]
127 struct IdentData(tt::Ident);
130 struct IdentInterner {
131 idents: HashMap<IdentData, u32>,
132 ident_data: Vec<IdentData>,
136 fn intern(&mut self, data: &IdentData) -> u32 {
137 if let Some(index) = self.idents.get(data) {
141 let index = self.idents.len() as u32;
142 self.ident_data.push(data.clone());
143 self.idents.insert(data.clone(), index);
147 fn get(&self, index: u32) -> &IdentData {
148 &self.ident_data[index as usize]
152 fn get_mut(&mut self, index: u32) -> &mut IdentData {
153 self.ident_data.get_mut(index as usize).expect("Should be consistent")
157 pub struct TokenStreamBuilder {
161 /// Public implementation details for the `TokenStream` type, such as iterators.
162 pub mod token_stream {
163 use std::str::FromStr;
165 use super::{TokenStream, TokenTree};
167 /// An iterator over `TokenStream`'s `TokenTree`s.
168 /// The iteration is "shallow", e.g., the iterator doesn't recurse into delimited groups,
169 /// and returns whole groups as token trees.
170 impl IntoIterator for TokenStream {
171 type Item = TokenTree;
172 type IntoIter = super::IntoIter<TokenTree>;
174 fn into_iter(self) -> Self::IntoIter {
175 self.token_trees.into_iter()
179 type LexError = String;
181 /// Attempts to break the string into tokens and parse those tokens into a token stream.
182 /// May fail for a number of reasons, for example, if the string contains unbalanced delimiters
183 /// or characters not existing in the language.
184 /// All tokens in the parsed stream get `Span::call_site()` spans.
186 /// NOTE: some errors may cause panics instead of returning `LexError`. We reserve the right to
187 /// change these errors into `LexError`s later.
188 impl FromStr for TokenStream {
191 fn from_str(src: &str) -> Result<TokenStream, LexError> {
192 let (subtree, _token_map) =
193 mbe::parse_to_token_tree(src).ok_or("Failed to parse from mbe")?;
195 let subtree = subtree_replace_token_ids_with_unspecified(subtree);
196 Ok(TokenStream::with_subtree(subtree))
200 impl ToString for TokenStream {
201 fn to_string(&self) -> String {
202 return tokentrees_to_text(&self.token_trees[..]);
204 fn tokentrees_to_text(tkns: &[tt::TokenTree]) -> String {
206 .fold((String::new(), true), |(last, last_to_joint), tkn| {
207 let s = [last, tokentree_to_text(tkn)].join(if last_to_joint {
212 let mut is_joint = false;
213 if let tt::TokenTree::Leaf(tt::Leaf::Punct(punct)) = tkn {
214 if punct.spacing == tt::Spacing::Joint {
223 fn tokentree_to_text(tkn: &tt::TokenTree) -> String {
225 tt::TokenTree::Leaf(tt::Leaf::Ident(ident)) => ident.text.clone().into(),
226 tt::TokenTree::Leaf(tt::Leaf::Literal(literal)) => literal.text.clone().into(),
227 tt::TokenTree::Leaf(tt::Leaf::Punct(punct)) => format!("{}", punct.char),
228 tt::TokenTree::Subtree(subtree) => {
229 let content = tokentrees_to_text(&subtree.token_trees);
230 let (open, close) = match subtree.delimiter.map(|it| it.kind) {
232 Some(tt::DelimiterKind::Brace) => ("{", "}"),
233 Some(tt::DelimiterKind::Parenthesis) => ("(", ")"),
234 Some(tt::DelimiterKind::Bracket) => ("[", "]"),
236 format!("{}{}{}", open, content, close)
243 fn subtree_replace_token_ids_with_unspecified(subtree: tt::Subtree) -> tt::Subtree {
247 .map(|d| tt::Delimiter { id: tt::TokenId::unspecified(), ..d }),
251 .map(|t| token_tree_replace_token_ids_with_unspecified(t))
256 fn token_tree_replace_token_ids_with_unspecified(tt: tt::TokenTree) -> tt::TokenTree {
258 tt::TokenTree::Leaf(leaf) => {
259 tt::TokenTree::Leaf(leaf_replace_token_ids_with_unspecified(leaf))
261 tt::TokenTree::Subtree(subtree) => {
262 tt::TokenTree::Subtree(subtree_replace_token_ids_with_unspecified(subtree))
267 fn leaf_replace_token_ids_with_unspecified(leaf: tt::Leaf) -> tt::Leaf {
269 tt::Leaf::Literal(lit) => {
270 tt::Leaf::Literal(tt::Literal { id: tt::TokenId::unspecified(), ..lit })
272 tt::Leaf::Punct(punct) => {
273 tt::Leaf::Punct(tt::Punct { id: tt::TokenId::unspecified(), ..punct })
275 tt::Leaf::Ident(ident) => {
276 tt::Leaf::Ident(tt::Ident { id: tt::TokenId::unspecified(), ..ident })
282 impl TokenStreamBuilder {
283 fn new() -> TokenStreamBuilder {
284 TokenStreamBuilder { acc: TokenStream::new() }
287 fn push(&mut self, stream: TokenStream) {
288 self.acc.extend(stream.into_iter())
291 fn build(self) -> TokenStream {
296 pub struct FreeFunctions;
299 pub struct TokenStreamIter {
300 trees: IntoIter<TokenTree>,
305 ident_interner: IdentInterner,
306 // FIXME: store span information here.
309 impl server::Types for Rustc {
310 type FreeFunctions = FreeFunctions;
311 type TokenStream = TokenStream;
312 type TokenStreamBuilder = TokenStreamBuilder;
313 type TokenStreamIter = TokenStreamIter;
316 type Ident = IdentId;
317 type Literal = Literal;
318 type SourceFile = SourceFile;
319 type Diagnostic = Diagnostic;
321 type MultiSpan = Vec<Span>;
324 impl server::FreeFunctions for Rustc {
325 fn track_env_var(&mut self, _var: &str, _value: Option<&str>) {
326 // FIXME: track env var accesses
327 // https://github.com/rust-lang/rust/pull/71858
331 impl server::TokenStream for Rustc {
332 fn new(&mut self) -> Self::TokenStream {
333 Self::TokenStream::new()
336 fn is_empty(&mut self, stream: &Self::TokenStream) -> bool {
339 fn from_str(&mut self, src: &str) -> Self::TokenStream {
340 use std::str::FromStr;
342 Self::TokenStream::from_str(src).expect("cannot parse string")
344 fn to_string(&mut self, stream: &Self::TokenStream) -> String {
349 tree: bridge::TokenTree<Self::Group, Self::Punct, Self::Ident, Self::Literal>,
350 ) -> Self::TokenStream {
352 bridge::TokenTree::Group(group) => {
353 let tree = TokenTree::from(group);
354 Self::TokenStream::from_iter(vec![tree])
357 bridge::TokenTree::Ident(IdentId(index)) => {
358 let IdentData(ident) = self.ident_interner.get(index).clone();
359 let ident: tt::Ident = ident;
360 let leaf = tt::Leaf::from(ident);
361 let tree = TokenTree::from(leaf);
362 Self::TokenStream::from_iter(vec![tree])
365 bridge::TokenTree::Literal(literal) => {
366 let leaf = tt::Leaf::from(literal);
367 let tree = TokenTree::from(leaf);
368 Self::TokenStream::from_iter(vec![tree])
371 bridge::TokenTree::Punct(p) => {
372 let leaf = tt::Leaf::from(p);
373 let tree = TokenTree::from(leaf);
374 Self::TokenStream::from_iter(vec![tree])
379 fn into_iter(&mut self, stream: Self::TokenStream) -> Self::TokenStreamIter {
380 let trees: Vec<TokenTree> = stream.into_iter().collect();
381 TokenStreamIter { trees: trees.into_iter() }
385 impl server::TokenStreamBuilder for Rustc {
386 fn new(&mut self) -> Self::TokenStreamBuilder {
387 Self::TokenStreamBuilder::new()
389 fn push(&mut self, builder: &mut Self::TokenStreamBuilder, stream: Self::TokenStream) {
392 fn build(&mut self, builder: Self::TokenStreamBuilder) -> Self::TokenStream {
397 impl server::TokenStreamIter for Rustc {
400 iter: &mut Self::TokenStreamIter,
401 ) -> Option<bridge::TokenTree<Self::Group, Self::Punct, Self::Ident, Self::Literal>> {
402 iter.trees.next().map(|tree| match tree {
403 TokenTree::Subtree(group) => bridge::TokenTree::Group(group),
404 TokenTree::Leaf(tt::Leaf::Ident(ident)) => {
405 bridge::TokenTree::Ident(IdentId(self.ident_interner.intern(&IdentData(ident))))
407 TokenTree::Leaf(tt::Leaf::Literal(literal)) => bridge::TokenTree::Literal(literal),
408 TokenTree::Leaf(tt::Leaf::Punct(punct)) => bridge::TokenTree::Punct(punct),
413 fn delim_to_internal(d: bridge::Delimiter) -> Option<tt::Delimiter> {
415 bridge::Delimiter::Parenthesis => tt::DelimiterKind::Parenthesis,
416 bridge::Delimiter::Brace => tt::DelimiterKind::Brace,
417 bridge::Delimiter::Bracket => tt::DelimiterKind::Bracket,
418 bridge::Delimiter::None => return None,
420 Some(tt::Delimiter { id: tt::TokenId::unspecified(), kind })
423 fn delim_to_external(d: Option<tt::Delimiter>) -> bridge::Delimiter {
424 match d.map(|it| it.kind) {
425 Some(tt::DelimiterKind::Parenthesis) => bridge::Delimiter::Parenthesis,
426 Some(tt::DelimiterKind::Brace) => bridge::Delimiter::Brace,
427 Some(tt::DelimiterKind::Bracket) => bridge::Delimiter::Bracket,
428 None => bridge::Delimiter::None,
432 fn spacing_to_internal(spacing: bridge::Spacing) -> Spacing {
434 bridge::Spacing::Alone => Spacing::Alone,
435 bridge::Spacing::Joint => Spacing::Joint,
439 fn spacing_to_external(spacing: Spacing) -> bridge::Spacing {
441 Spacing::Alone => bridge::Spacing::Alone,
442 Spacing::Joint => bridge::Spacing::Joint,
446 impl server::Group for Rustc {
447 fn new(&mut self, delimiter: bridge::Delimiter, stream: Self::TokenStream) -> Self::Group {
448 Self::Group { delimiter: delim_to_internal(delimiter), token_trees: stream.token_trees }
450 fn delimiter(&mut self, group: &Self::Group) -> bridge::Delimiter {
451 delim_to_external(group.delimiter)
454 // NOTE: Return value of do not include delimiter
455 fn stream(&mut self, group: &Self::Group) -> Self::TokenStream {
456 TokenStream { token_trees: group.token_trees.clone() }
459 fn span(&mut self, group: &Self::Group) -> Self::Span {
460 group.delimiter.map(|it| it.id).unwrap_or_else(|| tt::TokenId::unspecified())
463 fn set_span(&mut self, _group: &mut Self::Group, _span: Self::Span) {
467 fn span_open(&mut self, _group: &Self::Group) -> Self::Span {
469 // MySpan(self.span_interner.intern(&MySpanData(group.span_open())))
470 tt::TokenId::unspecified()
473 fn span_close(&mut self, _group: &Self::Group) -> Self::Span {
475 tt::TokenId::unspecified()
479 impl server::Punct for Rustc {
480 fn new(&mut self, ch: char, spacing: bridge::Spacing) -> Self::Punct {
483 spacing: spacing_to_internal(spacing),
484 id: tt::TokenId::unspecified(),
487 fn as_char(&mut self, punct: Self::Punct) -> char {
490 fn spacing(&mut self, punct: Self::Punct) -> bridge::Spacing {
491 spacing_to_external(punct.spacing)
493 fn span(&mut self, _punct: Self::Punct) -> Self::Span {
495 tt::TokenId::unspecified()
497 fn with_span(&mut self, punct: Self::Punct, _span: Self::Span) -> Self::Punct {
503 impl server::Ident for Rustc {
504 fn new(&mut self, string: &str, _span: Self::Span, _is_raw: bool) -> Self::Ident {
506 self.ident_interner.intern(&IdentData(tt::Ident {
508 id: tt::TokenId::unspecified(),
513 fn span(&mut self, _ident: Self::Ident) -> Self::Span {
515 tt::TokenId::unspecified()
517 fn with_span(&mut self, ident: Self::Ident, _span: Self::Span) -> Self::Ident {
523 impl server::Literal for Rustc {
524 fn debug_kind(&mut self, _literal: &Self::Literal) -> String {
525 // r-a: debug_kind and suffix are unsupported; corresponding client code has been changed to not call these.
526 // They must still be present to be ABI-compatible and work with upstream proc_macro.
529 fn symbol(&mut self, literal: &Self::Literal) -> String {
530 literal.text.to_string()
532 fn suffix(&mut self, _literal: &Self::Literal) -> Option<String> {
536 fn integer(&mut self, n: &str) -> Self::Literal {
537 let n = if let Ok(n) = n.parse::<i128>() {
540 n.parse::<u128>().unwrap().to_string()
542 Literal { text: n.into(), id: tt::TokenId::unspecified() }
545 fn typed_integer(&mut self, n: &str, kind: &str) -> Self::Literal {
546 macro_rules! def_suffixed_integer {
547 ($kind:ident, $($ty:ty),*) => {
551 let n: $ty = n.parse().unwrap();
552 format!(concat!("{}", stringify!($ty)), n)
555 _ => unimplemented!("unknown args for typed_integer: n {}, kind {}", n, $kind),
560 let text = def_suffixed_integer! {kind, u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize};
562 Literal { text: text.into(), id: tt::TokenId::unspecified() }
565 fn float(&mut self, n: &str) -> Self::Literal {
566 let n: f64 = n.parse().unwrap();
567 let mut text = f64::to_string(&n);
568 if !text.contains('.') {
571 Literal { text: text.into(), id: tt::TokenId::unspecified() }
574 fn f32(&mut self, n: &str) -> Self::Literal {
575 let n: f32 = n.parse().unwrap();
576 let text = format!("{}f32", n);
577 Literal { text: text.into(), id: tt::TokenId::unspecified() }
580 fn f64(&mut self, n: &str) -> Self::Literal {
581 let n: f64 = n.parse().unwrap();
582 let text = format!("{}f64", n);
583 Literal { text: text.into(), id: tt::TokenId::unspecified() }
586 fn string(&mut self, string: &str) -> Self::Literal {
587 let mut escaped = String::new();
588 for ch in string.chars() {
589 escaped.extend(ch.escape_debug());
591 Literal { text: format!("\"{}\"", escaped).into(), id: tt::TokenId::unspecified() }
594 fn character(&mut self, ch: char) -> Self::Literal {
595 Literal { text: format!("'{}'", ch).into(), id: tt::TokenId::unspecified() }
598 fn byte_string(&mut self, bytes: &[u8]) -> Self::Literal {
602 .flat_map(ascii::escape_default)
603 .map(Into::<char>::into)
604 .collect::<String>();
606 Literal { text: format!("b\"{}\"", string).into(), id: tt::TokenId::unspecified() }
609 fn span(&mut self, literal: &Self::Literal) -> Self::Span {
613 fn set_span(&mut self, _literal: &mut Self::Literal, _span: Self::Span) {
619 _literal: &Self::Literal,
620 _start: Bound<usize>,
622 ) -> Option<Self::Span> {
628 impl server::SourceFile for Rustc {
629 fn eq(&mut self, file1: &Self::SourceFile, file2: &Self::SourceFile) -> bool {
632 fn path(&mut self, file: &Self::SourceFile) -> String {
634 file.path().to_str().expect("non-UTF8 file path in `proc_macro::SourceFile::path`"),
637 fn is_real(&mut self, file: &Self::SourceFile) -> bool {
642 impl server::Diagnostic for Rustc {
643 fn new(&mut self, level: Level, msg: &str, spans: Self::MultiSpan) -> Self::Diagnostic {
644 let mut diag = Diagnostic::new(level, msg);
651 _diag: &mut Self::Diagnostic,
654 _spans: Self::MultiSpan,
656 // FIXME handle diagnostic
660 fn emit(&mut self, _diag: Self::Diagnostic) {
661 // FIXME handle diagnostic
666 impl server::Span for Rustc {
667 fn debug(&mut self, span: Self::Span) -> String {
668 format!("{:?}", span.0)
670 fn def_site(&mut self) -> Self::Span {
671 // MySpan(self.span_interner.intern(&MySpanData(Span::def_site())))
673 tt::TokenId::unspecified()
675 fn call_site(&mut self) -> Self::Span {
676 // MySpan(self.span_interner.intern(&MySpanData(Span::call_site())))
678 tt::TokenId::unspecified()
680 fn source_file(&mut self, _span: Self::Span) -> Self::SourceFile {
681 // let MySpanData(span) = self.span_interner.get(span.0);
685 /// Recent feature, not yet in the proc_macro
688 /// https://github.com/rust-lang/rust/pull/55780
689 fn source_text(&mut self, _span: Self::Span) -> Option<String> {
693 fn parent(&mut self, _span: Self::Span) -> Option<Self::Span> {
697 fn source(&mut self, span: Self::Span) -> Self::Span {
701 fn start(&mut self, _span: Self::Span) -> LineColumn {
703 LineColumn { line: 0, column: 0 }
705 fn end(&mut self, _span: Self::Span) -> LineColumn {
707 LineColumn { line: 0, column: 0 }
709 fn join(&mut self, _first: Self::Span, _second: Self::Span) -> Option<Self::Span> {
712 fn resolved_at(&mut self, _span: Self::Span, _at: Self::Span) -> Self::Span {
714 tt::TokenId::unspecified()
717 fn mixed_site(&mut self) -> Self::Span {
719 tt::TokenId::unspecified()
723 impl server::MultiSpan for Rustc {
724 fn new(&mut self) -> Self::MultiSpan {
729 fn push(&mut self, other: &mut Self::MultiSpan, span: Self::Span) {
738 use crate::proc_macro::bridge::server::Literal;
741 fn test_rustc_server_literals() {
742 let mut srv = Rustc { ident_interner: IdentInterner::default() };
743 assert_eq!(srv.integer("1234").text, "1234");
745 assert_eq!(srv.typed_integer("12", "u8").text, "12u8");
746 assert_eq!(srv.typed_integer("255", "u16").text, "255u16");
747 assert_eq!(srv.typed_integer("1234", "u32").text, "1234u32");
748 assert_eq!(srv.typed_integer("15846685", "u64").text, "15846685u64");
749 assert_eq!(srv.typed_integer("15846685258", "u128").text, "15846685258u128");
750 assert_eq!(srv.typed_integer("156788984", "usize").text, "156788984usize");
751 assert_eq!(srv.typed_integer("127", "i8").text, "127i8");
752 assert_eq!(srv.typed_integer("255", "i16").text, "255i16");
753 assert_eq!(srv.typed_integer("1234", "i32").text, "1234i32");
754 assert_eq!(srv.typed_integer("15846685", "i64").text, "15846685i64");
755 assert_eq!(srv.typed_integer("15846685258", "i128").text, "15846685258i128");
756 assert_eq!(srv.float("0").text, "0.0");
757 assert_eq!(srv.float("15684.5867").text, "15684.5867");
758 assert_eq!(srv.f32("15684.58").text, "15684.58f32");
759 assert_eq!(srv.f64("15684.58").text, "15684.58f64");
761 assert_eq!(srv.string("hello_world").text, "\"hello_world\"");
762 assert_eq!(srv.character('c').text, "'c'");
763 assert_eq!(srv.byte_string(b"1234586\x88").text, "b\"1234586\\x88\"");
767 srv.integer("340282366920938463463374607431768211455").text,
768 "340282366920938463463374607431768211455"
772 srv.integer("-170141183460469231731687303715884105728").text,
773 "-170141183460469231731687303715884105728"
778 fn test_rustc_server_to_string() {
779 let s = TokenStream {
781 tt::TokenTree::Leaf(tt::Leaf::Ident(tt::Ident {
782 text: "struct".into(),
783 id: tt::TokenId::unspecified(),
785 tt::TokenTree::Leaf(tt::Leaf::Ident(tt::Ident {
787 id: tt::TokenId::unspecified(),
789 tt::TokenTree::Subtree(tt::Subtree {
790 delimiter: Some(tt::Delimiter {
791 id: tt::TokenId::unspecified(),
792 kind: tt::DelimiterKind::Brace,
799 assert_eq!(s.to_string(), "struct T {}");
803 fn test_rustc_server_from_str() {
804 use std::str::FromStr;
805 let subtree_paren_a = tt::TokenTree::Subtree(tt::Subtree {
806 delimiter: Some(tt::Delimiter {
807 id: tt::TokenId::unspecified(),
808 kind: tt::DelimiterKind::Parenthesis,
810 token_trees: vec![tt::TokenTree::Leaf(tt::Leaf::Ident(tt::Ident {
812 id: tt::TokenId::unspecified(),
816 let t1 = TokenStream::from_str("(a)").unwrap();
817 assert_eq!(t1.token_trees.len(), 1);
818 assert_eq!(t1.token_trees[0], subtree_paren_a);
820 let t2 = TokenStream::from_str("(a);").unwrap();
821 assert_eq!(t2.token_trees.len(), 2);
822 assert_eq!(t2.token_trees[0], subtree_paren_a);
824 let underscore = TokenStream::from_str("_").unwrap();
826 underscore.token_trees[0],
827 tt::TokenTree::Leaf(tt::Leaf::Ident(tt::Ident {
829 id: tt::TokenId::unspecified(),