src/libsyntax/tokenstream.rs

   1 // Copyright 2012-2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! # Token Streams
  12 //!
  13 //! `TokenStream`s represent syntactic objects before they are converted into ASTs.
  14 //! A `TokenStream` is, roughly speaking, a sequence (eg stream) of `TokenTree`s,
  15 //! which are themselves a single `Token` or a `Delimited` subsequence of tokens.
  16 //!
  17 //! ## Ownership
  18 //! `TokenStreams` are persistent data structures constructed as ropes with reference
  19 //! counted-children. In general, this means that calling an operation on a `TokenStream`
  20 //! (such as `slice`) produces an entirely new `TokenStream` from the borrowed reference to
  21 //! the original. This essentially coerces `TokenStream`s into 'views' of their subparts,
  22 //! and a borrowed `TokenStream` is sufficient to build an owned `TokenStream` without taking
  23 //! ownership of the original.
  24
  25 use syntax_pos::{BytePos, Span, DUMMY_SP};
  26 use ext::base;
  27 use ext::tt::{macro_parser, quoted};
  28 use parse::Directory;
  29 use parse::token::{self, Token};
  30 use print::pprust;
  31 use serialize::{Decoder, Decodable, Encoder, Encodable};
  32 use util::RcSlice;
  33
  34 use std::{fmt, iter, mem};
  35 use std::hash::{self, Hash};
  36
  37 /// A delimited sequence of token trees
  38 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
  39 pub struct Delimited {
  40     /// The type of delimiter
  41     pub delim: token::DelimToken,
  42     /// The delimited sequence of token trees
  43     pub tts: ThinTokenStream,
  44 }
  45
  46 impl Delimited {
  47     /// Returns the opening delimiter as a token.
  48     pub fn open_token(&self) -> token::Token {
  49         token::OpenDelim(self.delim)
  50     }
  51
  52     /// Returns the closing delimiter as a token.
  53     pub fn close_token(&self) -> token::Token {
  54         token::CloseDelim(self.delim)
  55     }
  56
  57     /// Returns the opening delimiter as a token tree.
  58     pub fn open_tt(&self, span: Span) -> TokenTree {
  59         let open_span = if span == DUMMY_SP {
  60             DUMMY_SP
  61         } else {
  62             span.with_hi(span.lo() + BytePos(self.delim.len() as u32))
  63         };
  64         TokenTree::Token(open_span, self.open_token())
  65     }
  66
  67     /// Returns the closing delimiter as a token tree.
  68     pub fn close_tt(&self, span: Span) -> TokenTree {
  69         let close_span = if span == DUMMY_SP {
  70             DUMMY_SP
  71         } else {
  72             span.with_lo(span.hi() - BytePos(self.delim.len() as u32))
  73         };
  74         TokenTree::Token(close_span, self.close_token())
  75     }
  76
  77     /// Returns the token trees inside the delimiters.
  78     pub fn stream(&self) -> TokenStream {
  79         self.tts.clone().into()
  80     }
  81 }
  82
  83 /// When the main rust parser encounters a syntax-extension invocation, it
  84 /// parses the arguments to the invocation as a token-tree. This is a very
  85 /// loose structure, such that all sorts of different AST-fragments can
  86 /// be passed to syntax extensions using a uniform type.
  87 ///
  88 /// If the syntax extension is an MBE macro, it will attempt to match its
  89 /// LHS token tree against the provided token tree, and if it finds a
  90 /// match, will transcribe the RHS token tree, splicing in any captured
  91 /// `macro_parser::matched_nonterminals` into the `SubstNt`s it finds.
  92 ///
  93 /// The RHS of an MBE macro is the only place `SubstNt`s are substituted.
  94 /// Nothing special happens to misnamed or misplaced `SubstNt`s.
  95 #[derive(Debug, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash)]
  96 pub enum TokenTree {
  97     /// A single token
  98     Token(Span, token::Token),
  99     /// A delimited sequence of token trees
 100     Delimited(Span, Delimited),
 101 }
 102
 103 impl TokenTree {
 104     /// Use this token tree as a matcher to parse given tts.
 105     pub fn parse(cx: &base::ExtCtxt, mtch: &[quoted::TokenTree], tts: TokenStream)
 106                  -> macro_parser::NamedParseResult {
 107         // `None` is because we're not interpolating
 108         let directory = Directory {
 109             path: cx.current_expansion.module.directory.clone(),
 110             ownership: cx.current_expansion.directory_ownership,
 111         };
 112         macro_parser::parse(cx.parse_sess(), tts, mtch, Some(directory), true)
 113     }
 114
 115     /// Check if this TokenTree is equal to the other, regardless of span information.
 116     pub fn eq_unspanned(&self, other: &TokenTree) -> bool {
 117         match (self, other) {
 118             (&TokenTree::Token(_, ref tk), &TokenTree::Token(_, ref tk2)) => tk == tk2,
 119             (&TokenTree::Delimited(_, ref dl), &TokenTree::Delimited(_, ref dl2)) => {
 120                 dl.delim == dl2.delim &&
 121                 dl.stream().trees().zip(dl2.stream().trees()).all(|(tt, tt2)| tt.eq_unspanned(&tt2))
 122             }
 123             (_, _) => false,
 124         }
 125     }
 126
 127     /// Retrieve the TokenTree's span.
 128     pub fn span(&self) -> Span {
 129         match *self {
 130             TokenTree::Token(sp, _) | TokenTree::Delimited(sp, _) => sp,
 131         }
 132     }
 133
 134     /// Modify the `TokenTree`'s span inplace.
 135     pub fn set_span(&mut self, span: Span) {
 136         match *self {
 137             TokenTree::Token(ref mut sp, _) | TokenTree::Delimited(ref mut sp, _) => {
 138                 *sp = span;
 139             }
 140         }
 141     }
 142
 143     /// Indicates if the stream is a token that is equal to the provided token.
 144     pub fn eq_token(&self, t: Token) -> bool {
 145         match *self {
 146             TokenTree::Token(_, ref tk) => *tk == t,
 147             _ => false,
 148         }
 149     }
 150
 151     pub fn joint(self) -> TokenStream {
 152         TokenStream { kind: TokenStreamKind::JointTree(self) }
 153     }
 154 }
 155
 156 /// # Token Streams
 157 ///
 158 /// A `TokenStream` is an abstract sequence of tokens, organized into `TokenTree`s.
 159 /// The goal is for procedural macros to work with `TokenStream`s and `TokenTree`s
 160 /// instead of a representation of the abstract syntax tree.
 161 /// Today's `TokenTree`s can still contain AST via `Token::Interpolated` for back-compat.
 162 #[derive(Clone, Debug)]
 163 pub struct TokenStream {
 164     kind: TokenStreamKind,
 165 }
 166
 167 #[derive(Clone, Debug)]
 168 enum TokenStreamKind {
 169     Empty,
 170     Tree(TokenTree),
 171     JointTree(TokenTree),
 172     Stream(RcSlice<TokenStream>),
 173 }
 174
 175 impl From<TokenTree> for TokenStream {
 176     fn from(tt: TokenTree) -> TokenStream {
 177         TokenStream { kind: TokenStreamKind::Tree(tt) }
 178     }
 179 }
 180
 181 impl From<Token> for TokenStream {
 182     fn from(token: Token) -> TokenStream {
 183         TokenTree::Token(DUMMY_SP, token).into()
 184     }
 185 }
 186
 187 impl<T: Into<TokenStream>> iter::FromIterator<T> for TokenStream {
 188     fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
 189         TokenStream::concat(iter.into_iter().map(Into::into).collect::<Vec<_>>())
 190     }
 191 }
 192
 193 impl Eq for TokenStream {}
 194
 195 impl PartialEq<TokenStream> for TokenStream {
 196     fn eq(&self, other: &TokenStream) -> bool {
 197         self.trees().eq(other.trees())
 198     }
 199 }
 200
 201 impl TokenStream {
 202     pub fn len(&self) -> usize {
 203         if let TokenStreamKind::Stream(ref slice) = self.kind {
 204             slice.len()
 205         } else {
 206             0
 207         }
 208     }
 209
 210     pub fn empty() -> TokenStream {
 211         TokenStream { kind: TokenStreamKind::Empty }
 212     }
 213
 214     pub fn is_empty(&self) -> bool {
 215         match self.kind {
 216             TokenStreamKind::Empty => true,
 217             _ => false,
 218         }
 219     }
 220
 221     pub fn concat(mut streams: Vec<TokenStream>) -> TokenStream {
 222         match streams.len() {
 223             0 => TokenStream::empty(),
 224             1 => streams.pop().unwrap(),
 225             _ => TokenStream::concat_rc_slice(RcSlice::new(streams)),
 226         }
 227     }
 228
 229     fn concat_rc_slice(streams: RcSlice<TokenStream>) -> TokenStream {
 230         TokenStream { kind: TokenStreamKind::Stream(streams) }
 231     }
 232
 233     pub fn trees(&self) -> Cursor {
 234         self.clone().into_trees()
 235     }
 236
 237     pub fn into_trees(self) -> Cursor {
 238         Cursor::new(self)
 239     }
 240
 241     /// Compares two TokenStreams, checking equality without regarding span information.
 242     pub fn eq_unspanned(&self, other: &TokenStream) -> bool {
 243         for (t1, t2) in self.trees().zip(other.trees()) {
 244             if !t1.eq_unspanned(&t2) {
 245                 return false;
 246             }
 247         }
 248         true
 249     }
 250
 251     /// Precondition: `self` consists of a single token tree.
 252     /// Returns true if the token tree is a joint operation w.r.t. `proc_macro::TokenNode`.
 253     pub fn as_tree(self) -> (TokenTree, bool /* joint? */) {
 254         match self.kind {
 255             TokenStreamKind::Tree(tree) => (tree, false),
 256             TokenStreamKind::JointTree(tree) => (tree, true),
 257             _ => unreachable!(),
 258         }
 259     }
 260
 261     pub fn map_enumerated<F: FnMut(usize, TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream {
 262         let mut trees = self.into_trees();
 263         let mut result = Vec::new();
 264         let mut i = 0;
 265         while let Some(stream) = trees.next_as_stream() {
 266             result.push(match stream.kind {
 267                 TokenStreamKind::Tree(tree) => f(i, tree).into(),
 268                 TokenStreamKind::JointTree(tree) => f(i, tree).joint(),
 269                 _ => unreachable!()
 270             });
 271             i += 1;
 272         }
 273         TokenStream::concat(result)
 274     }
 275
 276     pub fn map<F: FnMut(TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream {
 277         let mut trees = self.into_trees();
 278         let mut result = Vec::new();
 279         while let Some(stream) = trees.next_as_stream() {
 280             result.push(match stream.kind {
 281                 TokenStreamKind::Tree(tree) => f(tree).into(),
 282                 TokenStreamKind::JointTree(tree) => f(tree).joint(),
 283                 _ => unreachable!()
 284             });
 285         }
 286         TokenStream::concat(result)
 287     }
 288
 289     fn first_tree_and_joint(&self) -> Option<(TokenTree, bool)> {
 290         match self.kind {
 291             TokenStreamKind::Empty => None,
 292             TokenStreamKind::Tree(ref tree) => Some((tree.clone(), false)),
 293             TokenStreamKind::JointTree(ref tree) => Some((tree.clone(), true)),
 294             TokenStreamKind::Stream(ref stream) => stream.first().unwrap().first_tree_and_joint(),
 295         }
 296     }
 297
 298     fn last_tree_if_joint(&self) -> Option<TokenTree> {
 299         match self.kind {
 300             TokenStreamKind::Empty | TokenStreamKind::Tree(..) => None,
 301             TokenStreamKind::JointTree(ref tree) => Some(tree.clone()),
 302             TokenStreamKind::Stream(ref stream) => stream.last().unwrap().last_tree_if_joint(),
 303         }
 304     }
 305 }
 306
 307 pub struct TokenStreamBuilder(Vec<TokenStream>);
 308
 309 impl TokenStreamBuilder {
 310     pub fn new() -> TokenStreamBuilder {
 311         TokenStreamBuilder(Vec::new())
 312     }
 313
 314     pub fn push<T: Into<TokenStream>>(&mut self, stream: T) {
 315         let stream = stream.into();
 316         let last_tree_if_joint = self.0.last().and_then(TokenStream::last_tree_if_joint);
 317         if let Some(TokenTree::Token(last_span, last_tok)) = last_tree_if_joint {
 318             if let Some((TokenTree::Token(span, tok), is_joint)) = stream.first_tree_and_joint() {
 319                 if let Some(glued_tok) = last_tok.glue(tok) {
 320                     let last_stream = self.0.pop().unwrap();
 321                     self.push_all_but_last_tree(&last_stream);
 322                     let glued_span = last_span.to(span);
 323                     let glued_tt = TokenTree::Token(glued_span, glued_tok);
 324                     let glued_tokenstream = if is_joint {
 325                         glued_tt.joint()
 326                     } else {
 327                         glued_tt.into()
 328                     };
 329                     self.0.push(glued_tokenstream);
 330                     self.push_all_but_first_tree(&stream);
 331                     return
 332                 }
 333             }
 334         }
 335         self.0.push(stream);
 336     }
 337
 338     pub fn add<T: Into<TokenStream>>(mut self, stream: T) -> Self {
 339         self.push(stream);
 340         self
 341     }
 342
 343     pub fn build(self) -> TokenStream {
 344         TokenStream::concat(self.0)
 345     }
 346
 347     fn push_all_but_last_tree(&mut self, stream: &TokenStream) {
 348         if let TokenStreamKind::Stream(ref streams) = stream.kind {
 349             let len = streams.len();
 350             match len {
 351                 1 => {}
 352                 2 => self.0.push(streams[0].clone().into()),
 353                 _ => self.0.push(TokenStream::concat_rc_slice(streams.sub_slice(0 .. len - 1))),
 354             }
 355             self.push_all_but_last_tree(&streams[len - 1])
 356         }
 357     }
 358
 359     fn push_all_but_first_tree(&mut self, stream: &TokenStream) {
 360         if let TokenStreamKind::Stream(ref streams) = stream.kind {
 361             let len = streams.len();
 362             match len {
 363                 1 => {}
 364                 2 => self.0.push(streams[1].clone().into()),
 365                 _ => self.0.push(TokenStream::concat_rc_slice(streams.sub_slice(1 .. len))),
 366             }
 367             self.push_all_but_first_tree(&streams[0])
 368         }
 369     }
 370 }
 371
 372 #[derive(Clone)]
 373 pub struct Cursor(CursorKind);
 374
 375 #[derive(Clone)]
 376 enum CursorKind {
 377     Empty,
 378     Tree(TokenTree, bool /* consumed? */),
 379     JointTree(TokenTree, bool /* consumed? */),
 380     Stream(StreamCursor),
 381 }
 382
 383 #[derive(Clone)]
 384 struct StreamCursor {
 385     stream: RcSlice<TokenStream>,
 386     index: usize,
 387     stack: Vec<(RcSlice<TokenStream>, usize)>,
 388 }
 389
 390 impl StreamCursor {
 391     fn new(stream: RcSlice<TokenStream>) -> Self {
 392         StreamCursor { stream: stream, index: 0, stack: Vec::new() }
 393     }
 394
 395     fn next_as_stream(&mut self) -> Option<TokenStream> {
 396         loop {
 397             if self.index < self.stream.len() {
 398                 self.index += 1;
 399                 let next = self.stream[self.index - 1].clone();
 400                 match next.kind {
 401                     TokenStreamKind::Tree(..) | TokenStreamKind::JointTree(..) => return Some(next),
 402                     TokenStreamKind::Stream(stream) => self.insert(stream),
 403                     TokenStreamKind::Empty => {}
 404                 }
 405             } else if let Some((stream, index)) = self.stack.pop() {
 406                 self.stream = stream;
 407                 self.index = index;
 408             } else {
 409                 return None;
 410             }
 411         }
 412     }
 413
 414     fn insert(&mut self, stream: RcSlice<TokenStream>) {
 415         self.stack.push((mem::replace(&mut self.stream, stream),
 416                          mem::replace(&mut self.index, 0)));
 417     }
 418 }
 419
 420 impl Iterator for Cursor {
 421     type Item = TokenTree;
 422
 423     fn next(&mut self) -> Option<TokenTree> {
 424         self.next_as_stream().map(|stream| match stream.kind {
 425             TokenStreamKind::Tree(tree) | TokenStreamKind::JointTree(tree) => tree,
 426             _ => unreachable!()
 427         })
 428     }
 429 }
 430
 431 impl Cursor {
 432     fn new(stream: TokenStream) -> Self {
 433         Cursor(match stream.kind {
 434             TokenStreamKind::Empty => CursorKind::Empty,
 435             TokenStreamKind::Tree(tree) => CursorKind::Tree(tree, false),
 436             TokenStreamKind::JointTree(tree) => CursorKind::JointTree(tree, false),
 437             TokenStreamKind::Stream(stream) => CursorKind::Stream(StreamCursor::new(stream)),
 438         })
 439     }
 440
 441     pub fn next_as_stream(&mut self) -> Option<TokenStream> {
 442         let (stream, consumed) = match self.0 {
 443             CursorKind::Tree(ref tree, ref mut consumed @ false) =>
 444                 (tree.clone().into(), consumed),
 445             CursorKind::JointTree(ref tree, ref mut consumed @ false) =>
 446                 (tree.clone().joint(), consumed),
 447             CursorKind::Stream(ref mut cursor) => return cursor.next_as_stream(),
 448             _ => return None,
 449         };
 450
 451         *consumed = true;
 452         Some(stream)
 453     }
 454
 455     pub fn insert(&mut self, stream: TokenStream) {
 456         match self.0 {
 457             _ if stream.is_empty() => return,
 458             CursorKind::Empty => *self = stream.trees(),
 459             CursorKind::Tree(_, consumed) | CursorKind::JointTree(_, consumed) => {
 460                 *self = TokenStream::concat(vec![self.original_stream(), stream]).trees();
 461                 if consumed {
 462                     self.next();
 463                 }
 464             }
 465             CursorKind::Stream(ref mut cursor) => {
 466                 cursor.insert(ThinTokenStream::from(stream).0.unwrap());
 467             }
 468         }
 469     }
 470
 471     pub fn original_stream(&self) -> TokenStream {
 472         match self.0 {
 473             CursorKind::Empty => TokenStream::empty(),
 474             CursorKind::Tree(ref tree, _) => tree.clone().into(),
 475             CursorKind::JointTree(ref tree, _) => tree.clone().joint(),
 476             CursorKind::Stream(ref cursor) => TokenStream::concat_rc_slice({
 477                 cursor.stack.get(0).cloned().map(|(stream, _)| stream)
 478                     .unwrap_or(cursor.stream.clone())
 479             }),
 480         }
 481     }
 482
 483     pub fn look_ahead(&self, n: usize) -> Option<TokenTree> {
 484         fn look_ahead(streams: &[TokenStream], mut n: usize) -> Result<TokenTree, usize> {
 485             for stream in streams {
 486                 n = match stream.kind {
 487                     TokenStreamKind::Tree(ref tree) | TokenStreamKind::JointTree(ref tree)
 488                         if n == 0 => return Ok(tree.clone()),
 489                     TokenStreamKind::Tree(..) | TokenStreamKind::JointTree(..) => n - 1,
 490                     TokenStreamKind::Stream(ref stream) => match look_ahead(stream, n) {
 491                         Ok(tree) => return Ok(tree),
 492                         Err(n) => n,
 493                     },
 494                     _ => n,
 495                 };
 496             }
 497             Err(n)
 498         }
 499
 500         match self.0 {
 501             CursorKind::Empty |
 502             CursorKind::Tree(_, true) |
 503             CursorKind::JointTree(_, true) => Err(n),
 504             CursorKind::Tree(ref tree, false) |
 505             CursorKind::JointTree(ref tree, false) => look_ahead(&[tree.clone().into()], n),
 506             CursorKind::Stream(ref cursor) => {
 507                 look_ahead(&cursor.stream[cursor.index ..], n).or_else(|mut n| {
 508                     for &(ref stream, index) in cursor.stack.iter().rev() {
 509                         n = match look_ahead(&stream[index..], n) {
 510                             Ok(tree) => return Ok(tree),
 511                             Err(n) => n,
 512                         }
 513                     }
 514
 515                     Err(n)
 516                 })
 517             }
 518         }.ok()
 519     }
 520 }
 521
 522 /// The `TokenStream` type is large enough to represent a single `TokenTree` without allocation.
 523 /// `ThinTokenStream` is smaller, but needs to allocate to represent a single `TokenTree`.
 524 /// We must use `ThinTokenStream` in `TokenTree::Delimited` to avoid infinite size due to recursion.
 525 #[derive(Debug, Clone)]
 526 pub struct ThinTokenStream(Option<RcSlice<TokenStream>>);
 527
 528 impl From<TokenStream> for ThinTokenStream {
 529     fn from(stream: TokenStream) -> ThinTokenStream {
 530         ThinTokenStream(match stream.kind {
 531             TokenStreamKind::Empty => None,
 532             TokenStreamKind::Tree(tree) => Some(RcSlice::new(vec![tree.into()])),
 533             TokenStreamKind::JointTree(tree) => Some(RcSlice::new(vec![tree.joint()])),
 534             TokenStreamKind::Stream(stream) => Some(stream),
 535         })
 536     }
 537 }
 538
 539 impl From<ThinTokenStream> for TokenStream {
 540     fn from(stream: ThinTokenStream) -> TokenStream {
 541         stream.0.map(TokenStream::concat_rc_slice).unwrap_or_else(TokenStream::empty)
 542     }
 543 }
 544
 545 impl Eq for ThinTokenStream {}
 546
 547 impl PartialEq<ThinTokenStream> for ThinTokenStream {
 548     fn eq(&self, other: &ThinTokenStream) -> bool {
 549         TokenStream::from(self.clone()) == TokenStream::from(other.clone())
 550     }
 551 }
 552
 553 impl fmt::Display for TokenStream {
 554     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 555         f.write_str(&pprust::tokens_to_string(self.clone()))
 556     }
 557 }
 558
 559 impl Encodable for TokenStream {
 560     fn encode<E: Encoder>(&self, encoder: &mut E) -> Result<(), E::Error> {
 561         self.trees().collect::<Vec<_>>().encode(encoder)
 562     }
 563 }
 564
 565 impl Decodable for TokenStream {
 566     fn decode<D: Decoder>(decoder: &mut D) -> Result<TokenStream, D::Error> {
 567         Vec::<TokenTree>::decode(decoder).map(|vec| vec.into_iter().collect())
 568     }
 569 }
 570
 571 impl Hash for TokenStream {
 572     fn hash<H: hash::Hasher>(&self, state: &mut H) {
 573         for tree in self.trees() {
 574             tree.hash(state);
 575         }
 576     }
 577 }
 578
 579 impl Encodable for ThinTokenStream {
 580     fn encode<E: Encoder>(&self, encoder: &mut E) -> Result<(), E::Error> {
 581         TokenStream::from(self.clone()).encode(encoder)
 582     }
 583 }
 584
 585 impl Decodable for ThinTokenStream {
 586     fn decode<D: Decoder>(decoder: &mut D) -> Result<ThinTokenStream, D::Error> {
 587         TokenStream::decode(decoder).map(Into::into)
 588     }
 589 }
 590
 591 impl Hash for ThinTokenStream {
 592     fn hash<H: hash::Hasher>(&self, state: &mut H) {
 593         TokenStream::from(self.clone()).hash(state);
 594     }
 595 }
 596
 597
 598 #[cfg(test)]
 599 mod tests {
 600     use super::*;
 601     use syntax::ast::Ident;
 602     use syntax_pos::{Span, BytePos, NO_EXPANSION};
 603     use parse::token::Token;
 604     use util::parser_testing::string_to_stream;
 605
 606     fn string_to_ts(string: &str) -> TokenStream {
 607         string_to_stream(string.to_owned())
 608     }
 609
 610     fn sp(a: u32, b: u32) -> Span {
 611         Span::new(BytePos(a), BytePos(b), NO_EXPANSION)
 612     }
 613
 614     #[test]
 615     fn test_concat() {
 616         let test_res = string_to_ts("foo::bar::baz");
 617         let test_fst = string_to_ts("foo::bar");
 618         let test_snd = string_to_ts("::baz");
 619         let eq_res = TokenStream::concat(vec![test_fst, test_snd]);
 620         assert_eq!(test_res.trees().count(), 5);
 621         assert_eq!(eq_res.trees().count(), 5);
 622         assert_eq!(test_res.eq_unspanned(&eq_res), true);
 623     }
 624
 625     #[test]
 626     fn test_to_from_bijection() {
 627         let test_start = string_to_ts("foo::bar(baz)");
 628         let test_end = test_start.trees().collect();
 629         assert_eq!(test_start, test_end)
 630     }
 631
 632     #[test]
 633     fn test_eq_0() {
 634         let test_res = string_to_ts("foo");
 635         let test_eqs = string_to_ts("foo");
 636         assert_eq!(test_res, test_eqs)
 637     }
 638
 639     #[test]
 640     fn test_eq_1() {
 641         let test_res = string_to_ts("::bar::baz");
 642         let test_eqs = string_to_ts("::bar::baz");
 643         assert_eq!(test_res, test_eqs)
 644     }
 645
 646     #[test]
 647     fn test_eq_3() {
 648         let test_res = string_to_ts("");
 649         let test_eqs = string_to_ts("");
 650         assert_eq!(test_res, test_eqs)
 651     }
 652
 653     #[test]
 654     fn test_diseq_0() {
 655         let test_res = string_to_ts("::bar::baz");
 656         let test_eqs = string_to_ts("bar::baz");
 657         assert_eq!(test_res == test_eqs, false)
 658     }
 659
 660     #[test]
 661     fn test_diseq_1() {
 662         let test_res = string_to_ts("(bar,baz)");
 663         let test_eqs = string_to_ts("bar,baz");
 664         assert_eq!(test_res == test_eqs, false)
 665     }
 666
 667     #[test]
 668     fn test_is_empty() {
 669         let test0: TokenStream = Vec::<TokenTree>::new().into_iter().collect();
 670         let test1: TokenStream =
 671             TokenTree::Token(sp(0, 1), Token::Ident(Ident::from_str("a"))).into();
 672         let test2 = string_to_ts("foo(bar::baz)");
 673
 674         assert_eq!(test0.is_empty(), true);
 675         assert_eq!(test1.is_empty(), false);
 676         assert_eq!(test2.is_empty(), false);
 677     }
 678
 679     #[test]
 680     fn test_dotdotdot() {
 681         let mut builder = TokenStreamBuilder::new();
 682         builder.push(TokenTree::Token(sp(0, 1), Token::Dot).joint());
 683         builder.push(TokenTree::Token(sp(1, 2), Token::Dot).joint());
 684         builder.push(TokenTree::Token(sp(2, 3), Token::Dot));
 685         let stream = builder.build();
 686         assert!(stream.eq_unspanned(&string_to_ts("...")));
 687         assert_eq!(stream.trees().count(), 1);
 688     }
 689
 690 }