3 //! `TokenStream`s represent syntactic objects before they are converted into ASTs.
4 //! A `TokenStream` is, roughly speaking, a sequence of [`TokenTree`]s,
5 //! which are themselves a single [`Token`] or a `Delimited` subsequence of tokens.
9 //! `TokenStream`s are persistent data structures constructed as ropes with reference
10 //! counted-children. In general, this means that calling an operation on a `TokenStream`
11 //! (such as `slice`) produces an entirely new `TokenStream` from the borrowed reference to
12 //! the original. This essentially coerces `TokenStream`s into "views" of their subparts,
13 //! and a borrowed `TokenStream` is sufficient to build an owned `TokenStream` without taking
14 //! ownership of the original.
16 use crate::token::{self, Delimiter, Token, TokenKind};
19 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
20 use rustc_data_structures::sync::{self, Lrc};
21 use rustc_macros::HashStable_Generic;
22 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
23 use rustc_span::{Span, DUMMY_SP};
24 use smallvec::{smallvec, SmallVec};
26 use std::{fmt, iter, mem};
28 /// When the main Rust parser encounters a syntax-extension invocation, it
29 /// parses the arguments to the invocation as a token tree. This is a very
30 /// loose structure, such that all sorts of different AST fragments can
31 /// be passed to syntax extensions using a uniform type.
33 /// If the syntax extension is an MBE macro, it will attempt to match its
34 /// LHS token tree against the provided token tree, and if it finds a
35 /// match, will transcribe the RHS token tree, splicing in any captured
36 /// `macro_parser::matched_nonterminals` into the `SubstNt`s it finds.
38 /// The RHS of an MBE macro is the only place `SubstNt`s are substituted.
39 /// Nothing special happens to misnamed or misplaced `SubstNt`s.
40 #[derive(Debug, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
44 /// A delimited sequence of token trees.
45 Delimited(DelimSpan, Delimiter, TokenStream),
48 #[derive(Copy, Clone)]
49 pub enum CanSynthesizeMissingTokens {
54 // Ensure all fields of `TokenTree` is `Send` and `Sync`.
55 #[cfg(parallel_compiler)]
59 DelimSpan: Send + Sync,
60 Delimiter: Send + Sync,
61 TokenStream: Send + Sync,
66 /// Checks if this `TokenTree` is equal to the other, regardless of span information.
67 pub fn eq_unspanned(&self, other: &TokenTree) -> bool {
69 (TokenTree::Token(token), TokenTree::Token(token2)) => token.kind == token2.kind,
70 (TokenTree::Delimited(_, delim, tts), TokenTree::Delimited(_, delim2, tts2)) => {
71 delim == delim2 && tts.eq_unspanned(&tts2)
77 /// Retrieves the `TokenTree`'s span.
78 pub fn span(&self) -> Span {
80 TokenTree::Token(token) => token.span,
81 TokenTree::Delimited(sp, ..) => sp.entire(),
85 /// Modify the `TokenTree`'s span in-place.
86 pub fn set_span(&mut self, span: Span) {
88 TokenTree::Token(token) => token.span = span,
89 TokenTree::Delimited(dspan, ..) => *dspan = DelimSpan::from_single(span),
93 pub fn token(kind: TokenKind, span: Span) -> TokenTree {
94 TokenTree::Token(Token::new(kind, span))
97 pub fn uninterpolate(self) -> TokenTree {
99 TokenTree::Token(token) => TokenTree::Token(token.uninterpolate().into_owned()),
105 impl<CTX> HashStable<CTX> for TokenStream
107 CTX: crate::HashStableContext,
109 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
110 for sub_tt in self.trees() {
111 sub_tt.hash_stable(hcx, hasher);
116 pub trait CreateTokenStream: sync::Send + sync::Sync {
117 fn create_token_stream(&self) -> AttrAnnotatedTokenStream;
120 impl CreateTokenStream for AttrAnnotatedTokenStream {
121 fn create_token_stream(&self) -> AttrAnnotatedTokenStream {
126 /// A lazy version of [`TokenStream`], which defers creation
127 /// of an actual `TokenStream` until it is needed.
128 /// `Box` is here only to reduce the structure size.
130 pub struct LazyTokenStream(Lrc<Box<dyn CreateTokenStream>>);
132 impl LazyTokenStream {
133 pub fn new(inner: impl CreateTokenStream + 'static) -> LazyTokenStream {
134 LazyTokenStream(Lrc::new(Box::new(inner)))
137 pub fn create_token_stream(&self) -> AttrAnnotatedTokenStream {
138 self.0.create_token_stream()
142 impl fmt::Debug for LazyTokenStream {
143 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
144 write!(f, "LazyTokenStream({:?})", self.create_token_stream())
148 impl<S: Encoder> Encodable<S> for LazyTokenStream {
149 fn encode(&self, s: &mut S) -> Result<(), S::Error> {
150 // Used by AST json printing.
151 Encodable::encode(&self.create_token_stream(), s)
155 impl<D: Decoder> Decodable<D> for LazyTokenStream {
156 fn decode(_d: &mut D) -> Self {
157 panic!("Attempted to decode LazyTokenStream");
161 impl<CTX> HashStable<CTX> for LazyTokenStream {
162 fn hash_stable(&self, _hcx: &mut CTX, _hasher: &mut StableHasher) {
163 panic!("Attempted to compute stable hash for LazyTokenStream");
167 /// A `AttrAnnotatedTokenStream` is similar to a `TokenStream`, but with extra
168 /// information about the tokens for attribute targets. This is used
169 /// during expansion to perform early cfg-expansion, and to process attributes
170 /// during proc-macro invocations.
171 #[derive(Clone, Debug, Default, Encodable, Decodable)]
172 pub struct AttrAnnotatedTokenStream(pub Lrc<Vec<(AttrAnnotatedTokenTree, Spacing)>>);
174 /// Like `TokenTree`, but for `AttrAnnotatedTokenStream`
175 #[derive(Clone, Debug, Encodable, Decodable)]
176 pub enum AttrAnnotatedTokenTree {
178 Delimited(DelimSpan, Delimiter, AttrAnnotatedTokenStream),
179 /// Stores the attributes for an attribute target,
180 /// along with the tokens for that attribute target.
181 /// See `AttributesData` for more information
182 Attributes(AttributesData),
185 impl AttrAnnotatedTokenStream {
186 pub fn new(tokens: Vec<(AttrAnnotatedTokenTree, Spacing)>) -> AttrAnnotatedTokenStream {
187 AttrAnnotatedTokenStream(Lrc::new(tokens))
190 /// Converts this `AttrAnnotatedTokenStream` to a plain `TokenStream
191 /// During conversion, `AttrAnnotatedTokenTree::Attributes` get 'flattened'
192 /// back to a `TokenStream` of the form `outer_attr attr_target`.
193 /// If there are inner attributes, they are inserted into the proper
194 /// place in the attribute target tokens.
195 pub fn to_tokenstream(&self) -> TokenStream {
196 let trees: Vec<_> = self
199 .flat_map(|tree| match &tree.0 {
200 AttrAnnotatedTokenTree::Token(inner) => {
201 smallvec![(TokenTree::Token(inner.clone()), tree.1)].into_iter()
203 AttrAnnotatedTokenTree::Delimited(span, delim, stream) => smallvec![(
204 TokenTree::Delimited(*span, *delim, stream.to_tokenstream()),
208 AttrAnnotatedTokenTree::Attributes(data) => {
209 let mut outer_attrs = Vec::new();
210 let mut inner_attrs = Vec::new();
211 for attr in &data.attrs {
213 crate::AttrStyle::Outer => {
214 outer_attrs.push(attr);
216 crate::AttrStyle::Inner => {
217 inner_attrs.push(attr);
222 let mut target_tokens: Vec<_> = data
224 .create_token_stream()
230 if !inner_attrs.is_empty() {
231 let mut found = false;
232 // Check the last two trees (to account for a trailing semi)
233 for (tree, _) in target_tokens.iter_mut().rev().take(2) {
234 if let TokenTree::Delimited(span, delim, delim_tokens) = tree {
235 // Inner attributes are only supported on extern blocks, functions, impls,
236 // and modules. All of these have their inner attributes placed at
237 // the beginning of the rightmost outermost braced group:
238 // e.g. fn foo() { #![my_attr} }
240 // Therefore, we can insert them back into the right location
241 // without needing to do any extra position tracking.
243 // Note: Outline modules are an exception - they can
244 // have attributes like `#![my_attr]` at the start of a file.
245 // Support for custom attributes in this position is not
246 // properly implemented - we always synthesize fake tokens,
247 // so we never reach this code.
249 let mut builder = TokenStreamBuilder::new();
250 for inner_attr in inner_attrs {
251 builder.push(inner_attr.tokens().to_tokenstream());
253 builder.push(delim_tokens.clone());
254 *tree = TokenTree::Delimited(*span, *delim, builder.build());
262 "Failed to find trailing delimited group in: {:?}",
266 let mut flat: SmallVec<[_; 1]> = SmallVec::new();
267 for attr in outer_attrs {
268 // FIXME: Make this more efficient
269 flat.extend(attr.tokens().to_tokenstream().0.clone().iter().cloned());
271 flat.extend(target_tokens);
276 TokenStream::new(trees)
280 /// Stores the tokens for an attribute target, along
281 /// with its attributes.
283 /// This is constructed during parsing when we need to capture
286 /// For example, `#[cfg(FALSE)] struct Foo {}` would
287 /// have an `attrs` field containing the `#[cfg(FALSE)]` attr,
288 /// and a `tokens` field storing the (unparsed) tokens `struct Foo {}`
289 #[derive(Clone, Debug, Encodable, Decodable)]
290 pub struct AttributesData {
291 /// Attributes, both outer and inner.
292 /// These are stored in the original order that they were parsed in.
294 /// The underlying tokens for the attribute target that `attrs`
296 pub tokens: LazyTokenStream,
299 /// A `TokenStream` is an abstract sequence of tokens, organized into [`TokenTree`]s.
301 /// The goal is for procedural macros to work with `TokenStream`s and `TokenTree`s
302 /// instead of a representation of the abstract syntax tree.
303 /// Today's `TokenTree`s can still contain AST via `token::Interpolated` for
304 /// backwards compatibility.
305 #[derive(Clone, Debug, Default, Encodable, Decodable)]
306 pub struct TokenStream(pub(crate) Lrc<Vec<TreeAndSpacing>>);
308 pub type TreeAndSpacing = (TokenTree, Spacing);
310 // `TokenStream` is used a lot. Make sure it doesn't unintentionally get bigger.
311 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
312 rustc_data_structures::static_assert_size!(TokenStream, 8);
314 #[derive(Clone, Copy, Debug, PartialEq, Encodable, Decodable)]
321 /// Given a `TokenStream` with a `Stream` of only two arguments, return a new `TokenStream`
322 /// separating the two arguments with a comma for diagnostic suggestions.
323 pub fn add_comma(&self) -> Option<(TokenStream, Span)> {
324 // Used to suggest if a user writes `foo!(a b);`
325 let mut suggestion = None;
326 let mut iter = self.0.iter().enumerate().peekable();
327 while let Some((pos, ts)) = iter.next() {
328 if let Some((_, next)) = iter.peek() {
329 let sp = match (&ts, &next) {
330 (_, (TokenTree::Token(Token { kind: token::Comma, .. }), _)) => continue,
332 (TokenTree::Token(token_left), Spacing::Alone),
333 (TokenTree::Token(token_right), _),
334 ) if ((token_left.is_ident() && !token_left.is_reserved_ident())
335 || token_left.is_lit())
336 && ((token_right.is_ident() && !token_right.is_reserved_ident())
337 || token_right.is_lit()) =>
341 ((TokenTree::Delimited(sp, ..), Spacing::Alone), _) => sp.entire(),
344 let sp = sp.shrink_to_hi();
345 let comma = (TokenTree::token(token::Comma, sp), Spacing::Alone);
346 suggestion = Some((pos, comma, sp));
349 if let Some((pos, comma, sp)) = suggestion {
350 let mut new_stream = Vec::with_capacity(self.0.len() + 1);
351 let parts = self.0.split_at(pos + 1);
352 new_stream.extend_from_slice(parts.0);
353 new_stream.push(comma);
354 new_stream.extend_from_slice(parts.1);
355 return Some((TokenStream::new(new_stream), sp));
361 impl From<(AttrAnnotatedTokenTree, Spacing)> for AttrAnnotatedTokenStream {
362 fn from((tree, spacing): (AttrAnnotatedTokenTree, Spacing)) -> AttrAnnotatedTokenStream {
363 AttrAnnotatedTokenStream::new(vec![(tree, spacing)])
367 impl From<TokenTree> for TokenStream {
368 fn from(tree: TokenTree) -> TokenStream {
369 TokenStream::new(vec![(tree, Spacing::Alone)])
373 impl From<TokenTree> for TreeAndSpacing {
374 fn from(tree: TokenTree) -> TreeAndSpacing {
375 (tree, Spacing::Alone)
379 impl iter::FromIterator<TokenTree> for TokenStream {
380 fn from_iter<I: IntoIterator<Item = TokenTree>>(iter: I) -> Self {
381 TokenStream::new(iter.into_iter().map(Into::into).collect::<Vec<TreeAndSpacing>>())
385 impl Eq for TokenStream {}
387 impl PartialEq<TokenStream> for TokenStream {
388 fn eq(&self, other: &TokenStream) -> bool {
389 self.trees().eq(other.trees())
394 pub fn new(streams: Vec<TreeAndSpacing>) -> TokenStream {
395 TokenStream(Lrc::new(streams))
398 pub fn is_empty(&self) -> bool {
402 pub fn len(&self) -> usize {
406 pub fn from_streams(mut streams: SmallVec<[TokenStream; 2]>) -> TokenStream {
407 match streams.len() {
408 0 => TokenStream::default(),
409 1 => streams.pop().unwrap(),
411 // We are going to extend the first stream in `streams` with
412 // the elements from the subsequent streams. This requires
413 // using `make_mut()` on the first stream, and in practice this
414 // doesn't cause cloning 99.9% of the time.
416 // One very common use case is when `streams` has two elements,
417 // where the first stream has any number of elements within
418 // (often 1, but sometimes many more) and the second stream has
419 // a single element within.
421 // Determine how much the first stream will be extended.
422 // Needed to avoid quadratic blow up from on-the-fly
423 // reallocations (#57735).
424 let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum();
426 // Get the first stream. If it's `None`, create an empty
428 let mut iter = streams.drain(..);
429 let mut first_stream_lrc = iter.next().unwrap().0;
431 // Append the elements to the first stream, after reserving
433 let first_vec_mut = Lrc::make_mut(&mut first_stream_lrc);
434 first_vec_mut.reserve(num_appends);
436 first_vec_mut.extend(stream.0.iter().cloned());
439 // Create the final `TokenStream`.
440 TokenStream(first_stream_lrc)
445 pub fn trees(&self) -> Cursor {
446 self.clone().into_trees()
449 pub fn into_trees(self) -> Cursor {
453 /// Compares two `TokenStream`s, checking equality without regarding span information.
454 pub fn eq_unspanned(&self, other: &TokenStream) -> bool {
455 let mut t1 = self.trees();
456 let mut t2 = other.trees();
457 for (t1, t2) in iter::zip(&mut t1, &mut t2) {
458 if !t1.eq_unspanned(&t2) {
462 t1.next().is_none() && t2.next().is_none()
465 pub fn map_enumerated<F: FnMut(usize, &TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream {
466 TokenStream(Lrc::new(
470 .map(|(i, (tree, is_joint))| (f(i, tree), *is_joint))
476 // 99.5%+ of the time we have 1 or 2 elements in this vector.
478 pub struct TokenStreamBuilder(SmallVec<[TokenStream; 2]>);
480 impl TokenStreamBuilder {
481 pub fn new() -> TokenStreamBuilder {
482 TokenStreamBuilder(SmallVec::new())
485 pub fn push<T: Into<TokenStream>>(&mut self, stream: T) {
486 let mut stream = stream.into();
488 // If `self` is not empty and the last tree within the last stream is a
489 // token tree marked with `Joint`...
490 if let Some(TokenStream(ref mut last_stream_lrc)) = self.0.last_mut()
491 && let Some((TokenTree::Token(last_token), Spacing::Joint)) = last_stream_lrc.last()
492 // ...and `stream` is not empty and the first tree within it is
494 && let TokenStream(ref mut stream_lrc) = stream
495 && let Some((TokenTree::Token(token), spacing)) = stream_lrc.first()
496 // ...and the two tokens can be glued together...
497 && let Some(glued_tok) = last_token.glue(&token)
499 // ...then do so, by overwriting the last token
500 // tree in `self` and removing the first token tree
501 // from `stream`. This requires using `make_mut()`
502 // on the last stream in `self` and on `stream`,
503 // and in practice this doesn't cause cloning 99.9%
506 // Overwrite the last token tree with the merged
508 let last_vec_mut = Lrc::make_mut(last_stream_lrc);
509 *last_vec_mut.last_mut().unwrap() = (TokenTree::Token(glued_tok), *spacing);
511 // Remove the first token tree from `stream`. (This
512 // is almost always the only tree in `stream`.)
513 let stream_vec_mut = Lrc::make_mut(stream_lrc);
514 stream_vec_mut.remove(0);
516 // Don't push `stream` if it's empty -- that could
517 // block subsequent token gluing, by getting
518 // between two token trees that should be glued
520 if !stream.is_empty() {
528 pub fn build(self) -> TokenStream {
529 TokenStream::from_streams(self.0)
533 /// By-reference iterator over a [`TokenStream`].
535 pub struct CursorRef<'t> {
536 stream: &'t TokenStream,
540 impl<'t> CursorRef<'t> {
541 fn next_with_spacing(&mut self) -> Option<&'t TreeAndSpacing> {
542 self.stream.0.get(self.index).map(|tree| {
549 impl<'t> Iterator for CursorRef<'t> {
550 type Item = &'t TokenTree;
552 fn next(&mut self) -> Option<&'t TokenTree> {
553 self.next_with_spacing().map(|(tree, _)| tree)
557 /// Owning by-value iterator over a [`TokenStream`].
558 // FIXME: Many uses of this can be replaced with by-reference iterator to avoid clones.
561 pub stream: TokenStream,
565 impl Iterator for Cursor {
566 type Item = TokenTree;
568 fn next(&mut self) -> Option<TokenTree> {
569 self.next_with_spacing().map(|(tree, _)| tree)
574 fn new(stream: TokenStream) -> Self {
575 Cursor { stream, index: 0 }
579 pub fn next_with_spacing(&mut self) -> Option<TreeAndSpacing> {
580 self.stream.0.get(self.index).map(|tree| {
587 pub fn next_with_spacing_ref(&mut self) -> Option<&TreeAndSpacing> {
588 self.stream.0.get(self.index).map(|tree| {
594 pub fn index(&self) -> usize {
598 pub fn append(&mut self, new_stream: TokenStream) {
599 if new_stream.is_empty() {
602 let index = self.index;
603 let stream = mem::take(&mut self.stream);
604 *self = TokenStream::from_streams(smallvec![stream, new_stream]).into_trees();
608 pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
609 self.stream.0[self.index..].get(n).map(|(tree, _)| tree)
613 #[derive(Debug, Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
614 pub struct DelimSpan {
620 pub fn from_single(sp: Span) -> Self {
621 DelimSpan { open: sp, close: sp }
624 pub fn from_pair(open: Span, close: Span) -> Self {
625 DelimSpan { open, close }
628 pub fn dummy() -> Self {
629 Self::from_single(DUMMY_SP)
632 pub fn entire(self) -> Span {
633 self.open.with_hi(self.close.hi())