| //! # Token Streams |
| //! |
| //! `TokenStream`s represent syntactic objects before they are converted into ASTs. |
| //! A `TokenStream` is, roughly speaking, a sequence (eg stream) 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::token::{self, DelimToken, Token, TokenKind}; |
| |
| use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; |
| use rustc_data_structures::sync::Lrc; |
| use rustc_macros::HashStable_Generic; |
| use rustc_span::{Span, DUMMY_SP}; |
| use smallvec::{smallvec, SmallVec}; |
| |
| use std::{iter, mem}; |
| |
| /// 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, RustcEncodable, RustcDecodable, HashStable_Generic)] |
| pub enum TokenTree { |
| /// A single token |
| Token(Token), |
| /// A delimited sequence of token trees |
| Delimited(DelimSpan, DelimToken, TokenStream), |
| } |
| |
| // Ensure all fields of `TokenTree` is `Send` and `Sync`. |
| #[cfg(parallel_compiler)] |
| fn _dummy() |
| where |
| Token: Send + Sync, |
| DelimSpan: Send + Sync, |
| DelimToken: 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, |
| } |
| } |
| |
| // See comments in `Nonterminal::to_tokenstream` for why we care about |
| // *probably* equal here rather than actual equality |
| // |
| // This is otherwise the same as `eq_unspanned`, only recursing with a |
| // different method. |
| pub fn probably_equal_for_proc_macro(&self, other: &TokenTree) -> bool { |
| match (self, other) { |
| (TokenTree::Token(token), TokenTree::Token(token2)) => { |
| token.probably_equal_for_proc_macro(token2) |
| } |
| (TokenTree::Delimited(_, delim, tts), TokenTree::Delimited(_, delim2, tts2)) => { |
| delim == delim2 && tts.probably_equal_for_proc_macro(&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), |
| } |
| } |
| |
| pub fn joint(self) -> TokenStream { |
| TokenStream::new(vec![(self, Joint)]) |
| } |
| |
| pub fn token(kind: TokenKind, span: Span) -> TokenTree { |
| TokenTree::Token(Token::new(kind, span)) |
| } |
| |
| /// Returns the opening delimiter as a token tree. |
| pub fn open_tt(span: DelimSpan, delim: DelimToken) -> TokenTree { |
| TokenTree::token(token::OpenDelim(delim), span.open) |
| } |
| |
| /// Returns the closing delimiter as a token tree. |
| pub fn close_tt(span: DelimSpan, delim: DelimToken) -> TokenTree { |
| TokenTree::token(token::CloseDelim(delim), span.close) |
| } |
| |
| pub fn uninterpolate(self) -> TokenTree { |
| match self { |
| TokenTree::Token(token) => TokenTree::Token(token.uninterpolate().into_owned()), |
| 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); |
| } |
| } |
| } |
| |
| /// 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 back-compat. |
| #[derive(Clone, Debug, Default, RustcEncodable, RustcDecodable)] |
| pub struct TokenStream(pub Lrc<Vec<TreeAndJoint>>); |
| |
| pub type TreeAndJoint = (TokenTree, IsJoint); |
| |
| // `TokenStream` is used a lot. Make sure it doesn't unintentionally get bigger. |
| #[cfg(target_arch = "x86_64")] |
| rustc_data_structures::static_assert_size!(TokenStream, 8); |
| |
| #[derive(Clone, Copy, Debug, PartialEq, RustcEncodable, RustcDecodable)] |
| pub enum IsJoint { |
| Joint, |
| NonJoint, |
| } |
| |
| use IsJoint::*; |
| |
| 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), NonJoint), |
| (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, ..), NonJoint), _) => sp.entire(), |
| _ => continue, |
| }; |
| let sp = sp.shrink_to_hi(); |
| let comma = (TokenTree::token(token::Comma, sp), NonJoint); |
| suggestion = Some((pos, comma, sp)); |
| } |
| } |
| if let Some((pos, comma, sp)) = suggestion { |
| let mut new_stream = vec![]; |
| 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 From<TokenTree> for TokenStream { |
| fn from(tree: TokenTree) -> TokenStream { |
| TokenStream::new(vec![(tree, NonJoint)]) |
| } |
| } |
| |
| impl From<TokenTree> for TreeAndJoint { |
| fn from(tree: TokenTree) -> TreeAndJoint { |
| (tree, NonJoint) |
| } |
| } |
| |
| impl iter::FromIterator<TokenTree> for TokenStream { |
| fn from_iter<I: IntoIterator<Item = TokenTree>>(iter: I) -> Self { |
| TokenStream::new(iter.into_iter().map(Into::into).collect::<Vec<TreeAndJoint>>()) |
| } |
| } |
| |
| 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<TreeAndJoint>) -> 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 span(&self) -> Option<Span> { |
| match &**self.0 { |
| [] => None, |
| [(tt, _)] => Some(tt.span()), |
| [(tt_start, _), .., (tt_end, _)] => Some(tt_start.span().to(tt_end.span())), |
| } |
| } |
| |
| pub fn from_streams(mut streams: SmallVec<[TokenStream; 2]>) -> TokenStream { |
| match streams.len() { |
| 0 => TokenStream::default(), |
| 1 => streams.pop().unwrap(), |
| _ => { |
| // We are going to extend the first stream in `streams` with |
| // the elements from the subsequent streams. This requires |
| // using `make_mut()` on the first stream, and in practice this |
| // doesn't cause cloning 99.9% of the time. |
| // |
| // One very common use case is when `streams` has two elements, |
| // where the first stream has any number of elements within |
| // (often 1, but sometimes many more) and the second stream has |
| // a single element within. |
| |
| // Determine how much the first stream will be extended. |
| // Needed to avoid quadratic blow up from on-the-fly |
| // reallocations (#57735). |
| let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum(); |
| |
| // Get the first stream. If it's `None`, create an empty |
| // stream. |
| let mut iter = streams.drain(..); |
| let mut first_stream_lrc = iter.next().unwrap().0; |
| |
| // Append the elements to the first stream, after reserving |
| // space for them. |
| let first_vec_mut = Lrc::make_mut(&mut first_stream_lrc); |
| first_vec_mut.reserve(num_appends); |
| for stream in iter { |
| first_vec_mut.extend(stream.0.iter().cloned()); |
| } |
| |
| // Create the final `TokenStream`. |
| TokenStream(first_stream_lrc) |
| } |
| } |
| } |
| |
| pub fn trees(&self) -> Cursor { |
| self.clone().into_trees() |
| } |
| |
| pub fn into_trees(self) -> Cursor { |
| Cursor::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 t1.by_ref().zip(t2.by_ref()) { |
| if !t1.eq_unspanned(&t2) { |
| return false; |
| } |
| } |
| t1.next().is_none() && t2.next().is_none() |
| } |
| |
| // See comments in `Nonterminal::to_tokenstream` for why we care about |
| // *probably* equal here rather than actual equality |
| // |
| // This is otherwise the same as `eq_unspanned`, only recursing with a |
| // different method. |
| pub fn probably_equal_for_proc_macro(&self, other: &TokenStream) -> bool { |
| // When checking for `probably_eq`, we ignore certain tokens that aren't |
| // preserved in the AST. Because they are not preserved, the pretty |
| // printer arbitrarily adds or removes them when printing as token |
| // streams, making a comparison between a token stream generated from an |
| // AST and a token stream which was parsed into an AST more reliable. |
| fn semantic_tree(tree: &TokenTree) -> bool { |
| if let TokenTree::Token(token) = tree { |
| if let |
| // The pretty printer tends to add trailing commas to |
| // everything, and in particular, after struct fields. |
| | token::Comma |
| // The pretty printer emits `NoDelim` as whitespace. |
| | token::OpenDelim(DelimToken::NoDelim) |
| | token::CloseDelim(DelimToken::NoDelim) |
| // The pretty printer collapses many semicolons into one. |
| | token::Semi |
| // The pretty printer collapses whitespace arbitrarily and can |
| // introduce whitespace from `NoDelim`. |
| | token::Whitespace |
| // The pretty printer can turn `$crate` into `::crate_name` |
| | token::ModSep = token.kind { |
| return false; |
| } |
| } |
| true |
| } |
| |
| let mut t1 = self.trees().filter(semantic_tree); |
| let mut t2 = other.trees().filter(semantic_tree); |
| for (t1, t2) in t1.by_ref().zip(t2.by_ref()) { |
| if !t1.probably_equal_for_proc_macro(&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, is_joint))| (f(i, tree.clone()), *is_joint)) |
| .collect(), |
| )) |
| } |
| |
| pub fn map<F: FnMut(TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream { |
| TokenStream(Lrc::new( |
| self.0.iter().map(|(tree, is_joint)| (f(tree.clone()), *is_joint)).collect(), |
| )) |
| } |
| } |
| |
| // 99.5%+ of the time we have 1 or 2 elements in this vector. |
| #[derive(Clone)] |
| pub struct TokenStreamBuilder(SmallVec<[TokenStream; 2]>); |
| |
| impl TokenStreamBuilder { |
| pub fn new() -> TokenStreamBuilder { |
| TokenStreamBuilder(SmallVec::new()) |
| } |
| |
| pub fn push<T: Into<TokenStream>>(&mut self, stream: T) { |
| let mut stream = stream.into(); |
| |
| // If `self` is not empty and the last tree within the last stream is a |
| // token tree marked with `Joint`... |
| if let Some(TokenStream(ref mut last_stream_lrc)) = self.0.last_mut() { |
| if let Some((TokenTree::Token(last_token), Joint)) = last_stream_lrc.last() { |
| // ...and `stream` is not empty and the first tree within it is |
| // a token tree... |
| let TokenStream(ref mut stream_lrc) = stream; |
| if let Some((TokenTree::Token(token), is_joint)) = stream_lrc.first() { |
| // ...and the two tokens can be glued together... |
| if let Some(glued_tok) = last_token.glue(&token) { |
| // ...then do so, by overwriting the last token |
| // tree in `self` and removing the first token tree |
| // from `stream`. This requires using `make_mut()` |
| // on the last stream in `self` and on `stream`, |
| // and in practice this doesn't cause cloning 99.9% |
| // of the time. |
| |
| // Overwrite the last token tree with the merged |
| // token. |
| let last_vec_mut = Lrc::make_mut(last_stream_lrc); |
| *last_vec_mut.last_mut().unwrap() = |
| (TokenTree::Token(glued_tok), *is_joint); |
| |
| // Remove the first token tree from `stream`. (This |
| // is almost always the only tree in `stream`.) |
| let stream_vec_mut = Lrc::make_mut(stream_lrc); |
| stream_vec_mut.remove(0); |
| |
| // Don't push `stream` if it's empty -- that could |
| // block subsequent token gluing, by getting |
| // between two token trees that should be glued |
| // together. |
| if !stream.is_empty() { |
| self.0.push(stream); |
| } |
| return; |
| } |
| } |
| } |
| } |
| self.0.push(stream); |
| } |
| |
| pub fn build(self) -> TokenStream { |
| TokenStream::from_streams(self.0) |
| } |
| } |
| |
| #[derive(Clone)] |
| pub struct Cursor { |
| pub stream: TokenStream, |
| index: usize, |
| } |
| |
| impl Iterator for Cursor { |
| type Item = TokenTree; |
| |
| fn next(&mut self) -> Option<TokenTree> { |
| self.next_with_joint().map(|(tree, _)| tree) |
| } |
| } |
| |
| impl Cursor { |
| fn new(stream: TokenStream) -> Self { |
| Cursor { stream, index: 0 } |
| } |
| |
| pub fn next_with_joint(&mut self) -> Option<TreeAndJoint> { |
| if self.index < self.stream.len() { |
| self.index += 1; |
| Some(self.stream.0[self.index - 1].clone()) |
| } else { |
| None |
| } |
| } |
| |
| pub fn append(&mut self, new_stream: TokenStream) { |
| if new_stream.is_empty() { |
| return; |
| } |
| let index = self.index; |
| let stream = mem::take(&mut self.stream); |
| *self = TokenStream::from_streams(smallvec![stream, new_stream]).into_trees(); |
| self.index = index; |
| } |
| |
| pub fn look_ahead(&self, n: usize) -> Option<TokenTree> { |
| self.stream.0[self.index..].get(n).map(|(tree, _)| tree.clone()) |
| } |
| } |
| |
| #[derive(Debug, Copy, Clone, PartialEq, RustcEncodable, RustcDecodable, 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()) |
| } |
| } |