//! # 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 //! //! `TokenStreams` 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::ext::base; use crate::ext::tt::{macro_parser, quoted}; use crate::parse::Directory; use crate::parse::token::{self, DelimToken, Token, TokenKind}; use crate::print::pprust; use syntax_pos::{BytePos, ExpnId, Span, DUMMY_SP}; #[cfg(target_arch = "x86_64")] use rustc_data_structures::static_assert_size; use rustc_data_structures::sync::Lrc; use serialize::{Decoder, Decodable, Encoder, Encodable}; use smallvec::{SmallVec, smallvec}; use std::borrow::Cow; use std::{fmt, 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)] 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 { /// Use this token tree as a matcher to parse given tts. pub fn parse(cx: &base::ExtCtxt<'_>, mtch: &[quoted::TokenTree], tts: TokenStream) -> macro_parser::NamedParseResult { // `None` is because we're not interpolating let directory = Directory { path: Cow::from(cx.current_expansion.module.directory.as_path()), ownership: cx.current_expansion.directory_ownership, }; macro_parser::parse(cx.parse_sess(), tts, mtch, Some(directory), true) } /// 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: Span, delim: DelimToken) -> TokenTree { let open_span = if span.is_dummy() { span } else { span.with_hi(span.lo() + BytePos(delim.len() as u32)) }; TokenTree::token(token::OpenDelim(delim), open_span) } /// Returns the closing delimiter as a token tree. pub fn close_tt(span: Span, delim: DelimToken) -> TokenTree { let close_span = if span.is_dummy() { span } else { span.with_lo(span.hi() - BytePos(delim.len() as u32)) }; TokenTree::token(token::CloseDelim(delim), close_span) } } /// # Token Streams /// /// 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. /// /// The use of `Option` is an optimization that avoids the need for an /// allocation when the stream is empty. However, it is not guaranteed that an /// empty stream is represented with `None`; it may be represented as a `Some` /// around an empty `Vec`. #[derive(Clone, Debug)] pub struct TokenStream(pub Option>>); pub type TreeAndJoint = (TokenTree, IsJoint); // `TokenStream` is used a lot. Make sure it doesn't unintentionally get bigger. #[cfg(target_arch = "x86_64")] static_assert_size!(TokenStream, 8); #[derive(Clone, Copy, Debug, PartialEq)] 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(crate) fn add_comma(&self) -> Option<(TokenStream, Span)> { // Used to suggest if a user writes `foo!(a b);` if let Some(ref stream) = self.0 { let mut suggestion = None; let mut iter = stream.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 = stream.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 for TokenStream { fn from(tree: TokenTree) -> TokenStream { TokenStream::new(vec![(tree, NonJoint)]) } } impl From for TreeAndJoint { fn from(tree: TokenTree) -> TreeAndJoint { (tree, NonJoint) } } impl> iter::FromIterator for TokenStream { fn from_iter>(iter: I) -> Self { TokenStream::from_streams(iter.into_iter().map(Into::into).collect::>()) } } impl Eq for TokenStream {} impl PartialEq for TokenStream { fn eq(&self, other: &TokenStream) -> bool { self.trees().eq(other.trees()) } } impl TokenStream { pub fn len(&self) -> usize { if let Some(ref slice) = self.0 { slice.len() } else { 0 } } pub fn empty() -> TokenStream { TokenStream(None) } pub fn is_empty(&self) -> bool { match self.0 { None => true, Some(ref stream) => stream.is_empty(), } } pub(crate) fn from_streams(mut streams: SmallVec<[TokenStream; 2]>) -> TokenStream { match streams.len() { 0 => TokenStream::empty(), 1 => streams.pop().unwrap(), _ => { // rust-lang/rust#57735: pre-allocate vector to avoid // quadratic blow-up due to on-the-fly reallocations. let tree_count = streams.iter() .map(|ts| match &ts.0 { None => 0, Some(s) => s.len() }) .sum(); let mut vec = Vec::with_capacity(tree_count); for stream in streams { match stream.0 { None => {}, Some(stream2) => vec.extend(stream2.iter().cloned()), } } TokenStream::new(vec) } } } pub fn new(streams: Vec) -> TokenStream { match streams.len() { 0 => TokenStream(None), _ => TokenStream(Some(Lrc::new(streams))), } } pub fn append_to_tree_and_joint_vec(self, vec: &mut Vec) { if let Some(stream) = self.0 { vec.extend(stream.iter().cloned()); } } pub fn trees(&self) -> Cursor { self.clone().into_trees() } pub fn into_trees(self) -> Cursor { Cursor::new(self) } /// Compares two TokenStreams, 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 TokenTree>(self, mut f: F) -> TokenStream { TokenStream(self.0.map(|stream| { Lrc::new( stream .iter() .enumerate() .map(|(i, (tree, is_joint))| (f(i, tree.clone()), *is_joint)) .collect()) })) } pub fn map TokenTree>(self, mut f: F) -> TokenStream { TokenStream(self.0.map(|stream| { Lrc::new( stream .iter() .map(|(tree, is_joint)| (f(tree.clone()), *is_joint)) .collect()) })) } fn first_tree_and_joint(&self) -> Option { self.0.as_ref().map(|stream| { stream.first().unwrap().clone() }) } fn last_tree_if_joint(&self) -> Option { match self.0 { None => None, Some(ref stream) => { if let (tree, Joint) = stream.last().unwrap() { Some(tree.clone()) } else { None } } } } } // 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>(&mut self, stream: T) { let stream = stream.into(); let last_tree_if_joint = self.0.last().and_then(TokenStream::last_tree_if_joint); if let Some(TokenTree::Token(last_token)) = last_tree_if_joint { if let Some((TokenTree::Token(token), is_joint)) = stream.first_tree_and_joint() { if let Some(glued_tok) = last_token.glue(token) { let last_stream = self.0.pop().unwrap(); self.push_all_but_last_tree(&last_stream); let glued_tt = TokenTree::Token(glued_tok); let glued_tokenstream = TokenStream::new(vec![(glued_tt, is_joint)]); self.0.push(glued_tokenstream); self.push_all_but_first_tree(&stream); return } } } self.0.push(stream); } pub fn build(self) -> TokenStream { TokenStream::from_streams(self.0) } fn push_all_but_last_tree(&mut self, stream: &TokenStream) { if let Some(ref streams) = stream.0 { let len = streams.len(); match len { 1 => {} _ => self.0.push(TokenStream(Some(Lrc::new(streams[0 .. len - 1].to_vec())))), } } } fn push_all_but_first_tree(&mut self, stream: &TokenStream) { if let Some(ref streams) = stream.0 { let len = streams.len(); match len { 1 => {} _ => self.0.push(TokenStream(Some(Lrc::new(streams[1 .. len].to_vec())))), } } } } #[derive(Clone)] pub struct Cursor { pub stream: TokenStream, index: usize, } impl Iterator for Cursor { type Item = TokenTree; fn next(&mut self) -> Option { 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 { match self.stream.0 { None => None, Some(ref stream) => { if self.index < stream.len() { self.index += 1; Some(stream[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::replace(&mut self.stream, TokenStream(None)); *self = TokenStream::from_streams(smallvec![stream, new_stream]).into_trees(); self.index = index; } pub fn look_ahead(&self, n: usize) -> Option { match self.stream.0 { None => None, Some(ref stream) => stream[self.index ..].get(n).map(|(tree, _)| tree.clone()), } } } impl fmt::Display for TokenStream { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.write_str(&pprust::tokens_to_string(self.clone())) } } impl Encodable for TokenStream { fn encode(&self, encoder: &mut E) -> Result<(), E::Error> { self.trees().collect::>().encode(encoder) } } impl Decodable for TokenStream { fn decode(decoder: &mut D) -> Result { Vec::::decode(decoder).map(|vec| vec.into_iter().collect()) } } #[derive(Debug, Copy, Clone, PartialEq, RustcEncodable, RustcDecodable)] 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()) } pub fn apply_mark(self, expn_id: ExpnId) -> Self { DelimSpan { open: self.open.apply_mark(expn_id), close: self.close.apply_mark(expn_id), } } } #[cfg(test)] mod tests { use super::*; use crate::ast::Name; use crate::with_default_globals; use crate::util::parser_testing::string_to_stream; use syntax_pos::{Span, BytePos, NO_EXPANSION}; fn string_to_ts(string: &str) -> TokenStream { string_to_stream(string.to_owned()) } fn sp(a: u32, b: u32) -> Span { Span::new(BytePos(a), BytePos(b), NO_EXPANSION) } #[test] fn test_concat() { with_default_globals(|| { let test_res = string_to_ts("foo::bar::baz"); let test_fst = string_to_ts("foo::bar"); let test_snd = string_to_ts("::baz"); let eq_res = TokenStream::from_streams(smallvec![test_fst, test_snd]); assert_eq!(test_res.trees().count(), 5); assert_eq!(eq_res.trees().count(), 5); assert_eq!(test_res.eq_unspanned(&eq_res), true); }) } #[test] fn test_to_from_bijection() { with_default_globals(|| { let test_start = string_to_ts("foo::bar(baz)"); let test_end = test_start.trees().collect(); assert_eq!(test_start, test_end) }) } #[test] fn test_eq_0() { with_default_globals(|| { let test_res = string_to_ts("foo"); let test_eqs = string_to_ts("foo"); assert_eq!(test_res, test_eqs) }) } #[test] fn test_eq_1() { with_default_globals(|| { let test_res = string_to_ts("::bar::baz"); let test_eqs = string_to_ts("::bar::baz"); assert_eq!(test_res, test_eqs) }) } #[test] fn test_eq_3() { with_default_globals(|| { let test_res = string_to_ts(""); let test_eqs = string_to_ts(""); assert_eq!(test_res, test_eqs) }) } #[test] fn test_diseq_0() { with_default_globals(|| { let test_res = string_to_ts("::bar::baz"); let test_eqs = string_to_ts("bar::baz"); assert_eq!(test_res == test_eqs, false) }) } #[test] fn test_diseq_1() { with_default_globals(|| { let test_res = string_to_ts("(bar,baz)"); let test_eqs = string_to_ts("bar,baz"); assert_eq!(test_res == test_eqs, false) }) } #[test] fn test_is_empty() { with_default_globals(|| { let test0: TokenStream = Vec::::new().into_iter().collect(); let test1: TokenStream = TokenTree::token(token::Ident(Name::intern("a"), false), sp(0, 1)).into(); let test2 = string_to_ts("foo(bar::baz)"); assert_eq!(test0.is_empty(), true); assert_eq!(test1.is_empty(), false); assert_eq!(test2.is_empty(), false); }) } #[test] fn test_dotdotdot() { with_default_globals(|| { let mut builder = TokenStreamBuilder::new(); builder.push(TokenTree::token(token::Dot, sp(0, 1)).joint()); builder.push(TokenTree::token(token::Dot, sp(1, 2)).joint()); builder.push(TokenTree::token(token::Dot, sp(2, 3))); let stream = builder.build(); assert!(stream.eq_unspanned(&string_to_ts("..."))); assert_eq!(stream.trees().count(), 1); }) } }