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//! # 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<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")]
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<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<T: Into<TokenStream>> iter::FromIterator<T> for TokenStream {
fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
TokenStream::from_streams(iter.into_iter().map(Into::into).collect::<SmallVec<_>>())
}
}
impl Eq for TokenStream {}
impl PartialEq<TokenStream> 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<TreeAndJoint>) -> TokenStream {
match streams.len() {
0 => TokenStream(None),
_ => TokenStream(Some(Lrc::new(streams))),
}
}
pub fn append_to_tree_and_joint_vec(self, vec: &mut Vec<TreeAndJoint>) {
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<F: FnMut(usize, TokenTree) -> 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<F: FnMut(TokenTree) -> 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<TreeAndJoint> {
self.0.as_ref().map(|stream| {
stream.first().unwrap().clone()
})
}
fn last_tree_if_joint(&self) -> Option<TokenTree> {
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<T: Into<TokenStream>>(&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<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> {
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<TokenTree> {
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<E: Encoder>(&self, encoder: &mut E) -> Result<(), E::Error> {
self.trees().collect::<Vec<_>>().encode(encoder)
}
}
impl Decodable for TokenStream {
fn decode<D: Decoder>(decoder: &mut D) -> Result<TokenStream, D::Error> {
Vec::<TokenTree>::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::<TokenTree>::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);
})
}
}
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