--- /dev/null
+//! # Token Streams
+//!
+//! `TokenStream`s represent syntactic objects before they are converted into ASTs.
+//! A `TokenStream` is, roughly speaking, a sequence 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::{self, Lrc};
+use rustc_macros::HashStable_Generic;
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
+use rustc_span::{Span, DUMMY_SP};
+use smallvec::{smallvec, SmallVec};
+
+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, Encodable, Decodable, HashStable_Generic)]
+pub enum TokenTree {
+ /// A single token.
+ Token(Token),
+ /// A delimited sequence of token trees.
+ Delimited(DelimSpan, DelimToken, TokenStream),
+}
+
+#[derive(Copy, Clone)]
+pub enum CanSynthesizeMissingTokens {
+ Yes,
+ No,
+}
+
+// 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,
+ }
+ }
+
+ /// 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, Spacing::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);
+ }
+ }
+}
+
+pub trait CreateTokenStream: sync::Send + sync::Sync {
+ fn create_token_stream(&self) -> TokenStream;
+}
+
+impl CreateTokenStream for TokenStream {
+ fn create_token_stream(&self) -> TokenStream {
+ self.clone()
+ }
+}
+
+/// A lazy version of [`TokenStream`], which defers creation
+/// of an actual `TokenStream` until it is needed.
+/// `Box` is here only to reduce the structure size.
+#[derive(Clone)]
+pub struct LazyTokenStream(Lrc<Box<dyn CreateTokenStream>>);
+
+impl LazyTokenStream {
+ pub fn new(inner: impl CreateTokenStream + 'static) -> LazyTokenStream {
+ LazyTokenStream(Lrc::new(Box::new(inner)))
+ }
+
+ pub fn create_token_stream(&self) -> TokenStream {
+ self.0.create_token_stream()
+ }
+}
+
+impl fmt::Debug for LazyTokenStream {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt("LazyTokenStream", f)
+ }
+}
+
+impl<S: Encoder> Encodable<S> for LazyTokenStream {
+ fn encode(&self, s: &mut S) -> Result<(), S::Error> {
+ // Used by AST json printing.
+ Encodable::encode(&self.create_token_stream(), s)
+ }
+}
+
+impl<D: Decoder> Decodable<D> for LazyTokenStream {
+ fn decode(_d: &mut D) -> Result<Self, D::Error> {
+ panic!("Attempted to decode LazyTokenStream");
+ }
+}
+
+impl<CTX> HashStable<CTX> for LazyTokenStream {
+ fn hash_stable(&self, _hcx: &mut CTX, _hasher: &mut StableHasher) {
+ panic!("Attempted to compute stable hash for LazyTokenStream");
+ }
+}
+
+/// 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
+/// backwards compatability.
+#[derive(Clone, Debug, Default, Encodable, Decodable)]
+pub struct TokenStream(pub(crate) Lrc<Vec<TreeAndSpacing>>);
+
+pub type TreeAndSpacing = (TokenTree, Spacing);
+
+// `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, Encodable, Decodable)]
+pub enum Spacing {
+ Alone,
+ Joint,
+}
+
+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), Spacing::Alone),
+ (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, ..), Spacing::Alone), _) => sp.entire(),
+ _ => continue,
+ };
+ let sp = sp.shrink_to_hi();
+ let comma = (TokenTree::token(token::Comma, sp), Spacing::Alone);
+ suggestion = Some((pos, comma, sp));
+ }
+ }
+ if let Some((pos, comma, sp)) = suggestion {
+ let mut new_stream = Vec::with_capacity(self.0.len() + 1);
+ 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, Spacing::Alone)])
+ }
+}
+
+impl From<TokenTree> for TreeAndSpacing {
+ fn from(tree: TokenTree) -> TreeAndSpacing {
+ (tree, Spacing::Alone)
+ }
+}
+
+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<TreeAndSpacing>>())
+ }
+}
+
+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<TreeAndSpacing>) -> 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_ref(&self) -> CursorRef<'_> {
+ CursorRef::new(self)
+ }
+
+ 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()
+ }
+
+ 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), *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), Spacing::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), spacing)) = 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), *spacing);
+
+ // 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)
+ }
+}
+
+/// By-reference iterator over a [`TokenStream`].
+#[derive(Clone)]
+pub struct CursorRef<'t> {
+ stream: &'t TokenStream,
+ index: usize,
+}
+
+impl<'t> CursorRef<'t> {
+ fn new(stream: &TokenStream) -> CursorRef<'_> {
+ CursorRef { stream, index: 0 }
+ }
+
+ fn next_with_spacing(&mut self) -> Option<&'t TreeAndSpacing> {
+ self.stream.0.get(self.index).map(|tree| {
+ self.index += 1;
+ tree
+ })
+ }
+}
+
+impl<'t> Iterator for CursorRef<'t> {
+ type Item = &'t TokenTree;
+
+ fn next(&mut self) -> Option<&'t TokenTree> {
+ self.next_with_spacing().map(|(tree, _)| tree)
+ }
+}
+
+/// Owning by-value iterator over a [`TokenStream`].
+// FIXME: Many uses of this can be replaced with by-reference iterator to avoid clones.
+#[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_spacing().map(|(tree, _)| tree)
+ }
+}
+
+impl Cursor {
+ fn new(stream: TokenStream) -> Self {
+ Cursor { stream, index: 0 }
+ }
+
+ pub fn next_with_spacing(&mut self) -> Option<TreeAndSpacing> {
+ 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)
+ }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Encodable, Decodable, 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())
+ }
+}
projects / rustc.git / blobdiff