diff options
Diffstat (limited to 'compiler/rustc_ast/src/tokenstream.rs')
| -rw-r--r-- | compiler/rustc_ast/src/tokenstream.rs | 383 |
1 files changed, 366 insertions, 17 deletions
diff --git a/compiler/rustc_ast/src/tokenstream.rs b/compiler/rustc_ast/src/tokenstream.rs index 43d25d18075..636c26bcde0 100644 --- a/compiler/rustc_ast/src/tokenstream.rs +++ b/compiler/rustc_ast/src/tokenstream.rs @@ -14,14 +14,16 @@ //! ownership of the original. use std::borrow::Cow; +use std::ops::Range; use std::sync::Arc; -use std::{cmp, fmt, iter}; +use std::{cmp, fmt, iter, mem}; use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; use rustc_data_structures::sync; use rustc_macros::{Decodable, Encodable, HashStable_Generic}; use rustc_serialize::{Decodable, Encodable}; use rustc_span::{DUMMY_SP, Span, SpanDecoder, SpanEncoder, Symbol, sym}; +use thin_vec::ThinVec; use crate::ast::AttrStyle; use crate::ast_traits::{HasAttrs, HasTokens}; @@ -106,25 +108,30 @@ where } } -pub trait ToAttrTokenStream: sync::DynSend + sync::DynSync { - fn to_attr_token_stream(&self) -> AttrTokenStream; -} - -impl ToAttrTokenStream for AttrTokenStream { - fn to_attr_token_stream(&self) -> AttrTokenStream { - 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. +/// A lazy version of [`AttrTokenStream`], which defers creation of an actual +/// `AttrTokenStream` until it is needed. #[derive(Clone)] -pub struct LazyAttrTokenStream(Arc<Box<dyn ToAttrTokenStream>>); +pub struct LazyAttrTokenStream(Arc<LazyAttrTokenStreamInner>); impl LazyAttrTokenStream { - pub fn new(inner: impl ToAttrTokenStream + 'static) -> LazyAttrTokenStream { - LazyAttrTokenStream(Arc::new(Box::new(inner))) + pub fn new_direct(stream: AttrTokenStream) -> LazyAttrTokenStream { + LazyAttrTokenStream(Arc::new(LazyAttrTokenStreamInner::Direct(stream))) + } + + pub fn new_pending( + start_token: (Token, Spacing), + cursor_snapshot: TokenCursor, + num_calls: u32, + break_last_token: u32, + node_replacements: ThinVec<NodeReplacement>, + ) -> LazyAttrTokenStream { + LazyAttrTokenStream(Arc::new(LazyAttrTokenStreamInner::Pending { + start_token, + cursor_snapshot, + num_calls, + break_last_token, + node_replacements, + })) } pub fn to_attr_token_stream(&self) -> AttrTokenStream { @@ -156,6 +163,184 @@ impl<CTX> HashStable<CTX> for LazyAttrTokenStream { } } +/// A token range within a `Parser`'s full token stream. +#[derive(Clone, Debug)] +pub struct ParserRange(pub Range<u32>); + +/// A token range within an individual AST node's (lazy) token stream, i.e. +/// relative to that node's first token. Distinct from `ParserRange` so the two +/// kinds of range can't be mixed up. +#[derive(Clone, Debug)] +pub struct NodeRange(pub Range<u32>); + +/// Indicates a range of tokens that should be replaced by an `AttrsTarget` +/// (replacement) or be replaced by nothing (deletion). This is used in two +/// places during token collection. +/// +/// 1. Replacement. During the parsing of an AST node that may have a +/// `#[derive]` attribute, when we parse a nested AST node that has `#[cfg]` +/// or `#[cfg_attr]`, we replace the entire inner AST node with +/// `FlatToken::AttrsTarget`. This lets us perform eager cfg-expansion on an +/// `AttrTokenStream`. +/// +/// 2. Deletion. We delete inner attributes from all collected token streams, +/// and instead track them through the `attrs` field on the AST node. This +/// lets us manipulate them similarly to outer attributes. When we create a +/// `TokenStream`, the inner attributes are inserted into the proper place +/// in the token stream. +/// +/// Each replacement starts off in `ParserReplacement` form but is converted to +/// `NodeReplacement` form when it is attached to a single AST node, via +/// `LazyAttrTokenStreamImpl`. +pub type ParserReplacement = (ParserRange, Option<AttrsTarget>); + +/// See the comment on `ParserReplacement`. +pub type NodeReplacement = (NodeRange, Option<AttrsTarget>); + +impl NodeRange { + // Converts a range within a parser's tokens to a range within a + // node's tokens beginning at `start_pos`. + // + // For example, imagine a parser with 50 tokens in its token stream, a + // function that spans `ParserRange(20..40)` and an inner attribute within + // that function that spans `ParserRange(30..35)`. We would find the inner + // attribute's range within the function's tokens by subtracting 20, which + // is the position of the function's start token. This gives + // `NodeRange(10..15)`. + pub fn new(ParserRange(parser_range): ParserRange, start_pos: u32) -> NodeRange { + assert!(!parser_range.is_empty()); + assert!(parser_range.start >= start_pos); + NodeRange((parser_range.start - start_pos)..(parser_range.end - start_pos)) + } +} + +enum LazyAttrTokenStreamInner { + // The token stream has already been produced. + Direct(AttrTokenStream), + + // From a value of this type we can reconstruct the `TokenStream` seen by + // the `f` callback passed to a call to `Parser::collect_tokens`, by + // replaying the getting of the tokens. This saves us producing a + // `TokenStream` if it is never needed, e.g. a captured `macro_rules!` + // argument that is never passed to a proc macro. In practice, token stream + // creation happens rarely compared to calls to `collect_tokens` (see some + // statistics in #78736) so we are doing as little up-front work as + // possible. + // + // This also makes `Parser` very cheap to clone, since there is no + // intermediate collection buffer to clone. + Pending { + start_token: (Token, Spacing), + cursor_snapshot: TokenCursor, + num_calls: u32, + break_last_token: u32, + node_replacements: ThinVec<NodeReplacement>, + }, +} + +impl LazyAttrTokenStreamInner { + fn to_attr_token_stream(&self) -> AttrTokenStream { + match self { + LazyAttrTokenStreamInner::Direct(stream) => stream.clone(), + LazyAttrTokenStreamInner::Pending { + start_token, + cursor_snapshot, + num_calls, + break_last_token, + node_replacements, + } => { + // The token produced by the final call to `{,inlined_}next` was not + // actually consumed by the callback. The combination of chaining the + // initial token and using `take` produces the desired result - we + // produce an empty `TokenStream` if no calls were made, and omit the + // final token otherwise. + let mut cursor_snapshot = cursor_snapshot.clone(); + let tokens = iter::once(FlatToken::Token(*start_token)) + .chain(iter::repeat_with(|| FlatToken::Token(cursor_snapshot.next()))) + .take(*num_calls as usize); + + if node_replacements.is_empty() { + make_attr_token_stream(tokens, *break_last_token) + } else { + let mut tokens: Vec<_> = tokens.collect(); + let mut node_replacements = node_replacements.to_vec(); + node_replacements.sort_by_key(|(range, _)| range.0.start); + + #[cfg(debug_assertions)] + for [(node_range, tokens), (next_node_range, next_tokens)] in + node_replacements.array_windows() + { + assert!( + node_range.0.end <= next_node_range.0.start + || node_range.0.end >= next_node_range.0.end, + "Node ranges should be disjoint or nested: ({:?}, {:?}) ({:?}, {:?})", + node_range, + tokens, + next_node_range, + next_tokens, + ); + } + + // Process the replace ranges, starting from the highest start + // position and working our way back. If have tokens like: + // + // `#[cfg(FALSE)] struct Foo { #[cfg(FALSE)] field: bool }` + // + // Then we will generate replace ranges for both + // the `#[cfg(FALSE)] field: bool` and the entire + // `#[cfg(FALSE)] struct Foo { #[cfg(FALSE)] field: bool }` + // + // By starting processing from the replace range with the greatest + // start position, we ensure that any (outer) replace range which + // encloses another (inner) replace range will fully overwrite the + // inner range's replacement. + for (node_range, target) in node_replacements.into_iter().rev() { + assert!( + !node_range.0.is_empty(), + "Cannot replace an empty node range: {:?}", + node_range.0 + ); + + // Replace the tokens in range with zero or one `FlatToken::AttrsTarget`s, + // plus enough `FlatToken::Empty`s to fill up the rest of the range. This + // keeps the total length of `tokens` constant throughout the replacement + // process, allowing us to do all replacements without adjusting indices. + let target_len = target.is_some() as usize; + tokens.splice( + (node_range.0.start as usize)..(node_range.0.end as usize), + target.into_iter().map(|target| FlatToken::AttrsTarget(target)).chain( + iter::repeat(FlatToken::Empty) + .take(node_range.0.len() - target_len), + ), + ); + } + make_attr_token_stream(tokens.into_iter(), *break_last_token) + } + } + } + } +} + +/// A helper struct used when building an `AttrTokenStream` from +/// a `LazyAttrTokenStream`. Both delimiter and non-delimited tokens +/// are stored as `FlatToken::Token`. A vector of `FlatToken`s +/// is then 'parsed' to build up an `AttrTokenStream` with nested +/// `AttrTokenTree::Delimited` tokens. +#[derive(Debug, Clone)] +enum FlatToken { + /// A token - this holds both delimiter (e.g. '{' and '}') + /// and non-delimiter tokens + Token((Token, Spacing)), + /// Holds the `AttrsTarget` for an AST node. The `AttrsTarget` is inserted + /// directly into the constructed `AttrTokenStream` as an + /// `AttrTokenTree::AttrsTarget`. + AttrsTarget(AttrsTarget), + /// A special 'empty' token that is ignored during the conversion + /// to an `AttrTokenStream`. This is used to simplify the + /// handling of replace ranges. + Empty, +} + /// An `AttrTokenStream` is similar to a `TokenStream`, but with extra /// information about the tokens for attribute targets. This is used /// during expansion to perform early cfg-expansion, and to process attributes @@ -163,6 +348,71 @@ impl<CTX> HashStable<CTX> for LazyAttrTokenStream { #[derive(Clone, Debug, Default, Encodable, Decodable)] pub struct AttrTokenStream(pub Arc<Vec<AttrTokenTree>>); +/// Converts a flattened iterator of tokens (including open and close delimiter tokens) into an +/// `AttrTokenStream`, creating an `AttrTokenTree::Delimited` for each matching pair of open and +/// close delims. +fn make_attr_token_stream( + iter: impl Iterator<Item = FlatToken>, + break_last_token: u32, +) -> AttrTokenStream { + #[derive(Debug)] + struct FrameData { + // This is `None` for the first frame, `Some` for all others. + open_delim_sp: Option<(Delimiter, Span, Spacing)>, + inner: Vec<AttrTokenTree>, + } + // The stack always has at least one element. Storing it separately makes for shorter code. + let mut stack_top = FrameData { open_delim_sp: None, inner: vec![] }; + let mut stack_rest = vec![]; + for flat_token in iter { + match flat_token { + FlatToken::Token((token @ Token { kind, span }, spacing)) => { + if let Some(delim) = kind.open_delim() { + stack_rest.push(mem::replace( + &mut stack_top, + FrameData { open_delim_sp: Some((delim, span, spacing)), inner: vec![] }, + )); + } else if let Some(delim) = kind.close_delim() { + let frame_data = mem::replace(&mut stack_top, stack_rest.pop().unwrap()); + let (open_delim, open_sp, open_spacing) = frame_data.open_delim_sp.unwrap(); + assert!( + open_delim.eq_ignoring_invisible_origin(&delim), + "Mismatched open/close delims: open={open_delim:?} close={span:?}" + ); + let dspan = DelimSpan::from_pair(open_sp, span); + let dspacing = DelimSpacing::new(open_spacing, spacing); + let stream = AttrTokenStream::new(frame_data.inner); + let delimited = AttrTokenTree::Delimited(dspan, dspacing, delim, stream); + stack_top.inner.push(delimited); + } else { + stack_top.inner.push(AttrTokenTree::Token(token, spacing)) + } + } + FlatToken::AttrsTarget(target) => { + stack_top.inner.push(AttrTokenTree::AttrsTarget(target)) + } + FlatToken::Empty => {} + } + } + + if break_last_token > 0 { + let last_token = stack_top.inner.pop().unwrap(); + if let AttrTokenTree::Token(last_token, spacing) = last_token { + let (unglued, _) = last_token.kind.break_two_token_op(break_last_token).unwrap(); + + // Tokens are always ASCII chars, so we can use byte arithmetic here. + let mut first_span = last_token.span.shrink_to_lo(); + first_span = + first_span.with_hi(first_span.lo() + rustc_span::BytePos(break_last_token)); + + stack_top.inner.push(AttrTokenTree::Token(Token::new(unglued, first_span), spacing)); + } else { + panic!("Unexpected last token {last_token:?}") + } + } + AttrTokenStream::new(stack_top.inner) +} + /// Like `TokenTree`, but for `AttrTokenStream`. #[derive(Clone, Debug, Encodable, Decodable)] pub enum AttrTokenTree { @@ -641,6 +891,104 @@ impl<'t> Iterator for TokenStreamIter<'t> { } } +#[derive(Clone, Debug)] +pub struct TokenTreeCursor { + stream: TokenStream, + /// Points to the current token tree in the stream. In `TokenCursor::curr`, + /// this can be any token tree. In `TokenCursor::stack`, this is always a + /// `TokenTree::Delimited`. + index: usize, +} + +impl TokenTreeCursor { + #[inline] + pub fn new(stream: TokenStream) -> Self { + TokenTreeCursor { stream, index: 0 } + } + + #[inline] + pub fn curr(&self) -> Option<&TokenTree> { + self.stream.get(self.index) + } + + pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> { + self.stream.get(self.index + n) + } + + #[inline] + pub fn bump(&mut self) { + self.index += 1; + } +} + +/// A `TokenStream` cursor that produces `Token`s. It's a bit odd that +/// we (a) lex tokens into a nice tree structure (`TokenStream`), and then (b) +/// use this type to emit them as a linear sequence. But a linear sequence is +/// what the parser expects, for the most part. +#[derive(Clone, Debug)] +pub struct TokenCursor { + // Cursor for the current (innermost) token stream. The index within the + // cursor can point to any token tree in the stream (or one past the end). + // The delimiters for this token stream are found in `self.stack.last()`; + // if that is `None` we are in the outermost token stream which never has + // delimiters. + pub curr: TokenTreeCursor, + + // Token streams surrounding the current one. The index within each cursor + // always points to a `TokenTree::Delimited`. + pub stack: Vec<TokenTreeCursor>, +} + +impl TokenCursor { + pub fn next(&mut self) -> (Token, Spacing) { + self.inlined_next() + } + + /// This always-inlined version should only be used on hot code paths. + #[inline(always)] + pub fn inlined_next(&mut self) -> (Token, Spacing) { + loop { + // FIXME: we currently don't return `Delimiter::Invisible` open/close delims. To fix + // #67062 we will need to, whereupon the `delim != Delimiter::Invisible` conditions + // below can be removed. + if let Some(tree) = self.curr.curr() { + match tree { + &TokenTree::Token(token, spacing) => { + debug_assert!(!token.kind.is_delim()); + let res = (token, spacing); + self.curr.bump(); + return res; + } + &TokenTree::Delimited(sp, spacing, delim, ref tts) => { + let trees = TokenTreeCursor::new(tts.clone()); + self.stack.push(mem::replace(&mut self.curr, trees)); + if !delim.skip() { + return (Token::new(delim.as_open_token_kind(), sp.open), spacing.open); + } + // No open delimiter to return; continue on to the next iteration. + } + }; + } else if let Some(parent) = self.stack.pop() { + // We have exhausted this token stream. Move back to its parent token stream. + let Some(&TokenTree::Delimited(span, spacing, delim, _)) = parent.curr() else { + panic!("parent should be Delimited") + }; + self.curr = parent; + self.curr.bump(); // move past the `Delimited` + if !delim.skip() { + return (Token::new(delim.as_close_token_kind(), span.close), spacing.close); + } + // No close delimiter to return; continue on to the next iteration. + } else { + // We have exhausted the outermost token stream. The use of + // `Spacing::Alone` is arbitrary and immaterial, because the + // `Eof` token's spacing is never used. + return (Token::new(token::Eof, DUMMY_SP), Spacing::Alone); + } + } + } +} + #[derive(Debug, Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)] pub struct DelimSpan { pub open: Span, @@ -687,6 +1035,7 @@ mod size_asserts { static_assert_size!(AttrTokenStream, 8); static_assert_size!(AttrTokenTree, 32); static_assert_size!(LazyAttrTokenStream, 8); + static_assert_size!(LazyAttrTokenStreamInner, 88); static_assert_size!(Option<LazyAttrTokenStream>, 8); // must be small, used in many AST nodes static_assert_size!(TokenStream, 8); static_assert_size!(TokenTree, 32); |