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https://github.com/rust-lang/rust-analyzer.git
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b275f37db6
Because it took me hours to figure out that contrary to common sense, the offset stored is the *end* of the node, and we search by the *start*. Which is why we need a convoluted `partition_point()` instead of a simple `binary_search()`. And this was not documented at all. Which made me make mistakes with my implementation of `SpanMap::merge()`. The other bug fixed about span map merging is correctly keeping track of the current offset in presence of multiple sibling macro invocations. Unrelated, but because of the previous issue it took me hours to debug, so I figured out I'll put them together for posterity.
211 lines
7.9 KiB
Rust
211 lines
7.9 KiB
Rust
//! A map that maps a span to every position in a file. Usually maps a span to some range of positions.
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//! Allows bidirectional lookup.
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use std::{fmt, hash::Hash};
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use stdx::{always, itertools::Itertools};
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use crate::{
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EditionedFileId, ErasedFileAstId, Span, SpanAnchor, SpanData, SyntaxContextId, TextRange,
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TextSize, ROOT_ERASED_FILE_AST_ID,
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};
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/// Maps absolute text ranges for the corresponding file to the relevant span data.
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#[derive(Debug, PartialEq, Eq, Clone, Hash)]
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pub struct SpanMap<S> {
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/// The offset stored here is the *end* of the node.
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spans: Vec<(TextSize, SpanData<S>)>,
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/// Index of the matched macro arm on successful expansion for declarative macros.
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// FIXME: Does it make sense to have this here?
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pub matched_arm: Option<u32>,
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}
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impl<S> SpanMap<S>
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where
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SpanData<S>: Copy,
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{
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/// Creates a new empty [`SpanMap`].
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pub fn empty() -> Self {
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Self { spans: Vec::new(), matched_arm: None }
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}
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/// Finalizes the [`SpanMap`], shrinking its backing storage and validating that the offsets are
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/// in order.
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pub fn finish(&mut self) {
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always!(
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self.spans.iter().tuple_windows().all(|(a, b)| a.0 < b.0),
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"spans are not in order"
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);
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self.spans.shrink_to_fit();
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}
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/// Pushes a new span onto the [`SpanMap`].
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pub fn push(&mut self, offset: TextSize, span: SpanData<S>) {
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if cfg!(debug_assertions) {
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if let Some(&(last_offset, _)) = self.spans.last() {
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assert!(
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last_offset < offset,
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"last_offset({last_offset:?}) must be smaller than offset({offset:?})"
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);
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}
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}
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self.spans.push((offset, span));
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}
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/// Returns all [`TextRange`]s that correspond to the given span.
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///
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/// Note this does a linear search through the entire backing vector.
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pub fn ranges_with_span_exact(&self, span: SpanData<S>) -> impl Iterator<Item = TextRange> + '_
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where
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S: Copy,
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{
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self.spans.iter().enumerate().filter_map(move |(idx, &(end, s))| {
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if !s.eq_ignoring_ctx(span) {
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return None;
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}
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let start = idx.checked_sub(1).map_or(TextSize::new(0), |prev| self.spans[prev].0);
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Some(TextRange::new(start, end))
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})
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}
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/// Returns all [`TextRange`]s whose spans contain the given span.
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///
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/// Note this does a linear search through the entire backing vector.
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pub fn ranges_with_span(&self, span: SpanData<S>) -> impl Iterator<Item = TextRange> + '_
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where
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S: Copy,
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{
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self.spans.iter().enumerate().filter_map(move |(idx, &(end, s))| {
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if s.anchor != span.anchor {
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return None;
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}
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if !s.range.contains_range(span.range) {
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return None;
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}
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let start = idx.checked_sub(1).map_or(TextSize::new(0), |prev| self.spans[prev].0);
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Some(TextRange::new(start, end))
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})
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}
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/// Returns the span at the given position.
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pub fn span_at(&self, offset: TextSize) -> SpanData<S> {
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let entry = self.spans.partition_point(|&(it, _)| it <= offset);
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self.spans[entry].1
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}
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/// Returns the spans associated with the given range.
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/// In other words, this will return all spans that correspond to all offsets within the given range.
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pub fn spans_for_range(&self, range: TextRange) -> impl Iterator<Item = SpanData<S>> + '_ {
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let (start, end) = (range.start(), range.end());
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let start_entry = self.spans.partition_point(|&(it, _)| it <= start);
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let end_entry = self.spans[start_entry..].partition_point(|&(it, _)| it <= end); // FIXME: this might be wrong?
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self.spans[start_entry..][..end_entry].iter().map(|&(_, s)| s)
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}
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pub fn iter(&self) -> impl Iterator<Item = (TextSize, SpanData<S>)> + '_ {
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self.spans.iter().copied()
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}
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/// Merges this span map with another span map, where `other` is inserted at (and replaces) `other_range`.
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///
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/// The length of the replacement node needs to be `other_size`.
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pub fn merge(&mut self, other_range: TextRange, other_size: TextSize, other: &SpanMap<S>) {
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// I find the following diagram helpful to illustrate the bounds and why we use `<` or `<=`:
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// --------------------------------------------------------------------
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// 1 3 5 6 7 10 11 <-- offsets we store
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// 0-1 1-3 3-5 5-6 6-7 7-10 10-11 <-- ranges these offsets refer to
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// 3 .. 7 <-- other_range
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// 3-5 5-6 6-7 <-- ranges we replace (len = 7-3 = 4)
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// ^^^^^^^^^^^ ^^^^^^^^^^
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// remove shift
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// 2 3 5 9 <-- offsets we insert
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// 0-2 2-3 3-5 5-9 <-- ranges we insert (other_size = 9-0 = 9)
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// ------------------------------------
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// 1 3
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// 0-1 1-3 <-- these remain intact
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// 5 6 8 12
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// 3-5 5-6 6-8 8-12 <-- we shift these by other_range.start() and insert them
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// 15 16
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// 12-15 15-16 <-- we shift these by other_size-other_range.len() = 9-4 = 5
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// ------------------------------------
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// 1 3 5 6 8 12 15 16 <-- final offsets we store
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// 0-1 1-3 3-5 5-6 6-8 8-12 12-15 15-16 <-- final ranges
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self.spans.retain_mut(|(offset, _)| {
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if other_range.start() < *offset && *offset <= other_range.end() {
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false
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} else {
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if *offset > other_range.end() {
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*offset += other_size;
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*offset -= other_range.len();
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}
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true
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}
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});
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self.spans
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.extend(other.spans.iter().map(|&(offset, span)| (offset + other_range.start(), span)));
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self.spans.sort_unstable_by_key(|&(offset, _)| offset);
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// Matched arm info is no longer correct once we have multiple macros.
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self.matched_arm = None;
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}
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}
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#[derive(PartialEq, Eq, Hash, Debug)]
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pub struct RealSpanMap {
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file_id: EditionedFileId,
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/// Invariant: Sorted vec over TextSize
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// FIXME: SortedVec<(TextSize, ErasedFileAstId)>?
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pairs: Box<[(TextSize, ErasedFileAstId)]>,
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end: TextSize,
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}
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impl fmt::Display for RealSpanMap {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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writeln!(f, "RealSpanMap({:?}):", self.file_id)?;
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for span in self.pairs.iter() {
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writeln!(f, "{}: {}", u32::from(span.0), span.1.into_raw())?;
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}
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Ok(())
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}
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}
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impl RealSpanMap {
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/// Creates a real file span map that returns absolute ranges (relative ranges to the root ast id).
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pub fn absolute(file_id: EditionedFileId) -> Self {
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RealSpanMap {
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file_id,
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pairs: Box::from([(TextSize::new(0), ROOT_ERASED_FILE_AST_ID)]),
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end: TextSize::new(!0),
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}
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}
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pub fn from_file(
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file_id: EditionedFileId,
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pairs: Box<[(TextSize, ErasedFileAstId)]>,
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end: TextSize,
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) -> Self {
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Self { file_id, pairs, end }
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}
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pub fn span_for_range(&self, range: TextRange) -> Span {
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assert!(
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range.end() <= self.end,
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"range {range:?} goes beyond the end of the file {:?}",
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self.end
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);
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let start = range.start();
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let idx = self
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.pairs
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.binary_search_by(|&(it, _)| it.cmp(&start).then(std::cmp::Ordering::Less))
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.unwrap_err();
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let (offset, ast_id) = self.pairs[idx - 1];
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Span {
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range: range - offset,
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anchor: SpanAnchor { file_id: self.file_id, ast_id },
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ctx: SyntaxContextId::ROOT,
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}
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}
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}
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