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rustc_span: represent line bounds with Range
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tgnottingham committed Oct 27, 2020
1 parent df59a44 commit 47dad31
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Showing 2 changed files with 24 additions and 30 deletions.
44 changes: 19 additions & 25 deletions compiler/rustc_span/src/caching_source_map_view.rs
Original file line number Diff line number Diff line change
@@ -1,13 +1,25 @@
use crate::source_map::SourceMap;
use crate::{BytePos, SourceFile};
use rustc_data_structures::sync::Lrc;
use std::ops::Range;

#[derive(Clone)]
struct CacheEntry {
time_stamp: usize,
line_number: usize,
line_start: BytePos,
line_end: BytePos,
// The line's byte position range in the `SourceMap`. This range will fail to contain a valid
// position in certain edge cases. Spans often start/end one past something, and when that
// something is the last character of a file (this can happen when a file doesn't end in a
// newline, for example), we'd still like for the position to be considered within the last
// line. However, it isn't according to the exclusive upper bound of this range. We cannot
// change the upper bound to be inclusive, because for most lines, the upper bound is the same
// as the lower bound of the next line, so there would be an ambiguity.
//
// Since the containment aspect of this range is only used to see whether or not the cache
// entry contains a position, the only ramification of the above is that we will get cache
// misses for these rare positions. A line lookup for the position via `SourceMap::lookup_line`
// after a cache miss will produce the last line number, as desired.
line: Range<BytePos>,
file: Lrc<SourceFile>,
file_index: usize,
}
Expand All @@ -26,8 +38,7 @@ impl<'sm> CachingSourceMapView<'sm> {
let entry = CacheEntry {
time_stamp: 0,
line_number: 0,
line_start: BytePos(0),
line_end: BytePos(0),
line: BytePos(0)..BytePos(0),
file: first_file,
file_index: 0,
};
Expand All @@ -47,13 +58,13 @@ impl<'sm> CachingSourceMapView<'sm> {

// Check if the position is in one of the cached lines
for cache_entry in self.line_cache.iter_mut() {
if line_contains((cache_entry.line_start, cache_entry.line_end), pos) {
if cache_entry.line.contains(&pos) {
cache_entry.time_stamp = self.time_stamp;

return Some((
cache_entry.file.clone(),
cache_entry.line_number,
pos - cache_entry.line_start,
pos - cache_entry.line.start,
));
}
}
Expand Down Expand Up @@ -95,30 +106,13 @@ impl<'sm> CachingSourceMapView<'sm> {
let line_bounds = cache_entry.file.line_bounds(line_index);

cache_entry.line_number = line_index + 1;
cache_entry.line_start = line_bounds.0;
cache_entry.line_end = line_bounds.1;
cache_entry.line = line_bounds;
cache_entry.time_stamp = self.time_stamp;

Some((cache_entry.file.clone(), cache_entry.line_number, pos - cache_entry.line_start))
Some((cache_entry.file.clone(), cache_entry.line_number, pos - cache_entry.line.start))
}
}

#[inline]
fn line_contains(line_bounds: (BytePos, BytePos), pos: BytePos) -> bool {
// This condition will be false in one case where we'd rather it wasn't. Spans often start/end
// one past something, and when that something is the last character of a file (this can happen
// when a file doesn't end in a newline, for example), we'd still like for the position to be
// considered within the last line. However, it isn't according to the exclusive upper bound
// below. We cannot change the upper bound to be inclusive, because for most lines, the upper
// bound is the same as the lower bound of the next line, so there would be an ambiguity.
//
// Supposing we only use this function to check whether or not the line cache entry contains
// a position, the only ramification of the above is that we will get cache misses for these
// rare positions. A line lookup for the position via `SourceMap::lookup_line` after a cache
// miss will produce the last line number, as desired.
line_bounds.0 <= pos && pos < line_bounds.1
}

#[inline]
fn file_contains(file: &SourceFile, pos: BytePos) -> bool {
// `SourceMap::lookup_source_file_idx` and `SourceFile::contains` both consider the position
Expand Down
10 changes: 5 additions & 5 deletions compiler/rustc_span/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -52,7 +52,7 @@ use std::cell::RefCell;
use std::cmp::{self, Ordering};
use std::fmt;
use std::hash::Hash;
use std::ops::{Add, Sub};
use std::ops::{Add, Range, Sub};
use std::path::{Path, PathBuf};
use std::str::FromStr;

Expand Down Expand Up @@ -1426,16 +1426,16 @@ impl SourceFile {
if line_index >= 0 { Some(line_index as usize) } else { None }
}

pub fn line_bounds(&self, line_index: usize) -> (BytePos, BytePos) {
pub fn line_bounds(&self, line_index: usize) -> Range<BytePos> {
if self.is_empty() {
return (self.start_pos, self.end_pos);
return self.start_pos..self.end_pos;
}

assert!(line_index < self.lines.len());
if line_index == (self.lines.len() - 1) {
(self.lines[line_index], self.end_pos)
self.lines[line_index]..self.end_pos
} else {
(self.lines[line_index], self.lines[line_index + 1])
self.lines[line_index]..self.lines[line_index + 1]
}
}

Expand Down

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