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Lint small gaps between ranges

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Nadrieril
2024-01-14 22:24:10 +01:00
parent f783043ebf
commit 8ac9a04257
7 changed files with 492 additions and 12 deletions
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46
compiler/rustc_pattern_analysis/src/usefulness.rs
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@@ -1489,7 +1489,7 @@ impl<Cx: TypeCx> WitnessMatrix<Cx> {
/// We can however get false negatives because exhaustiveness does not explore all cases. See the
/// section on relevancy at the top of the file.
fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
mcx: &mut UsefulnessCtxt<'_, Cx>,
cx: &Cx,
overlap_range: IntRange,
matrix: &Matrix<'p, Cx>,
specialized_matrix: &Matrix<'p, Cx>,
@@ -1522,7 +1522,7 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
.map(|&(_, pat)| pat)
.collect();
if !overlaps_with.is_empty() {
mcx.tycx.lint_overlapping_range_endpoints(pat, overlap_range, &overlaps_with);
cx.lint_overlapping_range_endpoints(pat, overlap_range, &overlaps_with);
}
}
suffixes.push((child_row_id, pat))
@@ -1538,7 +1538,7 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
.map(|&(_, pat)| pat)
.collect();
if !overlaps_with.is_empty() {
mcx.tycx.lint_overlapping_range_endpoints(pat, overlap_range, &overlaps_with);
cx.lint_overlapping_range_endpoints(pat, overlap_range, &overlaps_with);
}
}
prefixes.push((child_row_id, pat))
@@ -1546,6 +1546,33 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
}
}
/// Collect ranges that have a singleton gap between them.
fn collect_non_contiguous_range_endpoints<'p, Cx: TypeCx>(
cx: &Cx,
gap_range: &IntRange,
matrix: &Matrix<'p, Cx>,
) {
let gap = gap_range.lo;
// Ranges that look like `lo..gap`.
let mut onebefore: SmallVec<[_; 1]> = Default::default();
// Ranges that start on `gap+1` or singletons `gap+1`.
let mut oneafter: SmallVec<[_; 1]> = Default::default();
// Look through the column for ranges near the gap.
for pat in matrix.heads() {
let PatOrWild::Pat(pat) = pat else { continue };
let Constructor::IntRange(this_range) = pat.ctor() else { continue };
if gap == this_range.hi {
onebefore.push(pat)
} else if gap.plus_one() == Some(this_range.lo) {
oneafter.push(pat)
}
}
for pat_before in onebefore {
cx.lint_non_contiguous_range_endpoints(pat_before, *gap_range, oneafter.as_slice());
}
}
/// The core of the algorithm.
///
/// This recursively computes witnesses of the non-exhaustiveness of `matrix` (if any). Also tracks
@@ -1626,13 +1653,24 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
&& spec_matrix.rows.len() >= 2
&& spec_matrix.rows.iter().any(|row| !row.intersects.is_empty())
{
collect_overlapping_range_endpoints(mcx, overlap_range, matrix, &spec_matrix);
collect_overlapping_range_endpoints(mcx.tycx, overlap_range, matrix, &spec_matrix);
}
}
matrix.unspecialize(spec_matrix);
}
// Detect singleton gaps between ranges.
if missing_ctors.iter().any(|c| matches!(c, Constructor::IntRange(..))) {
for missing in &missing_ctors {
if let Constructor::IntRange(gap) = missing {
if gap.is_singleton() {
collect_non_contiguous_range_endpoints(mcx.tycx, gap, matrix);
}
}
}
}
// Record usefulness in the patterns.
for row in matrix.rows() {
if row.useful {