diff options
Diffstat (limited to 'compiler/rustc_pattern_analysis/src/usefulness.rs')
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/usefulness.rs | 48 |
1 files changed, 43 insertions, 5 deletions
diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs index c518844cc5e..a067bf1f0c2 100644 --- a/compiler/rustc_pattern_analysis/src/usefulness.rs +++ b/compiler/rustc_pattern_analysis/src/usefulness.rs @@ -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>, @@ -1522,11 +1522,11 @@ 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)) - } else if this_range.hi == overlap.plus_one() { + } else if Some(this_range.hi) == overlap.plus_one() { // `this_range` looks like `this_range.lo..=overlap`; it overlaps with any // ranges that look like `overlap..=hi`. if !suffixes.is_empty() { @@ -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 { |