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Document the new expand_and_push method

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Nadrieril 2024-01-09 16:31:04 +01:00
parent 5c65e9fdaf
commit 4a1889e3fd
1 changed files with 5 additions and 3 deletions
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8
compiler/rustc_pattern_analysis/src/lints.rs
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@ -24,9 +24,9 @@
/// the depth of patterns, whereas `compute_exhaustiveness_and_usefulness` is worst-case exponential /// the depth of patterns, whereas `compute_exhaustiveness_and_usefulness` is worst-case exponential
/// (exhaustiveness is NP-complete). The core difference is that we treat sub-columns separately. /// (exhaustiveness is NP-complete). The core difference is that we treat sub-columns separately.
/// ///
/// This must not contain an or-pattern. `specialize` takes care to expand them. /// This must not contain an or-pattern. `expand_and_push` takes care to expand them.
/// ///
/// This is not used in the main algorithm; only in lints. /// This is not used in the usefulness algorithm; only in lints.
#[derive(Debug)] #[derive(Debug)]
pub(crate) struct PatternColumn<'p, 'tcx> { pub(crate) struct PatternColumn<'p, 'tcx> {
patterns: Vec<&'p DeconstructedPat<'p, 'tcx>>, patterns: Vec<&'p DeconstructedPat<'p, 'tcx>>,
@ -41,8 +41,10 @@ pub(crate) fn new(arms: &[MatchArm<'p, 'tcx>]) -> Self {
} }
column column
} }
/// Pushes a pattern onto the column, expanding any or-patterns into its subpatterns.
/// Internal method, prefer [`PatternColumn::new`].
fn expand_and_push(&mut self, pat: PatOrWild<'p, RustcMatchCheckCtxt<'p, 'tcx>>) { fn expand_and_push(&mut self, pat: PatOrWild<'p, RustcMatchCheckCtxt<'p, 'tcx>>) {
// We flatten or-patterns and skip wildcards // We flatten or-patterns and skip algorithm-generated wildcards.
if pat.is_or_pat() { if pat.is_or_pat() {
self.patterns.extend( self.patterns.extend(
pat.flatten_or_pat().into_iter().filter_map(|pat_or_wild| pat_or_wild.as_pat()), pat.flatten_or_pat().into_iter().filter_map(|pat_or_wild| pat_or_wild.as_pat()),