1 files changed, 17 insertions, 103 deletions

diff --git a/compiler/rustc_pattern_analysis/src/lints.rs b/compiler/rustc_pattern_analysis/src/lints.rs
index 4bfe7dfb072..3f1497540d2 100644
--- a/compiler/rustc_pattern_analysis/src/lints.rs
+++ b/compiler/rustc_pattern_analysis/src/lints.rs
@@ -1,109 +1,24 @@
 use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
 use rustc_span::ErrorGuaranteed;
 
+use crate::constructor::Constructor;
 use crate::errors::{NonExhaustiveOmittedPattern, NonExhaustiveOmittedPatternLintOnArm, Uncovered};
-use crate::pat::PatOrWild;
-use crate::rustc::{
-    Constructor, DeconstructedPat, MatchArm, MatchCtxt, PlaceCtxt, RevealedTy, RustcMatchCheckCtxt,
-    SplitConstructorSet, WitnessPat,
-};
-
-/// A column of patterns in the matrix, where a column is the intuitive notion of "subpatterns that
-/// inspect the same subvalue/place".
-/// This is used to traverse patterns column-by-column for lints. Despite similarities with the
-/// algorithm in [`crate::usefulness`], this does a different traversal. Notably this is linear in
-/// 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.
-///
-/// This must not contain an or-pattern. `expand_and_push` takes care to expand them.
-///
-/// This is not used in the usefulness algorithm; only in lints.
-#[derive(Debug)]
-pub(crate) struct PatternColumn<'p, 'tcx> {
-    patterns: Vec<&'p DeconstructedPat<'p, 'tcx>>,
-}
-
-impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
-    pub(crate) fn new(arms: &[MatchArm<'p, 'tcx>]) -> Self {
-        let patterns = Vec::with_capacity(arms.len());
-        let mut column = PatternColumn { patterns };
-        for arm in arms {
-            column.expand_and_push(PatOrWild::Pat(arm.pat));
-        }
-        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>>) {
-        // We flatten or-patterns and skip algorithm-generated wildcards.
-        if pat.is_or_pat() {
-            self.patterns.extend(
-                pat.flatten_or_pat().into_iter().filter_map(|pat_or_wild| pat_or_wild.as_pat()),
-            )
-        } else if let Some(pat) = pat.as_pat() {
-            self.patterns.push(pat)
-        }
-    }
-
-    fn head_ty(&self) -> Option<RevealedTy<'tcx>> {
-        self.patterns.first().map(|pat| *pat.ty())
-    }
-
-    /// Do constructor splitting on the constructors of the column.
-    fn analyze_ctors(
-        &self,
-        pcx: &PlaceCtxt<'_, 'p, 'tcx>,
-    ) -> Result<SplitConstructorSet<'p, 'tcx>, ErrorGuaranteed> {
-        let column_ctors = self.patterns.iter().map(|p| p.ctor());
-        let ctors_for_ty = &pcx.ctors_for_ty()?;
-        Ok(ctors_for_ty.split(column_ctors))
-    }
-
-    /// Does specialization: given a constructor, this takes the patterns from the column that match
-    /// the constructor, and outputs their fields.
-    /// This returns one column per field of the constructor. They usually all have the same length
-    /// (the number of patterns in `self` that matched `ctor`), except that we expand or-patterns
-    /// which may change the lengths.
-    fn specialize(
-        &self,
-        pcx: &PlaceCtxt<'_, 'p, 'tcx>,
-        ctor: &Constructor<'p, 'tcx>,
-    ) -> Vec<PatternColumn<'p, 'tcx>> {
-        let arity = ctor.arity(pcx);
-        if arity == 0 {
-            return Vec::new();
-        }
-
-        // We specialize the column by `ctor`. This gives us `arity`-many columns of patterns. These
-        // columns may have different lengths in the presence of or-patterns (this is why we can't
-        // reuse `Matrix`).
-        let mut specialized_columns: Vec<_> =
-            (0..arity).map(|_| Self { patterns: Vec::new() }).collect();
-        let relevant_patterns =
-            self.patterns.iter().filter(|pat| ctor.is_covered_by(pcx, pat.ctor()));
-        for pat in relevant_patterns {
-            let specialized = pat.specialize(ctor, arity);
-            for (subpat, column) in specialized.into_iter().zip(&mut specialized_columns) {
-                column.expand_and_push(subpat);
-            }
-        }
-        specialized_columns
-    }
-}
+use crate::pat_column::PatternColumn;
+use crate::rustc::{RevealedTy, RustcMatchCheckCtxt, WitnessPat};
+use crate::MatchArm;
 
 /// Traverse the patterns to collect any variants of a non_exhaustive enum that fail to be mentioned
 /// in a given column.
 #[instrument(level = "debug", skip(cx), ret)]
 fn collect_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
-    cx: MatchCtxt<'a, 'p, 'tcx>,
-    column: &PatternColumn<'p, 'tcx>,
+    cx: &RustcMatchCheckCtxt<'p, 'tcx>,
+    column: &PatternColumn<'p, RustcMatchCheckCtxt<'p, 'tcx>>,
 ) -> Result<Vec<WitnessPat<'p, 'tcx>>, ErrorGuaranteed> {
-    let Some(ty) = column.head_ty() else {
+    let Some(&ty) = column.head_ty() else {
         return Ok(Vec::new());
     };
-    let pcx = &PlaceCtxt::new_dummy(cx, &ty);
 
-    let set = column.analyze_ctors(pcx)?;
+    let set = column.analyze_ctors(cx, &ty)?;
     if set.present.is_empty() {
         // We can't consistently handle the case where no constructors are present (since this would
         // require digging deep through any type in case there's a non_exhaustive enum somewhere),
@@ -112,20 +27,20 @@ fn collect_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
     }
 
     let mut witnesses = Vec::new();
-    if cx.tycx.is_foreign_non_exhaustive_enum(ty) {
+    if cx.is_foreign_non_exhaustive_enum(ty) {
         witnesses.extend(
             set.missing
                 .into_iter()
                 // This will list missing visible variants.
                 .filter(|c| !matches!(c, Constructor::Hidden | Constructor::NonExhaustive))
-                .map(|missing_ctor| WitnessPat::wild_from_ctor(pcx, missing_ctor)),
+                .map(|missing_ctor| WitnessPat::wild_from_ctor(cx, missing_ctor, ty)),
         )
     }
 
     // Recurse into the fields.
     for ctor in set.present {
-        let specialized_columns = column.specialize(pcx, &ctor);
-        let wild_pat = WitnessPat::wild_from_ctor(pcx, ctor);
+        let specialized_columns = column.specialize(cx, &ty, &ctor);
+        let wild_pat = WitnessPat::wild_from_ctor(cx, ctor, ty);
         for (i, col_i) in specialized_columns.iter().enumerate() {
             // Compute witnesses for each column.
             let wits_for_col_i = collect_nonexhaustive_missing_variants(cx, col_i)?;
@@ -141,18 +56,17 @@ fn collect_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
     Ok(witnesses)
 }
 
-pub(crate) fn lint_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
-    cx: MatchCtxt<'a, 'p, 'tcx>,
-    arms: &[MatchArm<'p, 'tcx>],
-    pat_column: &PatternColumn<'p, 'tcx>,
+pub(crate) fn lint_nonexhaustive_missing_variants<'p, 'tcx>(
+    rcx: &RustcMatchCheckCtxt<'p, 'tcx>,
+    arms: &[MatchArm<'p, RustcMatchCheckCtxt<'p, 'tcx>>],
+    pat_column: &PatternColumn<'p, RustcMatchCheckCtxt<'p, 'tcx>>,
     scrut_ty: RevealedTy<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
-    let rcx: &RustcMatchCheckCtxt<'_, '_> = cx.tycx;
     if !matches!(
         rcx.tcx.lint_level_at_node(NON_EXHAUSTIVE_OMITTED_PATTERNS, rcx.match_lint_level).0,
         rustc_session::lint::Level::Allow
     ) {
-        let witnesses = collect_nonexhaustive_missing_variants(cx, pat_column)?;
+        let witnesses = collect_nonexhaustive_missing_variants(rcx, pat_column)?;
         if !witnesses.is_empty() {
             // Report that a match of a `non_exhaustive` enum marked with `non_exhaustive_omitted_patterns`
             // is not exhaustive enough.