We only need the arity of the subtype list now

compiler/rustc_pattern_analysis/src/lints.rs

@@ -88,9 +88,8 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
             (0..arity).map(|_| Self { patterns: Vec::new() }).collect();
         let relevant_patterns =
             self.patterns.iter().filter(|pat| ctor.is_covered_by(pcx, pat.ctor()));
-        let ctor_sub_tys = pcx.ctor_sub_tys(ctor);
         for pat in relevant_patterns {
-            let specialized = pat.specialize(pcx, ctor, ctor_sub_tys);
+            let specialized = pat.specialize(ctor, arity);
             for (subpat, column) in specialized.into_iter().zip(&mut specialized_columns) {
                 column.expand_and_push(subpat);
             }

compiler/rustc_pattern_analysis/src/pat.rs

@@ -72,11 +72,10 @@ impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
     /// `other_ctor` can be different from `self.ctor`, but must be covered by it.
     pub(crate) fn specialize(
         &self,
-        _pcx: &PlaceCtxt<'_, 'p, Cx>,
         other_ctor: &Constructor<Cx>,
-        ctor_sub_tys: &[Cx::Ty],
+        ctor_arity: usize,
     ) -> SmallVec<[PatOrWild<'p, Cx>; 2]> {
-        let wildcard_sub_tys = || ctor_sub_tys.iter().map(|_| Wild).collect();
+        let wildcard_sub_tys = || (0..ctor_arity).map(|_| Wild).collect();
         match (&self.ctor, other_ctor) {
             // Return a wildcard for each field of `other_ctor`.
             (Wildcard, _) => wildcard_sub_tys(),
@@ -192,13 +191,12 @@ impl<'p, Cx: TypeCx> PatOrWild<'p, Cx> {
     /// `other_ctor` can be different from `self.ctor`, but must be covered by it.
     pub(crate) fn specialize(
         &self,
-        pcx: &PlaceCtxt<'_, 'p, Cx>,
         other_ctor: &Constructor<Cx>,
-        ctor_sub_tys: &[Cx::Ty],
+        ctor_arity: usize,
     ) -> SmallVec<[PatOrWild<'p, Cx>; 2]> {
         match self {
-            Wild => ctor_sub_tys.iter().map(|_| Wild).collect(),
-            Pat(pat) => pat.specialize(pcx, other_ctor, ctor_sub_tys),
+            Wild => (0..ctor_arity).map(|_| Wild).collect(),
+            Pat(pat) => pat.specialize(other_ctor, ctor_arity),
         }
     }
 

compiler/rustc_pattern_analysis/src/usefulness.rs

@@ -869,14 +869,13 @@ impl<'p, Cx: TypeCx> PatStack<'p, Cx> {
     /// Only call if `ctor.is_covered_by(self.head().ctor())` is true.
     fn pop_head_constructor(
         &self,
-        pcx: &PlaceCtxt<'_, 'p, Cx>,
         ctor: &Constructor<Cx>,
-        ctor_sub_tys: &[Cx::Ty],
+        ctor_arity: usize,
         ctor_is_relevant: bool,
     ) -> PatStack<'p, Cx> {
         // We pop the head pattern and push the new fields extracted from the arguments of
         // `self.head()`.
-        let mut new_pats = self.head().specialize(pcx, ctor, ctor_sub_tys);
+        let mut new_pats = self.head().specialize(ctor, ctor_arity);
         new_pats.extend_from_slice(&self.pats[1..]);
         // `ctor` is relevant for this row if it is the actual constructor of this row, or if the
         // row has a wildcard and `ctor` is relevant for wildcards.
@@ -946,14 +945,13 @@ impl<'p, Cx: TypeCx> MatrixRow<'p, Cx> {
     /// Only call if `ctor.is_covered_by(self.head().ctor())` is true.
     fn pop_head_constructor(
         &self,
-        pcx: &PlaceCtxt<'_, 'p, Cx>,
         ctor: &Constructor<Cx>,
-        ctor_sub_tys: &[Cx::Ty],
+        ctor_arity: usize,
         ctor_is_relevant: bool,
         parent_row: usize,
     ) -> MatrixRow<'p, Cx> {
         MatrixRow {
-            pats: self.pats.pop_head_constructor(pcx, ctor, ctor_sub_tys, ctor_is_relevant),
+            pats: self.pats.pop_head_constructor(ctor, ctor_arity, ctor_is_relevant),
             parent_row,
             is_under_guard: self.is_under_guard,
             useful: false,
@@ -1063,11 +1061,12 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
         ctor_is_relevant: bool,
     ) -> Matrix<'p, Cx> {
         let ctor_sub_tys = pcx.ctor_sub_tys(ctor);
+        let arity = ctor_sub_tys.len();
         let specialized_place_ty =
             ctor_sub_tys.iter().chain(self.place_ty[1..].iter()).copied().collect();
         let ctor_sub_validity = self.place_validity[0].specialize(ctor);
         let specialized_place_validity = std::iter::repeat(ctor_sub_validity)
-            .take(ctor.arity(pcx))
+            .take(arity)
             .chain(self.place_validity[1..].iter().copied())
             .collect();
         let mut matrix = Matrix {
@@ -1078,8 +1077,7 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
         };
         for (i, row) in self.rows().enumerate() {
             if ctor.is_covered_by(pcx, row.head().ctor()) {
-                let new_row =
-                    row.pop_head_constructor(pcx, ctor, ctor_sub_tys, ctor_is_relevant, i);
+                let new_row = row.pop_head_constructor(ctor, arity, ctor_is_relevant, i);
                 matrix.expand_and_push(new_row);
             }
         }