Store type of each column in the matrix

Author: Nadrieril

compiler/rustc_pattern_analysis/src/lints.rs

@@ -84,7 +84,7 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
         let relevant_patterns =
             self.patterns.iter().filter(|pat| ctor.is_covered_by(pcx, pat.ctor()));
         for pat in relevant_patterns {
-            let specialized = pat.specialize(pcx, ctor);
+            let specialized = pat.specialize(pcx, ctor, pcx.ctor_sub_tys(ctor));
             for (subpat, column) in specialized.iter().zip(&mut specialized_columns) {
                 if subpat.is_or_pat() {
                     column.patterns.extend(subpat.flatten_or_pat())

compiler/rustc_pattern_analysis/src/pat.rs

@@ -81,10 +81,11 @@ impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
         &self,
         pcx: &PlaceCtxt<'_, 'p, Cx>,
         other_ctor: &Constructor<Cx>,
+        ctor_sub_tys: &[Cx::Ty],
     ) -> SmallVec<[&'p DeconstructedPat<'p, Cx>; 2]> {
         let wildcard_sub_tys = || {
-            let tys = pcx.ctor_sub_tys(other_ctor);
-            tys.iter()
+            ctor_sub_tys
+                .iter()
                 .map(|ty| DeconstructedPat::wildcard(*ty))
                 .map(|pat| pcx.mcx.wildcard_arena.alloc(pat) as &_)
                 .collect()

compiler/rustc_pattern_analysis/src/usefulness.rs

@@ -847,11 +847,8 @@ impl<'p, Cx: TypeCx> PatStack<'p, Cx> {
         self.pats.len()
     }
 
-    fn head_opt(&self) -> Option<&'p DeconstructedPat<'p, Cx>> {
-        self.pats.first().copied()
-    }
     fn head(&self) -> &'p DeconstructedPat<'p, Cx> {
-        self.head_opt().unwrap()
+        self.pats[0]
     }
 
     fn iter(&self) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Captures<'_> {
@@ -874,11 +871,12 @@ impl<'p, Cx: TypeCx> PatStack<'p, Cx> {
         &self,
         pcx: &PlaceCtxt<'_, 'p, Cx>,
         ctor: &Constructor<Cx>,
+        ctor_sub_tys: &[Cx::Ty],
         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);
+        let mut new_pats = self.head().specialize(pcx, ctor, ctor_sub_tys);
         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.
@@ -950,11 +948,12 @@ impl<'p, Cx: TypeCx> MatrixRow<'p, Cx> {
         &self,
         pcx: &PlaceCtxt<'_, 'p, Cx>,
         ctor: &Constructor<Cx>,
+        ctor_sub_tys: &[Cx::Ty],
         ctor_is_relevant: bool,
         parent_row: usize,
     ) -> MatrixRow<'p, Cx> {
         MatrixRow {
-            pats: self.pats.pop_head_constructor(pcx, ctor, ctor_is_relevant),
+            pats: self.pats.pop_head_constructor(pcx, ctor, ctor_sub_tys, ctor_is_relevant),
             parent_row,
             is_under_guard: self.is_under_guard,
             useful: false,
@@ -984,9 +983,11 @@ struct Matrix<'p, Cx: TypeCx> {
     /// each column must have the same type. Each column corresponds to a place within the
     /// scrutinee.
     rows: Vec<MatrixRow<'p, Cx>>,
-    /// Stores an extra fictitious row full of wildcards. Mostly used to keep track of the type of
-    /// each column. This must obey the same invariants as the real rows.
+    /// Stores an extra fictitious row full of wildcards. Mostly used to keep track of the
+    /// relevancy. This must obey the same invariants as the real rows.
     wildcard_row: PatStack<'p, Cx>,
+    /// Track the type of each column/place.
+    place_ty: SmallVec<[Cx::Ty; 2]>,
     /// Track for each column/place whether it contains a known valid value.
     place_validity: SmallVec<[ValidityConstraint; 2]>,
 }
@@ -1017,6 +1018,7 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
         let mut matrix = Matrix {
             rows: Vec::with_capacity(arms.len()),
             wildcard_row,
+            place_ty: smallvec![scrut_ty],
             place_validity: smallvec![scrut_validity],
         };
         for (row_id, arm) in arms.iter().enumerate() {
@@ -1032,10 +1034,10 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
     }
 
     fn head_ty(&self) -> Option<Cx::Ty> {
-        self.wildcard_row.head_opt().map(|pat| pat.ty())
+        self.place_ty.first().copied()
     }
     fn column_count(&self) -> usize {
-        self.wildcard_row.len()
+        self.place_ty.len()
     }
 
     fn rows(
@@ -1063,17 +1065,23 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
         ctor: &Constructor<Cx>,
         ctor_is_relevant: bool,
     ) -> Matrix<'p, Cx> {
-        let wildcard_row = self.wildcard_row.pop_head_constructor(pcx, ctor, ctor_is_relevant);
+        let tys = pcx.ctor_sub_tys(ctor);
+        let new_place_ty = tys.iter().chain(self.place_ty[1..].iter()).copied().collect();
+        let wildcard_row = self.wildcard_row.pop_head_constructor(pcx, ctor, tys, ctor_is_relevant);
         let new_validity = self.place_validity[0].specialize(ctor);
         let new_place_validity = std::iter::repeat(new_validity)
             .take(ctor.arity(pcx))
             .chain(self.place_validity[1..].iter().copied())
             .collect();
-        let mut matrix =
-            Matrix { rows: Vec::new(), wildcard_row, place_validity: new_place_validity };
+        let mut matrix = Matrix {
+            rows: Vec::new(),
+            wildcard_row,
+            place_ty: new_place_ty,
+            place_validity: new_place_validity,
+        };
         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_is_relevant, i);
+                let new_row = row.pop_head_constructor(pcx, ctor, tys, ctor_is_relevant, i);
                 matrix.expand_and_push(new_row);
             }
         }