Track mutability of deref patterns

Author: Nadrieril

compiler/rustc_middle/src/thir.rs

@@ -645,7 +645,7 @@ impl<'tcx> Pat<'tcx> {
             AscribeUserType { subpattern, .. }
             | Binding { subpattern: Some(subpattern), .. }
             | Deref { subpattern }
-            | DerefPattern { subpattern }
+            | DerefPattern { subpattern, .. }
             | InlineConstant { subpattern, .. } => subpattern.walk_(it),
             Leaf { subpatterns } | Variant { subpatterns, .. } => {
                 subpatterns.iter().for_each(|field| field.pattern.walk_(it))
@@ -763,6 +763,7 @@ pub enum PatKind<'tcx> {
     /// Deref pattern, written `box P` for now.
     DerefPattern {
         subpattern: Box<Pat<'tcx>>,
+        mutability: hir::Mutability,
     },
 
     /// One of the following:
@@ -1167,7 +1168,7 @@ impl<'tcx> fmt::Display for Pat<'tcx> {
                 }
                 write!(f, "{subpattern}")
             }
-            PatKind::DerefPattern { ref subpattern } => {
+            PatKind::DerefPattern { ref subpattern, .. } => {
                 write!(f, "deref!({subpattern})")
             }
             PatKind::Constant { value } => write!(f, "{value}"),

compiler/rustc_middle/src/thir/visit.rs

@@ -229,7 +229,7 @@ pub fn walk_pat<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
     match &pat.kind {
         AscribeUserType { subpattern, ascription: _ }
         | Deref { subpattern }
-        | DerefPattern { subpattern }
+        | DerefPattern { subpattern, .. }
         | Binding { subpattern: Some(subpattern), .. } => visitor.visit_pat(subpattern),
         Binding { .. } | Wild | Never | Error(_) => {}
         Variant { subpatterns, adt_def: _, args: _, variant_index: _ } | Leaf { subpatterns } => {

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -943,7 +943,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 self.visit_primary_bindings(subpattern, pattern_user_ty.deref(), f);
             }
 
-            PatKind::DerefPattern { ref subpattern } => {
+            PatKind::DerefPattern { ref subpattern, .. } => {
                 self.visit_primary_bindings(subpattern, UserTypeProjections::none(), f);
             }
 

compiler/rustc_mir_build/src/build/matches/util.rs

@@ -250,7 +250,7 @@ impl<'pat, 'tcx> MatchPair<'pat, 'tcx> {
                 default_irrefutable()
             }
 
-            PatKind::DerefPattern { ref subpattern } => {
+            PatKind::DerefPattern { ref subpattern, .. } => {
                 // Create a new temporary for each deref pattern.
                 // FIXME(deref_patterns): dedup temporaries to avoid multiple `deref()` calls?
                 let temp = cx.temp(

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -257,7 +257,9 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
             }
 
             hir::PatKind::Deref(subpattern) => {
-                PatKind::DerefPattern { subpattern: self.lower_pattern(subpattern) }
+                let mutable = self.typeck_results.pat_has_ref_mut_binding(subpattern);
+                let mutability = if mutable { hir::Mutability::Mut } else { hir::Mutability::Not };
+                PatKind::DerefPattern { subpattern: self.lower_pattern(subpattern), mutability }
             }
             hir::PatKind::Ref(subpattern, _) | hir::PatKind::Box(subpattern) => {
                 PatKind::Deref { subpattern: self.lower_pattern(subpattern) }

compiler/rustc_mir_build/src/thir/print.rs

@@ -687,7 +687,7 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
                 self.print_pat(subpattern, depth_lvl + 2);
                 print_indented!(self, "}", depth_lvl + 1);
             }
-            PatKind::DerefPattern { subpattern } => {
+            PatKind::DerefPattern { subpattern, .. } => {
                 print_indented!(self, "DerefPattern { ", depth_lvl + 1);
                 print_indented!(self, "subpattern:", depth_lvl + 2);
                 self.print_pat(subpattern, depth_lvl + 2);