Handle all PatExprs in dead code analysis

Author: oli-obk

compiler/rustc_passes/src/dead.rs

@@ -13,7 +13,7 @@ use rustc_errors::MultiSpan;
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId};
 use rustc_hir::intravisit::{self, Visitor};
-use rustc_hir::{self as hir, Node, PatExpr, PatExprKind, PatKind, TyKind};
+use rustc_hir::{self as hir, Node, PatKind, TyKind};
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::middle::privacy::Level;
 use rustc_middle::query::Providers;
@@ -636,10 +636,6 @@ impl<'tcx> Visitor<'tcx> for MarkSymbolVisitor<'tcx> {
                 let res = self.typeck_results().qpath_res(path, pat.hir_id);
                 self.handle_field_pattern_match(pat, res, fields);
             }
-            PatKind::Expr(PatExpr { kind: PatExprKind::Path(ref qpath), hir_id, .. }) => {
-                let res = self.typeck_results().qpath_res(qpath, *hir_id);
-                self.handle_res(res);
-            }
             PatKind::TupleStruct(ref qpath, fields, dotdot) => {
                 let res = self.typeck_results().qpath_res(qpath, pat.hir_id);
                 self.handle_tuple_field_pattern_match(pat, res, fields, dotdot);
@@ -651,6 +647,17 @@ impl<'tcx> Visitor<'tcx> for MarkSymbolVisitor<'tcx> {
         self.in_pat = false;
     }
 
+    fn visit_pat_expr(&mut self, expr: &'tcx rustc_hir::PatExpr<'tcx>) {
+        match &expr.kind {
+            rustc_hir::PatExprKind::Path(qpath) => {
+                let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
+                self.handle_res(res);
+            }
+            _ => {}
+        }
+        intravisit::walk_pat_expr(self, expr);
+    }
+
     fn visit_path(&mut self, path: &hir::Path<'tcx>, _: hir::HirId) {
         self.handle_res(path.res);
         intravisit::walk_path(self, path);

tests/ui/pattern/issue-110508.rs

@@ -1,3 +1,5 @@
+//@ run-pass
+
 #![deny(dead_code)]
 
 #[derive(PartialEq, Eq)]
@@ -11,7 +13,7 @@ impl Foo {
     const A2: Foo = Self::FooA(());
     const A3: Self = Foo::FooA(());
     const A4: Self = Self::FooA(());
-    const A5: u32 = 1; //~ ERROR: dead_code
+    const A5: u32 = 1;
 }
 
 fn main() {