From f1ff461d118fb8de54ef2a6a9937c0e9e6ce25d8 Mon Sep 17 00:00:00 2001
From: Arthur Carcano <arthur.carcano@ocamlpro.com>
Date: Wed, 3 Jan 2024 17:39:16 +0100
Subject: [PATCH] Replace visibility test with reachability test in dead code
 detection

Fixes https://github.com/rust-lang/rust/issues/119545
---
 compiler/rustc_passes/src/dead.rs                |  3 ++-
 tests/ui/lint/dead-code/pub-field-in-priv-mod.rs | 11 +++++++++++
 .../lint/dead-code/pub-field-in-priv-mod.stderr  | 16 ++++++++++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/lint/dead-code/pub-field-in-priv-mod.rs
 create mode 100644 tests/ui/lint/dead-code/pub-field-in-priv-mod.stderr

diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs
index 22aac1e775e6f..c335b2741bee2 100644
--- a/compiler/rustc_passes/src/dead.rs
+++ b/compiler/rustc_passes/src/dead.rs
@@ -434,12 +434,13 @@ impl<'tcx> Visitor<'tcx> for MarkSymbolVisitor<'tcx> {
         let tcx = self.tcx;
         let has_repr_c = self.repr_has_repr_c;
         let has_repr_simd = self.repr_has_repr_simd;
+        let effective_visibilities = &tcx.effective_visibilities(());
         let live_fields = def.fields().iter().filter_map(|f| {
             let def_id = f.def_id;
             if has_repr_c || (f.is_positional() && has_repr_simd) {
                 return Some(def_id);
             }
-            if !tcx.visibility(f.hir_id.owner.def_id).is_public() {
+            if !effective_visibilities.is_reachable(f.hir_id.owner.def_id) {
                 return None;
             }
             if tcx.visibility(def_id).is_public() { Some(def_id) } else { None }
diff --git a/tests/ui/lint/dead-code/pub-field-in-priv-mod.rs b/tests/ui/lint/dead-code/pub-field-in-priv-mod.rs
new file mode 100644
index 0000000000000..e49a164e9401b
--- /dev/null
+++ b/tests/ui/lint/dead-code/pub-field-in-priv-mod.rs
@@ -0,0 +1,11 @@
+#![deny(dead_code)]
+
+fn main() {
+    let _ = foo::S{f: false};
+}
+
+mod foo {
+    pub struct S {
+        pub f: bool, //~ ERROR field `f` is never read
+    }
+}
diff --git a/tests/ui/lint/dead-code/pub-field-in-priv-mod.stderr b/tests/ui/lint/dead-code/pub-field-in-priv-mod.stderr
new file mode 100644
index 0000000000000..11dd387315fbc
--- /dev/null
+++ b/tests/ui/lint/dead-code/pub-field-in-priv-mod.stderr
@@ -0,0 +1,16 @@
+error: field `f` is never read
+  --> $DIR/pub-field-in-priv-mod.rs:9:13
+   |
+LL |     pub struct S {
+   |                - field in this struct
+LL |         pub f: bool,
+   |             ^
+   |
+note: the lint level is defined here
+  --> $DIR/pub-field-in-priv-mod.rs:1:9
+   |
+LL | #![deny(dead_code)]
+   |         ^^^^^^^^^
+
+error: aborting due to 1 previous error
+