From e09d7c19f48a9c754c9918b8237477286cc8ed74 Mon Sep 17 00:00:00 2001
From: jyn <rust@jyn.dev>
Date: Sun, 26 Apr 2026 16:07:28 +0000
Subject: [PATCH] Explain why `-D warnings` doesn't affect linker-warnings

---
 compiler/rustc_middle/src/lint.rs               | 12 ++++++++++++
 tests/run-make/linker-warning/deny-warnings.txt |  1 +
 2 files changed, 13 insertions(+)

diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index 7ea059c5d29d..13cdc405a8df 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -305,6 +305,18 @@ fn explain_lint_level_source(
             }
         }
     }
+
+    if let Some(warnings_group) = sess
+        .opts
+        .lint_opts
+        .iter()
+        .find_map(|(opt, level)| (opt == "warnings").then_some(level))
+        .copied()
+        && warnings_group >= Level::Deny
+        && level < warnings_group
+    {
+        err.note_once(format!("the `{name}` lint ignores `-D warnings`"));
+    }
 }
 
 /// The innermost function for emitting lints implementing the [`trait@Diagnostic`] trait.
diff --git a/tests/run-make/linker-warning/deny-warnings.txt b/tests/run-make/linker-warning/deny-warnings.txt
index 53137252e119..7a187af46f70 100644
--- a/tests/run-make/linker-warning/deny-warnings.txt
+++ b/tests/run-make/linker-warning/deny-warnings.txt
@@ -1,6 +1,7 @@
 warning: linker stderr: bar
   |
   = note: requested on the command line with `-W linker-messages`
+  = note: the `linker_messages` lint ignores `-D warnings`
 
 warning: 1 warning emitted