From 6f513ead9c170505cf118bb50ee4acb479ddab0f Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume.gomez@huawei.com>
Date: Tue, 5 Oct 2021 12:41:12 +0200
Subject: [PATCH 1/2] Add object safety information on traits

---
 src/librustdoc/html/render/print_item.rs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 28b2eded7cc3e..5a9bc5fe2e2b3 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -497,6 +497,13 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
 
     // Output the trait definition
     wrap_into_docblock(w, |w| {
+        if let Some(def_id) = it.def_id.as_def_id() {
+            write!(
+                w,
+                "<div class=\"obj-info\">This trait is <b>{}object safe</b>.</div>",
+                if cx.tcx().is_object_safe(def_id) { "" } else { "not " }
+            );
+        }
         wrap_item(w, "trait", |w| {
             render_attributes_in_pre(w, it, "");
             write!(

From 112dff001ab6dc33a6a4728e9304eb0a3b5e141b Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume.gomez@huawei.com>
Date: Tue, 5 Oct 2021 12:41:25 +0200
Subject: [PATCH 2/2] Add test for trait object safety

---
 src/test/rustdoc/trait-object-safe.rs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 src/test/rustdoc/trait-object-safe.rs

diff --git a/src/test/rustdoc/trait-object-safe.rs b/src/test/rustdoc/trait-object-safe.rs
new file mode 100644
index 0000000000000..3485ff1056270
--- /dev/null
+++ b/src/test/rustdoc/trait-object-safe.rs
@@ -0,0 +1,23 @@
+#![crate_name = "foo"]
+
+// @has 'foo/trait.Safe.html'
+// @has - '//*[@class="obj-info"]' 'This trait is object safe.'
+pub trait Safe {
+    fn foo(&self);
+}
+
+// @has 'foo/trait.Unsafe.html'
+// @has - '//*[@class="obj-info"]' 'This trait is not object safe.'
+pub trait Unsafe {
+    fn foo() -> Self;
+}
+
+// @has 'foo/trait.Unsafe2.html'
+// @has - '//*[@class="obj-info"]' 'This trait is not object safe.'
+pub trait Unsafe2<T> {
+    fn foo(i: T);
+}
+
+// @has 'foo/struct.Foo.html'
+// @!has - '//*[@class="obj-info"]'
+pub struct Foo;