From b5acf9501adc6926cb4496a1e981266f4c98ff25 Mon Sep 17 00:00:00 2001
From: CoCo-Japan-pan <115922543+CoCo-Japan-pan@users.noreply.github.com>
Date: Tue, 2 Jun 2026 18:15:46 +0900
Subject: [PATCH 1/2] Render `impl` restriction

---
 src/librustdoc/html/render/print_item.rs | 25 +++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 49a8c077188dd..8385e691ed385 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -628,7 +628,11 @@ fn item_trait(cx: &Context<'_>, it: &clean::Item, t: &clean::Trait) -> impl fmt:
         let count_types = required_types.len() + provided_types.len();
         let count_consts = required_consts.len() + provided_consts.len();
         let count_methods = required_methods.len() + provided_methods.len();
-        let must_implement_one_of_functions = &tcx.trait_def(t.def_id).must_implement_one_of;
+        let &rustc_middle::ty::TraitDef {
+            must_implement_one_of: ref must_implement_one_of_functions,
+            impl_restriction,
+            ..
+        } = tcx.trait_def(t.def_id);
 
         // Output the trait definition
         wrap_item(w, |mut w| {
@@ -782,6 +786,25 @@ fn item_trait(cx: &Context<'_>, it: &clean::Item, t: &clean::Trait) -> impl fmt:
         // Trait documentation
         write!(w, "{}", document(cx, it, None, HeadingOffset::H2))?;
 
+        if let rustc_middle::ty::trait_def::ImplRestrictionKind::Restricted(def_id, _) =
+            impl_restriction
+        {
+            let v1;
+            let v2;
+            write!(
+                w,
+                "<div class=\"stab impl_restriction\">This trait cannot be implemented outside <code>{}</code>.</div>",
+                if cx.cache().document_private {
+                    v1 =
+                        rustc_middle::ty::print::with_resolve_crate_name!(tcx.def_path_str(def_id));
+                    v1.as_str()
+                } else {
+                    v2 = tcx.crate_name(def_id.krate);
+                    v2.as_str()
+                },
+            )?;
+        }
+
         fn trait_item(cx: &Context<'_>, m: &clean::Item, t: &clean::Item) -> impl fmt::Display {
             fmt::from_fn(|w| {
                 let name = m.name.unwrap();

From 5358c2fdbb2f8f1ecdb6bf4e375b692da680d161 Mon Sep 17 00:00:00 2001
From: CoCo-Japan-pan <115922543+CoCo-Japan-pan@users.noreply.github.com>
Date: Tue, 2 Jun 2026 19:10:08 +0900
Subject: [PATCH 2/2] Add tests for `impl` restriction rendering

---
 .../impl/impl-restriction-document-private.rs     | 15 +++++++++++++++
 tests/rustdoc-html/impl/impl-restriction.rs       | 14 ++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 tests/rustdoc-html/impl/impl-restriction-document-private.rs
 create mode 100644 tests/rustdoc-html/impl/impl-restriction.rs

diff --git a/tests/rustdoc-html/impl/impl-restriction-document-private.rs b/tests/rustdoc-html/impl/impl-restriction-document-private.rs
new file mode 100644
index 0000000000000..6ea55eff54cf6
--- /dev/null
+++ b/tests/rustdoc-html/impl/impl-restriction-document-private.rs
@@ -0,0 +1,15 @@
+//@ compile-flags: --document-private-items
+#![crate_name = "c"]
+#![feature(impl_restriction)]
+
+//@ matches c/trait.Foo.html '//*[@class="stab impl_restriction"]' \
+//      'This trait cannot be implemented outside c.$'
+//@ has c/trait.Foo.html '//*[@class="stab impl_restriction"]//code' 'c'
+pub impl(crate) trait Foo {}
+
+pub mod inner {
+    //@ matches c/inner/trait.Bar.html '//*[@class="stab impl_restriction"]' \
+    //      'This trait cannot be implemented outside c::inner.$'
+    //@ has c/inner/trait.Bar.html '//*[@class="stab impl_restriction"]//code' 'c::inner'
+    pub impl(self) trait Bar {}
+}
diff --git a/tests/rustdoc-html/impl/impl-restriction.rs b/tests/rustdoc-html/impl/impl-restriction.rs
new file mode 100644
index 0000000000000..11df67425f9b9
--- /dev/null
+++ b/tests/rustdoc-html/impl/impl-restriction.rs
@@ -0,0 +1,14 @@
+#![crate_name = "c"]
+#![feature(impl_restriction)]
+
+//@ matches c/trait.Foo.html '//*[@class="stab impl_restriction"]' \
+//      'This trait cannot be implemented outside c.$'
+//@ has c/trait.Foo.html '//*[@class="stab impl_restriction"]//code' 'c'
+pub impl(crate) trait Foo {}
+
+pub mod inner {
+    //@ matches c/inner/trait.Bar.html '//*[@class="stab impl_restriction"]' \
+    //      'This trait cannot be implemented outside c.$'
+    //@ has c/inner/trait.Bar.html '//*[@class="stab impl_restriction"]//code' 'c'
+    pub impl(self) trait Bar {}
+}