From a9f0f6df94c4d08fe300b6e06941aea9c7324530 Mon Sep 17 00:00:00 2001
From: QuietMisdreavus <grey@quietmisdreavus.net>
Date: Tue, 15 Aug 2017 16:05:03 -0500
Subject: [PATCH] add "Implementations on Foreign Types" to the sidebar

---
 src/librustdoc/html/render.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 1836476f23b..46bb119cf9c 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -3535,6 +3535,17 @@ fn sidebar_trait(fmt: &mut fmt::Formatter, it: &clean::Item,
 
     sidebar.push_str(&sidebar_assoc_items(it));
 
+    let c = cache();
+
+    if let Some(implementors) = c.implementors.get(&it.def_id) {
+        if implementors.iter().any(|i| i.impl_.for_.def_id()
+                                   .map_or(false, |d| !c.paths.contains_key(&d)))
+        {
+            sidebar.push_str("<li><a href=\"#foreign-impls\">\
+                             Implementations on Foreign Types</a></li>");
+        }
+    }
+
     sidebar.push_str("<li><a href=\"#implementors\">Implementors</a></li>");
 
     write!(fmt, "<div class=\"block items\"><ul>{}</ul></div>", sidebar)