Expand sub code blocks block content when hidden when the page hash refers to it

Author: GuillaumeGomez

src/librustdoc/html/static/main.js

@@ -306,6 +306,14 @@ function defocusSearchBar() {
     function expandSection(id) {
         var elem = document.getElementById(id);
         if (elem && isHidden(elem)) {
+            if (elem.tagName === "CODE" && elem.parentNode.tagName === "H4") {
+                // We are in a trait implementation, what we want is the parent.
+                elem = elem.parentNode;
+                if (elem.id !== null && elem.id.length > 0) {
+                    // Change the id to the parent which is "more clear" and better for users.
+                    window.location.hash = elem.id;
+                }
+            }
             var h3 = elem.parentNode.previousElementSibling;
             if (h3 && h3.tagName !== "H3") {
                 h3 = h3.previousElementSibling; // skip div.docblock