Add missing anchor for union type fields

Author: GuillaumeGomez

src/librustdoc/html/render.rs

@@ -2801,10 +2801,15 @@ fn item_union(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
         write!(w, "<h2 id='fields' class='fields small-section-header'>
                    Fields<a href='#fields' class='anchor'></a></h2>")?;
         for (field, ty) in fields {
-            write!(w, "<span id='{shortty}.{name}' class=\"{shortty}\"><code>{name}: {ty}</code>
+            let name = field.name.as_ref().expect("union field name");
+            let id = format!("{}.{}", ItemType::StructField, name);
+            write!(w, "<span id=\"{id}\" class=\"{shortty} small-section-header\">\
+                           <a href=\"#{id}\" class=\"anchor field\"></a>\
+                           <span class='invisible'><code>{name}: {ty}</code></span>\
                        </span>",
+                   id = id,
+                   name = name,
                    shortty = ItemType::StructField,
-                   name = field.name.as_ref().unwrap(),
                    ty = ty)?;
             if let Some(stability_class) = field.stability_class() {
                 write!(w, "<span class='stab {stab}'></span>",