Mark the "#[default]" variant for enums

Author: omid

src/librustdoc/html/render/print_item.rs

@@ -1618,6 +1618,9 @@ fn item_variants(
         if let clean::VariantKind::Tuple(ref s) = variant_data.kind {
             write!(w, "({})", print_tuple_struct_fields(cx, s));
         }
+        if variant.attrs.other_attrs.iter().any(|a| a.has_name(kw::Default)) {
+            w.write_str(" <span class=\"stab default\">Default</span>");
+        }
         w.write_str("</h3></section>");
 
         let heading_and_fields = match &variant_data.kind {

tests/rustdoc/attributes.rs

@@ -11,3 +11,11 @@ pub extern "C" fn g() {}
 // @has foo/struct.Repr.html '//pre[@class="rust item-decl"]' '#[repr(C, align(8))]'
 #[repr(C, align(8))]
 pub struct Repr;
+
+// @has foo/enum.Enum.html '//section[@id="variant.Foo"]' 'Default'
+#[derive(Default)]
+pub enum Enum {
+    #[default]
+    Foo,
+    Bar,
+}