doc: Fold inline methods from Deref

Author: tesuji

src/librustdoc/html/render/mod.rs

@@ -1256,6 +1256,7 @@ fn render_assoc_items_inner(
     let Some(v) = cache.impls.get(&it) else { return };
     let (non_trait, traits): (Vec<_>, _) = v.iter().partition(|i| i.inner_impl().trait_.is_none());
     if !non_trait.is_empty() {
+        let mut close_tags = String::new();
         let mut tmp_buf = Buffer::html();
         let (render_mode, id, class_html) = match what {
             AssocItemRender::All => {
@@ -1266,6 +1267,8 @@ fn render_assoc_items_inner(
                 let id =
                     cx.derive_id(small_url_encode(format!("deref-methods-{:#}", type_.print(cx))));
                 let derived_id = cx.derive_id(&id);
+                tmp_buf.write_str("<details class=\"toggle implementors-toggle\" open><summary>");
+                close_tags.insert_str(0, "</details>");
                 write_impl_section_heading(
                     &mut tmp_buf,
                     &format!(
@@ -1275,6 +1278,7 @@ fn render_assoc_items_inner(
                     ),
                     &id,
                 );
+                tmp_buf.write_str("</summary>");
                 if let Some(def_id) = type_.def_id(cx.cache()) {
                     cx.deref_id_map.insert(def_id, id);
                 }
@@ -1308,6 +1312,7 @@ fn render_assoc_items_inner(
                 impls_buf.into_inner()
             )
             .unwrap();
+            w.write_str(&close_tags).unwrap();
         }
     }
 

tests/rustdoc/deref/deref-slice-core.rs

@@ -6,7 +6,7 @@
 use core::ops::Deref;
 
 //@ has 'deref_slice_core/struct.MyArray.html'
-//@ has '-' '//*[@id="deref-methods-%5BT%5D"]' 'Methods from Deref<Target = [T]>'
+//@ has '-' '//details/summary/h2[@id="deref-methods-%5BT%5D"]' 'Methods from Deref<Target = [T]>'
 //@ has '-' '//*[@class="impl-items"]//*[@id="method.len"]' 'pub fn len(&self)'
 
 pub struct MyArray<T> {