Rollup merge of #85280 - jsha:move-trait-toggles, r=GuillaumeGomez

Toggle-wrap items differently than top-doc.

This makes sure things like trait methods get wrapped at the
`<h3><code>` level rather than at the `.docblock` level. Also it ensures
that only the actual top documentation gets the `.top-doc` class.

Fixes #85167

Before:

![image](https://user-images.githubusercontent.com/220205/117743384-98790200-b1bb-11eb-8804-588530842514.png)

https://doc.rust-lang.org/nightly/std/io/trait.Read.html#tymethod.read

After:

![image](https://user-images.githubusercontent.com/220205/118410882-98a75080-b646-11eb-949d-ca688bab6923.png)

1 files changed, 5 insertions, 1 deletions

diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index b807c5ccc47..a288b43722a 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -509,7 +509,11 @@ fn document(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, parent: Option
         info!("Documenting {}", name);
     }
     document_item_info(w, cx, item, parent);
-    document_full_collapsible(w, item, cx);
+    if parent.is_none() {
+        document_full_collapsible(w, item, cx);
+    } else {
+        document_full(w, item, cx);
+    }
 }
 
 /// Render md_text as markdown.