Rollup merge of #110964 - notriddle:notriddle/deref-impl, r=GuillaumeGomez

rustdoc: fix weird margins between Deref impl items

## Before

![image](https://user-images.githubusercontent.com/1593513/235245977-90770591-22c1-4a27-9464-248a3729a2b7.png)

## After

![image](https://user-images.githubusercontent.com/1593513/235246009-0e83113e-42b7-4e29-981d-969f9d20af01.png)

## Description

In the old setup, if the dereffed-to item has multiple impl blocks, each one gets its own `div.impl-items` in the section, but there are no headers separating them. Since the last method in a `div.impl-items` has no bottom margin, and there are no margins between these divs, there is no margin between the last method of one impl and the first method of the following impl.

This patch fixes it by simplifying the HTML. Each Deref block gets exactly one `div.impl-items`, no matter how many impl blocks it actually has.

13 files changed, 55 insertions, 6 deletions

diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index a5f08fdac11..d90d0aecb93 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -1155,10 +1155,10 @@ fn render_assoc_items_inner(
     let (non_trait, traits): (Vec<_>, _) = v.iter().partition(|i| i.inner_impl().trait_.is_none());
     if !non_trait.is_empty() {
         let mut tmp_buf = Buffer::html();
-        let (render_mode, id) = match what {
+        let (render_mode, id, class_html) = match what {
             AssocItemRender::All => {
                 write_impl_section_heading(&mut tmp_buf, "Implementations", "implementations");
-                (RenderMode::Normal, "implementations-list".to_owned())
+                (RenderMode::Normal, "implementations-list".to_owned(), "")
             }
             AssocItemRender::DerefFor { trait_, type_, deref_mut_ } => {
                 let id =
@@ -1175,7 +1175,11 @@ fn render_assoc_items_inner(
                     ),
                     &id,
                 );
-                (RenderMode::ForDeref { mut_: deref_mut_ }, cx.derive_id(id))
+                (
+                    RenderMode::ForDeref { mut_: deref_mut_ },
+                    cx.derive_id(id),
+                    r#" class="impl-items""#,
+                )
             }
         };
         let mut impls_buf = Buffer::html();
@@ -1199,7 +1203,7 @@ fn render_assoc_items_inner(
         }
         if !impls_buf.is_empty() {
             write!(w, "{}", tmp_buf.into_inner()).unwrap();
-            write!(w, "<div id=\"{}\">", id).unwrap();
+            write!(w, "<div id=\"{id}\"{class_html}>").unwrap();
             write!(w, "{}", impls_buf.into_inner()).unwrap();
             w.write_str("</div>").unwrap();
         }
@@ -1788,12 +1792,14 @@ fn render_impl(
                 .into_string()
             );
         }
+        if !default_impl_items.is_empty() || !impl_items.is_empty() {
+            w.write_str("<div class=\"impl-items\">");
+            close_tags.insert_str(0, "</div>");
+        }
     }
     if !default_impl_items.is_empty() || !impl_items.is_empty() {
-        w.write_str("<div class=\"impl-items\">");
         w.push_buffer(default_impl_items);
         w.push_buffer(impl_items);
-        close_tags.insert_str(0, "</div>");
     }
     w.write_str(&close_tags);
 }
diff --git a/tests/rustdoc/deref-const-fn.rs b/tests/rustdoc/deref/deref-const-fn.rs
index 8ecca6d12d2..8ecca6d12d2 100644
--- a/tests/rustdoc/deref-const-fn.rs
+++ b/tests/rustdoc/deref/deref-const-fn.rs
diff --git a/tests/rustdoc/deref/deref-multiple-impl-blocks.rs b/tests/rustdoc/deref/deref-multiple-impl-blocks.rs
new file mode 100644
index 00000000000..fa3607c5fc1
--- /dev/null
+++ b/tests/rustdoc/deref/deref-multiple-impl-blocks.rs
@@ -0,0 +1,43 @@
+#![crate_name="foo"]
+
+use std::ops::{Deref, DerefMut};
+
+// @has foo/struct.Vec.html
+// @count - '//h2[@id="deref-methods-Slice"]' 1
+// @count - '//div[@id="deref-methods-Slice-1"]' 1
+// @count - '//div[@id="deref-methods-Slice-1"][@class="impl-items"]' 1
+// @count - '//div[@id="deref-methods-Slice-1"]/div[@class="impl-items"]' 0
+pub struct Vec;
+
+pub struct Slice;
+
+impl Deref for Vec {
+    type Target = Slice;
+    fn deref(&self) -> &Slice {
+        &Slice
+    }
+}
+
+impl DerefMut for Vec {
+    fn deref_mut(&mut self) -> &mut Slice {
+        &mut Slice
+    }
+}
+
+impl Slice {
+    pub fn sort_floats(&mut self) {
+        todo!();
+    }
+}
+
+impl Slice {
+    pub fn sort(&mut self) {
+        todo!();
+    }
+}
+
+impl Slice {
+    pub fn len(&self) {
+        todo!();
+    }
+}
diff --git a/tests/rustdoc/deref-mut-methods.rs b/tests/rustdoc/deref/deref-mut-methods.rs
index fdf8434224f..fdf8434224f 100644
--- a/tests/rustdoc/deref-mut-methods.rs
+++ b/tests/rustdoc/deref/deref-mut-methods.rs
diff --git a/tests/rustdoc/deref-recursive-pathbuf.rs b/tests/rustdoc/deref/deref-recursive-pathbuf.rs
index be2b42b5ac6..be2b42b5ac6 100644
--- a/tests/rustdoc/deref-recursive-pathbuf.rs
+++ b/tests/rustdoc/deref/deref-recursive-pathbuf.rs
diff --git a/tests/rustdoc/deref-recursive.rs b/tests/rustdoc/deref/deref-recursive.rs
index 0436f2f86f5..0436f2f86f5 100644
--- a/tests/rustdoc/deref-recursive.rs
+++ b/tests/rustdoc/deref/deref-recursive.rs
diff --git a/tests/rustdoc/deref-slice-core.rs b/tests/rustdoc/deref/deref-slice-core.rs
index cccf273a820..cccf273a820 100644
--- a/tests/rustdoc/deref-slice-core.rs
+++ b/tests/rustdoc/deref/deref-slice-core.rs
diff --git a/tests/rustdoc/deref-to-primitive.rs b/tests/rustdoc/deref/deref-to-primitive.rs
index 527de780d48..527de780d48 100644
--- a/tests/rustdoc/deref-to-primitive.rs
+++ b/tests/rustdoc/deref/deref-to-primitive.rs
diff --git a/tests/rustdoc/deref-typedef.rs b/tests/rustdoc/deref/deref-typedef.rs
index 32424d13eb8..32424d13eb8 100644
--- a/tests/rustdoc/deref-typedef.rs
+++ b/tests/rustdoc/deref/deref-typedef.rs
diff --git a/tests/rustdoc/escape-deref-methods.rs b/tests/rustdoc/deref/escape-deref-methods.rs
index 66919d73eeb..66919d73eeb 100644
--- a/tests/rustdoc/escape-deref-methods.rs
+++ b/tests/rustdoc/deref/escape-deref-methods.rs
diff --git a/tests/rustdoc/issue-100679-sidebar-links-deref.rs b/tests/rustdoc/deref/issue-100679-sidebar-links-deref.rs
index f09d2320609..f09d2320609 100644
--- a/tests/rustdoc/issue-100679-sidebar-links-deref.rs
+++ b/tests/rustdoc/deref/issue-100679-sidebar-links-deref.rs
diff --git a/tests/rustdoc/recursive-deref-sidebar.rs b/tests/rustdoc/deref/recursive-deref-sidebar.rs
index 619f40eff89..619f40eff89 100644
--- a/tests/rustdoc/recursive-deref-sidebar.rs
+++ b/tests/rustdoc/deref/recursive-deref-sidebar.rs
diff --git a/tests/rustdoc/recursive-deref.rs b/tests/rustdoc/deref/recursive-deref.rs
index aa38485c445..aa38485c445 100644
--- a/tests/rustdoc/recursive-deref.rs
+++ b/tests/rustdoc/deref/recursive-deref.rs