make item_trait_alias return impl fmt::Display

Author: yotamofek

src/librustdoc/html/render/print_item.rs

@@ -266,7 +266,9 @@ pub(super) fn print_item(cx: &Context<'_>, item: &clean::Item, buf: &mut String)
         ),
         clean::ForeignTypeItem => write_str(buf, format_args!("{}", item_foreign_type(cx, item))),
         clean::KeywordItem => write_str(buf, format_args!("{}", item_keyword(cx, item))),
-        clean::TraitAliasItem(ref ta) => item_trait_alias(buf, cx, item, ta),
+        clean::TraitAliasItem(ref ta) => {
+            write_str(buf, format_args!("{}", item_trait_alias(cx, item, ta)))
+        }
         _ => {
             // We don't generate pages for any other type.
             unreachable!();
@@ -1244,32 +1246,35 @@ fn item_trait<'a, 'tcx>(
     })
 }
 
-fn item_trait_alias(
-    w: &mut impl fmt::Write,
-    cx: &Context<'_>,
-    it: &clean::Item,
-    t: &clean::TraitAlias,
-) {
-    wrap_item(w, |w| {
+fn item_trait_alias<'a, 'tcx>(
+    cx: &'a Context<'tcx>,
+    it: &'a clean::Item,
+    t: &'a clean::TraitAlias,
+) -> impl fmt::Display + 'a + Captures<'tcx> {
+    fmt::from_fn(|w| {
+        wrap_item(w, |w| {
+            write!(
+                w,
+                "{attrs}trait {name}{generics}{where_b} = {bounds};",
+                attrs = render_attributes_in_pre(it, "", cx),
+                name = it.name.unwrap(),
+                generics = t.generics.print(cx),
+                where_b = print_where_clause(&t.generics, cx, 0, Ending::Newline).maybe_display(),
+                bounds = bounds(&t.bounds, true, cx),
+            )
+        })?;
+
+        write!(w, "{}", document(cx, it, None, HeadingOffset::H2))?;
+        // Render any items associated directly to this alias, as otherwise they
+        // won't be visible anywhere in the docs. It would be nice to also show
+        // associated items from the aliased type (see discussion in #32077), but
+        // we need #14072 to make sense of the generics.
         write!(
             w,
-            "{attrs}trait {name}{generics}{where_b} = {bounds};",
-            attrs = render_attributes_in_pre(it, "", cx),
-            name = it.name.unwrap(),
-            generics = t.generics.print(cx),
-            where_b = print_where_clause(&t.generics, cx, 0, Ending::Newline).maybe_display(),
-            bounds = bounds(&t.bounds, true, cx),
+            "{}",
+            render_assoc_items(cx, it, it.item_id.expect_def_id(), AssocItemRender::All)
         )
-        .unwrap();
-    });
-
-    write!(w, "{}", document(cx, it, None, HeadingOffset::H2)).unwrap();
-    // Render any items associated directly to this alias, as otherwise they
-    // won't be visible anywhere in the docs. It would be nice to also show
-    // associated items from the aliased type (see discussion in #32077), but
-    // we need #14072 to make sense of the generics.
-    write!(w, "{}", render_assoc_items(cx, it, it.item_id.expect_def_id(), AssocItemRender::All))
-        .unwrap();
+    })
 }
 
 fn item_type_alias<'a, 'tcx>(