make item_foreign_type return impl fmt::Display

Author: yotamofek

src/librustdoc/html/render/print_item.rs

@@ -264,7 +264,7 @@ pub(super) fn print_item(cx: &Context<'_>, item: &clean::Item, buf: &mut String)
             buf,
             format_args!("{}", item_constant(cx, item, &ci.generics, &ci.type_, &ci.kind)),
         ),
-        clean::ForeignTypeItem => item_foreign_type(buf, cx, item),
+        clean::ForeignTypeItem => write_str(buf, format_args!("{}", item_foreign_type(cx, item))),
         clean::KeywordItem => item_keyword(buf, cx, item),
         clean::TraitAliasItem(ref ta) => item_trait_alias(buf, cx, item, ta),
         _ => {
@@ -2122,22 +2122,24 @@ fn item_static<'a, 'tcx>(
     })
 }
 
-fn item_foreign_type(w: &mut impl fmt::Write, cx: &Context<'_>, it: &clean::Item) {
-    wrap_item(w, |buffer| {
-        buffer.write_str("extern {\n").unwrap();
-        render_attributes_in_code(buffer, it, cx);
+fn item_foreign_type<'a, 'tcx>(
+    cx: &'a Context<'tcx>,
+    it: &'a clean::Item,
+) -> impl fmt::Display + 'a + Captures<'tcx> {
+    fmt::from_fn(|w| {
+        wrap_item(w, |w| {
+            w.write_str("extern {\n")?;
+            render_attributes_in_code(w, it, cx);
+            write!(w, "    {}type {};\n}}", visibility_print_with_space(it, cx), it.name.unwrap(),)
+        })?;
+
         write!(
-            buffer,
-            "    {}type {};\n}}",
-            visibility_print_with_space(it, cx),
-            it.name.unwrap(),
+            w,
+            "{}{}",
+            document(cx, it, None, HeadingOffset::H2),
+            render_assoc_items(cx, it, it.item_id.expect_def_id(), AssocItemRender::All)
         )
-        .unwrap();
-    });
-
-    write!(w, "{}", document(cx, it, None, HeadingOffset::H2)).unwrap();
-    write!(w, "{}", render_assoc_items(cx, it, it.item_id.expect_def_id(), AssocItemRender::All))
-        .unwrap();
+    })
 }
 
 fn item_keyword(w: &mut String, cx: &Context<'_>, it: &clean::Item) {