make item_fields return impl fmt::Display

Author: yotamofek

src/librustdoc/html/render/print_item.rs

@@ -1334,7 +1334,7 @@ fn item_type_alias(w: &mut String, cx: &Context<'_>, it: &clean::Item, t: &clean
                         ),
                     );
                 });
-                item_fields(w, cx, it, fields, None);
+                write_str(w, format_args!("{}", item_fields(cx, it, fields, None)));
             }
             clean::TypeAliasInnerType::Struct { ctor_kind, fields } => {
                 wrap_item(w, |w| {
@@ -1359,7 +1359,7 @@ fn item_type_alias(w: &mut String, cx: &Context<'_>, it: &clean::Item, t: &clean
                         ),
                     );
                 });
-                item_fields(w, cx, it, fields, None);
+                write_str(w, format_args!("{}", item_fields(cx, it, fields, None)));
             }
         }
     }
@@ -1993,67 +1993,73 @@ fn item_struct(w: &mut String, cx: &Context<'_>, it: &clean::Item, s: &clean::St
         );
     });
 
-    write_str(w, format_args!("{}", document(cx, it, None, HeadingOffset::H2)));
-
-    item_fields(w, cx, it, &s.fields, s.ctor_kind);
-
     let def_id = it.item_id.expect_def_id();
-    write_str(w, format_args!("{}", render_assoc_items(cx, it, def_id, AssocItemRender::All)));
-    write_str(w, format_args!("{}", document_type_layout(cx, def_id)));
+
+    write_str(
+        w,
+        format_args!(
+            "{}{}{}{}",
+            document(cx, it, None, HeadingOffset::H2),
+            item_fields(cx, it, &s.fields, s.ctor_kind),
+            render_assoc_items(cx, it, def_id, AssocItemRender::All),
+            document_type_layout(cx, def_id),
+        ),
+    );
 }
 
-fn item_fields(
-    w: &mut String,
-    cx: &Context<'_>,
-    it: &clean::Item,
-    fields: &[clean::Item],
+fn item_fields<'a, 'tcx>(
+    cx: &'a Context<'tcx>,
+    it: &'a clean::Item,
+    fields: &'a [clean::Item],
     ctor_kind: Option<CtorKind>,
-) {
-    let mut fields = fields
-        .iter()
-        .filter_map(|f| match f.kind {
-            clean::StructFieldItem(ref ty) => Some((f, ty)),
-            _ => None,
-        })
-        .peekable();
-    if let None | Some(CtorKind::Fn) = ctor_kind {
-        if fields.peek().is_some() {
-            let title = format!(
-                "{}{}",
-                if ctor_kind.is_none() { "Fields" } else { "Tuple Fields" },
-                document_non_exhaustive_header(it),
-            );
-            write_str(
-                w,
-                format_args!(
+) -> impl fmt::Display + 'a + Captures<'tcx> {
+    fmt::from_fn(move |w| {
+        let mut fields = fields
+            .iter()
+            .filter_map(|f| match f.kind {
+                clean::StructFieldItem(ref ty) => Some((f, ty)),
+                _ => None,
+            })
+            .peekable();
+        if let None | Some(CtorKind::Fn) = ctor_kind {
+            if fields.peek().is_some() {
+                let title = format!(
+                    "{}{}",
+                    if ctor_kind.is_none() { "Fields" } else { "Tuple Fields" },
+                    document_non_exhaustive_header(it),
+                );
+                write!(
+                    w,
                     "{}",
                     write_section_heading(
                         &title,
                         "fields",
                         Some("fields"),
                         document_non_exhaustive(it)
                     )
-                ),
-            );
-            for (index, (field, ty)) in fields.enumerate() {
-                let field_name =
-                    field.name.map_or_else(|| index.to_string(), |sym| sym.as_str().to_string());
-                let id = cx.derive_id(format!("{typ}.{field_name}", typ = ItemType::StructField));
-                write_str(
-                    w,
-                    format_args!(
+                )?;
+                for (index, (field, ty)) in fields.enumerate() {
+                    let field_name = field
+                        .name
+                        .map_or_else(|| index.to_string(), |sym| sym.as_str().to_string());
+                    let id =
+                        cx.derive_id(format!("{typ}.{field_name}", typ = ItemType::StructField));
+                    write!(
+                        w,
                         "<span id=\"{id}\" class=\"{item_type} section-header\">\
                             <a href=\"#{id}\" class=\"anchor field\">§</a>\
                             <code>{field_name}: {ty}</code>\
-                        </span>",
+                        </span>\
+                        {doc}",
                         item_type = ItemType::StructField,
-                        ty = ty.print(cx)
-                    ),
-                );
-                write_str(w, format_args!("{}", document(cx, field, Some(it), HeadingOffset::H3)));
+                        ty = ty.print(cx),
+                        doc = document(cx, field, Some(it), HeadingOffset::H3),
+                    )?;
+                }
             }
         }
-    }
+        Ok(())
+    })
 }
 
 fn item_static(