make render_stability_since_raw_with_extra return Option<impl fmt::Display>

Author: yotamofek

src/librustdoc/html/render/mod.rs

@@ -1019,7 +1019,7 @@ fn assoc_method<'a, 'tcx>(
 /// example, if the item became stable at 1.0.0, and const-stable at 1.45.0, this function would
 /// write a span containing "1.0.0 (const: 1.45.0)".
 ///
-/// Returns `true` if a stability annotation was rendered.
+/// Returns `None` if there is no stability annotation to be rendered.
 ///
 /// Stability and const-stability are considered separately. If the item is unstable, no version
 /// will be written. If the item is const-unstable, "const: unstable" will be appended to the
@@ -1030,11 +1030,10 @@ fn assoc_method<'a, 'tcx>(
 /// will include the const-stable version, but no stable version will be emitted, as a natural
 /// consequence of the above rules.
 fn render_stability_since_raw_with_extra(
-    w: &mut String,
     stable_version: Option<StableSince>,
     const_stability: Option<ConstStability>,
     extra_class: &str,
-) -> bool {
+) -> Option<impl fmt::Display + '_> {
     let mut title = String::new();
     let mut stability = String::new();
 
@@ -1084,14 +1083,9 @@ fn render_stability_since_raw_with_extra(
         }
     }
 
-    if !stability.is_empty() {
-        write_str(
-            w,
-            format_args!(r#"<span class="since{extra_class}" title="{title}">{stability}</span>"#),
-        );
-    }
-
-    !stability.is_empty()
+    (!stability.is_empty()).then_some(fmt::from_fn(move |w| {
+        write!(w, r#"<span class="since{extra_class}" title="{title}">{stability}</span>"#)
+    }))
 }
 
 fn since_to_string(since: &StableSince) -> Option<String> {
@@ -1104,11 +1098,10 @@ fn since_to_string(since: &StableSince) -> Option<String> {
 
 #[inline]
 fn render_stability_since_raw(
-    w: &mut String,
     ver: Option<StableSince>,
     const_stability: Option<ConstStability>,
-) -> bool {
-    render_stability_since_raw_with_extra(w, ver, const_stability, "")
+) -> Option<impl fmt::Display> {
+    render_stability_since_raw_with_extra(ver, const_stability, "")
 }
 
 fn render_assoc_item<'a, 'tcx>(
@@ -2114,30 +2107,27 @@ fn render_rightside(w: &mut String, cx: &Context<'_>, item: &clean::Item, render
     let src_href = cx.src_href(item);
     let has_src_ref = src_href.is_some();
 
-    let mut rightside = String::new();
-    let has_stability = render_stability_since_raw_with_extra(
-        &mut rightside,
+    let stability = render_stability_since_raw_with_extra(
         item.stable_since(tcx),
         const_stability,
         if has_src_ref { "" } else { " rightside" },
     );
-    if let Some(link) = src_href {
-        if has_stability {
-            write_str(
-                &mut rightside,
-                format_args!(" · <a class=\"src\" href=\"{link}\">Source</a>"),
-            );
-        } else {
+    match (stability, src_href) {
+        (Some(stability), Some(link)) => {
             write_str(
-                &mut rightside,
-                format_args!("<a class=\"src rightside\" href=\"{link}\">Source</a>"),
+                w,
+                format_args!(
+                    "<span class=\"rightside\">{stability} · <a class=\"src\" href=\"{link}\">Source</a></span>"
+                ),
             );
         }
-    }
-    if has_stability && has_src_ref {
-        write_str(w, format_args!("<span class=\"rightside\">{rightside}</span>"));
-    } else {
-        w.push_str(&rightside);
+        (Some(stability), None) => {
+            write_str(w, format_args!("{stability}"));
+        }
+        (None, Some(link)) => {
+            write_str(w, format_args!("<a class=\"src rightside\" href=\"{link}\">Source</a>"));
+        }
+        (None, None) => {}
     }
 }
 

src/librustdoc/html/render/print_item.rs

@@ -206,15 +206,10 @@ pub(super) fn print_item(cx: &Context<'_>, item: &clean::Item, buf: &mut String)
             unreachable!();
         }
     };
-    let stability_since_raw = {
-        let mut buf = String::new();
-        render_stability_since_raw(
-            &mut buf,
-            item.stable_since(cx.tcx()),
-            item.const_stability(cx.tcx()),
-        );
-        buf
-    };
+    let stability_since_raw =
+        render_stability_since_raw(item.stable_since(cx.tcx()), item.const_stability(cx.tcx()))
+            .maybe_display()
+            .to_string();
 
     // Write source tag
     //
@@ -1693,16 +1688,17 @@ fn item_variants(
             w,
             format_args!(
                 "<section id=\"{id}\" class=\"variant\">\
-                <a href=\"#{id}\" class=\"anchor\">§</a>"
+                    <a href=\"#{id}\" class=\"anchor\">§</a>\
+                    {}\
+                    <h3 class=\"code-header\">",
+                render_stability_since_raw_with_extra(
+                    variant.stable_since(tcx),
+                    variant.const_stability(tcx),
+                    " rightside",
+                )
+                .maybe_display()
             ),
         );
-        render_stability_since_raw_with_extra(
-            w,
-            variant.stable_since(tcx),
-            variant.const_stability(tcx),
-            " rightside",
-        );
-        w.push_str("<h3 class=\"code-header\">");
         if let clean::VariantItem(ref var) = variant.kind
             && let clean::VariantKind::CLike = var.kind
         {