Put back, fix ()-output optimization

src/librustdoc/html/render/mod.rs

@@ -170,6 +170,7 @@ impl Serialize for IndexItemFunctionType {
                 _ => seq.serialize_element(&self.inputs)?,
             }
             match &self.output[..] {
+                [] => {}
                 [one] if one.generics.is_none() => seq.serialize_element(one)?,
                 _ => seq.serialize_element(&self.output)?,
             }

src/librustdoc/html/static/js/search.js

@@ -1910,7 +1910,7 @@ function initSearch(rawSearchIndex) {
                 output = buildItemSearchTypeAll(functionSearchType[OUTPUT_DATA], lowercasePaths);
             }
         } else {
-            output = null;
+            output = [];
         }
         return {
             inputs, output,