rustdoc-search: add unbox flag to Result aliases

Fixes #139665

tests/rustdoc-js/generics-unbox.js

@@ -31,4 +31,10 @@ const EXPECTED = [
             { 'path': 'generics_unbox', 'name': 'beta' },
         ],
     },
+    {
+        'query': '-> Sigma',
+        'others': [
+            { 'path': 'generics_unbox', 'name': 'delta' },
+        ],
+    },
 ];

tests/rustdoc-js/generics-unbox.rs

@@ -42,3 +42,15 @@ pub fn beta<T, U>(_: Inside<T>) -> Out<Out3<T, U>, Out4<U, T>> {
 pub fn gamma<T, U>(_: Inside<T>) -> Out<Out3<U, T>, Out4<T, U>> {
     loop {}
 }
+
+pub fn delta(_: i32) -> Epsilon<Sigma> {
+    loop {}
+}
+
+#[doc(search_unbox)]
+pub struct Theta<T>(T);
+
+#[doc(search_unbox)]
+pub type Epsilon<T> = Theta<T>;
+
+pub struct Sigma;