rustdoc-search: add test case for bufread -> result<u8>

tests/rustdoc-js-std/bufread-fill-buf.js

@@ -0,0 +1,16 @@
+// ignore-order
+
+const QUERY = [
+    'bufread -> result<u8>',
+];
+
+const EXPECTED = [
+    {
+        'others': [
+            { 'path': 'std::io::Split', 'name': 'next' },
+            { 'path': 'std::boxed::Box', 'name': 'fill_buf' },
+            { 'path': 'std::io::Chain', 'name': 'fill_buf' },
+            { 'path': 'std::io::Take', 'name': 'fill_buf' },
+        ],
+    },
+];