Add UI test

tests/ui/macros/issue-98790.rs

@@ -0,0 +1,24 @@
+// run-pass
+
+macro_rules! stringify_item {
+    ($item:item) => {
+        stringify!($item)
+    };
+}
+
+macro_rules! repro {
+    ($expr:expr) => {
+        stringify_item! {
+            pub fn repro() -> bool {
+                $expr
+            }
+        }
+    };
+}
+
+fn main() {
+    assert_eq!(
+        repro!(match () { () => true } | true),
+        "pub fn repro() -> bool { (match () { () => true, }) | true }"
+    );
+}