macros: Add parentheses in repetition test case

Author: CohenArthur

gcc/testsuite/rust/execute/torture/macros21.rs

@@ -0,0 +1,15 @@
+macro_rules! add_parens {
+    ($($rep:ident ( ) )*) => {
+        { 0 $(+ $rep ( ))* }
+    };
+}
+
+fn f() -> i32 {
+    1
+}
+
+fn main() -> i32 {
+    let a = add_parens!(f() f() f());
+
+    a - 3
+}