Modify test to check everything is not sent to dead

If the code skips visit_nested_body without additional care, some parts are marked as dead. I added a new line on the test to confirm the fix doesn't cause such problem.

Signed-off-by: Shunpoco <[email protected]>

Author: Shunpoco

tests/ui/consts/do-not-ice-long-constant-evaluation-in-for-loop.rs

@@ -1,6 +1,13 @@
-// Issue-125323
+// The test confirms ICE-125323 is fixed.
+//
+// This warning makes sure the fix doesn't throw everything with errors to dead.
+#![warn(unused)]
+fn should_not_be_dead() {}
+
 fn main() {
     for _ in 0..0 {
         [(); loop {}]; //~ ERROR constant evaluation is taking a long time
     }
+
+    should_not_be_dead();
 }