panic if valid entry already exists at index

Author: manishbista28

g16ckt/src/circuit/modes/execute_mode.rs

@@ -113,7 +113,13 @@ impl CircuitMode for ExecuteMode {
         }
 
         self.storage
-            .set(wire_id, |entry| *entry = Some(value))
+            .set(wire_id, |entry| {
+                assert!(
+                    entry.is_some(),
+                    "overwriting wire_id {wire_id} value in storage"
+                );
+                *entry = Some(value)
+            })
             .unwrap();
     }