Add positional_count field to Lambda

This field is used for static optimization, determining if parameters
are purely positional.

src/integration_test.rs

@@ -183,4 +183,20 @@ mod tests {
             panic!("Expected DateTime, got {:?}", res);
         }
     }
+
+    #[test]
+    fn test_dynamic_call_destructuring_underflow() {
+        let env = Environment::new();
+        let source = "(do 
+            (def call-dynamic (fn [f data] (f data)))
+            (def data [10 [20 30]])
+            (def x (fn [[a [b c]]] (+ a (+ b c))))
+            (call-dynamic x data))";
+        
+        let result = env.run_script(source);
+        if let Err(e) = &result {
+             panic!("Failed: {}", e);
+        }
+        assert_eq!(format!("{}", result.unwrap()), "60");
+    }
 }