fuzz: in descriptor parsing regression test, try lifting the result

Author: apoelstra

fuzz/fuzz_targets/regression_descriptor_parse.rs

@@ -14,12 +14,33 @@ fn do_test(data: &[u8]) {
         (Ok(x), Err(e)) => panic!("new logic parses {} as {:?}, old fails with {}", data_str, x, e),
         (Err(e), Ok(x)) => panic!("old logic parses {} as {:?}, new fails with {}", data_str, x, e),
         (Ok(new), Ok(old)) => {
+            use miniscript::policy::Liftable as _;
+            use old_miniscript::policy::Liftable as _;
+
             assert_eq!(
                 old.to_string(),
                 new.to_string(),
                 "input {} (left is old, right is new)",
                 data_str
-            )
+            );
+
+            match (new.lift(), old.lift()) {
+                (Err(_), Err(_)) => {}
+                (Ok(x), Err(e)) => {
+                    panic!("new logic lifts {} as {:?}, old fails with {}", data_str, x, e)
+                }
+                (Err(e), Ok(x)) => {
+                    panic!("old logic lifts {} as {:?}, new fails with {}", data_str, x, e)
+                }
+                (Ok(new), Ok(old)) => {
+                    assert_eq!(
+                        old.to_string(),
+                        new.to_string(),
+                        "lifted input {} (left is old, right is new)",
+                        data_str
+                    )
+                }
+            }
         }
     }
 }