Can trigger assertation failure in experimental compiler

The following unit test

commit c4a38f269369f87e7a9c210eba15a9f54e171965
Author: Andrew Poelstra <apoelstra@wpsoftware.net>
Date:   Tue Mar 12 14:54:09 2024 +0000

    compiler: add unit test that triggers assertation in compile_private_experimental

diff --git a/src/policy/mod.rs b/src/policy/mod.rs
index 7faccbc1..d9e119f4 100644
--- a/src/policy/mod.rs
+++ b/src/policy/mod.rs
@@ -520,6 +520,18 @@ mod tests {
             assert_eq!(desc, expected_desc);
         }
 
+        {
+            let pol = Concrete::<String>::from_str(
+                "thresh(3,pk(A),pk(B),pk(C),pk(D),pk(E),pk(F),pk(G),pk(H))",
+            )
+            .unwrap();
+            pol.compile::<Tap>().unwrap();
+            pol.compile_tr_private_experimental(Some(unspendable_key.clone()))
+                .unwrap();
+            // Don't bother checking the output, which is huge; just confirm that it
+            // does not trigger an assertation failure within the compiler.
+        }
+
         {
             let pol =
                 Concrete::<String>::from_str("thresh(3,pk(A),pk(B),pk(C),pk(D),pk(E))").unwrap();

Causes an assertation failure, as

---- policy::tests::experimental_taproot_compile stdout ----
thread 'policy::tests::experimental_taproot_compile' panicked at src/policy/concrete.rs:507:25:
assertion failed: tapleaf_prob_vec.remove(&(Reverse(*prev_prob), policy.clone()))
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Start with the reproducing unit test in src/policy/mod.rs and inspect the assertion at src/policy/concrete.rs:507. Run policy::tests::experimental_taproot_compile with the provided thresh policy, then trace compile_tr_private_experimental until the assertion is understood. Done means the test completes without an assertion failure.