`compile_tr` and `compile_tr_private_experimental` fail for `pk(A)`

[simongltr]

Both compile_tr and compile_tr_private_experimental fail for pk(A). Expected result in both cases is tr(A), extract_key correctly promotes A to the taproot internal key, but the remaining Policy::Unsatisfiable is not handled the same as Policy::Trivial, causing it to fall through to leaf compilation with nothing to compile.

compile_tr_private_experimental also panics for and(pk(A),pk(B)) (compile_tr is fine there).

I discovered this while trying to push for a privacy first taproot compiler in bdk-cli: bitcoindevkit/bdk-cli#244

[va-an]

Tried to reproduce pk(A) failures on current master with:

use std::fmt;
use std::str::FromStr;
use miniscript::policy::Concrete;

fn run<T: fmt::Display, E: fmt::Display>(
    label: &str,
    f: impl FnOnce() -> Result<T, E> + std::panic::UnwindSafe,
) {
    print!("{label}: ");
    match std::panic::catch_unwind(f) {
        Ok(Ok(v)) => println!("OK: {v}"),
        Ok(Err(e)) => println!("ERR: {e}"),
        Err(_) => println!("PANIC!"),
    }
}

fn main() {
    let pk_a = || Concrete::<String>::from_str("pk(A)").unwrap();

    run("compile_tr(pk(A))", || pk_a().compile_tr(None));
    run("compile_tr_private(pk(A))", || pk_a().compile_tr_private_experimental(None));
}

Results:

compile_tr(pk(A)): OK: tr(A)#xyg3grex

thread 'main' (350339) panicked at src/policy/concrete.rs:628:25:
assertion failed: tapleaf_prob_vec.remove(&(Reverse(*prev_prob), policy.clone()))
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
compile_tr_private(pk(A)): PANIC!

I was unable to reproduce the compile_tr failure for pk(A) on current master - it returns tr(A) as expected.
The compile_tr_private_experimental panic is confirmed.

[simongltr]

I re-coded the test and I get the same as you for pk(A) now.

Did the same for and(pk(A), pk(B)) here we need to provide the unspendable key or both fail with ERROR: Taproot compilation had no internal key available. I got this:

compile_tr(and(pk(A),pk(B))): OK: tr(UNSPENDABLE,and_v(v:pk(A),pk(B)))#787dpsca

thread 'main' (28780209) panicked at /Users/simon/src/rust-miniscript/src/policy/concrete.rs:505:25:
assertion failed: tapleaf_prob_vec.remove(&(Reverse(*prev_prob), policy.clone()))
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
compile_tr_private(and(pk(A),pk(B))): PANIC!

The code (your code with adaptations):

use std::fmt;
use std::str::FromStr;

use miniscript::policy::Concrete;

fn run<T: fmt::Display, E: fmt::Display>(
    label: &str,
    f: impl FnOnce() -> Result<T, E> + std::panic::UnwindSafe,
) {
    print!("{label}: ");
    match std::panic::catch_unwind(f) {
        Ok(Ok(v)) => println!("OK: {v}"),
        Ok(Err(e)) => println!("ERR: {e}"),
        Err(_) => println!("PANIC!"),
    }
}

fn main() {
    let and_ab = || Concrete::<String>::from_str("and(pk(A),pk(B))").unwrap();

    run("compile_tr(and(pk(A),pk(B)))", || {
        and_ab().compile_tr(Some("UNSPENDABLE".to_string()))
    });
    run("compile_tr_private(and(pk(A),pk(B)))", || {
        and_ab().compile_tr_private_experimental(Some("UNSPENDABLE".to_string()))
    });
}

Testing on current master too