Adding update to loop causes state edge to be unwrapped

[kirstenmg]

Error:
thread 'main' panicked at 'Tried to unwrap state edge', src/rvsdg/to_cfg.rs:62:38

Program that fails:

# ARGS: 3
@main(n: int) {
    i: int = const 3;
    x: int = add n i;
.loop:
    c: int = const 7;
    one: int = const 2;

    cond: bool = lt i n;
    y: int = mul c i;
    print y;
    i: int = add i one;
    x: int = mul c i;     <-- without this line the program succeeds
    br cond .loop .done;
.done:
    print x;
    print i;
}

[ezrosent]

How do we reproduce this? The following code seems to pass, but I know there may be other ways to hit the codepath that this code doesn't exercise.

#[test]
fn rvsdg_state_edge_unwrap() {
    const PROGRAM: &str = r#"
    @main(n: int) {
        i: int = const 3;
        x: int = add n i;
    .loop:
        c: int = const 7;
        one: int = const 2;
    
        cond: bool = lt i n;
        y: int = mul c i;
        print y;
        i: int = add i one;
        x: int = mul c i;
        br cond .loop .done;
    .done:
        print x;
        print i;
    }"#;
    let prog = parse_from_string(PROGRAM);
    let cfg = program_to_cfg(&prog);
    let rvsdg = cfg_to_rvsdg(&cfg)
        .unwrap()
        .functions
        .into_iter()
        .next()
        .unwrap();
    let expr = rvsdg.to_egglog_expr();
    let mut termdag = TermDag::default();
    let term = termdag.expr_to_term(&expr);
    let _res_rvsdg = RvsdgFunction::egglog_term_to_function(term, &termdag);
}

[oflatt]

Let's just add that test and close this
This is a pretty old test and it might have been fixed