Break and continue support

[idavis]

Closes #1835

[amcasey]

This is probably supposed to report that break isn't allowed there, rather than that the type couldn't be inferred

operation Main() : Unit {
    mutable x = 1;
    while (true) {
        () -> break;
    }
    x += 1;
}

QdkDiagnostics: type error: insufficient type information to infer type

help: provide a type annotation at code:4:15

[amcasey]

This reports an RIR timeout

operation Main() : Unit {
    use q = Qubit();
    for p in [q] {
        for p in [q] {
            for p in [q] {
                for p in [q] {
                    for p in [q] {
                        for p in [q] {
                            break
                        }
                    }
                }
            }
        }
    }
}

[amcasey]

Would you expect the local playground to pick this up? I'm not seeing it.

[idavis]

@amcasey I think monaco uses their own language def based on ours. @billti - do you remember?

[amcasey]

I'm seeing an LS panic (and a possibly downstream RIR generation failure) for

@EntryPoint(Adaptive)
operation Main() : Result {
    use qq = Qubit[2];
    repeat {
        H(qq[0]);
        Controlled X([qq[break]], qq[1]);
    } until (M(qq[1]) == One)
    fixup {
        ResetAll(qq);
    }
    let r = M(qq[0]);
    ResetAll(qq);
    r
}

[error] [wasm] Wasm panic occurred: panicked at source\compiler\qsc_partial_eval\src\lib.rs:2722:18:
invalid kind of value for index

RuntimeError: unreachable

Related: with Controlled X([break], qq[1]);, I see

QdkDiagnostics: partial evaluation error: partial evaluation failed with error: index out of range: 0 at code:6:23

Interestingly, Controlled X(break, qq[1]); appears to work (i.e. emit QIR and run)

[amcasey]

LS panic for

@EntryPoint(Adaptive)
operation Main() : Result {
    use qq = Qubit[2];
    repeat {
        H(qq[0]);
        use rr = Qubit[break];
        Controlled X(break );
    } until (M(qq[1]) == One)
    fixup {
        ResetAll(qq);
    }
    let r = M(qq[0]);
    ResetAll(qq);
    r
}

Wasm panic occurred: panicked at source\compiler\qsc_rca\src\core.rs:2807:13:
expected tuple expression

I was about to type a comma after the break in the Controlled

[amcasey]

I don't think this needs to work, but it stands out from a bunch of other nonsensical code that does work

@EntryPoint(Adaptive)
operation Main() : Result {
    use qq = Qubit[2];
    repeat {
        H(qq[break]);
        Controlled X(continue, qq[1]);
    } until (M(qq[1]) == One)
    fixup {
        ResetAll(qq);
    }
    let r = M(qq[0]);
    ResetAll(qq);
    r
}

main.qs@(4,5): cannot use a dynamically-sized array
help: using an array whose size depends on a measurement result is not supported by the configured target profile

In particular, the same example emits QIR with H(qq[continue]) (though I'm pretty sure it would loop infinitely?)