Is it possible to use pattern matching guards in a `while let`?

Question

I have a while let loop which goes over an iterator of Result and uses pattern matching; it goes over the iterator until it either hits an Err or the Ok's value is an empty string:

while let Some(Ok(a)) = some_iterator.next() {
    if a == "" {
        break;
    }
    // ...
}

This code works fine. However, I think the if statement looks ugly and is probably not idiomatic Rust. In match statements, guards can be used in pattern matching, like so:

match foo {
    Some(Ok(a)) if a != "" => bar(a)
    // ...
}

This would be ideal for my while let loop, although the pattern matching employed there doesn't seem to support it, causing a syntax error:

while let Some(Ok(a)) = some_iterator.next() if a != "" { // <-- Syntax error
    // ...
}

Is there any way of using guards like this in the condition of a while let? If not, is there a better way of breaking out of the loop if an empty string is found?

Answer 1

No, while let and if let patterns cannot have guards. There has been some discussion about changing that (e.g. here), but nothing has been decided yet.

Regarding alternatives, I think your version is pretty clear and I can't think of any ways to really improve on that.