Unexpected `SetMatches::len()` behavior

[EFanZh]

The document explains SetMatches::len() as “the total number of regexes in the set that created these matches”.

At first sight, I thought SetMatches as a collection of matched regular expression indices, so naturally, I expect the following function to always return true:

fn f(s: &SetMatches) -> bool {
    s.len() == s.iter().count()
}

But it seems that this method always returns the number of all regular expressions in the corresponding RegexSet object, not the number of matched regular expressions.

I think the name of len() strongly suggests that it is consistent with the behavior of iter(), maybe it’s better to rename this method or add a better explanation to reduce confusion.

[BurntSushi]

I probably agree that len and iter should be consistent. But I'm not going to rename it since this change on its own is not worth a breaking change release. I think just adding better docs is good enough here.

[BurntSushi]

In looking over past issues, I stumbled on this one and realized that there is no iter() method. So the premise of the problem described in this issue seems wrong.

[EFanZh]

I see there is a SetMatches::iter method: https://docs.rs/regex/1.5.4/regex/struct.SetMatches.html#method.iter.

[BurntSushi]

Oh, whoops. I did not re-read the issue closely enough.

I think the fix here is to clarify the docs. If I could do it over, I'd choose different names.