As of #969, I'm seeing a new failure case: some fonts (such as Moderustic) are failing to compile because some of the stylistic set features end up with two featureName blocks.

The generated FEA looks like this:

feature ss17 {
        featureNames {
        name "ss17";
    };

    # Stylistic Set 01–20
        featureNames {
        name "Bulgarian letters";
    };

    sub @loclBGR by @loclBGR1;
} ss17;

fea-rs is erroring because it expects there to only be one featureNames statement. A close reading of the relevant bit of spec suggests this is a mistake, and multiple blocks are allowed (they just have to precede any rules) so I'll go and fix that; but I wanted to open this for discussion, since this FEA looks weird, and I was wondering if anyone (@khaledhosny?) knows where it comes from? Specifically the first label block will end up being overwritten by the second, and isn't doing anything.