"Empty case ranges such as case -1 ... 0 are valid,
but recommended to be diagnosed.
"
Why is that an empty range?
Because I'm an idiot and meant to write 0 ... -1.
Ah, that makes more sense. I was re-checking my understanding (and re-reading the GCC docs) that the range is inclusive of both values, but even for 0 ... 0 that would still not be empty.
Re the "A noteworthy quirk of the C2y feature" paragraph, that was documented decades before it got into C2y:
https://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html
It might be worth linking to that page for the implementation experience talking about the extension.
Thanks, added a link, though not in the implementation experience section.
Thanks.