Handle the case when the Fixup suggested isn't a valid c/c++ identifer.
I don't think we need to tell that to the user. When Clang can't provide a fix, it just silently omits it. It does not help the user to know. that Clang tried, but failed.
(This message could be also read as "this code is so bad it can't be fixed"...)
Oh I see, this checker has a number of messages like that... Well, feel free to keep it, but what seems weird to me as a user is that for an input name of "_0Bad" the checker automatically chose somehow "0_Bad" (why?), and then concluded that it is not a good choice. This looks like irrelevant information because the new name is weird. I can totally see how reminding the user that "Break"->"break" is not easily possible because the latter is a keyword.
Feel free to ignore me since this checker already produces messages like this.