VoiceOver not reading '-' in Xcode
In VoiceOver Utility, you can go to the Pronunciation tab of the Speech section, and set up custom pronunciations. I've never used VoiceOver before, but I was able to get some custom pronunciations working. I set -= to be replaced by minus equals, and that seemed to work. Additionally, you can make these custom pronunciations app specific, or work in all apps, if you only want Xcode to read hyphens as minus signs. See here for more details.