Minification bug: erroneous fusion of operator symbols

Sorry @user135362 please don't waste any time answering @Robin. For some reason he repeatedly ignores my requests not to post when he has nothing useful to add.

@Robin I've mentioned this in personal messages, but let's just say it publically: I've never banned anyone from this forum, but I'm fed up reading your toxic, smart-arse comments every day and I've lost track of how many people you've offended or put off. I've repeatedly warned you via PMs and email and I just get ignored. If I feel I ever have to warn you again, you're getting banned.

Right. @user135362 - thank you!

So as far as I can tell this comes not from the minification in the IDE, but from Espruino's internal minification that it applies when E.setFlags({pretokenise:1}) is set, which is the default for Bangle.js

E.setFlags({pretokenise:0}) // change this to 1 and it breaks
a = () => print(1 - -1)
a();

I've filed an issue for it here: https://github.com/espruino/Espruino/iss­ues/2086

I guess one question is how I actually fix this. I can explicitly keep a space between - - and + + but can you think of other combinations in valid JS that would also cause issues? Looking at the list of tokens I can't see anything obvious.