The general idea behind the fix is that quoted literals need to be treated as data. Arc now has two new functions for this purpose: quoted and unquoted.
The fact that (quote {a 1}) now becomes a hash table is a little strange. I’m not entirely sure that’s correct behavior. It depends whether (car '({a 1})) should yield a hash table. It seems like it should, which is reified in the code now.
EDIT: Ok, I've force-pushed the fixed commit. (Sorry for the force-push.)
If you `git reset --hard HEAD~1 && git pull` it should work now.
Personally, I found I prefer racket's pretty-printing with the horrible hash tables compared to something like {pipe "water" a 1 b 2 c ...} because if you try to evaluate `items` or `profs` you won't have a clue what the data is without pretty-printing.
And it turns out I suck at writing pretty-printers. Someone else do it!