Love the addition!
Wanted to share a gut reaction to the printouts, I immediately read the [] in 15[utf8]+1 as a subscript, and it didn’t read at all like a unit (which I found out only after reading the pitch thread). I wonder if utf8[15] + int[1]or utf8[15 + 1] would be more recognizable to most swift devs who would be seeing them, especially since they would immediately read as indexes of a particular view this way.