Process substitution should be given a priority
Process substitution should be given a priority. Many Unix and Linux commands operate on files, and not because the creators of these utilities made any sort of bad decision, but because it was logical for these commands to operate on files rather than strings - and notwithstanding this, it is nevertheless often useful to make these utilities operate on strings using process substitution. The following link illustrates how full generality requires that Ion shell implement process substitution:
Sets don't really constitute an edge case here. There are a great many utilities that operate on files that can usefully be coerced into operating on strings using process substitution. Implementing process substitution in Ion shell should be given a priority.