Field math works similar to condition evaluation, but not the exact same
because we have more information to work with in field expressions than
we do in conditional math because fields retain the information about
their source while conditions do not.
The main difference is that you cannot add an unsigned literal to the
output of an integer iterator while you can inside of a condition. You
can perform math on a positive integer literal to an unsigned iterator.
Inside of the condition, we aren't sure if an integer is because of a
literal or because of an iterator so we can't make that distinction.
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