Yes, but the original boolean seems to have been used for error handling, and the tagged union is also used for error handling. Why have both simultaneously in the same function instead of just one of the two?

Edit: Looking at the code again, perhaps I was mistaken, since the boolean might not have been for error handling, just the result of the function, and C's limitations regarding error handling led it to using something like elog(), apparently a macro defined in https://github.com/postgres/postgres/blob/master/src/include... .