Checking if required init? failed from a convenience init

Using Swift
4

Yeah, this predates try/throws, as a port of the ObjC idiom:

self = [self init];
if (!self) {
  return nil
}

We knew that we didn't want people to forget assigning to self, and that we didn't want the nil to go untested and later be a problem if someone tried to access a variable. I'm not sure we even had guard yet, which meant we didn't have a construct that forced you to exit if you wanted to do any cleanup, but even then there usually wasn't any cleanup, in the fast majority of ObjC code that followed this idiom:

guard self.init() else {
  return nil
}

So it's just implicit. Now that you point it out it does seem weird though. (And if we supported guard self.init(), it would also allow delegating from a throwing convenience init to an optional-failable init, as proposed way back in 2015.)

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