[swift-evolution] Optional Argument Chaining

Magnus Ahltorp map at kth.se
Mon Dec 11 12:34:42 CST 2017

> 12 Dec. 2017 02:58 Jared Khan <jaredkhan at me.com> wrote:
> 2. It felt natural to me. It’s analogous to the existing optional chaining scenarios and composes nicely. I think it’s about as understandable as existing chaining, a newbie would have to look it up to discover its meaning. What are your thoughts on this particular syntax (ignoring 3. momentarily)? Hopefully others in this thread can share their views too.

Chaining methods is linear, while nesting fills a similar purpose when we use function calls. This of course affects the way existing Swift code is written, but that is something we have to live with if we want to use familiar syntax patterns. However, I think we have to consider this difference in this case, since the syntax becomes more convoluted. Your suggestion is definitely not as easy to read as the optional chaining syntax, and maybe it can't be.

> As for how common I’d expect it to be, it’s something I’ve run into myself a few times. Again, I hope members of this list can give their view on if this would be useful to them.

I don't have any real examples, but I certainly think that I have run into it, so I'm quite open to solving the problem. For me, it is probably only a matter of finding a syntax that is acceptable.

> 3. I’m not entirely sure what the grammar situation is yet but afaik ‘?’ has never been available as a postfix operator. Perhaps I’m missing your point, could you demonstrate where it is allowed?

I did not expect that you would be able to answer that, it was more a question directed to people who are more connected to the inner workings of the parsing of Swift than I am. It is not allowed, but the error message is not the one I expect, something that gives me a hint that it does have some meaning early in the parsing.  


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