On 29 March 2018 at 21:08, Jonathan M Davis via Digitalmars-d <digitalmars-d@puremagic.com> wrote: > On Thursday, March 29, 2018 23:28:54 Nick Sabalausky via Digitalmars-d > wrote: >> On 03/23/2018 09:06 PM, Jonathan M Davis wrote: >> > My biggest concern in all of this is that I don't want to see ref start >> > accepting rvalues as has been occasionally discussed. It needs to be >> > clear when a function is accept an argument by ref because it's going >> > to mutate the object and when it's accepting by ref because it wants to >> > avoid a copy. >> That ship sailed ages ago: It's already unclear. If we want to fix that, >> we can fix it, but blocking rvalue ref does nothing for that cause. > > Really? And how often does ref get used just to avoid copying? You can > almost always look at a function, see that it accepts ref, and know that > it's supposed to mutate the argument. Functions that want to avoid copying > lvalues usually use auto ref, not ref, whereas if ref accepted rvalues, a > number of folks would start using it all over the place to avoid copying. > Right now, folks rarely use ref that way, because it becomes too annoying to > call the function with an rvalue. So, while it might not be the case 100% of > the time right now that ref is used with the purpose of mutating the > argument, it almost always is. As such, you can pretty reliably look at a > function signature and expect that if one of its parameters is ref, it's > going to be mutating that argument. The function that accepts an argument by > ref with no intention of mutating it is very much the exception, and I > really don't want to see that change.
Interesting. Just understand that you're trading that feeling for a suite of edge cases though. Accepting asymmetric calling rules is a pretty big cost to pay for that 'nice thought'. That idea also dismisses the existence of the set of cases where ref is genuinely useful/correct. Your sentiment effectively puts those use cases into the position of 2nd-class citizens. I understand your sentiment, but I think the cost is not balanced, or even particularly fair with respect to users in those niche groups :/
