On Thu, 9 Jan 2020 at 20:53, Dik Takken <d.tak...@xs4all.nl> wrote: > On 09-01-2020 17:52, Andreas Hennings wrote: > > On Thu, 9 Jan 2020 at 16:31, Nikita Popov <nikita....@gmail.com> wrote: > > > >> On Thu, Jan 9, 2020 at 4:06 PM Rowan Tommins <rowan.coll...@gmail.com> > >> wrote: > >> > >> An argument could be made that $this does also specify a certain > contract > >> to the caller: That the API may be used fluently or not without change > in > >> functionality. That is > >> > >> $foo->setBar(); > >> $foo->setBaz(); > >> > >> must be strictly equivalent to > >> > >> $foo > >> ->setBar() > >> ->setBaz() > >> ; > >> > >> The same is not the case for a plain "static" type. In fact, I think > that > >> for all other uses of "static" outside of fluent interfaces, not using > the > >> return value would be a programming error. > >> > >> But still, this kind of contract is not a type-system contract, and I'm > not > >> sure it's a good idea to mix other types of API contracts into the type > >> system in this fashion. > >> > > > > We currently don't have another "system" where this kind of info could be > > specified. > > How about: > > public fluent function doWhatever(): static > > Perhaps this could be introduced at some point in the future to enforce > returning $this. >
This would work, but: - The ": static" would be redundant if the method is fluid. - I still would find it more natural to look into the return hint and find ": $this". With fluent + static I would have to look in two places. But I was thinking something else related to the ": $this" (or "fluent"). If we already annotate a method as fluent, then the actual "return $this;" statement is redundant as well. We _could_ make this implicit, so you no longer have to write "return $this;". Not sure if that's a good idea, and definitely not in scope of the ": static" proposal. But I think it is useful to have an idea where we want to go with this. > > > And in this case, $this also implies static, so if we would use whichever > > other system to specify $this, the type hint "static" would become > > redundant. > > > > "@return $this" is common in phpdoc (*) since a while, and so far I have > > not seen any problems with it. > > > > If we ask "where does this lead?", one natural next step might be to > > specifically say that the return type is the same type, but NOT $this. > > So, a promise that we really get a new object which we can modify without > > changing the original object. > > > > I don't know how we would express this. Perhaps ": clone", but this would > > be too specific imo, because whether it is a clone is an implementation > > detail. > > Maybe ": new" ? > To me this would not imply that this has to be the same type.. Either way, I think there is no strong enough reason to introduce a syntax for this case. It would be mostly for wither methods, and these can safely return the original object if the entire thing is designed as immutable. > > Regards, > Dik Takken >
