Re: [RFC] Unary null coalescing operator

On Thu, Jun 22, 2017 at 10:52 PM, Andrea Faulds <ajf@ajf.me> wrote: > Hi Stas, > > Stanislav Malyshev wrote: > >> Hi! >> >> I think that if ($_GET['x']?? === 1) looks and >> feels a lot like `if >>> (@$_GET['x'] === 1)`... >>> >>> Yes, the latter has runtime performance issues and will still send >>> notices to error handlers and logs. But perhaps if we're going to >>> extend syntax, the syntax could be something along the lines of: >>> >> >> I'd rather fix @ (or make another operator like @@ that Sara proposed) >> to make nullsafe access - and maybe even extend it to full expression >> like isset/empty does - so I could do something like >> @$foo['bar']->blah->foo['bah'] and have it mean "try to >> fetch the whole >> chain and if something is missing on the way return null". I kinda get >> the argument for PHP not doing it by default, though I personally could >> live with that too ;) - but I still need this thing quite frequently >> when dealing with all kinds of dirty data. >> > > You already can use @. I'm not sure how it could be "fixed": the > fundamental problem with @ is that it is a blunt-force instrument that > mutes all errors, but this is also its purpose, and any change to that will > break some use cases. The best fix would be to get rid of it entirely, but > we can't do that since it actually has to be used in some cases right now, > in particular standard library functions that produce E_WARNINGs on I/O > errors. > > With trailing ?? it is not clear how it would chain, >> > > It's a unary operator, I don't know what “chain” would mean for one. You > can use it within other expressions (1 + $a?? is valid, for example), and > you can nest it within itself ($a???? is also valid, though I've no idea > why you'd do that). > > and even if it >> chains having something at the end that changes how the expression is >> interpreted is both confusing and may be very hard for the parser. >> > > Unary ?? is a two-line addition to the syntax and completely unambiguous > from a parsing perspective. > As has been pointed out on reddit, unary ?? is ambiguous for cases like $a?? - 1, which could be either ($a??) - 1 or $a ?? (-1). Of course, precedence resolution is possible, but I wouldn't call the syntax unambiguous. Nikita