Re: Proposal: AS assertions

On Thu, Mar 21, 2024 at 7:01 PM Rowan Tommins [IMSoP] <imsop.php@rwec.co.uk> wrote: > > On 21/03/2024 15:02, Robert Landers wrote: > > I don't think you are getting what I am saying. > > $a as int|float > > would be an int, float, or thrown exception. > > $a as int|float|null > > would be an int, float, or null. > > > I get what you're saying, but I disagree that it's a good idea. > > If $a is 'hello', both of those statements should throw exactly the same error, for > exactly the same reason - the input is not compatible with the type you have specified. > > > > Another way of thinking about is: > > $x = $a as null > > What do you expect $x to be? > > > The same as $x inside this function: > > function foo(null $x) { var_dump($x); } > foo($a); > > Which is null if $a is null, and a TypeError if $a is anything else: > https://3v4l.org/5UR5A > > > Regards, > > -- > Rowan Tommins > [IMSoP] I suppose we are taking this from different viewpoints, yours appears to be more of a philosophical one, whereas mine is more of a practical one. $x = $a as null; (or any other value, such as true|false) appears to have no practical purpose in this particular case. This is better checked with ===, or even in_array(). Values are easy to check in PHP and there are already lots of great and simple ways to check a value. Further, reading "$x = $a as null", as a native English speaker, appears to be the same as "$x = null". As I mentioned in the beginning, I see this mostly being used when dealing with mixed types from built-in/library functions, where you have no idea what the actual type is, but when you write the code, you have a reasonable expectation of a set of types and you want to throw if it is unexpected. Right now, the best way to do that is to simply set a function signature and pass the mixed type to the function to have the engine do it for you; or write out a bunch of instanceofs when that isn't worth it. However, this is cumbersome. I'd also like to say that I'm not strongly attached to the |null behavior I'm proposing, but there are better ways to assert a variable is equal to a value. It makes more sense, from a practical programming point-of-view, to simply return the value given if none of the types match. Robert Landers Software Engineer Utrecht NL