Re: Union type casts

> On 5 Oct 2022, at 12:41, Dusk <dusk@woofle.net> wrote: > > On Oct 4, 2022, at 21:46, Eugene Sidelnyk <zsidelnik@gmail.com> wrote: >> $foo = (int|float)$bar; > > As written, I wouldn't know what to expect this to do with a string value -- would it cast > it to int or float? > > Based on the behavior of your second example, the answer appears to be "float", so > this syntax seems to be equivalent to: > > $foo = \is_int($bar) ? $bar : (float) $bar; > > Or, even more concisely: > > $foo = 0+$bar; > > I'd be even less sure what to expect when casting to other union types. What would the > expected result of casting a string to (bool|array|object) be, for example? I'm not sure there > are many meaningful operations which could be constructed here. > -- > PHP Internals - PHP Runtime Development Mailing List > To unsubscribe, visit: https://www.php.net/unsub.php > Hi, I think the intention is that it would follow precisely the same casting rules as function parameters do. So e.g: ``` function foo(int|float $var) { return $var; } $f1 = foo(‘1’); $c1 = (int|float) ‘1’; $f2 = foo(‘1.1’); $c2 = (int|float) ‘1.1’; ``` In both scenarios the $f1/$c1 and $f2/$c2 would result in the same type. Your first example isn’t quite the same though; Passing ‘1’ to a parameter typed as int|float will cast it to an integer, your example casts such a value to a float. The 0+$value thing is interesting, but also definitely seems less intuitive to my eye. Given your last comment I think its worth reiterating Eugene’s point is simply about exposing the **existing** cast behaviour that happens with typed parameters, to be usable on variables. I can see some benefit in the proposal, but I think I’d be more interested in the ability to define local variables as being a given type (or union), and then have the engine cast (or error) when assigning to them - essentially how typed object properties work, but for regular variables.