[RFC] throw expression

6 years ago by Ilija Tovilo — view source — reply

unread

Hi everybody!

Yesterday I stumbled upon this Tweet by Nikita:

https://twitter.com/nikita_ppv/status/1240309838950866946

It answered why this seemingly correct block of code doesn't work:

fn() => throw new Exception('nope');

The answer is rather simple. throw is a statement, not an expression. However, arrow functions only allow a single expression as their bodies. The obvious solution is to convert throw to an expression. This would also allow for the following:

$value = $nullableValue ?? throw new InvalidArgumentException();

$value = $falsableValue ?: throw new InvalidArgumentException();

At the moment this is generally done by moving the throw into a function:

function throwInvalidArgumentException() {

throw new InvalidArgumentException();

}

$value = $nullableValue ?? throwInvalidArgumentException();

or of course by just using an if statement:

if ($nullableValue === null) {

throw new InvalidArgumentException();

}

Neither of those are bad. The new syntax is just slightly more concise.

An implementation of the change can be found here:

https://github.com/php/php-src/pull/5279

It's also noteworthy that the same feature has semi-recently been added to C# 7.0:

https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/throw#the-throw-expression

This has been proposed a handful of times in the internals mailing list but never extensively discussed:

https://externals.io/message/49569 (2010)

https://externals.io/message/15301 (2005)

https://externals.io/message/10553 (2004)

Let me know what you think!

Also, to actually create the RFC I need RFC karma. Can someone grant me those privileges? My username is ilijatovilo.

Thank you!

[RFC] throw expression View as Markdown