Re: Proposal: AS assertions

On Fri, 22 Mar 2024, at 08:17, Jordi Boggiano wrote: > We perhaps could make sure that as does not throw if used with > ??, or that ?? catches the type > error and returns the right-hand expression instead: > So to do a nullable typecast you would do: > > $a as int|float ?? null > While this limits the impact to only expressions combining as with ?? it still has the same fundamental problem: you can't meaningfully use it with a nullable type. As a concrete example, imagine you have an optional $description parameter, and want to ensure any non-null values are converted to string, but keep null unchanged. At first sight, it looks like you could write this: $descString = $description as string|null ?? (string)$description; But this won't work - the ?? swallows the null and turns it into an empty string, which isn't what you wanted. You need some syntax that catches the TypeError, but preserves the null: $descString = $description as string|null else (string)$description; // or $descString = $description as string|null catch (string)$description; // or $descString = $description as string|null default (string)$description; I actually think there are quite a lot of scenarios where that idiom would be useful: $optionalExpiryDateTime = $expiry as ?DateTimeInterface else new DateTimeImmutable($expiry); $optionalUnixTimestamp = $time as ?int else strotime((string)$time); $optionalUnicodeName = $name as ?UnicodeString else new UnicodeString( $name ); etc And once you have that, you don't need anything special for the null case, it's just: $nameString = $name as ?string else null; Regards, -- Rowan Tommins [IMSoP]