Bug #81330 [Com]: Generator does not allow return null with implicit yield

Edit report at https://bugs.php.net/bug.php?id=81330&edit=1 ID: 81330 Comment by: greedy dot ivan at gmail dot com Reported by: greedy dot ivan at gmail dot com Summary: Generator does not allow return null with implicit yield Status: Not a bug Type: Bug Package: *General Issues Operating System: All PHP Version: 8.0.9 Assigned To: cmb Block user comment: N Private report: N New Comment: I understand it. This is a refactoring issue. You have a return type hint. You have an yield inside a function. And when you move yield instruction somewhere you get a runtime type error because you generator-function now use return instead of yield. And you get this error not on a primary case. I agree that it is not a bug. One more difficulties with generators in php. Previous Comments: ------------------------------------------------------------------------ [2021-08-04 12:44:05] cmb@php.net Actually, the point is that bar() is not a generator function at all, because there is no yield. You probably want something like <https://3v4l.org/hRSNS>. ------------------------------------------------------------------------ [2021-08-04 12:25:36] greedy dot ivan at gmail dot com There are three options here. 1. There is an yield operator inside a function. Parser gets it and allow to return null as a valid end for generator. 2. There is no yield operator inside a function but there is a return instruction that returns Generator. This line works fine. 3. The same as 2, but we have a line, that returns null. It will throws Error, because Parser doesn't allow return an empty Generator such way. It doesn't get, that function return Generator at all, because there is no yield operation inside function itself. So, we must use some tricks to return empty Generator in this case, or use yield from func() instead for return func(). ------------------------------------------------------------------------ [2021-08-04 11:57:48] cmb@php.net That type check is done at runtime, not compile time. And there is no implicit yield. ------------------------------------------------------------------------ [2021-08-04 11:49:42] greedy dot ivan at gmail dot com It doesn't throw error on all other cases. It will throw Type error only in case, when yield is implicit and null is returned. ------------------------------------------------------------------------ [2021-08-04 11:39:32] cmb@php.net If the generator function does not necessarily return a Generator, you shouldn't declare it as such. ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=81330 -- Edit this bug report at https://bugs.php.net/bug.php?id=81330&edit=1