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

Edit report at https://bugs.php.net/bug.php?id=81330&edit=1 ID: 81330 Updated by: cmb@php.net 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: That type check is done at runtime, not compile time. And there is no implicit yield. Previous Comments: ------------------------------------------------------------------------ [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. ------------------------------------------------------------------------ [2021-08-04 11:29:25] greedy dot ivan at gmail dot com Description: ------------ If there is not explicit yield instruction in Generator, it will throw TypeError message when null is returned. https://3v4l.org/EpIjA Test script: --------------- <?php function foo($flag = false): \Generator { if ($flag) { return null; } yield from [1, 2]; } function bar($flag = false): \Generator { if ($flag) { return null; } return internal(); } function internal(): \Generator { yield from [1, 2]; } foreach (foo() as $v){} foreach (foo(true) as $v){} foreach (bar() as $v){} foreach (bar(true) as $v){} Expected result: ---------------- No error Actual result: -------------- Fatal error: Uncaught TypeError: bar(): Return value must be of type Generator, null returned in /in/EpIjA:15 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=81330&edit=1