Bug #79629 [NEW]: Generator duplicating first elements in 7.4.6

From: thiago dot barcala at gmail dot com Operating system: PHP version: 7.4.6 Package: Unknown/Other Function Bug Type: Bug Bug description:Generator duplicating first elements in 7.4.6 Description: ------------ It seems like the fix for https://bugs.php.net/bug.php?id=78434 changed the behavior of generators. In version 7.4.5 the attached test script gives the expected output, but on 7.4.6, iterating over the generator yields the fist elements two times. If I replace: ``` if ($termination) { yield from $iterable; return; } ``` ... with: ``` if ($termination) { foreach ($iterable as $item) { yield $item; } return; } ``` It works as expected in both PHP versions. Test script: --------------- <?php function flatten(iterable $iterable, $termination = false) { if ($termination) { yield from $iterable; return; } foreach ($iterable as $item) { yield from flatten($item, true); } } function testGenerator() { yield [1, 2]; } echo 'Dumping with iterator_to_array:' . PHP_EOL; var_dump(iterator_to_array(flatten(testGenerator()))); echo 'Echoing keys/elements with foreach:' . PHP_EOL; foreach (flatten(testGenerator()) as $key => $item) { echo "key $key => value $item\n"; } Expected result: ---------------- Dumping with iterator_to_array: array(2) { [0]=> int(1) [1]=> int(2) } Echoing keys/elements with foreach: key 0 => value 1 key 1 => value 2 Actual result: -------------- Dumping with iterator_to_array: array(2) { [0]=> int(1) [1]=> int(2) } Echoing keys/elements with foreach: key 0 => value 1 key 0 => value 1 key 1 => value 2 -- Edit bug report at https://bugs.php.net/bug.php?id=79629&edit=1 -- Fix committed: https://bugs.php.net/fix.php?id=79629&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=79629&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=79629&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=79629&r=needscript Try newer version: https://bugs.php.net/fix.php?id=79629&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=79629&r=support Expected behavior: https://bugs.php.net/fix.php?id=79629&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=79629&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=79629&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=79629&r=globals PHP version support discontinued: https://bugs.php.net/fix.php?id=79629&r=phptooold Daylight Savings: https://bugs.php.net/fix.php?id=79629&r=dst IIS Stability: https://bugs.php.net/fix.php?id=79629&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=79629&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=79629&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=79629&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=79629&r=mysqlcfg