Bug #80126 [NEW]: Covariant return types failing compilation

From: terence-marks at zencontrol dot com Operating system: Debian Buster PHP version: 7.4.10 Package: Compile Failure Bug Type: Bug Bug description:Covariant return types failing compilation Description: ------------ Discovered an issue with narrowing return type using covariance. I have a chain of inheritance (...ignore implementation details) from which at the lowest level I attempt to narrow the return type for an inherited method. When running the code PHP fails at compilation stating the method is not compatible. Now the weird part is it seems the covariance check passes if I remove all interfaces from the lowest level (see example). The attached test script should point you guys in the right direction. Cheers, Terence Test script: --------------- <?php interface Poo { public function poo(): Poo; } abstract class AbstractPoo implements Poo { public function poo(): Poo { return new static(); } } class ConcretePoo extends AbstractPoo { } interface B { } // Fails if interface is present class ExtendedConcretePoo extends ConcretePoo implements B { public function poo(): ExtendedConcretePoo { return new static(); } } // Does not fail if no interfaces present //class ExtendedConcretePoo extends ConcretePoo //{ // public function poo(): ExtendedConcretePoo // { // return new static(); // } //} $e = new ExtendedConcretePoo(); $r = $e->poo(); Expected result: ---------------- No compilation errors. Actual result: -------------- Declaration of ExtendedConcretePoo::poo(): ExtendedConcretePoo must be compatible with AbstractPoo::poo() -- Edit bug report at https://bugs.php.net/bug.php?id=80126&edit=1 -- Fix committed: https://bugs.php.net/fix.php?id=80126&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=80126&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=80126&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=80126&r=needscript Try newer version: https://bugs.php.net/fix.php?id=80126&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=80126&r=support Expected behavior: https://bugs.php.net/fix.php?id=80126&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=80126&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=80126&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=80126&r=globals PHP version support discontinued: https://bugs.php.net/fix.php?id=80126&r=phptooold Daylight Savings: https://bugs.php.net/fix.php?id=80126&r=dst IIS Stability: https://bugs.php.net/fix.php?id=80126&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=80126&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=80126&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=80126&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=80126&r=mysqlcfg