Language: enum method/static param default self $e = self::A compile-rejects (re-#9715, Zend/zend_compile.c) #22085

Category

Language · php-src-strict · enum defaults (re-#9715 / #5885)

Problem

Zend allows enum cases as defaults when the parameter type is self (or the enum name) on enum methods/static methods. This compiler still rejects self $e = self::A at compile time with Cannot use object as default value for parameter … of type self, even though E $e = E::A on ordinary functions/classes already works (2026-07-22).

php-src reference

• php/php-src Zend/zend_compile.c — default value validation / self resolution in enum scope
• php/php-src Zend/zend_enum.c — enum case as constant expression

PHP implementation target

• lib/Compiler.php — when materializing parameter defaults, resolve self/static in enum scope to the enum class before the “object default” reject path (same path that already accepts E::A for named enum types)
• Keep invalid cross-type defaults as compile errors per Zend
• PHP-in-PHP; no new C

Repro

./script/docker-exec.sh -- bash -lc 'cat >/tmp/enum_self_default.php <<'"'"'P'"'"'
<?php
enum E {
  case A;
  case B;
  public function other(self $e = self::A): string {
    return $e->name;
  }
  public static function make(self $e = self::B): string {
    return $e->name;
  }
}
echo E::A->other(), "|", E::make(), "\n";
P
php /tmp/enum_self_default.php
php bin/vm.php /tmp/enum_self_default.php'

Done when

• Repro prints A|B on VM (and JIT/AOT when in scope)
• Ordinary E $e = E::A defaults remain green
• Compliance .phpt under test/compliance/cases/language/
• php-src-strict; no php-compiler-strict shortcut

Related

• Closed baseline: Language: enum case as parameter/property default must compile (Zend/zend_compile.c) #9715 / Language: optional parameter default with enum case (E $e = E::A) must compile (zend_compile.c) #5885 / Regression: enum typed parameter / instance property defaults — compile rejects after #9715 closed (Zend/zend_compile.c) #9895 (named enum type defaults)
• Backlog mention: Parity backlog snapshot 2026-06-19 (b) — class const new, enum static default, highlight regressions (refs #1492) #9978 (“enum static default”)