Language: enum class/trait/interface constants — E::X must resolve (zend_enum.c, zend_constants.c) #6407

Category

language

Problem

Enum types cannot resolve class constants declared on the enum itself or inherited via traits/interfaces. E::X throws Error: Undefined class constant E::X in the VM; Zend returns the constant value.

Related stdlib gaps (#5682, #3484) cover constant('E::A') for enum cases, not public const / trait const on enum types.

php-src-strict: direct E::X, constant('E::X'), and trait-merged constants must match Zend.

php-src reference

• php/php-src Zend/zend_enum.c — enum constant table
• php/php-src Zend/zend_constants.c — zend_fetch_class_constant_ex()
• php/php-src Zend/zend_compile.c — trait const merge on enums

Repro (failure today)

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php test/repro/maintainer_enum_class_constant.php   # Error: Undefined class constant E::X
php bin/vm.php test/repro/parity_enum_trait_const.php          # trait const on enum — same failure
php test/repro/maintainer_enum_class_constant.php              # Zend: 42
php test/repro/parity_enum_trait_const.php                     # Zend: 1
'

<?php
// enum-declared constant
enum E { case A; public const X = 42; }
echo E::X; // VM: Error; Zend: 42

// trait constant on enum
trait T { public const X = 1; }
enum E { use T; }
echo E::X; // VM: Error; Zend: 1

Implementation hints (PHP-in-PHP)

• Register enum constants in compiler symbol tables (lib/ lowering), not new C branches in runtime/.
• Trait/interface constant merge should reuse existing trait merge paths; ensure enum TYPE_ENUM stores constants separately from case objects.
• VM: FETCH_CLASS_CONSTANT / ClassConstFetch for enums must read enum constant table, not only case materialization.
• Add test/compliance/cases/language/enum_class_constant.phpt + trait variant; JIT/AOT when enum const fetch is lowered.

Verification

• Repro scripts above green on VM
• Filter: vendor/bin/phpunit test/compliance/VMTest.php --filter enum_class_constant (after adding case)