Language: backed enum strict compare with backing scalar — E::A === 1 must be false (Zend/zend_enum.c)

[PurHur]

Category

language · php-src-strict

Problem

Backed enum cases are objects in Zend. Strict comparison with the backing scalar must be false even when the case’s value matches.

This compiler materializes E::A to backing int(1), so:

enum E: int { case A = 1; }
var_dump(E::A === 1);  // Zend: false — VM today: true
var_dump(E::A == 1);   // Zend: false — VM today: true

This breaks type-sensitive code, match exhaustiveness assumptions, and masks the root enum-object bug tracked under #8941 / closed #8746.

php-src reference

• php/php-src Zend/zend_enum.c — enum case as IS_OBJECT, compare hooks
• php/php-src Zend/zend_operators.c — compare_function / strict equality

Repro

php bin/vm.php -r 'enum E: int { case A = 1; } var_dump(E::A === 1, E::A == 1);'
php -r 'enum E: int { case A = 1; } var_dump(E::A === 1, E::A == 1);'

Expression	Zend 8.4	VM today
E::A === 1	bool(false)	bool(true)
E::A == 1	bool(false)	bool(true)
E::A === E::A	bool(true)	bool(true)

Scope

Layer	Files
Enum fetch	Preserve TYPE_ENUM_CASE / object handles on E::A fetch — pairs #8941
Compare	lib/VM/Variable.php equality, lib/VM/InternalCompare.php
JIT	lib/JIT/JitValueCompare.php, SpaceshipCompareJit when enum operands involved

PHP-in-PHP: no new C compare tables.

Done when

• Repro prints false, false on VM like Zend
• E::A === E::B still false; case singleton identity preserved
• Compliance PHPT test/compliance/cases/language/enum_strict_scalar_compare.phpt
• ./script/ci-fast.sh --filter enum_strict_scalar_compare green

Related

• Stdlib: spl_object_id()/spl_object_hash() on enum case objects — must accept enum not backing scalar (ext/spl/php_spl.c) #8941, Regression: backed enum case fetch materializes backing scalar not enum object (re-#8725, zend_enum.c) #8746 — enum case object materialization root
• Stdlib: in_array()/array_search() loose mode matches enum cases via backing coercion (ext/standard/array.c) #8898 — loose in_array coercion (separate but same root)
• North star: Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: cursor-agent-lane-a — starting this run

[PurHur]

Verified on master (2026-06-18): repro php bin/vm.php -r 'enum E: int { case A = 1; } var_dump(E::A === 1, E::A == 1);' prints bool(false) / bool(false); test/compliance/cases/language/enum_compare_backing_scalar.phpt green. Unclaiming — no code change needed.

[PurHur]

Verified green on master 2026-06-18 (worker-lane-a audit). No code change needed — see #1492 north-star queue hygiene.