Language: regression — backed enum === / == with backing scalar still true (#5798, PR #5802)

[PurHur]

Category

language · php-src-strict · regression

Problem

#5798 was closed via PR #5802 (Variable::identicalTo / equals enum-vs-scalar guards), but the maintainer repro and compliance case enum_compare_backing_scalar.phpt still fail on VM (2026-06-04): E::A === 1, E::A == 1, and string-backed S::B === 'x' all return true.

Likely causes to investigate:

1. E::A not materialized as TYPE_ENUM_CASE at runtime (php-cfg isEnumCase / script/apply-patches.sh — enum case parsed as plain const).
2. Compare path bypasses Variable::identicalTo (constant-folded backing literal in compileClassConstFetch).

php-src reference

• php/php-src Zend/zend_operators.c — compare_function / identity
• php/php-src Zend/zend_enum.c

Repro

test/repro/maintainer_enum_compare_regression_5798.php (also test/compliance/cases/language/enum_compare_backing_scalar.phpt):

docker info >/dev/null
./script/docker-exec.sh -- bash -lc 'php test/repro/maintainer_enum_compare_regression_5798.php'
./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/maintainer_enum_compare_regression_5798.php'

Implementation (PHP-in-PHP)

• Ensure enum case constants load as enum case objects (lib/Compiler.php compileTimeEnumCaseVar, lib/VM.php TYPE_DECLARE_CLASS_CONST, copyClassConstOrStaticPropertyByName).
• Keep compare guards in lib/VM/Variable.php; add compliance green on VM before closing.
• JIT/AOT: same semantics in lowered compares when required by compliance.

Verification

./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/maintainer_enum_compare_regression_5798.php'
./script/ci-local.sh --filter 'enum_compare_backing_scalar'

[PurHur]

claim: worker-lane-c — starting this run

[PurHur]

Merged via #5857

Root cause: When enum case constants were stored as backing scalars (legacy table / missing enumCaseCanonicalNames), E::A fetched as int 1 so Variable::identicalTo guards never ran and E::A === 1 was true.

Fix: Materialize enum cases on class const fetch via enumCases metadata (EnumCaseSupport::tryMaterializeEnumCaseConstantFetch); compile-time isEnumCaseDeclare fallback when php-cfg isEnumCase flag is missing (flags=0 heuristic).

Verification:

./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/maintainer_enum_compare_regression_5798.php'
./script/docker-exec.sh -- bash -lc 'php vendor/bin/phpunit --filter "VmEnumCompareBackingScalarRegressionTest|enum_compare_backing_scalar"'
# OK (6 tests, 12 assertions)