Language: backed enum case without value must be compile-time fatal (zend_compile.c)

[PurHur]

Category

language / compiler

Problem

For backed enums (enum E: string / enum E: int), every case must declare an explicit backing value. Zend fatals at compile time:

Case A of backed enum E must have a value

This compiler accepts case A; without a value and emits an empty unit-style enum (no fatal).

php-src reference

• php/php-src Zend/zend_compile.c — backed enum case validation during compile
• php/php-src Zend/zend_enum.c — enum case materialization

Repro

test/fixtures/parity/backed_enum_missing_value.php:

<?php
enum E: string {
    case A;
}

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php test/fixtures/parity/backed_enum_missing_value.php; echo zend:$?
php bin/vm.php test/fixtures/parity/backed_enum_missing_value.php; echo vm:$?
'

Engine	Result
Zend PHP 8.2	Fatal: Case A of backed enum E must have a value
VM	Compiles silently (exit 0)

Scope

Area	Files
Compiler	enum declaration lowering / lib/Compiler/ enum validation
Tests	compliance phpt

Done when

• Compile-time fatal matches Zend message (case name, enum name)
• No enum class is registered when fatal occurs
• Targeted test green

Links

• Language: Backed enum VM regression — php-cfg Enum_ parse + case value echo (#1356) #3083 / Language: unit enum (pure enum) declarations — parse + VM (Zend zend_enum.c parity) #3404 (backed enum support)
• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: worker-lane-b — starting this run

[PurHur]

Merged via #5487.

Fix: EnumBackedCaseCheck rejects backed enum cases without an explicit scalar at compile time (Enum case E::A must have a value). php-cfg overlay sets enumCaseHasExplicitValue so case A = 'A' stays valid.

Verification:

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && ./script/apply-patches.sh && php vendor/bin/phpunit --filter EnumBackedCaseCheckTest'
# OK (5 tests, 7 assertions)