Language: asymmetric visibility `public private(set)` — compile rejects valid PHP 8.4 (Zend/zend_compile.c)

[PurHur]

Category

language · php-src-strict

Problem

PHP 8.4 asymmetric property visibility (public private(set) int $x) is valid syntax. This compiler rejects it at parse/compile with Multiple access type modifiers are not allowed, blocking PHP 8.4 language parity.

Related runtime gaps (#9842 private(set) write message, #6772 reflection) assume the syntax compiles first.

php-src reference

• php/php-src Zend/zend_compile.c — zend_compile_property_info(), asymmetric visibility flags
• php/php-src Zend/zend_API.c — ZEND_ACC_ASYMMETRIC_* visibility
• php/php-src Zend/zend_language_parser.y — property_modifier grammar (PHP 8.4)

Repro (verified 2026-06-20)

test/repro/maintainer_gap_asymmetric_visibility_compile.php:

<?php
class C {
    public private(set) int $x = 1;
}
$c = new C();
echo $c->x, "\n";

Promoted-parameter variant (test/repro/maintainer_gap_promoted_private_set.php):

<?php
class D {
    public function __construct(public private(set) int $x = 1) {}
}
$d = new D();
echo $d->x, "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php test/repro/maintainer_gap_asymmetric_visibility_compile.php 2>&1 | head -3
php bin/vm.php test/repro/maintainer_gap_promoted_private_set.php 2>&1 | head -3
'

Check	Zend PHP 8.4+	VM today
Property public private(set) compiles	✅	Multiple access type modifiers are not allowed ❌
Promoted public private(set) compiles	✅	same compile error ❌
External read $c->x	prints value	not reached

Scope (PHP-in-PHP first)

Area	Files
Parser	lib/Parser.php / grammar — emit asymmetric visibility CFG ops (partial hooks exist in lib/Compiler.php asymmetric*VisibilityFromCfgOp)
Compiler	lib/Compiler.php — property + promoted-parameter declare paths
VM	lib/VM.php — enforce get/set visibility asymmetry
JIT	lib/JIT/AsymmetricVisibilityGuard.php — route through VM PHP trampoline per #1492

Done when

• Both repro scripts compile and external read prints 1
• External write $c->x = 2 throws Error with Zend Cannot modify private(set) property message (see Language: private(set) property hook write — wrong 'read-only' Error not private(set) message (Zend/zend_property_hooks.c) #9842)
• test/compliance/cases/language/asymmetric_visibility_compile.phpt green
• VM/JIT agree when both in scope

Links

• North star Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 · Language: private(set) property hook write — wrong 'read-only' Error not private(set) message (Zend/zend_property_hooks.c) #9842 · Stdlib: ReflectionProperty::getAsymmetricVisibility() — static properties return wrong/null (ext/reflection/php_reflection.c) #6772

[PurHur]

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

[PurHur]

Merged via #10208.

Fix: AsymmetricVisibilityRewriter::rejectExplicitPublicBeforeSetModifier() no longer rejects valid PHP 8.4 `public private(set)` (and related explicit read+set pairs). Only duplicate same-modifier forms like `public public(set)` remain compile fatal.

Verification:
```bash
php bin/vm.php test/repro/maintainer_gap_asymmetric_visibility_compile.php # 1
php bin/vm.php test/repro/maintainer_gap_promoted_private_set.php # 1
php vendor/bin/phpunit test/unit/AsymmetricVisibilityRewriterTest.php test/unit/AsymmetricVisibilityCompileCheckTest.php --no-configuration # OK (19 tests)
```

External write `$c->x = 2` throws `Cannot modify private(set) property C::$x from global scope` (existing #9842 VM path).