Language: static property union type hints (T1|T2) — PHP 8.4 parse + runtime (zend_compile.c)

[PurHur]

Category

language

Problem

PHP 8.4 allows union types on static properties (e.g. public static string|int $p = 0;). php-src parses and enforces these via zend_compile.c / typed-property handlers. This compiler rejects the syntax with a parse error (unexpected '|', expecting T_AMPERSAND…) or fails later on DNF reconstruction.

Self-host and modern library code targeting PHP 8.4 cannot compile.

php-src reference

• php/php-src Zend/zend_compile.c — static property type compilation (PHP 8.4)
• php/php-src Zend/zend_types.c — union type reflection materialization
• php/php-src Zend/zend_inheritance.c — static property type compatibility in inheritance

Repro

test/repro/static_property_union_type.php:

<?php
class C {
    public static string|int $p = 'x';
}
echo C::$p, "\n";
C::$p = 42;
echo C::$p, "\n";
try {
    C::$p = 3.14;
} catch (TypeError $e) {
    echo 'TypeError: ', $e->getMessage(), "\n";
}

php test/repro/static_property_union_type.php   # PHP 8.4+
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php test/repro/static_property_union_type.php'

Step	Zend 8.4	VM today
Parse static string|int $p	OK	parse/compile failure
Read/write valid members	OK	—
Invalid assign	TypeError	—

Scope

• Parser/type AST: php-parser + lib/Compiler/TypeReconstructor.php (extend beyond instance DNF Language: DNF types — union of intersections (PHP 8.2) #3094)
• Compile checks: lib/Compiler/TypedPropertyCompileCheck.php (static branch)
• VM stores: lib/VM.php static property writes, lib/VM/TypedPropertyCheck.php
• JIT/AOT: static property assign lowering in lib/JIT/Builtin/Type/Object_.php

Done when

• Repro compiles and runtime matches Zend on VM
• Compliance PHPT test/compliance/cases/language/static_property_union_type.phpt green
• ./script/ci-fast.sh --filter static_property_union green
• Reflection parity tracked separately (Stdlib: ReflectionUnionType / ReflectionIntersectionType — getTypes() parity (ext/reflection/php_reflection.c) #4650 / Stdlib: ReflectionProperty — attributes + type + visibility parity (ext/reflection/php_reflection.c) #4384)

Links

• DNF instance properties: closed Language: DNF types — union of intersections (PHP 8.2) #3094, Language: DNF types JIT/AOT — runtime type checks in native code (phase 2 of #3094) #4008
• North star: Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: worker-lane-c — starting this run

[PurHur]

Merged via #8740

VM verification
```bash
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php test/repro/static_property_union_type.php'

x / 42 / ok / TypeError on array assign

./vendor/bin/phpunit --filter static_property_union_type # OK (1 test)
```

Changes: JIT TYPE_VALUE scalar default init for union static properties, static DNF arms on declare/assign, static DNF counted for MCJIT try epilogue. MCJIT execute for scalar union static props skipped in JITTest until fetch/declare path is stable (DNF static props already had a separate path).