Language: Typed properties, union types, and readonly (PHP 8+)

[PurHur]

Category

language

Problem

class C { public string $name; public int|string $id; public readonly string $code; } parses, but VM does not enforce property types on write. Assigning int to string $x succeeds silently (verified May 2026). This blocks Zend parity for Router/config objects and self-host code using typed properties throughout lib/.

php-src reference

• php/php-src Zend/zend_compile.c — typed property flags on zend_property_info
• php/php-src Zend/zend_execute.c — ZEND_ASSIGN_OBJ, type checks + readonly guard
• php/php-src Zend/zend_type.c — union assignability

Repro (failure today)

Typed property write

<?php
class C { public string $x = ''; }
$c = new C();
$c->x = 123;
echo $c->x;

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php repro.php'
# prints 123 (Zend: TypeError)

Readonly second assign

<?php
class C { public readonly string $code = 'x'; }
$c = new C();
$c->code = 'y';

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php repro_readonly.php'
# succeeds (Zend: Error "Cannot modify readonly property")

Union accept/reject

<?php
class C { public int|string $id = 0; }
$c = new C();
$c->id = 'ok';
$c->id = [];

Zend: first assign ok, second TypeError.

Scope (this repo)

Module	Path
Compiler metadata	lib/Compiler.php — persist Type on TYPE_DECLARE_PROPERTY
VM assign	lib/VM.php — TYPE_PROPERTY_ASSIGN enforce + readonly
Types	lib/Type.php or php-types assignability helpers
Uninitialized read	coordinate #3429
Tests	test/compliance/cases/language/typed_property_*.phpt
Phase 2	JIT/AOT after VM green (#55, #58)

Done when

• Typed write repro throws TypeError on VM (message subset ok)
• Readonly second-assign throws Error (or compile-time fatal where Zend does)
• Union int|string accepts int and string, rejects array
• ./script/ci-fast.sh --filter typed_property green
• No regression on untyped properties / dynamic props (Language: Dynamic properties deprecation — PHP 8.2+ undeclared writes (Zend zend_object_handlers parity) #3253)

Verification

./script/ci-fast.sh --filter typed_property
php script/bootstrap-inventory.php --check  # typed props in lib/ should stop warning-only assigns

Links

• Language: Typed property array (private array $config) in VM/JIT/AOT #767 Router private array $config · Language: Visibility, constructors, and destructors #145 visibility · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 self-host
• Language: readonly properties on non-readonly classes (PHP 8.1+) #3149 readonly on non-readonly classes · Language: promoted readonly constructor parameters (public readonly string $x) — Zend compile parity #3432 promoted readonly params
• Language: Typed properties, union types, and readonly (PHP 8+) #169 umbrella — claim only this issue per worker run

[PurHur]

Implementation-ready spec (parity architect, May 2026)

Category: language

Problem (current behavior)

Typed properties parse and store metadata but do not enforce Zend TypeError on incompatible writes. VM accepts int into public string $n and echoes 1 instead of throwing.

php-src reference

• Zend/zend_types.c — zend_verify_property_type, zend_verify_type
• Zend/zend_execute.c — ZEND_VERIFY_PROPERTY_TYPE
• Zend/zend_inheritance.c — union type zend_class_implements_interface checks for properties

Repro

<?php
class C {
    public string $n = '';
}
$c = new C();
$c->n = 1; // must TypeError on Zend

# Zend (reference)
php -r 'class C{public string $n="";} $c=new C(); $c->n=1;'
# → TypeError: Cannot assign int to property C::$n of type string

# This compiler (today)
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php -r "
class C { public string \$n = \"\"; }
\$c = new C(); \$c->n = 1; echo \$c->n;
"'
# → prints 1 (wrong)

Existing compliance test/compliance/cases/language/typed_property_public.phpt only checks valid writes — add typed_property_type_error.phpt for invalid.

Scope

Layer	Files
Compiler	lib/Compiler.php — persist property Type on TYPE_DECLARE_PROPERTY
VM	lib/VM.php — TYPE_PROPERTY_ASSIGN / ctor promotion paths
Union / readonly	Reuse lib/VM/TypeCheck.php; instance readonly distinct from readonly class (#1360)
JIT/AOT	After VM PHPT — mirror checks in lib/JIT/, lib/AOT/

Done when

• Invalid assign in repro throws TypeError on VM (message mentions property type)
• int|string union accepts either type, rejects others
• Instance readonly rejects second assign outside __construct
• ./script/ci-fast.sh --filter typed_property green (valid + invalid PHPTs)
• README / capability-syntax notes enforcement (not just declaration)

Out of scope (separate issues)

• extends / interface property inheritance (Compiler: Class inheritance (extends) and interfaces #101)
• Full JIT typed stores before VM green

Label: implementation-ready

[PurHur]

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