Language: scalar union types — compile abort Unknown Op\Type\Union_ (regression vs #6850/#6833)

[PurHur]

Category

language · php-src-strict · regression

Problem

Scalar union types (int|string, ?float, DNF arms containing unions) abort compile with:

Unknown Op\Type provided: PHPCfg\Op\Type\Union_

Closed #6850 / #6833 tracked this gap; Docker repro (Jun 2026) shows all union sites fail again — function parameters, return types, promoted properties, and declared instance properties. Intersection types (A&B) still compile.

Self-host and modern PHP sources using unions cannot compile on VM/JIT/AOT.

php-src reference

• php/php-src Zend/zend_compile.c — zend_compile_type() union type lists
• php/php-src Zend/zend_type.c — zend_type bitmask + union arms
• php/php-src Zend/zend_type_check.c — runtime verify

Repro (failure today)

Parameter union:

<?php
function f(int|string $x): void {
    echo $x;
}
f(1);

Declared property union:

<?php
class C {
    public int|string $p;
}
$c = new C();
try {
    var_dump($c->p);
} catch (Error $e) {
    echo $e->getMessage(), "\n";
}

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && ./script/apply-patches.sh
php bin/vm.php test/repro/maintainer_union_uninit.php 2>&1 | head -3
php bin/vm.php /tmp/param_union.php 2>&1 | head -3   # write repro files as above
'

Site	Zend	VM today
function f(int|string $x)	compiles	Unknown Op\Type\Union_ ❌
public int|string $p	compiles	Unknown Op\Type\Union_ ❌
function f(A&B $x)	compiles	compiles ✅

Scope (this repo)

Layer	Path
Compiler	lib/Compiler.php — compileTypeConstrainedVariable, TYPE_DECLARE_PROPERTY, param/return type lowering for Union_
VM	lib/VM/TypeCheck.php — per-arm verify on read/write
JIT/AOT	phase 2 after VM green (lib/JIT/TypeCheck.php, DNF helpers)
Tests	test/compliance/cases/types/scalar_union_param.phpt, scalar_union_property.phpt

PHP-in-PHP: union lowering in lib/; no new runtime/*.c.

Done when

• Parameter and property union repros compile on VM
• Uninitialized union property read throws catchable Error like Zend (not Union_ abort)
• Intersection-only types remain green (no regression)
• ./script/ci-fast.sh --filter scalar_union green

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter scalar_union'

Related

• Language: declared property scalar union types — Unknown Op\Type\Union_ (param unions compile) #6850, Language: scalar union types (int|string) — compile regression Unknown Op\Type\Union_ #6833 (closed — reopen tracking) · Language: Intersection types (A&B) in parameters and properties #1357 intersections · Language: DNF types — union of intersections (PHP 8.2) #3094 DNF · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: worker-lane-B — starting this run

[PurHur]

Merged via #7333

Root cause: partial vendor drift — Type.php lost CfgType\Union_ while Intersection remained; apply-patches.sh skipped repair, so params compiled (TypeReconstructor) but declared int|string properties failed at compile.

Fix: Type.php overlay now inserts missing Union_/Intersection blocks independently; verify_critical_language_patches gates vendor Type.php.

Verification:

./script/docker-exec.sh -- bash -lc './test/repro-maintainer/union_patch_drift_probe.sh'
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter "scalar_union|ScalarUnion|ApplyPatchesTest::testPhpTypesUnionTypeTypeOverlayReappliesAfterPartialVendorDrift|TypeReconstructorDnfTest"'

→ probe restores Union_ and property compile succeeds; 12 tests OK.