Language: #[\Override] on trait method alias must be compile-time fatal (zend_compile.c)

[PurHur]

Category

language

Problem

#[\Override] on a method that only overrides a trait-provided method (no parent class method in the inheritance chain) must fail at compile time in php-src. Partial coverage exists: trait alias + Override on child is already rejected; direct trait method redefinition in the same class still compiles.

Verified 2026-06-05 on bin/vm.php:

Scenario	Zend 8.3+	This compiler
Class use T; #[\Override] public function f() redefines trait method	Compile-time fatal	Compiles silently ❌
Child overrides trait alias T::f as g with #[\Override]	Compile-time fatal	Already rejected ✅

php-src reference

• php/php-src Zend/zend_compile.c — ZEND_ACC_OVERRIDE validation walks the parent class chain; trait-provided methods are not valid override targets (PHP 8.3+)
• php/php-src Zend/zend_attributes.c — Override attribute handling

Repro

Still broken (direct trait override):

<?php
trait T { public function f(): void {} }
class C {
    use T;
    #[\Override]
    public function f(): void { echo "class\n"; }
}

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
cat > /tmp/override_trait_direct.php <<'"'"'PHPEOF'"'"'
<?php
trait T { public function f(): void {} }
class C {
    use T;
    #[\Override]
    public function f(): void { echo "class\n"; }
}
PHPEOF
php bin/vm.php /tmp/override_trait_direct.php   # compiles — should fatal at compile time
'

Zend expected:

Fatal error: C::f() has #[\Override] attribute, but no matching parent method exists

Already fixed (alias case — regression guard):

trait T { public function f(): void {} }
class C { use T { f as g; } }
class D extends C {
    #[\Override]
    public function g(): void {}
}

Scope

Path	Work
lib/Compiler/OverrideValidator.php (or lib/Compiler.php)	Treat trait-origin methods as non-parent for Override target walk
test/compliance/cases/language/	PHPT compile-fail fixtures

Done when

• Direct trait override repro fails at compile time with Zend message (VM never runs echo)
• Alias regression repro still fails compile (no regression)
• test/compliance/cases/language/override_trait_method.phpt added (EXPECT compile failure)
• JIT/AOT inherit compile-time check (no attribute bypass)

Strictness

php-src-strict — compile-time parity with Zend attribute semantics.

Related

• Language: overriding final parent methods must be compile-time fatal (zend_compile.c parity) #4263 (final method override) · Language: #[\DelayedTargetValidation] attribute — validate attribute targets at compile time (PHP 8.4, zend_attributes.c) #5124 (DelayedTargetValidation) · Language: #[\Override] on trait method alias must be compile-time fatal (zend_compile.c) #6440 · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: worker-lane-C — starting this run

[PurHur]

Merged via #6477

Fix: Trait-composed methods are no longer valid #[\Override] targets — only parent class and interface chain methods count (php-src zend_compile.c).

Verification:

• vendor/bin/phpunit --filter OverrideAttributeTest — OK (4 tests)
• vendor/bin/phpunit --filter "override_trait|override_trait_method|override_trait_alias" — OK (6 tests, VM + JIT)
• Direct trait override repro exits 255 with C::f() has #[\Override] attribute, but no matching parent method exists