Language: enum implements interface — parse + VM dispatch (Zend zend_enum.c parity)

[PurHur]

Category

language

Problem

PHP 8.1+ allows enums to implement interfaces (enum Foo: string implements Bar { ... }). This compiler crashes during php-cfg parse when implements is present on an enum:

TypeError: PHPCfg\Op\Stmt\Enum_::__construct(): Argument #3 ($implements) must be of type array, PHPCfg\Block given

The vendor php-cfg Enum_ opcode and Parser::parseStmt_Enum() do not wire interface lists correctly (similar to class implements handling).

php-src reference

• Zend/zend_enum.c — zend_register_enum, interface implementation on enum entries
• Zend/zend_compile.c — zend_compile_enum implements-clause validation
• ext/reflection/php_reflection.c — ReflectionEnum::implements() metadata

Repro (today)

<?php
interface HasName { public function label(): string; }

enum Status: string implements HasName {
    case Open = 'open';
    case Closed = 'closed';
    public function label(): string { return $this->name; }
}

echo Status::Open->label(), "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php repro.php'
/usr/bin/php repro.php   # Zend: Open

This compiler: fatal in php-cfg Parser.php before VM runs.

Scope (this repo)

Module	Path
php-cfg	vendor patch or fork: PHPCfg/Parser.php parseStmt_Enum() — pass interface name list to Enum_
Compiler	store implements on enum class entry like user classes
VM	instanceof / interface checks on enum instances
Tests	test/compliance/cases/language/enum_implements_interface.phpt

Done when

• Repro compiles and prints Open on VM
• Status::Open instanceof HasName is true
• Enum without implements unchanged (Language: Enum declarations (enum / backed enum) #1356 regression guard)
• Compliance PHPT; row in docs/capabilities-syntax.md

Related

• Language: Enum declarations (enum / backed enum) #1356 — backed enum baseline
• Language: enum methods and non-const enum body elements (self-host subset) #2299 — enum methods (closed)
• Language: enum_from() — BackedEnum::from / tryFrom (PHP 8.1) #3114 — BackedEnum::from() / tryFrom()
• Language: UnitEnum::cases() / BackedEnum::cases() — list enum cases (PHP 8.1, Zend parity) #3308 — UnitEnum::cases()

[PurHur]

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