Language: parent:: and static:: resolution in extends chain (#101 phase 1b)

[PurHur]

Category

language

Problem

#101 tracks single-parent extends and empty implements v1. Real PHP controllers and future self-host code also use:

class Child extends Parent_ {
    public function run(): void {
        parent::greet();
        static::factory();
    }
}

Without parent:: / static:: lowering, even a minimal extends landing forces duplicated method bodies.

php-src reference

• Zend/zend_compile.c — zend_compile_static_call, parent / static class name resolution
• Zend/zend_inheritance.c — parent method lookup, zend_get_parent_ce
• Zend/zend_class.c — late static binding (Z_CE_SCOPE, called scope)
• Zend/zend_vm_execute.h — ZEND_INIT_FCALL / static call opcodes with LSB

Repro (today)

<?php
class Parent_ {
    public static function tag(): string { return 'P'; }
    public function greet(): string { return 'hi'; }
}
class Child extends Parent_ {
    public function run(): string {
        return parent::greet() . static::tag();
    }
}
echo (new Child())->run();

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

This compiler: compile error or wrong dispatch on parent:: / static:: until #101 + this issue land.

Goal

After #101 phase 1a (extends + method lookup chain on VM):

1. Compile parent::method() to parent vtable dispatch
2. Compile static::method() to late-static binding (class of call site, not instance)
3. Reject parent:: on non-methods with clear compile error

Defer: parent::class, parent::$prop, traits (#144).

Scope (this repo)

Layer	Files	Notes
Compiler	lib/Compiler.php	Expr_StaticCall with parent / static class
VM	lib/VM.php	Parent chain walk; LSB uses declaring class
JIT	lib/JIT.php	Defer — VM PHPT first
Tests	test/compliance/cases/classes/	parent_method_call.phpt, static_late_binding.phpt

Done when

• Repro prints hip on VM matching Zend
• ./script/ci-fast.sh --filter 'parent_|static_late' green
• JIT follow-up tracked under Language: late static binding (static::method()) #1231 if VM-only in v1

Dependencies

• Compiler: Class inheritance (extends) and interfaces #101 — extends metadata + dispatch (blocks this)
• Language: Class methods and property access in JIT #58, Language: Visibility, constructors, and destructors #145 — JIT class calls (follow-up)
• Not required for 🌐 North Star 1: Web-capable PHP application (living tracker) #1044 close (MiniWebApp has no parent::)

Links

• Compiler: Class inheritance (extends) and interfaces #101 · Language: Traits, abstract classes, and interfaces #144 · Language: late static binding (static::method()) #1231 · ROADMAP 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78 · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 self-host

[PurHur]

PR #1873 advances phase 1b:

• Done: parent:: on static parent methods (new parent_method_call.phpt), CFG temp slot reuse, return <call>() slot alignment in the compiler.
• Still open on VM: late_static_binding.phpt and any return static::tag() / return G::t() path — nested call results do not propagate to the caller’s returnVar (empty stdout). Needs a dedicated VM fix before the full Language: parent:: and static:: resolution in extends chain (#101 phase 1b) #1858 acceptance matrix is green.

Verified locally in Docker: phpunit --filter parent_method_call passes.

[PurHur]

PM / PR #1873 (batch 79):

PR open for phase 1b (parent:: static methods + return-call slot reuse). VM compliance filter for parent_method_call reported green.

Not done for full close: late_static_binding.phpt empty output — nested return static::…() (#1231). Recommend merge PR as partial land or keep issue open with checklist split.

ROADMAP: #78 batch 79.

[PurHur]

Implementation hints (batch 80)

Active PR: #1873 — VM compliance ✅ for basic parent:: / static:: dispatch; still open: late_static_binding return chain (child of #1231).

Step	File / test	Notes
1	lib/Compiler.php	Lower Expr_StaticCall when class is parent → resolved parent FQCN from extends table
2	lib/VM.php	Walk parent vtable; LSB uses called class for static::
3	test/compliance/cases/classes/parent_static_*.phpt	Add before JIT
4	lib/JIT.php	Defer until VM PHPT green; mirror #58 method dispatch
5	Return propagation	Fix slot reuse when callee returns into outer expression (#1873 tail)

Unblock order: #101 extends metadata → this issue → #1231 full LSB → JIT (#58).

Verify:

./script/ci-fast.sh --filter parent
docker run --rm -v "$(pwd):/compiler" -w /compiler php-compiler:22.04-dev \
  vendor/bin/phpunit --filter ParentStatic

Not required for #1044 / MiniWebApp (no parent:: in tree).