Language: list destructuring spread — JIT/AOT TYPE_LIST_SPREAD_ASSIGN (phase 2 of #4835) #4885

Category

language

Problem

PHP 8.1+ list assignment with spread ([$head, ...$tail] = $array) is VM-complete after #4835 (OpCode::TYPE_LIST_SPREAD_ASSIGN in lib/VM.php). lib/JIT.php has no case OpCode::TYPE_LIST_SPREAD_ASSIGN, so bin/jit.php / AOT cannot execute scripts using spread destructuring without VM fallback.

test/compliance/JITTest.php skips list_destructuring_spread.phpt for MCJIT execute.

php-src reference

• php/php-src Zend/zend_compile.c — list assignment with unpack
• php/php-src Zend/zend_execute.c — ZEND_ASSIGN list unpack + remainder merge

Repro — VM (baseline, should already pass)

<?php
$src = [1, 2, 3, 4];
[$a, ...$rest] = $src;
echo $a, ':', implode(',', $rest), "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php repro_list_spread.php'
# Expected: 1:2,3,4

Repro — JIT gap (today)

Same script via JIT:

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
export PHP_COMPILER_LLVM_PATH=/opt/llvm9
export LD_LIBRARY_PATH=/opt/llvm9
php bin/jit.php repro_list_spread.php
'

VM matches Zend; JIT compile/execute fails or diverges until TYPE_LIST_SPREAD_ASSIGN is lowered.

String-key tail guard (VM already enforces):

<?php
try {
    [$a, ...$b] = ['k' => 1, 'x' => 2];
} catch (TypeError $e) {
    echo $e->getMessage(), "\n";
}

Zend: Cannot unpack array with string keys.

Scope (this repo)

Done when

• JIT + AOT execute list_destructuring_spread.phpt without VM fallback
• Spread on non-list array throws TypeError with Zend message
• ./script/ci-fast.sh --filter list_destructuring_spread green (VM + JIT)

Links

• Language: list destructuring with spread — [$a, ...$rest] = $arr (zend_compile.c) #4835 (VM) · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 (self-host)