Language: list destructuring with spread — [$a, ...$rest] = $arr (zend_compile.c) #4835

Category

language

Problem

PHP supports array destructuring with spread: [$head, ...$tail] = $array (and keyed variants). Zend compiles this in zend_compile.c by assigning sequential elements then merging the remainder.

This compiler’s php-cfg fork (vendor/ircmaxell/php-cfg/lib/PHPCfg/Parser.php::parseListAssignment) walks list items but ignores $item->unpack, so spread arms are treated like ordinary numeric slots — wrong variables receive values or compile fails.

Array-literal spread ([...$a]) works via TYPE_ARRAY_SPREAD; list-assign spread is a separate lowering path.

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 runtime
• Grammar: zend_language_parser.y — array_element with T_ELLIPSIS

Repro (failure today)

<?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 repro.php
php bin/vm.php repro.php 2>&1
'

Keyed spread (stretch goal in same issue or follow-up):

['x' => $x, ...$others] = ['x' => 1, 'y' => 2];

Scope (this repo)

Done when

• Packed-list repro prints 1:2,3,4 on VM matching Zend
• By-ref spread [$a, &$b, ...$c] matches Zend when supported by php-parser
• JIT/AOT: same semantics or documented VM-only v1 with matrix note
• ./script/ci-fast.sh --filter list_destructuring_spread green

Related

• List assign base: Language: list destructuring from string — must not treat string as packed list (zend_execute.c parity) #4308, Language: list destructuring from null — target variables must remain unset (zend_execute.c parity) #4325 (closed) · JIT phase 2: Language: list destructuring JIT/MCJIT execute — phase 2 of #4308 / #4325 (zend_execute.c) #4531
• Array literal spread: Language: Array and argument unpack (...$x) #1361

Links

• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492