Language: list destructuring from null — target variables must remain unset (zend_execute.c parity) #4325

Category

language

Problem

When the RHS of list destructuring is null (or other non-array/non-iterable scalars), Zend does not assign the list slots — variables stay unset (null on read). This compiler may still run ArrayDimFetch with literal keys 0, 1, … against a null/scalar container, producing notices or wrong values.

Related but distinct:

• Language: list() destructuring — arrays with string keys must throw TypeError (Zend VM parity) #4298 / Language: list destructuring from string — must not treat string as packed list (zend_execute.c parity) #4308 — string-key arrays and string RHS
• Language: array destructuring with keys (["a" => $x]) #1234 — keyed destructuring ['a' => $x]

php-src reference

• php/php-src Zend/zend_execute.c — list assignment on non-array types
• php/php-src Zend/zend_operators.c — destructuring source type checks

Repro (today)

<?php
[$a, $b] = null;
echo "a=", var_export($a, true), " b=", var_export($b, true), "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php -r "
[\$a,\$b]=null;
echo \"a=\",var_export(\$a,true),\" b=\",var_export(\$b,true),\"\\n\";
"'

Also verify list($x) = false; and [$x] = 0; match Zend (no assignment).

Scope

Done when

• All three repros (null, false, 0) match Zend unset/null output on VM
• JIT/AOT same behavior without VM fallback
• ./script/ci-fast.sh --filter list_destructure_null green

Links

• Language: list destructuring from string — must not treat string as packed list (zend_execute.c parity) #4308 string RHS · Language: list() destructuring — arrays with string keys must throw TypeError (Zend VM parity) #4298 string keys · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492