Language: list destructuring from string — TypeError (#7461)

[PurHur]

Summary

• TYPE_LIST_UNPACK_CHECK in lib/VM.php throws TypeError: Cannot use string as array when list/[] destructuring RHS is a string (Language: list/array destructuring from string — must TypeError not null slots (zend_execute.c) #7461).
• lib/JIT/ListUnpackHelper.php mirrors the guard for compile-time and runtime string operands (LLVM TypeErrorRaise path).
• Null/int/bool/float RHS still leave targets unset per Language: list destructuring from null — target variables must remain unset (zend_execute.c parity) #4325.

php-src reference

Zend/zend_execute.c — zend_fetch_dimension_address_read() is_list branch (PHP 8.4+ warns; issue requires catchable TypeError for string RHS).

Verification

./script/docker-exec.sh -- php bin/vm.php test/repro-maintainer/list_destructure_string.php
# TypeError: Cannot use string as array

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php vendor/bin/phpunit --filter list_destructure_string'
# OK (2 tests, 2 assertions)

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php vendor/bin/phpunit test/unit/ListDestructStringTest.php test/unit/ListDestructNullTest.php'
# OK (2 tests) — string TypeError; null/false/int still NULL

Closes #7461

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