[PurHur]

Summary

• Fix VM call-arg lowering when php-cfg hoists a trailing literal ConstFetch between nested FuncCall nodes (e.g. var_export(get_debug_type(null), true)).
• Add isNestedCallArgProducerSeparatedByConsumerLiteralPreludes() so inner FUNCCALL_EXEC_RETURN slots wire to outer TYPE_ARG_SEND instead of dead temps.
• Extends Regression: var_export($nested_builtin, true) returns NULL — inline call arg not evaluated (ext/standard/var.c) #10373 (array/string builtins) to scalar-return builtins: get_debug_type, gettype, json_encode, get_class.

Closes #10495

php-src / PHP-in-PHP

Reference	PHP implementation
Zend/zend_execute.c nested call arg evaluation	lib/Compiler.php — inline call-arg producer matching

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php -r "
echo var_export(get_debug_type(null), true), \"\\n\";
echo var_export(gettype(null), true), \"\\n\";
echo var_export(json_encode(null), true), \"\\n\";
echo var_export(get_class(new stdClass()), true), \"\\n\";
"
./vendor/bin/phpunit --filter testVarExportNestedScalarBuiltinUsesFuncCallProducerSlot test/unit/InlineCallArgProducerSlotTest.php
./vendor/bin/phpunit --filter nested_string_builtin_arg test/compliance/
'

Results (2026-06-22):

• VM inline repro prints 'null', 'NULL', 'null', 'stdClass' (was NULL for nested calls)
• InlineCallArgProducerSlotTest::testVarExportNestedScalarBuiltinUsesFuncCallProducerSlot — OK
• nested_string_builtin_arg.phpt compliance — OK (VM + JIT matrix)

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