Language: builtin Exception/Error/Throwable VM classes (#195)

[PurHur]

Summary

Rebased on master (May 2026): builtin Throwable / Exception / Error hierarchy is already registered via #3371. This PR closes the remaining #195 gap — catch-variable use after merge resume.

• Set inheritUndefinedLocals on the try/catch merge block so enterMatchingCatchHandler can build the post-catch resume frame without Could not resolve argument when the catch body uses $e->getMessage() (etc.).

php-src reference

• Zend/zend_exceptions.c — catch frame setup + merge/finally resume control flow

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php -r '"'"'try { throw new Exception("x"); } catch (Exception $e) { echo $e->getMessage(); }'"'"''
# x

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter ExceptionBuiltin test/unit/ExceptionBuiltinTest.php'
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter exception_throw test/compliance/VMTest.php'
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter TryCatchCompliance test/unit/TryCatchComplianceTest.php'

All green on rebased branch.

Closes #195

[PurHur]

Worker lane A (continuation): Rebased onto latest master and re-verified.

Verification (May 2026)

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php -r '"'"'try { throw new Exception("x"); } catch (Exception $e) { echo $e->getMessage(); }'"'"''
# x

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit test/unit/ExceptionBuiltinTest.php test/compliance/VMTest.php --filter exception'
# OK (7 tests)

Master without this patch still fails with Could not resolve argument on the catch repro.

[PurHur]

Update (cursor-agent-lane-a)

Added Zend getLine() parity for rethrow and deferred throw paths:

• TYPE_NEW arg3 — record creation-site line on Throwable before __construct
• stampThrowLine — skip when line already set (rethrow preserves original)
• resolveCatchVarSlot — register catch var on catch-body block so throw $e works in nested try without a prior read

New compliance: exception_throw_rethrow.phpt, exception_throw_deferred.phpt, exception_throw_code.phpt

Verification

PHP_COMPILER_CI_SINGLE_CONTAINER=0 ./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit test/unit/ExceptionBuiltinTest.php test/unit/TryCatchComplianceTest.php test/compliance/VMTest.php --filter exception_throw'
# OK (24 tests)

php-src: Zend/zend_exceptions.c