Language: keyed list destructure Undefined array key Warning cites previous line — Zend list site (zend_vm_def.h)

[PurHur]

Category

Language · php-src-strict / list destructure warning line

Problem

Keyed list / short-array destructure of a missing key correctly emits Undefined array key and assigns null, but the warning line is the previous statement, not the destructure. Positional [$a, $b] = [1] already cites the list line (parity OK).

Probed 2026-08-18 @ aa2e5e8b62 — Zend 8.2.32 vs php bin/vm.php / php bin/jit.php.

Repro	Zend 8.2.32	VM / JIT
[$a, $b] = [1]; (file line 3)	Warning key 1 line 3	line 3 (parity OK)
['x' => $c] = ['y' => 1]; (file line 5)	Warning key "x" line 5	Warning key "x" line 4 (the echo above)

php-src reference

• php/php-src Zend/zend_vm_def.h — ZEND_FETCH_LIST_R
• php/php-src Zend/zend_execute.c — zend_undefined_index uses current opline

PHP implementation target

• lib/Compiler.php — list/keyed-destructure fetch opcodes must keep the destructure source line (not the previous stmt)
• lib/VM.php / lib/VM/ErrorReporter.php — undefinedArrayKey already has the right text; pass the list site
• JIT: same lineno on the fetch
• No new runtime/*.c

Repro

./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/maintainer_gap_list_undef_key_line.php'
./script/docker-exec.sh -- bash -lc 'php test/repro/maintainer_gap_list_undef_key_line.php'

Done when

• VM warning for key "x" cites line 5 of the repro (matches Zend); key 1 stays line 3
• JIT/AOT same (or documented skip with reason)
• Compliance .phpt under test/compliance/cases/language/
• php-src-strict; no php-compiler-strict shortcut

[PurHur]

claim: worker-lane-c — starting this run

[PurHur]

Merged via #32024.

Fix: assignSourceMetadata() on ArrayDimFetch lowering so Undefined array key warnings cite the list destruct fetch opline (line 5 in repro) instead of walking back to the preceding echo (line 4).

Verified:

• php bin/vm.php test/repro/maintainer_gap_list_undef_key_line.php — key "x" warning line 5
• php bin/jit.php same repro — line 5
• ListDestructUndefKeyLine31994VMTest + ListDestructUndefKeyLine31994JITTest — OK