Stdlib: array_first()/array_last() on enum-keyed arrays — must TypeError at access not return values (ext/standard/array.c) #10003

Category

stdlib · php-src-strict · enum preservation

Problem

Zend rejects enum case array keys at array creation (TypeError: Illegal offset type). This compiler coerces enum cases to backing scalars when building arrays, so array_first() / array_last() silently return element values instead of failing:

enum E: string { case A = 'a'; }
$a = [E::A => 1];   // Zend: TypeError; VM: coerces key to "a"
array_first($a);    // VM: int(1) — masks #9512 root cause at use site

Related umbrella #9512 (literal keys) — this issue tracks first/last element builtins once illegal arrays exist or as guard when coercion remains.

php-src reference

• php/php-src ext/standard/array.c — array_first, array_last
• php/php-src Zend/zend_hash.c — illegal offset type on enum keys

Repro

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php -r "enum E: string { case A = \"a\"; } try { \$a = [E::A => 1]; array_first(\$a); } catch (Throwable \$e) { echo get_class(\$e), \"\\n\"; }"
php bin/vm.php -r "enum E: string { case A = \"a\"; } \$a = [E::A => 1]; var_dump(array_first(\$a));"
'

Scope (PHP-in-PHP)

Prefer fixing #9512 coercion first; keep this issue as compliance guard + PHPT.

Done when (php-src-strict)

• [E::A => 1] throws TypeError: Illegal offset type on VM (ideal: Language: array literal enum case keys coerce to backing scalar — must TypeError (Zend/zend_hash.c) #9512)
• If coercion temporarily remains, array_first/array_last throw rather than return values for enum-keyed tables
• ./script/ci-fast.sh --filter array_first_enum_key green

Related

• Language: array literal enum case keys coerce to backing scalar — must TypeError (Zend/zend_hash.c) #9512 literal enum keys · Stdlib: array_first()/array_last() — enum case elements materialize backing scalars (ext/standard/array.c) #8987 element scalarization · Stdlib: array_keys()/array_key_first()/array_key_last() on enum-case keyed arrays — TypeError Illegal offset type (ext/standard/array.c) #9871 array_key_first · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492