fix(types): list destructuring accepts a union/assoc RHS carrying an array member

[chadmandoo]

What

list() / [$a, $b] = ... destructuring only accepted a plain Array(T) right-hand side and errored otherwise. A common pattern was rejected:

private function mk(int $n): ?array { /* ... */ }

$entry = $this->mk($n);
if ($entry === null) { continue; }
[$key, $value] = $entry;   // $entry types as Union[Array, Void] here

How

In check_list_unpack, accept an AssocArray RHS and a Union that carries an array-like member (Array / AssocArray / Mixed) — both are arrays at runtime in well-typed code. Their elements bind as Mixed (adaptive access), the trust posture PHP applies at runtime.

Test

test_list_unpack_null_narrowed_array_return — destructuring a null-narrowed ?array return in a loop, byte-parity vs PHP 8.5.

🤖 Generated with Claude Code