Inconsistent behaviour with AppendIterator and empty generators

Description

I've encountered inconsistent behaviour in the handling of empty generators with AppendIterator. Please can you confirm whether this is a bug or some weird expected behaviour.

Scenario 1

When iterating over a generator that yields nothing, foreach has no items to iterate over so var_dump isn't called, as expected.

<?php

function yieldEmpty()
{
    yield from [];
}

foreach (yieldEmpty() as $item) {
    var_dump($item);
}

Scenario 2

When attaching a generator yielding items and a generator yielding nothing and attaching both to an AppendIterator, foreach iterates over the items from the former and the three values are output, as expected.

<?php

function yieldRows()
{
    yield from ['one', 'two', 'three'];
}

function yieldEmpty()
{
    yield from [];
}

$iterator = new AppendIterator();
$iterator->append(yieldRows());
$iterator->append(yieldEmpty());

foreach ($iterator as $item) {
    var_dump($item);
}

Outputs (as expected):

string(3) "one"
string(3) "two"
string(5) "three"

Scenario 3

When attaching ONLY a generator yielding nothing and attaching it to an AppendIterator, foreach unexpectedly fails with an exception.

<?php

function yieldEmpty()
{
    yield from [];
}

$iterator = new AppendIterator();
$iterator->append(yieldEmpty());

foreach ($iterator as $item) {
    var_dump($item);
}

Expected output (following on from scenario 1 and 2):

string(3) "one"
string(3) "two"
string(5) "three"

Actual output:

PHP Fatal error:  Uncaught Exception: Cannot traverse an already closed generator in /Users/richard.coupland/test3.php:11
Stack trace:
#0 /Users/richard.coupland/test3.php(11): AppendIterator->rewind()
#1 {main}
  thrown in /Users/richard.coupland/test3.php on line 11

Fatal error: Uncaught Exception: Cannot traverse an already closed generator in /Users/richard.coupland/test3.php:11
Stack trace:
#0 /Users/richard.coupland/test3.php(11): AppendIterator->rewind()
#1 {main}
  thrown in /Users/richard.coupland/test3.php on line 11

PHP Version

8.2.7

Operating System

No response

Bắt đầu bằng cách tái hiện ba kịch bản AppendIterator với các generator yieldEmpty và yieldRows trên PHP 8.2.7, tập trung vào lỗi xảy ra trong foreach và AppendIterator->rewind(). Xác định xem hành vi khác biệt là có chủ đích hay là một bug, sau đó thêm hoặc cập nhật phạm vi kiểm thử hồi quy để trường hợp generator rỗng có hành vi được xác định và vượt qua kiểm thử.