Description:
------------
There appears to be inconsistent behaviour when returning generators.

Given the function `foo()` returns a generator, when you consume that generator in a new function which also returns a generator, you would expect `return foo()` to have the same behaviour as looping over the values of `foo()` and performing a `yield` on each value; however this doesn't appear to be the case if the function you are consuming `foo()` contains other yield statements.

It looks like PHP is getting confused by having both `yield` statements, and `return $generator` statements, in the same function body.

This appears to affect all PHP versions tested which support generators

POC (code below): https://3v4l.org/e86mK

Test script:
---------------
<?php

function generator() {
    foreach ([1, 2, 3, 4, 5] as $i) {
        yield $i;
    }
}

function A(): \Generator {
    return generator();
}

function B(): \Generator {
    if (false) {
        yield 7;
        return;
    }
    return generator();
}

function C(): \Generator {
    if (false) {
        yield 7;
        return;
    }
    foreach (generator() as $i) {
        yield $i;
    }
}

echo "-A\n";
foreach (A() as $i) {
    echo "{$i}\n";
}

echo "-B\n";
foreach (B() as $i) {
    echo "{$i}\n";
}

echo "-C\n";
foreach (C() as $i) {
    echo "{$i}\n";
}

echo "Done\n";


Expected result:
----------------
-A
1
2
3
4
5
-B
1
2
3
4
5
-C
1
2
3
4
5
Done

Actual result:
--------------
-A
1
2
3
4
5
-B
-C
1
2
3
4
5
Done