Description:
------------
The provided Test Script produces the Expected Result in 7.0.7, but encounters a TypeError in 7.1.0alpha1. The issue seems to have been introduced by the removal of the ZEND_VERIFY_RETURN_TYPE case in this commit: https://github.com/php/php-src/commit/cb3825a8dc551e6a43b4ea3a01dbd0584bf606bb#diff-8f41738bb0ceb7bf7c9882a4b399ab6eL645.

Removing the Generator return type declaration or adding an empty return statement after the final yield seems to function as a workaround, but naturally I'd prefer to change nothing if this break was an unintentional.

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

function foo() : Generator
{
    yield 1;
    yield 2;
    yield 3;
}

foreach (foo() as $bar) {
    echo $bar . "\n";
}

Expected result:
----------------
1
2
3

Actual result:
--------------
1
2
3

Fatal error: Uncaught TypeError: Return value of foo() must be an instance of Generator, none returned in /tmp/foo.php:8
Stack trace:
#0 /tmp/foo.php(10): foo()
#1 {main}
  thrown in /tmp/foo.php on line 8