Bug->Doc #71252 [Opn]: Yield from by reference is not supported

Edit report at https://bugs.php.net/bug.php?id=71252&edit=1

 ID:                 71252
 Updated by:         [email protected]
 Reported by:        [email protected]
-Summary:            yield from ignores yield-by-reference
+Summary:            Yield from by reference is not supported
 Status:             Open
-Type:               Bug
+Type:               Documentation Problem
 Package:            Scripting Engine problem
 PHP Version:        7.0Git-2015-12-30 (Git)
 Block user comment: N
 Private report:     N

 New Comment:

As of PHP 7.0.4 this is forbidden[1].  When looking at the
respective commit message[2] and the now long standing behavior,
it might be best to just document the behavior.

[1] <https://3v4l.org/fZEH0>
[2] <https://github.com/php/php-src/commit/ccc06e252bdf4c54cb2c96dbcab9a2aeb933181c>


Previous Comments:
------------------------------------------------------------------------
[2015-12-30 23:24:07] [email protected]

Description:
------------
When "yield from" was implemented, we did not consider how it interacts with yield-by-reference. Right now it is simply ignored and "yield from" yields all values by-value.

Likely this is not the expected or intended behavior. Instead "yield from" in a by-reference generator should yield array values and values from by-reference generators by-reference. "yield from" should generate an error for iterators (and generators) that do not support by-reference iteration.

Test script:
---------------
<?php
function &gen(array $array) {
    yield from $array;
}

$array = [1, 2, 3];
foreach (gen($array) as &$v) {
    $v += 1;
}
var_dump($array);

Expected result:
----------------
array(3) {
  [0]=>
  int(2)
  [1]=>
  int(3)
  [2]=>
  int(4)
}


Actual result:
--------------
array(3) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
}



------------------------------------------------------------------------



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Edit this bug report at https://bugs.php.net/bug.php?id=71252&edit=1