Bug #81330 [Com]: Generator does not allow return null with implicit yield
Edit report at https://bugs.php.net/bug.php?id=81330&edit=1
ID: 81330
Comment by: greedy dot ivan at gmail dot com
Reported by: greedy dot ivan at gmail dot com
Summary: Generator does not allow return null with implicit
yield
Status: Not a bug
Type: Bug
Package: *General Issues
Operating System: All
PHP Version: 8.0.9
Assigned To: cmb
Block user comment: N
Private report: N
New Comment:
There are three options here.
1. There is an yield operator inside a function. Parser gets it and allow to return null as a valid
end for generator.
2. There is no yield operator inside a function but there is a return instruction that returns
Generator. This line works fine.
3. The same as 2, but we have a line, that returns null. It will throws Error, because Parser
doesn't allow return an empty Generator such way. It doesn't get, that function return
Generator at all, because there is no yield operation inside function itself.
So, we must use some tricks to return empty Generator in this case, or use yield from
func() instead for return func().
Previous Comments:
------------------------------------------------------------------------
[2021-08-04 11:57:48] cmb@php.net
That type check is done at runtime, not compile time. And there
is no implicit yield.
------------------------------------------------------------------------
[2021-08-04 11:49:42] greedy dot ivan at gmail dot com
It doesn't throw error on all other cases.
It will throw Type error only in case, when yield is implicit and null is returned.
------------------------------------------------------------------------
[2021-08-04 11:39:32] cmb@php.net
If the generator function does not necessarily return a Generator,
you shouldn't declare it as such.
------------------------------------------------------------------------
[2021-08-04 11:29:25] greedy dot ivan at gmail dot com
Description:
------------
If there is not explicit yield instruction in Generator, it will throw TypeError message when null
is returned.
https://3v4l.org/EpIjA
Test script:
---------------
<?php
function foo($flag = false): \Generator
{
if ($flag) {
return null;
}
yield from [1, 2];
}
function bar($flag = false): \Generator
{
if ($flag) {
return null;
}
return internal();
}
function internal(): \Generator
{
yield from [1, 2];
}
foreach (foo() as $v){}
foreach (foo(true) as $v){}
foreach (bar() as $v){}
foreach (bar(true) as $v){}
Expected result:
----------------
No error
Actual result:
--------------
Fatal error: Uncaught TypeError: bar(): Return value must be of type Generator, null returned in
/in/EpIjA:15
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=81330&edit=1
Thread (9 messages)