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Inconsistency between null safe operator and property fetch with null coalesce #8661
Description
Description
Noticed this issue while investigating phpstan/phpstan#7291.
The following code:
https://3v4l.org/bgVKX
<?php
echo $a?->foo;
echo $a?->foo ?? '';
echo isset($a?->foo);
echo $a->foo;
echo $a->foo ?? '';
echo isset($a->foo);Resulted in this output:
Warning: Undefined variable $a in /in/bgVKX on line 3
Warning: Undefined variable $a in /in/bgVKX on line 4
Warning: Undefined variable $a in /in/bgVKX on line 7
Warning: Attempt to read property "foo" on null in /in/bgVKX on line 7
But I expected this output instead:
Warning: Undefined variable $a in /in/bgVKX on line 3
Warning: Undefined variable $a in /in/bgVKX on line 7
Warning: Attempt to read property "foo" on null in /in/bgVKX on line 7
I think line 4 should not report a warning because the undefined var $a is handled by null coalescing operator like in line 8.
I believe it is a bug, because the inconsistency between line 4 and 5 (null coalesce vs isset), line 4 and line 8 (null safe vs non null safe) is hard to expect.
PHP Version
PHP 8.0.1 - 8.1.6
Operating System
No response
Activity
damianwadley commentedon May 31, 2022
Agreed that both line 4's
$a?->foo ?? ''and line 8's$a->foo ?? ''should behave the same.cmb69 commentedon May 31, 2022
I tend to agree, but maybe @iluuu1994 can clarify.
iluuu1994 commentedon May 31, 2022
I agree.
JMP_NULLcurrently always callsZVAL_UNDEFINED_OP1(), even if compiled throughzend_compile_coalesce(). It would make sense to avoid the undefined variable error here. This requires passing the BP type in theJMP_NULLopcode throughextended_value. As extensions might depend on that value, I'm not sure if it makes more sense to only patch for PHP 8.2.Fix phpGH-8661: Nullsafe in coalesce triggers undefined variable warning