This reverts commit bb43a3822e.
After thinking about this a bit more, this is now going to be
a complete solution for the "readonly properties" case, for example:
unset($foo->readOnly->bar);
should also be legal and
$foo->readOnly['bar'] = 42;
should also be legal if $foo->readOnly is not an array but an
ArrayAccess object.
I think it may be better to distinguish better on the BP_VAR flag
level. Reverting for now.
$a->b->c = 'd';
is now compiled the same way as
$b = $a->b;
$b->c = 'd';
That is, we perform a read fetch on $a->b, rather than a write
fetch.
This is possible, because PHP 8 removed auto-vivification support
for objects, so $a->b->c = 'd' may no longer modify $a->b proper
(i.e. not counting interior mutability of the object).
Closes GH-5250.
This removes object auto-vivification support.
This also means that we can remove the corresponding special
handling for typed properites: We no longer need to check that a
property is convertible to stdClass if such a conversion might
take place indirectly due to a nested property write.
Additionally OBJ_W style operations now no longer modify the
object operand, and as such we no longer need to treat op1 as a
def in SSA form.
The next step would be to actually compile the whole LHS of OBJ_W
operations in R rather than W mode, but that causes issues with
SimpleXML, whose object handlers depend on the current compilation
structure.
Part of https://wiki.php.net/rfc/engine_warnings.
