Throw Error when writing property of non-object

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.

Author: nikic

UPGRADING

@@ -86,6 +86,11 @@ PHP 8.0 UPGRADE NOTES
         function test(?int $arg = CONST_RESOLVING_TO_NULL) {}
         // Or
         function test(int $arg = null) {}
+  . Attempting to write to a property of a non-object will now result in an
+    Error exception. Previously this resulted in a warning and either converted
+    the value into an object (if it was null, false or an empty string) or
+    ignored the write altogether (in all other cases).
+    RFC: Part of https://wiki.php.net/rfc/engine_warnings
 
 - COM:
   . Removed the ability to import case-insensitive constants from type

Zend/tests/026.phpt

@@ -13,13 +13,16 @@ $test = new foo;
 $test->a()->a;
 print "ok\n";
 
-$test->a()->a = 1;
+try {
+    $test->a()->a = 1;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
 print "ok\n";
 
 ?>
 --EXPECTF--
 Notice: Trying to get property 'a' of non-object in %s on line %d
 ok
-
-Warning: Creating default object from empty value in %s on line %d
+Attempt to assign property 'a' of non-object
 ok

Zend/tests/033.phpt

@@ -9,11 +9,19 @@ echo $arr[1][2][3][4][5];
 
 $arr[1][2][3][4][5]->foo;
 
-$arr[1][2][3][4][5]->foo = 1;
+try {
+    $arr[1][2][3][4][5]->foo = 1;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
 
 $arr[][] = 2;
 
-$arr[][]->bar = 2;
+try {
+    $arr[][]->bar = 2;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
 
 ?>
 --EXPECTF--
@@ -54,7 +62,5 @@ Notice: Trying to access array offset on value of type null in %s on line %d
 Notice: Trying to access array offset on value of type null in %s on line %d
 
 Notice: Trying to get property 'foo' of non-object in %s on line %d
-
-Warning: Creating default object from empty value in %s on line %d
-
-Warning: Creating default object from empty value in %s on line %d
+Attempt to assign property 'foo' of non-object
+Attempt to assign property 'bar' of non-object

Zend/tests/assign_dim_obj_null_return.phpt

@@ -17,8 +17,16 @@ function test() {
     var_dump($array[new stdClass] += 123);
     var_dump($true[123] += 456);
 
-    var_dump($true->foo = 123);
-    var_dump($true->foo += 123);
+    try {
+        var_dump($true->foo = 123);
+    } catch (Error $e) {
+        echo $e->getMessage(), "\n";
+    }
+    try {
+        var_dump($true->foo += 123);
+    } catch (Error $e) {
+        echo $e->getMessage(), "\n";
+    }
 }
 
 test();
@@ -48,9 +56,5 @@ NULL
 
 Warning: Cannot use a scalar value as an array in %s on line %d
 NULL
-
-Warning: Attempt to assign property 'foo' of non-object in %s on line %d
-NULL
-
-Warning: Attempt to assign property 'foo' of non-object in %s on line %d
-NULL
+Attempt to assign property 'foo' of non-object
+Attempt to assign property 'foo' of non-object

Zend/tests/assign_ref_error_var_handling.phpt

@@ -7,19 +7,19 @@ function val() {
     return 42;
 }
 
-$str = "foo";
 $var = 24;
-var_dump($str->foo =& $var);
-var_dump($str);
-var_dump($str->foo =& val());
-var_dump($str);
+$arr = [PHP_INT_MAX => "foo"];
+var_dump($arr[] =& $var);
+var_dump(count($arr));
+var_dump($arr[] =& val());
+var_dump(count($arr));
 
 ?>
 --EXPECTF--
-Warning: Attempt to modify property 'foo' of non-object in %s on line %d
+Warning: Cannot add element to the array as the next element is already occupied in %s on line %d
 NULL
-string(3) "foo"
+int(1)
 
-Warning: Attempt to modify property 'foo' of non-object in %s on line %d
+Warning: Cannot add element to the array as the next element is already occupied in %s on line %d
 NULL
-string(3) "foo"
+int(1)

Zend/tests/bug36303.phpt

@@ -2,13 +2,13 @@
 Bug #36303 (foreach on error_zval produces segfault)
 --FILE--
 <?php
-$x="test";
-foreach($x->a->b as &$v) {
+$x=[PHP_INT_MAX=>"test"];
+foreach ($x[] as &$v) {
 }
 echo "ok\n";
 ?>
 --EXPECTF--
-Warning: Attempt to modify property 'a' of non-object in %sbug36303.php on line 3
+Warning: Cannot add element to the array as the next element is already occupied in %s on line %d
 
-Warning: Invalid argument supplied for foreach() in %sbug36303.php on line 3
+Warning: Invalid argument supplied for foreach() in %s on line %d
 ok

Zend/tests/bug41075.phpt

@@ -8,42 +8,62 @@ $a = true;
 echo "--> read access: ";
 echo $a->p;
 
-echo "\n--> direct assignment: ";
-$a->p = $s;
+echo "\n--> direct assignment:\n";
+try {
+    $a->p = $s;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
 
-echo "\n--> increment: ";
-$a->p++;
+echo "\n--> increment:\n";
+try {
+    $a->p++;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
 
-echo "\n--> reference assignment:";
-$a->p =& $s;
+echo "\n--> reference assignment:\n";
+try {
+    $a->p =& $s;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
 
-echo "\n--> reference assignment:";
-$s =& $a->p;
+echo "\n--> reference assignment:\n";
+try {
+    $s =& $a->p;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
 
-echo "\n--> indexed assignment:";
-$a->p[0] = $s;
+echo "\n--> indexed assignment:\n";
+try {
+    $a->p[0] = $s;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
 
 echo "\n--> Confirm assignments have had no impact:\n";
 var_dump($a);
 ?>
 --EXPECTF--
 --> read access: 
-Notice: Trying to get property 'p' of non-object in %sbug44660.php on line 6
+Notice: Trying to get property 'p' of non-object in %s on line %d
 
---> direct assignment: 
-Warning: Attempt to assign property 'p' of non-object in %sbug44660.php on line 9
+--> direct assignment:
+Attempt to assign property 'p' of non-object
 
---> increment: 
-Warning: Attempt to increment/decrement property 'p' of non-object in %sbug44660.php on line 12
+--> increment:
+Attempt to increment/decrement property 'p' of non-object
 
 --> reference assignment:
-Warning: Attempt to modify property 'p' of non-object in %sbug44660.php on line 15
+Attempt to modify property 'p' of non-object
 
 --> reference assignment:
-Warning: Attempt to modify property 'p' of non-object in %sbug44660.php on line 18
+Attempt to modify property 'p' of non-object
 
 --> indexed assignment:
-Warning: Attempt to modify property 'p' of non-object in %sbug44660.php on line 21
+Attempt to modify property 'p' of non-object
 
 --> Confirm assignments have had no impact:
 bool(true)