Fix the issue for access via cache slot as well

Author: nikic

Zend/tests/readonly_props/cache_slot.phpt

@@ -6,13 +6,22 @@ Test interaction with cache slots
 class Test {
     public readonly string $prop;
     public readonly array $prop2;
+    public readonly object $prop3;
     public function setProp(string $prop) {
         $this->prop = $prop;
     }
     public function initAndAppendProp2() {
         $this->prop2 = [];
         $this->prop2[] = 1;
     }
+    public function initProp3() {
+        $this->prop3 = new stdClass;
+        $this->prop3->foo = 1;
+    }
+    public function replaceProp3() {
+        $ref =& $this->prop3;
+        $ref = new stdClass;
+    }
 }
 
 $test = new Test;
@@ -38,6 +47,22 @@ try {
     echo $e->getMessage(), "\n";
 }
 var_dump($test->prop2);
+echo "\n";
+
+$test = new Test;
+$test->initProp3();
+try {
+    $test->replaceProp3();
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+var_dump($test->prop3);
+try {
+    $test->replaceProp3();
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+var_dump($test->prop3);
 
 ?>
 --EXPECT--
@@ -49,3 +74,12 @@ Cannot modify readonly property Test::$prop2
 Cannot modify readonly property Test::$prop2
 array(0) {
 }
+
+object(stdClass)#3 (1) {
+  ["foo"]=>
+  int(1)
+}
+object(stdClass)#3 (1) {
+  ["foo"]=>
+  int(1)
+}

Zend/zend_execute.c

@@ -2840,11 +2840,14 @@ static zend_always_inline void zend_fetch_property_address(zval *result, zval *c
 				ZVAL_INDIRECT(result, ptr);
 				zend_property_info *prop_info = CACHED_PTR_EX(cache_slot + 2);
 				if (prop_info) {
-					if (UNEXPECTED(prop_info->flags & ZEND_ACC_READONLY)
-							&& Z_TYPE_P(ptr) != IS_OBJECT) {
+					if (UNEXPECTED(prop_info->flags & ZEND_ACC_READONLY)) {
 						ZEND_ASSERT(type == BP_VAR_W || type == BP_VAR_RW || type == BP_VAR_UNSET);
-						zend_readonly_property_modification_error(prop_info);
-						ZVAL_ERROR(result);
+						if (Z_TYPE_P(ptr) == IS_OBJECT) {
+							ZVAL_COPY(result, ptr);
+						} else {
+							zend_readonly_property_modification_error(prop_info);
+							ZVAL_ERROR(result);
+						}
 						return;
 					}
 					if (flags) {