Disallow the usage of the #[AllowDynamicProperties] attribute

Author: kocsismate

Zend/tests/readonly_classes/readonly_class_dynamic_property_attribute.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Readonly classes cannot apply the #[AllowDynamicProperties] attribute
+--FILE--
+<?php
+
+#[AllowDynamicProperties]
+readonly class Foo
+{
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot apply #[AllowDynamicProperties] to readonly class Foo in %s on line %d

Zend/zend_attributes.c

@@ -71,6 +71,11 @@ static void validate_allow_dynamic_properties(
 	if (scope->ce_flags & ZEND_ACC_INTERFACE) {
 		zend_error_noreturn(E_ERROR, "Cannot apply #[AllowDynamicProperties] to interface");
 	}
+	if (scope->ce_flags & ZEND_ACC_READONLY_CLASS) {
+		zend_error_noreturn(E_ERROR, "Cannot apply #[AllowDynamicProperties] to readonly class %s",
+			ZSTR_VAL(scope->name)
+		);
+	}
 	scope->ce_flags |= ZEND_ACC_ALLOW_DYNAMIC_PROPERTIES;
 }