Fix GH-9285 Traits cannot be used in readonly classes

Author: kocsismate

NEWS

@@ -7,6 +7,8 @@ PHP                                                                        NEWS
     (Tim Starling)
   . Fixed bug GH-9227 (Trailing dots and spaces in filenames are ignored).
     (cmb)
+  . Fixed bug GH-9285 (Traits cannot be used in readonly classes).
+    (kocsismate)
 
 - Streams:
   . Fixed bug GH-9316 ($http_response_header is wrong for long status line).

Zend/tests/readonly_classes/gh9285_error.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Bug GH-9285: PHP 8.2 readonly classes allow inheriting mutable properties from traits - error
+--FILE--
+<?php
+
+trait T {
+    public $prop;
+}
+
+readonly class C {
+    use T;
+}
+
+?>
+--EXPECTF--
+Fatal error: Readonly class C cannot use trait with a non-readonly property T::$prop in %s on line %d

Zend/tests/readonly_classes/gh9285_success.phpt

@@ -0,0 +1,24 @@
+--TEST--
+Bug GH-9285: PHP 8.2 readonly classes allow inheriting mutable properties from traits - success
+--FILE--
+<?php
+
+trait T {
+    public readonly int $prop;
+}
+
+readonly class C {
+    use T;
+
+    public function __construct()
+    {
+        $this->prop = 1;
+    }
+}
+
+$c = new C();
+var_dump($c->prop);
+
+?>
+--EXPECT--
+int(1)

Zend/zend_inheritance.c

@@ -2368,7 +2368,7 @@ static void zend_do_traits_property_binding(zend_class_entry *ce, zend_class_ent
 
 					if (!is_compatible) {
 						zend_error_noreturn(E_COMPILE_ERROR,
-							   "%s and %s define the same property ($%s) in the composition of %s. However, the definition differs and is considered incompatible. Class was composed",
+								"%s and %s define the same property ($%s) in the composition of %s. However, the definition differs and is considered incompatible. Class was composed",
 								ZSTR_VAL(find_first_property_definition(ce, traits, i, prop_name, colliding_prop->ce)->name),
 								ZSTR_VAL(property_info->ce->name),
 								ZSTR_VAL(prop_name),
@@ -2378,6 +2378,15 @@ static void zend_do_traits_property_binding(zend_class_entry *ce, zend_class_ent
 				}
 			}
 
+			if ((ce->ce_flags & ZEND_ACC_READONLY_CLASS) && !(property_info->flags & ZEND_ACC_READONLY)) {
+				zend_error_noreturn(E_COMPILE_ERROR,
+					"Readonly class %s cannot use trait with a non-readonly property %s::$%s",
+					ZSTR_VAL(ce->name),
+					ZSTR_VAL(property_info->ce->name),
+					ZSTR_VAL(prop_name)
+				);
+			}
+
 			/* property not found, so lets add it */
 			if (flags & ZEND_ACC_STATIC) {
 				prop_value = &traits[i]->default_static_members_table[property_info->offset];