[RFC] Allow hooks for backed readonly properties

NEWS

@@ -53,6 +53,7 @@ PHP                                                                        NEWS
     evaluation) and GH-18464 (Recursion protection for deprecation constants not
     released on bailout). (DanielEScherzer and ilutov)
   . Fixed AST printing for immediately invoked Closure. (Dmitrii Derepko)
+  . Property hooks are now allowed on backed readonly properties. (Crell, NickSdot and iluuu1994)
 
 - Curl:
   . Added curl_multi_get_handles(). (timwolla)

UPGRADING

@@ -144,6 +144,8 @@ PHP 8.5 UPGRADE NOTES
     RFC: https://wiki.php.net/rfc/attributes-on-constants
   . The #[\Deprecated] attribute can now be used on constants.
     RFC: https://wiki.php.net/rfc/attributes-on-constants
+  . Property hooks are now allowed on backed readonly properties.
+    RFC: https://wiki.php.net/rfc/readonly_hooks
 
 - Curl:
   . Added support for share handles that are persisted across multiple PHP

Zend/tests/property_hooks/readonly_class_property_backed.phpt

@@ -0,0 +1,41 @@
+--TEST--
+Backed property in readonly class may have hooks
+--FILE--
+<?php
+
+// readonly class
+readonly class Test {
+    public int $prop {
+        get => $this->prop;
+        set => $value;
+    }
+
+    public function __construct(int $v) {
+        $this->prop = $v;
+    }
+
+    public function set($v)
+    {
+         $this->prop = $v;
+    }
+}
+
+$t = new Test(42);
+var_dump($t->prop);
+try {
+    $t->set(43);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+try {
+    $t->prop = 43;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+var_dump($t->prop);
+?>
+--EXPECT--
+int(42)
+Cannot modify readonly property Test::$prop
+Cannot modify protected(set) readonly property Test::$prop from global scope
+int(42)

Zend/tests/property_hooks/readonly_class_property_backed_inheritance_1.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Non-readonly class cannot extend readonly class
+--FILE--
+<?php
+
+readonly class ParentClass {
+    public int $prop;
+}
+
+class Test extends ParentClass {
+    public function __construct(
+        public int $prop {
+            get => $this->prop;
+            set => $value;
+        }
+    ) {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Non-readonly class Test cannot extend readonly class ParentClass in %s on line %d

Zend/tests/property_hooks/readonly_class_property_backed_inheritance_2.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Readonly class cannot extend non-readonly class
+--FILE--
+<?php
+
+class ParentClass {
+    public int $prop;
+}
+
+readonly class Test extends ParentClass {
+    public function __construct(
+        public int $prop {
+            get => $this->prop;
+            set => $value;
+        }
+    ) {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Readonly class Test cannot extend non-readonly class ParentClass in %s on line %d

Zend/tests/property_hooks/readonly_class_property_backed_promoted.phpt

@@ -0,0 +1,40 @@
+--TEST--
+Backed promoted property in readonly class may have hooks
+--FILE--
+<?php
+
+// readonly class, promoted
+readonly class Test {
+    public function __construct(
+        public int $prop {
+            get => $this->prop;
+            set => $value;
+        }
+    ) {}
+
+    public function set($v)
+    {
+         $this->prop = $v;
+    }
+}
+
+$t = new Test(42);
+var_dump($t->prop);
+try {
+    $t->set(43);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+try {
+    $t->prop = 43;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+var_dump($t->prop);
+?>
+--EXPECT--
+int(42)
+Cannot modify readonly property Test::$prop
+Cannot modify protected(set) readonly property Test::$prop from global scope
+int(42)
+

Zend/tests/property_hooks/readonly_class_property_virtual_promoted.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Virtual promoted property in readonly class cannot have hooks
+--FILE--
+<?php
+
+readonly class Test {
+    public function __construct(
+        public int $prop {
+            get => 42;
+        }
+    ) {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Hooked virtual properties cannot be readonly in %s on line %d

Zend/tests/property_hooks/readonly_property_backed.phpt

@@ -0,0 +1,108 @@
+--TEST--
+Backed readonly property may have hooks
+--FILE--
+<?php
+
+// readonly property
+class Test {
+    public readonly int $prop {
+        get => $this->prop;
+        set => $value;
+    }
+
+    public function __construct(int $v) {
+        $this->prop = $v;
+    }
+
+    public function set($v)
+    {
+         $this->prop = $v;
+    }
+}
+
+$t = new Test(42);
+var_dump($t->prop);
+try {
+    $t->set(43);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+try {
+    $t->prop = 43;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+var_dump($t->prop);
+
+// class readonly
+final readonly class Foo
+{
+    public function __construct(
+        public array $values {
+            set(array $value) => array_map(strtoupper(...), $value);
+        },
+    ) {}
+}
+
+// property readonly
+final class Foo2
+{
+    public function __construct(
+        public readonly array $values {
+            set(array $value) => array_map(strtoupper(...), $value);
+        },
+    ) {}
+}
+
+// redundant readonly
+final readonly class Foo3
+{
+    public function __construct(
+        public readonly array $values {
+            set(array $value) => array_map(strtoupper(...), $value);
+            get => $this->makeNicer($this->values);
+        },
+    ) {}
+
+    public function makeNicer(array $entries): array
+    {
+      return array_map(
+        fn($i, $entry) => $entry . strtoupper(['', 'r', 'st'][$i]), array_keys($entries),
+        $entries
+       );
+    }
+}
+
+\var_dump(new Foo(['yo,', 'you', 'can'])->values);
+\var_dump(new Foo2(['just', 'do', 'things'])->values);
+\var_dump(new Foo3(['nice', 'nice', 'nice'])->values);
+?>
+--EXPECT--
+int(42)
+Cannot modify readonly property Test::$prop
+Cannot modify protected(set) readonly property Test::$prop from global scope
+int(42)
+array(3) {
+  [0]=>
+  string(3) "YO,"
+  [1]=>
+  string(3) "YOU"
+  [2]=>
+  string(3) "CAN"
+}
+array(3) {
+  [0]=>
+  string(4) "JUST"
+  [1]=>
+  string(2) "DO"
+  [2]=>
+  string(6) "THINGS"
+}
+array(3) {
+  [0]=>
+  string(4) "NICE"
+  [1]=>
+  string(5) "NICER"
+  [2]=>
+  string(6) "NICEST"
+}

Zend/tests/property_hooks/readonly_property_backed_inheritance_1.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Backed property cannot redeclare readonly as non-readonly property
+--FILE--
+<?php
+
+class ParentClass {
+    public readonly int $prop;
+}
+
+class Test extends ParentClass {
+    public function __construct(
+        public int $prop {
+            get => $this->prop;
+            set => $value;
+        }
+    ) {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot redeclare readonly property ParentClass::$prop as non-readonly Test::$prop %s on line %d

Zend/tests/property_hooks/readonly_property_backed_inheritance_2.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Backed property cannot redeclare non-readonly as readonly property
+--FILE--
+<?php
+
+class ParentClass {
+    public int $prop;
+}
+
+class Test extends ParentClass {
+    public function __construct(
+        public readonly int $prop {
+            get => $this->prop;
+            set => $value;
+        }
+    ) {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot redeclare non-readonly property ParentClass::$prop as readonly Test::$prop in %s on line %d