Allow promoted readonly property to be reassigned once in constructor

Author: nicolas-grekas

Zend/tests/readonly_props/promoted_readonly_reinit_in_constructor.phpt

@@ -0,0 +1,153 @@
+--TEST--
+Promoted readonly property can be reassigned once in constructor
+--FILE--
+<?php
+
+class Point {
+    public function __construct(
+        public readonly float $x = 0.0,
+        public readonly float $y = 0.0,
+    ) {
+        $this->x = abs($x);
+        $this->y = abs($y);
+    }
+}
+
+$point = new Point();
+var_dump($point->x, $point->y);
+
+$point2 = new Point(-1.0, -2.0);
+var_dump($point2->x, $point2->y);
+
+class FailingPoint {
+    public function __construct(
+        public readonly float $x = 0.0,
+    ) {
+        $this->x = 10.0;  // First reassignment - allowed
+        try {
+            $this->x = 20.0;  // Second reassignment - should fail
+        } catch (Error $e) {
+            echo $e->getMessage(), "\n";
+        }
+    }
+}
+
+$fp = new FailingPoint();
+var_dump($fp->x);
+
+try {
+    $point->x = 100.0;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+class Foo {
+    public function __construct(
+        public readonly ?string $bar = null,
+    ) {
+        $this->bar ??= 'modified in constructor';
+    }
+}
+
+$foo = new Foo();
+var_dump($foo->bar);
+
+$foo2 = new Foo('passed value');
+var_dump($foo2->bar);
+
+// Test that non-promoted readonly properties still cannot be reassigned
+class NonPromoted {
+    public readonly string $prop;
+
+    public function __construct() {
+        $this->prop = 'first';
+        try {
+            $this->prop = 'second';  // Should fail - not a promoted property
+        } catch (Error $e) {
+            echo $e->getMessage(), "\n";
+        }
+    }
+}
+
+$np = new NonPromoted();
+var_dump($np->prop);
+
+// Test mixed: promoted and non-promoted in same class
+class PromotedAndNonPromoted {
+    public readonly string $nonPromoted;
+
+    public function __construct(
+        public readonly string $promoted = 'default',
+    ) {
+        $this->nonPromoted = 'first';
+        $this->promoted = 'reassigned';  // Allowed (promoted)
+        try {
+            $this->nonPromoted = 'second';  // Should fail (non-promoted)
+        } catch (Error $e) {
+            echo $e->getMessage(), "\n";
+        }
+    }
+}
+
+$m = new PromotedAndNonPromoted();
+var_dump($m->promoted, $m->nonPromoted);
+
+// Reassignment is NOT allowed in methods called by the constructor
+class CalledMethod {
+    public function __construct(
+        public readonly string $prop = 'default',
+    ) {
+        $this->initProp();
+    }
+
+    private function initProp(): void {
+        try {
+            $this->prop = 'from method';
+        } catch (Error $e) {
+            echo $e->getMessage(), "\n";
+        }
+    }
+}
+
+$cm = new CalledMethod();
+var_dump($cm->prop);
+
+// Reassignment is NOT allowed in closures called by the constructor
+class ClosureInConstructor {
+    public function __construct(
+        public readonly string $prop = 'default',
+    ) {
+        $fn = function() {
+            try {
+                $this->prop = 'from closure';
+            } catch (Error $e) {
+                echo $e->getMessage(), "\n";
+            }
+        };
+        $fn();
+    }
+}
+
+$cc = new ClosureInConstructor();
+var_dump($cc->prop);
+
+?>
+--EXPECT--
+float(0)
+float(0)
+float(1)
+float(2)
+Cannot modify readonly property FailingPoint::$x
+float(10)
+Cannot modify readonly property Point::$x
+string(23) "modified in constructor"
+string(12) "passed value"
+Cannot modify readonly property NonPromoted::$prop
+string(5) "first"
+Cannot modify readonly property PromotedAndNonPromoted::$nonPromoted
+string(10) "reassigned"
+string(5) "first"
+Cannot modify readonly property CalledMethod::$prop
+string(7) "default"
+Cannot modify readonly property ClosureInConstructor::$prop
+string(7) "default"

Zend/zend_object_handlers.c

@@ -1100,7 +1100,21 @@ ZEND_API zval *zend_std_write_property(zend_object *zobj, zend_string *name, zva
 					variable_ptr = &EG(error_zval);
 					goto exit;
 				}
-				Z_PROP_FLAG_P(variable_ptr) &= ~(IS_PROP_UNINIT|IS_PROP_REINITABLE);
+				/* For promoted readonly properties being initialized in the constructor,
+				 * set IS_PROP_REINITABLE to allow one more assignment in the constructor body. */
+				if ((prop_info->flags & (ZEND_ACC_READONLY | ZEND_ACC_PROMOTED)) == (ZEND_ACC_READONLY | ZEND_ACC_PROMOTED)
+				 && (Z_PROP_FLAG_P(variable_ptr) & IS_PROP_UNINIT)) {
+					zend_execute_data *execute_data = EG(current_execute_data);
+					if (execute_data && EX(func)
+					 && ZEND_USER_CODE(EX(func)->common.type)
+					 && EX(func) == (zend_function *)zobj->ce->constructor) {
+						Z_PROP_FLAG_P(variable_ptr) = IS_PROP_REINITABLE;
+					} else {
+						Z_PROP_FLAG_P(variable_ptr) = 0;
+					}
+				} else {
+					Z_PROP_FLAG_P(variable_ptr) &= ~(IS_PROP_UNINIT|IS_PROP_REINITABLE);
+				}
 				value = &tmp;
 			}