[Rfc] data classes

Zend/tests/data_class_001.phpt

@@ -0,0 +1,30 @@
+--TEST--
+Data classes can be defined and compared.
+--FILE--
+<?php
+
+data class Point {
+    public function __construct(public int $x, public int $y) {}
+}
+
+$p1 = new Point(1, 2);
+$p2 = new Point(1, 2);
+$p3 = new Point(2, 3);
+
+var_dump($p1 === $p2);
+var_dump($p1 !== $p2);
+var_dump($p1 === $p3);
+var_dump($p1 !== $p3);
+var_dump($p1);
+?>
+--EXPECT--
+bool(true)
+bool(false)
+bool(false)
+bool(true)
+data object(Point)#1 (2) {
+  ["x"]=>
+  int(1)
+  ["y"]=>
+  int(2)
+}

Zend/tests/data_class_002.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Data classes can be combined with inheritance and other features.
+--FILE--
+<?php
+
+data class Point {
+    public function __construct(public int $x, public int $y) {}
+}
+
+final data class Point3D extends Point {
+    public function __construct(int $x, int $y, public int $z) {
+        parent::__construct($x, $y);
+    }
+}
+
+$p2 = new Point3D(1, 2, 3);
+$p3 = new Point3D(1, 2, 3);
+$p4 = new Point3D(2, 3, 4);
+
+var_dump($p2 === $p3);
+var_dump($p2 !== $p3);
+var_dump($p2 === $p4);
+var_dump($p2 !== $p4);
+?>
+--EXPECT--
+bool(true)
+bool(false)
+bool(false)
+bool(true)

Zend/tests/data_class_003.phpt

@@ -0,0 +1,17 @@
+--TEST--
+Data class inheritance rules are enforced.
+--FILE--
+<?php
+
+class Point {
+    public function __construct(public int $x, public int $y) {}
+}
+
+data class Point3D extends Point {
+    public function __construct(int $x, int $y, public int $z) {
+        parent::__construct($x, $y);
+    }
+}
+?>
+--EXPECTF--
+Fatal error: Data class Point3D cannot extend non-data class Point in %s on line %d

Zend/tests/data_class_004.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Reflection should work
+--FILE--
+<?php
+
+class Foo {
+    public function bar() {}
+}
+
+data class Bar {
+    public function baz() {}
+}
+
+$foo = new ReflectionClass(Foo::class);
+$bar = new ReflectionClass(Bar::class);
+var_dump($foo->isDataClass());
+var_dump($bar->isDataClass());
+?>
+--EXPECT--
+bool(false)
+bool(true)

Zend/tests/data_class_005.phpt

@@ -0,0 +1,52 @@
+--TEST--
+Copy on write
+--FILE--
+<?php
+
+data class Point {
+    public function __construct(public int $x, public int $y) {}
+    public function add(Point $other): Point {
+        $this->x += $other->x;
+        $this->y += $other->y;
+        return $this;
+    }
+    public function __toString(): string {
+        return "({$this->x},{$this->y})";
+    }
+}
+
+$p1 = new Point(1, 2);
+$p2 = $p1;
+
+// p2 is copy on write (3,2)
+$p2->x = 3;
+echo "p1: $p1\n";
+echo "p2 (x+3): $p2\n";
+
+echo "p1->add(p2): " . $p1->add($p2) . "\n";
+echo "p1: $p1\n";
+$po = new Point(1,1);
+$p2 = $po;
+$p2->x++;
+echo "p2: $p2\n";
+echo "po: $po\n";
+
+function modify(Point $p): Point {
+    $p->y++;
+    return $p;
+}
+
+$p1 = new Point(1,1);
+$p2 = modify($p1);
+echo "p1: $p1\n";
+echo "p2: $p2\n";
+
+--EXPECT--
+p1: (1,2)
+p2 (x+3): (3,2)
+p1->add(p2): (4,4)
+p1: (1,2)
+p2: (2,1)
+po: (1,1)
+p1: (1,1)
+p2: (1,2)

Zend/tests/data_class_006.phpt

@@ -0,0 +1,42 @@
+--TEST--
+A convoluted path
+--FILE--
+<?php
+
+data class Length {
+    public function __construct(public float $length) {}
+}
+
+data class Point {
+    public int $x;
+    private Length $l;
+    public function __construct(int $x, public int $y) {
+        $previous = $this;
+        $this->x = $x;
+        $this->l = new Length($x + $y);
+        echo "$previous === $this\n";
+    }
+
+    public function addNoisily(Point $other): Point {
+        echo "Adding $this and $other\n";
+        $previous = $this;
+        $this->x += $other->x;
+        $this->y += $other->y;
+        $this->l = new Length($this->x + $this->y);
+        echo "$previous !== $this\n";
+        return $this;
+    }
+
+    public function __toString(): string {
+        return "({$this->x},{$this->y}|{$this->l->length})";
+    }
+}
+
+$p1 = new Point(1, 2);
+$p2 = $p1->addNoisily($p1);
+
+?>
+--EXPECT--
+(1,2|3) === (1,2|3)
+Adding (1,2|3) and (1,2|3)
+(1,2|3) !== (2,4|6)

Zend/tests/data_class_007.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Private properties are included in equality checks
+--FILE--
+<?php
+
+data class Length {
+    public function __construct(private float $length) {}
+}
+
+$l1 = new Length(1.0);
+$l2 = new Length(1.0);
+$l3 = new Length(2.0);
+var_dump($l1 === $l2);
+var_dump($l1 !== $l3);
+?>
+--EXPECT--
+bool(true)
+bool(true)

Zend/tests/data_class_008.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Data classes can be anonymous
+--FILE--
+<?php
+
+$data = new data class(1) {
+    public function __construct(private int $value) {}
+};
+
+var_dump($data);
+?>
+--EXPECT--
+data object(class@anonymous)#1 (1) {
+  ["value":"class@anonymous":private]=>
+  int(1)
+}

Zend/tests/data_class_009.phpt

@@ -0,0 +1,20 @@
+--TEST--
+unset triggers copy-on-write
+--FILE--
+<?php
+
+$data = new data class(1) {
+    public function __construct(public int $value) {}
+};
+
+$copy = $data;
+unset($copy->value);
+var_dump($data !== $copy);
+var_dump($data);
+?>
+--EXPECT--
+bool(true)
+data object(class@anonymous)#1 (1) {
+  ["value"]=>
+  int(1)
+}

Zend/tests/data_class_010.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Serialization works
+--FILE--
+<?php
+
+data class Point {
+    public function __construct(public int $x, public int $y) {}
+}
+
+$p = new Point(1, 2);
+$s = serialize($p);
+var_dump($s);
+$p2 = unserialize($s);
+var_dump($p2 === $p);
+?>
+--EXPECT--
+string(40) "O:5:"Point":2:{s:1:"x";i:1;s:1:"y";i:2;}"
+bool(true)

Zend/tests/data_class_011.phpt

@@ -0,0 +1,37 @@
+--TEST--
+Other features work with data classes
+--FILE--
+<?php
+
+interface Point {
+  public function add(Point $point): Point;
+  public float $length { get; }
+}
+
+trait PythagoreanTheorem {
+    public readonly float $length;
+
+    public function memoizeLength(): void {
+        $this->length = sqrt($this->x ** 2 + $this->y ** 2);
+    }
+}
+
+final readonly data class Point2D implements Point {
+    use PythagoreanTheorem; // contains implementation of $length
+
+    public function __construct(public int $x, public int $y) {
+        $this->memoizeLength(); // from the trait
+    }
+
+    public function add(Point $point): Point {
+        return new static($this->x + $point->x, $this->y + $point->y);
+    }
+}
+
+$p1 = new Point2D(1, 1);
+$p2 = new Point2D(2, 2);
+$p3 = $p1->add($p2);
+echo $p3->length, "\n";
+?>
+--EXPECT--
+6

Zend/zend_ast.c

@@ -1898,6 +1898,9 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 				if (decl->flags & ZEND_ACC_READONLY_CLASS) {
 					smart_str_appends(str, "readonly ");
 				}
+				if (decl->flags & ZEND_ACC_DATA_CLASS) {
+					smart_str_appends(str, "data ");
+				}
 				smart_str_appends(str, "class ");
 			}
 			smart_str_appendl(str, ZSTR_VAL(decl->name), ZSTR_LEN(decl->name));

Zend/zend_attributes.c

@@ -86,6 +86,11 @@ static void validate_allow_dynamic_properties(
 			ZSTR_VAL(scope->name)
 		);
 	}
+	if (scope->ce_flags & ZEND_ACC_DATA_CLASS) {
+		zend_error_noreturn(E_ERROR, "Cannot apply #[AllowDynamicProperties] to data class %s",
+			ZSTR_VAL(scope->name)
+		);
+	}
 	if (scope->ce_flags & ZEND_ACC_ENUM) {
 		zend_error_noreturn(E_ERROR, "Cannot apply #[AllowDynamicProperties] to enum %s",
 			ZSTR_VAL(scope->name)

Zend/zend_compile.c

@@ -862,6 +862,8 @@ static const char *zend_modifier_token_to_string(uint32_t token)
 			return "final";
 		case T_READONLY:
 			return "readonly";
+		case T_DATA:
+			return "data";
 		case T_ABSTRACT:
 			return "abstract";
 		case T_PUBLIC_SET:
@@ -995,6 +997,10 @@ uint32_t zend_add_class_modifier(uint32_t flags, uint32_t new_flag) /* {{{ */
 		zend_throw_exception(zend_ce_compile_error, "Multiple readonly modifiers are not allowed", 0);
 		return 0;
 	}
+	if ((flags & ZEND_ACC_DATA_CLASS) && (new_flag & ZEND_ACC_DATA_CLASS)) {
+		zend_throw_exception(zend_ce_compile_error, "Multiple data modifiers are not allowed", 0);
+		return 0;
+	}
 	if ((new_flags & ZEND_ACC_EXPLICIT_ABSTRACT_CLASS) && (new_flags & ZEND_ACC_FINAL)) {
 		zend_throw_exception(zend_ce_compile_error,
 			"Cannot use the final modifier on an abstract class", 0);
@@ -1020,6 +1026,10 @@ uint32_t zend_add_anonymous_class_modifier(uint32_t flags, uint32_t new_flag)
 		zend_throw_exception(zend_ce_compile_error, "Multiple readonly modifiers are not allowed", 0);
 		return 0;
 	}
+	if ((flags & ZEND_ACC_DATA_CLASS) && (new_flag & ZEND_ACC_DATA_CLASS)) {
+		zend_throw_exception(zend_ce_compile_error, "Multiple data modifiers are not allowed", 0);
+		return 0;
+	}
 	return new_flags;
 }
 

Zend/zend_compile.h

@@ -267,7 +267,7 @@ typedef struct _zend_oparray_context {
 #define ZEND_ACC_PROTECTED_SET           (1 << 11) /*     |     |  X  |     */
 #define ZEND_ACC_PRIVATE_SET             (1 << 12) /*     |     |  X  |     */
 /*                                                        |     |     |     */
-/* Class Flags (unused: 30,31)                            |     |     |     */
+/* Class Flags (unused: 31)                               |     |     |     */
 /* ===========                                            |     |     |     */
 /*                                                        |     |     |     */
 /* Special class types                                    |     |     |     */
@@ -333,6 +333,9 @@ typedef struct _zend_oparray_context {
 /* Class cannot be serialized or unserialized             |     |     |     */
 #define ZEND_ACC_NOT_SERIALIZABLE        (1 << 29) /*  X  |     |     |     */
 /*                                                        |     |     |     */
+/* Class is compared by value                             |     |     |     */
+#define ZEND_ACC_DATA_CLASS			     (1 << 30) /*  X  |     |     |     */
+/*                                                        |     |     |     */
 /* Function Flags (unused: 29-30)                         |     |     |     */
 /* ==============                                         |     |     |     */
 /*                                                        |     |     |     */

Zend/zend_inheritance.c

@@ -1783,6 +1783,13 @@ ZEND_API void zend_do_inheritance_ex(zend_class_entry *ce, zend_class_entry *par
 		);
 	}
 
+	if (UNEXPECTED((ce->ce_flags & ZEND_ACC_DATA_CLASS) != (parent_ce->ce_flags & ZEND_ACC_DATA_CLASS))) {
+		zend_error_noreturn(E_COMPILE_ERROR, "%s class %s cannot extend %s class %s",
+			ce->ce_flags & ZEND_ACC_DATA_CLASS ? "Data" : "Non-data", ZSTR_VAL(ce->name),
+			parent_ce->ce_flags & ZEND_ACC_DATA_CLASS ? "data" : "non-data", ZSTR_VAL(parent_ce->name)
+		);
+	}
+
 	if (ce->parent_name) {
 		zend_string_release_ex(ce->parent_name, 0);
 	}