Typed class constants (#10444)

RFC: https://wiki.php.net/rfc/typed_class_constants

Co-Authored-By: Ben <[email protected]>
Co-Authored-By: Bob Weinand <[email protected]>
Co-Authored-By: Ilija Tovilo <[email protected]>

Author: 4 people

UPGRADING

@@ -52,6 +52,8 @@ PHP 8.3 UPGRADE NOTES
   . Anonymous classes may now be marked as readonly.
   . Readonly properties can now be reinitialized during cloning.
     RFC: https://wiki.php.net/rfc/readonly_amendments
+  . Class, interface, trait, and enum constants now support type
+    declarations. RFC: https://wiki.php.net/rfc/typed_class_constants
 
 - Posix
   . posix_getrlimit() now takes an optional $res parameter to allow fetching a

Zend/tests/type_declarations/typed_class_constants_diamond_error1.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Typed class constants (diamond error with self)
+--FILE--
+<?php
+class A {
+    public const self CONST1 = C;
+}
+
+try {
+    define("C", new A());
+} catch (Error $exception) {
+    echo $exception->getMessage() . "\n";
+}
+?>
+--EXPECT--
+Undefined constant "C"

Zend/tests/type_declarations/typed_class_constants_inheritance_error1.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Typed class constants (incompatible inheritance; simple)
+--FILE--
+<?php
+class A {
+    public const int CONST1 = 1;
+}
+
+class B extends A {
+    public const string CONST1 = 'a';
+}
+?>
+--EXPECTF--
+Fatal error: Type of B::CONST1 must be compatible with A::CONST1 of type int in %s on line %d

Zend/tests/type_declarations/typed_class_constants_inheritance_error2.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Typed class constants (incompatible inheritance; missing type in child)
+--FILE--
+<?php
+class A {
+    public const int CONST1 = 1;
+}
+
+class B extends A {
+    public const CONST1 = 0;
+}
+?>
+--EXPECTF--
+Fatal error: Type of B::CONST1 must be compatible with A::CONST1 of type int in %s on line %d

Zend/tests/type_declarations/typed_class_constants_inheritance_error3.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Typed class constants (incompatible composition; traits)
+--FILE--
+<?php
+
+trait T {
+    public const ?array CONST1 = [];
+}
+
+class C {
+    use T;
+
+    public const CONST1 = [];
+}
+
+?>
+--EXPECTF--
+Fatal error: C and T define the same constant (CONST1) in the composition of C. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/type_declarations/typed_class_constants_inheritance_error4.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Typed class constants (incompatible covariant composition; traits)
+--FILE--
+<?php
+
+trait T {
+    public const ?array CONST1 = [];
+}
+
+class C {
+    use T;
+
+    public const array CONST1 = [];
+}
+
+?>
+--EXPECTF--
+Fatal error: C and T define the same constant (CONST1) in the composition of C. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/type_declarations/typed_class_constants_inheritance_error5.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Typed class constants (incompatible contravariant composition; traits)
+--FILE--
+<?php
+
+trait T {
+    public const array CONST1 = [];
+}
+
+class C {
+    use T;
+
+    public const ?array CONST1 = [];
+}
+
+?>
+--EXPECTF--
+Fatal error: C and T define the same constant (CONST1) in the composition of C. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/type_declarations/typed_class_constants_inheritance_success1.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Typed class constants (inheritance success)
+--FILE--
+<?php
+class A {
+    public const CONST1 = 1;
+    public const CONST2 = 1;
+    public const mixed CONST3 = 1;
+    public const iterable CONST4 = [];
+}
+
+class B extends A {
+    public const int CONST1 = 0;
+    public const mixed CONST2 = 0;
+    public const mixed CONST3 = 0;
+    public const array CONST4 = [];
+}
+
+var_dump(B::CONST1);
+var_dump(B::CONST2);
+var_dump(B::CONST3);
+var_dump(B::CONST4);
+?>
+--EXPECT--
+int(0)
+int(0)
+int(0)
+array(0) {
+}

Zend/tests/type_declarations/typed_class_constants_inheritance_success2.phpt

@@ -0,0 +1,48 @@
+--TEST--
+Typed class constants (inheritance success - object types)
+--FILE--
+<?php
+class S implements Stringable {
+    public function __toString() {
+        return "";
+    }
+}
+
+class Z extends S {}
+
+class A {
+    public const object CONST1 = S;
+    public const S CONST2 = S;
+    public const S|Stringable CONST3 = S;
+    public const S CONST4 = S;
+    public const ?S CONST5 = S;
+}
+
+class B extends A {
+    public const S CONST1 = Z;
+    public const Z CONST2 = Z;
+    public const S CONST3 = Z;
+    public const S&Stringable CONST4 = Z;
+    public const (S&Stringable)|null CONST5 = Z;
+}
+
+define("S", new S());
+define("Z", new Z());
+
+var_dump(B::CONST1);
+var_dump(B::CONST2);
+var_dump(B::CONST3);
+var_dump(B::CONST4);
+var_dump(B::CONST5);
+?>
+--EXPECTF--
+object(Z)#%d (%d) {
+}
+object(Z)#%d (%d) {
+}
+object(Z)#%d (%d) {
+}
+object(Z)#%d (%d) {
+}
+object(Z)#%d (%d) {
+}

Zend/tests/type_declarations/typed_class_constants_inheritance_success3.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Typed class constants (inheritance; private constants)
+--FILE--
+<?php
+class A {
+    private const int CONST1 = 1;
+}
+
+class B extends A {
+    public const string CONST1 = 'a';
+}
+
+var_dump(B::CONST1);
+?>
+--EXPECT--
+string(1) "a"