Add support for final class constants

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

Co-authored-by: Nikita Popov <nikita.ppv@gmail.com>

Author: kocsismate

UPGRADING

@@ -67,6 +67,8 @@ PHP 8.1 UPGRADE NOTES
   . Added support for intersection types.
     They cannot be combined with union types.
     RFC: https://wiki.php.net/rfc/pure-intersection-types
+  . Added support for the final modifier for class constants.
+    RFC: https://wiki.php.net/rfc/final_class_const
 
 - Fileinfo:
   . The fileinfo functions now accept and return, respectively, finfo objects

Zend/tests/bug49472.phpt

@@ -23,5 +23,6 @@ class FooBar extends Foo implements ia {
 new FooBar;
 
 ?>
---EXPECTF--
-Fatal error: Cannot inherit previously-inherited or override constant c from interface ia in %s on line %d
+===DONE===
+--EXPECT--
+===DONE===

Zend/tests/constants/final_constants/final_const1.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Class constants support the final modifier
+--FILE--
+<?php
+
+class Foo
+{
+    final const A = "foo";
+    final public const B = "foo";
+}
+
+?>
+--EXPECT--

Zend/tests/constants/final_constants/final_const10.phpt

@@ -0,0 +1,22 @@
+--TEST--
+Interface constants inherited from other interfaces can be redeclared
+--FILE--
+<?php
+
+interface I1
+{
+    const C = 1;
+}
+
+interface I2
+{
+    const C = 2;
+}
+
+interface I3 extends I1, I2
+{
+    const C = 3;
+}
+
+?>
+--EXPECT--

Zend/tests/constants/final_constants/final_const11.phpt

@@ -0,0 +1,22 @@
+--TEST--
+Class constants cannot be inherited from both a class and an interface
+--FILE--
+<?php
+
+class C
+{
+    const C = 1;
+}
+
+interface I
+{
+    const C = 1;
+}
+
+class C2 extends C implements I
+{
+}
+
+?>
+--EXPECTF--
+Fatal error: Class C2 inherits both C::C and I::C, which is ambiguous in %s on line %d

Zend/tests/constants/final_constants/final_const12.phpt

@@ -0,0 +1,22 @@
+--TEST--
+Interface constants cannot be inherited from other interfaces
+--FILE--
+<?php
+
+interface I1
+{
+    const C = 1;
+}
+
+interface I2
+{
+    const C = 2;
+}
+
+interface I3 extends I1, I2
+{
+}
+
+?>
+--EXPECTF--
+Fatal error: Class I3 inherits both I1::C and I2::C, which is ambiguous in %s on line %d

Zend/tests/constants/final_constants/final_const2.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Final class constants cannot be overridden
+--FILE--
+<?php
+
+class Foo
+{
+    final const A = "foo";
+}
+
+class Bar extends Foo
+{
+    const A = "bar";
+}
+
+?>
+--EXPECTF--
+Fatal error: Bar::A cannot override final constant Foo::A in %s on line %d

Zend/tests/constants/final_constants/final_const3.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Private class constants cannot be final
+--FILE--
+<?php
+
+class Foo
+{
+    private final const A = "foo";
+}
+
+?>
+--EXPECTF--
+Fatal error: Private constant Foo::A cannot be final as it is not visible to other classes in %s on line %d

Zend/tests/constants/final_constants/final_const4.phpt

@@ -0,0 +1,17 @@
+--TEST--
+Interface constants can be overridden directly
+--FILE--
+<?php
+
+interface I
+{
+    const X = 1;
+}
+
+class C implements I
+{
+    const X = 2;
+}
+
+?>
+--EXPECT--

Zend/tests/constants/final_constants/final_const5.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Final interface constants cannot be overridden directly
+--FILE--
+<?php
+
+interface I
+{
+    final public const X = 1;
+}
+
+class C implements I
+{
+    const X = 2;
+}
+
+?>
+--EXPECTF--
+Fatal error: C::X cannot override final constant I::X in %s on line %d