[RFC] Final Property Promotion

https://wiki.php.net/rfc/final_promotion

Author: DanielEScherzer

UPGRADING

@@ -106,6 +106,8 @@ PHP 8.5 UPGRADE NOTES
   . Fatal Errors (such as an exceeded maximum execution time) now include a
     backtrace.
     RFC: https://wiki.php.net/rfc/error_backtraces_v2
+  . Constructor property promotion can now be used for final properties.
+    RFC: https://wiki.php.net/rfc/final_promotion
 
 - Curl:
   . Added support for share handles that are persisted across multiple PHP

Zend/tests/property_hooks/final_prop_promoted_1.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Promoted property may be marked final (hook)
+--FILE--
+<?php
+
+class A {
+    public function __construct(
+        public final $prop { get {} set {} }
+    ) {}
+}
+
+class B extends A {
+    public $prop { get {} set {} }
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot override final property A::$prop in %s on line %d

Zend/tests/property_hooks/final_prop_promoted_2.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Promoted property may be marked final (normal)
+--FILE--
+<?php
+
+class A {
+    public function __construct(
+        public final $prop
+    ) {}
+}
+
+class B extends A {
+    public $prop { get {} set {} }
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot override final property A::$prop in %s on line %d

Zend/tests/property_hooks/final_prop_promoted_3.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Promoted property may be marked final (no visibility needed)
+--FILE--
+<?php
+
+class A {
+    public function __construct(
+        final $prop
+    ) {}
+}
+
+class B extends A {
+    public $prop { get {} set {} }
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot override final property A::$prop in %s on line %d

Zend/tests/property_hooks/final_prop_promoted_ast.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Confirm that the AST indicates final promoted properties
+--FILE--
+<?php
+try {
+    assert(false && new class {
+        public function __construct( public final $prop ) {}
+    });
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+?>
+--EXPECT--
+assert(false && new class {
+    public function __construct(public final $prop) {
+    }
+
+})

Zend/zend_ast.c

@@ -2721,6 +2721,9 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 				zend_ast_export_attributes(str, ast->child[3], indent, 0);
 			}
 			zend_ast_export_visibility(str, ast->attr, ZEND_MODIFIER_TARGET_CPP);
+			if (ast->attr & ZEND_ACC_FINAL) {
+				smart_str_appends(str, "final ");
+			}
 			if (ast->child[0]) {
 				zend_ast_export_type(str, ast->child[0], indent);
 				smart_str_appendc(str, ' ');

Zend/zend_compile.c

@@ -903,13 +903,7 @@ uint32_t zend_modifier_token_to_flag(zend_modifier_target target, uint32_t token
 			}
 			break;
 		case T_FINAL:
-			if (target == ZEND_MODIFIER_TARGET_METHOD
-				|| target == ZEND_MODIFIER_TARGET_CONSTANT
-				|| target == ZEND_MODIFIER_TARGET_PROPERTY
-				|| target == ZEND_MODIFIER_TARGET_PROPERTY_HOOK) {
-				return ZEND_ACC_FINAL;
-			}
-			break;
+			return ZEND_ACC_FINAL;
 		case T_STATIC:
 			if (target == ZEND_MODIFIER_TARGET_PROPERTY || target == ZEND_MODIFIER_TARGET_METHOD) {
 				return ZEND_ACC_STATIC;
@@ -7622,7 +7616,7 @@ static void zend_compile_params(zend_ast *ast, zend_ast *return_type_ast, uint32
 		zend_string *name = zval_make_interned_string(zend_ast_get_zval(var_ast));
 		bool is_ref = (param_ast->attr & ZEND_PARAM_REF) != 0;
 		bool is_variadic = (param_ast->attr & ZEND_PARAM_VARIADIC) != 0;
-		uint32_t property_flags = param_ast->attr & (ZEND_ACC_PPP_MASK | ZEND_ACC_PPP_SET_MASK | ZEND_ACC_READONLY);
+		uint32_t property_flags = param_ast->attr & (ZEND_ACC_PPP_MASK | ZEND_ACC_PPP_SET_MASK | ZEND_ACC_READONLY | ZEND_ACC_FINAL);
 		bool is_promoted = property_flags || hooks_ast;
 
 		znode var_node, default_node;

ext/reflection/tests/ReflectionProperty_isFinal.phpt

@@ -12,6 +12,8 @@ class C {
     public protected(set) final mixed $p6;
     public private(set) mixed $p7;
     public private(set) final mixed $p8;
+
+    public function __construct( final $p9 ) {}
 }
 
 $rc = new ReflectionClass(C::class);
@@ -30,3 +32,4 @@ p5: bool(false)
 p6: bool(true)
 p7: bool(true)
 p8: bool(true)
+p9: bool(true)