Fix GH-17916: Final abstract properties should error

Closes GH-17917.

Author: DanielEScherzer

NEWS

@@ -17,6 +17,8 @@ PHP                                                                        NEWS
     `__callStatic` is allowed). (timwolla)
   . Fixed bug GH-17713 (ReflectionProperty::getRawValue() and related methods
     may call hooks of overridden properties). (Arnaud)
+  . Fixed bug GH-17916 (Final abstract properties should error).
+    (DanielEScherzer)
 
 - DOM:
   . Fixed bug GH-17609 (Typo in error message: Dom\NO_DEFAULT_NS instead of

Zend/tests/property_hooks/abstract_prop_final.phpt

@@ -0,0 +1,14 @@
+--TEST--
+GH-17916: Abstract property cannot be marked as final
+--FILE--
+<?php
+
+abstract class Foo {
+    final abstract public string $bar {
+        get;
+    }
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot use the final modifier on an abstract property in %s on line %d

Zend/zend_compile.c

@@ -1036,10 +1036,17 @@ uint32_t zend_add_member_modifier(uint32_t flags, uint32_t new_flag, zend_modifi
 			"Multiple readonly modifiers are not allowed", 0);
 		return 0;
 	}
-	if (target == ZEND_MODIFIER_TARGET_METHOD && (new_flags & ZEND_ACC_ABSTRACT) && (new_flags & ZEND_ACC_FINAL)) {
-		zend_throw_exception(zend_ce_compile_error,
-			"Cannot use the final modifier on an abstract method", 0);
-		return 0;
+	if ((new_flags & ZEND_ACC_ABSTRACT) && (new_flags & ZEND_ACC_FINAL)) {
+		if (target == ZEND_MODIFIER_TARGET_METHOD) {
+			zend_throw_exception(zend_ce_compile_error,
+				"Cannot use the final modifier on an abstract method", 0);
+			return 0;
+		}
+		if (target == ZEND_MODIFIER_TARGET_PROPERTY) {
+			zend_throw_exception(zend_ce_compile_error,
+				"Cannot use the final modifier on an abstract property", 0);
+			return 0;
+		}
 	}
 	if (target == ZEND_MODIFIER_TARGET_PROPERTY || target == ZEND_MODIFIER_TARGET_CPP) {
 		if ((flags & ZEND_ACC_PPP_SET_MASK) && (new_flag & ZEND_ACC_PPP_SET_MASK)) {