Improve final/abstract methods in interfaces error messages

Closes #81683
Closes GH-7722

Author: iluuu1994

NEWS

@@ -7,6 +7,8 @@ PHP                                                                        NEWS
   . Fixed bug #81684 (Using null coalesce assignment with $GLOBALS["x"] produces
     opcode error). (ilutov)
   . Fixed bug #81656 (GCC-11 silently ignores -R). (Michael Wallner)
+  . Fixed bug #81683 (Misleading "access type ... must be public" error message
+    on final or abstract interface methods). (ilutov)
 
 - MBString:
   . Fixed bug #81693 (mb_check_encoding(7bit) segfaults). (cmb)

Zend/tests/bug71871.phpt

@@ -9,4 +9,4 @@ interface test {
 
 ?>
 --EXPECTF--
-Fatal error: Access type for interface method test::test() must be public in %s on line %d
+Fatal error: Interface method test::test() must not be final in %s on line %d

Zend/tests/bug71871_2.phpt

@@ -9,4 +9,4 @@ interface test {
 
 ?>
 --EXPECTF--
-Fatal error: Access type for interface method test::test() must be public in %s on line %d
+Fatal error: Interface method test::test() must not be abstract in %s on line %d

Zend/zend_compile.c

@@ -7039,10 +7039,18 @@ static zend_string *zend_begin_method_decl(zend_op_array *op_array, zend_string
 	}
 
 	if (in_interface) {
-		if (!(fn_flags & ZEND_ACC_PUBLIC) || (fn_flags & (ZEND_ACC_FINAL|ZEND_ACC_ABSTRACT))) {
+		if (!(fn_flags & ZEND_ACC_PUBLIC)) {
 			zend_error_noreturn(E_COMPILE_ERROR, "Access type for interface method "
 				"%s::%s() must be public", ZSTR_VAL(ce->name), ZSTR_VAL(name));
 		}
+		if (fn_flags & ZEND_ACC_FINAL) {
+			zend_error_noreturn(E_COMPILE_ERROR, "Interface method "
+				"%s::%s() must not be final", ZSTR_VAL(ce->name), ZSTR_VAL(name));
+		}
+		if (fn_flags & ZEND_ACC_ABSTRACT) {
+			zend_error_noreturn(E_COMPILE_ERROR, "Interface method "
+				"%s::%s() must not be abstract", ZSTR_VAL(ce->name), ZSTR_VAL(name));
+		}
 		op_array->fn_flags |= ZEND_ACC_ABSTRACT;
 	}