Allow named args after unpack

Currently, argument unpacking and named arguments cannot be mixed
at all. This relaxes the restriction to allow
foo(...$args, named: $arg). The variant foo(named: $arg, ...$args)
is still forbidden, because we can't ensure that positional
parameters come before named parameters in that case (without more
intrusive changes). Effectively this just enforces a required style,
as the order of unpack and named args doesn't matter for the cases
where both could be well-defined.

ML discussion: https://externals.io/message/114589

Closes GH-7009.

Author: nikic

UPGRADING

@@ -185,6 +185,8 @@ PHP 8.1 UPGRADE NOTES
   . File uploads now provide an additional full_path key, which contains the
     full path (rather than just the basename) of the uploaded file. This is
     intended for use in conjunction with "upload webkitdirectory".
+  . It is now allowed to specify named arguments after an argument unpack, e.g.
+    foo(...$args, named: $arg).
 
 - Curl:
   . Added CURLOPT_DOH_URL option.

Zend/tests/named_params/unpack_and_named_1.phpt

@@ -1,10 +1,58 @@
 --TEST--
-Mixing unpacking and named params (1)
+Named args after unpacking (supported)
 --FILE--
 <?php
 
-test(...[], a: 42);
+function test(...$args) {
+    var_dump($args);
+}
+
+test(...[1, 2], a: 3);
+test(...[1, 'a' => 2], b: 3);
+
+function test2($a, $b, $c = 3, $d = 4) {
+    var_dump($a, $b, $c, $d);
+}
+
+test2(...[1, 2], d: 40);
+test2(...['b' => 2, 'a' => 1], d: 40);
+
+try {
+    test2(...[1, 2], b: 20);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+try {
+    test2(...[1, 'b' => 2], b: 20);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
 
 ?>
---EXPECTF--
-Fatal error: Cannot combine named arguments and argument unpacking in %s on line %d
+--EXPECT--
+array(3) {
+  [0]=>
+  int(1)
+  [1]=>
+  int(2)
+  ["a"]=>
+  int(3)
+}
+array(3) {
+  [0]=>
+  int(1)
+  ["a"]=>
+  int(2)
+  ["b"]=>
+  int(3)
+}
+int(1)
+int(2)
+int(3)
+int(40)
+int(1)
+int(2)
+int(3)
+int(40)
+Named parameter $b overwrites previous argument
+Named parameter $b overwrites previous argument

Zend/tests/named_params/unpack_and_named_2.phpt

@@ -1,10 +1,10 @@
 --TEST--
-Mixing unpacking and named params (2)
+Named args before unpacking (not supported)
 --FILE--
 <?php
 
 test(a: 42, ...[]);
 
 ?>
 --EXPECTF--
-Fatal error: Cannot combine named arguments and argument unpacking in %s on line %d
+Fatal error: Cannot use argument unpacking after named arguments in %s on line %d

Zend/zend_compile.c

@@ -3472,7 +3472,7 @@ uint32_t zend_compile_args(
 		if (arg->kind == ZEND_AST_UNPACK) {
 			if (uses_named_args) {
 				zend_error_noreturn(E_COMPILE_ERROR,
-					"Cannot combine named arguments and argument unpacking");
+					"Cannot use argument unpacking after named arguments");
 			}
 
 			uses_arg_unpack = 1;
@@ -3492,16 +3492,11 @@ uint32_t zend_compile_args(
 		}
 
 		if (arg->kind == ZEND_AST_NAMED_ARG) {
-			if (uses_arg_unpack) {
-				zend_error_noreturn(E_COMPILE_ERROR,
-					"Cannot combine named arguments and argument unpacking");
-			}
-
 			uses_named_args = 1;
 			arg_name = zval_make_interned_string(zend_ast_get_zval(arg->child[0]));
 			arg = arg->child[1];
 
-			if (fbc) {
+			if (fbc && !uses_arg_unpack) {
 				arg_num = zend_get_arg_num(fbc, arg_name);
 				if (arg_num == arg_count + 1 && !may_have_undef) {
 					/* Using named arguments, but passing in order. */