Implement variadic function syntax

As per RFC: https://wiki.php.net/rfc/variadics

NEWS

@@ -14,6 +14,8 @@ PHP                                                                        NEWS
   . Reduced POST data memory usage by 200-300%. Removed INI setting
     always_populate_raw_post_data and the $HTTP_RAW_POST_DATA global
     variable. (Mike)
+  . Implemented dedicated syntax for variadic functions
+    (RFC: https://wiki.php.net/rfc/variadics). (Nikita)
 
 - cURL:
   . Implemented FR #65646 (re-enable CURLOPT_FOLLOWLOCATION with open_basedir

UPGRADING

@@ -34,8 +34,10 @@ PHP X.Y UPGRADE NOTES
 2. New Features
 ========================================
 
-- Core:
-  The php://input stream is now re-usable and can be used concurrently with 
+- Added dedicated syntax for variadic functions.
+  (https://wiki.php.net/rfc/variadics)
+
+- The php://input stream is now re-usable and can be used concurrently with 
   enable_post_data_reading=0.
 
 ========================================

UPGRADING.INTERNALS

@@ -6,6 +6,7 @@ UPGRADE NOTES - PHP X.Y
   a. Addition of do_operation and compare object handlers
   b. return_value_ptr now always available, RETVAL_ZVAL_FAST macros
   c. POST data handling
+  d. Arginfo changes
 
 2. Build system changes
   a. Unix build system changes
@@ -68,6 +69,47 @@ UPGRADE NOTES - PHP X.Y
   The recommended way to access raw POST data is to open and use a php://input 
   stream wrapper.  It is safe to be used concurrently and more than once. 
 
+  d. Arginfo changes
+
+  The pass_rest_by_reference argument of the ZEND_BEGIN_ARG_INFO and
+  ZEND_BEGIN_ARG_INFO_EX() is no longer used. The value passed to it is ignored.
+
+  Instead a variadic argument is created using ZEND_ARG_VARIADIC_INFO():
+
+      ZEND_ARG_VARIADIC_INFO(0, name) /* pass rest by value */
+      ZEND_ARG_VARIADIC_INFO(1, name) /* pass rest by reference */
+      ZEND_ARG_VARIADIC_INFO(ZEND_SEND_PREFER_REF, name)
+          /* pass rest by prefer-ref */
+
+  ZEND_ARG_VARIADIC_INFO() should only be used for the last argument.
+
+  The following changes were applied to the zend_arg_info struct:
+
+       typedef struct _zend_arg_info {
+           const char *class_name;
+           zend_uint class_name_len;
+           zend_uchar type_hint;
+      +    zend_uchar pass_by_reference;
+           zend_bool allow_null;
+      -    zend_bool pass_by_reference;
+      +    zend_bool is_variadic;
+       } zend_arg_info;
+
+  The following changes were applied to the zend_internal_function_info struct:
+
+       typedef struct _zend_internal_function_info {
+           zend_uint required_num_args;
+           zend_uchar _type_hint;
+           zend_bool return_reference;
+      -    zend_bool pass_rest_by_reference;
+      +    zend_bool _allow_null;
+      +    zend_bool _is_variadic;
+       } zend_internal_function_info;
+
+  The CHECK_ARG_SEND_TYPE(), ARG_MUST_BE_SENT_BY_REF(),
+  ARG_SHOULD_BE_SENT_BY_REF() and ARG_MAY_BE_SENT_BY_REF() macros now assume
+  that the argument passed to them is a zend_function* and that it is non-NULL.
+
 ========================
 2. Build system changes
 ========================

Zend/tests/variadic/adding_additional_optional_parameter.phpt

@@ -0,0 +1,17 @@
+--TEST--
+It's possible to add additional optional arguments with matching signature
+--FILE--
+<?php
+
+interface DB {
+    public function query($query, string ...$params);
+}
+
+class MySQL implements DB {
+    public function query($query, string $extraParam = null, string ...$params) { }
+}
+
+?>
+===DONE===
+--EXPECT--
+===DONE===

Zend/tests/variadic/adding_additional_optional_parameter_error.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Additional optional parameters must have a matching prototype
+--FILE--
+<?php
+
+interface DB {
+    public function query($query, string ...$params);
+}
+
+class MySQL implements DB {
+    public function query($query, int $extraParam = null, string ...$params) { }
+}
+
+?>
+--EXPECTF--
+Fatal error: Declaration of MySQL::query() must be compatible with DB::query($query, string ...$params) in %s on line %d

Zend/tests/variadic/basic.phpt

@@ -0,0 +1,57 @@
+--TEST--
+Basic variadic function
+--FILE--
+<?php
+
+function test1(... $args) {
+    var_dump($args);
+}
+
+test1();
+test1(1);
+test1(1, 2, 3);
+
+function test2($arg1, $arg2, ...$args) {
+    var_dump($arg1, $arg2, $args);
+}
+
+test2(1, 2);
+test2(1, 2, 3);
+test2(1, 2, 3, 4, 5);
+
+?>
+--EXPECT--
+array(0) {
+}
+array(1) {
+  [0]=>
+  int(1)
+}
+array(3) {
+  [0]=>
+  int(1)
+  [1]=>
+  int(2)
+  [2]=>
+  int(3)
+}
+int(1)
+int(2)
+array(0) {
+}
+int(1)
+int(2)
+array(1) {
+  [0]=>
+  int(3)
+}
+int(1)
+int(2)
+array(3) {
+  [0]=>
+  int(3)
+  [1]=>
+  int(4)
+  [2]=>
+  int(5)
+}

Zend/tests/variadic/by_ref.phpt

@@ -0,0 +1,24 @@
+--TEST--
+Variadic arguments with by-reference passing
+--FILE--
+<?php
+
+function test(&... $args) {
+    $i = 0;
+    foreach ($args as &$arg) {
+        $arg = $i++;
+    }
+}
+
+test();
+test($a);
+var_dump($a);
+test($b, $c, $d);
+var_dump($b, $c, $d);
+
+?>
+--EXPECT--
+int(0)
+int(0)
+int(1)
+int(2)

Zend/tests/variadic/by_ref_error.phpt

@@ -0,0 +1,12 @@
+--TEST--
+By-ref variadics enforce the reference
+--FILE--
+<?php
+
+function test(&... $args) { }
+
+test(1);
+
+?>
+--EXPECTF--
+Fatal error: Only variables can be passed by reference in %s on line %d

Zend/tests/variadic/no_default_error.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Variadic argument cannot have a default value
+--FILE--
+<?php
+
+function test(...$args = 123) {}
+
+?>
+--EXPECTF--
+Fatal error: Variadic parameter cannot have a default value in %s on line %d

Zend/tests/variadic/non_variadic_implements_variadic_error.phpt

@@ -0,0 +1,16 @@
+--TEST--
+It's not possible to turn a variadic function into a non-variadic one
+--FILE--
+<?php
+
+interface DB {
+    public function query($query, ...$params);
+}
+
+class MySQL implements DB {
+    public function query($query, $params) { }
+}
+
+?>
+--EXPECTF--
+Fatal error: Declaration of MySQL::query() must be compatible with DB::query($query, ...$params) in %s on line %d

Zend/tests/variadic/only_last_error.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Only the last argument can be variadic
+--FILE--
+<?php
+
+function test($foo, ...$bar, $baz) {}
+
+?>
+--EXPECTF--
+Fatal error: Only the last parameter can be variadic in %s on line %d

Zend/tests/variadic/optional_params.phpt

@@ -0,0 +1,49 @@
+--TEST--
+Optional parameter before variadic parameter
+--FILE--
+<?php
+
+function fn($reqParam, $optParam = null, ...$params) {
+    var_dump($reqParam, $optParam, $params);
+}
+
+fn(1);
+fn(1, 2);
+fn(1, 2, 3);
+fn(1, 2, 3, 4);
+fn(1, 2, 3, 4, 5);
+
+?>
+--EXPECT--
+int(1)
+NULL
+array(0) {
+}
+int(1)
+int(2)
+array(0) {
+}
+int(1)
+int(2)
+array(1) {
+  [0]=>
+  int(3)
+}
+int(1)
+int(2)
+array(2) {
+  [0]=>
+  int(3)
+  [1]=>
+  int(4)
+}
+int(1)
+int(2)
+array(3) {
+  [0]=>
+  int(3)
+  [1]=>
+  int(4)
+  [2]=>
+  int(5)
+}

Zend/tests/variadic/removing_parameter_error.phpt

@@ -0,0 +1,20 @@
+--TEST--
+It's not possible to remove required parameter before a variadic parameter
+--FILE--
+<?php
+
+/* Theoretically this should be valid because it weakens the constraint, but
+ * PHP does not allow this (for non-variadics), so I'm not allowing it here, too,
+ * to stay consistent. */
+
+interface DB {
+    public function query($query, ...$params);
+}
+
+class MySQL implements DB {
+    public function query(...$params) { }
+}
+
+?>
+--EXPECTF--
+Fatal error: Declaration of MySQL::query() must be compatible with DB::query($query, ...$params) in %s on line %d

Zend/tests/variadic/typehint_error.phpt

@@ -0,0 +1,36 @@
+--TEST--
+Variadic arguments enforce typehints
+--FILE--
+<?php
+
+function test(array... $args) {
+    var_dump($args);
+}
+
+test();
+test([0], [1], [2]);
+test([0], [1], 2);
+
+?>
+--EXPECTF--
+array(0) {
+}
+array(3) {
+  [0]=>
+  array(1) {
+    [0]=>
+    int(0)
+  }
+  [1]=>
+  array(1) {
+    [0]=>
+    int(1)
+  }
+  [2]=>
+  array(1) {
+    [0]=>
+    int(2)
+  }
+}
+
+Catchable fatal error: Argument 3 passed to test() must be of the type array, integer given, called in %s on line %d

Zend/tests/variadic/typehint_suppressed_error.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Error suppression for typehints on variadic arguments works
+--FILE--
+<?php
+
+function test(array... $args) {
+    var_dump($args);
+}
+
+set_error_handler(function($errno, $errstr) {
+    var_dump($errstr);
+    return true;
+});
+
+test([0], [1], 2);
+
+?>
+--EXPECTF--
+string(%d) "Argument 3 passed to test() must be of the type array, integer given, called in %s on line %d and defined"
+array(3) {
+  [0]=>
+  array(1) {
+    [0]=>
+    int(0)
+  }
+  [1]=>
+  array(1) {
+    [0]=>
+    int(1)
+  }
+  [2]=>
+  int(2)
+}