[RFC] Deprecate implicit nullable parameter types

UPGRADING

@@ -268,6 +268,10 @@ PHP 8.4 UPGRADE NOTES
 4. Deprecated Functionality
 ========================================
 
+- Core:
+  . Implicitly nullable parameter types are now deprecated.
+    RFC: https://wiki.php.net/rfc/deprecate-implicitly-nullable-types
+
 - Curl:
   . The CURLOPT_BINARYTRANSFER constant is deprecated.
 

Zend/tests/bug63635.phpt

@@ -6,7 +6,7 @@ class Node {
     public $parent = NULL;
     public $children = array();
 
-    function __construct(Node $parent=NULL) {
+    function __construct(?Node $parent=NULL) {
         if ($parent) {
             $parent->children[] = $this;
         }

Zend/tests/bug71428.1.phpt

@@ -3,7 +3,7 @@ bug #71428.1: inheritance with null default values
 --FILE--
 <?php
 class A {
-    public function m(array $a = null) {}
+    public function m(?array $a = null) {}
 }
 class B extends A {
     public function m(array $a = []) {}

Zend/tests/bug71428.3.phpt

@@ -7,4 +7,6 @@ class B           {  public function m(A $a = NULL, $n) { echo "B.m";} };
 class C extends B {  public function m(A $a       , $n) { echo "C.m";} };
 ?>
 --EXPECTF--
+Deprecated: Implicitly marking parameter $a as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
+
 Fatal error: Declaration of C::m(A $a, $n) must be compatible with B::m(?A $a, $n) in %sbug71428.3.php on line 4

Zend/tests/bug72119.phpt

@@ -3,7 +3,7 @@ Bug #72119 (Interface declaration compatibility regression with default values)
 --FILE--
 <?php
 interface Foo {
-    public function bar(array $baz = null);
+    public function bar(?array $baz = null);
 }
 
 class Hello implements Foo {

Zend/tests/gh11488.phpt

@@ -18,4 +18,6 @@ function c(
 --EXPECTF--
 Deprecated: Optional parameter $a declared before required parameter $b is implicitly treated as a required parameter in %s on line %d
 
+Deprecated: Implicitly marking parameter $c as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
+
 Deprecated: Optional parameter $e declared before required parameter $f is implicitly treated as a required parameter in %s on line %d

Zend/tests/ns_070.phpt

@@ -6,7 +6,7 @@ Testing parameter type-hinted with default value inside namespace
 namespace foo;
 
 class bar {
-    public function __construct(\stdclass $x = NULL) {
+    public function __construct(?\stdclass $x = NULL) {
         var_dump($x);
     }
 }

Zend/tests/ns_071.phpt

@@ -6,7 +6,7 @@ Testing parameter type-hinted (array) with default value inside namespace
 namespace foo;
 
 class bar {
-    public function __construct(array $x = NULL) {
+    public function __construct(?array $x = NULL) {
         var_dump($x);
     }
 }

Zend/tests/ns_072.phpt

@@ -10,7 +10,7 @@ interface foo {
 }
 
 class bar {
-    public function __construct(foo $x = NULL) {
+    public function __construct(?foo $x = NULL) {
         var_dump($x);
     }
 }

Zend/tests/ns_073.phpt

@@ -14,6 +14,7 @@ $x(new \stdclass);
 
 ?>
 --EXPECTF--
+Deprecated: Implicitly marking parameter $x as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 NULL
 object(stdClass)#%d (0) {
 }

Zend/tests/ns_074.phpt

@@ -5,7 +5,7 @@ Testing type-hinted lambda parameter inside namespace
 
 namespace foo;
 
-$x = function (\stdclass $x = NULL) {
+$x = function (?\stdclass $x = NULL) {
     var_dump($x);
 };
 

Zend/tests/required_param_after_optional.phpt

@@ -13,6 +13,10 @@ Deprecated: Optional parameter $testA declared before required parameter $testC
 
 Deprecated: Optional parameter $testB declared before required parameter $testC is implicitly treated as a required parameter in %s on line %d
 
+Deprecated: Implicitly marking parameter $test2A as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
+
 Deprecated: Optional parameter $test2B declared before required parameter $test2C is implicitly treated as a required parameter in %s on line %d
 
+Deprecated: Implicitly marking parameter $test3A as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
+
 Deprecated: Optional parameter $test3B declared before required parameter $test3C is implicitly treated as a required parameter in %s on line %d

Zend/tests/traits/bug60717.phpt

@@ -69,5 +69,10 @@ namespace HTML
     echo 'Done';
 }
 ?>
---EXPECT--
+--EXPECTF--
+Deprecated: Implicitly marking parameter $attributes as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
+
+Deprecated: Implicitly marking parameter $attributes as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
+
+Deprecated: Implicitly marking parameter $attributes as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 Done

Zend/tests/type_declarations/callable_003.phpt

@@ -13,7 +13,8 @@ function bar(callable $a = null) {
 foo("strpos", 123, "strpos");
 bar("substr");
 ?>
---EXPECT--
+--EXPECTF--
+Deprecated: Implicitly marking parameter $a as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 string(6) "strpos"
 int(123)
 string(6) "strpos"

Zend/tests/type_declarations/intersection_types/implicit_nullable_intersection_type.phpt

@@ -10,5 +10,6 @@ function foo(X&Y $foo = null) {
 foo(null);
 
 ?>
---EXPECT--
+--EXPECTF--
+Deprecated: Implicitly marking parameter $foo as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 NULL

Zend/tests/type_declarations/intersection_types/implicit_nullable_intersection_type_error.phpt

@@ -15,4 +15,5 @@ try {
 
 ?>
 --EXPECTF--
+Deprecated: Implicitly marking parameter $foo as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 foo(): Argument #1 ($foo) must be of type (X&Y)|null, int given, called in %s on line %d

Zend/tests/type_declarations/iterable/iterable_002.phpt

@@ -17,4 +17,6 @@ function baz(iterable $iterable = 1) {
 
 ?>
 --EXPECTF--
+Deprecated: Implicitly marking parameter $iterable as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
+
 Fatal error: Cannot use int as default value for parameter $iterable of type Traversable|array in %s on line %d

Zend/tests/type_declarations/literal_types/false_standalone_implicit_nullability.phpt

@@ -8,6 +8,7 @@ function test(false $v = null) { return $v; }
 var_dump(test(false));
 var_dump(test(null));
 ?>
---EXPECT--
+--EXPECTF--
+Deprecated: Implicitly marking parameter $v as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 bool(false)
 NULL

Zend/tests/type_declarations/literal_types/true_standalone_implicit_nullability.phpt

@@ -8,6 +8,7 @@ function test(true $v = null) { return $v; }
 var_dump(test(true));
 var_dump(test(null));
 ?>
---EXPECT--
+--EXPECTF--
+Deprecated: Implicitly marking parameter $v as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 bool(true)
 NULL

Zend/tests/type_declarations/nullable_null.phpt

@@ -7,5 +7,6 @@ function test(Foo $a = null) {
 }
 test(null);
 ?>
---EXPECT--
+--EXPECTF--
+Deprecated: Implicitly marking parameter $a as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 ok

Zend/tests/type_declarations/scalar_none.phpt

@@ -8,10 +8,10 @@ $functions = [
     'float' => function (float $f) { return $f; },
     'string' => function (string $s) { return $s; },
     'bool' => function (bool $b) { return $b; },
-    'int nullable' => function (int $i = NULL) { return $i; },
-    'float nullable' => function (float $f = NULL) { return $f; },
-    'string nullable' => function (string $s = NULL) { return $s; },
-    'bool nullable' => function (bool $b = NULL) { return $b; }
+    'int nullable' => function (?int $i = NULL) { return $i; },
+    'float nullable' => function (?float $f = NULL) { return $f; },
+    'string nullable' => function (?string $s = NULL) { return $s; },
+    'bool nullable' => function (?bool $b = NULL) { return $b; }
 ];
 
 foreach ($functions as $type => $function) {

Zend/tests/type_declarations/scalar_null.phpt

@@ -8,10 +8,10 @@ $functions = [
     'float' => function (float $f) { return $f; },
     'string' => function (string $s) { return $s; },
     'bool' => function (bool $b) { return $b; },
-    'int nullable' => function (int $i = NULL) { return $i; },
-    'float nullable' => function (float $f = NULL) { return $f; },
-    'string nullable' => function (string $s = NULL) { return $s; },
-    'bool nullable' => function (bool $b = NULL) { return $b; }
+    'int nullable' => function (?int $i) { return $i; },
+    'float nullable' => function (?float $f) { return $f; },
+    'string nullable' => function (?string $s) { return $s; },
+    'bool nullable' => function (?bool $b) { return $b; }
 ];
 
 foreach ($functions as $type => $function) {

Zend/tests/type_declarations/variance/internal_parent/unresolvable_inheritance_check_param.phpt

@@ -4,7 +4,7 @@ Test unresolvable inheritance check due to unavailable parameter type when the p
 <?php
 
 class Test extends DateTime {
-    public static function createFromFormat($format, $datetime, Wrong $timezone = null): DateTime|false {}
+    public static function createFromFormat($format, $datetime, ?Wrong $timezone = null): DateTime|false {}
 }
 
 ?>

Zend/tests/variadic/adding_additional_optional_parameter.phpt

@@ -8,10 +8,10 @@ interface DB {
 }
 
 class MySQL implements DB {
-    public function query($query, string $extraParam = null, string ...$params) { }
+    public function query($query, ?string $extraParam = null, string ...$params) { }
 }
 
 ?>
 ===DONE===
---EXPECT--
+--EXPECTF--
 ===DONE===

Zend/tests/variadic/adding_additional_optional_parameter_error.phpt

@@ -8,7 +8,7 @@ interface DB {
 }
 
 class MySQL implements DB {
-    public function query($query, int $extraParam = null, string ...$params) { }
+    public function query($query, ?int $extraParam = null, string ...$params) { }
 }
 
 ?>

Zend/zend_compile.c

@@ -7224,6 +7224,11 @@ static void zend_compile_params(zend_ast *ast, zend_ast *return_type_ast, uint32
 
 			op_array->fn_flags |= ZEND_ACC_HAS_TYPE_HINTS;
 			arg_info->type = zend_compile_typename_ex(type_ast, force_nullable, &forced_allow_nullable);
+			if (forced_allow_nullable) {
+				zend_error(E_DEPRECATED,
+				   "Implicitly marking parameter $%s as nullable is deprecated, the explicit nullable type "
+				   "must be used instead", ZSTR_VAL(name));
+			}
 
 			if (ZEND_TYPE_FULL_MASK(arg_info->type) & MAY_BE_VOID) {
 				zend_error_noreturn(E_COMPILE_ERROR, "void cannot be used as a parameter type");

ext/date/tests/DateTime_extends_basic2.phpt

@@ -10,7 +10,7 @@ echo "*** Testing new DateTime() : with user space __construct magic method ***\
 
 class DateTimeExt extends DateTime
 {
-    public function __construct ($date = null, DateTimeZone  $dtz = null)
+    public function __construct ($date = null, ?DateTimeZone $dtz = null)
     {
         if($dtz === null)
         {

ext/date/tests/bug55407.phpt

@@ -6,7 +6,7 @@ error_reporting=-1
 <?php namespace melt\core;
 
 class DateTime extends \DateTime {
-    public static function createFromFormat($format, $time, \DateTimeZone $timezone = null): DateTime|false {
+    public static function createFromFormat($format, $time, ?\DateTimeZone $timezone = null): DateTime|false {
         return new DateTime(parent::createFromFormat($format, $time, $timezone));
     }
 }

ext/opcache/tests/bug73746.phpt

@@ -11,7 +11,7 @@ class CountryMapping
     const CZ = 'CZ';
     const EN = 'EN';
 
-    public function get(string $countryIsoCode = null) : string // Works correctly if return type is removed
+    public function get(?string $countryIsoCode = null) : string // Works correctly if return type is removed
     {
         switch (strtoupper($countryIsoCode)) {
         case 'CZ':

ext/opcache/tests/bug74442.phpt

@@ -7,14 +7,14 @@ opcache
 --FILE--
 <?php
 class Schema_Base {
-    public function addField($typeclass, array $params = null) {
+    public function addField($typeclass, ?array $params = null) {
         $field = new $typeclass($params);
         return $field;
     }
 }
 
 class Field_Base {
-    public function __construct(array $params = null) {
+    public function __construct(?array $params = null) {
         if (! is_array($params)) {
             $params = (array) $params;
         }

ext/opcache/tests/invalid_array_key_type.phpt

@@ -5,7 +5,7 @@ opcache
 --FILE--
 <?php
 
-function test(\SplObjectStorage $definitions = null) {
+function test(?\SplObjectStorage $definitions = null) {
     $argument = new stdClass;
     $definitions[$argument] = 1;
     $definitions[$argument] += 1;

ext/opcache/tests/jit/cast_001.phpt

@@ -10,7 +10,7 @@ opcache.jit=1205
 opcache
 --FILE--
 <?php
-function foo (int $x = null) {
+function foo (?int $x = null) {
     $a = (array)$x;
     $a[] = 42;
     var_dump($a);

ext/opcache/tests/jit/send_var_ex_002.phpt

@@ -12,7 +12,7 @@ for ($i = 0; $i < 3; $i++ ) {
 	var_dump($x);
 }	
 
-function test(&$a = null, SomeType &$b = null) {
+function test(&$a = null, ?SomeType &$b = null) {
     $a++;
 }
 ?>

ext/opcache/tests/opt/assign_op_002.phpt

@@ -6,7 +6,7 @@ opcache.enable_cli=1
 opcache.optimization_level=-1
 --FILE--
 <?php
-function foo(int $a = null) {
+function foo(?int $a = null) {
     $a -= 1;
     return $a;
 }

ext/pdo_pgsql/tests/bug72294.phpt

@@ -27,7 +27,7 @@ abstract class PHPUnit_Framework_TestCase
     private $name = null;
     private $result;
 
-    public function run(PHPUnit_Framework_TestResult $result = null)
+    public function run(?PHPUnit_Framework_TestResult $result = null)
     {
         $result->run($this);
     }

ext/reflection/tests/ReflectionClass_export_basic1.phpt

@@ -6,7 +6,7 @@ Class A {
     public function privf(Exception $a) {}
     public function pubf(A $a,
                          $b,
-                         C $c = null,
+                         ?C $c = null,
                          $d = K,
                          $e = "15 chars long -",
                          $f = null,
@@ -20,6 +20,7 @@ define('K', "16 chars long --");
 echo new ReflectionClass("C"), "\n";
 ?>
 --EXPECTF--
+Deprecated: Implicitly marking parameter $h as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 Class [ <user> class C extends A ] {
   @@ %s 14-14
 

ext/reflection/tests/bug62715.phpt

@@ -3,7 +3,7 @@ Bug #62715 (ReflectionParameter::isDefaultValueAvailable() wrong result)
 --FILE--
 <?php
 
-function test(PDO $a = null, $b = 0, array $c) {}
+function test(?PDO $a = null, $b = 0, array $c) {}
 $r = new ReflectionFunction('test');
 
 foreach ($r->getParameters() as $p) {
@@ -17,6 +17,8 @@ foreach ($r->getParameters() as $p) {
 }
 ?>
 --EXPECTF--
+Deprecated: Optional parameter $a declared before required parameter $c is implicitly treated as a required parameter in %s on line %d
+
 Deprecated: Optional parameter $b declared before required parameter $c is implicitly treated as a required parameter in %s on line %d
 bool(false)
 bool(false)

ext/reflection/tests/parameters_002.phpt

@@ -11,7 +11,7 @@ function test($nix, Array $ar, &$ref, stdClass $std,
 class test
 {
     function method($nix, Array $ar, &$ref, stdClass $std,
-        NonExistingClass $na, stdClass $opt = NULL, $def = "FooBar")
+        NonExistingClass $na, ?stdClass $opt = NULL, $def = "FooBar")
     {
     }
 }
@@ -73,6 +73,7 @@ check_params(ReflectionMethod::createFromMethodName('test::method'));
 
 ?>
 --EXPECTF--
+Deprecated: Implicitly marking parameter $opt as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 #####test()#####
 ===0===
 getName: string(3) "nix"

ext/reflection/tests/types/ReflectionType_001.phpt

@@ -100,7 +100,8 @@ $obj->std = new stdClass;
 $r = (new ReflectionProperty($obj, 'std'))->getType();
 var_dump($r->getName());
 ?>
---EXPECT--
+--EXPECTF--
+Deprecated: Implicitly marking parameter $d as nullable is deprecated, the explicit nullable type must be used instead in %s on line %d
 *** functions
 ** Function 0 - Parameter 0
 bool(true)