nullable_type_declaration_for_default_null_value fails for nullable readonly parameter in promoted constructor

[krzysztofrewak]

I think NullableTypeDeclarationForDefaultNullValueFixer crashes when I'm trying to add readonly modifier to nullable parameter in promoted constructor.

Bug report

• PHP version: PHP 8.1.0 (cli) (built: Nov 30 2021 07:26:16) (NTS)
• PHP CS Fixer version: PHP CS Fixer 3.4.0 Si! by Fabien Potencier and Dariusz Ruminski
• the command used to run PHP CS Fixer (run with -vvv):

PHP CS Fixer 3.4.0 Si! by Fabien Potencier and Dariusz Ruminski
Runtime: PHP 8.1.0
Loaded config default.
Using cache file ".php-cs-fixer.cache".
E                                                                                                                                                                                                                                                                                                           1 / 1 (100%)
Legend: ?-unknown, I-invalid file syntax (file ignored), S-skipped (cached or empty file), .-no changes, F-fixed, E-error

Fixed all files in 0.004 seconds, 12.000 MB memory used

Files that were not fixed due to errors reported during linting after fixing:
   1) /application/src/ReadonlyThing.php

                                                                            
        [PhpCsFixer\Linter\LintingException]                                
        Parse error: syntax error, unexpected token "readonly" on line 11.  
                                                                            

      Applied fixers: nullable_type_declaration_for_default_null_value
ERROR: 64

• the configuration (file) you used: none

Code snippet that reproduces the problem

<?php

class ReadonlyThing
{
    public function __construct(
        protected readonly bool $nullable = null,
    ) {
    }
}

Expected output

<?php

class ReadonlyThing
{
    public function __construct(
        protected readonly ?bool $nullable = null,
    ) {
    }
}

Btw. when it's used with easy-coding-standard, it's even worse:

<?php

class ReadonlyThing
{
    public function __construct(
        protected ?readonly ?bool $nullable = null,
    ) {
    }
}

[SpacePossum]

Thanks for reporting this issue to us.

Looking at your example I wonder why the tool tries to fix the code as it does not lint:

$ sudo docker-compose run --rm --user "$(id --user):$(id --group)" php php -l test2.php
Fatal error: Cannot use null as default value for parameter $nullable of type bool in test2.php on line 5

$ sudo docker-compose run --rm --user "$(id --user):$(id --group)" php php -v
PHP 8.1.0 (cli) (built: Dec  2 2021 12:47:04) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.1.0, Copyright (c) Zend Technologies

[SpacePossum]

to clarify; it does "fix" the following correct PHP incorrectly so there is indeed a bug in the tool

<?php
class Foo
{
    public function __construct(
        protected readonly ?bool $nullable = null,
    ) {}
}