Psalm emits InaccessibleProperty and RedundantPropertyInitializationCheck for checks and mutating code in the "__wakeup"

[andrew-demb]

Discussed in #10180

^{Originally posted by andrew-demb September 5, 2023}
https://psalm.dev/r/0b9d93cacf

<?php

/**
 * @psalm-immutable
 */
class Some
{
    // it was a `?string $locale` in past
    private string $locale;
    
    public function __construct(
        string $locale,
    ) {
        $this->locale = $locale;
    }

    public function __wakeup(): void
    {
    	// it was a `?string $locale` in past
        if (false === isset($this->locale)) {
            $this->locale = '';
        }
    }
}

Psalm output (using commit [37cc4fd](https://github.com/vimeo/psalm/commit/37cc4fd)): 

ERROR: [RedundantPropertyInitializationCheck](https://psalm.dev/261) - 20:13 - Property $this->locale with type string should already be set in the constructor

ERROR: [InaccessibleProperty](https://psalm.dev/054) - 21:13 - Some::$locale is marked readonly

What's the proper way to handle it?
Suppress both issues or psalm may allow such a checks and updates for magic method like a __wakeup?

As of #10180 (comment) - the current issue requests for a feature in Psalm - don't emit such errors for code like above in the __wakeup.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/0b9d93cacf

<?php

/**
 * @psalm-immutable
 */
class Some
{
    // it was a `?string $locale` in past
    private string $locale;
    
    public function __construct(
        string $locale,
    ) {
        $this->locale = $locale;
    }

    public function __wakeup(): void
    {
    	// it was a `?string $locale` in past
        if (false === isset($this->locale)) {
            $this->locale = '';
        }
    }
}

Psalm output (using commit 37cc4fd):

ERROR: RedundantPropertyInitializationCheck - 20:13 - Property $this->locale with type string should already be set in the constructor

ERROR: InaccessibleProperty - 21:13 - Some::$locale is marked readonly