MissingConstructor

Unitialized properties are statically hard to analyze. To prevent mistakes, Psalm will enforce that all properties should be initialized.

It does that through PropertyNotSetInConstructor and this issue.

Psalm will then assume every property in the codebase is initialized.

Doing that allows it to report missing initializations as well as RedundantPropertyInitializationCheck

This issue is emitted when non-null properties without default values are defined in a class without a __construct method

If your project relies on having uninitialized properties, it is advised to suppress this issue, as well as PropertyNotSetInConstructor and RedundantPropertyInitializationCheck.

<?php

class A {
    /** @var string */
    public $foo;
}