Not respecting previous null check

[allejo]

Bug report

It looks like null checks that happen previous and cause an exit from a function are ignored. i.e. After the null check, the variable is still considered "nullable."

Code snippet that reproduces the problem

<?php declare(strict_types = 1);

class Sample {
	/** @var null|array<string, string> */
	private $arr = null;
	
	public function test(): void {
		if ($this->arr === null) {
			return;
		}
		
		unset($this->arr['hello']);
		
		if (count($this->arr) === 0) {
			$this->arr = null;
		}
	}
}

https://phpstan.org/r/a79d1e2f-932f-4c40-8e92-530baa0a3fb8

Expected output

This should work the same and not require an explicit null check like so,

if ($this->arr !== null && count($this->arr) === 0) {
    $this->arr = null;
}

[phpstan-bot]

@allejo After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-PHP 8.0 (1 error)
-==========
-
-14: Parameter #1 $value of function count expects array|Countable, array<string, string>|null given.
-
-PHP 7.1 – 7.4 (1 error)
-==========
-
-14: Parameter #1 $var of function count expects array|Countable, array<string, string>|null given.
+No errors

[github-actions]

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