add regression test for phpstan/phpstan#5971 and phpstan/phpstan#6107

tests/PHPStan/Rules/DeadCode/UnusedPrivatePropertyRuleTest.php

@@ -241,4 +241,26 @@ public function testBug5337(): void
 		$this->analyse([__DIR__ . '/data/bug-5337.php'], []);
 	}
 
+	public function testBug5971(): void
+	{
+		if (PHP_VERSION_ID < 70400) {
+			$this->markTestSkipped('Test requires PHP 7.4.');
+		}
+
+		$this->alwaysWrittenTags = [];
+		$this->alwaysReadTags = [];
+		$this->analyse([__DIR__ . '/data/bug-5971.php'], []);
+	}
+
+	public function testBug6107(): void
+	{
+		if (PHP_VERSION_ID < 70400) {
+			$this->markTestSkipped('Test requires PHP 7.4.');
+		}
+
+		$this->alwaysWrittenTags = [];
+		$this->alwaysReadTags = [];
+		$this->analyse([__DIR__ . '/data/bug-6107.php'], []);
+	}
+
 }

tests/PHPStan/Rules/DeadCode/data/bug-5971.php

@@ -0,0 +1,33 @@
+<?php declare(strict_types = 1); // lint >= 7.4
+
+namespace Bug5971;
+
+class TestEmpty
+{
+	private ?array $test;
+
+	public function write(): void
+	{
+		$this->test = [];
+	}
+
+	public function read(): bool
+	{
+		return empty($this->test);
+	}
+}
+
+class TestIsset
+{
+	private ?string $test;
+
+	public function write(string $string): void
+	{
+		$this->test = $string;
+	}
+
+	public function read(): bool
+	{
+		return isset($this->test);
+	}
+}

tests/PHPStan/Rules/DeadCode/data/bug-6107.php

@@ -0,0 +1,18 @@
+<?php declare(strict_types = 1); // lint >= 7.4
+
+namespace Bug6107;
+
+class Test
+{
+	private ?\stdClass $item;
+
+	public function __construct(?\stdClass $item)
+	{
+		$this->item = $item;
+	}
+
+	public function handle(): void
+	{
+		$value = $this->item->value ?? 'custom value';
+	}
+}