Added regression test

Author: staabm

tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php

@@ -1054,4 +1054,18 @@ public function testBug12087(): void
 		]);
 	}
 
+	public function testBug9666(): void
+	{
+		$tipText = 'Because the type is coming from a PHPDoc, you can turn off this check by setting <fg=cyan>treatPhpDocTypesAsCertain: false</> in your <fg=cyan>%configurationFile%</>.';
+
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-9666.php'], [
+			[
+				'Call to function is_bool() with bool will always evaluate to true.',
+				20,
+				$tipText,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-9666.php

@@ -0,0 +1,24 @@
+<?php declare(strict_types=1);
+
+namespace Bug9666;
+
+class A
+{
+	/**
+	 * @return array<int,bool>
+	 */
+	function b()
+	{
+		return [];
+	}
+}
+
+function doFoo() {
+	$a = new A();
+	$b = $a->b();
+	$c = null;
+	if ($b && is_bool($c = reset($b))) {
+		//
+	}
+}
+