Fix always-true detection in in_array with union type haystack

Author: sayuprc

src/Rules/Comparison/ImpossibleCheckTypeHelper.php

@@ -148,6 +148,10 @@ public function findSpecifiedType(
 							foreach ($haystackArrayTypes as $haystackArrayType) {
 								if ($haystackArrayType instanceof ConstantArrayType) {
 									foreach ($haystackArrayType->getValueTypes() as $i => $haystackArrayValueType) {
+										if ($haystackArrayValueType instanceof UnionType) {
+											continue;
+										}
+
 										if ($haystackArrayType->isOptionalKey($i)) {
 											continue;
 										}

tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php

@@ -1004,4 +1004,10 @@ public function testBugPR3404(): void
 		]);
 	}
 
+	public function testBug12755(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-12755.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-12755.php

@@ -0,0 +1,35 @@
+<?php declare(strict_types = 1);
+
+namespace Bug12755;
+
+class HelloWorld
+{
+	/**
+	 * @param array{
+	 *     key1: ?int,
+	 *     key2: ?string,
+	 * } $myArray
+	 */
+	public function testOther(array $myArray): ?\stdClass
+	{
+	    if (\in_array(null, $myArray, true)) {
+	        return null;
+	    }
+
+		return (object) $myArray;
+	}
+		
+	/**
+	 * @param array{
+	 *     key1: ?bool,
+	 * } $myArray
+	 */
+	public function testBool(array $myArray): ?\stdClass
+	{
+	    if (\in_array(null, $myArray, true)) {
+	        return null;
+	    }
+
+		return (object) $myArray;
+	}
+}