Add test

Author: VincentLanglet

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -88,6 +88,7 @@ private static function findTestFiles(): iterable
 		yield __DIR__ . '/../Rules/Variables/data/bug-10577.php';
 		yield __DIR__ . '/../Rules/Variables/data/bug-10610.php';
 		yield __DIR__ . '/../Rules/Comparison/data/bug-2550.php';
+		yield __DIR__ . '/../Rules/Comparison/data/bug-12412.php';
 		yield __DIR__ . '/../Rules/Properties/data/bug-3777.php';
 		yield __DIR__ . '/../Rules/Methods/data/bug-4552.php';
 		yield __DIR__ . '/../Rules/Methods/data/infer-array-key.php';

tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php

@@ -999,4 +999,10 @@ public function testBug12755(): void
 		$this->analyse([__DIR__ . '/data/bug-12755.php'], []);
 	}
 
+	public function testBug12412(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-12412.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-12412.php

@@ -0,0 +1,26 @@
+<?php declare(strict_types = 1);
+
+namespace Bug12412;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @param 'A'|'B' $type
+ * @return list<string>
+ */
+function f(string $type): array {
+	$field_list = [ ];
+	if ($type === 'A') {
+		array_push($field_list, 'x1');
+	}
+	if ($type === 'B') {
+		array_push($field_list, 'x2');
+	}
+
+	assertType('bool', in_array('x1', $field_list, true));
+
+	array_push($field_list, 'x3');
+	assertType('bool', in_array('x1', $field_list, true));
+
+	return $field_list;
+}