fix

Author: staabm

src/Analyser/TypeSpecifier.php

@@ -708,10 +708,9 @@ public function specifyTypesInCondition(
 						&& ($numArg === null || $one->isSuperTypeOf($scope->getType($numArg))->yes())
 					) {
 						$dimFetch = new ArrayDimFetch($arrayArg, $expr->var);
-						$iterableValueType = $arrayType->getFirstIterableValueType();
 
 						return $specifiedTypes->unionWith(
-							$this->create($dimFetch, $iterableValueType, TypeSpecifierContext::createTrue(), $scope),
+							$this->create($dimFetch, $arrayType->getIterableValueType(), TypeSpecifierContext::createTrue(), $scope),
 						);
 					}
 				}

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -69,6 +69,7 @@ private static function findTestFiles(): iterable
 		}
 
 		yield __DIR__ . '/../Rules/Methods/data/bug-6856.php';
+		yield __DIR__ . '/../Rules/Arrays/data/bug-12981.php';
 
 		if (PHP_VERSION_ID < 80000) {
 			yield __DIR__ . '/data/explode-php74.php';

tests/PHPStan/Rules/Arrays/data/bug-12981.php

@@ -12,6 +12,7 @@ public function sayHello(array $arr): void
 	{
 		echo $arr[array_rand($arr)];
 		$randIndex = array_rand($arr);
+		assertType('bool|float|int|string', $arr[$randIndex]);
 		echo $arr[$randIndex];
 	}
 
@@ -40,4 +41,21 @@ public function sayHello4(array $arr, int $num): void
 		$randIndex = array_rand($arr, $num);
 		echo $arr[$randIndex];
 	}
+
+	public function sayHello5(): void
+	{
+		$arr = [
+			1 => true,
+			2 => false,
+			'a' => 'hello',
+		];
+		assertType("'hello'|bool", $arr[array_rand($arr)]);
+
+		$arr = [
+			1 => true,
+			2 => null,
+			'a' => 'hello',
+		];
+		assertType("'hello'|true|null", $arr[array_rand($arr)]);
+	}
 }