added test

Author: staabm

tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php

@@ -2718,9 +2718,16 @@ public function testBug11534(): void
 		$this->analyse([__DIR__ . '/data/bug-11534.php'], [
 			[
 				'Parameter #2 $param2 of function Bug11534\hello expects int, mixed given.',
-				14
-			]
+				14,
+			],
 		]);
 	}
 
+	public function testBug10559(): void
+	{
+		$this->checkExplicitMixed = true;
+		$this->checkImplicitMixed = true;
+		$this->analyse([__DIR__ . '/data/bug-10559.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Functions/data/bug-10559.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Bug10559;
+
+/** @var mixed[] $arr1 */
+$arr1 = [
+	'a1' => 1,
+	'b1' => '2',
+	'c1' => 3.3,
+];
+// There is no error
+echo (string)$arr1['c1'];
+
+
+/** @var mixed[] $arr2 */
+$arr2 = [
+	'a1' => 1,
+	'b1' => '2',
+	'c1' => 3.3,
+];
+if ($arr2['a1'] > 1) {}
+// !!! There is error "Cannot cast mixed to string." on next line if "checkImplicitMixed: true"
+echo (string)$arr2['c1'];