Added regression test

Author: staabm

tests/PHPStan/Analyser/nsrt/bug-13039.php

@@ -0,0 +1,21 @@
+<?php declare(strict_types=1);
+
+namespace Bug13039;
+
+use function PHPStan\Testing\assertType;
+
+function doFoo() {
+	/** @var list<array<string, mixed>> */
+	$transactions = [];
+
+	assertType('list<array<string, mixed>>', $transactions);
+
+	foreach (array_keys($transactions) as $k) {
+		$transactions[$k]['Shares'] = [];
+		$transactions[$k]['Shares']['Projects'] = [];
+		$transactions[$k]['Shares']['People'] = [];
+	}
+
+	assertType('list<array<string, mixed>>', $transactions);
+}
+