Added non-regression test (#5260)

Author: staabm

tests/PHPStan/Analyser/nsrt/reset-after-non-empty-loop.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace ResetAfterNonEmptyLoop;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @param list<string> $joins
+ */
+function mergeJoins(array $joins, string $s, string $hash): void
+{
+	if (count($joins) === 0) return;
+	assertType('non-empty-list<string>', $joins);
+
+	/** @var array<array<string>> $aggregated */
+	$aggregated = [];
+	foreach ($joins as $join) {
+		$aggregated[$s][$hash] = $s;
+	}
+	assertType('non-empty-array<non-empty-array<string>>', $aggregated);
+
+	foreach ($aggregated as $sameJoins) {
+		$first = reset($sameJoins);
+		assertType('string', $first);
+	}
+}