added inverse test

Author: staabm

tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php

@@ -1168,11 +1168,11 @@ public function testBug13770(): void
 		$this->analyse([__DIR__ . '/data/bug-13770.php'], [
 			[
 				'Offset int<1, max> might not exist on non-empty-list<int>.',
-				40,
+				53,
 			],
 			[
 				'Offset int might not exist on list<int>.',
-				53,
+				66,
 			],
 		]);
 	}

tests/PHPStan/Rules/Arrays/data/bug-13770.php

@@ -17,6 +17,19 @@ public function positiveIntLessThanCount(array $array, int $index): int
 		return 0;
 	}
 
+	/**
+	 * @param list<int> $array
+	 * @param positive-int $index
+	 */
+	public function positiveIntLessThanCountInversed(array $array, int $index): int
+	{
+		if (count($array) > $index) {
+			return $array[$index]; // should not report
+		}
+
+		return 0;
+	}
+
 	/**
 	 * @param list<int> $array
 	 * @param int<0, max> $index