Update bug-13857.php

Author: staabm

tests/PHPStan/Analyser/nsrt/bug-13857.php

@@ -11,6 +11,7 @@
  */
 function test(array $array, int $id): void {
 	$array[$id]['state'] = 'foo';
+	// only one element was set to 'foo', not all of them.
 	assertType("non-empty-array<int, array{state: 'foo'}>", $array);
 }
 
@@ -19,6 +20,7 @@ function test(array $array, int $id): void {
  */
 function testMaybe(array $array, int $id): void {
 	$array[$id]['state'] = 'foo';
+	// only one element was set to 'foo', not all of them.
 	assertType("non-empty-array<int, array{state: 'foo'}>", $array);
 }
 
@@ -27,6 +29,7 @@ function testMaybe(array $array, int $id): void {
  */
 function testUnionValue(array $array, int $id): void {
 	$array[$id]['state'] = 'foo';
+	// only one element was set to 'foo', not all of them.
 	assertType("non-empty-array<int, array{state: 'foo'}>", $array);
 }
 
@@ -35,6 +38,7 @@ function testUnionValue(array $array, int $id): void {
  */
 function testUnionArray(array $array, int $id): void {
 	$array[$id]['state'] = 'foo';
+	// only one element was set to 'foo', not all of them.
 	assertType("non-empty-array<int, array{foo?: int, state: 'foo'}>", $array);
 }