Add a failing unit test to reproduce #52

tests/Type/Php/TypeAssertionsTest.php

@@ -13,6 +13,7 @@ public static function dataFileAsserts(): iterable
     {
         yield from self::gatherAssertTypes(__DIR__ . '/data/preg_match_unchecked.php');
         yield from self::gatherAssertTypes(__DIR__ . '/data/preg_match_checked.php');
+        yield from self::gatherAssertTypes(__DIR__ . '/data/preg_match_asserted.php');
         yield from self::gatherAssertTypes(__DIR__ . '/data/preg_replace_return.php');
     }
 

tests/Type/Php/data/preg_match_asserted.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace TheCodingMachine\Safe\PHPStan\Type\Php\data;
+
+// Checking that preg_match and Safe\preg_match are equivalent
+$pattern = '/H(.)ll(o) (World)?/';
+$string = 'Hello World';
+
+// when the return value is checked, we should have matches,
+// unless the match-group itself is optional
+$type = "array{0: string, 1: non-empty-string, 2: 'o', 3?: 'World'}";
+
+// @phpstan-ignore-next-line - use of unsafe is intentional
+$ret = \preg_match($pattern, $string, $matches);
+assert($ret === 1);
+\PHPStan\Testing\assertType($type, $matches);
+
+$ret = \Safe\preg_match($pattern, $string, $matches);
+assert($ret === 1);
+\PHPStan\Testing\assertType($type, $matches);