Fix preg_match() group containing start/end meta characters

Author: staabm

src/Type/Regex/RegexGroupParser.php

@@ -527,7 +527,7 @@ private function isMaybeEmptyNode(TreeNode $node, string $patternModifiers, bool
 			if ($literal !== '' && $literal !== '0') {
 				$isNonFalsy = true;
 			}
-			return false;
+			return $literal === '';
 		}
 
 		foreach ($node->getChildren() as $child) {

tests/PHPStan/Analyser/nsrt/bug-12297.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Bug12297;
+
+use function PHPStan\Testing\assertType;
+
+function doFoo($s) {
+	if (preg_match('/(^.+)/', $s, $matches) === 1) {
+		assertType('non-empty-string', $matches[1]);
+	}
+
+	if (preg_match('/(.+$)/', $s, $matches) === 1) {
+		assertType('non-empty-string', $matches[1]);
+	}
+
+	if (preg_match('/(^.+$)/', $s, $matches) === 1) {
+		assertType('non-empty-string', $matches[1]);
+	}
+}