Regression test

Closes phpstan/phpstan#8938

Author: ondrejmirtes

Diff for: tests/PHPStan/Rules/Comparison/NumberComparisonOperatorsConstantConditionRuleTest.php

@@ -207,4 +207,10 @@ public function testBug7075(): void
 		$this->analyse([__DIR__ . '/data/bug-7075.php'], []);
 	}
 
+	public function testBug8938(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-8938.php'], []);
+	}
+
 }

Diff for: tests/PHPStan/Rules/Comparison/data/bug-8938.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Bug8938;
+
+class HelloWorld
+{
+	public function processData(string $data): string
+	{
+		$returnValue = '';
+		while (strlen($data) > 0) {
+			$firstChar = substr($data, 0, 1);
+			$data = substr($data, 1);
+			$returnValue = $returnValue . $firstChar;
+		}
+		return $returnValue;
+	}
+}