Fixed fatal error when checking class existence with leading backslash

src/Broker/Broker.php

@@ -349,11 +349,13 @@ public function getClassFromReflection(\ReflectionClass $reflectionClass, string
 
 	public function hasClass(string $className): bool
 	{
+		$className = trim($className, '\\');
 		if (isset($this->hasClassCache[$className])) {
 			return $this->hasClassCache[$className];
 		}
 
 		spl_autoload_register($autoloader = function (string $autoloadedClassName) use ($className): void {
+			$autoloadedClassName = trim($autoloadedClassName, '\\');
 			if ($autoloadedClassName !== $className && !$this->isExistsCheckCall()) {
 				throw new \PHPStan\Broker\ClassAutoloadingException($autoloadedClassName);
 			}

tests/PHPStan/Analyser/AnalyserIntegrationTest.php

@@ -171,6 +171,14 @@ public function testNestedNamespaces(): void
 		$this->assertSame(13, $errors[0]->getLine());
 	}
 
+	public function testClassExistsAutoloadingError(): void
+	{
+		$errors = $this->runAnalyse(__DIR__ . '/data/class-exists.php');
+		$this->assertCount(1, $errors);
+		$this->assertSame('Instantiated class \PHPStan\GitHubIssue2359 not found.', $errors[0]->getMessage());
+		$this->assertSame(12, $errors[0]->getLine());
+	}
+
 	/**
 	 * @param string $file
 	 * @return \PHPStan\Analyser\Error[]

tests/PHPStan/Analyser/data/class-exists.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace ClassExistsAutoloadingError;
+
+class Foo
+{
+
+	public function doFoo()
+	{
+		$className = '\PHPStan\GitHubIssue2359';
+		if (class_exists($className)) {
+			var_dump(new $className());
+		}
+	}
+
+}