Add test for unknown named parameters on native variadic functions

Adds a regression test for #14408 verifying that unknown named arguments
passed to native variadic functions like sprintf() are properly detected.

Author: Amoifr

tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php

@@ -545,6 +545,20 @@ public function testBugNumberFormatNamedArguments(): void
 		$this->analyse([__DIR__ . '/data/number-format-named-arguments.php'], []);
 	}
 
+	public function testBug14408(): void
+	{
+		if (PHP_VERSION_ID < 80000) {
+			$this->markTestSkipped('Test requires PHP 8.0');
+		}
+
+		$this->analyse([__DIR__ . '/data/bug-14408.php'], [
+			[
+				'Unknown parameter $foo in call to function sprintf.',
+				6,
+			],
+		]);
+	}
+
 	public function testArrayReduceCallback(): void
 	{
 		$this->analyse([__DIR__ . '/data/array_reduce.php'], [

tests/PHPStan/Rules/Functions/data/bug-14408.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace Bug14408;
+
+// This should report an error: sprintf does not accept unknown named parameters
+sprintf(format: '%s', foo: 'bar');
+
+// This should be fine: named parameter matches the signature
+sprintf(format: '%s %s', values: 'hello');
+
+// call_user_func should accept unknown named args (forwards to callback)
+call_user_func('strtolower', str: 'HELLO');