Printer: fixed combination nullable + mixed [Closes #74]

Author: dg

src/PhpGenerator/Printer.php

@@ -293,7 +293,7 @@ public function printType(?string $type, bool $nullable = false, PhpNamespace $n
 		if ($this->resolveTypes && $namespace) {
 			$type = $namespace->unresolveUnionType($type);
 		}
-		if ($nullable) {
+		if ($nullable && strcasecmp($type, 'mixed')) {
 			$type = strpos('|', $type) === false
 				? '?' . $type
 				: $type . '|null';

tests/PhpGenerator/expected/ClassType.from.80.expect

@@ -39,7 +39,7 @@ class Class10
 	public string|int $prop;
 
 
-	public function test(string|int $param): string|int
+	public function test(mixed $param): string|int
 	{
 	}
 }

tests/PhpGenerator/fixtures/classes.php80

@@ -44,7 +44,7 @@ class Class10
 {
 	public string|int $prop;
 
-	function test(string|int $param): string|int
+	function test(mixed $param): string|int
 	{
 	}
 }