UnionType.php

<?php
 
namespace DaveRandom\CallbackValidator\Type;
 
use function array_shift;
use function assert;
use function count;
 
final class UnionType implements BaseType{
    public function __construct(
        public readonly array $types,
    ){}
 
    public function stringify(int $depth = 0) : string{
        if(count($this->types) === 2){
            //simplify nullable types with ?Type
            foreach($this->types as $k => $type){
                if($type instanceof NamedType && $type->type === BuiltInType::NULL){
                    $types = $this->types;
                    unset($types[$k]);
                    $remaining = array_shift($types);
                    assert($remaining !== null);
                    return '?' . $remaining->stringify($depth + 1);
                }
            }
        }
 
        $result = implode('|', array_map(fn($type) => $type->stringify($depth + 1), $this->types));
        return $depth === 0 ? $result : "($result)";
    }
}