Psalm - a static analysis tool for PHP

<?php
declare(strict_types=1);

namespace Snippet;

use Iterator;
use IteratorAggregate;
use function array_key_exists;
use function count;
use function PHPStan\Testing\assertType;

/**
 * @template T
 */
interface TypeGenerator
{
    /**
     * @return T
     */
    public function __invoke();
}

/**
 * @implements TypeGenerator<int>
 */
final class IntType implements TypeGenerator
{
    public function __invoke(): int
    {
        return mt_rand(0, 9);
    }
}

/**
 * @implements TypeGenerator<string>
 */
final class StringType implements TypeGenerator
{
    public function __invoke(): string
    {
        return chr(random_int(33, 126));
    }
}

/**
 * @implements TypeGenerator<null>
 */
final class NullType implements TypeGenerator
{
    public function __invoke()
    {
        return null;
    }
}

/**
 * @template TKey of array-key
 * @template T
 *
 * @implements TypeGenerator<array<TKey, T>>
 */
final class ArrayType implements TypeGenerator
{
    /**
     * @var list<TypeGenerator<TKey>>
     */
    private array $keys = [];

/**
     * @var list<TypeGenerator<T>>
     */
    private array $values = [];

/**
     * @param TypeGenerator<TKey> $key
     * @param TypeGenerator<T> $value
     */
    public function __construct(TypeGenerator $key, TypeGenerator $value)
    {
        $this->keys[] = $key;
        $this->values[] = $value;
    }

/**
     * @return array<TKey, T>
     */
    public function __invoke(): array
    {
        $keys = $values = [];
        $countKeys = count($this->keys);

for ($i = 0; count($keys) < $countKeys; ++$i) {
            $key = ($this->keys[$i])();

if (array_key_exists($key, $keys)) {
                --$i;

continue;
            }

$keys[$key] = $key;
        }

foreach ($this->values as $value) {
            $values[] = ($value)();
        }

return array_combine($keys, $values);
    }

/**
     * @template VKey of array-key
     * @template V
     *
     * @param TypeGenerator<VKey> $key
     * @param TypeGenerator<V> $value
     *
     * @return ArrayType<TKey|VKey, T|V>
     */
    public function add(TypeGenerator $key, TypeGenerator $value): ArrayType
    {
        // @TODO: See if we can fix this issue in PHPStan/PSalm.
        // There should not be @var annotation here.
        // An issue has been opened: https://github.com/vimeo/psalm/issues/8066
        /** @var ArrayType<TKey|VKey, T|V> $clone */
        $clone = clone $this;

/** @var list<TypeGenerator<TKey|VKey>> $keys */
        $keys = array_merge($this->keys, [$key]);
        $clone->keys = $keys;

/** @var list<TypeGenerator<T|V>> $values */
        $values = array_merge($this->values, [$value]);
        $clone->values = $values;

return $clone;
    }
}

$sub1 = (new ArrayType(new StringType(), new NullType()))();
/** @psalm-trace $sub1 */

$sub2 = (new ArrayType(new IntType(), new NullType()))();
/** @psalm-trace $sub2 */

$sub3 = ((new ArrayType(new StringType(), new StringType()))->add(new IntType(), new IntType()))();
/** @psalm-trace $sub3 */

Snippet created on June 10 2022 at 12:24 UTC