Negation type

[mathroc]

🚀 Describe the Feature

It can be useful sometimes to indicate that an argument or return value should not be of a certain type (another way of narrowing the accepted input type or declared return type)

✅ Use Case / Example

<?php declare(strict_types=1);

/**
 * @template I of scalar
 * @template C of I&(literal-string|literal-int|false|true|null)
 * @param I $input
 * @param C&literal $canary
 * @return ($input is $canary ? null : I&!C)
 */
function canaryValueToNull(mixed $input, mixed $canary): mixed
{
    return $input === $canary ? null : $input;
}

function g(int|false $input): ?int
{
    // should be OK
    return canaryValueToNull($input, false);
}

/** @return non-empty-string */
function h(string $input): ?string
{
    // should be OK
    return canaryValueToNull($input, '');
}

function i(int|bool $input, float $f): ?int
{
    // should not be OK (return value is int|true|null)
    return canaryValueToNull($input, false);
}

function j(int|false $input): int
{
    // should not be OK (return value is int|null)
    return canaryValueToNull($input, false);
}

💡 Proposed Solution

No response

📌 Priority

Nice to have

📝 Additional Context

No response