Binding scalars to generics

[MidnightDesign]

It would be great if generics supported binding scalars. Here's a use case:

/**
 * @template K of array-key
 * @param array<K, int> $in
 * @return array<K, string>
 */
function stringValues(array $in): array {
    return array_map(fn (int $int): string => (string) $int, $in);
}

Currently, this gives me a

PHPDoc tag @template K for function stringValues() with bound type (int|string) is not supported.

See https://phpstan.org/r/f80b7892-415f-4c38-a63b-37b885d1b6ae

I have read somewhere that this is being considered, but I couldn't find an issue for it and I wanted to provide a use case.

[ondrejmirtes]

I'm kind of undecided if the K in case of a literal value like 1 should be resolved to int or 1. Currently (if you don't use the bound) 1 is resolved to int. So for example passing 1 as T and returning array<T> leads to array<int>.

[MidnightDesign]

In TypeScript, literals in code are generalized: const num = 1; // type 'number'.
But literals in types are not: type oneOrTwo = 1 | 2; const num = 1 as oneOrTwo; // type '1 | 2'.

Since we're dealing with types here, I'd say they should not be generalized.

Don't know if this helps though. Or if that's even what you meant.

[simPod]

psalm has support for it. Would be nice if both tools interpreted this in the same way.

[ondrejmirtes]

Implemented: phpstan/phpstan-src@ac7b49e

[github-actions]

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