How do I make this work as expected?

[loevgaard]

https://psalm.dev/r/a2c22ba1dd

I would like TCallback to either be an int or float. If I use the numeric type it can also be numeric-string which is not intended.

Can I make this work somehow?

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/a2c22ba1dd

<?php

/**
 * @template TCallback of int|float
 *
 * @param callable():TCallback $callback
 *
 * @return TCallback
 */
function sum(callable $callback, array $items): int|float
{
    return array_sum(array_map($callback, $items));
}

Psalm output (using commit 79ab7e2):

ERROR: InvalidReturnStatement - 12:12 - The inferred type 'float' does not match the declared return type 'TCallback:fn-sum as float|int' for sum

ERROR: InvalidReturnType - 8:12 - The declared return type 'TCallback:fn-sum as float|int' for sum is incorrect, got 'float'

[M393]

You need to cast the return value of array_sum to TCallback and callable need one parameter of mixed type.
https://psalm.dev/r/fed7db1b92

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/fed7db1b92

<?php

/**
 * @param callable(mixed):T $callback
 * @return T
 * @template T of int|float
 */
function sum(callable $callback, array $items): int|float
{
    /** @var T $result */
    $result = array_sum(array_map($callback, $items));
    return $result;
}

$_sum_i = sum(static fn (int $i): int => $i, [1, 2, 3]);
$_sum_f = sum(static fn (float $i): float => $i, [1, 2, 3]);
/** @psalm-trace $_sum_f $_sum_i */

Psalm output (using commit 79ab7e2):

INFO: Trace - 17:36 - $_sum_f: float

INFO: Trace - 17:36 - $_sum_i: int

[loevgaard]

Cool, thanks! Is this expected? I would expect that if a type is either int or string and array_sum returns either int or string then Psalm would put 2 and 2 together