request for enhancement with variadics

[ghost]

could psalm infer a closure param type if the input to array_map was taken from a typed variadic ? (i.e. to upgrade the error message from "could not infer type")

<?php
function Foo(DateTime ...$dateTimes) : array {
  return array_map(function ($dateTime) : string {
    return (string) ($dateTime->format('c'));
  }, $dateTimes);
}

[muglug]

I won't do exactly what you asked, but I can have Psalm produce an error message similar to the one it produces here:

Argument 1 of datetimeArrayMapper expects callable(DateTime):mixed, callable(mixed):string provided

/**
 * @param callable(DateTime):mixed $c
 * @param DateTime[] $arr
 * @return mixed[]
 */
function datetimeArrayMapper(callable $c, array $arr) : array {
    $new_arr = [];
    foreach ($arr as $a) {
        $new_arr[] = $c($a);
    }
    return $new_arr;
}

function foo(DateTime ...$dateTimes) : array {
    return datetimeArrayMapper(
        function ($dateTime) : string {
            return "hello";
        },
        $dateTimes
    );
}

[muglug]

Actually that's not useful either.

[muglug]

Related to #204

[ghost]

I wasn't aware of the callable(T1):T2 syntax- was that part of your discarded resolution, or is it already in psalm?

[weirdan]

@WDD-Marv It's in dev-master only, there was no release since it was added AFAIK.

[muglug]

Yup, hopefully a release tonight with that feature.

The problem with adding an required param type of callable(Foo):mixed when array_map is passed Foo[] in its second arg is that Foo is a lower bound on the callable’s param type. You should be able to pass it callable(FooParent):mixed without issue, but adding that constraint I mentioned above breaks that.

[iluuu1994]

I would like this feature.

https://psalm.dev/r/7790a6ea53

$ints = [1, 2, 3, 4];
$ints2 = array_filter($ints, function ($int) {
  return $int->foo();
});

This example emits a few infos but no errors. Most modern languages allow emitting types in closures when it can be inferred (Swift, C#, Rust, etc.). I only really add them because it helps with static analysis and my IDE.

Psalm could still error when the type cannot be inferred of course.

[muglug]

Solved (in a slightly hacky fashion) using the scaffolding I added yesterday to fix #1600

This now typechecks (and Psalm finds bugs in the array_filter example)

https://psalm.dev/r/dc741dce60