`array_intersect_key` results in array<array-key, mixed> vs array<string, mixed>

[bkdotcom]

https://psalm.dev/r/16ba5c2e38

/**
 * @return array<string, mixed>
 */
function foo(array $values) {
    $default = array(
        'foo' => 'foo',
        'bar' => 'bar',
    );
    $return = \array_merge($default, $values);
    return \array_intersect_key($return, $default); // we know that keys are limited to 'foo'|'bar', 
                                                    // yet psalm infers array<array-key, mixed>
}

INFO: MixedReturnTypeCoercion - 4:12 - The declared return type 'array<string, mixed>' for foo is more specific than the inferred return type 'array<array-key, 'bar'|'foo'|mixed>'

It knows the values are 'bar'|'foo'|mixed, but doesn't know the keys are 'foo'|'bar'?

which leads to .. ERROR: MixedArgumentTypeCoercion when passing the results to another method

do I need to add some annotation?

[psalm-github-bot[bot]]

I found these snippets:

https://psalm.dev/r/16ba5c2e38

<?php

/**
 * @return array<string, mixed>
 */
function foo(array $values) {
    $default = array(
        'foo' => 'foo',
        'bar' => 'bar',
    );
    $return = \array_merge($default, $values);
    return \array_intersect_key($return, $default);
}

Psalm output (using commit 4b2c698):

INFO: MixedReturnTypeCoercion - 12:12 - The type 'array<array-key, 'bar'|'foo'|mixed>' is more general than the declared return type 'array<string, mixed>' for foo

INFO: MixedReturnTypeCoercion - 4:12 - The declared return type 'array<string, mixed>' for foo is more specific than the inferred return type 'array<array-key, 'bar'|'foo'|mixed>'

[weirdan]

This would require a specific return type provider. Currently we only have a generic stub for array_intersect_key(): https://github.com/vimeo/psalm/blob/62b525993d6091c8c2b95bfdc0b70a4e077e6f1e/stubs/CoreGenericFunctions.phpstub#L30-L42