Object like array with required key not always considered non-empty

[AndrolGenhald]

https://psalm.dev/r/23869e7fec

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/23869e7fec

<?php

/**
 * @psalm-suppress UnusedParam
 * @param non-empty-array<string, string> $arg
 */
function test(array $arg): void {}

/** @var array{a?: string, b: string} */
$a = ['b' => 'b'];
test($a); // 'b' is required, $a should be non-empty-array

/** @var array{a: string, b?: string} */
$b = ['a' => 'a'];
test($b); // works

Psalm output (using commit 42d3bce):

ERROR: ArgumentTypeCoercion - 11:6 - Argument 1 of test expects non-empty-array<string, string>, parent type array{a?: string, b: string} provided