Psalm doesn't recognize that an array key can be an int

[kamil-tekiela]

PHP maintains numeric strings as integers whenever used as an array key. It's a little quirk of PHP. Psalm however, doesn't recognize the fact that a value which is initially string can be int|string when used as an array key.

This example is showing how to do it properly with a string cast:
https://psalm.dev/r/5edbef1817
Psalm says that the cast is redundant but it's not. Without it, PHP would throw an error!
https://3v4l.org/WirJP

Psalm should treat all array keys as int|string unless the array is a list.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/5edbef1817

<?php
declare(strict_types=1);

/** @var string[] $strings */
$strings = (function():array{
    return ['1'];
})();
$arr = [];
foreach ($strings as $string) {
    $arr[$string] = 42;
}

foreach ($arr as $key => $value) {
    echo htmlentities((string) $key);
}

Psalm output (using commit f73fe36):

ERROR: RedundantCastGivenDocblockType - 14:23 - Redundant cast to string given docblock-provided type

INFO: UnusedForeachValue - 13:26 - $value is never referenced or the value is not used

[dragosprotung]

I had the same issue just now. Here is another code snippet that reproduces the issue:
https://psalm.dev/r/4517dabd6d

<?php declare(strict_types = 1);

class test {
	public string $prop = '1';
}
$test = new test();

$array = [$test->prop => 'value'];

foreach ($array as $k => $_) {
	echo (string) $k; // even if the key was a string, but it represented an int, PHP will convert it to int
}

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/4517dabd6d

<?php declare(strict_types = 1);

class test {
	public string $prop = '1';
}
$test = new test();

$array = [$test->prop => 'value'];

foreach ($array as $k => $_) {
	echo (string) $k; // even if the key was a string, but it represented an int, PHP will convert it to int
}

Psalm output (using commit f73fe36):

ERROR: RedundantCast - 11:7 - Redundant cast to string

[kkmuffme]

Basic unit test cases:
https://psalm.dev/r/db8d70db4e

Funny enough for array shapes it already works correctly as the example shows
=> only for fallback_params it has the same issue.

Duplicate of #8680

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/db8d70db4e

<?php

$x = ['15' => 'a', 17 => 'b'];
abc($x);
def($x);
ghi($x);

/**
 * @param array<numeric-string, string> $arg
 * @return void
 */
function abc($arg) {
    foreach ($arg as $k => $v) {
     	/** @psalm-trace $k */; // should be int|numeric-string since float numeric strings stay strings, e.g. '1.2' 
    }
}

/**
 * @param array<15|'17', string> $arg
 * @return void
 */
function def($arg) {
    foreach ($arg as $k => $v) {
     	/** @psalm-trace $k */;   
    }
}

/**
 * @param array{15: string, '17': string} $arg
 * @return void
 */
function ghi($arg) {
    foreach ($arg as $k => $v) {
     	/** @psalm-trace $k */;   
    }
}

Psalm output (using commit 0e43c44):

ERROR: InvalidArgument - 4:5 - Argument 1 of abc expects array<numeric-string, string>, but array{15: 'a', 17: 'b'} provided

ERROR: InvalidArgument - 5:5 - Argument 1 of def expects array<'17'|15, string>, but array{15: 'a', 17: 'b'} provided

INFO: Trace - 14:29 - $k: numeric-string

INFO: Trace - 24:29 - $k: '17'|15

INFO: Trace - 34:29 - $k: 15|17