Is [ 0 => 0, 1 => 1 ] a valid list ?

[someniatko]

https://psalm.dev/r/73fe3f58d1

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/73fe3f58d1

<?php

/** @param list $list */
function takesList(array $list): void {}

takesList([ 0 => 0, 1 => 1 ]);

Psalm output (using commit 7fc4a85):

INFO: UnusedParam - 4:26 - Param $list is never referenced in this method

ERROR: InvalidArgument - 6:11 - Argument 1 of takesList expects list<mixed>, array{0: int(0), 1: int(1)} provided

[muglug]

Nah, leave out the keys and this passes – I don't consider this a bug

[someniatko]

@muglug Well, yeah, it is obvious that it would pass if you leave out the keys. You have unit tests for this after all. I did not mention this is a bug report, by the way. This issue is more like of question type - I've just asked whether [ 0 => 0, 1 => 1 ] is a valid list in the Psalm type system, or not. If it is not, it would be very nice to know the reason why - maybe it's documented somewhere.

A possible outcome is that it is actually a list as defined by the docs (and common sense, imo), but Psalm doesn't infer that because it's technically hard to implement. In such case i would suggest "bug" badge to stay, and a "wontfix" badge to be added.

Another outcome is that [ 0 => 0, 1 => 1 ] is not a list. Then i suggest it's a documentation issue because, at least I failed to find anything proving it's not.

[someniatko]

BTW, the reason I have asked this issue-question is because earlier I was explaining here doctrine/collections#242 (comment) the concept of list (vs array) to a, presumably, Doctrine contributor. However, now I feel myself a bit guilty because probably my explanation is wrong.