UnusedFunctionCall false positive on mail standard extension

[smaddock]

When calling mail as documented in the PHP manual, Psalm throws an UnusedFunctionCall because the boolean return value is not captured and utilized.

https://psalm.dev/r/79996b7e5c

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/79996b7e5c

<?php

mail('a@b.c', 'subject line', 'message');

Psalm output (using commit 08afc45):

ERROR: UnusedFunctionCall - 3:1 - The call to mail is not used

[jack-worman]

How do you know if the function worked if you don't check?

if (!mail('a@b.c', 'subject line', 'message')) {
    throw new \Exception('mail() failed.');
}

But anyways, you can fix this problem by submitting a PR which adds mail to the impure function list in dictionaries/ImpureFunctionsList.php.

[smaddock]

Not saying one shouldn't check for it, only that the way it is documented in the PHP manual examples don't check for it, so it shouldn't return an UnusedFunctionCall. PR submitted.