class_alias breaks if class exists

[muglug]

Bug report

Question	Answer
Box version	3.8
PHP version	7.3.5
MacOs
Github Repo	- https://github.com/vimeo/psalm

PHP Scoper slightly breaks this polyfill for JsonException.

It gets a class_alias appended (as expected), but that class_alias causes a warning when running on PHP 7.3 as PHP 7.3 includes the class.

\class_alias('_HumbugBoxc9de1eddd699\\JsonException', 'JsonException', \false);

I'm currently fixing it in Psalm's build with this hideous patch that wraps a class_exists check around the class_alias:

if (!\class_exists(\JsonException::class, false)) {
    \class_alias('_HumbugBox9de1eddd699\\JsonException', 'JsonException', \false);
}

[theofidry]

Hm I see, do you think all those class aliases should be wrapped in a class_exists() statement like you did?

[muglug]

Yeah, I think so