"Use of undefined constant STDIN - assumed 'STDIN'"

[francoism90]

Symfony version(s) affected: symfony/console v5.1.0

Description
I'm keep getting his error on Laravel, I don't know if this should be reported to them or if this is a Symfony issue?

How to reproduce
Update to latest deps.

Possible Solution
I don't think the constant exists when using it as a dep, shouldn't it be checked if it is?

Additional context
Converting the constant works fine, but I don't think this is the solution:

public function __construct(OutputInterface $output, $input = 'STDIN')
    {
        $this->output = $output;
        $this->input = $input;
    }

[xabbuh]

I think #37130 should fix this.

[francoism90]

@fabpot Thanks for the fix. :)