Get class from constant

I have a function with a parameter that is fed a constant.
The constant can come from several classes, see example:

function myFunction($const): string {
    // do some stuff
    // use the classname do some other stuff
    // do some more stuff

    return $output;
}

echo myFunction(SomeClass::A_CONSTANT);
echo myFunction(OtherClass::ALSO_A_CONSTANT);

To make things more difficult, the constants I’m getting come from aliased classes, in the class file outside the class you have something like this:

class_alias(RealClass::class, 'SomeClass');

Is there a way to get the classname from the constant?
So from the example above I would get RealClass when I use the constant SomeClass::A_CONSTANT.
I can work around the alias, getting SomeClass when I use SomeClass::A_CONSTANT is just fine.

I’ve tried get_defined_constants(), get_class(), get_parent_class() & get_called_class(), but those just get the result or result in errors due to not being in scope or the variable being a string instead of an object.