Improve error message when trying to instantiate a script with _init(...)

[HolonProduction]

Fixes godotengine/godot-proposals#8488

[AThousandShips]

See also:

• Improve error message when a GDScript instance fails to be constructed #76632

[Mickeon]

Is it possible, and could it be nice to explicitly state how many parameters are required?

[HolonProduction]

Is possible. But doesn't help in the context of the proposal since no parameters can be passed. But yeah the error contains the expected amount of args so adding it to the message is possible.

Priority should however be to determine whether #76632 is the better solution or if they could coexist.

[AThousandShips]

I'd say that #76632 is more comprehensive as it also adds error information (ignore the accidental inclusion of unrelated code by the OP of that PR, hopefully that'll get fixer or a new branch made)

Having explicit information about this specific case might be good, but it could also be confusing when not creating an instance like this, as the same error is thrown then, having an error message with information is what matters here, having it say "too few arguments" would be enough on its own

The current issue is the complete lack of information about what went wrong

It also covers one case this does not

Also this solution prints this message when creating an instance with too few arguments yet not none, as it is called in other situations as well, not just resource initialization, so I think the other PR is better for this

[HolonProduction]

Adding the call error is definitely right. (I could probably include the changes into this PR to resolve the rebase mess up). I am just curious whether it is helpful in the context of godotengine/godot-proposals#8488. Or if we need to extend the error message to be helpful in that context. I'll have a look at the specific message.

[HolonProduction]

Closing in favor of #76632