Use case

I often try to use flutter create to spin up a quick example. The number of times I use - instead of _ is astounding, and the error text doesn't make it especially clear that this is why my package name is invalid ("my-flutter-exampe" is not a valid Dart package name.).

Proposal

It would be super helpful if the error message called this out, as I imagine 1) a lot of people make this mistake and 2) it's not immediately obvious to them that the - vs _ distinction is the cause of the problem. The tool could also suggest a valid package name if swapping the separator character with _ would yield a valid package name.