Following code works, the cause is enum Color that is declared in fn main

enum Color {
  red green blue
}

fn main() {
  mut color := Color.red
  // V knows that `color` is a `Color`. No need to use `color = Color.green` here.
  color = .green
  println(color) // "1"  TODO: print "green"? 
}

@vuhg so it is bad error message. I do not know why it is not working...

@medvednikov The above screened behavior seems a bit odd. It's not documented that enums have to be declared outside of functions. I tried some other stuff and declared some enums within a bunch of functions (this time not within main) and get a similar error. Although I did this (declaring them 'standalone') naturally and never thought about this, they are just some kinds of variables aren't they? So one should be able to do the above declaration style. That would limit their scope too - besides pub enum declaration.

I personally think it's a documentation issue to clarify the use of them.