Static check enum as type annotation

```rust
enum Color {
    Red = "#FF0000",
    Green = "#00FF00",
    Blue = "#0000FF",
}

fn get_color(color: Color) -> str {
    match color {
        Color::Red => "red",
        Color::Green => "green",
        Color::Blue => "blue",
    }
}

get_color(Color::Red); // red

enum AnotherEnum {}

get_color(AnotherEnum); // Error: AnotherEnum is not a Color
```