19:48 $ cat src/main.rs 
use scale::{
    Decode,
    Encode,
};
pub type GroupId = u32;

#[derive(Debug, Clone, PartialEq,Encode, Decode, Default)]
pub enum PostVisibility {
    #[default]
    Public,
    Supporter,   
    Group(GroupId), 

#[derive(Encode, Decode)]
pub enum Foo {
    Bar,
}

fn main() {
    println!("Hello, world!");
}

   Checking my_project v0.1.0 (/Users/thientd/github/my_project)
error: casting `usize` to `u8` may truncate the value
  --> src/main.rs:12:5
   |
12 |     Group(GroupId), // Visible to a specific group
   |     ^^^^^
   |
   = help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#cast_possible_truncation
   = note: requested on the command line with `-D clippy::cast-possible-truncation`
help: ... or use `try_from` and handle the error accordingly
   |
12 |     Group::try_from(Encode)(GroupId), // Visible to a specific group
   |          ++++++++++++++++++