Demo for structopt possible_values issue

README.md

Add the following files in a new folder (with paths as per filenames), and comment/uncomment the structopt dependencies to demo it. This is derived from code at https://github.com/Michael-F-Bryan/mdbook-linkcheck

Cargo.toml

[package]
name = "structopt-bug"
version = "0.1.0"
authors = ["Tom Parker-Shemilt <palfrey@tevp.net>"]
edition = "2018"

[dependencies]
# This works
# structopt = "=0.3.7"
# This doesn't work
structopt = "=0.3.8"

# Fix for https://github.com/TeXitoi/structopt/pull/353
syn = { version = "1", default-features = false, features = ["derive", "parsing", "proc-macro", "clone-impls"] }

src\bin\main.rs

use structopt::StructOpt;

#[derive(Debug, StructOpt, Clone)]
struct Args {
    #[structopt(
        short = "c",
        long = "colour",
        help = "Output colouring",
        default_value = "auto",
        possible_values = &["always", "auto", "never"]
    )]
    colour: String,
}

fn main() {
   let _ = Args::from_args();
}