Flag misinterpreted as option when using macros on Rust 1.47.0 #439

use structopt::StructOpt;

macro_rules! command {
    (
        $(#[derive($($t:tt),+)])?
        #[structopt(
            name = $name:literal,
            about = $about:literal,
            $( $var:ident = $val:expr, )*
        )]
        struct $command:ident {
            $(
                $(#[$m:meta])*
                $field:ident: $type:ty,
            )*
        }
    ) => (
        $(#[derive($($t),+)])?
        #[structopt(
            name = $name,
            about = $about,
            $( $var = $val, )*
        )]
        struct $command {
            $(
                $(#[$m])*
                $field: $type,
            )*
        }
    );
}

command!{
    #[derive(Debug, StructOpt)]
    #[structopt(
        name = "opts", 
        about = "Opts",
    )]
    struct Opts {
        #[structopt(long = "x", help = "xxx")]
        x: bool,
    }
}

fn main() {
    println!("{:?}", Opts::from_args());
}