error: flatten is only allowed on fields
  --> $DIR/struct_flatten.rs:12:24
   |
12 | #[clap(name = "basic", flatten)]
   |                        ^^^^^^^

error[E0277]: the trait bound `Opt: std::convert::From<clap::parse::matches::arg_matches::ArgMatches>` is not satisfied
  --> $DIR/struct_flatten.rs:11:10
   |
11 | #[derive(Clap, Debug)]
   |          ^^^^ the trait `std::convert::From<clap::parse::matches::arg_matches::ArgMatches>` is not implemented for `Opt`