Structopt: from_str parser for an Option field

Created on 8 Mar 2019 · 5Comments · Source: TeXitoi/structopt

Using a from_str parser for an Option field results in the following:

use structopt::StructOpt;

#[derive(Debug)]
struct A {}

impl From<&str> for A {
    fn from(a: &str) -> A {
        // ...
        A {}
    }
}

#[derive(Debug, StructOpt)]
struct Opt {
    #[structopt(parse(from_str))]
    a: Option<A>,
}

error[E0277]: the trait bound `A: std::convert::From<&&str>` is not satisfied
  --> src/lib.rs:13:17
   |
13 | #[derive(Debug, StructOpt)]
   |                 ^^^^^^^^^ the trait `std::convert::From<&&str>` is not implemented for `A`
   |
   = help: the following implementations were found:
             <A as std::convert::From<&str>>
   = note: required by `std::convert::From::from`



md5-440378ef64ed62d6c91840a8d42e5bfb



rust 1.33 
structopt 0.2.14

bug

Source