[rust] Turn a `Result<T,T>` into a `T`.

resolve_result.rs

pub trait Resolve<T> {
  fn resolve(self) -> T;
}

impl <T> Into<T> for Result<T,T> {
  fn resolve(self) -> T {
    match self {
      Ok(value) => value,
      Err(err) => err,
    }
  }
}

fn main() {
  let result: Result<bool, String> = Ok(true);
  // let result: Result<bool, String> = Err("hello world".into());
  let code = {
    result
      .map(|b| if b { 1 } else { 0 })
      .map_err(|s| if s.len() == 0 { 2 } else { 3 })
      // : Result<i32, i32>
      .resolve()
  };
  // : i32
  println!("code: {}", code);
}