Rust proper error handling (auto convert from one error type to another with question mark)

I want to learn how to properly deal with errors in Rust. I have read the book and this example; now I would like to know how I should deal with errors in this function:

fn get_synch_point(&self) -> Result {
    let url = self.root.join("/term/pv/synch"); // self.root is url::Url
    let url = match url {
        Ok(url) => url,
        // ** this err here is url::ParseError and can be converted to Error::Kind https://docs.rs/reqwest/0.8.3/src/reqwest/error.rs.html#54-57 **//
        Err(err) => {
            return Err(Error {
                kind: ::std::convert::From::from(err),
                url: url.ok(),
            })
        }
    };

    Ok(reqwest::get(url)?.json()?) //this return reqwest::Error or convert to pv::sych::MeasPeriods automaticly
}

This code is improper; it causes a compilation error:

error[E0451]: field kind of struct reqwest::Error is private
--> src/main.rs:34:42
|
34 | Err(err) => return Err(Error{kind: ::std::convert::From::from(err), url: url.ok()})
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ field kind is private

error[E0451]: field url of struct reqwest::Error is private
--> src/main.rs:34:81
|
34 | Err(err) => return Err(Error{kind: ::std::convert::From::from(err), url: url.ok()})
| ^^^^^^^^^^^^^ field url is private


What is a proper pattern to deal with that case? For me, reqwest::Error in this case is a good solution so I would like to avoid defining my own error type:

enum MyError {
    Request(reqwest::Error),
    Url(url::ParseError) // this already a part of request::Error::Kind!!!
}

Update 2020

The rust programming language is evolving quickly so a new answer can be added! I really liked custom_error but now I think thiserror will be my loved one!

use thiserror::Error;

#[derive(Error, Debug)]
pub enum DataStoreError {
#[error("data store disconnected")]
Disconnect(#[from] io::Error),
#[error("the data for key {0} is not available")]
Redaction(String),
#[error("invalid header (expected {expected:?}, found {found:?})")]
InvalidHeader {
expected: String,
found: String,
},
#[error("unknown data store error")]
Unknown,
}


This allow change io::Error to DataStoreError::Disconnect with question mark ?. Go here for details

useful links:

• great blog about using thiserror in combine with anyhow

Other interesting crates:

• anyhow - Flexible concrete Error type built on std::error::Error

• snafu - Situation Normal: All Fouled Up - SNAFU is a library to easily assign underlying errors into domain-specific errors while adding context. (similar to thiserror)

• custom_error - This crate contains a macro that should make it easier to define custom errors without having to write a lot of boilerplate code.

for panics:

• proc-macro-error - This crate aims to make error reporting in proc-macros simple and easy to use.

• human-panic - Panic messages for humans. Handles panics by calling std::panic::set_hook to make errors nice for humans.

Stack Overflow Q#48430836, score: 63