Unresolved import and unstable library feature errors on Rust 1.68.2

[vincent-herlemont]

I am using stable version Rust 1.68.2 and the thiserror crate, but I am encountering errors related to an unresolved import and the use of an unstable library feature.

I try to activate Backtrace like described in the documentation: latest/thiserror/.

A From impl is generated for each variant containing a #[from] attribute.

Note that the variant must not contain any other fields beyond the source error and possibly a backtrace. > A backtrace is captured from within the From impl if there is a field for it.

#[derive(Error, Debug)]
pub enum MyError {
   Io {
       #[from]
        source: io::Error,
        backtrace: Backtrace,
    },
}

Here's the code I am using with the thiserror crate:

use thiserror::Error;
use std::backtrace::Backtrace;

#[derive(Error, Debug)]
pub enum Error {
    Io {
        #[from]
        source: std::io::Error,
        backtrace: Backtrace,
    }
}

And my function:

pub fn open_file(path: &Path) -> Result<File> {
    let file = File::open(path)?;
    Ok(file)
}

And my test:

let file = struct_db::open_file("my_path").unwrap();

Output logs:

error[E0432]: unresolved import `thiserror`
 --> src/error.rs:4:10
  |
4 | #[derive(Error, Debug)]
  |          ^^^^^ no `ThiserrorProvide` in `__private`
  |
  = note: this error originates in the derive macro `Error` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0658]: use of unstable library feature 'error_generic_member_access'
 --> src/error.rs:4:10
  |
4 | #[derive(Error, Debug)]
  |          ^^^^^
  |
  = note: see issue #99301 <https://github.com/rust-lang/rust/issues/99301> for more information
  = note: this error originates in the derive macro `Error` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: `error::Error` doesn't implement `std::fmt::Display`
  --> src/error.rs:5:10
   |
5  | pub enum Error {
   |          ^^^^^ `error::Error` cannot be formatted with the default formatter
   |
   = help: the trait `std::fmt::Display` is not implemented for `error::Error`
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
note: required by a bound in `std::error::Error`
  --> /home/user/.rustup/toolchains/1.68.2-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/error.rs:31:26
   |
31 | pub trait Error: Debug + Display {
   |                          ^^^^^^^ required by this bound in `Error`

Any suggestions on how to resolve this issue would be greatly appreciated.

---

Related topics that I read to try to resolve this issue:

• Replace failure crate with thiserror hyperledger/aries-vcx#684
• derive(Error) with Backtrace causes errors on beta #204

[dtolnay]

This is a duplicate of #204.

[dzmitry-lahoda]

Currenly anyhow uses some rust nightly features https://github.com/dtolnay/anyhow/blob/master/build.rs if I am not wrong.

So would be PR thiserror accepted to have similar solution to enable errors in core in rust?