Compile error when using edn-rs as dependency

[divs1210]

Hi!

I'm new to rust, so please bear with me if I'm being stupid.

I get the following error when trying to use this crate:

Compiling edn-rs v0.16.12
error[E0277]: the trait bound `std::string::String: std::convert::From<char>` is not satisfied
   --> /Users/divyansh/.cargo/registry/src/github.com-1ecc6299db9ec823/edn-rs-0.16.12/src/deserialize/parse.rs:119:22
    |
119 |     let mut symbol = String::from(a);
    |                      ^^^^^^^^^^^^ the trait `std::convert::From<char>` is not implemented for `std::string::String`
    |
    = help: the following implementations were found:
              <std::string::String as std::convert::From<&std::string::String>>
              <std::string::String as std::convert::From<&str>>
              <std::string::String as std::convert::From<std::borrow::Cow<'a, str>>>
              <std::string::String as std::convert::From<std::boxed::Box<str>>>
    = note: required by `std::convert::From::from`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
error: could not compile `edn-rs`.

To learn more, run the command again with --verbose.

This is my code for reference:

use edn_rs::{Edn};
use std::str::FromStr;

fn main() {
    let edn: Edn = Edn::from_str("[1 2]");

    println!("{:?}", edn);
}

What am I doing wrong?

[naomijub]

What is a? I should be a &str, so anything formatted like "this is a &str".

For the rust snipped you posted the problem is that Edn::from_str returns a type Result<Edn, EdnError>, so there are two possibilities for this:

use edn_rs::Edn;
use std::str::FromStr;

fn main() {
    let edn: Result<Edn, edn_rs::EdnError> = Edn::from_str("[1 2]");

    println!("{:?}", edn);
}

or

use edn_rs::Edn;
use std::str::FromStr;

fn main() {
    let edn: Edn = Edn::from_str("[1 2]").unwrap();

    println!("{:?}", edn);
}

[naomijub]

Do you understand Result and Option types?

[divs1210]

I was following examples from the readme, and there is this code snippet:

let edn_str = "{:a \"2\" :b [true false] :c #{:A {:a :b} nil}}";
// std::str::FromStr
let edn: Edn = Edn::from_str(edn_str);

so I wasn't aware that Edn::from_str would return an Option.

Anyhow, adding .unwrap to my code doesn't seem to have any effect.

The String::from(a) code is not a part of my codebase, it seems to be a part of this crate which seems to be failing to build.

[divs1210]

Basically this is my main.rs:

use edn_rs::Edn;
use std::str::FromStr;

fn main() {
    let edn: Edn = Edn::from_str("[1 2]").unwrap();
    println!("{:?}", edn);
}

and this is my Cargo.toml:

[package]
name = "native"
version = "0.1.0"
edition = "2018"

[dependencies]
edn-rs = "0.16.11"

And this is the error I get:

$ cargo run
Compiling edn-rs v0.16.12
error[E0277]: the trait bound `std::string::String: std::convert::From<char>` is not satisfied
   --> /Users/divyansh/.cargo/registry/src/github.com-1ecc6299db9ec823/edn-rs-0.16.12/src/deserialize/parse.rs:119:22
    |
119 |     let mut symbol = String::from(a);
    |                      ^^^^^^^^^^^^ the trait `std::convert::From<char>` is not implemented for `std::string::String`
    |
    = help: the following implementations were found:
              <std::string::String as std::convert::From<&std::string::String>>
              <std::string::String as std::convert::From<&str>>
              <std::string::String as std::convert::From<std::borrow::Cow<'a, str>>>
              <std::string::String as std::convert::From<std::boxed::Box<str>>>
    = note: required by `std::convert::From::from`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
error: could not compile `edn-rs`.

To learn more, run the command again with --verbose.

[naomijub]

The same exact code for me returns Vector(Vector([UInt(1), UInt(2)])) .

This snippet:

use edn_rs::Edn;
use std::str::FromStr;

fn main() {
    let edn_str = "{:a \"2\" :b [true false] :c #{:A {:a :b} nil}}";
    let edn: Edn = Edn::from_str(edn_str).unwrap();
    println!("{:?}", edn);
}

returns Map(Map({":a": Str("2"), ":b": Vector(Vector([Bool(true), Bool(false)])), ":c": Set(Set({Map(Map({":a": Key(":b")})), Key(":A"), Nil}))}))

@otaviopace do you have ANY IDEA what may be happening to them?

@divs1210 Edn::from_str returns a Result<Edn, EdnError>, but the undated docs is on us, I will take a look at them next week. Rust analyzer can provide you with type hints. Also, the latest version is edn-rs = "0.16.12", that is something we need to update in the crates readme. And, the error you are getting is from the edn-rs crate src/deserialize/parse.rs:119:22, which doesnt fail locally 🤷🏽‍♀️

[naomijub]

@divs1210 What is your rustc version? I think the minimal required, as of now, is 1.46 or higher

[divs1210]

Thanks for your help!

I had two different versions of cargo installed via homebrew and rustup.

I uninstalled the homebrew version using $ brew uninstall rust, and updated the rustup version, and now it works fine!