I’m trying to parse some user input, the input is stored in a struct where there are a lot of options/results (to deal with the data being uninitialized before the user enters it) and when the user submits it it needs to go into a struct where all the values are known.

I’d like to be able to a vector with any errors so I can give feedback to the user on all the errors with the input (not just the first). However, I can’t find a good way to do that.

struct Test {
    x: i32,
    y: String,
}

#[derive(Debug)]
enum Errors {
    OneIsNone,
    TwoIsNone,
}

The my current approach is:

fn main() -> Result<Test, Vec<Errors>> {
    let option1 = Some(5);
    let option2 = None;

    let mut errors = Vec::new();

    let x: i32;
    match option1 {
        Some(value) => x = value,
        None => errors.push(Errors::OneIsNone),
    };

    let y: String;
    match option2 {
        Some(value) => y = value,
        None => errors.push(Errors::TwoIsNone),
    }

    if errors.len() != 0 {
        return Err(errors)
    }

    Ok(
        Test {
            x,
            y
        }
    )
}

Which doesn’t work because the compiler can’t tell that x and y must be initialised if the code reaches the Ok block.

In this case I could just unwrap match the two results but that approach will become hideously clunky for structs with a large number of fields.

Basically I want a way to take in a large number of results and parse them into a struct if they all give Ok() or return a vector containing all the errors otherwise i.e. how to I implement unwrap_or_errors in

fn main() -> Result<Test, Vec<Errors>> {
    let option1 = Some(5);
    let option2 = None;

    let mut errors = Vec::new();
    

    let x = match option1 {
        Some(val) => Ok(val),
        None => Err(Errors::OneIsNone),
    };

    let y =  match option2 {
        Some(val) => Ok(val),
        None => Err(Errors::TwoIsNone),
    };

    
    if errors.len() != 0 {
        return Err(errors)
    }

    Test::unwrap_or_errors(x, y)?
}