feat: Rewrite try_from_into

[ikar49]

English is not my native language, so I may have made some mistakes in the text. I would be grateful if someone could check it out.

closes #392

[AbdouSeck]

Hi @ikar49,

This looks really good. Thank you for the great work. I have one suggestion here. The hint provided in the info.toml for the from_str exercise tells people to do an almost copy-paste operation from the try_from_into exercise to answer the question. However, that will not be the case once this pull request gets merged.
Can you please edit the hint for from_str to say something else? You can say something like:

The implementation of FromStr should return an Ok with a Person object, or an Err with a string if the string is not valid.

Please feel free to reach out if you have any questions.

Thank you so much!

Abdou

[AbdouSeck]

Hi @ikar49,

Sorry, I completely overlooked something:

I realized the Color is defined with u8 as inner types while the implementations are asking for i16. While this may not be a problem by itself, if someone directly converts an i16 to a u8, there may be some wrapping issues. For instance, the following will compile, but is not really what you would want:

fn main() {
    let v = 1000;
    println!("{}", v as u8);
}

Evidently, this can be resolved by adding unit tests that makes sure that if a value greater than 255 is provided, then an error is returned.

Please let me know if you have a question about this.

Thank you,

Abdou

[ikar49]

Hello @AbdouSeck.

Are you suggesting replacing i16 with isize, if I understand correctly?

[AbdouSeck]

@ikar49,

Not really. I think it would be fine to just add a test cases to handle when values above 255 are passed. I am thinking of the following tests:

#[test]
fn test_out_of_range_slice() {
    let v = vec![10000, 1000, 1000];
    let c = Color::try_from(&v[..]);
    assert!(c.iserr());
}

and

#[test]
fn test_out_of_range_array() {
    let v = [10000, 1000, 1000];
    let c = Color::try_from(v);
    assert!(c.iserr());
}

and also

#[test]
fn test_out_of_range_tuple() {
    let v = (10000, 1000, 1000);
    let c = Color::try_from(v);
    assert!(c.iserr());
}

These will make sure that the implementations remember to return an error if the values provided are greater than 255.

Please let me know if you have any questions.

Thank you,

Abdou

[ikar49]

@AbdouSeck,

I fixed it. What you think about it?

[AbdouSeck]

Hi @ikar49, I think this should take care of all types of out-of-range issues. Thank you so much!

[shadows-withal]

Thank you so much!

[ekaats]

I've just been going through the rustlings exercises and found this one a little confusing. I could not get the type Error = Box<dyn error::Error>; working. After changing this back to type Error = String; and just returning an Err("Something went wrong")-esque error I was able to finish the exercise without issue. Maybe make a separate exercise for that error?