copper aspen
The problem in that function is that s.parse() returns a Result, and that Result is immediately .unwrap(). When you unwrap a Result (or similar, like Option), you get the Ok() value if that's what the Result is. But if Result is Err, then unwrap() will throw a panic.
(https://doc.rust-lang.org/std/result/enum.Result.html#method.unwrap)
The exercise wants you to change this line such that if .parse() fails, that you return an error instead of panicing.
Hopefully that offers some help? Is there something specific you're unsure how to do, or something that doesn't make sense?
austere kettle
The error that the function wants to return is this enum here:
enum ParsePosNonzeroError {
Creation(CreationError),
ParseInt(ParseIntError),
}
So the variants indicate that it can be constructed from a value of type CreationError or ParseIntError
The already existing function here is able to convert from a CreationError to a ParsePosNonzeroError
fn from_creation(err: CreationError) -> ParsePosNonzeroError {
ParsePosNonzeroError::Creation(err)
}
And it's asking you to write a similar function from_parseint which takes a ParseIntError and converts it to a ParsePosNonzeroError - that's the first part
Then notice that in the parse_pos_nonzero function, there is already this pattern for "do something which returns a Result, and apply a function to change the error type"
PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation)
You'll want to do something similar here to change the error type of the Result from parse using ParsePosNonzeroError::from_parseint
It will be useful to take a look at this page too for an idiomatic approach: https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator