rustlings/exercises/error_handling/errors5.rs

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// errors5.rs
// This program uses a completed version of the code from errors4.
// It won't compile right now! Why?
// Execute `rustlings hint errors5` for hints!
// I AM NOT DONE
use std::error;
use std::fmt;
use std::num::ParseIntError;
// TODO: update the return type of `main()` to make this compile.
fn main() -> Result<(), ParseIntError> {
let pretend_user_input = "42";
let x: i64 = pretend_user_input.parse()?;
println!("output={:?}", PositiveNonzeroInteger::new(x)?);
Ok(())
}
// Don't change anything below this line.
#[derive(PartialEq, Debug)]
struct PositiveNonzeroInteger(u64);
#[derive(PartialEq, Debug)]
enum CreationError {
Negative,
Zero,
}
impl PositiveNonzeroInteger {
fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
match value {
x if x < 0 => Err(CreationError::Negative),
x if x == 0 => Err(CreationError::Zero),
x => Ok(PositiveNonzeroInteger(x as u64))
}
}
}
// This is required so that `CreationError` can implement `error::Error`.
impl fmt::Display for CreationError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let description = match *self {
CreationError::Negative => "number is negative",
CreationError::Zero => "number is zero",
};
f.write_str(description)
}
}
impl error::Error for CreationError {}