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#![deny(
missing_copy_implementations,
missing_debug_implementations,
missing_docs,
trivial_casts,
trivial_numeric_casts,
unsafe_code,
unstable_features,
unused_import_braces,
unused_qualifications
)]
use std::fmt;
pub type Result<T> = std::result::Result<T, NotFourError>;
#[derive(Debug, Clone, Copy)]
pub enum NotFourError {
Close,
NotClose,
}
impl std::fmt::Display for NotFourError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
NotFourError::Close => write!(f, "it's pretty close to four"),
NotFourError::NotClose => write!(f, "it's definitely not four"),
}
}
}
impl std::error::Error for NotFourError {}
pub fn do_work(input: usize) -> Result<&'static str> {
match input {
n if n == four() => Ok("it's four"),
3..=5 => Err(NotFourError::Close),
_ => Err(NotFourError::NotClose),
}
}
fn four() -> usize {
2 + 2
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn it_works_private() {
assert_eq!(four(), 4);
}
}