Fix warnings

solutions/13_error_handling/errors2.rs

@@ -16,6 +16,7 @@
 
 use std::num::ParseIntError;
 
+#[allow(unused_variables)]
 fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
     let processing_fee = 1;
     let cost_per_item = 5;

solutions/13_error_handling/errors4.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::comparison_chain)]
+
 #[derive(PartialEq, Debug)]
 enum CreationError {
     Negative,

solutions/13_error_handling/errors6.rs

@@ -36,7 +36,7 @@ impl PositiveNonzeroInteger {
     fn new(value: i64) -> Result<Self, CreationError> {
         match value {
             x if x < 0 => Err(CreationError::Negative),
-            x if x == 0 => Err(CreationError::Zero),
+            0 => Err(CreationError::Zero),
             x => Ok(Self(x as u64)),
         }
     }
@@ -57,7 +57,6 @@ fn main() {
 #[cfg(test)]
 mod test {
     use super::*;
-    use std::num::IntErrorKind;
 
     #[test]
     fn test_parse_error() {