fix various clippy lints from 1.57

aoc2020/src/day20.rs

@@ -59,7 +59,7 @@ enum Rotation {
 ///
 /// Note: we don't need a horizontal and a vertical flip, these result in the same output as a 180
 /// degree rotation when combined, so only one is necessary
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Default, Clone, Copy)]
 struct Transform {
     flip: bool,
     rotation: Option<Rotation>,
@@ -121,15 +121,6 @@ impl Transform {
     }
 }
 
-impl Default for Transform {
-    fn default() -> Self {
-        Self {
-            flip: false,
-            rotation: None,
-        }
-    }
-}
-
 #[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
 enum Position {
     Down,

aoc2020/src/day24.rs

@@ -133,7 +133,7 @@ fn part2(input: &str) -> Result<usize> {
 /// These use the axial coordinates described here:
 ///
 /// https://www.redblobgames.com/grids/hexagons/#coordinates-axial
-#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
+#[derive(Debug, Default, Clone, Copy, Hash, PartialEq, Eq)]
 struct HexCoordinates {
     q: i64,
     r: i64,
@@ -188,12 +188,6 @@ impl HexCoordinates {
     }
 }
 
-impl Default for HexCoordinates {
-    fn default() -> Self {
-        Self { q: 0, r: 0 }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;