clippy3 solution

solutions/22_clippy/clippy3.rs

@@ -1 +1,31 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+use std::mem;
+
+#[rustfmt::skip]
+#[allow(unused_variables, unused_assignments)]
+fn main() {
+    let my_option: Option<()> = None;
+    // `unwrap` of an `Option` after checking if it is `None` will panic.
+    // Use `if-let` instead.
+    if let Some(value) = my_option {
+        println!("{value:?}");
+    }
+
+    // A comma was missing.
+    let my_arr = &[
+        -1, -2, -3,
+        -4, -5, -6,
+    ];
+    println!("My array! Here it is: {:?}", my_arr);
+
+    let mut my_empty_vec = vec![1, 2, 3, 4, 5];
+    // `resize` mutates a vector instead of returning a new one.
+    // `resize(0, …)` clears a vector, so it is better to use `clear`.
+    my_empty_vec.clear();
+    println!("This Vec is empty, see? {my_empty_vec:?}");
+
+    let mut value_a = 45;
+    let mut value_b = 66;
+    // Use `mem::swap` to correctly swap two values.
+    mem::swap(&mut value_a, &mut value_b);
+    println!("value a: {}; value b: {}", value_a, value_b);
+}