$ cargo run
   Compiling patterns v0.1.0 (file:///projects/patterns)
warning: irrefutable if-let pattern
 --> src/main.rs:2:5
  |
2 | /     if let x = 5 {
3 | |         println!("{}", x);
4 | |     };
  | |_____^
  |
  = note: `#[warn(irrefutable_let_patterns)]` on by default

    Finished dev [unoptimized + debuginfo] target(s) in 0.39s
     Running `target/debug/patterns`
5
