error[]8;;https://doc.rust-lang.org/error_codes/E0308.htmlE0308]8;;]: mismatched types
  --> $DIR/terminal_urls.rs:3:9
   |
LL |     let () = 4;
   |         ^^   - this expression has type `{integer}`
   |         |
   |         expected integer, found `()`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.