Weird Expressions in Rust(wakunguma.com)

        let guess: u32 = match guess.trim().parse() {
            Ok(num) => num,
            Err(_) => return,
        };

    let day_number = match name {
        "Sunday" => 0,
        "Monday" => 1,
        "Tuesday" => 2,
        "Wednesday" => 3,
        "Thursday" => 4,
        "Friday" => 5,
        "Saturday" => 6,
        _ => return Err("invalid day")
    };

  let name = match color_code {
    0 => "red",
    1 => "blue",
    2 => "green",
    _ => "unknown",
  };

  let name = match color_code {
    0 => "red",
    1 => "blue",
    2 => "green",
    _ => return Err("unknown color"),
  };

  let x = if cond { a } else { b };

  const x;  // but x's value will depend on a computation:
  // This is illegal.
  if(foo) {
    x = 3;
  } else {
    x = 4;
  }
  // It's doable, but ugly:
  const x = (function() { if(foo) { return 3; } else { return 4; }})();
  // (Yes, you can do this example with a ternary.
  // Imagine the if branches are a bit more complicated than a ternary,
  // e.g., like 2 statements.)
  

  let x = loop {
    // e.g., find a value in a datastructure. Compute something. Etc.
    if all_done {
      break result;
    }
  };

  let x = {
    // compute x; intermediate variables are properly scoped
    // & cleaned up at block close.
    //
    // There's also a slight visual benefit of "here we compute x" is
    // pretty clearly denoted.
  };

    enum MyEmptyType {} // MyEmptyType has no possible values

  type __ *[]*__