Rust code may have a plethora of representations of errors, but the standard library has
a universal trait
std::error::Error for describing errors.
Using a smart pointer
Box we can use the type
Box<dyn std::error::Error> as a common type for returning errors because it allows us to
propagate up an error on the heap and interact with it at a high level without having to know a specific type.
Early in Tour of Rust we learned that
main can return an error. We can now return
a type capable of describing almost any kind of error that might occur in our program
so long as the error's data structure implements Rust's common
fn main() -> Result<(), Box<dyn std::error:Error>>