= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
= note: the return type of a function must have a statically known size
-error: aborting due to 3 previous errors
+error: aborting due to 3 previous errors; 1 warning emitted
For more information about this error, try `rustc --explain E0271`.