【検討】return の時のSpan設定がおかしいので直す

[anotherhollow1125]

$ cargo build
   Compiling project v0.1.0 (/path/to/project)
error[E0599]: no method named `ok_or_else` found for enum `Result` in the current scope
  --> src/main.rs:31:9
   |
31 |         return Err(format!(
   |         ^^^^^^
   |
help: there is a method `or_else` with a similar name
   |
31 -         return Err(format!(
31 +         or_else Err(format!(
   |

For more information about this error, try `rustc --explain E0599`.
error: could not compile `playground` (bin "playground") due to 1 previous error

? ならば仕方ないが、 ; 等の方がマシに感じるため直す