Make code examples pass mdbook test.

Author: SebastianJL

src/flow_control/let_else.md

@@ -9,6 +9,8 @@ in the surrounding scope like a normal `let`, or else diverge (e.g. `break`,
 `return`, `panic!`) when the pattern doesn't match.
 
 ```rust
+use std::str::FromStr;
+
 fn get_count_item(s: &str) -> (u64, &str) {
     let mut it = s.split(' ');
     let (Some(count_str), Some(item)) = (it.next(), it.next()) else {
@@ -19,6 +21,7 @@ fn get_count_item(s: &str) -> (u64, &str) {
     };
     (count, item)
 }
+
 assert_eq!(get_count_item("3 chairs"), (3, "chairs"));
 ```
 
@@ -27,6 +30,10 @@ The scope of name bindings is the main thing that makes this different from
 patterns with an unfortunate bit of repetition and an outer `let`:
 
 ```rust
+# use std::str::FromStr;
+# 
+# fn get_count_item(s: &str) -> (u64, &str) {
+#     let mut it = s.split(' ');
     let (count_str, item) = match (it.next(), it.next()) {
         (Some(count_str), Some(item)) => (count_str, item),
         _ => panic!("Can't segment count item pair: '{s}'"),
@@ -36,6 +43,10 @@ patterns with an unfortunate bit of repetition and an outer `let`:
     } else {
         panic!("Can't parse integer: '{count_str}'");
     };
+#     (count, item)
+# }
+# 
+# assert_eq!(get_count_item("3 chairs"), (3, "chairs"));
 ```
 
 ### See also: