ensure to have explicit main functions in typestate pattern

src/idiomatic/leveraging-the-type-system/typestate-pattern.md

@@ -32,12 +32,14 @@ impl SerializeStruct {
     }
 }
 
-let ser = Serializer::default()
+fn main() {
+    let ser = Serializer::default()
         .serialize_struct("User")
         .serialize_field("id", "42")
         .serialize_field("name", "Alice")
         .finish_struct();
-println!("{}", ser.output);
+    println!("{}", ser.output);
+}
 ```
 
 <details>

src/idiomatic/leveraging-the-type-system/typestate-pattern/typestate-generics.md

@@ -5,7 +5,6 @@ shared logic across state variants, while still encoding state transitions in
 the type system.
 
 ```rust
-# fn main() -> std::io::Result<()> {
 #[non_exhaustive]
 struct Insecure;
 struct Secure {
@@ -85,13 +84,14 @@ impl<T: Transport> ConnectionBuilder<Ready<T>> {
     }
 }
 
-let _conn = Connection::new("db.local")
+fn main() -> std::io::Result<()> {
+    let _conn = Connection::new("db.local")
         .secure()
         .client_certificate(vec![1, 2, 3])
         .timeout(10)
         .connect()?;
-Ok(())
+    Ok(())
-# }
+}
 ```
 
 <details>