diff options
| -rw-r--r-- | library/core/src/option.rs | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/library/core/src/option.rs b/library/core/src/option.rs index c43b728022d..f485763b234 100644 --- a/library/core/src/option.rs +++ b/library/core/src/option.rs @@ -943,7 +943,7 @@ impl<T> Option<T> { // Transforming contained values ///////////////////////////////////////////////////////////////////////// - /// Maps an `Option<T>` to `Option<U>` by applying a function to a contained value. + /// Maps an `Option<T>` to `Option<U>` by applying a function to a contained value (if `Some`) or return `None` (if `None`). /// /// # Examples /// @@ -955,8 +955,10 @@ impl<T> Option<T> { /// let maybe_some_string = Some(String::from("Hello, World!")); /// // `Option::map` takes self *by value*, consuming `maybe_some_string` /// let maybe_some_len = maybe_some_string.map(|s| s.len()); - /// /// assert_eq!(maybe_some_len, Some(13)); + /// + /// let x: Option<&str> = None; + /// assert_eq!(x.map(|s| s.len()), None); /// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] |