X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=library%2Fcore%2Fsrc%2Fbool.rs;h=db1c505ba3851016db993e153efebf7d0ba0a580;hb=4e591884f3acc96b2d3a62b9264131d3aca5c1a7;hp=7667a6508376912d005e04656396d9d811c060fd;hpb=7b30b26145791ef1953c93e8dd8a0175fd53c3ac;p=rust.git

diff --git a/library/core/src/bool.rs b/library/core/src/bool.rs
index 7667a650837..db1c505ba38 100644
--- a/library/core/src/bool.rs
+++ b/library/core/src/bool.rs
@@ -18,6 +18,18 @@ impl bool {
     /// assert_eq!(false.then_some(0), None);
     /// assert_eq!(true.then_some(0), Some(0));
     /// ```
+    ///
+    /// ```
+    /// let mut a = 0;
+    /// let mut function_with_side_effects = || { a += 1; };
+    ///
+    /// true.then_some(function_with_side_effects());
+    /// false.then_some(function_with_side_effects());
+    ///
+    /// // `a` is incremented twice because the value passed to `then_some` is
+    /// // evaluated eagerly.
+    /// assert_eq!(a, 2);
+    /// ```
     #[stable(feature = "bool_to_option", since = "1.62.0")]
     #[rustc_const_unstable(feature = "const_bool_to_option", issue = "91917")]
     #[inline]
@@ -37,6 +49,17 @@ pub const fn then_some<T>(self, t: T) -> Option<T>
     /// assert_eq!(false.then(|| 0), None);
     /// assert_eq!(true.then(|| 0), Some(0));
     /// ```
+    ///
+    /// ```
+    /// let mut a = 0;
+    ///
+    /// true.then(|| { a += 1; });
+    /// false.then(|| { a += 1; });
+    ///
+    /// // `a` is incremented once because the closure is evaluated lazily by
+    /// // `then`.
+    /// assert_eq!(a, 1);
+    /// ```
     #[stable(feature = "lazy_bool_to_option", since = "1.50.0")]
     #[rustc_const_unstable(feature = "const_bool_to_option", issue = "91917")]
     #[inline]