2 files changed, 4 insertions, 0 deletions
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 3da92c0a05a..68ef087d84b 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -178,6 +178,7 @@ impl<T> Option<T> {
     /// ```
     ///
     /// [`Some`]: #variant.Some
+    #[must_use]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_some(&self) -> bool {
@@ -200,6 +201,7 @@ impl<T> Option<T> {
     /// ```
     ///
     /// [`None`]: #variant.None
+    #[must_use]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_none(&self) -> bool {
diff --git a/src/libcore/result.rs b/src/libcore/result.rs
index 9b7b8368986..e22a9ebbca4 100644
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -277,6 +277,7 @@ impl<T, E> Result<T, E> {
     /// let x: Result<i32, &str> = Err("Some error message");
     /// assert_eq!(x.is_ok(), false);
     /// ```
+    #[must_use]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_ok(&self) -> bool {
@@ -301,6 +302,7 @@ impl<T, E> Result<T, E> {
     /// let x: Result<i32, &str> = Err("Some error message");
     /// assert_eq!(x.is_err(), true);
     /// ```
+    #[must_use]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_err(&self) -> bool {