From 145385e7c3fbb242e3024ad0368f2cfd95f5666e Mon Sep 17 00:00:00 2001
From: Chris Gregory <czipperz@gmail.com>
Date: Fri, 5 Jul 2019 20:57:25 -0700
Subject: [PATCH 1/2] Add messages to Option and Result must_use for is_*

---
 src/libcore/option.rs | 4 ++--
 src/libcore/result.rs | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index b27fd4098e167..9174ebae171da 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -178,7 +178,7 @@ impl<T> Option<T> {
     /// ```
     ///
     /// [`Some`]: #variant.Some
-    #[must_use]
+    #[must_use = "if you intended to assert that this has a value, consider `.unwrap()` instead"]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_some(&self) -> bool {
@@ -201,7 +201,7 @@ impl<T> Option<T> {
     /// ```
     ///
     /// [`None`]: #variant.None
-    #[must_use]
+    #[must_use = "if you intended to assert that this doesn't have a value, consider `.and_then(|| panic!(\"`Option` had a value when expected `None`\"))` instead"]
     #[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 8a09877ce1f4b..a31ac212dea24 100644
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -277,7 +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]
+    #[must_use = "if you intended to assert that this is ok, consider `.unwrap()` instead"]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_ok(&self) -> bool {
@@ -302,7 +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]
+    #[must_use = "if you intended to assert that this is err, consider `.unwrap_err()` instead"]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_err(&self) -> bool {

From 9b0623d51f5c9754e63107b50373ff1294c28c61 Mon Sep 17 00:00:00 2001
From: Chris Gregory <czipperz@gmail.com>
Date: Fri, 5 Jul 2019 21:38:35 -0700
Subject: [PATCH 2/2] Wrap line

---
 src/libcore/option.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 9174ebae171da..2c148ec485767 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -201,7 +201,8 @@ impl<T> Option<T> {
     /// ```
     ///
     /// [`None`]: #variant.None
-    #[must_use = "if you intended to assert that this doesn't have a value, consider `.and_then(|| panic!(\"`Option` had a value when expected `None`\"))` instead"]
+    #[must_use = "if you intended to assert that this doesn't have a value, consider \
+                  `.and_then(|| panic!(\"`Option` had a value when expected `None`\"))` instead"]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_none(&self) -> bool {