From ffa919c8aa0d563cedd975d95f0ed4a697bd6e8e Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Mon, 7 Mar 2022 12:41:58 -0800
Subject: [PATCH] Add must_use to value created by anyhow! macro

---
 src/lib.rs    |  8 ++++++++
 src/macros.rs | 26 +++++++++++++++-----------
 2 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 0cb1ed6..b595300 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -668,4 +668,12 @@ pub mod private {
             Error::msg(fmt::format(args))
         }
     }
+
+    #[doc(hidden)]
+    #[inline]
+    #[cold]
+    #[must_use]
+    pub fn must_use(error: Error) -> Error {
+        error
+    }
 }
diff --git a/src/macros.rs b/src/macros.rs
index 89dc4d2..e92a264 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -206,17 +206,21 @@ macro_rules! ensure {
 /// ```
 #[macro_export]
 macro_rules! anyhow {
-    ($msg:literal $(,)?) => ({
-        let error = $crate::private::format_err($crate::private::format_args!($msg));
-        error
-    });
-    ($err:expr $(,)?) => ({
-        use $crate::private::kind::*;
-        let error = match $err {
-            error => (&error).anyhow_kind().new(error),
-        };
-        error
-    });
+    ($msg:literal $(,)?) => {
+        $crate::private::must_use({
+            let error = $crate::private::format_err($crate::private::format_args!($msg));
+            error
+        })
+    };
+    ($err:expr $(,)?) => {
+        $crate::private::must_use({
+            use $crate::private::kind::*;
+            let error = match $err {
+                error => (&error).anyhow_kind().new(error),
+            };
+            error
+        })
+    };
     ($fmt:expr, $($arg:tt)*) => {
         $crate::Error::msg($crate::private::format!($fmt, $($arg)*))
     };