1 files changed, 21 insertions, 0 deletions
diff --git a/src/test/ui/macros/must-use-in-macro-55516.rs b/src/test/ui/macros/must-use-in-macro-55516.rs
new file mode 100644
index 00000000000..ad7cc37da52
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+++ b/src/test/ui/macros/must-use-in-macro-55516.rs
@@ -0,0 +1,21 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-pass
+// compile-flags: -Wunused
+
+// make sure write!() can't hide its unused Result
+
+fn main() {
+    use std::fmt::Write;
+    let mut example = String::new();
+    write!(&mut example, "{}", 42); //~WARN must be used
+}
+