From 0f1eb8a70f0f877eba4b55151949df8861377c65 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Sat, 18 Mar 2017 12:28:34 -0400
Subject: [PATCH] add regression test for #39984

Fixes #39984
---
 src/test/run-pass/issue-39984.rs | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 src/test/run-pass/issue-39984.rs

diff --git a/src/test/run-pass/issue-39984.rs b/src/test/run-pass/issue-39984.rs
new file mode 100644
index 0000000000000..a0019e7215c98
--- /dev/null
+++ b/src/test/run-pass/issue-39984.rs
@@ -0,0 +1,21 @@
+// Copyright 2016 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.
+
+// Regression test for issue #39984.
+//
+// The key here is that the error type of the `Ok` call ought to be
+// constrained to `String`, even though it is dead-code.
+
+fn main() {}
+
+fn t() -> Result<(), String> {
+    return Err("".into());
+    Ok(())
+}