Add run-pass test

src/test/run-pass/issue-49854.rs

@@ -0,0 +1,18 @@
+// 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.
+
+use std::ffi::OsString;
+
+fn main() {
+    let os_str = OsString::from("Hello Rust!");
+
+    assert_eq!(os_str, "Hello Rust!");
+    assert_eq!("Hello Rust!", os_str);
+}