Add regression test.

src/test/run-pass-fulldeps/proc-macro/auxiliary/issue-39889.rs

@@ -0,0 +1,27 @@
+// 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.
+
+// force-host
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+use proc_macro::TokenStream;
+
+#[proc_macro_derive(Issue39889)]
+pub fn f(_input: TokenStream) -> TokenStream {
+    let rules = r#"
+        macro_rules! id {
+            ($($tt:tt)*) => { $($tt)* };
+        }
+    "#;
+    rules.parse().unwrap()
+}

src/test/run-pass-fulldeps/proc-macro/issue-39889.rs

@@ -0,0 +1,22 @@
+// 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.
+
+// aux-build:issue-39889.rs
+
+#![feature(proc_macro)]
+#![allow(unused)]
+
+extern crate issue_39889;
+use issue_39889::Issue39889;
+
+#[derive(Issue39889)]
+struct S;
+
+fn main() {}