Add regression test.

src/test/compile-fail-fulldeps/proc-macro/auxiliary/issue_38586.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.
+
+// force-host
+// no-prefer-dynamic
+
+#![feature(proc_macro, proc_macro_lib)]
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+#[proc_macro_derive(A)]
+pub fn derive_a(_: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    "fn f() { println!(\"{}\", foo); }".parse().unwrap()
+}

src/test/compile-fail-fulldeps/proc-macro/issue-38586.rs

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+// 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_38586.rs
+
+#![feature(proc_macro)]
+
+#[macro_use]
+extern crate issue_38586;
+
+#[derive(A)] //~ ERROR `foo`
+struct A;
+
+fn main() {}