Add regression test.

Author: jseyfried

src/test/compile-fail-fulldeps/proc-macro/auxiliary/derive-a-b.rs

@@ -0,0 +1,28 @@
+// 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;
+use proc_macro::TokenStream;
+
+#[proc_macro_derive(A)]
+pub fn derive_a(_: TokenStream) -> TokenStream {
+    "".parse().unwrap()
+}
+
+#[proc_macro_derive(B)]
+pub fn derive_b(_: TokenStream) -> TokenStream {
+    "".parse().unwrap()
+}

src/test/compile-fail-fulldeps/proc-macro/issue-37788.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:derive-a-b.rs
+
+#![feature(proc_macro)]
+
+#[macro_use]
+extern crate derive_a_b;
+
+fn main() {
+    // Test that constructing the `visible_parent_map` (in `cstore_impl.rs`) does not ICE.
+    std::cell::Cell::new(0) //~ ERROR mismatched types
+}