add test for issue 52129

src/test/rustdoc/doc-proc-macro.rs

+// Copyright 2012-2013 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.
+
+// Issue #52129: ICE when trying to document the `quote` proc-macro from proc_macro
+
+// As of this writing, we don't currently attempt to document proc-macros. However, we shouldn't
+// crash when we try.
+
+extern crate proc_macro;
+
+pub use proc_macro::*;