add regression test

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

@@ -0,0 +1,12 @@
+// aux-build:through-proc-macro-aux.rs
+// build-aux-docs
+#![warn(intra_doc_link_resolution_failure)]
+extern crate some_macros;
+
+#[some_macros::second]
+pub enum Boom {
+    /// [Oooops]
+    Bam,
+}
+
+fn main() {}