Add test for #105022

Author: aDotInTheVoid

src/test/rustdoc-json/reexport/auxiliary/trait_with_docs.rs

@@ -0,0 +1,2 @@
+/// The Docs
+pub trait HasDocs {}

src/test/rustdoc-json/reexport/synthesize_trait_with_docs.rs

@@ -0,0 +1,10 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/105022>
+// aux-build: trait_with_docs.rs
+
+extern crate trait_with_docs;
+
+pub struct Local;
+
+impl trait_with_docs::HasDocs for Local {}
+
+// @!has "$.index[*][?(@.name == 'HasDocs')]"