Add regression test where private item with intermediate doc hidden re-export was not inlined

Author: GuillaumeGomez

tests/rustdoc/inline-private-with-intermediate-doc-hidden.rs

@@ -0,0 +1,23 @@
+// This test ensures that if a private item is re-exported with an intermediate
+// `#[doc(hidden)]` re-export, it'll still be inlined (and not include any attribute
+// from the doc hidden re-export.
+
+#![crate_name = "foo"]
+
+// @has 'foo/index.html'
+// There should only be one struct displayed.
+// @count - '//*[@id="main-content"]/*[@class="small-section-header"]' 1
+// @has - '//*[@id="main-content"]/*[@class="small-section-header"]' 'Structs'
+// @has - '//*[@id="main-content"]//a[@href="struct.Reexport.html"]' 'Reexport'
+// @has - '//*[@id="main-content"]//*[@class="desc docblock-short"]' 'Visible. Original.'
+
+mod private {
+    /// Original.
+    pub struct Bar3;
+}
+
+/// Hidden.
+#[doc(hidden)]
+pub use crate::private::Bar3;
+/// Visible.
+pub use self::Bar3 as Reexport;