Add test for #108570.

Update UI test with new output.

Author: GuillaumeGomez

tests/ui/lint/issue-108570-missing-docs-on-hidden.rs

@@ -0,0 +1,17 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/108570>.
+// If a `#[doc(hidden)]` item is re-exported or if a private item is re-exported
+// with a `#[doc(hidden)]` re-export, it shouldn't complain.
+
+// check-pass
+
+#![crate_type = "lib"]
+
+mod priv_mod {
+    pub struct Foo;
+    #[doc(hidden)]
+    pub struct Bar;
+}
+
+#[doc(hidden)]
+pub use priv_mod::Foo;
+pub use priv_mod::Bar;

tests/ui/lint/lint-missing-doc.stderr

@@ -117,18 +117,36 @@ error: missing documentation for a function
    |
 LL |     pub fn undocumented1() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: because it is re-exported here
+  --> $DIR/lint-missing-doc.rs:183:5
+   |
+LL |     pub use internal_impl::undocumented1 as bar;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: missing documentation for a function
   --> $DIR/lint-missing-doc.rs:170:5
    |
 LL |     pub fn undocumented2() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: because it is re-exported here
+  --> $DIR/lint-missing-doc.rs:184:41
+   |
+LL |     pub use internal_impl::{documented, undocumented2};
+   |                                         ^^^^^^^^^^^^^
 
 error: missing documentation for a function
   --> $DIR/lint-missing-doc.rs:176:9
    |
 LL |         pub fn also_undocumented1() {}
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: because it is re-exported here
+  --> $DIR/lint-missing-doc.rs:185:5
+   |
+LL |     pub use internal_impl::globbed::*;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: missing documentation for a function
   --> $DIR/lint-missing-doc.rs:191:5

tests/ui/privacy/auxiliary/ctor_aux.rs

@@ -3,7 +3,7 @@
 //! Use the lint to additionally verify that items are reachable
 //! but not exported.
 #![allow(non_camel_case_types)]
-#![deny(missing_docs)]
+// #![deny(missing_docs)]
 
 mod hidden {
     pub struct s;