Add rustdoc test to ensure that items into a doc(hidden) block are handled as expected

tests/rustdoc/hidden-private.rs

@@ -0,0 +1,50 @@
+// This is a regression test for <https://github.com/rust-lang/rust/issues/106373>.
+// It ensures that the items in the `doc(hidden)` const block don't show up in the
+// generated docs.
+
+// compile-flags: --document-private-items
+
+#![crate_name = "foo"]
+
+// @has 'foo/index.html'
+// @count - '//*[@class="item-table"]//a[@class="struct"]' 2
+// @count - '//*[@class="item-table"]//a[@class="trait"]' 1
+// @count - '//*[@class="item-table"]//a[@class="macro"]' 0
+#[doc(hidden)]
+const _: () = {
+    macro_rules! stry {
+        () => {};
+    }
+
+    struct ShouldBeHidden;
+
+    // @has 'foo/struct.Foo.html'
+    // @!has - '//*[@class="code-header"]' 'impl Bar for Foo'
+    #[doc(hidden)]
+    impl Bar for Foo {
+        fn bar(&self) {
+            struct SHouldAlsoBeHidden;
+        }
+    }
+
+    // @has 'foo/struct.Private.html'
+    // @has - '//*[@id="impl-Bar-for-Private"]/*[@class="code-header"]' 'impl Bar for Private'
+    // @has - '//*[@id="method.bar"]/*[@class="code-header"]' 'fn bar(&self)'
+    impl Bar for Private {
+        fn bar(&self) {}
+    }
+
+    // @has - '//*[@id="impl-Private"]/*[@class="code-header"]' 'impl Private'
+    // @has - '//*[@id="method.tralala"]/*[@class="code-header"]' 'fn tralala()'
+    impl Private {
+        fn tralala() {}
+    }
+};
+
+
+struct Private;
+pub struct Foo;
+
+pub trait Bar {
+    fn bar(&self);
+}