Rollup merge of #46359 - GuillaumeGomez:remove-dead-linkage, r=QuietMisdreavus

Do not display hidden types, fixes issue 23912

Fixes #23912.

r? @QuietMisdreavus

(It's the one I was talking about a few days ago, just close it if it's useless.)

src/test/rustdoc/hidden-trait-struct-impls.rs

@@ -0,0 +1,32 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![crate_name = "foo"]
+
+#[doc(hidden)]
+pub trait Foo {}
+
+trait Dark {}
+
+pub trait Bam {}
+
+pub struct Bar;
+
+struct Hidden;
+
+// @!has foo/struct.Bar.html '//*[@id="impl-Foo"]' 'impl Foo for Bar'
+impl Foo for Bar {}
+// @!has foo/struct.Bar.html '//*[@id="impl-Dark"]' 'impl Dark for Bar'
+impl Dark for Bar {}
+// @has foo/struct.Bar.html '//*[@id="impl-Bam"]' 'impl Bam for Bar'
+// @has foo/trait.Bam.html '//*[@id="implementors-list"]' 'impl Bam for Bar'
+impl Bam for Bar {}
+// @!has foo/trait.Bam.html '//*[@id="implementors-list"]' 'impl Bam for Hidden'
+impl Bam for Hidden {}