Rollup merge of rust-lang#90420 - GuillaumeGomez:rustdoc-internals-feature, r=camelid

Create rustdoc_internals feature gate

As suggested by ``@camelid`` [here](rust-lang#90398 (comment)), since `doc_keyword` and `doc_primitive` aren't meant to be stabilized, we could put them behind a same feature flag.

This is pretty much what it would look like (needs to update the tests too).

The tracking issue is rust-lang#90418.

What do you think ``@rust-lang/rustdoc`` ?

Author: GuillaumeGomez

core/src/lib.rs

@@ -166,7 +166,8 @@
 #![feature(derive_default_enum)]
 #![feature(doc_cfg)]
 #![feature(doc_notable_trait)]
-#![feature(doc_primitive)]
+#![cfg_attr(bootstrap, feature(doc_primitive))]
+#![cfg_attr(not(bootstrap), feature(rustdoc_internals))]
 #![feature(exhaustive_patterns)]
 #![feature(doc_cfg_hide)]
 #![feature(extern_types)]

std/src/lib.rs

@@ -275,10 +275,11 @@
 #![feature(decl_macro)]
 #![feature(doc_cfg)]
 #![feature(doc_cfg_hide)]
-#![feature(doc_keyword)]
+#![cfg_attr(bootstrap, feature(doc_primitive))]
+#![cfg_attr(bootstrap, feature(doc_keyword))]
+#![cfg_attr(not(bootstrap), feature(rustdoc_internals))]
 #![feature(doc_masked)]
 #![feature(doc_notable_trait)]
-#![feature(doc_primitive)]
 #![feature(dropck_eyepatch)]
 #![feature(duration_checked_float)]
 #![feature(duration_constants)]