Auto merge of #138907 - GuillaumeGomez:rfc-3631, r=fmease,camelid,Manishearth,lolbinarycat

Implement RFC 3631: add rustdoc doc_cfg features

Implementation of https://github.com/rust-lang/rfcs/pull/3631.

This implementation actually resulted in a lot of simplifications:
 * All `cfg` computation is now done in one place: `propagate_doc_cfg.rs`. Because (trait) `impl`s are not retrieved at the same time as the other items, we cannot perform this computation in the clean process, it needs to be after.
 * Because there is `cfg` inheritance, we can keep track of them in one place (in `propagate_doc_cfg.rs`), meaning we don't need to copy an item's attributes to its children anymore. Only exception: impl items. For them we clone only `cfg` attributes.
 * `propagate_doc_cfg.rs` is also now much simpler, much less need to keep track of parents, since everything we need is handled by the new `CfgInfo` type.
 * I also suspect that `Cfg::simplify_with` could either be removed or at least used directly into `propagate_doc_cfg.rs` when we compute `cfg`s. Considering how big the PR already is, I'll do it in a follow-up.

I didn't remove the `doc_cfg*` features in this PR because some dependencies used in `rustc` (like `stdarch`) are using it, so we need to have a nightly released with this PR before I can switch to the new feature.

r? ghost

3 files changed, 4 insertions, 14 deletions

diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index cba1ce40f75..fc3266b7479 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -64,14 +64,7 @@
     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
     test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
 )]
-#![doc(cfg_hide(
-    not(test),
-    no_global_oom_handling,
-    not(no_global_oom_handling),
-    not(no_rc),
-    not(no_sync),
-    target_has_atomic = "ptr"
-))]
+#![doc(auto_cfg(hide(no_global_oom_handling, no_rc, no_sync, target_has_atomic = "ptr")))]
 #![doc(rust_logo)]
 #![feature(rustdoc_internals)]
 #![no_std]
@@ -195,7 +188,6 @@
 //
 // Rustdoc features:
 #![feature(doc_cfg)]
-#![feature(doc_cfg_hide)]
 // Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
 // blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
 // that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 5d52bfb1b12..54adf97f100 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -51,7 +51,7 @@
     test(attr(allow(dead_code, deprecated, unused_variables, unused_mut)))
 )]
 #![doc(rust_logo)]
-#![doc(cfg_hide(
+#![doc(auto_cfg(hide(
     no_fp_fmt_parse,
     target_pointer_width = "16",
     target_pointer_width = "32",
@@ -71,7 +71,7 @@
     target_has_atomic_load_store = "32",
     target_has_atomic_load_store = "64",
     target_has_atomic_load_store = "ptr",
-))]
+)))]
 #![no_core]
 #![rustc_coherence_is_core]
 #![rustc_preserve_ub_checks]
@@ -149,7 +149,6 @@
 #![feature(deprecated_suggestion)]
 #![feature(derive_const)]
 #![feature(doc_cfg)]
-#![feature(doc_cfg_hide)]
 #![feature(doc_notable_trait)]
 #![feature(extern_types)]
 #![feature(f16)]
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 233e41aa345..61b7d170b8b 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -235,7 +235,7 @@
     test(attr(allow(dead_code, deprecated, unused_variables, unused_mut)))
 )]
 #![doc(rust_logo)]
-#![doc(cfg_hide(not(test), no_global_oom_handling, not(no_global_oom_handling)))]
+#![doc(auto_cfg(hide(no_global_oom_handling)))]
 // Don't link to std. We are std.
 #![no_std]
 // Tell the compiler to link to either panic_abort or panic_unwind
@@ -285,7 +285,6 @@
 #![feature(decl_macro)]
 #![feature(deprecated_suggestion)]
 #![feature(doc_cfg)]
-#![feature(doc_cfg_hide)]
 #![feature(doc_masked)]
 #![feature(doc_notable_trait)]
 #![feature(dropck_eyepatch)]