Stabilize doc_cfg feature

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -257,7 +257,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
 
                 gate_doc!(
                     include => external_doc
-                    cfg => doc_cfg
                     masked => doc_masked
                     spotlight => doc_spotlight
                     keyword => doc_keyword

compiler/rustc_feature/src/accepted.rs

@@ -274,6 +274,10 @@ declare_features! (
     /// For example, you can write `Foo(a, ref b)` where `a` is by-move and `b` is by-ref.
     (accepted, move_ref_pattern, "1.48.0", Some(68354), None),
 
+    /// Allows `#[doc(cfg(...))]`. It adds information about under which condition an item is
+    /// available.
+    (active, doc_cfg, "1.50.0", Some(43781), None),
+
     // -------------------------------------------------------------------------
     // feature-group-end: accepted features
     // -------------------------------------------------------------------------

compiler/rustc_feature/src/active.rs

@@ -367,9 +367,6 @@ declare_features! (
     /// Allows defining generators.
     (active, generators, "1.21.0", Some(43122), None),
 
-    /// Allows `#[doc(cfg(...))]`.
-    (active, doc_cfg, "1.21.0", Some(43781), None),
-
     /// Allows `#[doc(masked)]`.
     (active, doc_masked, "1.21.0", Some(44027), None),
 

library/core/src/lib.rs

@@ -104,7 +104,7 @@
 #![feature(const_unreachable_unchecked)]
 #![feature(custom_inner_attributes)]
 #![feature(decl_macro)]
-#![feature(doc_cfg)]
+#![cfg_attr(bootstrap, doc_cfg)]
 #![feature(doc_spotlight)]
 #![feature(duration_consts_2)]
 #![feature(duration_saturating_ops)]

library/std/src/lib.rs

@@ -251,7 +251,7 @@
 #![feature(core_intrinsics)]
 #![feature(custom_test_frameworks)]
 #![feature(decl_macro)]
-#![feature(doc_cfg)]
+#![cfg_attr(bootstrap, doc_cfg)]
 #![feature(doc_keyword)]
 #![feature(doc_masked)]
 #![feature(doc_spotlight)]

src/doc/rustdoc/src/advanced-features.md

@@ -2,6 +2,41 @@
 
 The features listed on this page fall outside the rest of the main categories.
 
+### `#[doc(cfg)]`: Recording what platforms or features are required for code to be present
+
+You can use `#[doc(cfg(...))]` to tell Rustdoc exactly which platform items appear on.
+This has two effects:
+
+1. doctests will only run on the appropriate platforms, and
+2. When Rustdoc renders documentation for that item, it will be accompanied by a banner explaining
+   that the item is only available on certain platforms.
+
+`#[doc(cfg)]` is intended to be used alongside `#[cfg(doc)]` (described a bit below on this same
+page). For example, `#[cfg(any(windows, doc))]` will preserve the item either on Windows or during
+the documentation process. Then, adding a new attribute `#[doc(cfg(windows))]` will tell Rustdoc
+that the item is supposed to be used on Windows. For example:
+
+```rust
+/// Token struct that can only be used on Windows.
+#[cfg(any(windows, doc))]
+#[doc(cfg(windows))]
+pub struct WindowsToken;
+
+/// Token struct that can only be used on Unix.
+#[cfg(any(unix, doc))]
+#[doc(cfg(unix))]
+pub struct UnixToken;
+
+/// Token struct that is only available with the `serde` feature
+#[cfg(feature = "serde")]
+#[doc(cfg(feature = "serde"))]
+#[derive(serde::Deserialize)]
+pub struct SerdeToken;
+```
+
+In this sample, the tokens will only appear on their respective platforms, but they will both appear
+in documentation.
+
 ## `#[cfg(doc)]`: Documenting platform-specific or feature-specific information
 
 For conditional compilation, Rustdoc treats your crate the same way the compiler does. Only things

src/doc/rustdoc/src/the-doc-attribute.md

@@ -214,3 +214,10 @@ the `strip-hidden` pass is removed.
 Since primitive types are defined in the compiler, there's no place to attach documentation
 attributes. This attribute is used by the standard library to provide a way to generate
 documentation for primitive types.
+
+## `#[doc(cfg)]`
+
+You can use `#[doc(cfg(...))]` to tell Rustdoc exactly which platform items appear on. For more
+information, take a look at the [advanced-features][advanced-features] chapter.
+
+[advanced-features]: ./advanced-features.md

src/doc/rustdoc/src/unstable-features.md

@@ -43,51 +43,6 @@ plain text.
 These features operate by extending the `#[doc]` attribute, and thus can be caught by the compiler
 and enabled with a `#![feature(...)]` attribute in your crate.
 
-### `#[doc(cfg)]`: Recording what platforms or features are required for code to be present
-
-You can use `#[doc(cfg(...))]` to tell Rustdoc exactly which platform items appear on.
-This has two effects:
-
-1. doctests will only run on the appropriate platforms, and
-2. When Rustdoc renders documentation for that item, it will be accompanied by a banner explaining
-   that the item is only available on certain platforms.
-
-`#[doc(cfg)]` is intended to be used alongside [`#[cfg(doc)]`][cfg-doc].
-For example, `#[cfg(any(windows, doc))]` will preserve the item either on Windows or during the
-documentation process. Then, adding a new attribute `#[doc(cfg(windows))]` will tell Rustdoc that
-the item is supposed to be used on Windows. For example:
-
-```rust
-#![feature(doc_cfg)]
-
-/// Token struct that can only be used on Windows.
-#[cfg(any(windows, doc))]
-#[doc(cfg(windows))]
-pub struct WindowsToken;
-
-/// Token struct that can only be used on Unix.
-#[cfg(any(unix, doc))]
-#[doc(cfg(unix))]
-pub struct UnixToken;
-
-/// Token struct that is only available with the `serde` feature
-#[cfg(feature = "serde")]
-#[doc(cfg(feature = "serde"))]
-#[derive(serde::Deserialize)]
-pub struct SerdeToken;
-```
-
-In this sample, the tokens will only appear on their respective platforms, but they will both appear
-in documentation.
-
-`#[doc(cfg(...))]` was introduced to be used by the standard library and currently requires the
-`#![feature(doc_cfg)]` feature gate. For more information, see [its chapter in the Unstable
-Book][unstable-doc-cfg] and [its tracking issue][issue-doc-cfg].
-
-[cfg-doc]: ./advanced-features.md
-[unstable-doc-cfg]: ../unstable-book/language-features/doc-cfg.html
-[issue-doc-cfg]: https://github.com/rust-lang/rust/issues/43781
-
 ### Adding your trait to the "Important Traits" dialog
 
 Rustdoc keeps a list of a few traits that are believed to be "fundamental" to a given type when