Auto merge of #120242 - matthiaskrgr:rollup-a93yj3i, r=matthiaskrgr

Rollup of 10 pull requests

Successful merges:

 - #117910 (Refactor uses of `objc_msgSend` to no longer have clashing definitions)
 - #118639 (Undeprecate lint `unstable_features` and make use of it in the compiler)
 - #119801 (Fix deallocation with wrong allocator in (A)Rc::from_box_in)
 - #120058 (bootstrap: improvements for compiler builds)
 - #120059 (Make generic const type mismatches not hide trait impls from the trait solver)
 - #120097 (Report unreachable subpatterns consistently)
 - #120137 (Validate AggregateKind types in MIR)
 - #120164 (`maybe_lint_impl_trait`: separate `is_downgradable` from `is_object_safe`)
 - #120181 (Allow any `const` expression blocks in `thread_local!`)
 - #120218 (rustfmt: Check that a token can begin a nonterminal kind before parsing it as a macro arg)

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 27 insertions, 7 deletions

diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 5e1f2ed11ac..2ce78152cc2 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -1233,10 +1233,30 @@ impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
 }
 
 declare_lint! {
-    /// The `unstable_features` is deprecated and should no longer be used.
+    /// The `unstable_features` lint detects uses of `#![feature]`.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(unstable_features)]
+    /// #![feature(test)]
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// In larger nightly-based projects which
+    ///
+    /// * consist of a multitude of crates where a subset of crates has to compile on
+    ///   stable either unconditionally or depending on a `cfg` flag to for example
+    ///   allow stable users to depend on them,
+    /// * don't use nightly for experimental features but for, e.g., unstable options only,
+    ///
+    /// this lint may come in handy to enforce policies of these kinds.
     UNSTABLE_FEATURES,
     Allow,
-    "enabling unstable features (deprecated. do not use)"
+    "enabling unstable features"
 }
 
 declare_lint_pass!(
@@ -1246,11 +1266,11 @@ declare_lint_pass!(
 
 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
     fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
-        if attr.has_name(sym::feature) {
-            if let Some(items) = attr.meta_item_list() {
-                for item in items {
-                    cx.emit_spanned_lint(UNSTABLE_FEATURES, item.span(), BuiltinUnstableFeatures);
-                }
+        if attr.has_name(sym::feature)
+            && let Some(items) = attr.meta_item_list()
+        {
+            for item in items {
+                cx.emit_spanned_lint(UNSTABLE_FEATURES, item.span(), BuiltinUnstableFeatures);
             }
         }
     }