Yeet some features

Author: compiler-errors

compiler/rustc_type_ir/src/lib.rs

@@ -1,15 +1,6 @@
 #![cfg_attr(
     feature = "nightly",
-    feature(
-        associated_type_defaults,
-        fmt_helpers_for_derive,
-        get_mut_unchecked,
-        min_specialization,
-        never_type,
-        new_uninit,
-        rustc_attrs,
-        unwrap_infallible
-    )
+    feature(associated_type_defaults, min_specialization, never_type, rustc_attrs)
 )]
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]

compiler/rustc_type_ir/src/structural_impls.rs

@@ -131,10 +131,7 @@ impl<I: Interner, T: TypeFoldable<I>> TypeFoldable<I> for Lrc<T> {
             // Call to `Lrc::make_mut` above guarantees that `unique` is the
             // sole reference to the contained value, so we can avoid doing
             // a checked `get_mut` here.
-            #[cfg(feature = "nightly")]
-            let slot = Lrc::get_mut_unchecked(&mut unique);
-            #[cfg(not(feature = "nightly"))]
-            let slot = Lrc::get_mut(&mut unique).unwrap();
+            let slot = Lrc::get_mut(&mut unique).unwrap_unchecked();
 
             // Semantically move the contained type out from `unique`, fold
             // it, then move the folded value back into `unique`. Should