stabilize offset_of_enum

Author: fee1-dead

compiler/rustc_error_codes/src/error_codes/E0795.md

@@ -3,8 +3,6 @@ Invalid argument for the `offset_of!` macro.
 Erroneous code example:
 
 ```compile_fail,E0795
-#![feature(offset_of_enum)]
-
 let x = std::mem::offset_of!(Option<u8>, Some);
 ```
 
@@ -16,8 +14,6 @@ The offset of the contained `u8` in the `Option<u8>` can be found by specifying
 the field name `0`:
 
 ```
-#![feature(offset_of_enum)]
-
 let x: usize = std::mem::offset_of!(Option<u8>, Some.0);
 ```
 

compiler/rustc_feature/src/accepted.rs

@@ -328,6 +328,8 @@ declare_features! (
     (accepted, non_exhaustive, "1.40.0", Some(44109)),
     /// Allows `foo.rs` as an alternative to `foo/mod.rs`.
     (accepted, non_modrs_mods, "1.30.0", Some(44660)),
+    /// Allows using enums in offset_of!
+    (accepted, offset_of_enum, "CURRENT_RUSTC_VERSION", Some(120141)),
     /// Allows using multiple nested field accesses in offset_of!
     (accepted, offset_of_nested, "1.82.0", Some(120140)),
     /// Allows the use of or-patterns (e.g., `0 | 1`).

compiler/rustc_feature/src/unstable.rs

@@ -597,8 +597,6 @@ declare_features! (
     (unstable, non_exhaustive_omitted_patterns_lint, "1.57.0", Some(89554)),
     /// Allows `for<T>` binders in where-clauses
     (incomplete, non_lifetime_binders, "1.69.0", Some(108185)),
-    /// Allows using enums in offset_of!
-    (unstable, offset_of_enum, "1.75.0", Some(120141)),
     /// Allows using fields with slice type in offset_of!
     (unstable, offset_of_slice, "1.81.0", Some(126151)),
     /// Allows using `#[optimize(X)]`.

compiler/rustc_hir_typeck/src/expr.rs

@@ -3847,16 +3847,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let (ident, _def_scope) =
                         self.tcx.adjust_ident_and_get_scope(field, container_def.did(), block);
 
-                    if !self.tcx.features().offset_of_enum() {
-                        rustc_session::parse::feature_err(
-                            &self.tcx.sess,
-                            sym::offset_of_enum,
-                            ident.span,
-                            "using enums in offset_of is experimental",
-                        )
-                        .emit();
-                    }
-
                     let Some((index, variant)) = container_def
                         .variants()
                         .iter_enumerated()

library/core/src/lib.rs

@@ -113,7 +113,6 @@
 #![feature(is_ascii_octdigit)]
 #![feature(lazy_get)]
 #![feature(link_cfg)]
-#![feature(offset_of_enum)]
 #![feature(panic_internals)]
 #![feature(ptr_alignment_type)]
 #![feature(ptr_metadata)]

library/core/src/mem/mod.rs

@@ -1365,7 +1365,6 @@ impl<T> SizedTypeProperties for T {}
 ///
 /// The following unstable features expand the functionality of `offset_of!`:
 ///
-/// * [`offset_of_enum`] — allows `enum` variants to be traversed as if they were fields.
 /// * [`offset_of_slice`] — allows getting the offset of a field of type `[T]`.
 ///
 /// # Examples
@@ -1392,10 +1391,20 @@ impl<T> SizedTypeProperties for T {}
 /// struct NestedB(u8);
 ///
 /// assert_eq!(mem::offset_of!(NestedA, b.0), 0);
+///
+/// #[repr(u8)]
+/// enum Enum {
+///    A(u8, u16),
+///    B { one: u8, two: u16 },
+/// }
+///
+/// assert_eq!(mem::offset_of!(Enum, A.0), 1);
+/// assert_eq!(mem::offset_of!(Enum, B.two), 2);
+///
+/// assert_eq!(mem::offset_of!(Option<&u8>, Some.0), 0);
 /// ```
 ///
 /// [dynamically sized]: https://doc.rust-lang.org/reference/dynamically-sized-types.html
-/// [`offset_of_enum`]: https://doc.rust-lang.org/nightly/unstable-book/language-features/offset-of-enum.html
 /// [`offset_of_slice`]: https://doc.rust-lang.org/nightly/unstable-book/language-features/offset-of-slice.html
 #[stable(feature = "offset_of", since = "1.77.0")]
 #[allow_internal_unstable(builtin_syntax)]

src/doc/unstable-book/src/language-features/offset-of-enum.md

@@ -2,8 +2,6 @@
 //@ test-mir-pass: GVN
 // EMIT_MIR_FOR_EACH_PANIC_STRATEGY
 
-#![feature(offset_of_enum)]
-
 use std::marker::PhantomData;
 use std::mem::offset_of;