Auto merge of #87768 - rust-lang:core-features-cleanup, r=dtolnay

Core features cleanup

This sorts and categorizes the `#![features]` in `core` and removes unused ones.

This is part of #87766

The following feature attributes were unnecessary and are removed:

```diff
// Library features:
-#![feature(bool_to_option)]
-#![feature(char_indices_offset)]
-#![feature(pin_deref_mut)]
-#![feature(str_split_as_str)]
-#![feature(str_split_inclusive_as_str)]

// Language features:
-#![feature(arbitrary_self_types)]
-#![feature(custom_inner_attributes)]
-#![feature(nll)]
```

library/core/src/internal_macros.rs

@@ -77,7 +77,6 @@ fn $method(&mut self, other: &$u) {
 }
 
 /// Create a zero-size type similar to a closure type, but named.
-#[unstable(feature = "std_internals", issue = "none")]
 macro_rules! impl_fn_for_zst {
     ($(
         $( #[$attr: meta] )*

library/core/src/lib.rs

@@ -61,61 +61,74 @@
     test(attr(allow(dead_code, deprecated, unused_variables, unused_mut)))
 )]
 #![no_core]
+//
+// Lints:
+#![deny(rust_2021_incompatible_or_patterns)]
+#![deny(unsafe_op_in_unsafe_fn)]
 #![warn(deprecated_in_future)]
-#![warn(missing_docs)]
 #![warn(missing_debug_implementations)]
+#![warn(missing_docs)]
 #![allow(explicit_outlives_requirements)]
-#![feature(rustc_allow_const_fn_unstable)]
-#![feature(allow_internal_unstable)]
-#![feature(arbitrary_self_types)]
-#![feature(asm)]
-#![feature(bool_to_option)]
-#![feature(cfg_target_has_atomic)]
-#![feature(const_heap)]
+//
+// Library features for const fns:
+#![feature(const_align_of_val)]
 #![feature(const_alloc_layout)]
 #![feature(const_arguments_as_str)]
 #![feature(const_assert_type)]
-#![feature(const_discriminant)]
+#![feature(const_caller_location)]
 #![feature(const_cell_into_inner)]
+#![feature(const_discriminant)]
+#![feature(const_float_bits_conv)]
+#![feature(const_float_classify)]
+#![feature(const_heap)]
+#![feature(const_inherent_unchecked_arith)]
+#![feature(const_int_unchecked_arith)]
 #![feature(const_intrinsic_copy)]
 #![feature(const_intrinsic_forget)]
-#![feature(const_float_classify)]
-#![feature(const_float_bits_conv)]
-#![feature(const_int_unchecked_arith)]
-#![feature(const_inherent_unchecked_arith)]
-#![feature(const_mut_refs)]
-#![feature(const_refs_to_cell)]
-#![feature(const_panic)]
-#![feature(const_pin)]
-#![cfg_attr(bootstrap, feature(const_fn_union))]
-#![feature(const_impl_trait)]
-#![feature(const_fn_floating_point_arithmetic)]
-#![feature(const_fn_fn_ptr_basics)]
-#![feature(const_fn_trait_bound)]
+#![feature(const_likely)]
+#![feature(const_maybe_uninit_as_ptr)]
+#![feature(const_maybe_uninit_assume_init)]
 #![feature(const_option)]
-#![feature(const_precise_live_drops)]
+#![feature(const_pin)]
 #![feature(const_ptr_offset)]
 #![feature(const_ptr_offset_from)]
 #![feature(const_ptr_read)]
 #![feature(const_ptr_write)]
 #![feature(const_raw_ptr_comparison)]
-#![feature(const_raw_ptr_deref)]
+#![feature(const_size_of_val)]
 #![feature(const_slice_from_raw_parts)]
 #![feature(const_slice_ptr_len)]
-#![feature(const_size_of_val)]
 #![feature(const_swap)]
-#![feature(const_align_of_val)]
 #![feature(const_type_id)]
 #![feature(const_type_name)]
-#![feature(const_likely)]
 #![feature(const_unreachable_unchecked)]
-#![feature(const_maybe_uninit_assume_init)]
-#![feature(const_maybe_uninit_as_ptr)]
-#![feature(custom_inner_attributes)]
+#![feature(duration_consts_2)]
+#![feature(ptr_metadata)]
+#![feature(slice_ptr_get)]
+#![feature(variant_count)]
+//
+// Language features:
+#![feature(abi_unadjusted)]
+#![feature(allow_internal_unstable)]
+#![feature(asm)]
+#![feature(associated_type_bounds)]
+#![feature(auto_traits)]
+#![feature(cfg_target_has_atomic)]
+#![feature(const_fn_floating_point_arithmetic)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_fn_trait_bound)]
+#![cfg_attr(bootstrap, feature(const_fn_transmute))]
+#![cfg_attr(bootstrap, feature(const_fn_union))]
+#![feature(const_impl_trait)]
+#![feature(const_mut_refs)]
+#![feature(const_panic)]
+#![feature(const_precise_live_drops)]
+#![feature(const_raw_ptr_deref)]
+#![feature(const_refs_to_cell)]
 #![feature(decl_macro)]
 #![feature(doc_cfg)]
 #![feature(doc_notable_trait)]
-#![feature(duration_consts_2)]
+#![feature(exhaustive_patterns)]
 #![feature(extern_types)]
 #![feature(fundamental)]
 #![feature(intra_doc_pointers)]
@@ -123,53 +136,40 @@
 #![feature(lang_items)]
 #![feature(link_llvm_intrinsics)]
 #![feature(llvm_asm)]
+#![feature(min_specialization)]
 #![feature(negative_impls)]
 #![feature(never_type)]
-#![feature(nll)]
-#![feature(exhaustive_patterns)]
 #![feature(no_core)]
-#![feature(auto_traits)]
-#![feature(pin_deref_mut)]
+#![feature(no_coverage)] // rust-lang/rust#84605
+#![feature(no_niche)] // rust-lang/rust#68303
+#![feature(platform_intrinsics)]
 #![feature(prelude_import)]
-#![feature(ptr_metadata)]
-#![feature(repr_simd, platform_intrinsics)]
+#![feature(repr_simd)]
+#![feature(rustc_allow_const_fn_unstable)]
 #![feature(rustc_attrs)]
 #![feature(simd_ffi)]
-#![feature(min_specialization)]
 #![feature(staged_api)]
-#![feature(std_internals)]
 #![feature(stmt_expr_attributes)]
-#![feature(str_split_as_str)]
-#![feature(str_split_inclusive_as_str)]
-#![feature(char_indices_offset)]
 #![feature(trait_alias)]
 #![feature(transparent_unions)]
 #![feature(try_blocks)]
 #![feature(unboxed_closures)]
 #![feature(unsized_fn_params)]
-#![feature(variant_count)]
-#![feature(tbm_target_feature)]
-#![feature(sse4a_target_feature)]
-#![feature(arm_target_feature)]
-#![feature(powerpc_target_feature)]
-#![feature(mips_target_feature)]
+//
+// Target features:
 #![feature(aarch64_target_feature)]
-#![feature(wasm_target_feature)]
+#![feature(adx_target_feature)]
+#![feature(arm_target_feature)]
 #![feature(avx512_target_feature)]
 #![feature(cmpxchg16b_target_feature)]
-#![feature(rtm_target_feature)]
 #![feature(f16c_target_feature)]
 #![feature(hexagon_target_feature)]
-#![cfg_attr(bootstrap, feature(const_fn_transmute))]
-#![feature(abi_unadjusted)]
-#![feature(adx_target_feature)]
-#![feature(associated_type_bounds)]
-#![feature(const_caller_location)]
-#![feature(slice_ptr_get)]
-#![feature(no_niche)] // rust-lang/rust#68303
-#![feature(no_coverage)] // rust-lang/rust#84605
-#![deny(unsafe_op_in_unsafe_fn)]
-#![deny(rust_2021_incompatible_or_patterns)]
+#![feature(mips_target_feature)]
+#![feature(powerpc_target_feature)]
+#![feature(rtm_target_feature)]
+#![feature(sse4a_target_feature)]
+#![feature(tbm_target_feature)]
+#![feature(wasm_target_feature)]
 
 // allow using `core::` in intra-doc links
 #[allow(unused_extern_crates)]