Rollup merge of rust-lang#148683 - fmease:rm-const_trait-attr, r=fee1-dead

Remove `#[const_trait]`

Remove `#[const_trait]` since we now have `const trait`. Update all structured diagnostics that still suggested the attribute.

r? ```@rust-lang/project-const-traits```

Author: matthiaskrgr

core/src/array/equality.rs

@@ -132,9 +132,8 @@ where
 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
 impl<T: [const] Eq, const N: usize> const Eq for [T; N] {}
 
-#[const_trait]
 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
-trait SpecArrayEq<Other, const N: usize>: Sized {
+const trait SpecArrayEq<Other, const N: usize>: Sized {
     fn spec_eq(a: &[Self; N], b: &[Other; N]) -> bool;
     fn spec_ne(a: &[Self; N], b: &[Other; N]) -> bool;
 }

core/src/cmp/bytewise.rs

@@ -17,8 +17,7 @@ use crate::num::NonZero;
 /// - Neither `Self` nor `Rhs` have provenance, so integer comparisons are correct.
 /// - `<Self as PartialEq<Rhs>>::{eq,ne}` are equivalent to comparing the bytes.
 #[rustc_specialization_trait]
-#[const_trait] // FIXME(const_trait_impl): Migrate to `const unsafe trait` once #146122 is fixed.
-pub(crate) unsafe trait BytewiseEq<Rhs = Self>:
+pub(crate) const unsafe trait BytewiseEq<Rhs = Self>:
     [const] PartialEq<Rhs> + Sized
 {
 }

core/src/ops/range.rs

@@ -816,9 +816,8 @@ impl<T: Clone> Bound<&T> {
 /// by range syntax like `..`, `a..`, `..b`, `..=c`, `d..e`, or `f..=g`.
 #[stable(feature = "collections_range", since = "1.28.0")]
 #[rustc_diagnostic_item = "RangeBounds"]
-#[const_trait]
 #[rustc_const_unstable(feature = "const_range", issue = "none")]
-pub trait RangeBounds<T: ?Sized> {
+pub const trait RangeBounds<T: ?Sized> {
     /// Start index bound.
     ///
     /// Returns the start value as a `Bound`.
@@ -954,9 +953,8 @@ pub trait RangeBounds<T: ?Sized> {
 /// `IntoBounds` is implemented by Rust’s built-in range types, produced
 /// by range syntax like `..`, `a..`, `..b`, `..=c`, `d..e`, or `f..=g`.
 #[unstable(feature = "range_into_bounds", issue = "136903")]
-#[const_trait]
 #[rustc_const_unstable(feature = "const_range", issue = "none")]
-pub trait IntoBounds<T>: [const] RangeBounds<T> {
+pub const trait IntoBounds<T>: [const] RangeBounds<T> {
     /// Convert this range into the start and end bounds.
     /// Returns `(start_bound, end_bound)`.
     ///
@@ -1319,9 +1317,8 @@ pub enum OneSidedRangeBound {
 /// Types that implement `OneSidedRange<T>` must return `Bound::Unbounded`
 /// from one of `RangeBounds::start_bound` or `RangeBounds::end_bound`.
 #[unstable(feature = "one_sided_range", issue = "69780")]
-#[const_trait]
 #[rustc_const_unstable(feature = "const_range", issue = "none")]
-pub trait OneSidedRange<T>: RangeBounds<T> {
+pub const trait OneSidedRange<T>: RangeBounds<T> {
     /// An internal-only helper function for `split_off` and
     /// `split_off_mut` that returns the bound of the one-sided range.
     fn bound(self) -> (OneSidedRangeBound, T);

core/src/slice/cmp.rs

@@ -155,18 +155,16 @@ where
 }
 
 #[doc(hidden)]
-#[const_trait]
 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
 // intermediate trait for specialization of slice's PartialOrd
-trait SlicePartialOrd: Sized {
+const trait SlicePartialOrd: Sized {
     fn partial_compare(left: &[Self], right: &[Self]) -> Option<Ordering>;
 }
 
 #[doc(hidden)]
-#[const_trait]
 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
 // intermediate trait for specialization of slice's PartialOrd chaining methods
-trait SliceChain: Sized {
+const trait SliceChain: Sized {
     fn chaining_lt(left: &[Self], right: &[Self]) -> ControlFlow<bool>;
     fn chaining_le(left: &[Self], right: &[Self]) -> ControlFlow<bool>;
     fn chaining_gt(left: &[Self], right: &[Self]) -> ControlFlow<bool>;
@@ -244,9 +242,8 @@ impl<A: [const] AlwaysApplicableOrd> const SlicePartialOrd for A {
 }
 
 #[rustc_specialization_trait]
-#[const_trait]
 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
-trait AlwaysApplicableOrd: [const] SliceOrd + [const] Ord {}
+const trait AlwaysApplicableOrd: [const] SliceOrd + [const] Ord {}
 
 macro_rules! always_applicable_ord {
     ($([$($p:tt)*] $t:ty,)*) => {
@@ -265,10 +262,9 @@ always_applicable_ord! {
 }
 
 #[doc(hidden)]
-#[const_trait]
 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
 // intermediate trait for specialization of slice's Ord
-trait SliceOrd: Sized {
+const trait SliceOrd: Sized {
     fn compare(left: &[Self], right: &[Self]) -> Ordering;
 }
 
@@ -292,8 +288,7 @@ impl<A: Ord> SliceOrd for A {
 /// * For every `x` and `y` of this type, `Ord(x, y)` must return the same
 ///   value as `Ord::cmp(transmute::<_, u8>(x), transmute::<_, u8>(y))`.
 #[rustc_specialization_trait]
-#[const_trait]
-unsafe trait UnsignedBytewiseOrd: [const] Ord {}
+const unsafe trait UnsignedBytewiseOrd: [const] Ord {}
 
 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
 unsafe impl const UnsignedBytewiseOrd for bool {}

core/src/slice/index.rs

@@ -159,9 +159,8 @@ mod private_slice_index {
     message = "the type `{T}` cannot be indexed by `{Self}`",
     label = "slice indices are of type `usize` or ranges of `usize`"
 )]
-#[const_trait] // FIXME(const_trait_impl): Migrate to `const unsafe trait` once #146122 is fixed.
 #[rustc_const_unstable(feature = "const_index", issue = "143775")]
-pub unsafe trait SliceIndex<T: ?Sized>: private_slice_index::Sealed {
+pub const unsafe trait SliceIndex<T: ?Sized>: private_slice_index::Sealed {
     /// The output type returned by methods.
     #[stable(feature = "slice_get_slice", since = "1.28.0")]
     type Output: ?Sized;