Auto merge of #122754 - Mark-Simulacrum:bootstrap-bump, r=albertlarsan68

Bump to 1.78 bootstrap compiler

https://forge.rust-lang.org/release/process.html#master-bootstrap-update-t-2-day-tuesday

library/core/src/convert/mod.rs

@@ -396,7 +396,7 @@ pub trait AsMut<T: ?Sized> {
 /// For example, take this code:
 ///
 /// ```
-/// # #![cfg_attr(not(bootstrap), allow(non_local_definitions))]
+/// # #![allow(non_local_definitions)]
 /// struct Wrapper<T>(Vec<T>);
 /// impl<T> From<Wrapper<T>> for Vec<T> {
 ///     fn from(w: Wrapper<T>) -> Vec<T> {

library/core/src/ffi/c_str.rs

@@ -438,13 +438,7 @@ impl CStr {
             unsafe { &*(bytes as *const [u8] as *const CStr) }
         }
 
-        #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-        // SAFETY: The const and runtime versions have identical behavior
-        // unless the safety contract of `from_bytes_with_nul_unchecked` is
-        // violated, which is UB.
-        unsafe {
-            intrinsics::const_eval_select((bytes,), const_impl, rt_impl)
-        }
+        intrinsics::const_eval_select((bytes,), const_impl, rt_impl)
     }
 
     /// Returns the inner pointer to this C string.
@@ -759,11 +753,7 @@ const unsafe fn const_strlen(ptr: *const c_char) -> usize {
         unsafe { strlen(s) }
     }
 
-    #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-    // SAFETY: the two functions always provide equivalent functionality
-    unsafe {
-        intrinsics::const_eval_select((ptr,), strlen_ct, strlen_rt)
-    }
+    intrinsics::const_eval_select((ptr,), strlen_ct, strlen_rt)
 }
 
 /// An iterator over the bytes of a [`CStr`], without the nul terminator.

library/core/src/hash/mod.rs

@@ -454,7 +454,7 @@ pub trait Hasher {
     /// ```
     /// #![feature(hasher_prefixfree_extras)]
     /// # // Stubs to make the `impl` below pass the compiler
-    /// # #![cfg_attr(not(bootstrap), allow(non_local_definitions))]
+    /// # #![allow(non_local_definitions)]
     /// # struct MyCollection<T>(Option<T>);
     /// # impl<T> MyCollection<T> {
     /// #     fn len(&self) -> usize { todo!() }

library/core/src/intrinsics.rs

@@ -84,9 +84,6 @@ pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
     unsafe { crate::ptr::drop_in_place(to_drop) }
 }
 
-#[cfg(bootstrap)]
-pub use self::r#try as catch_unwind;
-
 extern "rust-intrinsic" {
     // N.B., these intrinsics take raw pointers because they mutate aliased
     // memory, which is not valid for either `&` or `&mut`.
@@ -965,8 +962,7 @@ extern "rust-intrinsic" {
 #[rustc_const_stable(feature = "const_assume", since = "1.77.0")]
 #[rustc_nounwind]
 #[unstable(feature = "core_intrinsics", issue = "none")]
-#[cfg_attr(not(bootstrap), rustc_intrinsic)]
-#[cfg_attr(bootstrap, inline)]
+#[rustc_intrinsic]
 pub const unsafe fn assume(b: bool) {
     if !b {
         // SAFETY: the caller must guarantee the argument is never `false`
@@ -987,9 +983,8 @@ pub const unsafe fn assume(b: bool) {
 /// This intrinsic does not have a stable counterpart.
 #[rustc_const_unstable(feature = "const_likely", issue = "none")]
 #[unstable(feature = "core_intrinsics", issue = "none")]
-#[cfg_attr(not(bootstrap), rustc_intrinsic)]
+#[rustc_intrinsic]
 #[rustc_nounwind]
-#[cfg_attr(bootstrap, inline)]
 pub const fn likely(b: bool) -> bool {
     b
 }
@@ -1007,9 +1002,8 @@ pub const fn likely(b: bool) -> bool {
 /// This intrinsic does not have a stable counterpart.
 #[rustc_const_unstable(feature = "const_likely", issue = "none")]
 #[unstable(feature = "core_intrinsics", issue = "none")]
-#[cfg_attr(not(bootstrap), rustc_intrinsic)]
+#[rustc_intrinsic]
 #[rustc_nounwind]
-#[cfg_attr(bootstrap, inline)]
 pub const fn unlikely(b: bool) -> bool {
     b
 }
@@ -1919,7 +1913,6 @@ extern "rust-intrinsic" {
     /// This intrinsic does not have a stable counterpart.
     #[rustc_nounwind]
     #[rustc_safe_intrinsic]
-    #[cfg(not(bootstrap))]
     pub fn fadd_algebraic<T: Copy>(a: T, b: T) -> T;
 
     /// Float subtraction that allows optimizations based on algebraic rules.
@@ -1927,7 +1920,6 @@ extern "rust-intrinsic" {
     /// This intrinsic does not have a stable counterpart.
     #[rustc_nounwind]
     #[rustc_safe_intrinsic]
-    #[cfg(not(bootstrap))]
     pub fn fsub_algebraic<T: Copy>(a: T, b: T) -> T;
 
     /// Float multiplication that allows optimizations based on algebraic rules.
@@ -1935,7 +1927,6 @@ extern "rust-intrinsic" {
     /// This intrinsic does not have a stable counterpart.
     #[rustc_nounwind]
     #[rustc_safe_intrinsic]
-    #[cfg(not(bootstrap))]
     pub fn fmul_algebraic<T: Copy>(a: T, b: T) -> T;
 
     /// Float division that allows optimizations based on algebraic rules.
@@ -1943,7 +1934,6 @@ extern "rust-intrinsic" {
     /// This intrinsic does not have a stable counterpart.
     #[rustc_nounwind]
     #[rustc_safe_intrinsic]
-    #[cfg(not(bootstrap))]
     pub fn fdiv_algebraic<T: Copy>(a: T, b: T) -> T;
 
     /// Float remainder that allows optimizations based on algebraic rules.
@@ -1951,7 +1941,6 @@ extern "rust-intrinsic" {
     /// This intrinsic does not have a stable counterpart.
     #[rustc_nounwind]
     #[rustc_safe_intrinsic]
-    #[cfg(not(bootstrap))]
     pub fn frem_algebraic<T: Copy>(a: T, b: T) -> T;
 
     /// Convert with LLVM’s fptoui/fptosi, which may return undef for values out of range
@@ -2407,14 +2396,8 @@ extern "rust-intrinsic" {
     ///
     /// The stable version of this intrinsic is `std::panic::catch_unwind`.
     #[rustc_nounwind]
-    #[cfg(not(bootstrap))]
     pub fn catch_unwind(try_fn: fn(*mut u8), data: *mut u8, catch_fn: fn(*mut u8, *mut u8)) -> i32;
 
-    /// For bootstrap only, see `catch_unwind`.
-    #[rustc_nounwind]
-    #[cfg(bootstrap)]
-    pub fn r#try(try_fn: fn(*mut u8), data: *mut u8, catch_fn: fn(*mut u8, *mut u8)) -> i32;
-
     /// Emits a `!nontemporal` store according to LLVM (see their docs).
     /// Probably will never become stable.
     ///
@@ -2518,9 +2501,9 @@ extern "rust-intrinsic" {
     #[cfg(bootstrap)]
     pub fn vtable_align(ptr: *const ()) -> usize;
 
-    #[cfg(bootstrap)]
     #[rustc_const_unstable(feature = "const_eval_select", issue = "none")]
-    #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
+    #[rustc_safe_intrinsic]
+    #[cfg(bootstrap)]
     pub fn const_eval_select<ARG: Tuple, F, G, RET>(
         arg: ARG,
         called_in_const: F,
@@ -2650,8 +2633,7 @@ where
 #[rustc_const_unstable(feature = "is_val_statically_known", issue = "none")]
 #[rustc_nounwind]
 #[unstable(feature = "core_intrinsics", issue = "none")]
-#[cfg_attr(not(bootstrap), rustc_intrinsic)]
-#[cfg_attr(bootstrap, inline)]
+#[rustc_intrinsic]
 pub const fn is_val_statically_known<T: Copy>(_arg: T) -> bool {
     false
 }
@@ -2670,7 +2652,7 @@ pub const fn is_val_statically_known<T: Copy>(_arg: T) -> bool {
 #[rustc_const_unstable(feature = "ub_checks", issue = "none")]
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[inline(always)]
-#[cfg_attr(not(bootstrap), rustc_intrinsic)]
+#[rustc_intrinsic]
 pub(crate) const fn check_library_ub() -> bool {
     cfg!(debug_assertions)
 }
@@ -2686,7 +2668,7 @@ pub(crate) const fn check_library_ub() -> bool {
 #[rustc_const_unstable(feature = "ub_checks", issue = "none")]
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[inline(always)]
-#[cfg_attr(not(bootstrap), rustc_intrinsic)]
+#[rustc_intrinsic]
 pub(crate) const fn check_language_ub() -> bool {
     cfg!(debug_assertions)
 }
@@ -2702,8 +2684,7 @@ pub(crate) const fn check_language_ub() -> bool {
 #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[rustc_nounwind]
-#[cfg_attr(not(bootstrap), rustc_intrinsic)]
-#[cfg_attr(bootstrap, inline)]
+#[rustc_intrinsic]
 pub const unsafe fn const_allocate(_size: usize, _align: usize) -> *mut u8 {
     // const eval overrides this function, but runtime code should always just return null pointers.
     crate::ptr::null_mut()
@@ -2722,8 +2703,7 @@ pub const unsafe fn const_allocate(_size: usize, _align: usize) -> *mut u8 {
 #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[rustc_nounwind]
-#[cfg_attr(not(bootstrap), rustc_intrinsic)]
-#[cfg_attr(bootstrap, inline)]
+#[rustc_intrinsic]
 pub const unsafe fn const_deallocate(_ptr: *mut u8, _size: usize, _align: usize) {}
 
 /// `ptr` must point to a vtable.
@@ -2799,15 +2779,6 @@ pub unsafe fn vtable_align(_ptr: *const ()) -> usize {
 macro_rules! assert_unsafe_precondition {
     ($kind:ident, $message:expr, ($($name:ident:$ty:ty = $arg:expr),*$(,)?) => $e:expr $(,)?) => {
         {
-            // #[cfg(bootstrap)] (this comment)
-            // When the standard library is compiled with debug assertions, we want the check to inline for better performance.
-            // This is important when working on the compiler, which is compiled with debug assertions locally.
-            // When not compiled with debug assertions (so the precompiled std) we outline the check to minimize the compile
-            // time impact when debug assertions are disabled.
-            // The proper solution to this is the `#[rustc_no_mir_inline]` below, but we still want decent performance for cfg(bootstrap).
-            #[cfg_attr(all(debug_assertions, bootstrap), inline(always))]
-            #[cfg_attr(all(not(debug_assertions), bootstrap), inline(never))]
-
             // This check is inlineable, but not by the MIR inliner.
             // The reason for this is that the MIR inliner is in an exceptionally bad position
             // to think about whether or not to inline this. In MIR, this call is gated behind `debug_assertions`,
@@ -2816,8 +2787,8 @@ macro_rules! assert_unsafe_precondition {
             //
             // LLVM on the other hand sees the constant branch, so if it's `false`, it can immediately delete it without
             // inlining the check. If it's `true`, it can inline it and get significantly better performance.
-            #[cfg_attr(not(bootstrap), rustc_no_mir_inline)]
-            #[cfg_attr(not(bootstrap), inline)]
+            #[rustc_no_mir_inline]
+            #[inline]
             #[rustc_nounwind]
             #[rustc_const_unstable(feature = "ub_checks", issue = "none")]
             const fn precondition_check($($name:$ty),*) {
@@ -2885,13 +2856,7 @@ pub(crate) const fn is_nonoverlapping(
         true
     }
 
-    #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-    // SAFETY: This function's precondition is equivalent to that of `const_eval_select`.
-    // Programs which do not execute UB will only see this function return `true`, which makes the
-    // const and runtime implementation indistinguishable.
-    unsafe {
-        const_eval_select((src, dst, size, count), comptime, runtime)
-    }
+    const_eval_select((src, dst, size, count), comptime, runtime)
 }
 
 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
@@ -3208,9 +3173,5 @@ pub(crate) const fn miri_promise_symbolic_alignment(ptr: *const (), align: usize
 
     const fn compiletime(_ptr: *const (), _align: usize) {}
 
-    #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-    // SAFETY: the extra behavior at runtime is for UB checks only.
-    unsafe {
-        const_eval_select((ptr, align), compiletime, runtime);
-    }
+    const_eval_select((ptr, align), compiletime, runtime);
 }

library/core/src/intrinsics/simd.rs

@@ -2,11 +2,7 @@
 //!
 //! In this module, a "vector" is any `repr(simd)` type.
 
-// Temporary macro while we switch the ABI from "platform-intrinsics" to "intrinsics".
-#[rustfmt::skip]
-macro_rules! declare_intrinsics {
-($abi:tt) => {
-extern $abi {
+extern "rust-intrinsic" {
     /// Insert an element into a vector, returning the updated vector.
     ///
     /// `T` must be a vector with element type `U`.
@@ -659,10 +655,3 @@ extern $abi {
     #[rustc_nounwind]
     pub fn simd_flog<T>(a: T) -> T;
 }
-}
-}
-
-#[cfg(bootstrap)]
-declare_intrinsics!("platform-intrinsic");
-#[cfg(not(bootstrap))]
-declare_intrinsics!("rust-intrinsic");

library/core/src/lib.rs

@@ -112,6 +112,7 @@
 //
 // Library features:
 // tidy-alphabetical-start
+#![cfg_attr(bootstrap, feature(associated_type_bounds))]
 #![feature(array_ptr_get)]
 #![feature(char_indices_offset)]
 #![feature(const_align_of_val)]
@@ -203,12 +204,6 @@
 //
 // Language features:
 // tidy-alphabetical-start
-#![cfg_attr(bootstrap, feature(associated_type_bounds))]
-#![cfg_attr(bootstrap, feature(diagnostic_namespace))]
-#![cfg_attr(bootstrap, feature(exhaustive_patterns))]
-#![cfg_attr(bootstrap, feature(platform_intrinsics))]
-#![cfg_attr(not(bootstrap), feature(freeze_impls))]
-#![cfg_attr(not(bootstrap), feature(min_exhaustive_patterns))]
 #![feature(abi_unadjusted)]
 #![feature(adt_const_params)]
 #![feature(allow_internal_unsafe)]
@@ -233,6 +228,7 @@
 #![feature(doc_notable_trait)]
 #![feature(effects)]
 #![feature(extern_types)]
+#![feature(freeze_impls)]
 #![feature(fundamental)]
 #![feature(generic_arg_infer)]
 #![feature(if_let_guard)]
@@ -243,6 +239,7 @@
 #![feature(let_chains)]
 #![feature(link_llvm_intrinsics)]
 #![feature(macro_metavar_expr)]
+#![feature(min_exhaustive_patterns)]
 #![feature(min_specialization)]
 #![feature(multiple_supertrait_upcastable)]
 #![feature(must_not_suspend)]

library/core/src/mem/transmutability.rs

@@ -6,7 +6,7 @@ use crate::marker::ConstParamTy;
 /// any value of type `Self` are safely transmutable into a value of type `Dst`, in a given `Context`,
 /// notwithstanding whatever safety checks you have asked the compiler to [`Assume`] are satisfied.
 #[unstable(feature = "transmutability", issue = "99571")]
-#[cfg_attr(not(bootstrap), lang = "transmute_trait")]
+#[lang = "transmute_trait"]
 #[rustc_deny_explicit_impl(implement_via_object = false)]
 #[rustc_coinductive]
 pub unsafe trait BikeshedIntrinsicFrom<Src, const ASSUME: Assume = { Assume::NOTHING }>

library/core/src/num/f32.rs

@@ -1153,11 +1153,7 @@ impl f32 {
             // Stability concerns.
             unsafe { mem::transmute(x) }
         }
-        #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-        // SAFETY: We use internal implementations that either always work or fail at compile time.
-        unsafe {
-            intrinsics::const_eval_select((self,), ct_f32_to_u32, rt_f32_to_u32)
-        }
+        intrinsics::const_eval_select((self,), ct_f32_to_u32, rt_f32_to_u32)
     }
 
     /// Raw transmutation from `u32`.
@@ -1248,11 +1244,7 @@ impl f32 {
             // Stability concerns.
             unsafe { mem::transmute(x) }
         }
-        #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-        // SAFETY: We use internal implementations that either always work or fail at compile time.
-        unsafe {
-            intrinsics::const_eval_select((v,), ct_u32_to_f32, rt_u32_to_f32)
-        }
+        intrinsics::const_eval_select((v,), ct_u32_to_f32, rt_u32_to_f32)
     }
 
     /// Return the memory representation of this floating point number as a byte array in

library/core/src/num/f64.rs

@@ -1146,11 +1146,7 @@ impl f64 {
             // Stability concerns.
             unsafe { mem::transmute::<f64, u64>(rt) }
         }
-        #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-        // SAFETY: We use internal implementations that either always work or fail at compile time.
-        unsafe {
-            intrinsics::const_eval_select((self,), ct_f64_to_u64, rt_f64_to_u64)
-        }
+        intrinsics::const_eval_select((self,), ct_f64_to_u64, rt_f64_to_u64)
     }
 
     /// Raw transmutation from `u64`.
@@ -1246,11 +1242,7 @@ impl f64 {
             // Stability concerns.
             unsafe { mem::transmute::<u64, f64>(rt) }
         }
-        #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-        // SAFETY: We use internal implementations that either always work or fail at compile time.
-        unsafe {
-            intrinsics::const_eval_select((v,), ct_u64_to_f64, rt_u64_to_f64)
-        }
+        intrinsics::const_eval_select((v,), ct_u64_to_f64, rt_u64_to_f64)
     }
 
     /// Return the memory representation of this floating point number as a byte array in

library/core/src/ops/async_function.rs

@@ -132,7 +132,7 @@ mod internal_implementation_detail {
     /// and thus either `?0` or `i8`/`i16`/`i32` (see docs for `ClosureKind`
     /// for an explanation of that). The `GoalKind` is also the same type, but
     /// representing the kind of the trait that the closure is being called with.
-    #[cfg_attr(not(bootstrap), lang = "async_fn_kind_helper")]
+    #[lang = "async_fn_kind_helper"]
     trait AsyncFnKindHelper<GoalKind> {
         // Projects a set of closure inputs (arguments), a region, and a set of upvars
         // (by move and by ref) to the upvars that we expect the coroutine to have

library/core/src/panicking.rs

@@ -117,11 +117,7 @@ pub const fn panic_nounwind_fmt(fmt: fmt::Arguments<'_>, force_no_backtrace: boo
         panic_fmt(fmt);
     }
 
-    #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-    // SAFETY: const panic does not care about unwinding
-    unsafe {
-        super::intrinsics::const_eval_select((fmt, force_no_backtrace), comptime, runtime);
-    }
+    super::intrinsics::const_eval_select((fmt, force_no_backtrace), comptime, runtime);
 }
 
 // Next we define a bunch of higher-level wrappers that all bottom out in the two core functions

library/core/src/ptr/const_ptr.rs

@@ -48,12 +48,8 @@ impl<T: ?Sized> *const T {
             }
         }
 
-        // on bootstrap bump, remove unsafe block
-        #[cfg_attr(not(bootstrap), allow(unused_unsafe))]
-        // SAFETY: The two versions are equivalent at runtime.
-        unsafe {
-            const_eval_select((self as *const u8,), const_impl, runtime_impl)
-        }
+        #[allow(unused_unsafe)]
+        const_eval_select((self as *const u8,), const_impl, runtime_impl)
     }
 
     /// Casts to a pointer of another type.
@@ -818,13 +814,8 @@ impl<T: ?Sized> *const T {
                 true
             }
 
-            #[cfg_attr(not(bootstrap), allow(unused_unsafe))]
-            // on bootstrap bump, remove unsafe block
-            // SAFETY: This function is only used to provide the same check that the const eval
-            // interpreter does at runtime.
-            unsafe {
-                intrinsics::const_eval_select((this, origin), comptime, runtime)
-            }
+            #[allow(unused_unsafe)]
+            intrinsics::const_eval_select((this, origin), comptime, runtime)
         }
 
         assert_unsafe_precondition!(
@@ -1648,11 +1639,7 @@ impl<T: ?Sized> *const T {
         // The cast to `()` is used to
         //   1. deal with fat pointers; and
         //   2. ensure that `align_offset` (in `const_impl`) doesn't actually try to compute an offset.
-        #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-        // SAFETY: The two versions are equivalent at runtime.
-        unsafe {
-            const_eval_select((self.cast::<()>(), align), const_impl, runtime_impl)
-        }
+        const_eval_select((self.cast::<()>(), align), const_impl, runtime_impl)
     }
 }
 

library/core/src/ptr/mut_ptr.rs

@@ -48,11 +48,7 @@ impl<T: ?Sized> *mut T {
             }
         }
 
-        #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-        // SAFETY: The two versions are equivalent at runtime.
-        unsafe {
-            const_eval_select((self as *mut u8,), const_impl, runtime_impl)
-        }
+        const_eval_select((self as *mut u8,), const_impl, runtime_impl)
     }
 
     /// Casts to a pointer of another type.
@@ -1906,11 +1902,7 @@ impl<T: ?Sized> *mut T {
         // The cast to `()` is used to
         //   1. deal with fat pointers; and
         //   2. ensure that `align_offset` (in `const_impl`) doesn't actually try to compute an offset.
-        #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-        // SAFETY: The two versions are equivalent at runtime.
-        unsafe {
-            const_eval_select((self.cast::<()>(), align), const_impl, runtime_impl)
-        }
+        const_eval_select((self.cast::<()>(), align), const_impl, runtime_impl)
     }
 }
 

library/core/src/slice/index.rs

@@ -35,15 +35,7 @@ where
 #[track_caller]
 #[rustc_const_unstable(feature = "const_slice_index", issue = "none")]
 const fn slice_start_index_len_fail(index: usize, len: usize) -> ! {
-    #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-    // SAFETY: we are just panicking here
-    unsafe {
-        const_eval_select(
-            (index, len),
-            slice_start_index_len_fail_ct,
-            slice_start_index_len_fail_rt,
-        )
-    }
+    const_eval_select((index, len), slice_start_index_len_fail_ct, slice_start_index_len_fail_rt)
 }
 
 // FIXME const-hack
@@ -64,11 +56,7 @@ const fn slice_start_index_len_fail_ct(_: usize, _: usize) -> ! {
 #[track_caller]
 #[rustc_const_unstable(feature = "const_slice_index", issue = "none")]
 const fn slice_end_index_len_fail(index: usize, len: usize) -> ! {
-    #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-    // SAFETY: we are just panicking here
-    unsafe {
-        const_eval_select((index, len), slice_end_index_len_fail_ct, slice_end_index_len_fail_rt)
-    }
+    const_eval_select((index, len), slice_end_index_len_fail_ct, slice_end_index_len_fail_rt)
 }
 
 // FIXME const-hack
@@ -89,11 +77,7 @@ const fn slice_end_index_len_fail_ct(_: usize, _: usize) -> ! {
 #[track_caller]
 #[rustc_const_unstable(feature = "const_slice_index", issue = "none")]
 const fn slice_index_order_fail(index: usize, end: usize) -> ! {
-    #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-    // SAFETY: we are just panicking here
-    unsafe {
-        const_eval_select((index, end), slice_index_order_fail_ct, slice_index_order_fail_rt)
-    }
+    const_eval_select((index, end), slice_index_order_fail_ct, slice_index_order_fail_rt)
 }
 
 // FIXME const-hack

library/core/src/str/mod.rs

@@ -86,15 +86,7 @@ use iter::{MatchesInternal, SplitNInternal};
 #[rustc_allow_const_fn_unstable(const_eval_select)]
 #[cfg(not(feature = "panic_immediate_abort"))]
 const fn slice_error_fail(s: &str, begin: usize, end: usize) -> ! {
-    #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
-    // SAFETY: panics for both branches
-    unsafe {
-        crate::intrinsics::const_eval_select(
-            (s, begin, end),
-            slice_error_fail_ct,
-            slice_error_fail_rt,
-        )
-    }
+    crate::intrinsics::const_eval_select((s, begin, end), slice_error_fail_ct, slice_error_fail_rt)
 }
 
 #[cfg(feature = "panic_immediate_abort")]