Make use of core::hint::unreachable_unchecked

Author: c410-f3r

src/macros.rs

@@ -6,7 +6,7 @@ macro_rules! debug_unreachable {
     };
     ($e:expr) => {
         if cfg!(not(debug_assertions)) {
-            crate::utils::unreachable();
+            core::hint::unreachable_unchecked();
         } else {
             panic!($e);
         }

src/small_vec.rs

@@ -2,7 +2,7 @@
 use crate::small_vec_visitor::SmallVecVisitor;
 #[cfg(feature = "specialization")]
 use crate::spec_from::SpecFrom;
-use crate::utils::{deallocate, unreachable};
+use crate::utils::deallocate;
 #[cfg(not(feature = "const_generics"))]
 use crate::Array;
 use crate::{
@@ -13,6 +13,7 @@ use core::{
     cmp::{Eq, Ord, Ordering, PartialOrd},
     fmt::{self, Debug},
     hash::{Hash, Hasher},
+    hint::unreachable_unchecked,
     iter::{repeat, FromIterator},
     mem::{self, MaybeUninit},
     ops::{Deref, DerefMut, Index, IndexMut, Range, RangeFrom, RangeFull, RangeTo},
@@ -435,7 +436,7 @@ impl<A: Array> SmallVec<A> {
     pub fn swap_remove(&mut self, index: usize) -> A::Item {
         let len = self.len();
         self.swap(len - 1, index);
-        self.pop().unwrap_or_else(|| unsafe { unreachable() })
+        self.pop().unwrap_or_else(|| unsafe { unreachable_unchecked() })
     }
 
     /// Remove all elements from the vector.

src/utils.rs

@@ -1,17 +1,4 @@
-use core::mem;
-
 pub unsafe fn deallocate<T>(ptr: *mut T, capacity: usize) {
     let _vec: Vec<T> = Vec::from_raw_parts(ptr, 0, capacity);
     // Let it drop.
-}
-
-/// Hint to the optimizer that any code path which calls this function is
-/// statically unreachable and can be removed.
-///
-/// Equivalent to `std::hint::unreachable_unchecked` but works in older versions of Rust.
-#[inline]
-pub unsafe fn unreachable() -> ! {
-    enum Void {}
-    let x: &Void = mem::transmute(1usize);
-    match *x {}
-}
+}