Rollup merge of rust-lang#120809 - reitermarkus:generic-nonzero-const…

…ructors, r=Nilstrieb

Use `transmute_unchecked` in `NonZero::new`.

Tracking issue: rust-lang#120257

See rust-lang#120521 (comment).

library/core/src/num/nonzero.rs

@@ -8,7 +8,6 @@ use crate::intrinsics;
 use crate::marker::StructuralEq;
 use crate::marker::StructuralPartialEq;
 use crate::ops::{BitOr, BitOrAssign, Div, Neg, Rem};
-use crate::ptr;
 use crate::str::FromStr;
 
 use super::from_str_radix;
@@ -91,13 +90,12 @@ where
     /// Creates a non-zero if the given value is not zero.
     #[stable(feature = "nonzero", since = "1.28.0")]
     #[rustc_const_stable(feature = "const_nonzero_int_methods", since = "1.47.0")]
-    #[rustc_allow_const_fn_unstable(const_refs_to_cell)]
     #[must_use]
     #[inline]
     pub const fn new(n: T) -> Option<Self> {
         // SAFETY: Memory layout optimization guarantees that `Option<NonZero<T>>` has
         //         the same layout and size as `T`, with `0` representing `None`.
-        unsafe { ptr::read(ptr::addr_of!(n).cast()) }
+        unsafe { intrinsics::transmute_unchecked(n) }
     }
 
     /// Creates a non-zero without checking whether the value is non-zero.