Backport the reimplementation of transmute

src/lib.rs

@@ -53,7 +53,6 @@ use core::{mem, ptr, slice};
 
 use core::marker::PhantomData;
 use core::mem::ManuallyDrop;
-pub use core::mem::transmute;
 use core::ops::{Deref, DerefMut};
 
 use typenum::bit::{B0, B1};
@@ -435,6 +434,16 @@ where
     }
 }
 
+/// A reimplementation of the `transmute` function, avoiding problems
+/// when the compiler can't prove equal sizes.
+#[inline]
+#[doc(hidden)]
+pub unsafe fn transmute<A, B>(a: A) -> B {
+    let b = ::core::ptr::read(&a as *const A as *const B);
+    ::core::mem::forget(a);
+    b
+}
+
 #[cfg(test)]
 mod test {
     // Compile with: