Fix miri errors.

Author: reitermarkus

src/vec/drain.rs

@@ -104,8 +104,8 @@ impl<T, const N: usize> Drop for Drain<'_, T, N> {
                         let start = source_vec.len();
                         let tail = self.0.tail_start;
                         if tail != start {
-                            let src = source_vec.as_ptr().add(tail);
                             let dst = source_vec.as_mut_ptr().add(start);
+                            let src = source_vec.as_ptr().add(tail);
                             ptr::copy(src, dst, self.0.tail_len);
                         }
                         source_vec.set_len(start + self.0.tail_len);

src/vec/mod.rs

@@ -345,12 +345,13 @@ impl<T, const N: usize> Vec<T, N> {
         unsafe {
             // Set `self.vec` length's to `start`, to be safe in case `Drain` is leaked.
             self.set_len(start);
-            let range_slice = slice::from_raw_parts(self.as_ptr().add(start), end - start);
+            let vec = NonNull::from(self);
+            let range_slice = slice::from_raw_parts(vec.as_ref().as_ptr().add(start), end - start);
             Drain {
                 tail_start: end,
                 tail_len: len - end,
                 iter: range_slice.iter(),
-                vec: NonNull::from(self),
+                vec,
             }
         }
     }