| Returns `None` if the pointer is null, or else returns a shared reference to |
| the value wrapped in `Some`. If the value may be uninitialized, [`as_uninit_ref`] |
| must be used instead. |
| |
| # Safety |
| |
| When calling this method, you have to ensure that *either* the pointer is null *or* |
| the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion). |
| |
| # Panics during const evaluation |
| |
| This method will panic during const evaluation if the pointer cannot be |
| determined to be null or not. See [`is_null`] for more information. |
| |
| # Null-unchecked version |
| |
| If you are sure the pointer can never be null and are looking for some kind of |
| `as_ref_unchecked` that returns the `&T` instead of `Option<&T>`, know that you can |
| dereference the pointer directly. |
