| # Proxy Bit-References | |
| Rust does not permit the use of custom proxy structures in place of true | |
| reference primitives, so APIs that specify references (like `IndexMut` or | |
| `DerefMut`) cannot be implemented by types that cannot manifest `&mut` | |
| references directly. Since `bitvec` cannot produce an `&mut bool` reference | |
| within a `BitSlice`, it instead uses the `BitRef` proxy type defined in this | |
| module to provide reference-like work generally, and simply does not define | |
| `IndexMut<usize>`. |