The nightly version of the docs properly document that method, including an example: https://doc.rust-lang.org/nightly/std/cell/struct.RefMut.html#method.map_s

The nightly version of the docs properly document that method, including an example: https://doc.rust-lang.org/nightly/std/cell/struct.RefMut.html#method.map_split https://doc.rust-lang.org/nightly/std/cell/struct.RefMut.htm...