Function replace_with::replace_with_or_default_and_return

pub fn replace_with_or_default_and_return<T: Default, U, F: FnOnce(T) -> (U, T)>(
    dest: &mut T, 
    f: F
) -> U

Temporarily takes ownership of a value at a mutable location, and replace it with a new value based on the old one. Replaces with Default::default() on panic. Lets the closure return a custom value as well.

We move out of the reference temporarily, to apply a closure f, returning a new value, which is then placed at the original value's location.

This is effectively the same function as replace_with_or_default, but it lets the closure return a custom value as well.

An important note

On panic (or to be more precise, unwinding) of the closure f, T::default() will be called to provide a replacement value. T::default() should not panic – doing so will constitute a double panic and will most likely abort the process.

Equivalent to replace_with_and_return(dest, T::default, f).

Example

fn take<T>(option: &mut Option<T>) -> Option<T> {
    replace_with_or_default_and_return(option, |option| (option, None))
}