#borrow #unsafe #mutable

borrowck_sacrifices

Necessary sacrifices to keep the Borrow Checker happy and developers sane

1 unstable release

0.1.0 Aug 7, 2023

#2457 in Rust patterns

MIT license

9KB
107 lines

Borrowck Scarifices

Keeps the borrow checker happy by combination of safe and unsafe sacrifices. This crate mostly deals with limitations of the borrow checker and is not supposed to be used to create segfaults.

Access to "the rest of the elements" while iterating over a slice

Splittable trait is provided to facilitate a common pattern of modifying a container element while iterating over all other elements of the same container, as in the pseudo-example below:

    let mut x = [1,2,3];        
        let hero = &mut x[1];
        for (i,elem) in x.iter_mut().enumerate()
        {
            if i == 1 {continue}
            if elem > hero{
                *hero = 0;
            }
            else{
                *elem = 0;
            }
        }

A Splittable trait allows for stuff similar to split_at_mut() but better suited to facilitate this usecase.

Lifetime extension

When making mutable iterators there is a common trick that is often needed to make borrowck admit that giving a mutable reference to an element in next() is indeed safe. The lifetime_detach() allows for the user to do the usual "extend the lifetime" ritual, all in a nice generic package. This also makes it easier to make mutable and immutable iterators in one swoop using duplicate! macro.

Stability, contributions

PR's are welcome, but keep the scope to things related to borrow checking tricks, rather than "anything related to memory".

Other similar things you may want to do

Also check these crates for more of similar features:

No runtime deps