What's your motivation for this pull request? This currently raises the MSRV quite substantially, so it should have a good motivation, at the very least.

I made this crate, and doing that was my motivation.

The summary is: now that &mut is const-compatible, you can make almost everything in ArrayVec into a const fn. Having a mut ArrayVec at compile-time is extremely powerful.

For now I've just forked this crate as arrayvec-const, but that's basically just a hack.

Do you think this would be better served via a feature-flag?

I would love if we could have something like this 👍 , honestly sooner rather than later as it blocks downstream libraries.

1.83 marks a huge shift in whats possible in const and anybody trying to currently use arrayvec
in programs that want to take advantage of that is just completely out of luck.

A minimal version of this that would be sufficient for libraries would be a const_as_mut_ptr feature flag that would opt in to 1.83. It would mark the following two functions as const (both of these are one liners so having a cfg'd duplicate should be acceptible):

• as_mut_ptr
• set_len
  This would expose enough of ArrayVecs internals for a downstream library / program willing to use unsafe to do what it needs to in const code.

I've created #296 as an alternative to this with the changes under the feature flag const.

Instead of cfg duplicating the code, I just cfg duplicated a macro that basically just adds or removes const based on the flag.