Fix unsizes on mutations

[W95Psp]

Fixes #256: copy_from_slice (and any other functions with &mut inputs actually) on sized things (e.g. fixed size arrays [T; N])

This is related to thin / fat pointers.

cc @karthikbhargavan @xvzcf @geonnave

[franziskuskiefer]

Thanks. Two comments.

I noticed that running tests fails because of js_of_ocaml. This is unrelated to this PR (probably introduced in #265), but something we need to get fixed. Manually installing it fixes the issue

File "bin/dune", line 27, characters 28-39:
27 |  (libraries zarith_stubs_js js_of_ocaml lib))
                                 ^^^^^^^^^^^
Error: Library "js_of_ocaml" not found.

[W95Psp]

I fixed the field bug, and added the example you suggested @franziskuskiefer :)

[franziskuskiefer]

I fixed the field bug, and added the example you suggested @franziskuskiefer :)

And you force pushed ... So this will have to wait until tomorrow I'm afraid because I have to start the review from scratch

[W95Psp]

Sorry... I'm so used to running git rebase main, but after doing it that's a pain to revert :(

[franziskuskiefer]

Thanks

[franziskuskiefer]

CI is failing