Use cast instead of transmute

[kornelski]

NonNull supports cast(), so there's no need for transmute.

[Voultapher]

Thanks for the PR. I'm fine with the change, that said I'd like to understand the motivation for the change a bit better. For example one thing I like about transmute is you immediately see and enforce the type you cast from and to, and if you change something you have to go through each relevant transmute and update them, re-evaluating if they are still valid. With cast that would not be a compile time error right?

[Voultapher]

Please specify the cast result type here.

[Voultapher]

Completely unrelated, I just realized you are the creator of gifski a project I've used quite a bit, thank you for the great project <3

[kornelski]

The idea behind this is that transmute is a more powerful, more general-purpose function, and it has power of transmuting types that aren't compatible.

cast() is more specific and directly expresses what is happening, and is implemented only on pointer types.

In your case I think all transmutes are correct. However in general there are cases where transmute of exotically sized pointers is not well-defined (they don't have guaranteed layouts), but cast (which can change pointer layout) is allowed.

[Voultapher]

Sounds good. I'm looking into the miri failure that seems unrelated to this change. Please update the PR to be compatible with rustc 1.36 as tested by old_rust_rustc_1_36.

[Voultapher]

You should be able to rebase on main now and the miri test should run as expected.

[Voultapher]

The CI for this project is a bit dated, and the triggers were wonky. I took the liberty of fixing it on main and rebasing your branch. Change looks good otherwise.

[Voultapher]

ptr: self.joined_ptr.as_ptr().cast::<u8>() requires ptr_cast feature which is not available for rustc 1.36. The machinery for polyfilling it only for old rustc versions and if the users opt into the old_rustc feature is there, but I wonder if it is overkill. Thoughts?

[kornelski]

Sure, I've replaced that with a regular pointer cast.

BTW, I expect 1.36, and all rust versions below 1.56, to be completely dead and unusable: https://lib.rs/stats#rustc

[Voultapher]

I'd be careful about such assumptions, also I have an upstream dependency that specifically asked for this feature #30. As long as it seems reasonably possible to keep the minimum required rustc version the same, I plan on doing so.

[Voultapher]

I've merged the change, thanks for the PR. I'm not sure if this change has any immediate impact on users, do you think a new release is required?

[kornelski]

Thanks. No need to rush with a release.