Comparison to other "safe transmute" crates

[8573]

In the spirit of

• does this replace quickcheck completely? proptest-rs/proptest#15 (comment),
• Comparison to Nom Marwes/combine#73, and
• Add comparison/migration guide to failure shepmaster/snafu#50,

I suggest documenting how this crate compares with some other crates that offer "safe transmute" functions, especially for transmuting a type to itself, such as

• https://github.com/Centril/refl
• https://github.com/pthariensflame/identity.rs
• https://github.com/nabijaczleweli/safe-transmute-rs

[GoldsteinE]

Thanks for suggestion!

It looks like first two require to statically provide an equality proof, which could be impossible in some contexts — for example, when implementing a generic method of a foreign trait and arguably worse for usability: if you want to compare a type against several other types, you’ll need to carry an enum of Refls and match on it dynamically, which is not zero-cost.

I think the third one doesn’t provide equivalent functionality at all, but I’ll have to look further into it.

[GoldsteinE]

I’ll describe this in README a little bit later.

[zicklag]

Another crate we might want to compare with is castaway which seems by far the most similar so far, but also seems to lack the functionality of cismute::reference.

[GoldsteinE]

It can cast simple references, but it seems to not be extendable. Also it uses macros instead of functions, so reqiured bounds are explained in text, not in types. It also lacks switch.

Thanks, I’ll add this to the comparison.

[zicklag]

Ah. I ended up using your crate instead of it because I didn't want to have to implement LifetimeFree, especially because I had to implement it on a foreign container type, which meant I'd have to use a newtype, which would just end up with way more boilerplate.

I think I have a real-world use-case for your crate, so thanks a lot for this!