Convi - convenient (but safe) conversion (From-like) traits for Rust

Tired of the pain of casting usize in Rust? This crate is here to help.

First, by enabling cargo features on this crate like this:

convi = { version = "*", features = [ "min_target_ptr_width_32"] }

you can mark your code as not compatible with architectures with pointer size less than 32 bits. This will enable conversions like:

``` use convi::CastFrom;

fn main() { let someu32 = 3u32; println!("{}", usize::castfrom(some_u32); } ```

and display appropriate error message if anyone tries to build your code for unsupported architecture.

In addition, for times where you know that your value will always be smaller than the given type, instead of u32::try_from(some_usize).expect("must not fail"), you can:

``` use convi::CheckedFrom;

fn main() { let someu32 = 3u32; println!("{}", usize::checkedfrom(some_u32); } ```

Zero dependencies, small code, review it yourself.