quick_from

A derive macro for quickly implementing From on on enum variants that wrap other types.

Example

```rust

[macro_use]

extern crate quick_from;

use std::{io, fs};

[derive(QuickFrom)]

enum Error { InvalidInput,

#[quick_from]
Io(io::Error),

}

fn my_read(s : &str) -> Result, Error> { if s.len() == 0 { return Err(Error::InvalidInput) }

Ok(fs::read(s)?)

} ```