auto_from

This library exports a derive macro for From. It is used to automatically generate std::convert::From implementations for enum variants containing only one field. It currently works for tuple or struct variants. Here is a small example:

use auto_from::From;

#[auto_from]
#[derive(Debug, PartialEq, From)]
enum Foo {
    Int(i32),
    Long { value: i64 },
}

fn main() {
    assert_eq!(Foo::Int(24), Foo::from(24i32));
    assert_eq!(Foo::Long{ value: 24 }, Foo::from(24i64));
}

This should be most useful when constructing error enums that require writing many From implementations, or using many .map_error(|e| MyError::Variant(e)) calls across the code. This crate just simplifies the process.