Macro impl_from 

macro_rules! impl_from {
    (<$($generic:ident),+> in $($rest:tt)+) => { ... };
    (<const $($rest:tt)+) => { ... };
    (<$generic:ident, $($rest:tt)+) => { ... };
    (@impl [$($generic:tt)+] $from:ty => $this:ty $(,)?) => { ... };
    (@impl [$($generic:tt)+] $from:ty => $this:ty : $field:ident $(,)?) => { ... };
    ($from:ty => $this:ty $(,)?) => { ... };
    ($from:ty => $this:ty : $field:ident $(,)?) => { ... };
}

Implement From for a struct.

Declare type and const parameters before in.

Examples

With a newtype struct:

use impl_more::impl_from;

struct Foo(String);
impl_from!(String => Foo);

let foo = Foo::from("bar".to_owned());

With a named field struct with type parameters:

use std::rc::Rc;
use impl_more::impl_from;

struct Foo<T> { inner: Rc<T> }
impl_from!(<T> in Rc<T> => Foo<T> : inner);

let foo = Foo::from(Rc::new("bar".to_owned()));

With type and const parameters:

struct Array<T, const N: usize>([T; N]);
impl_more::impl_from!(<T, const N: usize> in [T; N] => Array<T, N>);

let value = Array::from([1, 2, 3]);
assert_eq!(value.0, [1, 2, 3]);