newtype-tools 1.0.13

A lightweight library designed to make the newtype idiom more ergonomic to use.
Documentation 
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#![cfg(feature = "derive")]

#[test]
fn from() {
    #[derive(newtype_tools::Newtype)]
    /// Doc comment.
    #[newtype(
        // From oranges.
        from("Oranges", with = "|oranges| Apples(oranges.0 as u64 * 2)"),
        // From oranges reference.
        from(&Oranges, with = |oranges| Apples(oranges.0 as u64 * 2)),
        // Into oranges.
        into(Oranges, with = |apples| Oranges((apples.0 / 2) as u32)),
    )]
    #[repr(transparent)]
    struct Apples(u64);
    struct Oranges(u32);

    let apples = Apples(42);
    assert_eq!(apples.0, 42);

    let oranges = Oranges::from(apples);
    assert_eq!(oranges.0, 21);
}

#[test]
fn generic_from() {
    #[derive(newtype_tools::Newtype)]
    #[newtype(from(Oranges, with = |oranges| Apples(T::from(oranges.0 * 2))))]
    #[repr(transparent)]
    struct Apples<T>(T)
    where
        T: From<u32>;
    struct Oranges(u32);

    let apples = Apples(42_u64);
    assert_eq!(apples.0, 42);
}

#[test]
fn try_from() {
    use core::num::TryFromIntError;
    #[derive(newtype_tools::Newtype)]
    #[newtype(try_from(
        u64,
        error = "TryFromIntError",
        with = "|v| u32::try_from(v).map(Oranges)"
    ))]
    #[repr(transparent)]
    struct Oranges(u32);

    let oranges = Oranges::try_from(42_u64).unwrap();
    assert_eq!(oranges.0, 42);
}

#[test]
fn generic_try_from() {
    use core::num::TryFromIntError;
    #[derive(newtype_tools::Newtype)]
    #[newtype(try_from(
        Oranges,
        error = TryFromIntError,
        with = |a| T::try_from(a.0).map(Apples)
    ))]
    #[repr(transparent)]
    struct Apples<T>(T)
    where
        T: TryFrom<u64, Error = TryFromIntError>;
    struct Oranges(u64);

    let apples = Apples::<u32>::try_from(Oranges(42)).unwrap();
    assert_eq!(apples.0, 42);
}