num_convert 0.7.2

Type converting library, conversions integers by overflow addition, supports generics types.
Documentation 
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/// A generic trait for converting into possible types with different signs.
///
/// # Usage
/// Basic use of the trait.
///
/// ```
/// use num_convert::IntoByAdd;
///
/// assert_eq!(IntoByAdd::<u64>::into_by_add(i8::MAX), u8::MAX as u64);
/// assert_eq!(<i16 as IntoByAdd<u16>>::into_by_add(i16::MIN), u16::MIN);
/// ```
///
/// # Examples
///
/// ```
/// # use num_convert::IntoByAdd;
/// fn convert_into_u8<T: IntoByAdd<u8>>(min: T, max: T) -> (u8, u8) {
///     (min.into_by_add(), max.into_by_add())
/// }
///
/// assert_eq!(convert_into_u8(i8::MIN, i8::MAX), (u8::MIN, u8::MAX));
/// assert_eq!(<i32 as IntoByAdd<u128>>::into_by_add(i32::MIN), u32::MIN as u128);
/// ```
pub trait IntoByAdd<T> {
    /// Converts the value of `self` to an `T`.
    fn into_by_add(self) -> T;
}

macro_rules! signed_or_unsigned_impls {
    ( $( $for_type:ty; $($into_type:ty),* );* ) => {
        $(
            //signed = to signed
            //unsigned = to unsigned
            impl IntoByAdd<$for_type> for $for_type {
                #[doc = concat!("Returns the same type ", stringify!($for_type), ".")]
                #[inline]
                fn into_by_add(self) -> $for_type {
                    self
                }
            }

            $(
                //signed < to signed
                //unsigned < to unsigned
                impl IntoByAdd<$into_type> for $for_type {
                    #[doc = concat!("Converts ", stringify!($for_type), " to ", stringify!($into_type), " losslessly.")]
                    #[inline]
                    fn into_by_add(self) -> $into_type {
                        self as $into_type
                    }
                }
            )*
        )*
    }
}

macro_rules! unsigned_to_signed_impls {
    ( $( $for_type:ty, $as_type:ty; $($into_type:ty),* );* ) => {
        $(
            //unsigned = to signed
            impl IntoByAdd<$as_type> for $for_type {
                #[doc = concat!("Converts ", stringify!($for_type), " to equvalent ", stringify!($as_type), ".")]
                #[inline]
                fn into_by_add(self) -> $as_type {
                    ((self as $as_type).wrapping_add(<$as_type>::MAX)).wrapping_add(1)
                }
            }

            $(
                //unsigned < to signed
                impl IntoByAdd<$into_type> for $for_type {
                    #[doc = concat!("Converts ", stringify!($for_type), " to equvalent ", stringify!($into_type), ".")]
                    #[inline]
                    fn into_by_add(self) -> $into_type {
                        ((self as $as_type).wrapping_add(<$as_type>::MAX)).wrapping_add(1) as $into_type
                    }
                }
            )*
        )*
    };
}

macro_rules! signed_to_unsigned_impls {
    //signed < to unsigned
    ( $for_type:ty; $add_value:expr; $($into_type:ty),*) => {
        $(
            impl IntoByAdd<$into_type> for $for_type {
                #[doc = concat!("Converts ", stringify!($for_type), " to equvalent ", stringify!($into_type), ".")]
                #[inline]
                fn into_by_add(self) -> $into_type {
                    (self as $into_type).wrapping_add($add_value)
                }
            }
        )*
    };
}

signed_or_unsigned_impls! { i8; i16, i32, i64, isize, i128; i16; i32, i64, isize, i128 }
signed_or_unsigned_impls! { i32; i64, isize, i128; i64; isize, i128; isize; i64, i128; i128; }
signed_or_unsigned_impls! { u8; u16, u32, u64, usize, u128; u16; u32, u64, usize, u128 }
signed_or_unsigned_impls! { u32; u64, usize, u128; u64; usize, u128; usize; u64, u128; u128; }

signed_to_unsigned_impls! { i8; 128; u8, u16, u32, u64, usize, u128 }
signed_to_unsigned_impls! { i16; 32_768; u16, u32, u64, usize, u128 }
signed_to_unsigned_impls! { i32; 2_147_483_648; u32, u64, usize, u128 }
signed_to_unsigned_impls! { i64; 9_223_372_036_854_775_808; u64, usize, u128 }
signed_to_unsigned_impls! { isize; 9_223_372_036_854_775_808; u64, usize, u128 }
signed_to_unsigned_impls! { i128; 170_141_183_460_469_231_731_687_303_715_884_105_728; u128 }

unsigned_to_signed_impls! { u8, i8; i16, i32, i64, isize, i128; u16, i16; i32, i64, isize, i128 }
unsigned_to_signed_impls! { u32, i32; i64, isize, i128; u64, i64; isize, i128; usize, isize; i64, i128; u128, i128; }