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//! # Welcome, fellow programmer! 👋🏼
//!
//! The newtype macro is very simple:
//!
//! ```rust
//! # #[macro_use] extern crate new_type;
//! # fn main() {
//! newtype!(Meters, Centimeters);
//!
//! let distance_one = Meters(10);
//! let distance_two = Meters(5);
//! let distance_three = Centimeters(5);
//!
//! // Successfully add the same type.
//! assert_eq!(distance_one + distance_two, Meters(15))
//!
//! // Compilation error: expected struct `Meters`, found struct `Centimeters`
//! // assert_eq!(distance_one + distance_three, Meters(15))
//! # }
//! ```
//!
//! # Under the hood ⚙️
//!
//! The newtype is implemented with a generic type parameter.
//! Via this type parameter it does kind of a "type level derive" i.e. it implements operations by deferring to the implementation of the underlying type.
//! That works across any level of nested newtypes, if that should be of any use.
//! For details read on in [newtype].
//!
//! # Footgun Warning ⚠️
//!
//! It is highly recommended to explicitly pass the expexted types into the tuple constructor as by default any type goes due to the generic type parameter.
//! This is definetly a footgun but as the generic type parameter is core to how this crate operates not obviously avoidable. Open a PR is you have ideas.
//!
//! ```rust
//! # #[macro_use] extern crate new_type;
//! # fn main() {
//! // We specify a default type.
//! // The default type is only relevant for calls to T::default() and only if there is no reason for the compiler to infer another type.
//! newtype!(Meters: f32);
//!
//! // Footgun right here, we pass an integer, so it will be an i32.
//! let distance_one = Meters(10);
//!
//! // Footgun possible here, we pass a float, so it would be a f64 by default.
//! // Because we add it with an explicit f32 type the compiler can infer it needs to be an f32 as well.
//! let distance_two = Meters(5.0);
//!
//! // The recommended way to construct values of the newtype.
//! let distance_three = Meters(5.0_f32);
//!
//! assert_eq!(distance_two + distance_three, Meters(10.0));
//!
//! // Compilation error: expected integer, found floating-point number
//! // assert_eq!(distance_one + distance_two, Meters(15))
//!
//! // Footgun here, f64 is infered for the call to T::default() despite f32 being the default type parameter.
//! assert_eq!(Meters::default(), Meters(0.0_f64));
//! # }
//! ```
/// Implements its arguments as newtypes.
///
/// The macro is meant to provide easy means to enhance the semantics of language built-ins.
///
/// Newtypes come with `Deref`, `DerefMut`, `AsRef`, `AsMut`, and `From` traits.
/// Further they implement almost all std::ops and std::cmp of the type they wrap if the operants have value semantics and return `Self`.
/// Exceptions are std::ops::{`Drop`, `Fn`, `FnMut`, `FnOnce`, `Index`, `IndexMut`, `RangeBounds`}.
///
/// Usually one obtains instances of the newtype by the public constructor but `Default` is available if the wrapped type implements it.
/// It is not as ergonomic as it should be though, see examples below.
///
/// # Examples
///
/// Operations are available on newtypes:
/// ```rust
/// # #[macro_use] extern crate new_type;
/// # fn main() {
/// newtype!(Count);
/// let count_one = Count(100);
/// let count_two = Count(50);
/// // We can add 'Count' because we can add i32!
/// assert_eq!(count_one + count_two, Count(150))
/// # }
/// ```
/// Newtypes can be simple function arguments with default types:
/// ```rust
/// # #[macro_use] extern crate new_type;
/// # fn main() {
/// // We specify default type here!
/// newtype!(Count: usize);
///
/// fn add_count(a: Count, b: Count) -> Count {
/// a + b
/// }
///
/// // We can add 'Count' because we can add usize!
/// assert_eq!(add_count(Count(100), Count(50)), Count(150))
/// # }
/// ```
/// Functions and defaults are available on newtypes:
/// ```rust
/// # #[macro_use] extern crate new_type;
/// # use std::collections::HashSet;
/// # fn main() {
/// newtype!(Humans: HashSet<&'static str>);
/// // Sadly we need to specify `Humans` as type in order to get access to `Default`.
/// let mut some_humans: Humans = Humans::default();
/// some_humans.insert("Maria");
/// some_humans.insert("Peter");
/// let mut other_humans: Humans = Humans::default();
/// other_humans.insert("Kim");
/// other_humans.insert("Mia");
/// // We can extend Humans with Humans!
/// some_humans.extend(other_humans.iter());
/// // We can ask for '.len()' on Humans because we can ask for '.len()' on HashSet!
/// assert_eq!(some_humans.len(), 4)
/// # }
/// ```
/// Newtypes can be nested:
/// ```rust
/// # #[macro_use] extern crate new_type;
/// # fn main() {
/// newtype!(A, B, C);
/// let abc_one = A(B(C(5)));
/// let abc_two = A(B(C(5)));
/// // We can add nested newtypes because we can add the wrapped type!
/// assert_eq!(abc_one + abc_two, A(B(C(10))))
/// # }
/// ```
#[macro_export]
macro_rules! newtype {
( $( $newtype:ident $( : $default:ty )? ),* ) => {
$(
#[derive(Debug)]
pub struct $newtype<T $( =$default )? >(pub T);
impl<U, T: std::iter::FromIterator<U>> std::iter::FromIterator<U> for $newtype<T> {
fn from_iter<I: IntoIterator<Item=U>>(iter: I) -> Self {
Self(T::from_iter(iter))
}
}
impl<T: std::default::Default> std::default::Default for $newtype<T> {
fn default() -> Self {
Self(T::default())
}
}
impl<T> std::convert::From<T> for $newtype<T> {
fn from(other: T) -> Self {
Self(other)
}
}
impl<T> std::ops::Deref for $newtype<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl<T> std::ops::DerefMut for $newtype<T> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.0
}
}
impl<T> std::convert::AsRef<T> for $newtype<T> {
fn as_ref(&self) -> &T {
&self.0
}
}
impl<T> std::convert::AsMut<T> for $newtype<T> {
fn as_mut(&mut self) -> &mut T {
&mut self.0
}
}
// std::clone and std::marker::Copy implementations
impl<T: std::clone::Clone> std::clone::Clone for $newtype<T> {
fn clone(&self) -> Self {
Self(self.0.clone())
}
}
impl<T: std::marker::Copy> std::marker::Copy for $newtype<T> {}
// std::cmp implementations
impl<T: std::cmp::PartialEq> std::cmp::PartialEq for $newtype<T> {
fn eq(&self, other: &Self) -> bool {
self.0 == other.0
}
}
impl<T: std::cmp::Eq> std::cmp::Eq for $newtype<T> {}
impl<T: std::cmp::PartialOrd> std::cmp::PartialOrd for $newtype<T> {
fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
self.0.partial_cmp(&other.0)
}
}
impl<T: std::cmp::Ord> std::cmp::Ord for $newtype<T> {
fn cmp(&self, other: &Self) -> std::cmp::Ordering {
self.0.cmp(&other.0)
}
}
// std::hash::Hash implementation
impl<T: std::hash::Hash> std::hash::Hash for $newtype<T> {
fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
self.0.hash(state);
}
}
// std::ops implementations
impl<T: std::ops::Add<Output = T>> std::ops::Add for $newtype<T> {
type Output = Self;
fn add(self, other: Self) -> Self {
Self(self.0 + other.0)
}
}
impl<T: std::ops::AddAssign> std::ops::AddAssign for $newtype<T> {
fn add_assign(&mut self, other: Self) {
self.0 += other.0;
}
}
impl<T: std::ops::BitAnd<Output = T>> std::ops::BitAnd for $newtype<T> {
type Output = Self;
fn bitand(self, rhs: Self) -> Self::Output {
Self(self.0 & rhs.0)
}
}
impl<T: std::ops::BitAndAssign + std::ops::BitAnd<Output = T> > std::ops::BitAndAssign for $newtype<T> {
fn bitand_assign(&mut self, rhs: Self) {
self.0 &= rhs.0
}
}
impl<T: std::ops::BitOr<Output = T>> std::ops::BitOr for $newtype<T> {
type Output = Self;
fn bitor(self, rhs: Self) -> Self {
Self(self.0 | rhs.0)
}
}
impl<T: std::ops::BitOrAssign> std::ops::BitOrAssign for $newtype<T> {
fn bitor_assign(&mut self, rhs: Self) {
self.0 |= rhs.0
}
}
impl<T: std::ops::BitXor<Output = T>> std::ops::BitXor for $newtype<T> {
type Output = Self;
fn bitxor(self, rhs: Self) -> Self::Output {
Self(self.0 ^ rhs.0)
}
}
impl<T: std::ops::BitXorAssign> std::ops::BitXorAssign for $newtype<T> {
fn bitxor_assign(&mut self, rhs: Self) {
self.0 ^= rhs.0
}
}
impl<T: std::ops::Div<Output = T>> std::ops::Div for $newtype<T> {
type Output = Self;
fn div(self, rhs: Self) -> Self::Output {
Self(self.0 / rhs.0)
}
}
impl<T: std::ops::DivAssign> std::ops::DivAssign for $newtype<T> {
fn div_assign(&mut self, rhs: Self) {
self.0 /= rhs.0
}
}
impl<T: std::ops::Mul<Output = T>> std::ops::Mul for $newtype<T> {
type Output = Self;
fn mul(self, rhs: Self) -> Self {
Self(self.0 * rhs.0)
}
}
impl<T: std::ops::MulAssign> std::ops::MulAssign for $newtype<T> {
fn mul_assign(&mut self, rhs: Self) {
self.0 *= rhs.0
}
}
impl<T: std::ops::Not<Output = T>> std::ops::Not for $newtype<T> {
type Output = Self;
fn not(self) -> Self::Output {
Self(!self.0)
}
}
impl<T: std::ops::Rem<Output = T>> std::ops::Rem for $newtype<T> {
type Output = Self;
fn rem(self, modulus: Self) -> Self::Output {
Self(self.0 % modulus.0)
}
}
impl<T: std::ops::RemAssign> std::ops::RemAssign for $newtype<T> {
fn rem_assign(&mut self, modulus: Self) {
self.0 %= modulus.0;
}
}
impl<T: std::ops::Sub<Output = T>> std::ops::Sub for $newtype<T> {
type Output = Self;
fn sub(self, other: Self) -> Self {
Self(self.0 - other.0)
}
}
impl<T: std::ops::SubAssign> std::ops::SubAssign for $newtype<T> {
fn sub_assign(&mut self, other: Self) {
self.0 -= other.0
}
}
impl<T: std::ops::Neg<Output = T>> std::ops::Neg for $newtype<T> {
type Output = Self;
fn neg(self) -> Self::Output {
Self(-self.0)
}
}
impl<T: std::ops::Shl<Output = T>> std::ops::Shl for $newtype<T> {
type Output = Self;
fn shl(self, rhs: Self) -> Self {
Self(self.0 << rhs.0)
}
}
impl<T: std::ops::ShlAssign> std::ops::ShlAssign for $newtype<T> {
fn shl_assign(&mut self, rhs: Self) {
self.0 <<= rhs.0;
}
}
impl<T: std::ops::Shr<Output = T>> std::ops::Shr for $newtype<T> {
type Output = Self;
fn shr(self, rhs: Self) -> Self {
Self(self.0 >> rhs.0)
}
}
impl<T: std::ops::ShrAssign> std::ops::ShrAssign for $newtype<T> {
fn shr_assign(&mut self, rhs: Self) {
self.0 >>= rhs.0;
}
}
)*
};
}
#[cfg(test)]
mod tests {
use std::collections::HashSet;
#[test]
fn it_works() {
newtype!(Id, Nested);
let mut id = Id(0);
let mut id_1 = Id(1);
// Deref
assert_eq!(*id, 0);
//DerefMut
*id = 2;
assert_eq!(*id, 2);
// Add
assert_eq!(id + id_1, Id(3));
// AddAssign
id += id_1;
assert_eq!(id, Id(3));
// Clone
let id_2 = id.clone();
assert_eq!(id, id_2);
// Copy
let id_2 = id;
assert_eq!(id, id_2);
// PartialEq
assert_eq!(id, id);
// Eq
assert_eq!(id, id);
// BitAnd
assert_eq!(Id(1) & Id(2), Id(0));
// BitAndAssign
id_1 &= Id(2);
assert_eq!(id_1, Id(0));
// BitOr
assert_eq!(Id(1) | Id(2), Id(3));
// BitOrAssign
id_1 |= Id(1);
assert_eq!(id_1, Id(1));
// BitXor
assert_eq!(Id(1) ^ Id(2), Id(3));
// BitXorAssign
id_1 ^= Id(2);
assert_eq!(id_1, Id(3));
// Div
assert_eq!(Id(2) / Id(2), Id(1));
// DivAssign
id_1 /= Id(2);
assert_eq!(id_1, Id(1));
// Mul
assert_eq!(Id(1) * Id(2), Id(2));
// MulAssign
id_1 *= Id(2);
assert_eq!(id_1, Id(2));
// Not
assert_eq!(!Id(0), Id(-1));
// Ord
assert_eq!(Id(0).cmp(&Id(0)), std::cmp::Ordering::Equal);
// PartialOrd
assert_eq!(Id(0).partial_cmp(&Id(0)), Some(std::cmp::Ordering::Equal));
// Rem
assert_eq!(Id(2) % Id(2), Id(0));
// RemAssign
id_1 %= Id(2);
assert_eq!(id_1, Id(0));
// Sub
assert_eq!(Id(1) - Id(1), Id(0));
// SubAssign
id_1 -= Id(1);
assert_eq!(id_1, Id(-1));
// Neg
assert_eq!(-Id(1), Id(-1));
// Shl
assert_eq!(Id(1) << Id(1), Id(2));
// ShlAssign
id_1 <<= Id(1);
assert_eq!(id_1, Id(-2));
// Shr
assert_eq!(Id(1) >> Id(1), Id(0));
// ShrAssign
id_1 >>= Id(1);
assert_eq!(id_1, Id(-1));
}
#[test]
fn nested() {
newtype!(A, B);
let a = A(B(5));
let b: B<i32> = 5.into();
let b: A<B<i32>> = b.into();
assert_eq!(a + b, A(B(10)))
}
#[test]
fn more_complex() {
newtype!(MySet);
let mut a = MySet(HashSet::new());
a.insert(1);
let mut b = MySet(HashSet::new());
b.insert(2);
a.extend(b.iter());
assert_eq!(a.len(), 2)
}
}