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Diffstat (limited to 'third_party/rust/either/src')
| -rw-r--r-- | third_party/rust/either/src/lib.rs | 602 |
1 files changed, 602 insertions, 0 deletions
diff --git a/third_party/rust/either/src/lib.rs b/third_party/rust/either/src/lib.rs new file mode 100644 index 0000000000..a28340782f --- /dev/null +++ b/third_party/rust/either/src/lib.rs @@ -0,0 +1,602 @@ +//! The enum [**Either**](enum.Either.html). +//! +//! **Crate features:** +//! +//! * `"use_std"` +//! Enabled by default. Disable to make the library `#![no_std]`. +//! + +#![doc(html_root_url = "https://docs.rs/either/1/")] +#![cfg_attr(all(not(test), not(feature = "use_std")), no_std)] +#[cfg(all(not(test), not(feature = "use_std")))] +extern crate core as std; + +use std::convert::{AsRef, AsMut}; +use std::fmt; +use std::iter; +use std::ops::Deref; +use std::ops::DerefMut; +#[cfg(any(test, feature = "use_std"))] +use std::io::{self, Write, Read, BufRead}; +#[cfg(any(test, feature = "use_std"))] +use std::error::Error; + +pub use Either::{Left, Right}; + +/// `Either` represents an alternative holding one value out of +/// either of the two possible values. +/// +/// `Either` is a general purpose sum type of two parts. For representing +/// success or error, use the regular `Result<T, E>` instead. +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)] +pub enum Either<L, R> { + /// A value of type `L`. + Left(L), + /// A value of type `R`. + Right(R), +} + +macro_rules! either { + ($value:expr, $pattern:pat => $result:expr) => ( + match $value { + Either::Left($pattern) => $result, + Either::Right($pattern) => $result, + } + ) +} + +/// Macro for unwrapping the left side of an `Either`, which fails early +/// with the opposite side. Can only be used in functions that return +/// `Either` because of the early return of `Right` that it provides. +/// +/// See also `try_right!` for its dual, which applies the same just to the +/// right side. +/// +/// # Example +/// +/// ``` +/// #[macro_use] extern crate either; +/// use either::{Either, Left, Right}; +/// +/// fn twice(wrapper: Either<u32, &str>) -> Either<u32, &str> { +/// let value = try_left!(wrapper); +/// Left(value * 2) +/// } +/// +/// fn main() { +/// assert_eq!(twice(Left(2)), Left(4)); +/// assert_eq!(twice(Right("ups")), Right("ups")); +/// } +/// ``` +#[macro_export] +macro_rules! try_left { + ($expr:expr) => ( + match $expr { + $crate::Left(val) => val, + $crate::Right(err) => return $crate::Right(::std::convert::From::from(err)) + } + ) +} + +/// Dual to `try_left!`, see its documentation for more information. +#[macro_export] +macro_rules! try_right { + ($expr:expr) => ( + match $expr { + $crate::Left(err) => return $crate::Left(::std::convert::From::from(err)), + $crate::Right(val) => val + } + ) +} + +impl<L, R> Either<L, R> { + /// Return true if the value is the `Left` variant. + /// + /// ``` + /// use either::*; + /// + /// let values = [Left(1), Right("the right value")]; + /// assert_eq!(values[0].is_left(), true); + /// assert_eq!(values[1].is_left(), false); + /// ``` + pub fn is_left(&self) -> bool { + match *self { + Left(_) => true, + Right(_) => false, + } + } + + /// Return true if the value is the `Right` variant. + /// + /// ``` + /// use either::*; + /// + /// let values = [Left(1), Right("the right value")]; + /// assert_eq!(values[0].is_right(), false); + /// assert_eq!(values[1].is_right(), true); + /// ``` + pub fn is_right(&self) -> bool { + !self.is_left() + } + + /// Convert the left side of `Either<L, R>` to an `Option<L>`. + /// + /// ``` + /// use either::*; + /// + /// let left: Either<_, ()> = Left("some value"); + /// assert_eq!(left.left(), Some("some value")); + /// + /// let right: Either<(), _> = Right(321); + /// assert_eq!(right.left(), None); + /// ``` + pub fn left(self) -> Option<L> { + match self { + Left(l) => Some(l), + Right(_) => None, + } + } + + /// Convert the right side of `Either<L, R>` to an `Option<R>`. + /// + /// ``` + /// use either::*; + /// + /// let left: Either<_, ()> = Left("some value"); + /// assert_eq!(left.right(), None); + /// + /// let right: Either<(), _> = Right(321); + /// assert_eq!(right.right(), Some(321)); + /// ``` + pub fn right(self) -> Option<R> { + match self { + Left(_) => None, + Right(r) => Some(r), + } + } + + /// Convert `&Either<L, R>` to `Either<&L, &R>`. + /// + /// ``` + /// use either::*; + /// + /// let left: Either<_, ()> = Left("some value"); + /// assert_eq!(left.as_ref(), Left(&"some value")); + /// + /// let right: Either<(), _> = Right("some value"); + /// assert_eq!(right.as_ref(), Right(&"some value")); + /// ``` + pub fn as_ref(&self) -> Either<&L, &R> { + match *self { + Left(ref inner) => Left(inner), + Right(ref inner) => Right(inner), + } + } + + /// Convert `&mut Either<L, R>` to `Either<&mut L, &mut R>`. + /// + /// ``` + /// use either::*; + /// + /// fn mutate_left(value: &mut Either<u32, u32>) { + /// if let Some(l) = value.as_mut().left() { + /// *l = 999; + /// } + /// } + /// + /// let mut left = Left(123); + /// let mut right = Right(123); + /// mutate_left(&mut left); + /// mutate_left(&mut right); + /// assert_eq!(left, Left(999)); + /// assert_eq!(right, Right(123)); + /// ``` + pub fn as_mut(&mut self) -> Either<&mut L, &mut R> { + match *self { + Left(ref mut inner) => Left(inner), + Right(ref mut inner) => Right(inner), + } + } + + /// Convert `Either<L, R>` to `Either<R, L>`. + /// + /// ``` + /// use either::*; + /// + /// let left: Either<_, ()> = Left(123); + /// assert_eq!(left.flip(), Right(123)); + /// + /// let right: Either<(), _> = Right("some value"); + /// assert_eq!(right.flip(), Left("some value")); + /// ``` + pub fn flip(self) -> Either<R, L> { + match self { + Left(l) => Right(l), + Right(r) => Left(r), + } + } + + /// Apply the function `f` on the value in the `Left` variant if it is present rewrapping the + /// result in `Left`. + /// + /// ``` + /// use either::*; + /// + /// let left: Either<_, u32> = Left(123); + /// assert_eq!(left.map_left(|x| x * 2), Left(246)); + /// + /// let right: Either<u32, _> = Right(123); + /// assert_eq!(right.map_left(|x| x * 2), Right(123)); + /// ``` + pub fn map_left<F, M>(self, f: F) -> Either<M, R> + where F: FnOnce(L) -> M + { + match self { + Left(l) => Left(f(l)), + Right(r) => Right(r), + } + } + + /// Apply the function `f` on the value in the `Right` variant if it is present rewrapping the + /// result in `Right`. + /// + /// ``` + /// use either::*; + /// + /// let left: Either<_, u32> = Left(123); + /// assert_eq!(left.map_right(|x| x * 2), Left(123)); + /// + /// let right: Either<u32, _> = Right(123); + /// assert_eq!(right.map_right(|x| x * 2), Right(246)); + /// ``` + pub fn map_right<F, S>(self, f: F) -> Either<L, S> + where F: FnOnce(R) -> S + { + match self { + Left(l) => Left(l), + Right(r) => Right(f(r)), + } + } + + /// Apply one of two functions depending on contents, unifying their result. If the value is + /// `Left(L)` then the first function `f` is applied; if it is `Right(R)` then the second + /// function `g` is applied. + /// + /// ``` + /// use either::*; + /// + /// fn square(n: u32) -> i32 { (n * n) as i32 } + /// fn negate(n: i32) -> i32 { -n } + /// + /// let left: Either<u32, i32> = Left(4); + /// assert_eq!(left.either(square, negate), 16); + /// + /// let right: Either<u32, i32> = Right(-4); + /// assert_eq!(right.either(square, negate), 4); + /// ``` + pub fn either<F, G, T>(self, f: F, g: G) -> T + where F: FnOnce(L) -> T, + G: FnOnce(R) -> T + { + match self { + Left(l) => f(l), + Right(r) => g(r), + } + } + + /// Apply the function `f` on the value in the `Left` variant if it is present. + /// + /// ``` + /// use either::*; + /// + /// let left: Either<_, u32> = Left(123); + /// assert_eq!(left.left_and_then::<_,()>(|x| Right(x * 2)), Right(246)); + /// + /// let right: Either<u32, _> = Right(123); + /// assert_eq!(right.left_and_then(|x| Right::<(), _>(x * 2)), Right(123)); + /// ``` + pub fn left_and_then<F, S>(self, f: F) -> Either<S, R> + where F: FnOnce(L) -> Either<S, R> + { + match self { + Left(l) => f(l), + Right(r) => Right(r), + } + } + + /// Apply the function `f` on the value in the `Right` variant if it is present. + /// + /// ``` + /// use either::*; + /// + /// let left: Either<_, u32> = Left(123); + /// assert_eq!(left.right_and_then(|x| Right(x * 2)), Left(123)); + /// + /// let right: Either<u32, _> = Right(123); + /// assert_eq!(right.right_and_then(|x| Right(x * 2)), Right(246)); + /// ``` + pub fn right_and_then<F, S>(self, f: F) -> Either<L, S> + where F: FnOnce(R) -> Either<L, S> + { + match self { + Left(l) => Left(l), + Right(r) => f(r), + } + } +} + +/// Convert from `Result` to `Either` with `Ok => Right` and `Err => Left`. +impl<L, R> From<Result<R, L>> for Either<L, R> { + fn from(r: Result<R, L>) -> Self { + match r { + Err(e) => Left(e), + Ok(o) => Right(o), + } + } +} + +/// Convert from `Either` to `Result` with `Right => Ok` and `Left => Err`. +impl<L, R> Into<Result<R, L>> for Either<L, R> { + fn into(self) -> Result<R, L> { + match self { + Left(l) => Err(l), + Right(r) => Ok(r), + } + } +} + +impl<L, R, A> Extend<A> for Either<L, R> + where L: Extend<A>, R: Extend<A> +{ + fn extend<T>(&mut self, iter: T) + where T: IntoIterator<Item=A> + { + either!(*self, ref mut inner => inner.extend(iter)) + } +} + +/// `Either<L, R>` is an iterator if both `L` and `R` are iterators. +impl<L, R> Iterator for Either<L, R> + where L: Iterator, R: Iterator<Item=L::Item> +{ + type Item = L::Item; + + fn next(&mut self) -> Option<Self::Item> { + either!(*self, ref mut inner => inner.next()) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + either!(*self, ref inner => inner.size_hint()) + } + + fn fold<Acc, G>(self, init: Acc, f: G) -> Acc + where G: FnMut(Acc, Self::Item) -> Acc, + { + either!(self, inner => inner.fold(init, f)) + } + + fn count(self) -> usize { + either!(self, inner => inner.count()) + } + + fn last(self) -> Option<Self::Item> { + either!(self, inner => inner.last()) + } + + fn nth(&mut self, n: usize) -> Option<Self::Item> { + either!(*self, ref mut inner => inner.nth(n)) + } + + fn collect<B>(self) -> B + where B: iter::FromIterator<Self::Item> + { + either!(self, inner => inner.collect()) + } + + fn all<F>(&mut self, f: F) -> bool + where F: FnMut(Self::Item) -> bool + { + either!(*self, ref mut inner => inner.all(f)) + } +} + +impl<L, R> DoubleEndedIterator for Either<L, R> + where L: DoubleEndedIterator, R: DoubleEndedIterator<Item=L::Item> +{ + fn next_back(&mut self) -> Option<Self::Item> { + either!(*self, ref mut inner => inner.next_back()) + } +} + +impl<L, R> ExactSizeIterator for Either<L, R> + where L: ExactSizeIterator, R: ExactSizeIterator<Item=L::Item> +{ +} + +#[cfg(any(test, feature = "use_std"))] +/// `Either<L, R>` implements `Read` if both `L` and `R` do. +/// +/// Requires crate feature `"use_std"` +impl<L, R> Read for Either<L, R> + where L: Read, R: Read +{ + fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { + either!(*self, ref mut inner => inner.read(buf)) + } + + fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> { + either!(*self, ref mut inner => inner.read_to_end(buf)) + } +} + +#[cfg(any(test, feature = "use_std"))] +/// Requires crate feature `"use_std"` +impl<L, R> BufRead for Either<L, R> + where L: BufRead, R: BufRead +{ + fn fill_buf(&mut self) -> io::Result<&[u8]> { + either!(*self, ref mut inner => inner.fill_buf()) + } + + fn consume(&mut self, amt: usize) { + either!(*self, ref mut inner => inner.consume(amt)) + } +} + +#[cfg(any(test, feature = "use_std"))] +/// `Either<L, R>` implements `Write` if both `L` and `R` do. +/// +/// Requires crate feature `"use_std"` +impl<L, R> Write for Either<L, R> + where L: Write, R: Write +{ + fn write(&mut self, buf: &[u8]) -> io::Result<usize> { + either!(*self, ref mut inner => inner.write(buf)) + } + + fn flush(&mut self) -> io::Result<()> { + either!(*self, ref mut inner => inner.flush()) + } +} + +impl<L, R, Target> AsRef<Target> for Either<L, R> + where L: AsRef<Target>, R: AsRef<Target> +{ + fn as_ref(&self) -> &Target { + either!(*self, ref inner => inner.as_ref()) + } +} + +impl<L, R, Target> AsMut<Target> for Either<L, R> + where L: AsMut<Target>, R: AsMut<Target> +{ + fn as_mut(&mut self) -> &mut Target { + either!(*self, ref mut inner => inner.as_mut()) + } +} + +impl<L, R> Deref for Either<L, R> + where L: Deref, R: Deref<Target=L::Target> +{ + type Target = L::Target; + + fn deref(&self) -> &Self::Target { + either!(*self, ref inner => &*inner) + } +} + +impl<L, R> DerefMut for Either<L, R> + where L: DerefMut, R: DerefMut<Target=L::Target> +{ + fn deref_mut(&mut self) -> &mut Self::Target { + either!(*self, ref mut inner => &mut *inner) + } +} + +#[cfg(any(test, feature = "use_std"))] +/// `Either` implements `Error` if *both* `L` and `R` implement it. +impl<L, R> Error for Either<L, R> + where L: Error, R: Error +{ + fn description(&self) -> &str { + either!(*self, ref inner => inner.description()) + } + + fn cause(&self) -> Option<&Error> { + either!(*self, ref inner => inner.cause()) + } +} + +impl<L, R> fmt::Display for Either<L, R> + where L: fmt::Display, R: fmt::Display +{ + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + either!(*self, ref inner => inner.fmt(f)) + } +} + +#[test] +fn basic() { + let mut e = Left(2); + let r = Right(2); + assert_eq!(e, Left(2)); + e = r; + assert_eq!(e, Right(2)); + assert_eq!(e.left(), None); + assert_eq!(e.right(), Some(2)); + assert_eq!(e.as_ref().right(), Some(&2)); + assert_eq!(e.as_mut().right(), Some(&mut 2)); +} + +#[test] +fn macros() { + fn a() -> Either<u32, u32> { + let x: u32 = try_left!(Right(1337u32)); + Left(x * 2) + } + assert_eq!(a(), Right(1337)); + + fn b() -> Either<String, &'static str> { + Right(try_right!(Left("foo bar"))) + } + assert_eq!(b(), Left(String::from("foo bar"))); +} + +#[test] +fn deref() { + fn is_str(_: &str) {} + let value: Either<String, &str> = Left(String::from("test")); + is_str(&*value); +} + +#[test] +fn iter() { + let x = 3; + let mut iter = match x { + 1...3 => Left(0..10), + _ => Right(17..), + }; + + assert_eq!(iter.next(), Some(0)); + assert_eq!(iter.count(), 9); +} + +#[test] +fn read_write() { + use std::io; + + let use_stdio = false; + let mockdata = [0xff; 256]; + + let mut reader = if use_stdio { + Left(io::stdin()) + } else { + Right(&mockdata[..]) + }; + + let mut buf = [0u8; 16]; + assert_eq!(reader.read(&mut buf).unwrap(), buf.len()); + assert_eq!(&buf, &mockdata[..buf.len()]); + + let mut mockbuf = [0u8; 256]; + let mut writer = if use_stdio { + Left(io::stdout()) + } else { + Right(&mut mockbuf[..]) + }; + + let buf = [1u8; 16]; + assert_eq!(writer.write(&buf).unwrap(), buf.len()); +} + +#[test] +fn error() { + let invalid_utf8 = b"\xff"; + let res = || -> Result<_, Either<_, _>> { + try!(::std::str::from_utf8(invalid_utf8).map_err(Left)); + try!("x".parse::<i32>().map_err(Right)); + Ok(()) + }(); + assert!(res.is_err()); + res.unwrap_err().description(); // make sure this can be called +} |