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Rollup merge of #73447 - lzutao:stabilize-result_as_deref, r=dtolnay 

Improve document for `Result::as_deref(_mut)` methods

cc #50264
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Manish Goregaokar 2020-06-18 15:21:03 -07:00 committed by GitHub
parent 1db7dc4794 4e77214583
commit f15b346f3a
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1 changed files with 40 additions and 16 deletions
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src/libcore/result.rs
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@ -1145,45 +1145,69 @@ impl<T, E: Into<!>> Result<T, E> {
}
}
#[unstable(feature = "inner_deref", reason = "newly added", issue = "50264")]
#[unstable(feature = "inner_deref", issue = "50264")]
impl<T: Deref, E> Result<T, E> {
/// Converts from `Result<T, E>` (or `&Result<T, E>`) to `Result<&T::Target, &E>`.
/// Converts from `Result<T, E>` (or `&Result<T, E>`) to `Result<&<T as Deref>::Target, &E>`.
///
/// Leaves the original `Result` in-place, creating a new one containing a reference to the
/// `Ok` type's `Deref::Target` type.
/// Coerces the [`Ok`] variant of the original [`Result`] via [`Deref`](crate::ops::Deref)
/// and returns the new [`Result`].
///
/// # Examples
///
/// ```
/// let x: Result<String, u32> = Ok("hello".to_string());
/// let y: Result<&str, &u32> = Ok("hello");
/// assert_eq!(x.as_deref(), y);
///
/// let x: Result<String, u32> = Err(42);
/// let y: Result<&str, &u32> = Err(&42);
/// assert_eq!(x.as_deref(), y);
/// ```
pub fn as_deref(&self) -> Result<&T::Target, &E> {
self.as_ref().map(|t| t.deref())
}
}
#[unstable(feature = "inner_deref", reason = "newly added", issue = "50264")]
#[unstable(feature = "inner_deref", issue = "50264")]
impl<T, E: Deref> Result<T, E> {
/// Converts from `Result<T, E>` (or `&Result<T, E>`) to `Result<&T, &E::Target>`.
/// Converts from `Result<T, E>` (or `&Result<T, E>`) to `Result<&T, &<E as Deref>::Target>`.
///
/// Leaves the original `Result` in-place, creating a new one containing a reference to the
/// `Err` type's `Deref::Target` type.
/// Coerces the [`Err`] variant of the original [`Result`] via [`Deref`](crate::ops::Deref)
/// and returns the new [`Result`].
pub fn as_deref_err(&self) -> Result<&T, &E::Target> {
self.as_ref().map_err(|e| e.deref())
}
}
#[unstable(feature = "inner_deref", reason = "newly added", issue = "50264")]
#[unstable(feature = "inner_deref", issue = "50264")]
impl<T: DerefMut, E> Result<T, E> {
/// Converts from `Result<T, E>` (or `&mut Result<T, E>`) to `Result<&mut T::Target, &mut E>`.
/// Converts from `Result<T, E>` (or `&mut Result<T, E>`) to `Result<&mut <T as DerefMut>::Target, &mut E>`.
///
/// Leaves the original `Result` in-place, creating a new one containing a mutable reference to
/// the `Ok` type's `Deref::Target` type.
/// Coerces the [`Ok`] variant of the original [`Result`] via [`DerefMut`](crate::ops::DerefMut)
/// and returns the new [`Result`].
///
/// # Examples
///
/// ```
/// let mut x: Result<String, u32> = Ok("hello".to_string());
/// let y: Result<&mut str, &mut u32> = Ok("HELLO");
/// assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);
///
/// let mut x: Result<String, u32> = Err(42);
/// let y: Result<&mut str, &mut u32> = Err(&42);
/// assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);
/// ```
pub fn as_deref_mut(&mut self) -> Result<&mut T::Target, &mut E> {
self.as_mut().map(|t| t.deref_mut())
}
}
#[unstable(feature = "inner_deref", reason = "newly added", issue = "50264")]
#[unstable(feature = "inner_deref", issue = "50264")]
impl<T, E: DerefMut> Result<T, E> {
/// Converts from `Result<T, E>` (or `&mut Result<T, E>`) to `Result<&mut T, &mut E::Target>`.
/// Converts from `Result<T, E>` (or `&mut Result<T, E>`) to `Result<&mut T, &mut <E as DerefMut>::Target>`.
///
/// Leaves the original `Result` in-place, creating a new one containing a mutable reference to
/// the `Err` type's `Deref::Target` type.
/// Coerces the [`Err`] variant of the original [`Result`] via [`DerefMut`](crate::ops::DerefMut)
/// and returns the new [`Result`].
pub fn as_deref_mut_err(&mut self) -> Result<&mut T, &mut E::Target> {
self.as_mut().map_err(|e| e.deref_mut())
}