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Auto merge of #74948 - lzutao:stalize-result-as-deref, r=dtolnay

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Stabilize `Result::as_deref` and `as_deref_mut`

FCP completed in https://github.com/rust-lang/rust/issues/50264#issuecomment-645681400.

This PR stabilizes two new APIs for `std::result::Result`:
```rust
fn as_deref(&self) -> Result<&T::Target, &E> where T: Deref;
fn as_deref_mut(&mut self) -> Result<&mut T::Target, &mut E> where T: DerefMut;
```

This PR also removes two rarely used unstable APIs from `Result`:
```rust
fn as_deref_err(&self) -> Result<&T, &E::Target> where E: Deref;
fn as_deref_mut_err(&mut self) -> Result<&mut T, &mut E::Target> where E: DerefMut;
```

Closes #50264
This commit is contained in:
bors 2020-08-02 23:55:12 +00:00
commit 19ecce332e
13 changed files with 14 additions and 192 deletions
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28
library/core/src/result.rs
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@ -1145,7 +1145,6 @@ impl<T, E: Into<!>> Result<T, E> {
}
}
#[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 as Deref>::Target, &E>`.
///
@ -1155,7 +1154,6 @@ impl<T: Deref, E> Result<T, E> {
/// # Examples
///
/// ```
/// #![feature(inner_deref)]
/// let x: Result<String, u32> = Ok("hello".to_string());
/// let y: Result<&str, &u32> = Ok("hello");
/// assert_eq!(x.as_deref(), y);
@ -1164,23 +1162,12 @@ impl<T: Deref, E> Result<T, E> {
/// let y: Result<&str, &u32> = Err(&42);
/// assert_eq!(x.as_deref(), y);
/// ```
#[stable(feature = "inner_deref", since = "1.47.0")]
pub fn as_deref(&self) -> Result<&T::Target, &E> {
self.as_ref().map(|t| t.deref())
}
}
#[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 as Deref>::Target>`.
///
/// 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", issue = "50264")]
impl<T: DerefMut, E> Result<T, E> {
/// Converts from `Result<T, E>` (or `&mut Result<T, E>`) to `Result<&mut <T as DerefMut>::Target, &mut E>`.
///
@ -1190,7 +1177,6 @@ impl<T: DerefMut, E> Result<T, E> {
/// # Examples
///
/// ```
/// #![feature(inner_deref)]
/// let mut s = "HELLO".to_string();
/// let mut x: Result<String, u32> = Ok("hello".to_string());
/// let y: Result<&mut str, &mut u32> = Ok(&mut s);
@ -1201,22 +1187,12 @@ impl<T: DerefMut, E> Result<T, E> {
/// let y: Result<&mut str, &mut u32> = Err(&mut i);
/// assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);
/// ```
#[stable(feature = "inner_deref", since = "1.47.0")]
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", 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 as DerefMut>::Target>`.
///
/// 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())
}
}
impl<T, E> Result<Option<T>, E> {
/// Transposes a `Result` of an `Option` into an `Option` of a `Result`.
///