Rollup merge of #68222 - alexcrichton:update-wasi-libc, r=kennytm

[rust.git] / src / libcore / result.rs

diff --git a/src/libcore/result.rs b/src/libcore/result.rs
index 5cfc81097dd44a3b9b7a5e3381c5e08ab34bbe7c..c657ce33f60adccb380b82001affb7dfd59606ae 100644 (file)
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -282,10 +282,7 @@ impl<T, E> Result<T, E> {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const fn is_ok(&self) -> bool {
-        match *self {
-            Ok(_) => true,
-            Err(_) => false,
-        }
+        matches!(*self, Ok(_))
     }
 
     /// Returns `true` if the result is [`Err`].
@@ -957,6 +954,7 @@ impl<T, E: fmt::Debug> Result<T, E> {
     /// x.unwrap(); // panics with `emergency failure`
     /// ```
     #[inline]
+    #[track_caller]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn unwrap(self) -> T {
         match self {
@@ -984,6 +982,7 @@ pub fn unwrap(self) -> T {
     /// x.expect("Testing expect"); // panics with `Testing expect: emergency failure`
     /// ```
     #[inline]
+    #[track_caller]
     #[stable(feature = "result_expect", since = "1.4.0")]
     pub fn expect(self, msg: &str) -> T {
         match self {
@@ -1017,6 +1016,7 @@ impl<T: fmt::Debug, E> Result<T, E> {
     /// assert_eq!(x.unwrap_err(), "emergency failure");
     /// ```
     #[inline]
+    #[track_caller]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn unwrap_err(self) -> E {
         match self {
@@ -1044,6 +1044,7 @@ pub fn unwrap_err(self) -> E {
     /// x.expect_err("Testing expect_err"); // panics with `Testing expect_err: 10`
     /// ```
     #[inline]
+    #[track_caller]
     #[stable(feature = "result_expect_err", since = "1.17.0")]
     pub fn expect_err(self, msg: &str) -> E {
         match self {
@@ -1091,13 +1092,51 @@ pub fn unwrap_or_default(self) -> T {
     }
 }
 
+#[unstable(feature = "unwrap_infallible", reason = "newly added", issue = "61695")]
+impl<T, E: Into<!>> Result<T, E> {
+    /// Unwraps a result that can never be an [`Err`], yielding the content of the [`Ok`].
+    ///
+    /// Unlike [`unwrap`], this method is known to never panic on the
+    /// result types it is implemented for. Therefore, it can be used
+    /// instead of `unwrap` as a maintainability safeguard that will fail
+    /// to compile if the error type of the `Result` is later changed
+    /// to an error that can actually occur.
+    ///
+    /// [`Ok`]: enum.Result.html#variant.Ok
+    /// [`Err`]: enum.Result.html#variant.Err
+    /// [`unwrap`]: enum.Result.html#method.unwrap
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// # #![feature(never_type)]
+    /// # #![feature(unwrap_infallible)]
+    ///
+    /// fn only_good_news() -> Result<String, !> {
+    ///     Ok("this is fine".into())
+    /// }
+    ///
+    /// let s: String = only_good_news().into_ok();
+    /// println!("{}", s);
+    /// ```
+    #[inline]
+    pub fn into_ok(self) -> T {
+        match self {
+            Ok(x) => x,
+            Err(e) => e.into(),
+        }
+    }
+}
+
 #[unstable(feature = "inner_deref", reason = "newly added", issue = "50264")]
 impl<T: Deref, E> Result<T, E> {
     /// Converts from `Result<T, E>` (or `&Result<T, E>`) to `Result<&T::Target, &E>`.
     ///
     /// Leaves the original `Result` in-place, creating a new one containing a reference to the
     /// `Ok` type's `Deref::Target` type.
-    pub fn as_deref_ok(&self) -> Result<&T::Target, &E> {
+    pub fn as_deref(&self) -> Result<&T::Target, &E> {
         self.as_ref().map(|t| t.deref())
     }
 }
@@ -1113,24 +1152,13 @@ pub fn as_deref_err(&self) -> Result<&T, &E::Target> {
     }
 }
 
-#[unstable(feature = "inner_deref", reason = "newly added", issue = "50264")]
-impl<T: Deref, E: Deref> Result<T, E> {
-    /// Converts from `Result<T, E>` (or `&Result<T, E>`) to `Result<&T::Target, &E::Target>`.
-    ///
-    /// Leaves the original `Result` in-place, creating a new one containing a reference to both
-    /// the `Ok` and `Err` types' `Deref::Target` types.
-    pub fn as_deref(&self) -> Result<&T::Target, &E::Target> {
-        self.as_ref().map(|t| t.deref()).map_err(|e| e.deref())
-    }
-}
-
 #[unstable(feature = "inner_deref", reason = "newly added", 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>`.
     ///
     /// Leaves the original `Result` in-place, creating a new one containing a mutable reference to
     /// the `Ok` type's `Deref::Target` type.
-    pub fn as_deref_mut_ok(&mut self) -> Result<&mut T::Target, &mut E> {
+    pub fn as_deref_mut(&mut self) -> Result<&mut T::Target, &mut E> {
         self.as_mut().map(|t| t.deref_mut())
     }
 }
@@ -1146,18 +1174,6 @@ pub fn as_deref_mut_err(&mut self) -> Result<&mut T, &mut E::Target> {
     }
 }
 
-#[unstable(feature = "inner_deref", reason = "newly added", issue = "50264")]
-impl<T: DerefMut, E: DerefMut> Result<T, E> {
-    /// Converts from `Result<T, E>` (or `&mut Result<T, E>`) to
-    /// `Result<&mut T::Target, &mut E::Target>`.
-    ///
-    /// Leaves the original `Result` in-place, creating a new one containing a mutable reference to
-    /// both the `Ok` and `Err` types' `Deref::Target` types.
-    pub fn as_deref_mut(&mut self) -> Result<&mut T::Target, &mut E::Target> {
-        self.as_mut().map(|t| t.deref_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`.
     ///
@@ -1188,6 +1204,7 @@ pub fn transpose(self) -> Option<Result<T, E>> {
 // This is a separate function to reduce the code size of the methods
 #[inline(never)]
 #[cold]
+#[track_caller]
 fn unwrap_failed(msg: &str, error: &dyn fmt::Debug) -> ! {
     panic!("{}: {:?}", msg, error)
 }