Rollup merge of #92444 - dtolnay:coremethods, r=joshtriplett

Consolidate Result's and Option's methods into fewer impl blocks

`Result`'s and `Option`'s methods have historically been separated up into `impl` blocks based on their trait bounds, with the bounds specified on type parameters of the impl block. I find this unhelpful because closely related methods, like `unwrap_or` and `unwrap_or_default`, end up disproportionately far apart in source code and rustdocs:

<pre>
impl&lt;T&gt; Option&lt;T&gt; {
    pub fn unwrap_or(self, default: T) -&gt; T {
        ...
    }

    <img alt="one eternity later" src="https://user-images.githubusercontent.com/1940490/147780325-ad4e01a4-c971-436e-bdf4-e755f2d35f15.jpg" width="750">
}

impl&lt;T: Default&gt; Option&lt;T&gt; {
    pub fn unwrap_or_default(self) -&gt; T {
        ...
    }
}
</pre>

I'd prefer for method to be in as few impl blocks as possible, with the most logical grouping within each impl block. Any bounds needed can be written as `where` clauses on the method instead:

```rust
impl<T> Option<T> {
    pub fn unwrap_or(self, default: T) -> T {
        ...
    }

    pub fn unwrap_or_default(self) -> T
    where
        T: Default,
    {
        ...
    }
}
```

*Warning: the end-to-end diff of this PR is computed confusingly by git / rendered confusingly by GitHub; it's practically impossible to review that way. I've broken the PR into commits that move small groups of methods for which git behaves better &mdash; these each should be easily individually reviewable.*

2 files changed, 449 insertions, 428 deletions

diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index e6312b8b2d9..0022df4f65f 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -810,6 +810,45 @@ impl<T> Option<T> {
         }
     }
 
+    /// Returns the contained [`Some`] value or a default.
+    ///
+    /// Consumes the `self` argument then, if [`Some`], returns the contained
+    /// value, otherwise if [`None`], returns the [default value] for that
+    /// type.
+    ///
+    /// # Examples
+    ///
+    /// Converts a string to an integer, turning poorly-formed strings
+    /// into 0 (the default value for integers). [`parse`] converts
+    /// a string to any other type that implements [`FromStr`], returning
+    /// [`None`] on error.
+    ///
+    /// ```
+    /// let good_year_from_input = "1909";
+    /// let bad_year_from_input = "190blarg";
+    /// let good_year = good_year_from_input.parse().ok().unwrap_or_default();
+    /// let bad_year = bad_year_from_input.parse().ok().unwrap_or_default();
+    ///
+    /// assert_eq!(1909, good_year);
+    /// assert_eq!(0, bad_year);
+    /// ```
+    ///
+    /// [default value]: Default::default
+    /// [`parse`]: str::parse
+    /// [`FromStr`]: crate::str::FromStr
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_unstable(feature = "const_option_ext", issue = "91930")]
+    pub const fn unwrap_or_default(self) -> T
+    where
+        T: ~const Default,
+    {
+        match self {
+            Some(x) => x,
+            None => Default::default(),
+        }
+    }
+
     /// Returns the contained [`Some`] value, consuming the `self` value,
     /// without checking that the value is not [`None`].
     ///
@@ -1033,6 +1072,58 @@ impl<T> Option<T> {
         }
     }
 
+    /// Converts from `Option<T>` (or `&Option<T>`) to `Option<&T::Target>`.
+    ///
+    /// Leaves the original Option in-place, creating a new one with a reference
+    /// to the original one, additionally coercing the contents via [`Deref`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let x: Option<String> = Some("hey".to_owned());
+    /// assert_eq!(x.as_deref(), Some("hey"));
+    ///
+    /// let x: Option<String> = None;
+    /// assert_eq!(x.as_deref(), None);
+    /// ```
+    #[stable(feature = "option_deref", since = "1.40.0")]
+    #[rustc_const_unstable(feature = "const_option_ext", issue = "91930")]
+    pub const fn as_deref(&self) -> Option<&T::Target>
+    where
+        T: ~const Deref,
+    {
+        match self.as_ref() {
+            Some(t) => Some(t.deref()),
+            None => None,
+        }
+    }
+
+    /// Converts from `Option<T>` (or `&mut Option<T>`) to `Option<&mut T::Target>`.
+    ///
+    /// Leaves the original `Option` in-place, creating a new one containing a mutable reference to
+    /// the inner type's [`Deref::Target`] type.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut x: Option<String> = Some("hey".to_owned());
+    /// assert_eq!(x.as_deref_mut().map(|x| {
+    ///     x.make_ascii_uppercase();
+    ///     x
+    /// }), Some("HEY".to_owned().as_mut_str()));
+    /// ```
+    #[stable(feature = "option_deref", since = "1.40.0")]
+    #[rustc_const_unstable(feature = "const_option_ext", issue = "91930")]
+    pub const fn as_deref_mut(&mut self) -> Option<&mut T::Target>
+    where
+        T: ~const DerefMut,
+    {
+        match self.as_mut() {
+            Some(t) => Some(t.deref_mut()),
+            None => None,
+        }
+    }
+
     /////////////////////////////////////////////////////////////////////////
     // Iterator constructors
     /////////////////////////////////////////////////////////////////////////
@@ -1581,7 +1672,7 @@ impl<T, U> Option<(T, U)> {
     }
 }
 
-impl<T: Copy> Option<&T> {
+impl<T> Option<&T> {
     /// Maps an `Option<&T>` to an `Option<T>` by copying the contents of the
     /// option.
     ///
@@ -1597,7 +1688,10 @@ impl<T: Copy> Option<&T> {
     #[must_use = "`self` will be dropped if the result is not used"]
     #[stable(feature = "copied", since = "1.35.0")]
     #[rustc_const_unstable(feature = "const_option", issue = "67441")]
-    pub const fn copied(self) -> Option<T> {
+    pub const fn copied(self) -> Option<T>
+    where
+        T: Copy,
+    {
         // FIXME: this implementation, which sidesteps using `Option::map` since it's not const
         // ready yet, should be reverted when possible to avoid code repetition
         match self {
@@ -1605,33 +1699,7 @@ impl<T: Copy> Option<&T> {
             None => None,
         }
     }
-}
 
-impl<T: Copy> Option<&mut T> {
-    /// Maps an `Option<&mut T>` to an `Option<T>` by copying the contents of the
-    /// option.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// let mut x = 12;
-    /// let opt_x = Some(&mut x);
-    /// assert_eq!(opt_x, Some(&mut 12));
-    /// let copied = opt_x.copied();
-    /// assert_eq!(copied, Some(12));
-    /// ```
-    #[must_use = "`self` will be dropped if the result is not used"]
-    #[stable(feature = "copied", since = "1.35.0")]
-    #[rustc_const_unstable(feature = "const_option_ext", issue = "91930")]
-    pub const fn copied(self) -> Option<T> {
-        match self {
-            Some(&mut t) => Some(t),
-            None => None,
-        }
-    }
-}
-
-impl<T: Clone> Option<&T> {
     /// Maps an `Option<&T>` to an `Option<T>` by cloning the contents of the
     /// option.
     ///
@@ -1658,8 +1726,8 @@ impl<T: Clone> Option<&T> {
     }
 }
 
-impl<T: Clone> Option<&mut T> {
-    /// Maps an `Option<&mut T>` to an `Option<T>` by cloning the contents of the
+impl<T> Option<&mut T> {
+    /// Maps an `Option<&mut T>` to an `Option<T>` by copying the contents of the
     /// option.
     ///
     /// # Examples
@@ -1668,115 +1736,43 @@ impl<T: Clone> Option<&mut T> {
     /// let mut x = 12;
     /// let opt_x = Some(&mut x);
     /// assert_eq!(opt_x, Some(&mut 12));
-    /// let cloned = opt_x.cloned();
-    /// assert_eq!(cloned, Some(12));
+    /// let copied = opt_x.copied();
+    /// assert_eq!(copied, Some(12));
     /// ```
     #[must_use = "`self` will be dropped if the result is not used"]
-    #[stable(since = "1.26.0", feature = "option_ref_mut_cloned")]
-    #[rustc_const_unstable(feature = "const_option_cloned", issue = "91582")]
-    pub const fn cloned(self) -> Option<T>
-    where
-        T: ~const Clone,
-    {
-        match self {
-            Some(t) => Some(t.clone()),
-            None => None,
-        }
-    }
-}
-
-impl<T: Default> Option<T> {
-    /// Returns the contained [`Some`] value or a default.
-    ///
-    /// Consumes the `self` argument then, if [`Some`], returns the contained
-    /// value, otherwise if [`None`], returns the [default value] for that
-    /// type.
-    ///
-    /// # Examples
-    ///
-    /// Converts a string to an integer, turning poorly-formed strings
-    /// into 0 (the default value for integers). [`parse`] converts
-    /// a string to any other type that implements [`FromStr`], returning
-    /// [`None`] on error.
-    ///
-    /// ```
-    /// let good_year_from_input = "1909";
-    /// let bad_year_from_input = "190blarg";
-    /// let good_year = good_year_from_input.parse().ok().unwrap_or_default();
-    /// let bad_year = bad_year_from_input.parse().ok().unwrap_or_default();
-    ///
-    /// assert_eq!(1909, good_year);
-    /// assert_eq!(0, bad_year);
-    /// ```
-    ///
-    /// [default value]: Default::default
-    /// [`parse`]: str::parse
-    /// [`FromStr`]: crate::str::FromStr
-    #[inline]
-    #[stable(feature = "rust1", since = "1.0.0")]
+    #[stable(feature = "copied", since = "1.35.0")]
     #[rustc_const_unstable(feature = "const_option_ext", issue = "91930")]
-    pub const fn unwrap_or_default(self) -> T
+    pub const fn copied(self) -> Option<T>
     where
-        T: ~const Default,
+        T: Copy,
     {
         match self {
-            Some(x) => x,
-            None => Default::default(),
-        }
-    }
-}
-
-impl<T: Deref> Option<T> {
-    /// Converts from `Option<T>` (or `&Option<T>`) to `Option<&T::Target>`.
-    ///
-    /// Leaves the original Option in-place, creating a new one with a reference
-    /// to the original one, additionally coercing the contents via [`Deref`].
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// let x: Option<String> = Some("hey".to_owned());
-    /// assert_eq!(x.as_deref(), Some("hey"));
-    ///
-    /// let x: Option<String> = None;
-    /// assert_eq!(x.as_deref(), None);
-    /// ```
-    #[stable(feature = "option_deref", since = "1.40.0")]
-    #[rustc_const_unstable(feature = "const_option_ext", issue = "91930")]
-    pub const fn as_deref(&self) -> Option<&T::Target>
-    where
-        T: ~const Deref,
-    {
-        match self.as_ref() {
-            Some(t) => Some(t.deref()),
+            Some(&mut t) => Some(t),
             None => None,
         }
     }
-}
 
-impl<T: DerefMut> Option<T> {
-    /// Converts from `Option<T>` (or `&mut Option<T>`) to `Option<&mut T::Target>`.
-    ///
-    /// Leaves the original `Option` in-place, creating a new one containing a mutable reference to
-    /// the inner type's [`Deref::Target`] type.
+    /// Maps an `Option<&mut T>` to an `Option<T>` by cloning the contents of the
+    /// option.
     ///
     /// # Examples
     ///
     /// ```
-    /// let mut x: Option<String> = Some("hey".to_owned());
-    /// assert_eq!(x.as_deref_mut().map(|x| {
-    ///     x.make_ascii_uppercase();
-    ///     x
-    /// }), Some("HEY".to_owned().as_mut_str()));
+    /// let mut x = 12;
+    /// let opt_x = Some(&mut x);
+    /// assert_eq!(opt_x, Some(&mut 12));
+    /// let cloned = opt_x.cloned();
+    /// assert_eq!(cloned, Some(12));
     /// ```
-    #[stable(feature = "option_deref", since = "1.40.0")]
-    #[rustc_const_unstable(feature = "const_option_ext", issue = "91930")]
-    pub const fn as_deref_mut(&mut self) -> Option<&mut T::Target>
+    #[must_use = "`self` will be dropped if the result is not used"]
+    #[stable(since = "1.26.0", feature = "option_ref_mut_cloned")]
+    #[rustc_const_unstable(feature = "const_option_cloned", issue = "91582")]
+    pub const fn cloned(self) -> Option<T>
     where
-        T: ~const DerefMut,
+        T: ~const Clone,
     {
-        match self.as_mut() {
-            Some(t) => Some(t.deref_mut()),
+        match self {
+            Some(t) => Some(t.clone()),
             None => None,
         }
     }
diff --git a/library/core/src/result.rs b/library/core/src/result.rs
index 3cde63493d3..f46632e7a8d 100644
--- a/library/core/src/result.rs
+++ b/library/core/src/result.rs
@@ -901,6 +901,56 @@ impl<T, E> Result<T, E> {
         self
     }
 
+    /// Converts from `Result<T, E>` (or `&Result<T, E>`) to `Result<&<T as Deref>::Target, &E>`.
+    ///
+    /// 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);
+    /// ```
+    #[stable(feature = "inner_deref", since = "1.47.0")]
+    pub fn as_deref(&self) -> Result<&T::Target, &E>
+    where
+        T: Deref,
+    {
+        self.as_ref().map(|t| t.deref())
+    }
+
+    /// Converts from `Result<T, E>` (or `&mut Result<T, E>`) to `Result<&mut <T as DerefMut>::Target, &mut E>`.
+    ///
+    /// Coerces the [`Ok`] variant of the original [`Result`] via [`DerefMut`](crate::ops::DerefMut)
+    /// and returns the new [`Result`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// 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);
+    /// assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);
+    ///
+    /// let mut i = 42;
+    /// let mut x: Result<String, u32> = Err(42);
+    /// 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>
+    where
+        T: DerefMut,
+    {
+        self.as_mut().map(|t| t.deref_mut())
+    }
+
     /////////////////////////////////////////////////////////////////////////
     // Iterator constructors
     /////////////////////////////////////////////////////////////////////////
@@ -951,6 +1001,253 @@ impl<T, E> Result<T, E> {
         IterMut { inner: self.as_mut().ok() }
     }
 
+    /////////////////////////////////////////////////////////////////////////
+    // Extract a value
+    /////////////////////////////////////////////////////////////////////////
+
+    /// Returns the contained [`Ok`] value, consuming the `self` value.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the value is an [`Err`], with a panic message including the
+    /// passed message, and the content of the [`Err`].
+    ///
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```should_panic
+    /// let x: Result<u32, &str> = Err("emergency failure");
+    /// 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
+    where
+        E: fmt::Debug,
+    {
+        match self {
+            Ok(t) => t,
+            Err(e) => unwrap_failed(msg, &e),
+        }
+    }
+
+    /// Returns the contained [`Ok`] value, consuming the `self` value.
+    ///
+    /// Because this function may panic, its use is generally discouraged.
+    /// Instead, prefer to use pattern matching and handle the [`Err`]
+    /// case explicitly, or call [`unwrap_or`], [`unwrap_or_else`], or
+    /// [`unwrap_or_default`].
+    ///
+    /// [`unwrap_or`]: Result::unwrap_or
+    /// [`unwrap_or_else`]: Result::unwrap_or_else
+    /// [`unwrap_or_default`]: Result::unwrap_or_default
+    ///
+    /// # Panics
+    ///
+    /// Panics if the value is an [`Err`], with a panic message provided by the
+    /// [`Err`]'s value.
+    ///
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let x: Result<u32, &str> = Ok(2);
+    /// assert_eq!(x.unwrap(), 2);
+    /// ```
+    ///
+    /// ```should_panic
+    /// let x: Result<u32, &str> = Err("emergency failure");
+    /// x.unwrap(); // panics with `emergency failure`
+    /// ```
+    #[inline]
+    #[track_caller]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn unwrap(self) -> T
+    where
+        E: fmt::Debug,
+    {
+        match self {
+            Ok(t) => t,
+            Err(e) => unwrap_failed("called `Result::unwrap()` on an `Err` value", &e),
+        }
+    }
+
+    /// Returns the contained [`Ok`] value or a default
+    ///
+    /// Consumes the `self` argument then, if [`Ok`], returns the contained
+    /// value, otherwise if [`Err`], returns the default value for that
+    /// type.
+    ///
+    /// # Examples
+    ///
+    /// Converts a string to an integer, turning poorly-formed strings
+    /// into 0 (the default value for integers). [`parse`] converts
+    /// a string to any other type that implements [`FromStr`], returning an
+    /// [`Err`] on error.
+    ///
+    /// ```
+    /// let good_year_from_input = "1909";
+    /// let bad_year_from_input = "190blarg";
+    /// let good_year = good_year_from_input.parse().unwrap_or_default();
+    /// let bad_year = bad_year_from_input.parse().unwrap_or_default();
+    ///
+    /// assert_eq!(1909, good_year);
+    /// assert_eq!(0, bad_year);
+    /// ```
+    ///
+    /// [`parse`]: str::parse
+    /// [`FromStr`]: crate::str::FromStr
+    #[inline]
+    #[stable(feature = "result_unwrap_or_default", since = "1.16.0")]
+    pub fn unwrap_or_default(self) -> T
+    where
+        T: Default,
+    {
+        match self {
+            Ok(x) => x,
+            Err(_) => Default::default(),
+        }
+    }
+
+    /// Returns the contained [`Err`] value, consuming the `self` value.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the value is an [`Ok`], with a panic message including the
+    /// passed message, and the content of the [`Ok`].
+    ///
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```should_panic
+    /// let x: Result<u32, &str> = Ok(10);
+    /// 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
+    where
+        T: fmt::Debug,
+    {
+        match self {
+            Ok(t) => unwrap_failed(msg, &t),
+            Err(e) => e,
+        }
+    }
+
+    /// Returns the contained [`Err`] value, consuming the `self` value.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the value is an [`Ok`], with a custom panic message provided
+    /// by the [`Ok`]'s value.
+    ///
+    /// # Examples
+    ///
+    /// ```should_panic
+    /// let x: Result<u32, &str> = Ok(2);
+    /// x.unwrap_err(); // panics with `2`
+    /// ```
+    ///
+    /// ```
+    /// let x: Result<u32, &str> = Err("emergency failure");
+    /// assert_eq!(x.unwrap_err(), "emergency failure");
+    /// ```
+    #[inline]
+    #[track_caller]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn unwrap_err(self) -> E
+    where
+        T: fmt::Debug,
+    {
+        match self {
+            Ok(t) => unwrap_failed("called `Result::unwrap_err()` on an `Ok` value", &t),
+            Err(e) => e,
+        }
+    }
+
+    /// Returns the contained [`Ok`] value, but never panics.
+    ///
+    /// 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.
+    ///
+    /// [`unwrap`]: Result::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);
+    /// ```
+    #[unstable(feature = "unwrap_infallible", reason = "newly added", issue = "61695")]
+    #[inline]
+    pub fn into_ok(self) -> T
+    where
+        E: Into<!>,
+    {
+        match self {
+            Ok(x) => x,
+            Err(e) => e.into(),
+        }
+    }
+
+    /// Returns the contained [`Err`] value, but never panics.
+    ///
+    /// Unlike [`unwrap_err`], this method is known to never panic on the
+    /// result types it is implemented for. Therefore, it can be used
+    /// instead of `unwrap_err` as a maintainability safeguard that will fail
+    /// to compile if the ok type of the `Result` is later changed
+    /// to a type that can actually occur.
+    ///
+    /// [`unwrap_err`]: Result::unwrap_err
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// # #![feature(never_type)]
+    /// # #![feature(unwrap_infallible)]
+    ///
+    /// fn only_bad_news() -> Result<!, String> {
+    ///     Err("Oops, it failed".into())
+    /// }
+    ///
+    /// let error: String = only_bad_news().into_err();
+    /// println!("{}", error);
+    /// ```
+    #[unstable(feature = "unwrap_infallible", reason = "newly added", issue = "61695")]
+    #[inline]
+    pub fn into_err(self) -> E
+    where
+        T: Into<!>,
+    {
+        match self {
+            Ok(x) => x.into(),
+            Err(e) => e,
+        }
+    }
+
     ////////////////////////////////////////////////////////////////////////
     // Boolean operations on the values, eager and lazy
     /////////////////////////////////////////////////////////////////////////
@@ -1196,7 +1493,7 @@ impl<T, E> Result<T, E> {
     }
 }
 
-impl<T: Copy, E> Result<&T, E> {
+impl<T, E> Result<&T, E> {
     /// Maps a `Result<&T, E>` to a `Result<T, E>` by copying the contents of the
     /// `Ok` part.
     ///
@@ -1211,32 +1508,13 @@ impl<T: Copy, E> Result<&T, E> {
     /// assert_eq!(copied, Ok(12));
     /// ```
     #[unstable(feature = "result_copied", reason = "newly added", issue = "63168")]
-    pub fn copied(self) -> Result<T, E> {
+    pub fn copied(self) -> Result<T, E>
+    where
+        T: Copy,
+    {
         self.map(|&t| t)
     }
-}
-
-impl<T: Copy, E> Result<&mut T, E> {
-    /// Maps a `Result<&mut T, E>` to a `Result<T, E>` by copying the contents of the
-    /// `Ok` part.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(result_copied)]
-    /// let mut val = 12;
-    /// let x: Result<&mut i32, i32> = Ok(&mut val);
-    /// assert_eq!(x, Ok(&mut 12));
-    /// let copied = x.copied();
-    /// assert_eq!(copied, Ok(12));
-    /// ```
-    #[unstable(feature = "result_copied", reason = "newly added", issue = "63168")]
-    pub fn copied(self) -> Result<T, E> {
-        self.map(|&mut t| t)
-    }
-}
 
-impl<T: Clone, E> Result<&T, E> {
     /// Maps a `Result<&T, E>` to a `Result<T, E>` by cloning the contents of the
     /// `Ok` part.
     ///
@@ -1251,308 +1529,55 @@ impl<T: Clone, E> Result<&T, E> {
     /// assert_eq!(cloned, Ok(12));
     /// ```
     #[unstable(feature = "result_cloned", reason = "newly added", issue = "63168")]
-    pub fn cloned(self) -> Result<T, E> {
+    pub fn cloned(self) -> Result<T, E>
+    where
+        T: Clone,
+    {
         self.map(|t| t.clone())
     }
 }
 
-impl<T: Clone, E> Result<&mut T, E> {
-    /// Maps a `Result<&mut T, E>` to a `Result<T, E>` by cloning the contents of the
+impl<T, E> Result<&mut T, E> {
+    /// Maps a `Result<&mut T, E>` to a `Result<T, E>` by copying the contents of the
     /// `Ok` part.
     ///
     /// # Examples
     ///
     /// ```
-    /// #![feature(result_cloned)]
+    /// #![feature(result_copied)]
     /// let mut val = 12;
     /// let x: Result<&mut i32, i32> = Ok(&mut val);
     /// assert_eq!(x, Ok(&mut 12));
-    /// let cloned = x.cloned();
-    /// assert_eq!(cloned, Ok(12));
-    /// ```
-    #[unstable(feature = "result_cloned", reason = "newly added", issue = "63168")]
-    pub fn cloned(self) -> Result<T, E> {
-        self.map(|t| t.clone())
-    }
-}
-
-impl<T, E: fmt::Debug> Result<T, E> {
-    /// Returns the contained [`Ok`] value, consuming the `self` value.
-    ///
-    /// # Panics
-    ///
-    /// Panics if the value is an [`Err`], with a panic message including the
-    /// passed message, and the content of the [`Err`].
-    ///
-    ///
-    /// # Examples
-    ///
-    /// Basic usage:
-    ///
-    /// ```should_panic
-    /// let x: Result<u32, &str> = Err("emergency failure");
-    /// 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 {
-            Ok(t) => t,
-            Err(e) => unwrap_failed(msg, &e),
-        }
-    }
-
-    /// Returns the contained [`Ok`] value, consuming the `self` value.
-    ///
-    /// Because this function may panic, its use is generally discouraged.
-    /// Instead, prefer to use pattern matching and handle the [`Err`]
-    /// case explicitly, or call [`unwrap_or`], [`unwrap_or_else`], or
-    /// [`unwrap_or_default`].
-    ///
-    /// [`unwrap_or`]: Result::unwrap_or
-    /// [`unwrap_or_else`]: Result::unwrap_or_else
-    /// [`unwrap_or_default`]: Result::unwrap_or_default
-    ///
-    /// # Panics
-    ///
-    /// Panics if the value is an [`Err`], with a panic message provided by the
-    /// [`Err`]'s value.
-    ///
-    ///
-    /// # Examples
-    ///
-    /// Basic usage:
-    ///
-    /// ```
-    /// let x: Result<u32, &str> = Ok(2);
-    /// assert_eq!(x.unwrap(), 2);
-    /// ```
-    ///
-    /// ```should_panic
-    /// let x: Result<u32, &str> = Err("emergency failure");
-    /// x.unwrap(); // panics with `emergency failure`
-    /// ```
-    #[inline]
-    #[track_caller]
-    #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn unwrap(self) -> T {
-        match self {
-            Ok(t) => t,
-            Err(e) => unwrap_failed("called `Result::unwrap()` on an `Err` value", &e),
-        }
-    }
-}
-
-impl<T: fmt::Debug, E> Result<T, E> {
-    /// Returns the contained [`Err`] value, consuming the `self` value.
-    ///
-    /// # Panics
-    ///
-    /// Panics if the value is an [`Ok`], with a panic message including the
-    /// passed message, and the content of the [`Ok`].
-    ///
-    ///
-    /// # Examples
-    ///
-    /// Basic usage:
-    ///
-    /// ```should_panic
-    /// let x: Result<u32, &str> = Ok(10);
-    /// 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 {
-            Ok(t) => unwrap_failed(msg, &t),
-            Err(e) => e,
-        }
-    }
-
-    /// Returns the contained [`Err`] value, consuming the `self` value.
-    ///
-    /// # Panics
-    ///
-    /// Panics if the value is an [`Ok`], with a custom panic message provided
-    /// by the [`Ok`]'s value.
-    ///
-    /// # Examples
-    ///
-    /// ```should_panic
-    /// let x: Result<u32, &str> = Ok(2);
-    /// x.unwrap_err(); // panics with `2`
-    /// ```
-    ///
-    /// ```
-    /// let x: Result<u32, &str> = Err("emergency failure");
-    /// 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 {
-            Ok(t) => unwrap_failed("called `Result::unwrap_err()` on an `Ok` value", &t),
-            Err(e) => e,
-        }
-    }
-}
-
-impl<T: Default, E> Result<T, E> {
-    /// Returns the contained [`Ok`] value or a default
-    ///
-    /// Consumes the `self` argument then, if [`Ok`], returns the contained
-    /// value, otherwise if [`Err`], returns the default value for that
-    /// type.
-    ///
-    /// # Examples
-    ///
-    /// Converts a string to an integer, turning poorly-formed strings
-    /// into 0 (the default value for integers). [`parse`] converts
-    /// a string to any other type that implements [`FromStr`], returning an
-    /// [`Err`] on error.
-    ///
-    /// ```
-    /// let good_year_from_input = "1909";
-    /// let bad_year_from_input = "190blarg";
-    /// let good_year = good_year_from_input.parse().unwrap_or_default();
-    /// let bad_year = bad_year_from_input.parse().unwrap_or_default();
-    ///
-    /// assert_eq!(1909, good_year);
-    /// assert_eq!(0, bad_year);
-    /// ```
-    ///
-    /// [`parse`]: str::parse
-    /// [`FromStr`]: crate::str::FromStr
-    #[inline]
-    #[stable(feature = "result_unwrap_or_default", since = "1.16.0")]
-    pub fn unwrap_or_default(self) -> T {
-        match self {
-            Ok(x) => x,
-            Err(_) => Default::default(),
-        }
-    }
-}
-
-#[unstable(feature = "unwrap_infallible", reason = "newly added", issue = "61695")]
-impl<T, E: Into<!>> Result<T, E> {
-    /// Returns the contained [`Ok`] value, but never panics.
-    ///
-    /// 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.
-    ///
-    /// [`unwrap`]: Result::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 = "unwrap_infallible", reason = "newly added", issue = "61695")]
-impl<T: Into<!>, E> Result<T, E> {
-    /// Returns the contained [`Err`] value, but never panics.
-    ///
-    /// Unlike [`unwrap_err`], this method is known to never panic on the
-    /// result types it is implemented for. Therefore, it can be used
-    /// instead of `unwrap_err` as a maintainability safeguard that will fail
-    /// to compile if the ok type of the `Result` is later changed
-    /// to a type that can actually occur.
-    ///
-    /// [`unwrap_err`]: Result::unwrap_err
-    ///
-    /// # Examples
-    ///
-    /// Basic usage:
-    ///
-    /// ```
-    /// # #![feature(never_type)]
-    /// # #![feature(unwrap_infallible)]
-    ///
-    /// fn only_bad_news() -> Result<!, String> {
-    ///     Err("Oops, it failed".into())
-    /// }
-    ///
-    /// let error: String = only_bad_news().into_err();
-    /// println!("{}", error);
-    /// ```
-    #[inline]
-    pub fn into_err(self) -> E {
-        match self {
-            Ok(x) => x.into(),
-            Err(e) => e,
-        }
-    }
-}
-
-impl<T: Deref, E> Result<T, E> {
-    /// Converts from `Result<T, E>` (or `&Result<T, E>`) to `Result<&<T as Deref>::Target, &E>`.
-    ///
-    /// 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);
+    /// let copied = x.copied();
+    /// assert_eq!(copied, Ok(12));
     /// ```
-    #[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 = "result_copied", reason = "newly added", issue = "63168")]
+    pub fn copied(self) -> Result<T, E>
+    where
+        T: Copy,
+    {
+        self.map(|&mut t| t)
     }
-}
 
-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>`.
-    ///
-    /// Coerces the [`Ok`] variant of the original [`Result`] via [`DerefMut`](crate::ops::DerefMut)
-    /// and returns the new [`Result`].
+    /// Maps a `Result<&mut T, E>` to a `Result<T, E>` by cloning the contents of the
+    /// `Ok` part.
     ///
     /// # Examples
     ///
     /// ```
-    /// 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);
-    /// assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);
-    ///
-    /// let mut i = 42;
-    /// let mut x: Result<String, u32> = Err(42);
-    /// let y: Result<&mut str, &mut u32> = Err(&mut i);
-    /// assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);
+    /// #![feature(result_cloned)]
+    /// let mut val = 12;
+    /// let x: Result<&mut i32, i32> = Ok(&mut val);
+    /// assert_eq!(x, Ok(&mut 12));
+    /// let cloned = x.cloned();
+    /// assert_eq!(cloned, Ok(12));
     /// ```
-    #[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 = "result_cloned", reason = "newly added", issue = "63168")]
+    pub fn cloned(self) -> Result<T, E>
+    where
+        T: Clone,
+    {
+        self.map(|t| t.clone())
     }
 }